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Specialty Update   |    
What's New in Hip Arthroplasty
Michael H. Huo, MD1; Javad Parvizi, MD, PhD2; Nathan F. Gilbert, MD1
1 Department of Orthopedic Surgery, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-8883. E-mail address for M.H. Huo: michael.huo@utsouthwestern.edu
2 Rothman Institute, 925 Chestnut Street, Philadelphia, PA 19107
View Disclosures and Other Information
The authors did not receive grants or outside funding in support of their research for or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Specialty Update has been developed in collaboration with the Council of Musculoskeletal Specialty Societies (COMSS) of the American Academy of Orthopaedic Surgeons.

The Journal of Bone and Joint Surgery, Incorporated
J Bone Joint Surg Am, 2006 Sep 01;88(9):2100-2113. doi: 10.2106/JBJS.F.00595
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Surgeons and scientists have once again produced a large amount of data related to outcomes, biomaterials, surgical techniques, the treatment of complications, and socioeconomic issues related to total hip arthroplasty surgery. One recent debate in hip surgery is on the most efficacious treatment for displaced intracapsular hip fractures. Following the style of our previous Specialty Updates, this review is organized into seven sections: (1) primary surgery, (2) surface replacement, (3) revision surgery, (4) biomaterials and prosthetic design, (5) complications, (6) practice management, and (7) treatment of intracapsular hip fractures.

Minimal Incision Surgery

Total hip arthroplasty performed with use of smaller tissue-preserving techniques received intense initial popularity and scrutiny. There are now more data documenting differences among the various techniques. Moreover, the complication rate associated with certain techniques may be too high for patient safety.
Pagnano et al. performed staged bilateral total hip arthroplasties in twenty-six patients. One hip was treated with use of the two-incision technique, and the contralateral hip was treated with use of a mini-posterior approach. Sixteen of the twenty-six patients reported greater satisfaction on the side that had been treated with the miniposterior approach; the reasons cited included earlier recovery (50%), cosmetic appearance (25%), and a combination of reasons (25%). Eight patients preferred the side treated with the two-incision technique; all cited early recovery as the reason. Two patients had no preference. Sharkey and Hozack conducted a prospective, randomized study in which the standard approach was compared with the miniincision approach. They found no difference between the groups with regard to intraoperative blood loss, transfusions, operative time, or time to hospital discharge. Moreover, there was no difference with regard to patient outcome measurements such as the Harris hip score, the Short Form-36, and a validated rehabilitation improvement test at three to six months. The authors also evaluated the efficacy of intense rehabilitation and pain-management protocols in both groups. There was better functional improvement, a shorter hospital stay, higher patient satisfaction, and lower analgesia requirements in the group of patients who had received the intense preoperative and postoperative rehabilitation and pain-management protocol. This superior outcome was independent of incision size. These data suggest that accelerated discharge and functional return following primary total hip arthroplasty was not a function of incision size but rather was a function of many psychosocial variables.
Murphy and Tannast reported superior (p < 0.0001) recovery and functional improvement at six weeks following a superior capsulotomy mini-incision approach. However, there was no difference between the mini-incision and standard-incision groups at twelve weeks. Hildebrand et al. conducted gait analysis at three, six, and twelve weeks after total hip arthroplasty in patients who had been managed with three different minimal-incision approaches: a two-incision approach, a one-incision anterolateral approach, and a one-incision posterior approach. All patients demonstrated improvement in the Harris hip and WOMAC scores. There was a faster increase in these parameters in association with the two-incision approach at three (p < 0.01) and twelve weeks (p < 0.05). There was no difference in range of motion or abductor strength among the groups. More patients in the two-incision group were able to walk without support at three weeks as compared with those in the other two groups (p < 0.01). Moreover, the stride length, cadence, and speed were all superior in the two-incision group (p < 0.01). Another group of investigators from Japan conducted a prospective, randomized study in which gait analysis was used to assess differences in muscle recovery. The strength of selected muscle groups (abductor, extensor, and flexor) was best in association with the mini-posterior approach in contrast with the two-incision, mini-anterolateral, and standard posterior approaches. The differences were apparent at one month and persisted for as long as six months after surgery. Different minimal-incision surgical approaches may influence the temporal events of functional return following total hip arthroplasty. Patients should be properly counseled with regard to realistic expectations.
One proposed advantage of minimal-incision total hip arthroplasty is reduced cost as a result of accelerated discharge. Greidanus et al. conducted a prospective, randomized trial in which a two-incision anterior approach (sixty-six total hip arthroplasties) was compared with a one-incision anterior approach (ninety-nine total hip arthroplasties). Hospital stay and narcotic use were lower in the two-incision group (p < 0.05). However, this was offset by greater resource utilization in the operating room (time and fluoroscopy use) with the two-incision approach. Another proposed advantage of minimal-incision surgery is reduced blood loss. Vaughn et al. found no difference in acute blood loss or laboratory measures of blood levels between two groups of 100 hips that were treated with either a minimal two-incision approach or a standard one-incision approach. In fact, more patients required allogeneic blood transfusions in the two-incision group (p > 0.05). The authors also reported an average 50% (thirty-minute) increase in operative time in the two-incision group. Last, thirteen complications occurred, including ten intraoperative fractures, two dislocations, and one instance of stem loosening in the two-incision group. In contrast, only one complication occurred in the standard-incision group. There was no difference with regard to operative time, blood loss, and complications between the first fifty and second fifty total hip arthroplasties in the mini-incision group.
Bal et al.1 reported on early complications associated with the two-incision technique in a study of eighty-nine consecutive total hip arthroplasties. These results were compared with those for ninety-six total hip arthroplasties that had been performed by the same surgeon one year previously with use of a mini-lateral incision. There was no difference in operative time. Blood loss was greater in the two-incision group (p < 0.0001). The duration of hospital stay was shorter in the two-incision group (p = 0.001). Complications occurred in 42% of the patients in the two-incision group, compared with 6% of those in the mini-lateral group (p < 0.0001). Reoperations were required in 10% of the patients in the two-incision group because of fracture, loosening, dislocation, and/or wound complications. However, there was significant improvement with greater experience. When the first forty and the second forty-eight total hip arthroplasties performed with the two-incision technique were compared, there was a reduction in the rates of overall complications (p = 0.02) and revision surgery (p = 0.04). However, there was no difference between the early and late groups with regard to the prevalence of injury to the lateral femoral cutaneous nerve. The two-incision technique is a technically demanding procedure. The surgeon, although quite experienced with minimal-incision total hip arthroplasty, still experienced these complications, particularly during the early phase of the learning curve.

Fixation Without Cement

Stem

Morshed et al. conducted a meta-analysis with use of stratified and regression methods. Twenty studies were included. There was no difference between fixation with and without cement when revision of either component (p = 0.88) or both components (p = 0.30) was used as the end point. Subgroup analysis of studies not restricted to younger patients (those less than fifty-five years old) demonstrated a 3.8% (95% confidence interval, 0.7% to 6.9%) advantage in association with cement fixation. There was a trend toward superior results in younger patients who were managed with cementless fixation. Evidence-based guidelines to support any specific fixation method will require much larger and more rigorously designed studies.
Two stem designs have gained extensive clinical application over the past decade: (1) extensively coated stems with straight geometry and (2) proximally coated stems with tapered geometry. Engh et al. followed 223 total hip arthroplasties that had been performed with an extensively coated stem. The mean age at the time of surgery was fifty-five years. The latest evaluation was conducted at a mean of 18.6 years for 137 living patients (143 hips). Only three stems had been revised because of aseptic loosening, and the rate of stem survival was 97.5% at twenty years. Callaghan et al. reported the outcomes associated with a second-generation extensively coated stem in a study of seventy-nine hips that had six to eight years of follow-up. The mean age of the patients was fifty-five years. No stem was revised. With regard to fixation status, 92% of the stems were classified as bone-ingrown and 8% were classified as fibrous-stable. The prevalence of thigh pain was 6%. These data were significantly superior (p < 0.05) to those for first-generation proximally coated stems that had been inserted by the same surgeon and evaluated after a comparable follow-up interval, for which the rates of revision, loosening, and thigh pain were 3%, 5%, and 13%, respectively. Jasty et al. reported the minimum five-year results of 101 consecutive total hip arthroplasties that had been performed with use of a proximally coated (fiber-metal) tapered stem. The mean age of the patients was fifty-five years. No stem was revised. All stems were bone-ingrown, and the prevalence of thigh pain was 0%. No femoral osteolysis was observed.

