Extract
The purpose of this review is to report and summarize the research published on selected topics in adult knee reconstruction during the year 2009. The keywords "knee" and "arthroplasty" and "prospective" and "randomized" were used to create a search in the National Library of Medicine's PubMed database, limited to manuscripts published in The Journal of Bone and Joint Surgery (American Volume) or The Journal of Arthroplasty in 2009. The resulting seventeen studies are included in this review of adult reconstruction of the knee as well as in the complete bibliography at the end of the report. In addition, other studies from 2009 were chosen for their specific relevance to the topics discussed.
The purpose of this review is to report and summarize the research published on selected topics in adult knee reconstruction during the year 2009. The keywords "knee" and "arthroplasty" and "prospective" and "randomized" were used to create a search in the National Library of Medicine's PubMed database, limited to manuscripts published in The Journal of Bone and Joint Surgery (American Volume) or The Journal of Arthroplasty in 2009. The resulting seventeen studies are included in this review of adult reconstruction of the knee as well as in the complete bibliography at the end of the report. In addition, other studies from 2009 were chosen for their specific relevance to the topics discussed.
Over the past several years, there has been a clear nationwide push to decrease costs while simultaneously reducing complications. Among the strategies used to accomplish these goals are the implementation of national guidelines and the development of performance measurements. Implicit in such endeavors is the knowledge and understanding of true best practice, outcomes, complications, and cost-effectiveness. Studies focusing on the epidemiology and economics of knee arthroplasty are critical to the development and implementation of national guidelines and measures.
Kurtz et al.1 searched for temporal changes in primary and revision total knee arthroplasty caseloads for surgeons from 1990 to 2004. The Nationwide Inpatient Sample revealed dramatic increases in the number of primary and revision total knee arthroplasties being performed by individual surgeons over the study period. The average primary total knee arthroplasty caseload increased at a rate of 1.7 cases per surgeon per decade, whereas the average revision total knee arthroplasty caseload increased at a rate of 1.4 cases per surgeon per decade. Analysis of the caseloads of the top 5% of total knee arthroplasty surgeons by volume revealed that the average caseload increased from thirty-three to eighty-six cases per year. Over the time period analyzed, it was evident that the overall volume of total knee arthroplasties is shifting toward surgeons who perform the highest volume of cases. The increasing demand for primary and revision total knee arthroplasty certainly will have serious economic and logistical consequences on the future of orthopaedic health care, particularly in tertiary centers where high volume of primary and revision total knee arthroplasties is performed. Ong et al.2 used Medicare claims data from 1997 to 2004 to study the duration of total joint arthroplasty procedures nationwide. For total knee arthroplasty, the average duration of surgery declined from 160 minutes in 1997 to 138 minutes in 2004. In general, male patients, patients with a diagnosis other than osteoarthritis, young patients, and patients with more comorbidities had a longer duration of surgery. The authors also found that while hospital and surgeon volume were inversely proportionate to the duration of total knee arthroplasty, the larger hospitals (those with >500 beds) were associated with longer procedures. This is an important study because it provides a reference point for studies analyzing the relationship between complications and surgical time. Furthermore, considering recent national efforts to cut costs and to encourage efficiency, these data provide an accurate baseline for comparison.
Memtsoudis et al.3 used the National Hospital Discharge Survey to analyze changes in the demographics, comorbidities, complications, and mortality in a study of 3,830,420 patients who were managed during three five-year periods from 1990 to 2004. As expected, they found an increased utilization of primary total knee arthroplasty, with the number of procedures doubling from 313 total knee arthroplasties per 100,000 individuals during the period from 1990 to 1994, to 634 total knee arthroplasties per 100,000 individuals during the period from 2000 to 2004. Over the three study periods, the demographic characteristics demonstrated an increasing proportion of younger patients as well as an increasing number of comorbidities among patients. Despite an increase in the rate of comorbidities, the authors found that the procedure-related complication rate decreased from 12% to 7% from the first time period to the third time period. Although the mortality rate declined from 0.50% during the period from 1990 to 1994 to 0.21% during the period from 1995 to 1999, mortality increased slightly to 0.28% during the period from 2000 to 2004. Despite progressive increases in the use of thromboprophylaxis during these time periods, the authors did not find a concomitant decline in mortality or pulmonary embolism during the most recent time period. In fact, the rate of pulmonary embolism increased from 0.29% in the period from 1995 to 1999 to 0.52% in the period from 2000 to 2004. Although an increase in patient comorbidities could explain recent trends toward increasing rates of pulmonary embolism and overall mortality, it is nevertheless surprising to note that the mandates directed at the use of potent thromboprophylaxis have not led to a decline in the rate of pulmonary embolism and mortality. Additional large population studies are necessary to understand the true relationship between the use of potent chemoprophylaxis and morbidity and mortality after total knee arthroplasty.
The controversy regarding optimal thromboprophylaxis after total knee arthroplasty continues to focus on the risk-to-benefit ratio of various anticoagulants. Considering the variable efficacy and risks of bleeding, infection, and wound complications associated with anticoagulation after total knee arthroplasty, the American Academy of Orthopaedic Surgeons (AAOS) has offered clinical practice guidelines on the prevention of symptomatic pulmonary embolism4. The practice guidelines emphasize the following points: (1) arthroplasty surgery is different now than it was fifteen years ago and older studies should not be used to create guidelines, (2) the available literature since 1996 shows no significant differences in the rate of symptomatic pulmonary embolism with the use of low-molecular-weight heparin, warfarin, or mechanical devices and aspirin alone, (3) the body of literature is underpowered and fails to provide considerable evidence because of the rarity of symptomatic or fatal pulmonary embolism after arthroplasty, and (4) the risk of major bleeding should be a consideration when selecting the method of thromboprophylaxis after arthroplasty.