Hydroxyapatite Coating

The debate on the proposed benefits of hydroxyapatite coating has continued. Lombardi et al. reported on 192 hips that had been treated with stems of identical geometry and surface texture (tapered, proximally coated) either with hydroxyapatite (sixty-one hips) or without hydroxyapatite (129 hips). The mean duration of follow-up was 11.6 years. Only one stem (a non-hydroxyapatite-coated stem) was revised. There was no difference between the groups with regard to the Harris hip score or the rate of revision. Capello et al. reported the minimum fifteen-year results of 156 total hip arthroplasties that had been performed with use of another hydroxyapatite-coated tapered stem. The mean age of the patients at the time of surgery was 51.5 years. The mean Harris hip score was 92, with 91% of the patients reporting no pain or limp at the time of the final follow-up. Revision because of loosening was necessary in only one hip. The fifteen-year stem survival rate was 99.1%, and the combined revision rate for loosening and osteolysis was 1.8%. McCarthy and Lee reported the five-year follow-up data for 114 total hip arthroplasties that had been performed with stems of identical geometry and surface texture either with hydroxyapatite coating (seventy-five hips) or without hydroxyapatite coating (thirty-nine hips). No stem was revised or was loose. There was no difference (p > 0.05) in the radiographic features of bone remodeling around either stem type. An interesting finding was the higher short-term (six-week) overall Harris hip score (82 compared with 73) and the higher pain score (42 compared with 36) in the hydroxyapatite-coated group. There was no difference between the groups with regard to the Harris hip score at two years or five years. The authors suggested a potential benefit of hydroxyapatite-coated stems in selected patients with high expectations of an early return to high-demand and high-level function following surgery.

Cup

Moore et al.2 proposed radiographic signs of osseointegration of cementless cups. Radiographic evaluation was done for 119 hips that had adequate serial radiographs after primary arthroplasty and before revision surgery. Osseointegration was confirmed with use of mechanical testing at the time of revision. The authors proposed five radiographic signs of stable cup fixation: (1) the absence of radiolucent lines, (2) the presence of a superolateral buttress, (3) medial bone stress-shielding, (4) radial trabeculae, and (5) an inferomedial buttress. Ninety-seven percent of the cups with three or more of these signs were determined to be stable at the time of revision surgery. In contrast, 83% of the cups with two or fewer signs were loose.
Callaghan et al. reported ten to eighteen-year results of 118 consecutive hip replacements that had been performed with use of a first-generation cementless cup in patients younger than fifty years old. Three cups were revised because of loosening, and four were revised because of osteolysis without loosening. In addition, fifteen revisions were performed for liner exchange. Pelvic osteolysis was observed in 15% of the hips. The mean linear wear rate was 0.2 mm/year. Fixation durability was fivefold superior to that associated with cemented cups (p < 0.01) that had been inserted by the same surgeon in a comparable patient population. Cup fixation durability has been a principal limitation in patients with previous pelvic and acetabular fractures. Lombardi et al. reported on sixty-three cementless cups that had been inserted for the treatment of posttraumatic arthritis following thirty-four acetabular, twenty-three pelvic, and six combination fractures. After a mean duration of follow-up of seven years, eight revisions had been performed because of wear and/or loosening. The ten-year rate of cup survival was 88.1% with revision as the end point. Another challenging population includes patients who have had previous pelvic irradiation. Lewallen et al. used a new cup design made of tantalum trabecular metal in this setting. The series included thirteen cups that were reviewed after a mean duration of follow-up of twenty-nine months. The mean radiation dose was 5260 cGy. The mean interval between radiation therapy and total hip arthroplasty was thirteen years. No cup was revised or loose. Surgeons from the Rothman Institute also reported durable cementless cup fixation in association with the use of a hemispherical design with supplemental screws in patients who had had previous pelvic irradiation for the treatment of prostate cancer. These results provided promise for improved cup fixation in this extremely difficult clinical setting.
Cup liners with an elevated rim were initially introduced to reduce instability. Recent data reflect the risk of impingement associated with these liners. Comfort et al. analyzed a community-based total hip arthroplasty registry that included 3070 hips. The procedures had been performed by fifty-three surgeons in five hospitals over thirteen years. The liners were grouped into three categories: (1) no elevation (17%), (2) 10° of elevation (69%), or (3) >10° of elevation (14%). One hundred and seventy liners were revised. The overall rate of liner survival at 13.3 years was 94.5%. There was a difference in the rate of survival (p = 0.02) between flat liners (98.1%) and liners with an elevation (93.7% for liners with 10° of elevation and 93.5% for those with >10° of elevation). All hips that were revised because of recurrent dislocations or shell loosening initially had an elevated liner. As a consequence of these findings, the rate of use of elevated liners in that community decreased from a high of 99% in 1996 to 50% in 2004. That report reflects the utility of a joint registry in altering clinical practice.

Fixation with Cement

The use of cement fixation has decreased considerably. Collis et al. provided additional data validating the superior durability of a polished stem surface texture when inserted with cement. Those authors reported on 1031 consecutive cemented stems with a polished texture that were inserted over ten years. There were four different stem geometries as the designs evolved over the decade. Six stems had been revised because of aseptic loosening or osteolysis after two to twelve years of follow-up. Debonding always occurred at the bone-cement interface in the failed cases. There was no difference among the four stem geometries. The revision rate for polished stems was fivefold lower than that for stems with a more roughened texture that had been inserted by the same surgeon and followed for a comparable period of time.
Surface replacement initially was introduced in the 1970s; however, its durability was poor and thus it was abandoned by most surgeons. There has been a resurgence of surface replacement over the past decade because of improvements in design, bearing surface, and instrumentation. Surface replacement has become the fastest-growing segment of all total hip arthroplasties worldwide. Ritter reported his experience with a first-generation surface replacement. Sixty-five hips were treated between 1977 and 1981. Sixty-six percent of the procedures failed at some time between three months and twenty-two years (mean, 12.3 years). Femoral failure occurred in 37% of the hips, and cup failure occurred in 29% of the hips. Among the femoral failures, 50% were due to femoral neck fracture. The author specifically commented on the eight femoral failures that occurred after a minimum of ten years. Every hip showed narrowing at the neck as a result of stress-shielding under the shell. The failure rate for these surface replacements was 5.4 times greater than the rate for total hip arthroplasties that had been performed by the same surgeon with use of stemmed designs over the same time-period. These data clearly do not reflect the improvements with the current designs, bearing surfaces, and surgical techniques. They should serve as reference against which all newer designs can be measured.
There is now more than eight years of clinical experience worldwide with contemporary metal-on-metal surface replacement. The longest and most extensive clinical experience has been with the Birmingham Surface Replacement (BSR) system. Daniel et al.3 reported that only one (0. 2%) of 446 hips that had been treated with this system had been revised after a mean duration of follow-up of 3.3 years. Nearly 90% of the entire patient group were engaged in high-demand jobs or recreational activities. Treacy et al.4 reported a 99% survival rate after a minimum duration of follow-up of five years in a study of 144 consecutive hips that were treated with the same implant system.
Femoral loosening has been a major mechanism of failure following surface replacement. Amstutz et al. reviewed the difference in outcomes between the first 300 surface replacements (Group 1) and the second 300 surface replacements (Group 2) that they performed. The mean age for the entire cohort was forty-nine years, and 74% of the patients were male. The mean duration of follow-up was seven years for Group 1 and 4.6 years for Group 2. Survival analysis demonstrated a difference (p = 0.015) between Groups 1 and 2. Overall, twenty-five hips (4.17%) were converted to a stemmed hip replacement, and two-thirds of the conversions were performed because of femoral loosening. Metaphyseal radiolucencies were apparent in 59% of the failed hips by twenty-four months and in 100% by fifty months. The authors identified the most critical technical factors for success as being meticulous femoral neck bone preparation, a dry bone bed, circumferential fixation holes, and cementing of the stem. They also recommended avoiding bone-grafting because bone-grafting would reduce the area of cement fixation to host bone. Amstutz also reported a 1% rate of femoral neck fracture in his personal experience of 800 surface replacements. He recommended (1) reaming the neck at 140°, (2) avoiding notching the lateral femoral neck cortex, and (3) abandoning surface replacement in cases in which large bone defects are present at the head-neck junction.
Vail compared surface replacement (forty-five hips) with stemmed total hip arthroplasty (123 hips). There was greater improvement in the Harris hip score among the patients managed with resurfacing (p < 0.001). Moreover, there were also differences in activity (p < 0.001), function (p < 0.001), and range of motion (p < 0.001) that favored surface replacement. There was no difference between the groups with regard to complications. Mont et al. conducted gait analysis in a study of fifteen patients who had been managed with a standard total hip arthroplasty, fifteen patients who had been managed with surface replacement, and eleven volunteers with hip osteoarthritis. All patients who had had an arthroplasty (including those managed with total hip arthroplasty and those managed with surface replacement) had a Harris hip score of >90 twelve months after surgery. Patients who had been managed with resurfacing had the best hip kinematics (abductor and extensor moments) and the best walking velocity, even when compared with the volunteers who had osteoarthritis. These data further validate the clinical efficacy of hip resurfacing in selected patients.
Fixation failure has been correlated with specific anatomical characteristics of the proximal part of the femur. Schmalzried et al.5 proposed a radiographic grading scale based on four principal characteristics: (1) bone density, (2) bone shape, (3) biomechanics, and (4) focal defects. Hips were categorized into five grades on the basis of the number of unfavorable characteristics. Lower grades were associated with a better clinical outcome. The authors concluded that proper patient selection and precise surgical technique are critical in order to avoid complications and to achieve durability after surface replacement.
Kurtz et al.6 reported a relatively constant revision burden of 17.5% for total hip arthroplasty from 1991 to 2002, with revisions accounting for approximately 20% of all total hip arthroplasty cost expenditures. The investigators constructed a model to predict the future rate of revision total hip arthroplasty. They projected 48,000 revisions in 2010, more than 67,000 in 2020, and nearly 97,000 in 2030 (a 137% increase from 2005). Similarly, they projected a greater than twofold increase in primary total hip arthroplasties (from 240,000 to 570,000) from 2005 to 2030. They also projected that the number of practicing orthopaedic surgeons in the United States would increase from approximately 20,000 in 2010 to 26,000 in 2030. On the basis of their numbers, the mean case load for each surgeon would continue to increase from decade to decade. Moreover, the increasing volume of revisions will undoubtedly pose a challenge to resource utilization and cost containment.
Many elderly patients (those who are more than eighty years old) require revision total hip arthroplasty. Parvizi et al. reviewed 170 revision total hip arthroplasties that had been done in octogenarians at a tertiary high-volume arthroplasty center over an eight-year period. There was significant improvement in function and pain relief according to the SF-36 scores after revision (p < 0.05). There was a 16.5% rate of orthopaedic complications and a 15.3% rate of major medical complications in the first six months after revision. Approximately half (48.1%) of the patients had died by a mean of 4.6 years after revision. The authors concluded that revision total hip arthroplasty is excellent for improving quality of life despite a high rate of complications in this patient population.

Stem

Iorio, Healy, and Presutti conducted a prospective, surgeon-randomized, matched-cohort study in which femoral revisions that had been performed with a cementless, modular, straight-stem femoral component with flutes were compared with those that had been performed with a cemented component. All patients had minimal (Paprosky type-I or II) bone deficiency. Each surgeon performed forty-three consecutive revisions with use of the same technique. The mean duration of follow-up was seven years. There was no difference between the groups with regard to the rates of stem rerevision (p = 0.56) or overall reoperation (p = 0.29). Although it is being used with less frequency, cement fixation may be effective in selected cases of femoral revision. One of the most common femoral revision techniques is to use distal fixation in the diaphysis with either an extensively-coated straight or curved cylindrical stem or a tapered, straight stem with flutes. The fixation stability of both stem designs is dependent on sufficient stem-canal engagement. Paprosky and Sporer reported on the use of 9 and 10-in (22.9 and 25.4-cm) fully coated cylindrical stems for revision arthroplasty in a series of patients with Paprosky type-IIIB deficiencies (characterized by no metaphyseal support and a diaphyseal segment measuring <4 cm) or type-IV deficiencies (characterized by an insufficient diaphyseal segment). The mean duration of follow-up was 4.2 years. The rate of mechanical failure was 0% for hips with type-IIIB deficiencies when the canal diameter was <19 mm, 18% for hips with type-IIIB deficiencies when the canal diameter was >19 mm, and 37.5% for hips with type-IV deficiencies. In contrast, there were no failures after revisions that had been performed with impaction grafting (ten hips) or with a tapered stem with flutes (ten hips) in the presence of similar bone deficiencies. These data reflect the limitations of extensively-coated cylindrical stems when femoral bone is deficient.
Another way to address major segmental bone deficiencies is with an allograft-prosthesis composite. Christie et al. reported the results for twelve hips after a mean of eight years of follow-up. All allografts healed to the host. Seven reconstructions had failed after a mean duration of follow-up of nine years. There was graft resorption in all hips. Most importantly, the surgeons found the allograft segment to be inadequate to support a new stem.
Some investigators have recommended revision with use of a total femoral replacement in the most extreme clinical situations. Friesecke et al.7 presented the results of 100 consecutive total femoral replacements that had been performed over 7.5 years. The mean operative time was nearly four hours. Seventy-seven percent of the procedures were performed because of the failure of a total hip arthroplasty, whereas the others were performed because of knee-related issues or periprosthetic fractures. The rate of complications (including infection, dislocation, material failure, patellar problems, and peroneal nerve palsy) was 32%. The overall functional rating for both the hip and the knee was satisfactory in most patients. However, the mean duration of follow-up was short (six years) and the durability of this salvage option remains to be documented with longer follow-up.

Cup

Berry presented a further update on eighty-nine revisions that were performed with use of a jumbo cup with multiple screws and a fiber-metal surface texture. Particulate graft was used in 61% of the procedures, and structural graft was used in 10%. The mean duration of follow-up was twelve years (minimum, ten years). Ten cups were rerevised because of loosening (five cups), infection (four), or instability (one). This technique is excellent (with a reported success rate of 93.3%), provided that there is adequate bone support and initial cup stability. Another technique that has been used to address extreme acetabular defects such as pelvic discontinuity is the use of custom-designed flanged cups. DeBoer et al. followed twenty-one consecutive revisions that had been performed with use of such a design. The mean duration of follow-up was ten years. Definite healing of the discontinuity was evident in eighteen of twenty-one hips. No cup migration was observed. No cup was revised. Despite the durable fixation and healing of the bone defects, the mean Harris hip score was <90 and 71% of the patients still required walking aids.
The tantalum trabecular metal cup was introduced into clinical use in 1997. Unger et al.8 evaluated sixty consecutive revisions that were performed with use of this type of cup, with most (92%) of the cups not having any supplemental screws. The mean duration of follow-up was just short of four years. One hip was revised because of cup loosening, 75% of the hips had no radiolucencies around the cup, and 17.5% of the hips had new nonprogressive radiolucencies around the cup. No cup migrated. Sporer and Paprosky reported on the use of a modular trabecular metal cup with multiple screws to treat major acetabular deficiencies. They inserted the cups with trabecular metal augments to supplement peripheral, and occasionally central, defects in thirty-four patients with a Paprosky type-IIIA defect (proximal and medial migration). The mean duration of follow-up was 3.1 years. All cups remained stable. One hip required revision to a constrained liner because of instability. The authors also reported on the use of a similar technique for thirteen patients with a Paprosky type-IIIB defect (pelvic discontinuity). The mean duration of follow-up was 2.6 years, and no cup was loose. Potential concerns included fretting between the shell and the augments and the failure of bone ingrowth.

Wear and Osteolysis

Osteolysis remains the principal clinical issue that can adversely affect the durability and function of any total hip arthroplasty. Engh et al. reviewed the plain radiographs and computed tomography scans of ninety-five hips after a minimum duration of follow-up of five years. Plain radiographs underestimated the total prevalence of pelvic osteolysis as compared with the findings on computed tomography scans. Most of the underestimation was in the detection of smaller lesions that were perhaps not of clinical relevance. There was a strong correlation (r2 = 0.81) between the two-dimensional size and the three-dimensional volume estimate of the lesions. Engh concluded that the clinical relevance of pelvic osteolysis can be reliably estimated on plain radiographs. This is important with regard to surveillance costs in general community practice, where sophisticated software and a high-resolution computed tomography scanner may not be readily available or affordable.
One of the most frequent revision procedures is articulation exchange with bone-grafting of osteolytic areas. Puri et al. compared the preoperative and postoperative computed tomography scans for fifteen patients who underwent such a revision. The mean size of the lesions decreased from 6.38 cm2 preoperatively to 2.94 cm2 at two years postoperatively (p < 0.0001). Graft incorporation was seen in thirteen of the fifteen cases, and no cup became loose. The authors concluded that modular liner exchange with bone-grafting is an effective technique with which to restore bone stock and to maintain cup stability.