Brown5 conducted a pooled analysis of randomized controlled trials focusing on venous thromboembolism after major orthopaedic surgery. He included all randomized controlled trials that were cited by the American College of Chest Physicians (ACCP) guidelines and also added two trials that were excluded by the ACCP because they did not provide venographic data. Pooled data analysis was utilized in the review, and the rates of symptomatic deep-vein thrombosis, symptomatic pulmonary embolism, fatal pulmonary embolism, major operative-site bleeding, and major non-operative-site bleeding were specifically calculated. The author found, on the basis of the pooled data, that aspirin is effective for decreasing the number of venous thromboembolism events after major orthopaedic surgery. This conclusion resulted from the Pulmonary Embolism Prevention trial that was excluded from the ACCP analysis because of the lack of venographic data. The author also found that while warfarin, low-molecular-weight heparins, and pentasaccharides increase the risk of operative-site bleeding events across pooled data, there was no reduction in symptomatic deep-vein thrombosis, pulmonary embolism, or fatal pulmonary embolism.
The author also identified the methodological flaws that undermine the ACCP guidelines: (1) the exclusion of any randomized studies that did not utilize venographic outcome assessments, (2) the failure to require relevant clinical outcomes such as symptomatic deep-vein thrombosis, pulmonary embolism, fatal pulmonary embolism, and major bleeding complications for inclusion in their analysis, (3) the failure to quantitatively analyze the incidence of these relevant clinical outcomes from randomized trials, and (4) potential conflicts of interest with pharmaceutical companies for six of seven members of the drafting committee. Furthermore, the ACCP guidelines adhere to strict inclusion criteria requiring outcomes assessment with venography or duplex ultrasound. This criterion is based on their claim that asymptomatic deep-vein thromboses lead to post-thrombotic syndrome and cause morbidity after major orthopaedic surgery. However, without any Level-1 prognostic outcome studies demonstrating post-thrombotic syndrome after asymptomatic deep-vein thrombosis following arthroplasty or hip fracture surgery, the ACCP guidelines are reduced to expert opinion.
In a continuing effort to decrease variability in surgical technique, investigators have further defined the merits and drawbacks of navigation. The two main technologies currently available to "guide" the surgical decision-making during a total knee arthroplasty are computer navigation and case-specific cutting jigs. Both technologies aim to eradicate the natural variation in surgeon technique. One of the main recent areas of focus has been demonstration of the importance of the mechanical axis as a predictor of function and longevity after total knee arthroplasty.
Two studies demonstrated advantages in terms of functional outcome and implant survival following total knee arthroplasties with a neutral mechanical axis. Fang et al.6, in a report on 6070 knees, showed that outliers in terms of overall mechanical alignment were associated with a significantly higher failure rate. The authors observed an average failure rate of 0.84% at a mean of 6.6 years after total knee arthroplasty. Knees that were implanted in 3° to 7° of coronal anatomic alignment had the lowest failure rate (0.5%), whereas knees outside of this range had a risk of failure that was more than three times greater. This study was larger than previous studies with conflicting conclusions. Choong et al.7 performed a randomized prospective study comparing computer-assisted surgery (sixty knees) with conventional surgery (fifty-five knees). They demonstrated a functional advantage when implants that were implanted within 3° of a neutral mechanical axis were compared with outliers. Furthermore, computer-assisted total knee arthroplasty was associated with a higher number of knees within 3° of neutral mechanical alignment (88% versus 61%). Longstaff et al.8 also demonstrated that the functional outcome after total knee arthroplasty was significantly better for patients who had neutral mechanical alignment.
Kim et al.9 prospectively compared computer navigation with conventional total knee arthroplasty in a bilateral total knee arthroplasty study model involving 160 patients (320 knees). After a mean of 3.4 years follow-up, the authors found no differences in terms of knee scores or function. They also found no differences in terms of implant alignment between techniques with use of radiographs and computed tomography. However, the total knee arthroplasties that were performed with computer navigation required an average of almost twenty minutes of additional surgical time. Weng et al.10 also prospectively compared computer navigation with conventional total knee arthroplasty with use of a bilateral knee study model involving sixty patients (120 knees). The authors found that computer navigation was associated with a much higher rate of knees within 3° of a neutral mechanical axis (87% versus 50%) but also increased the surgical duration by an average of about twenty minutes. In a third such study, Seon et al.11 prospectively compared function and implant alignment in a study involving thirty-one knees that were treated with navigation-assisted unicondylar knee arthroplasty and thirty-three knees that were treated with conventional unicondylar arthroplasty. After a minimum duration of follow-up of two years, there were no significant differences between the groups in terms of knee scores or function; however, there were significantly more outliers in alignment (>3° from neutral) in the conventional unicondylar arthroplasty group. The authors also reported two stress fractures due to the creation of pin tracks in the navigation group. While most studies have demonstrated that navigation successfully reduces the number of outliers of implant alignment, navigation requires more operative time, and additional study will be necessary to determine whether the improvement in implant alignment impacts long-term function or survival to offset the increased surgical time and the potential for fracture.
Smaller incisions, muscle-preserving approaches, and rapid recovery protocols have been a prominent trend in total knee arthroplasty for nearly a decade. Outcomes and benefits remain mixed.
Karpman and Smith12 performed a randomized prospective study of total knee arthroplasties performed through a medial parapatellar approach (n = 19), a mini-midvastus approach (n = 20), or a quadriceps-sparing approach (n = 20). The same surgeon performed all procedures, and identical perioperative protocols were used for all patients. Although the quadriceps-sparing approach was associated with improvements in terms of pain, function, and satisfaction, these improvements were not consistent or persistent. The quadriceps-sparing approach was associated with an additional fifteen minutes of operative time on average and was the approach used for the only two postoperative infections in the study. Lin et al.13 also conducted a prospective randomized study comparing the quadriceps-sparing approach with the mini-incision medial parapatellar approach. Sixty patients (eighty total knee arthroplasties) were included in the study, and the authors could find no significant differences in terms of postoperative pain, peak muscle torque, or functional outcomes. The quadriceps-sparing approach was associated with the only alignment outliers (four implants) and had a surgical duration that was about twenty minutes longer than that for the medial parapatellar approach. Given the increased surgical time, the potential for malalignment and wound complications, and the limited early benefit, the quadriceps-sparing approach is not a recommended technique for many surgeons.
Other authors have also studied the early outcome after specific approaches to total knee arthroplasty. Dalury et al.14 specifically addressed the effect of anterior tibial translation and patellar eversion on early recovery after total knee arthroplasty. In a prospective randomized study involving forty patients, the authors tested the hypothesis that avoidance of tibial dislocation and patellar eversion leads to improved recovery. Patients were followed with regard to Knee Society scores and testing for pain, strength, and motion. The authors found no clinical differences between the study groups at six weeks and concluded that patellar eversion and tibial translation have no adverse effect on patients having a total knee arthroplasty.
Niki et al.15 analyzed the serum levels of several biomarkers for tissue damage to compare various surgical approaches for total knee arthroplasty. A consecutive series of 147 patients was studied; the procedures included several minimally invasive approaches and standard approaches to total knee arthroplasty. Serum levels of creatinine phosphokinase, myoglobin, aldolase, lactate dehydrogenase, glutamic-oxaloacetic transaminase, and creatinine were tested in all patients preoperatively and at five intervals up to two weeks postoperatively. The minimally invasive approaches were not associated with lower biomarker levels. In addition to concerns about the limited benefit of minimally invasive surgery, there is concern that use of the minimally invasive approaches could lead to increased early failure after total knee arthroplasty, especially when new adopters are not trained. Barrack et al.16 conducted a very interesting study in which they analyzed their experience with 237 first-time revision total knee arthroplasties over a three-year period. Although only 18% of these revisions were performed following a minimally invasive index arthroplasty, the average time to revision in this group of patients was only fifteen months. This represented a very rapid time to failure in comparison with the authors’ overall experience with revision after standard total knee arthroplasty (average time to revision, eighty months). Although there have been many reports from experienced centers demonstrating the safety of minimally invasive techniques, it is not clear that the results are equal among all surgeons.
The authors of two recent studies warned about the complications that may arise in association with the use of a minimally invasive approach to unicompartmental knee replacement. Hamilton et al.17 focused on complications and two-year survival in a retrospective study of 445 consecutive minimally invasive fixed-bearing unicondylar knee replacements. The authors identified an overall revision rate of 5.8% at an average of 3.25 years after surgery. The most common reasons for revision and reoperation were retained cement (4.5%), aseptic loosening (2.2%), and tibial plateau fracture or collapse (0.9%). Interestingly, the authors found that the complications could not be totally attributed to a learning curve as the revision and reoperation rates did not decrease significantly through the study period. The authors emphasized the importance of appropriate visualization and attention to excess cement removal before closure. However, it was not clear from the study whether the minimally invasive technique was responsible for the complications. Song et al.18 also reported on their early experience with unicompartmental knee arthroplasty with use of a mobile-bearing implant. They reviewed their first 100 cases of medial unicompartmental knee arthroplasty after a minimum of two years of follow-up. Complications necessitating reoperation included two medial plateau fractures, four meniscal bearing dislocations, and one case of femoral loosening. Similar to the paper by Hamilton et al., the authors emphasized the careful attention that is required to perform a successful unicompartmental knee replacement. Again, it is not clear whether the complications were related to minimally invasive surgery. Unicompartmental knee replacement is certainly less traumatic and likely results in better function than total knee replacement. However, the surgery requires meticulous technique in order to avoid complications, regardless of whether an extensile or a minimally invasive approach is used.
Over the last decade, perioperative protocols have emerged to reduce postoperative pain and to improve early function; these protocols have included preemptive pain management, the intraoperative administration of medications, periarticular injections, and postoperative avoidance of parenteral narcotics.
Krenzel et al.19 conducted a prospective randomized study to evaluate the efficacy of posterior capsular injections of a local anesthetic during sixty-six total knee arthroplasties. During surgery, 20 mL of either ropivacaine or saline solution was injected into the posterior capsule in all four quadrants. Additionally, all patients received a femoral nerve catheter with ropivacaine, a spinal block with ropivacaine, and patient-controlled intravenous fentanyl after surgery. Outcomes were evaluated with use of functional tests, pain scales, and the assessment of narcotic usage at frequent intervals after surgery. The authors found that patients receiving the posterior capsular injection were more likely to perform a straight leg raise at eight and ten hours after surgery and were less likely to rate the pain as severe at twelve hours after surgery. After twelve hours, there was no apparent difference between the study group and the control group. Christensen et al.20 also conducted a prospective randomized study focusing on periarticular injection during total knee arthroplasty. However, those authors compared a periarticular injection with and without the presence of methylprednisolone. Seventy-six patients were randomized to either the study or control group. All patients received preemptive pain medication, general anesthesia, and a femoral nerve block, and all were permitted to resume walking in the early postoperative period. The authors found no differences in terms of pain or function after surgery; however, the patients who received the methylprednisolone injection were discharged from the hospital an average of one day sooner. The only complications in the study occurred in patients who received the periarticular steroid injection; specifically, one patient had a deep infection, and two patients required manipulation. The rate of complications was not significantly different between the groups; however, if periarticular corticosteroid injection does increase the risk of deep infection, the study likely did not have enough power to reveal significance.
One concern regarding the use of periarticular injections is the potential for local anesthetic toxicity in association with the simultaneous use of a reinfusion drain after total knee arthroplasty. Parker et al.21 actually measured plasma ropivacaine concentrations in twenty patients who had reinfusion from a drain after having received periarticular ropivacaine during total knee arthroplasty. Although the periarticular injection had 150 mg of ropivacaine, patients who were reinfused with an average of only 1.9 mg of ropivacaine and plasma concentrations reached peaks of only 1.5 µg/mL. Interestingly, the reinfused quantity of ropivacaine was quite trivial compared with the ropivacaine plasma levels resulting from the periarticular injection itself. It is important to note that the periarticular injection is administered into the tissue, not into the joint space. Periarticular injections, as part of a pain-management protocol, are used commonly. They are easy to administer, are generally safe, and appear to have a benefit in the early postoperative period.