Highly Cross-Linked Polyethylene

Highly cross-linked polyethylene has received tremendous focus since its introduction into clinical use. It has evolved into the most frequently used bearing surface for total hip arthroplasty. However, clinical wear measurements generally have not matched those reported initially from laboratory testing. McCalden et al. reported wear measurements in a prospective, randomized trial of 100 hips that were treated with either conventional or highly cross-linked polyethylene. Both groups were treated with identical implant designs and fixation techniques. There was no difference between the groups with regard to demographic characteristics or clinical outcome measures. The two-dimensional wear rates were 0.14 and 0.09 mm/year for the conventional and highly cross-linked polyethylene groups, respectively. The three-dimensional wear rates were 0.15 and 0.11 mm/year for the conventional and highly cross-linked groups, respectively. These differences represented 36% and 27% reductions for two and three-dimensional wear, respectively. Engh et al. reported intermediate-term wear measurements for more than 200 hips that were randomized to total hip arthroplasty with use of either conventional or highly cross-linked polyethylene. All femoral heads were 28 mm. The mean linear wear rates were 0.20 and 0.02 mm/year for the conventional and highly cross-linked polyethylene groups, respectively. Geller et al. reported wear measurements for seventy-five total hip arthroplasties after a minimum duration of follow-up of five years. The polyethylene liners had been made with use of an electron beam process. No osteolysis was observed in the femur or pelvis. There was no difference in the wear rate between 28-mm heads (0.01 mm/year) and 32-mm heads (0.06 mm/year). Longer follow-up will be necessary to confirm that these lower wear rates continue to correlate with a reduced prevalence of osteolysis and implant fixation failure.
Retrieval analysis of failed and well-functioning implants has demonstrated a high frequency of neck-liner impingement. Impingement can cause wear and even fracture of the liner rim. Usrey et al. reported that sixty-eight (60%) of 113 retrieved liners showed evidence of impingement at the rim, with moderate to severe damage being seen in association with 32% of the liners. They specifically examined the liners for backside wear, which was evident in association with 31% of the liners. Backside wear was evident in 61% (twenty-two) of the thirty-six liners that showed impingement. In contrast, backside wear was evident in only 16% (twelve) of the seventy-three liners that showed no impingement. This difference was significant (p < 0.0001). There was also a significant difference between the groups with regard to the wear rate (0.33 mm/year for liners with impingement, compared with 0.19 mm/year for those without impingement; p = 0.03). Currier et al. reported fatigue fractures of highly cross-linked polyethylene liners secondary to oxidation. They analyzed seven retrieved liners made of highly cross-linked gamma-irradiated polyethylene that was annealed below melting temperature. Six liners were found to have reduced mechanical properties due to oxidation. In fact, five showed fatigue damage (cracking and delamination) at the liner rim. These changes were evident after only two years of in situ use. Researchers from the same institution reported rim fractures in three of eleven retrieved liners made of another highly cross-linked polyethylene. In this group, there was no excessive oxidation of the material itself in the areas of rim fracture. The damage always occurred in the thinnest portion of the liner and in cups that had been placed in a more vertical position (that is, in greater abduction). These findings suggest that highly cross-linked polyethylene liners are subject to failure mechanisms that are not dissimilar to those of conventional polyethylene. Kurtz et al.9 analyzed the mechanical properties of twelve retrieved cup liners that were made of highly cross-linked gamma-irradiated polyethylene. All liners had an identical design with regard to shell geometry and locking mechanism. All liners were revised for reasons other than wear. The mean time in situ was 1.9 years. Maximum oxidation occurred near the unloaded bearing surface at a mean depth of 0.9 mm. The ultimate strength properties in unworn areas were within 10% of the initial ultimate strength of never-implanted liners. Strength properties were lower in unworn areas than in worn areas (p = 0.01). There was no correlation between the duration of implantation and the strength properties of either the worn or unworn surfaces. There were variations within each liner as a function of sampling. Additional retrieval studies will be needed to fully determine the material properties after long-term clinical use.
No correlation has been made between wear reduction and clinical osteolysis. One variable is the host's biological response to the wear debris generated from highly cross-linked polyethylene. Minoda et al. analyzed wear particles of highly cross-linked polyethylene that were retrieved from the pseudoapsule at the time of revision surgery. They found fewer particles (5.33 × 107 particles/g) than the previously proposed critical particle load for osteolysis (1 × 1010 particles/g). The particle geometry was generally smaller (0.66 µm) and rounder (1.44 × 1.37 µm) than that of particles of conventional polyethylene that were analyzed in the same laboratory. However, the particle dimensions were larger than what had been documented from in vitro testing. These data reflect the particle characteristics from one particular material but do suggest that in vivo wear of this material is different from in vitro wear testing.
Quantitative assessments of patient activity have been found to correlate with wear following total hip arthroplasty. The single greatest limitation of activity assessment with use of pedometers and other methods is patient compliance. Silva et al.10 compared the use of a four-day assessment protocol with that of a longer assessment protocol lasting seven days or more. The mean activity was 5464 steps/day during the four-day collection period, compared with 5737 steps/day during the longer collection period (a 5.0% difference). Patients were categorized into several activity levels on the basis of the pedometer reading. There was high agreement among the activity categories between the two data collection methods. This is an important finding as the use of a shorter collection period will ensure greater patient compliance. This form of activity assessment does not account for seasonal variations, nor does it allow for distinction of types of activities.

Ceramic Bearings

Intermediate-term clinical data are now available for two series of total hip arthroplasties performed with use of ceramic-on-ceramic bearings. Capello et al., in a study of 257 hips with a minimum duration of follow-up of five years, reported no fracture or failure of the ceramic bearing surfaces. The rate of femoral osteolysis was 0.6%, in contrast with the rate of 22.1% in a comparable series of hips with metal-polyethylene bearings and identical cup and stem designs. There was no difference between the two groups with regard to the Harris hip score. Murphy reported on 141 hips after a mean duration of follow-up of four years. There was no fracture or bearing failure and no femoral or pelvic osteolysis. Toni et al. performed 3746 total hip arthroplasties with use of a ceramic-on-ceramic bearing between 1990 and 2004. They reported four head fractures and ten liner rim chips. No head fractures occurred in hips that had been treated with a head that was 32 mm or larger. The survival rate for this ceramic articulation was 98.2% at fifteen years.
There have been reports of squeaking in hips with a ceramic-on-ceramic bearing. O'Toole et al. conducted a detailed review of 2397 total hip arthroplasties that had been performed with ceramic-on-ceramic bearings. Seventeen patients (0.7%) reported squeaking. The mean time to the onset of the squeaking was fourteen months. Compared with patients without squeaking, those who reported squeaking were younger (mean age, fifty-six years), heavier (mean weight, 90 kg), and taller (mean height, 180 cm). Eight patients had squeaking only when the hip was in flexion (such as when picking up something from the floor); these patients did not associate squeaking with walking, whereas the other patients did. Computed tomography scans were made to assess component position. There was no significant difference between the groups with regard to cup abduction or anteversion. Toni et al. reported on the fluid analysis of aspirates from squeaking ceramic-on-ceramic hips. The presence of ceramic particles established the diagnosis of articulation damage leading to squeaking and to revision surgery. The authors recommend using computed tomography scans to assess component position as suboptimal position could result in impingement, creating ceramic chips or even a bearing fracture.

Metal-on-Metal Bearings

Controversies remain with regard to the safety of metal-on-metal bearing surfaces, particularly with regard to metal ion release and the potential for hypersensitivity reactions. Jacobs et al. reported additional data in their ongoing prospective longitudinal study examining the serum and urine metal ion levels in patients with such a bearing surface. The cohort included twenty-two patients with surface replacements and fifteen patients with total hip replacements. All components and bearing surfaces were made by the same manufacturer. Serum and urine samples were collected at specific time intervals after surgery for as long as thirty-six months. The ion levels were greater in both groups after surgery compared with preoperative levels, and, at four months after surgery, the serum chromium and cobalt levels were greater in the surface replacement group than in the total hip arthroplasty group. The authors concluded that the larger head sizes (range, 46 to 52 mm) used for surface replacement did not result in greater metal ion concentrations when compared with the head size used for total hip arthroplasty (32 mm). Rasquinha et al. reported on steady-state serum metal ion levels in patients with four different bearing surfaces after a minimum duration of follow-up of five years. Forty total hip arthroplasties were randomized into four groups: (1) cemented metal-polyethylene, (2) cementless metal-polyethylene, (3) cementless ceramic-polyethylene, and (4) cementless metal-metal. There were no differences among the four groups with regard to clinical and radiographic outcomes. The highest cobalt and chromium levels were found in the metal-metal group. These data suggest lower corrosion and release of metal ions at the head-neck taper junction in association with ceramic heads as compared with metal (cobalt-chromium) heads.
One of the proposed advantages of hard-on-hard bearings is a reduction in osteolysis. Park et al.11, in a study of 169 total hip arthroplasties that had been performed with a contemporary metal-on-metal bearing, reported ten cases of osteolysis (prevalence, 5.9%) after two years of follow-up. The patients with early osteolysis had a significantly higher prevalence of hypersensitivity to cobalt than control patients did (p = 0.03). Two patients underwent reoperation, and periarticular tissue was retrieved. Histologic examination showed a perivascular infiltrate of lymphocytes. Immunophenotyping demonstrated CD3-positive T cells and CD68-positive macrophages, and immunohistochemical analysis demonstrated the presence of bone-resorbing cytokines. These findings suggest that delayed hypersensitivity may be the cause of early osteolysis in some patients following metal-on-metal total hip arthroplasty.
The increasing use of metal-on-metal bearings in younger patients has raised the concern of potential adverse effects, particularly on child-bearing females. McMinn et al. collected whole blood from the mother and umbilical cord after five deliveries. Four of the five patients had a unilateral metal-on-metal surface replacement, and the other patient had a bilateral surface replacement. The levels of chromium and cobalt recorded in the cord blood were an average of 50% lower than those recorded in the maternal blood. There also was an excellent correlation between cord and maternal blood with regard to the levels of trace elements. It is thus possible to follow maternal blood ion levels during pregnancy as a monitor of fetal safety. These data clearly underscore the importance of continued surveillance in patients with metal-on-metal bearings.
Retrieval analysis of a well-functioning metal-on-metal total hip replacement has been reported in the past. Clarke et al.12 reported the results of retrieval analysis of a McKee-Farrar total hip replacement after thirty years. They specifically looked for surface roundness and roughness. The deviation from perfect roundness for the head and cup was 15.6 µm and 15.1 µm, respectively. Surface roughness was 0.015 µm for the head and 0.012 µm for the cup. Histologic examination did not demonstrate any histiocytes or plasma cells. Cobalt and chromium were not identified in the tissues. No systemic trace-element analysis was done prior to the patient's death.