A few groups of investigators have also conducted excellent studies on nerve blocks during the perioperative period. Hunt et al.21 randomized patients to receive either a sham injection (n = 24), a femoral nerve block (n = 33), or femoral and sciatic nerve blocks (n = 31) before total knee arthroplasty. Postoperative pain management included patient-controlled intravenous morphine in addition to oral medications, and patients were assessed with pain scales at four-hour intervals. The groups receiving nerve blocks had significantly lower pain scores through the morning of the second postoperative day when compared with the sham injection group. On the day of surgery, patients receiving the femoral and sciatic nerve blocks had less pain than those receiving a femoral block only; however, there was no significant difference after the day of surgery. Opioid use was also significantly less for the groups receiving the nerve blocks, with the combined sciatic and femoral nerve block group having the least opioid usage through the afternoon of the first postoperative day. Shum et al.23 studied the use of continuous femoral nerve blocks for analgesia after total knee arthroplasty. Sixty patients undergoing a unilateral total knee arthroplasty were randomized to receive a high-dose continuous femoral nerve block (0.15% ropivacaine), a low-dose femoral nerve block (0.2% ropivacaine), or no femoral nerve block. All patients also received patient-controlled intravenous morphine after surgery. Both nerve block groups received continuous ropivacaine administered at a rate of 10 mL/hr for the first twenty-four hours and 5 mL/hr for the next twenty-four hours. The authors assessed pain scores and opioid use for seventy-two hours after total knee arthroplasty and also evaluated clinical scores and range of motion two years after surgery. Patients who had a continuous nerve block had significantly less postoperative pain for six hours after surgery; however, there was no effect beyond this time period. Additionally, patients with a continuous block had lower cumulative morphine usage for seventy-two hours after surgery. There were no differences between the high and low-dose ropivacaine groups. Furthermore, there were no differences between any of the groups in terms of clinical scores at two years. On the basis of these two studies addressing the use of nerve blocks after total knee arthroplasty, it appears that there is an early postoperative benefit that decreases pain and opioid use for up to twenty-four hours after surgery. However, there do not appear to be clinically relevant differences beyond this time period.
Another perioperative decision involves the use of blood-salvage techniques and the timing of tourniquet release during total knee arthroplasty. Steffin et al.24 conducted a prospective randomized study comparing tourniquet release before or after wound closure and studied the effects on hematocrit drop, drainage output, and operative time. Thirty-seven patients were randomized by means of a coin flip and were followed through the perioperative period. The authors found no difference between the groups in terms of any of the parameters studied.
The quality of outcomes studies on arthroplasty has improved dramatically in the recent literature, with an increasing number of prospective randomized studies coming to fruition. However, given the limited number of prospective randomized studies performed to date, we must also consider retrospective data in our assessment of the arthroplasty outcomes literature.
High-Flexion versus Standard Knee Designs
Kim et al.25 conducted a prospective randomized study involving a bilateral total knee arthroplasty model in which a high-flexion design was compared with a standard cruciate-retaining design. Ten men and 240 women had a bilateral total knee arthroplasty in which one knee was treated with a high-flexion implant and the contralateral knee was treated with a standard-flexion design. Patients were assessed at various intervals with use of questionnaires, rating systems, and clinical and radiographic examinations. After a minimum duration of follow-up of two years, the authors found no significant clinical differences between the groups, revealing that the high-flexion design did not have any advantage over the standard-flexion design. Kim et al.26 also performed a prospective randomized study in which fifty-four patients received a high-flexion prosthesis in one knee and a standard cruciate-retaining prosthesis in the contralateral knee. Again, the authors found no differences between the groups in terms of knee scores, function, or range of motion at three years. Minoda et al.27 prospectively randomized 171 patients undergoing 181 cruciate-retaining total knee arthroplasties to receive standard implants or implants with a high-flexion femoral component and a polyethylene insert. The patients were followed for one year and were assessed on the basis of range of motion, knee scores, and clinical and radiographic outcomes. There were no significant differences between groups, although the authors identified a higher average range of motion in the high-flexion group. Seon et al.28 conducted a study in which fifty knees were randomized to total knee arthroplasty with a high-flexion design and fifty were randomized to total knee arthroplasty with a standard design. The high-flexion design was a cruciate-retaining implant with a high-flexion femoral component and high-flexion polyethylene insert similar to that used in the study by Minoda et al.27. The authors prospectively followed the patients for a minimum of two years in terms of range of motion, function, and knee ratings. They found no significant differences between the groups, suggesting that the high-flexion implants alone did not provide improvement in terms of clinical outcome after total knee arthroplasty. McCalden et al.29 also compared a high-flexion design with a standard-flexion design in a prospective randomized study of 100 patients. Fifty patients received a high-flexion posterior-stabilized polyethylene insert, and fifty received a standard posterior stabilized polyethylene insert. After an average duration of follow-up of 2.7 years, the authors found no differences in range of motion between the implant designs, again suggesting that the implant alone is not associated with clinically important improvement in postoperative flexion. It appears that high-flexion implant designs do not provide a significant improvement of range of motion after total knee arthroplasty. We await longer-term clinical results to determine if there are differences in implant survival due to differences in contact stress between high-flexion and standard total knee arthroplasty designs.
Mobile-Bearing versus Fixed-Bearing Knee Designs
Mobile-bearing total knee arthroplasty designs are purported to provide several advantages over fixed-bearing design. Proponents of mobile-bearing designs have suggested that rotation of the tibial platform may facilitate optimal patellar tracking and range of motion. Furthermore, some believe that rotating-platform technologies will reduce wear and the overall polyethylene burden that leads to osteolysis and implant loosening. Two recent prospective randomized studies specifically tested the early benefits of mobile bearings in total knee arthroplasty.
Gioe et al.30 performed a randomized, patient-blinded study of 312 total knee arthroplasties (273 patients) that were performed with either a rotating-platform tibial implant or an all-polyethylene implant. The patients were followed for a minimum of two years and were assessed with regard to several outcome measures, knee scores, and radiographic findings. Although both the study group and the control group had significant improvements postoperatively, the authors could not find any significant differences between the groups. They concluded that, at least in the early to intermediate term, the rotating-platform technology did not appear to provide patients with a clinical improvement. Harrington et al.31 conducted a similar prospective, randomized study of 140 total knee arthroplasties that were performed with either a rotating-platform or a fixed-bearing implant. The authors monitored the Knee Society score, several outcome measures, and range of motion at multiple time periods until the two-year follow-up. They only found a significant result at the six-week and one-year intervals, when the rotating-platform group demonstrated superior range of motion (a clinical difference of approximately 5°). At two years, the authors found no clinical differences between the groups and concluded that there is no early functional benefit associated with mobile-bearing designs. Oh et al.32 performed a meta-analysis of the literature comparing the outcomes of fixed-bearing and mobile-bearing total knee arthroplasty. They identified ten trials involving a total of 906 total knee arthroplasties that met the criteria for inclusion in their study. The authors found no significant differences between the implant designs in terms of American Knee Society knee scores, Knee Society function and pain scores, range of motion, radiolucent lines, complications, or patient preference. The authors concluded that mobile-bearing prostheses do not provide a functional or radiographic advantage over fixed-bearing designs. It appears that there are no significant functional benefits associated with mobile-bearing implants, and long-term studies concerning survival are anticipated. Engh et al.33 examined the surfaces of twenty-three retrieved low-contact-stress mobile-bearing inserts and thirty-one retrieved fixed-bearing inserts for evidence of top and backside wear with use of the Hood grading system. After more than five years in situ, there was no significant difference between the mobile-bearing and fixed-bearing implants with regard to mean penetration (0.329 compared with 0.320 mm). At least at early to intermediate-term follow-up, it does not appear that mobile-bearing technology provides any significant clinical benefit following total knee arthroplasty.
Patellar Outcomes
The decision to resurface the patella at the time of total knee arthroplasty remains a cause of contention within the field of arthroplasty. Burnett et al.34 performed a prospective randomized study of patients who underwent cruciate-retaining total knee arthroplasty with or without patellar resurfacing. The investigators followed fifty-seven patients (seventy-eight total knee arthroplasties) for a minimum of ten years and found no differences between the groups in terms of range of motion, Knee Society scores, anterior knee pain, or overall revision rates. However, while the overall frequency and severity of anterior knee pain was similar in both groups, the rate of revision for patellofemoral problems was higher in the unresurfaced group (12% compared with 3%). Even more interesting is the fact that the patients in the nonresurfacing group who later underwent reoperation for resurfacing had short-term but not long-term resolution of the anterior knee pain. This study suggests that the rate and severity of anterior knee pain after cruciate-retaining total knee arthroplasty is independent of patellar resurfacing; patients with and without a resurfaced patella have similar patellar symptoms after total knee arthroplasty. However, patients with an unresurfaced patella are more likely than their resurfaced counterparts to have a reoperation, likely because surgeons assume that anterior knee pain is causally related to the unresurfaced patella. Garcia et al.35 studied the outcomes of isolated patellar resurfacing in patients with anterior knee pain after total knee arthroplasty with an unresurfaced patella. Seventeen patients were managed with resurfacing of the patella and were followed with use of Knee Society clinical and radiographic classification systems. Although overall scores improved after surgery, nearly 50% of patients did not have resolution of anterior knee pain after a minimum duration of follow-up of two years (mean, four years). It is possible that longer-term follow-up of these patients will reveal an even higher rate of persistent anterior knee pain, as reported by Burnett et al.34. It remains unclear whether anterior knee pain after total knee arthroplasty without patellar resurfacing is generated from the articular surface of the patella.
Johnston et al.36 reported the two-year results of the Knee Arthroplasty Trial, a multicenter randomized controlled trial with the participation of 116 surgeons in the United Kingdom. Patients were randomized to treatment with (1) an all-polyethylene or metal-backed tibial implant, (2) patellar resurfacing or nonresurfacing, and (3) a mobile-bearing or fixed-bearing total knee arthroplasty. All subjects were followed and assessed according to several criteria, including the Oxford knee score and the need for additional surgery. The authors found a 6% rate of reoperation after total knee arthroplasty in their series but reported no differences between the groups in terms of clinical results or complications at the two-year interval.
Other Total Knee Arthroplasty Outcomes
There were several larger retrospective outcomes reports that were especially valuable and informative in the year 2009. Lachiewicz and Soileau37 presented the fifteen-year results associated with a modular posterior-stabilized total knee implant. The original prospective cohort included 245 total knee arthroplasties. One hundred and seventeen implants survived and had a minimum of ten years of follow-up. The average age at the time of total knee arthroplasty was sixty-six years, and the average weight of the patients was 82 kg. After a minimum duration of follow-up of ten years, only six patients had had a reoperation after the index total knee arthroplasty, with only one revision due to aseptic loosening and one revision due to polyethylene wear. Only 7% of the 117 knees had radiographic evidence of osteolysis, and the survival rate at fifteen years was 96.8% with mechanical failure as the end point. On the basis of these encouraging results, the authors reported that they continued to use a similar total knee arthroplasty system. Bettinson et al.38 compared all-polyethylene and metal-backed tibial components in a prospective randomized study of 510 consecutive patients with 566 total knee arthroplasties. The patients were evaluated clinically and radiographically at one, three, five, eight, and ten years. Aseptic failure was used as an end point for survival analysis. At ten years, 293 patients had returned for follow-up and there was no difference in survival between the all-polyethylene and metal-backed tibial implants. Both implant types had a survival rate of 97% at ten years. Dalury et al.39 reported on 120 total knee arthroplasties that were performed with use of an all-polyethylene tibial component. All patients were more than seventy years old at the time of primary implantation. The patients were evaluated on the basis of Knee Society scores, radiographic analysis, and physical examination; the minimum duration of follow-up was seven years. Kaplan-Meier analysis with revision as the end point revealed a survival rate of 99.4% at seven years, with no cases of osteolysis and a rate of progressive radiolucency of only 2.5%. In this elderly population, the all-polyethylene tibial component exhibited excellent survival and radiographic outcomes. Dunbar et al.40 conducted a prospective study in which an uncemented trabecular metal tibial component was compared with a standard cemented tibial component with use of radiostereometric analysis. The knees were examined for evidence of tibial migration at six, twelve, and twenty-four months. The authors found that despite a subset of patients in the trabecular metal implant group that exhibited early tibial migration, all patients in the trabecular metal implant group had a well-fixed, stabilized implant by twenty-four months. In contrast, four of the twenty-one subjects in the standard cemented implant group had evidence of progressive implant micromotion at twenty-four months, indicative of an elevated risk of early loosening. The authors concluded that the uncemented trabecular metal tibial implant exhibits a consistent stable fixation that may reveal a lower likelihood for early loosening when compared with traditional cemented tibial implants. Helm et al.41 also studied the outcomes after the use of the uncemented trabecular metal tibial component in a consecutive series of 105 primary total knee arthroplasties. All patients were followed for a minimum of three years in terms of radiographic outcomes and knee scores. The authors found no cases of early loosening and no cases of radiolucent lines. It appears that at early follow-up, the trabecular metal tibial implant exhibits equivalent results in comparison with cemented implants, with possible improvements on radiostereometric analysis. We await longer-term studies to assess the survival of the uncemented trabecular metal tibial implant.