Infection

Multiple laboratory tests and imaging modalities are currently used to diagnose periprosthetic infection. Deirmengian et al. analyzed gene expression patterns in white blood cells isolated from joints with implants. They found distinctively different patterns of gene expression between infected and noninfected cases. They also reported different patterns between joints with infection and those with inflammatory arthritis (gout). The differences were highly significant (p < 0.001). The most important finding was that abnormal gene expression was not found in cells isolated from noninfected joints. It is hoped that with further refinement, synovial fluid analysis for gene expression may provide increased sensitivity and specificity in comparison with the tests that are currently available. Parvizi et al. reported on fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging as a noninvasive diagnostic modality for periprosthetic infection. They evaluated eighty-three patients who underwent revision surgery. Infection was correctly diagnosed with FDG-PET in twenty-one of twenty-three cases (specificity, 91.3%). Infection was correctly excluded in sixty-two of sixty-three cases (specificity, 98.4%). The positive and negative predictive values of this imaging technique were 95.5% and 96.9%, respectively. These values were far superior to those for indium-111 white blood-cell scintigraphy.
Cahill et al. compared the quality of life for thirty-four patients who had an infection with that for sixty-two patients who did not have an infection. They used a variety of outcome measurement instruments, including the WOMAC, SF-36, and Assessment of Quality of Life (AQoL) instruments. Functional outcome and health-related quality of life parameters were significantly poorer in those who had an infection (p < 0.05). The treatment of infection is a burden to both hospitals and surgeons. Bozic and Ries analyzed resource utilization at a tertiary teaching hospital. They collected data on twenty-five consecutive revision total hip arthroplasties for two-stage reimplantation, twenty-five revisions for reasons other than infection, and twenty-five primary total hip arthroplasties over an eighteen-month period. Revision for the treatment of infection was associated with a longer operative time, more blood loss, a higher rate of complications, and a longer hospital stay. Moreover, revision for the treatment of infection resulted in higher costs for the inpatient stay and higher outpatient charges during the twelve months following the revision procedure. The referral rate for infection at the site of total hip arthroplasty had increased significantly at that center over the previous five years, while there had been no change in the referral rate for revisions for reasons other than infection during the same period. This trend could reflect the technical and financial disincentives for hospitals and surgeons to provide treatment for patients with infection at the site of a total hip arthroplasty.
The most effective treatment protocol for an infection at the site of a total hip arthroplasty is a two-stage revision. Surgeons from the Mayo Clinic reviewed the results of 169 consecutive total hip arthroplasties that had been performed with use of a two-stage protocol over a period of ten years (from 1988 to 1998). Cement fixation was used in 72% of the procedures. The mean duration of follow-up was six years. The rate of rerevision was 15% overall, with rates of 9.5% for reinfection, 5% for aseptic loosening, and 0.5% for periprosthetic fracture. Reinfection was correlated neither with the initial pathogen nor with the type of fixation.
One of the most difficult clinical situations is having unexpected positive intraoperative cultures following revision total hip arthroplasty. There is no consensus with regard to the best method for the treatment of this problem. Berend et al. reported seven positive cultures after 103 revisions in which the preoperative workup had been negative for infection. They chose to treat each patient with intravenous antibiotics for six weeks without additional surgery. None of the patients had development of a clinical infection or fixation failure.

Dislocation

Dislocation remains one of the most frequent reasons for early total hip revision. Hoeffel et al. reviewed the data on seventy-six revisions for recurrent dislocation that had been collected in a community-based registry of 3210 total hip arthroplasties from 1991 to 2003. The mean time from the index total hip arthroplasty to revision was 1.1 years. The techniques that were used included liner/head exchange (50%), shell revision (42%), stem/shell revision (5%), and insertion of a constrained liner (3%). Redislocation occurred in 16% of the hips, with half of those requiring another revision. The lowest redislocation rate was associated with complete shell revision (4.5%), and the worst rate was associated with liner/head exchange (10.5%). The rate of survival of the revised hips was 97.1% at twelve years. One newer option for the treatment of recurrent dislocation is the use of a large-diameter femoral head. This improves the head-neck ratio and increases the offset and the range of motion. Paprosky and Sporer reported the clinical results for forty-seven hips that had undergone revision for the treatment of recurrent dislocation. Seventeen hips had received a 36-mm head, eight had received a 40-mm head, and twenty-two had received a larger tripolar component with a >40-mm articulation. The mean duration of follow-up was three years. Two redislocations occurred; both were successfully treated by changing the shell position.

Periprosthetic Femoral Fracture

Periprosthetic femoral fractures are complex and difficult to treat. Their incidence will continue to increase as more patients are living longer with higher activity levels. In addition, the increased incidence of revision surgery could also contribute to a higher rate of periprosthetic fractures. Lindahl et al.13 reported on 1049 fractures, recorded in the Swedish Hip Registry, that had occurred between 1979 and 2000. The overall incidence was 0.4% for primary total hip arthroplasty and 2.1% for revision total hip arthroplasty. The mean time from the procedure to the fracture was 7.4 years for primary total hip arthroplasty and 3.9 years for revision total hip arthroplasty. The ten-year rate of implant survival was 69.9% following the treatment of a periprosthetic fracture, compared with 90.5% for hips without a periprosthetic fracture.
Broaching of the femur is a critically important step in terms of sizing, stability, and fixation durability of the stem. Intraoperative fracture of the proximal part of the femur is the most frequent complication associated with minimal-incision techniques. There is definitely a risk when there is a geometric mismatch between the broach and the femur as occurs in association with the use of tapered and wedge-shaped implant designs. Markel et al. evaluated the impaction forces on the broaches and the stem implant with use of instruments with strain gauges. They operated on seventeen patients using a flat, tapered, wedge-shaped design. The mean number of impactions for canal preparation and insertion of the stem was 111. A wide range of impaction forces was recorded, with the highest approaching 9000 lb. An important finding was that the maximum force used for the last broach was nearly twofold greater than the force used to insert the stem. Therefore, there is greater risk of a calcar fracture in association with the use of the final broach than there is in association with the insertion of the stem itself. Data such as these may be of use for future instrument design and surgical training. Berend et al. reviewed the results of 3089 total hip arthroplasties that had been performed with cement (2295 hips) or without cement (794 hips) at a single center over fourteen years. Calcar fractures occurred in 2.7% of the hips. The fracture rate was higher for cementless stems (6.9%) than for cemented stems (0.8%). Regression analysis identified the anterolateral approach and female gender as risk factors. A fracture did not have an adverse effect on fixation durability for cementless stems but led to inferior results for cemented stems (rate of survival of stem fixation, 97.1% compared with 93.3%) after a mean seven years of follow-up.
At the present time, there is no agreement with regard to the most effective treatment method for periprosthetic fracture. This is in part due to the many different patterns of fractures and the need to consider implant fixation stability. Contemporary fracture fixation methods have focused on tissue-preserving techniques. Ricci et al.14 reported the results of treatment of fifty consecutive Vancouver type-B1 fractures (fractures around a stable implant) with use of indirect reduction and a single lateral plate inserted with tissue-preserving techniques. No bone graft was used. After a mean duration of follow-up of twenty-four months, all fractures had healed. There was one deep infection, and 73% of the patients returned to their prefracture level of functional capacity.

Nerve Palsy

Nerve palsy is a rare but devastating complication of total hip arthroplasty. Farrell et al.15 reviewed the results of 27,004 total hip arthroplasties that had been performed at one institution over thirty years. Forty-seven patients with postoperative motor nerve palsy were identified (prevalence, 0.17%). There were twenty-nine complete palsies (including sixteen peroneal, eleven sciatic, and two femoral palsies) and eighteen incomplete palsies (including fourteen peroneal, three sciatic, and one femoral palsy). Risk factors included hip dysplasia, posttraumatic arthritis, the posterior approach, and lengthening of >1.1 cm. Thirty-six percent of the patients with a complete palsy recovered fully at a mean of twenty-one months. Seventy percent of the patients with an incomplete palsy recovered fully. Fortunately, only five patients required medication for the treatment of neurogenic pain. These data are useful for preoperative patient counseling, particularly for patients with dysplasia and posttraumatic arthritis.