Manley et al.42 examined Medicare data from 1997 to 2004 in a study focusing on the relationship between hospital and surgeon volume and implant survival after total knee arthroplasty in patients sixty-five years of age or older. Kaplan-Meier curves and hazard ratios were calculated at various intervals up to eight years after total knee arthroplasty, and surgeons and hospitals were grouped according to total knee arthroplasty volume. The authors found no effect of surgeon volume on the survival of total knee arthroplasty implants at any of the follow-up periods. However, patients who underwent total knee arthroplasty at a hospital with one to twenty-five cases per year were at a higher risk of revision at five and eight years when compared with patients who underwent total knee arthroplasty at a hospital with >200 cases per year (adjusted odds ratio, approximately 1.5). This study is one of many studies showing that the results of total knee arthroplasty are often influenced by the experience of the hospital. Although several previous studies have suggested an association between surgeon volume and complications after total knee arthroplasty, this specific study suggested that there is no relationship between surgeon volume and early and intermediate-term implant survival.
In order to compare the risks of unilateral versus bilateral knee replacement, Hooper et al.43 evaluated morbidity, mortality, and outcomes in a large register of patients. The New Zealand National Joint Registry was used to study the results of 37,828 hip and knee arthroplasties, including 6772 unilateral total knee arthroplasties, 1360 staged bilateral total knee arthroplasties, and 1012 simultaneous bilateral total knee arthroplasties. The authors found that 69% of simultaneous bilateral total knee arthroplasties were performed by surgeons performing twenty-five total knee arthroplasties or more per year, representing the high-volume group of surgeons. The overall percentage of pulmonary embolism was approximately 0.1%, and there was only one death during the study period. The authors stated that despite previous reports in the literature warning against the risks of simultaneous bilateral arthroplasty, the New Zealand Joint Registry appeared to reveal no difference between unilateral and bilateral procedures with regard to morbidity and mortality. However, it is important to note that some of the studies identifying an increased mortality after bilateral total knee arthroplasty were much larger than the authors’ own study and demonstrated a higher mortality rate, thus potentially having increased statistical power to detect a difference between procedures.
To evaluate the effect of using prophylactic antibiotic-loaded cement during total knee arthroplasty, Namba et al.44 performed a retrospective cohort study with use of a joint registry, an administrative database, and an infection surveillance program. The authors recorded the outcomes of 22,889 primary total knee arthroplasties that had been performed from 2003 to 2007, with a focus on antibiotic cement usage and infection rates; the study represented the largest series involving the use of antibiotic-loaded bone cement to date. The study group had an 8.9% rate of usage of antibiotic cement; the cement appeared to be used preferentially in patients with diabetes, inflammatory arthritis, and a higher anesthesia risk category. Multivariate logistic regression revealed no significant differences in the infection rate between total knee arthroplasties performed with use of antibiotic-loaded cement and those performed with use of antibiotic-free cement. Diabetic patients undergoing total knee arthroplasty with antibiotic cement had a higher infection rate than diabetic patients undergoing total knee arthroplasty without antibiotic cement (1.7% compared with 0.9%), although the difference was not significant. The authors suggested that the routine use of antibiotic-loaded cement cannot be recommended, even for patients who are considered to have a higher risk for infection. Gandhi et al.45 also considered the use of antibiotic-loaded cement (cement loaded with tobramycin) during primary total knee arthroplasty. The authors followed 1625 patients for one year after surgery. The rate of deep infection in the group that received antibiotic-loaded cement was compared with that in the group that received standard cement. The authors found no baseline differences between the groups before surgery and found no difference between the groups in terms of the rate of deep infection (p = 0.84). The authors suggested that antibiotic-loaded cement does not protect against infection after primary total knee arthroplasty. Admittedly, these conclusions differ from large registry data.
In addition to surgeon, hospital, and implant characteristics, there is an increasing body of evidence suggesting that preoperative patient characteristics have a profound effect on outcomes and satisfaction after total knee arthroplasty. Gandhi et al.46 specifically evaluated the relationship between postoperative outcomes and preoperative patient expectations in a study of 1799 patients undergoing total joint arthroplasty. Preoperative comorbidity indices, function, pain, and quality-of-life scores were recorded. Additionally, all patients were asked three specific questions regarding their expectations of recovery time, pain after surgery, and eventual functional level. Patients who had better function before surgery generally had higher expectations of postoperative results and also generally experienced less pain, a faster recovery, and better function after surgery. In contrast, patients with lower function tended to have lower expectations and poorer function after surgery. In fact, a patient's expectation of pain relief after surgery was associated with greater pain relief at one year after arthroplasty (p < 0.05). Lavernia et al.47 also studied patient factors in relation to outcomes in an observational study of 127 hip and knee arthroplasties. There is great variation in the timing of total knee arthroplasty when it comes to the severity of disease. Some patients choose to undergo total knee arthroplasty early in the disease process, while they are still functionally intact, whereas others wait until there is serious functional deficit before proceeding with surgery. The authors reviewed preoperative and several postoperative measures of well-being, function, and quality of life up until three years after total knee arthroplasty. The authors found that patients who had severe functional impairment before surgery also had the worst function and pain three years after total knee arthroplasty and never "caught up" to the patients who had better function before surgery. The study suggested that it may not be optimal to delay total knee arthroplasty to the point that severe functional deficiency occurs because patients may have better outcomes when choosing to have a total knee arthroplasty earlier in the disease process. Choosing the optimal timing to proceed with a total knee arthroplasty remains an important decision that requires further insight and research; however, it is clear that waiting too long can sacrifice an optimal outcome. Kim et al.48 reviewed 438 patients who had had a total knee arthroplasty and identified thirty-three patients who were dissatisfied with the result. Sixteen of these patients had knee-related symptoms, whereas seventeen patients had symptoms unrelated to the knee. The authors found an association between preoperative pain scores, preoperative decreased range of motion, and postoperative dissatisfaction with surgery, even after multivariate logistic regression analysis. The authors gave more credence to the observation that postoperative dissatisfaction and residual symptoms after total knee arthroplasty are often due to factors unrelated to the knee implant. Surgeons must consider patients’ preoperative characteristics when generating appropriate expectations after surgery.
Outcomes of Total Knee Arthroplasty in Specific Patient Groups
The outcomes of total knee arthroplasty in the general population are not necessarily applicable to all subgroups of patients. Often, the presence of underlying disease states and comorbidities can significantly influence early and long-term outcomes. Bae et al.49 retrospectively studied the long-term results of total knee arthroplasty in patients with neuropathic (Charcot) arthropathy. Nine patients with neurosyphilis and concomitant neuropathic arthropathy underwent primary total knee arthroplasty at an average age of sixty years and were followed for an average of twelve years after surgery. All patients received a rotating-hinge prosthesis and experienced improvements in knee function and score after surgery. Although most patients had a stable implant at the time of the most recent follow-up, two patients had a dislocation and one had a deep infection. Dewan et al.50 focused on the subgroup of patients with morbid obesity in order to study the relationship between body-mass index and outcomes after total knee arthroplasty. Knee Society scores were calculated for seventy-one patients with a body-mass index from 30 to 39, thirty-one patients with a body-mass index of >39, and sixty-seven patients with a body-mass index of <30. The mean duration of follow up after total knee arthroplasty was 5.4 years. The authors found that for most measures and study outcomes, there were no differences between body-mass-index groups. However, there was a significant increase in the rate of patellar radiolucency in the highest body-mass-index group. The authors recommend closer monitoring of total knee arthroplasties in patients who are morbidly obese, especially with regard to the patellofemoral compartment.
Outcomes After Revision Total Knee Arthroplasty
The literature supporting decision-making for revision total knee arthroplasty is less developed and less rigorous than that for primary total knee arthroplasty. Furthermore, the choices and strategies shown to be optimal for total knee arthroplasty are not always optimal for revision surgery, which carries a higher risk of complication and failure. The following studies specifically address outcomes after revision total knee arthroplasty.
The use of constrained condylar implants is quite common for revision total knee arthroplasty as there are often challenges to attaining optimal stability through the range of motion. Kim and Kim51 retrospectively studied the results of revision total knee arthroplasty in ninety-seven patients (114 knees) who had an average age of sixty-five years at the time of the index procedure. Aseptic loosening, polyethylene wear, and infection were the reasons for revision in the majority of cases, and constrained condylar implants were used when the posterior cruciate ligament and either the medial or lateral collateral ligament was deficient. Most implants were cemented in the metaphyseal region only, leaving the canal free of cement for a press fit. Patients were followed for an average of 7.2 years and were assessed with use of several knee scores and osteoarthritis indices. The authors found that the ten-year survival rate, with revision or radiographic failure as the end point, was 96%. Five knees required repeat revision, and three knees sustained an extensor mechanism rupture. This report suggested that constrained condylar implants can yield very successful outcomes for ten years after revision total knee arthroplasty, although surgeons must be vigilant after surgery in consideration of a higher complication rate. Peters et al.52 retrospectively studied the four-year results of 184 consecutive revision total knee arthroplasties that were performed with a modular, cementless, press-fit, fluted stem. The most common reasons for revision were aseptic loosening and infection. At the time of the most recent follow-up, there had been only fifteen failures (8%), including nine recurrent infections and four new cases of deep infection. There were no repeat revisions for aseptic loosening and no cases of radiographic loosening. Similar to the previous study, revision total knee arthroplasty with a metaphyseal cementing technique and a diaphyseal press-fit yielded excellent early to intermediate-term results. Long and Scuderi53 reviewed the outcomes of sixteen revision total knee arthroplasties involving the use of porous tantalum cones for defects in the tibia. At a minimum of two years of follow-up, there were no cases of mechanical failure or loosening of any of the cones. Two patients required cone removal because of recurrent infection. It appears that early-term results are quite positive for tantalum augments as they exhibit dependable osseointegration characteristics. Long-term studies are necessary to determine their survival rate.
The efficacy of antibiotic-loaded bone cement may differ when revision total knee arthroplasty is compared with primary total knee arthroplasty. Chiu and Lin54 studied the prophylactic effect of vancomycin-bearing cement (1 g of vancomycin per 40 g of cement) used during revision total knee arthroplasty. The authors conducted a prospective cohort study of 183 first-time revision total knee arthroplasties in patients without an infection. Ninety-three procedures were performed with low-concentration antibiotic cement, and ninety procedures were performed with standard cement. All revisions were performed in a room without ultraviolet light, laminar flow, or body-exhaust suits, and all patients received intravenous antibiotics preoperatively and for thirty-six hours after surgery. At an average of eighty-nine months after revision total knee arthroplasty, there had been six deep infections (7%) in the control group and no infections in the vancomycin-loaded cement group. The difference was significant (p = 0.0130). The authors recommended the use of low-dose antibiotic-laden cement for revision total knee arthroplasty but pointed out the need for larger studies.
Infection
Reports on complications after total knee arthroplasty account for a large proportion of studies in the literature. They are critical for the appropriate education of surgeons and also for the ongoing optimization of patient care.