Epidemiology

More evidence has become available in support of earlier surgical intervention for patients in need of total joint arthroplasty. Lavernia et al. prospectively followed sixty-three total hip arthroplasties and sixty-nine total knee arthroplasties for three consecutive years. Comprehensive evaluation was performed with use of the WOMAC, the SF-36, and the Quality of Well-Being (QWB) scale. The patients were divided into two categories: (1) severe functional impairment ("waited too long") and (2) mild impairment. Significant improvement was seen in both groups after surgery (p < 0.05); however, all outcome measures were inferior in patients with severe impairment even after three years.
Disparity of care among different patient groups is an area of focus in public health policy. Lau et al. reported significant (p < 0.05) differences in the rates of total hip arthroplasty among racial groups in the United States. The mean rates (per 100,000 individuals) were 72.2 for whites, 32.7 for blacks, 16.8 for Hispanics, 13.5 for Asians, and 8.7 for Native Americans. This disparity could be related to access to care, cultural barriers, and/or socioeconomic issues. Regardless of the reasons, the elderly Hispanic and Asian populations are projected to grow by sixfold to sevenfold in the next five decades, compared with a projected twofold increase among elderly non-Hispanic whites. As the elderly minority population expands in the United States, the unique challenges facing the delivery of health care to these population segments must be addressed.

Safety of Hip Arthroplasty

In recent years, several authors have correlated surgical volume with clinical outcome. Doro analyzed the results of total hip arthroplasty from the Nationwide Inpatient Sample between 1988 and 2000. These data were based on a random sample of 20% of all patient admissions in the United States. Hospitals were categorized into either the highest quartile (more than 146 primary and more than forty-six revision arthroplasties per year) or the lowest quartile (fewer than forty primary and fewer than ten revision arthroplasties per year). In-hospital mortality was the principal outcome measured. There was a significant difference between high-volume and low-volume hospitals with regard to the rate of mortality following primary arthroplasty (0.16% compared with 0.29%; p < 0.01). There also was a significant difference in mortality following revision surgery as compared with primary surgery (0.48% compared with 1.2%; p < 0.01). The difference was especially profound in older patients, with the data showing a 7.5-fold greater mortality for patients more than seventy-five years of age undergoing primary surgery in low-volume hospitals.
There has been increased interest in reducing hospital stay for a variety of reasons. Parvizi et al. prospectively evaluated the medical complications in a study of 2411 patients undergoing 2631 hip and knee arthroplasties and found that 32.4% of the patients had at least one complication. Twenty-one percent of these were considered to be major complications, including death. Only 22% of the major complications occurred on the day of the operation, whereas 66% had become apparent by three days. The authors concluded that early discharge protocols may only be safe for selected patients.

Pain Management

Multimodal perioperative pain management has been implemented to facilitate accelerated rehabilitation. Peters et al. evaluated the efficacy of a protocol involving the use of preoperative and postoperative oral narcotics and COX-2 inhibitors, spinal anesthesia, and either femoral nerve block (for patients managed with total knee arthroplasty) or local anesthetic infiltration (for patients managed with total hip arthroplasty). Two cohorts of fifty consecutive hip and knee arthroplasties were evaluated before and after institution of the protocol. There was a significant (p < 0.005) decrease in narcotic use and length of hospital stay and an increase in distance walked during therapy for patients managed with the protocol. Shore et al. performed a prospective, randomized study to evaluate the efficacy of periarticular injection with use of a combination of ropivacaine, ketorolac, epimorphine, and epinephrine in 128 patients undergoing total knee and total hip arthroplasty. They found significant (p < 0.01) reductions in intravenous narcotic use and in visual analog pain scores in patients who received the injections. Parvataneni et al. also reported reduction of narcotic use and physical therapy services following the institution of a local injection protocol. More importantly, 90% of the patients reached functional and activity milestones earlier than those who did not receive injections and 74% described their recovery as "easy" on a standardized questionnaire. Newer pain-management protocols coupled with tissue-preserving surgical techniques may provide accelerated functional return, at least in selected patients.

Inpatient Rehabilitation

There have been some recent policy changes with regard to inpatient rehabilitation following total joint arthroplasty. Costs associated with inpatient rehabilitation have not been widely studied. Lavernia et al. conducted a cost analysis of 136 consecutive patients following primary total hip or knee arthroplasty. The mean cost (and standard deviation) was $10,751 ± $598 for the rehabilitation unit stay and $2393 ± $92 for home-care services. This difference was significant (p < 0.001). The authors projected that the annual rehabilitation costs for total joint arthroplasty in the United States would exceed $3.4 billion. Vincent et al. examined functional improvement and costs for inpatient rehabilitation following 331 primary and revision total hip arthroplasties. Patients managed with primary total hip arthroplasty had a shorter length of stay than patients managed with revision total hip arthroplasty, and the degree of improvement in functional independence was inferior following revision total hip arthroplasty. The total hospital cost was also higher in the revision group. The worst outcome and highest costs were found for patients who underwent revision total hip arthroplasty for the treatment of infection.

Total Hip Arthroplasty in Specific Patient Populations

Obese Patients

There have been several reports in the high-profile lay press on the perceived reluctance of surgeons to operate on obese patients. Turgeon et al. reviewed resource utilization in a study of 1343 patients who underwent total hip arthroplasty in two community hospitals. Obesity was stratified according to body mass index, with the highest category being a body mass index of >35. The most obese patients were 2.3 times more likely to have a hospital stay in excess of five days and 2.6 times more likely to require inpatient rehabilitation. There was no difference among the groups with regard to operative times or blood transfusions. An important finding was that patients with a body mass index of >25 (all obese categories) had lower Harris hip scores at one year than did nonobese patients. Dalury evaluated forty-six patients (fifty-seven total hip arthroplasties) with a body mass index of >35 after a mean of 5.8 years. The mean Harris hip score improved from 36 to 84. The most common complication was wound drainage (eight hips). There were no deep infections, dislocations, leg-length inequalities, or venous thromboemboli. No cup was revised. One stem was revised because of loosening, and another was loose according to radiographic criteria. A technical challenge was that 17% of the cups were placed with a high abduction angle, probably because of exposure limitations. These data will facilitate the formulation of practice guidelines and modifications in surgical techniques to minimize complications in the obese patient population.