Jameson et al.55 reviewed primary and revision knee arthroplasties in the Finnish Arthroplasty Register in order to search for risk factors for infection. They identified 43,149 arthroplasties with a median duration of follow-up of three years and also identified 387 reoperations that were performed because of infection. This yielded a 0.9% rate of reoperation for infection in their study. Factors that were found to be significantly associated with reoperation for infection included male sex, seropositive rheumatoid arthritis, a history of fracture about the knee, revision procedures, and the use of hinged and constrained prostheses. In addition, antibiotic-loaded cement combined with parenteral prophylactic antibiotics was protective against infection, especially for patients undergoing revision procedures. Given that patient-related factors appear to be strongly associated with the infection rate, it is likely that a surgeon's or hospital's infection rate may also be dependent on patient demographics and characteristics. Malinzak et al.56 retrospectively reviewed the records for 6108 patients after knee and hip arthroplasty to identify risk factors for infection. The overall observed rate of infection in their cohort was 0.51%, and several patient-related characteristics were identified as having a significant association with the occurrence of infection. Patients with obesity (body-mass index, >50), diabetes, and younger age were more likely to have a deep infection after arthroplasty. In addition, the authors found that infections had a lower probability of developing in patients managed with bilateral arthroplasty.
The treatment of infection has evolved tremendously as we have defined outcomes after various types of infections and types of treatments. Anderson et al.57 retrospectively analyzed twenty-five consecutive patients with a chronic deep infection who had a two-stage procedure involving the use of an articulating spacer. The femoral component was removed, sterilized, and reimplanted, and a new polyethylene liner was inserted. Appropriate microbial identification and parenteral antibiotic treatment was accomplished between stages, during which mobilization was encouraged. After a mean duration of follow-up of fifty-four weeks, only one patient had a reinfection and the average range of motion for the group was 3° to 115°. The findings of this study add to those of several previous studies demonstrating that infections at the site of a total knee arthroplasty can be successfully treated with two-stage procedure involving the use of an articulating spacer. Bradbury et al.58 specifically studied the results after open irrigation, debridement, and component retention for patients with an acute deep infection with methicillin-resistant Staphylococcus aureus. All patients were managed with at least four weeks of parenteral antibiotics and were followed for a minimum of two years after debridement. Similar to previous reports on open debridement for the treatment of Staphylococcus aureus infections after total knee arthroplasty, the authors found an unacceptably low rate of success (18%) in their group of patients. Surgeons who identify an acute infection with Staphylococcus aureus at the site of a total knee arthroplasty, especially when the infection is methicillin-resistant, should be aware of the low rate of success with debridement and should consider removal of components depending on the patient's specific scenario.
Morgan et al.59 studied the accuracy of Gram stains for the diagnosis of infection during revision total knee arthroplasty. Although Gram stains are widely used for diagnosis, with some physicians placing great importance on them, previous studies have questioned the value of Gram stains in the setting of total knee arthroplasty. The authors retrospectively reviewed the records of 945 revision total knee arthroplasties from three institutions and identified 921 cases with an available Gram stain. Patients were defined as infected or not infected on the basis of standard classification methods including cultures, histological findings, and clinical signs. Gram staining was found to have a sensitivity of 27%, a specificity of 99.9%, and an accuracy of 80%. Patients with a true-positive Gram stain had laboratory values for infection that were significantly higher than those for patients with a false-negative Gram stain. Given the unacceptably low specificity of Gram staining and the redundancy of true-positive Gram stains, decision-making was almost never altered on the basis of the result of a Gram stain. Routine Gram staining of synovial fluid does not appear to be valuable on the basis of this study.
Other Complications
Feibel et al.60 reviewed the records of 1190 patients who had had a total knee arthroplasty with an indwelling femoral nerve catheter. Catheters were placed with use of electrical stimulation guidance and were removed two to three days postoperatively for the first 469 patients and twelve hours postoperatively for the next 721 patients. The overall complication rate was 1.5%, with nine femoral nerve palsies, eight major falls, and a 0.2% rate of permanent nerve injury. The authors warned about the complications that may result from the use of continuous femoral nerve catheters.
Koo and Choi61 reviewed the results of nonoperative treatment for fifteen patients who had a complete iatrogenic detachment of the medial collateral ligament at the time of total knee arthroplasty. The authors did not use any specific procedures or repairs, but rather allowed the medial collateral ligament to remain in place to heal after surgery. They also did not recommend a brace or immobilization of any kind after surgery. After a minimum of two years of follow-up, the patients with detachment of the medial collateral ligament had no significant differences in terms of clinical or radiographic outcomes, and the authors recommended nonoperative treatment of iatrogenic medial collateral ligament injuries during total knee arthroplasty. Kusuma et al.62 retrospectively reviewed the results of 1108 total knee arthroplasties in 314 patients who had a lateral release for improved patellar tracking and 794 patients who did not have a release. At an average of 4.7 years after total knee arthroplasty, there were no differences between the groups with regard to Knee Society scores, complication rates, or range of motion. The authors concluded that lateral release does not compromise the patella and is not associated with an elevated rate of complications after total knee arthroplasty.
Marchant et al.63 studied the impact of glycemic control and diabetes on perioperative outcomes after total joint arthroplasty. The Nationwide Inpatient Sample was searched and grouped with an algorithm of ICD-9-CM codes to identify 3973 patients with uncontrolled diabetes, 105,485 patients with controlled diabetes, and 920,555 patients without diabetes. Compared with patients with controlled diabetes, patients with uncontrolled diabetes were found to have a higher risk of stroke (odds ratio = 3.42), urinary tract infection (odds ratio = 1.97), ileus (odds ratio = 2.47), postoperative hemorrhage (odds ratio = 1.99), transfusion (odds ratio = 1.19), wound infection (odds ratio = 2.28), and death (odds ratio = 3.23). Patients with controlled and uncontrolled diabetes had significantly increased hospital charges compared with patients without diabetes. The elevated risk of wound complications in diabetic patients was also identified by Galat et al.64. Those authors reviewed their institutional database and created a matched control study of fifty-nine knees that had an operative procedure within thirty days after a total knee arthroplasty. There was a higher rate of diabetes in the study group, which also went on to have a higher rate of subsequent complications. Patients who had a postoperative reoperation because of a wound problem had a 5.3% risk of needing a third procedure (component removal, muscle flap coverage, or amputation) and a 6.0% risk of deep infection. In comparison, these rates were 0.6% and 0.8%, respectively, for patients without a postoperative procedure for a wound complication. The importance of obtaining wound-healing after total knee arthroplasty is critical in order to avoid what is often a terrible series of postoperative complications.
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