Young Patients

Lombardi et al. reported on 247 hip arthroplasties that were performed with use of a tapered titanium-alloy stem design with a plasma-sprayed porous surface in patients who were less than forty years old. The mean age at the time of surgery was 34.8 years, and the mean body mass index was 29 kg/m2. The mean duration of follow-up was 5.8 years, with 125 hips having a minimum of five years of follow-up and fifty-one hips having a minimum of ten years of follow-up. Three stems were revised because of loosening (two) or thigh pain (one). The rate of stem survival was estimated to be 98.8% for up to eighteen years. Archibeck et al. reported on 100 consecutive total hip arthroplasties that were performed with use of a proximally-coated straight stem in patients who were less than fifty years old. The mean duration of follow-up was nine years. The result was rated as good or excellent in 84% of the hips. No stem was revised for loosening. There were twelve revisions, including six for wear or osteolysis, five for dislocation, and one for infection. The rate of stem survival at ten years was 98%.
Controversy has existed with regard to the best surgical method with which to treat a displaced femoral neck fracture. Several recent reports have presented data in support of total hip arthroplasty for the treatment of such fractures in the elderly. Keating et al.16 conducted a prospective, randomized trial to evaluate the differences in efficacy, complications, and cost among three treatment options for the treatment of displaced femoral neck fractures in the elderly. The investigators randomized 207 patients to internal fixation, hemiarthroplasty, or primary total hip arthroplasty. The rate of reoperation was 36% for the internal fixation group, compared with 5% for the hemiarthroplasty group and 9% for the total hip arthroplasty group. The internal fixation group also had inferior hip and functional scores. Patients who had been managed with total hip arthroplasty had slightly better hip and functional scores at twenty-four months than did those who had been managed with hemiarthroplasty. The overall cost over two years was higher for the internal fixation group, principally because of a higher rate of reoperation. There was no difference between the hemiarthroplasty and total hip arthroplasty groups with regard to cost. Hoffman et al. reviewed data from thirteen prospective, randomized trials comparing internal fixation and arthroplasty for the treatment of displaced femoral neck fractures. They compared quality-adjusted life-years (QALYs) and cost. The best functional outcome was attained with total hip arthroplasty (4.5 QALYs), followed by hemiarthroplasty (3.6 QALYs) and internal fixation (2.6 QALYs). Cost-effectiveness analysis showed that hemiarthroplasty had the lowest cost per procedure ($22,208), followed by total hip arthroplasty ($23,551) and internal fixation ($29,733). The incremental cost-effectiveness of total hip arthroplasty over hemiarthroplasty was $2400/QALY. Blomfeldt et al.17 performed a prospective, randomized trial of 102 consecutive patients in which internal fixation was compared with total hip arthroplasty for the treatment of displaced femoral neck fractures. Patients were followed for four years. The reoperation rate was 4% for the total hip arthroplasty group and 47% for the internal fixation group. Hip function was better and the decline in health-related quality of life parameters was less in the total hip arthroplasty group at four, twelve, and twenty-four months. The difference was not significant by forty-eight months.
The editorial staff of The Journal reviewed a large number of recently published research studies related to the musculoskeletal system that received a Level of Evidence grade of I. Over 100 medical journals were reviewed to identify these articles, which all have high-quality study design. In addition to articles cited already in this Update, six level-I articles were identified that were relevant to total hip arthroplasty. A list of those titles is appended to this review after the standard bibliography. We have provided a brief commentary about each of the articles to help guide your further reading, in an evidence-based fashion, in this subspecialty area.
Bhandari M, Bajammal S, Guyatt GH, Griffith L, Busse JW, Schunemann H, Einhorn TA. Effect of bisphosphonates on periprosthetic bone mineral density after total joint arthroplasty. A meta-analysis. J Bone Joint Surg Am. 2005;87:293-301.
Six studies (296 patients) were analyzed to determine whether bisphosphonates have an effect on periprosthetic bone loss in the hip and knee. All studies were randomized, controlled trials in which dual-energy x-ray absorptiometry scans were used to measure periprosthetic bone mineral density after total joint arthroplasty. Significantly less periprosthetic bone loss had occurred in patients managed with bisphosphonates than in control patients at three, six, and twelve months (p < 0.01). Bone loss was prevented more effectively around cemented than around cementless implants. A larger effect was also seen following total knee arthroplasty than following total hip arthroplasty. These studies focused on the results of the dualenergy x-ray absorptiometry scans alone and not on clinical data such as patient outcomes, side effects, the periprosthetic fracture rate, or the rate of revision. Additional analysis is necessary before general recommendations can be made.
Mundy GM, Birtwistle SJ, Power RA. The effect of iron supplementation on the level of haemoglobin after lower limb arthroplasty. J Bone Joint Surg Br. 2005;87:213-7.
One hundred and twenty patients were randomized to treatment with ferrous sulfate tablets or placebo for three weeks following primary total hip or knee arthroplasty. Ninety-nine patients completed the study. The dose of ferrous sulfate was 200 mg three times per day. There was no difference in demographic characteristics or preoperative laboratory values between the groups. The hemoglobin levels were measured preoperatively, on Days 1 and 5 after surgery, and during Weeks 3 and 6. Patients with preexisting anemia (as indicated by a hemoglobin level of <13 for men and of <11.5 for women) were excluded. The hemoglobin levels dropped by an average of 30% immediately after surgery and recovered to an average of 85% at three weeks after surgery, independent of iron therapy. No significant difference was seen between the two groups in terms of hemoglobin levels after surgery. However, there was a slight trend toward increased hemoglobin levels at six weeks in the iron-supplementation group. Ten percent of the patients were noncompliant because of gastrointestinal side effects. On the basis of these results, the routine administration of iron supplementation following total joint arthroplasty does not appear to provide any added benefit with regard to recovery of the hemoglobin level.
Chimento GF, Pavone V, Sharrock N, Kahn B, Cahill J, Sculco TP. Minimally invasive total hip arthroplasty: a prospective randomized study. J Arthroplasty. 2005;20:139-44.
Sixty patients were randomized to receive either a minimally invasive total hip arthroplasty (twenty-eight patients) or a standard-incision total hip arthroplasty (thirty-two patients). The surgical approach was decided by drawing a card immediately preoperatively to determine whether an 8-cm or 15-cm incision was to be used. A posterolateral approach was used, with repair of the short external rotators at time of closure. Patients with a body mass index of >30 and those who had had previous hip surgery were excluded. There was no significant difference between the patients in terms of age, weight, body mass index, or hip score. The minimally invasive surgery group had significantly less blood loss intraoperatively (p = 0.003) and less total blood loss (p = 0.009) when adding drain output. There was no difference between the groups in terms of operative time, transfusion requirements, pain medication usage, or serum levels of interleukin-6. Most of the arthroplasties were performed with hybrid fixation. There was no difference in cement grading. The rate of limp at six weeks was higher in the standard-incision group than in the minimally invasive surgery group (46.8% compared with 21.4%). Other rehabilitation milestones were similar. There was no significant difference between the groups with regard to the rate of complications, but there were two dislocations in the minimally invasive surgery group as compared with none in the standard-incision group. The only clinically relevant advantages of single-incision posterior minimally invasive total hip arthroplasty were a reduction in blood loss and a lower rate of limp at six weeks. Longer-term follow-up is necessary to determine if minimally invasive total hip arthroplasty is superior in terms of daily function and the durability of fixation.
Lai KA, Shen WJ, Yang CY, Shao CJ, Hsu JT, Lin RM. The use of alendronate to prevent early collapse of the femoral head in patients with nontraumatic osteonecrosis. A randomized clinical study. J Bone Joint Surg Am. 2005;87:2155-9.
Forty patients with Steinberg grade-II or III osteonecrosis of the femoral head were randomized to receive 70 mg of alendronate orally once weekly for twenty-five weeks. The control group did not receive any medication. The patients were followed for a minimum of two years with use of the Harris hip score, serial radiographs, and magnetic resonance imaging scans. Only two of twenty-nine femoral heads in the treatment group collapsed, whereas nineteen of twenty-five in the control group collapsed (p < 0.001). In addition, one hip in the treatment group went on to total hip arthroplasty, compared with sixteen hips in the control group. Many risk factors are associated with osteonecrosis. This particular protocol may be effective only for selected subgroups of patients. Larger patient populations and longer follow-up periods are necessary in order to fully assess the clinical effectiveness of using alendronate to prevent collapse and progression to total hip arthroplasty.
Kalisvaart KJ, de Jonghe JF, Bogaards MJ, Vreeswijk R, Egberts TC, Burger BJ, Eikelenboom P, van Gool WA. Haloperidol prophylaxis for elderly hip-surgery patients at risk for delirium: a randomized placebo-controlled study. JAm Geriatr Soc. 2005;53:1658-66.
This randomized, double-blind, placebo-controlled trial was an attempt to define the role of routine administration of haloperidol to high-risk geriatric patients to prevent delirium following hip surgery. The study included 430 patients who were seventy years old or more and were at risk for postoperative delirium. Haloperidol (1.5 mg per day, divided into three doses) was given at the time of admission and was continued for seventy-two hours after surgery. The investigators recorded the prevalence of delirium as well as its severity and duration. The duration of hospital stay was also determined. Delirium was reported in 15.8% of the patients, and the prophylactic administration of haloperidol had no effect on its prevalence. However, it did significantly decrease the severity and duration of the dementia (5.4 compared with 11.8 days; p < 0.01). In addition, the mean length of the hospital stay was reduced by more than five days. The medication had no side effects. This appears to be a safe and cost-effective treatment for this particular patient population.
Tak E, Staats P, Van Hespen A, Hopman-Rock M. The effects of an exercise program for older adults with osteoarthritis of the hip. J Rheumatol. 2005;32:1106-13.
The investigators randomized 109 patients who had osteoarthritis of the hip to an eight-week exercise program and compared them with controls who followed no formal exercise program. All of the patients were at least fifty-five years old and lived independently. Outcome was measured according to pain, the Harris hip score, a quality of life assessment, body mass index, and disability. Patients were followed prospectively for three months. The exercise program, consisting of observed strength-training, home exercises, and dietary advice, was effective for decreasing pain and improving hip function. It did not affect the quality of life or the body mass index. However, there was insufficient follow-up to determine if these changes would continue. Exercise and lifestyle alterations can reduce pain and improve functional status in the short term. This is especially important for medical delivery systems in which there is a long waiting time for total hip arthroplasty.
Bal BS, Haltom D, Aleto T, Barrett M. Early complications of primary total hip replacement performed with a two-incision minimally invasive technique. J Bone Joint Surg Am. 2005;87: 2432-8.872432  2005  [PubMed][CrossRef]
 
Moore MS, McAuley JP, Young AM, Engh CA Sr. Radiographic signs of osseointegration in porous-coated acetabular components. Clin Orthop Relat Res. 2006;444: 176-83.444176  2006  [PubMed][CrossRef]
 
Daniel J, Pynsent PB, McMinn DJ. Metal-on-metal resurfacing of the hip in patients under the age of 55 years with osteoarthritis. J Bone Joint Surg Br. 2004;86: 177-84.86177  2004  [PubMed][CrossRef]
 
Treacy RB, McBryde CW, Pynsent PB. Birmingham hip resurfacing arthroplasty. A minimum follow-up of five years. J Bone Joint Surg Br. 2005;87: 167-70.87167  2005  [PubMed][CrossRef]
 
Schmalzried TP, Silva M, de la Rosa MA, Choi ES, Fowble VA. Optimizing patient selection and outcomes with total hip resurfacing. Clin Orthop Relat Res. 2005;441: 200-4.441200  2005  [PubMed][CrossRef]
 
Kurtz S, Mowat F, Ong K, Chan N, Lau E, Halpern M. Prevalence of primary and revision total hip and knee arthroplasty in the United States from 1990 through 2002. J Bone Joint Surg Am. 2005;87: 1487-97.871487  2005  [CrossRef]
 
Friesecke C, Plutat J, Block A. Revision arthroplasty with use of a total femur prosthesis. J Bone Joint Surg Am. 2005;87: 2693-701.872693  2005  [CrossRef]
 
Unger AS, Lewis RJ, Gruen T. Evaluation of a porous tantalum uncemented acetabular cup in revision total hip arthroplasty: clinical and radiological results of 60 hips. J Arthroplasty. 2005;20: 1002-9.201002  2005  [CrossRef]
 
Kurtz SM, Hozack W, Turner J, Purtill J, MacDonald D, Sharkey P, Parvizi J, Manley M, Rothman R. Mechanical properties of retrieved highly cross-linked crossfire liners after short-term implantation. J Arthroplasty. 2005;20: 840-9.20840  2005  [PubMed][CrossRef]
 
Silva M, McClung CD, Dela Rosa MA, Dorey FJ, Schmalzried TP. Activity sampling in the assessment of patients with total joint arthroplasty. J Arthroplasty. 2005;20: 487-91.20487  2005  [PubMed][CrossRef]
 
Park YS, Moon YW, Lim SJ, Yang JM, Ahn G, Choi YL. Early osteolysis following second-generation metal-on-metal hip replacement. J Bone Joint Surg Am. 2005;87: 1515-21.871515  2005  [PubMed][CrossRef]
 
Clarke MT, Darrah C, Stewart T, Ingham E, Fisher J, Nolan JF. Long-term clinical, radiological and histopathological follow-up of a well-fixed McKee-Farrar metal-on-metal total hip arthroplasty. J Arthroplasty. 2005;20: 542-6.20542  2005  [PubMed][CrossRef]
 
Lindahl H, Malchau H, Herberts P, Garellick G. Periprosthetic femoral fractures classification and demographics of 1049 periprosthetic femoral fractures from the Swedish National Hip Arthroplasty Register. J Arthroplasty. 2005;20: 857-65.20857  2005  [PubMed][CrossRef]
 
Ricci WM, Bolhofner BR, Loftus T, Cox C, Mitchell S, Borelli J Jr. Indirect reduction and plate fixation, without grafting, for periprosthetic femoral shaft fractures about a stable intramedullary implant. J Bone Joint Surg Am. 2005;87: 2240-5.872240  2005  [PubMed][CrossRef]
 
Farrell CM, Springer BD, Haidukewych GJ, Morrey BF. Motor nerve palsy following primary total hip arthroplasty. J Bone Joint Surg Am. 2005;87: 2619-25.872619  2005  [PubMed][CrossRef]
 
Keating JF, Grant A, Masson M, Scott NW, Forbes JF. Randomized comparison of reduction and fixation, bipolar hemiarthroplasty, and total hip arthroplasty. Treatment of displaced intracapsular hip fractures in healthy older patients. J Bone Joint Surg Am. 2006;88: 249-60.88249  2006  [CrossRef]
 
Blomfeldt R, Tornkvist H, Ponzer S, Soderqvist A, Tidermark J. Comparison of internal fixation with total hip replacement for displaced femoral neck fractures. Randomized, controlled trial performed at four years. J Bone Joint Surg Am. 2005;87: 1680-8.871680  2005  [PubMed][CrossRef]
 

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References

Bal BS, Haltom D, Aleto T, Barrett M. Early complications of primary total hip replacement performed with a two-incision minimally invasive technique. J Bone Joint Surg Am. 2005;87: 2432-8.872432  2005  [PubMed][CrossRef]
 
Moore MS, McAuley JP, Young AM, Engh CA Sr. Radiographic signs of osseointegration in porous-coated acetabular components. Clin Orthop Relat Res. 2006;444: 176-83.444176  2006  [PubMed][CrossRef]
 
Daniel J, Pynsent PB, McMinn DJ. Metal-on-metal resurfacing of the hip in patients under the age of 55 years with osteoarthritis. J Bone Joint Surg Br. 2004;86: 177-84.86177  2004  [PubMed][CrossRef]
 
Treacy RB, McBryde CW, Pynsent PB. Birmingham hip resurfacing arthroplasty. A minimum follow-up of five years. J Bone Joint Surg Br. 2005;87: 167-70.87167  2005  [PubMed][CrossRef]
 
Schmalzried TP, Silva M, de la Rosa MA, Choi ES, Fowble VA. Optimizing patient selection and outcomes with total hip resurfacing. Clin Orthop Relat Res. 2005;441: 200-4.441200  2005  [PubMed][CrossRef]
 
Kurtz S, Mowat F, Ong K, Chan N, Lau E, Halpern M. Prevalence of primary and revision total hip and knee arthroplasty in the United States from 1990 through 2002. J Bone Joint Surg Am. 2005;87: 1487-97.871487  2005  [CrossRef]
 
Friesecke C, Plutat J, Block A. Revision arthroplasty with use of a total femur prosthesis. J Bone Joint Surg Am. 2005;87: 2693-701.872693  2005  [CrossRef]
 
Unger AS, Lewis RJ, Gruen T. Evaluation of a porous tantalum uncemented acetabular cup in revision total hip arthroplasty: clinical and radiological results of 60 hips. J Arthroplasty. 2005;20: 1002-9.201002  2005  [CrossRef]
 
Kurtz SM, Hozack W, Turner J, Purtill J, MacDonald D, Sharkey P, Parvizi J, Manley M, Rothman R. Mechanical properties of retrieved highly cross-linked crossfire liners after short-term implantation. J Arthroplasty. 2005;20: 840-9.20840  2005  [PubMed][CrossRef]
 
Silva M, McClung CD, Dela Rosa MA, Dorey FJ, Schmalzried TP. Activity sampling in the assessment of patients with total joint arthroplasty. J Arthroplasty. 2005;20: 487-91.20487  2005  [PubMed][CrossRef]
 
Park YS, Moon YW, Lim SJ, Yang JM, Ahn G, Choi YL. Early osteolysis following second-generation metal-on-metal hip replacement. J Bone Joint Surg Am. 2005;87: 1515-21.871515  2005  [PubMed][CrossRef]
 
Clarke MT, Darrah C, Stewart T, Ingham E, Fisher J, Nolan JF. Long-term clinical, radiological and histopathological follow-up of a well-fixed McKee-Farrar metal-on-metal total hip arthroplasty. J Arthroplasty. 2005;20: 542-6.20542  2005  [PubMed][CrossRef]
 
Lindahl H, Malchau H, Herberts P, Garellick G. Periprosthetic femoral fractures classification and demographics of 1049 periprosthetic femoral fractures from the Swedish National Hip Arthroplasty Register. J Arthroplasty. 2005;20: 857-65.20857  2005  [PubMed][CrossRef]
 
Ricci WM, Bolhofner BR, Loftus T, Cox C, Mitchell S, Borelli J Jr. Indirect reduction and plate fixation, without grafting, for periprosthetic femoral shaft fractures about a stable intramedullary implant. J Bone Joint Surg Am. 2005;87: 2240-5.872240  2005  [PubMed][CrossRef]
 
Farrell CM, Springer BD, Haidukewych GJ, Morrey BF. Motor nerve palsy following primary total hip arthroplasty. J Bone Joint Surg Am. 2005;87: 2619-25.872619  2005  [PubMed][CrossRef]
 
Keating JF, Grant A, Masson M, Scott NW, Forbes JF. Randomized comparison of reduction and fixation, bipolar hemiarthroplasty, and total hip arthroplasty. Treatment of displaced intracapsular hip fractures in healthy older patients. J Bone Joint Surg Am. 2006;88: 249-60.88249  2006  [CrossRef]
 
Blomfeldt R, Tornkvist H, Ponzer S, Soderqvist A, Tidermark J. Comparison of internal fixation with total hip replacement for displaced femoral neck fractures. Randomized, controlled trial performed at four years. J Bone Joint Surg Am. 2005;87: 1680-8.871680  2005  [PubMed][CrossRef]
 
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These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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Quarterly CME | October 05, 2006
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Paul E. Beaule, M.D., FRCSC
Posted on September 06, 2006
Patient Selection and Hip Resurfacing
University of Ottawa, Ottawa, CANADA

To The Editor:

I read with interest the review, "What’s new in hip arthroplasty", by Huo and associates(1). Realizing the importance and difficulty in preparing this type of article for the Journal, it is equally important that the information presented be accurate. Unfortunately, the section on surface replacement is somewhat misleading, particularly regarding patient selection. After correctly stating that the weak link in hip resurfacing is femoral fixation, the authors refer to a paper by Schmalzried and associates(2) to guide surgeons in optimizing femoral fixation through proper patient selection. Unfortunately, the results of that paper (2) report no such relationship between patient anatomy and femoral fixation or for that matter clinical outcome.

Although the radiographic characteristics cited can certainly influence the level of difficulty in performing hip resurfacing, their level of significance is still unclear. Similarly, while the authors cite works from Amstutz, Vail and Mont, there are no references provided making it again difficult to independently assess the information presented.

The author(s) of this letter to the editor received payment or other benefits or a commitment or agreement to provide such benefits from a commercial entity. A commercial entity paid or directed, or agreed to pay or direct, benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author(s) is affiliated or associated.

References:

1. Huo MH, Parvizi J, Gill GS. What's new in hip arthroplasty. J Bone Joint Surg 2006;88(9):2100-13.

2. Schmalzried T, Silva M, de la Rosa MA, Choi E-S, Fowble VA. Optimizing patient selection and outcomes with total hip resurfacing. Clin Orthop 2005;441:200-4.

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