The Journal of Bone & Joint Surgery

The Journal of Bone & Joint Surgery, Volume 86, Issue 12

Scientific Articles | December 01, 2004

Comparison of a Hydroxyapatite-Coated Sleeve and a Porous-Coated Sleeve with a Modular Revision Hip Stem: A Prospective, Randomized Study

Michael P. Bolognesi, MD¹; Ricardo Pietrobon, MD, PhD¹; Phillip E. Clifford, MD¹; T. Parker Vail, MD²

¹ Division of Orthopaedic Surgery, Duke University Medical Center, Box 3332, Durham, NC 27710
² Triangle Orthopaedic Associates, 120 William Penn Plaza, Durham, NC 27704

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The authors did not receive grants or outside funding in support of their research 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. A commercial entity (DePuy, a Johnson and Johnson company) paid or directed, or agreed to pay or direct, benefits to a research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

Investigation performed at the Division of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina

The Journal of Bone and Joint Surgery, Incorporated

J Bone Joint Surg Am, 2004 Dec 01;86(12):2720-2725

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Abstract

Background: Bone ingrowth into a cementless prosthesis can be achieved by both porous and hydroxyapatite coatings. The purpose of this study was to compare the performance of a hydroxyapatite-coated proximal sleeve and a porous bead-coated sleeve in patients managed with a modular revision hip system.

Methods: Between August 1992 and December 1996, fifty-three consecutive femoral revisions performed with an S-ROM stem in fifty-two patients were prospectively randomized at the time of surgery to either a hydroxyapatite-coated or a porous-coated sleeve. All patients were evaluated clinically and radiographically at three months, six months, and yearly for a minimum of two years (average, four years; range, two to 7.5 years). Femoral defects were classified according to the criteria of Paprosky et al. Six patients died and four patients were lost to follow-up, leaving forty-two patients (forty-three hips) as the final study group.

Results: For the entire group, two femoral stems, one of which had been implanted in a hip with a Paprosky type-II femoral defect and the other in a hip with a Paprosky type-IIIB femoral defect, required a repeat revision, one for pain and the other for aseptic loosening. Radiographic evidence of bone ingrowth was observed in 96% (twenty-six) of the twenty-seven femora with type-I or II defects and in 81% (thirteen) of the sixteen femora with type-III defects. Femoral component survival, with use of revision as the end point, was 95% at four years for the entire group. The Harris hip scores were not significantly different when stratified by implant type, but were significantly different when stratified by bone loss (p < 0.05). In the femora with type-I or II defects, no difference was detected between those treated with a hydroxyapatite-coated implant and those that received a porous-coated implant with respect to bone ingrowth. However, in femora with type-III defects, the likelihood of the development of bone ingrowth was 2.6 (95% confidence interval, 1.3 to 5.17) times greater in hips that received a hydroxyapatite-coated implant (all eight developed ingrowth) than in hips that had a porous-coated implant (five of eight developed ingrowth) (p = 0.05).

Conclusions: Bone fixation was achieved more often with hydroxyapatite-coated sleeves in femora with Paprosky type-III defects, but no significant difference was noted in outcomes between the two implant types when used in bone with type-I or type-II femoral defects. Overall, the S-ROM modular hip stem performed better in femora with type-I or II bone defects than in femora with type-III defects.

Level of Evidence: Prognostic study, Level II-1 (retrospective study). See Instructions to Authors for a complete description of levels of evidence.

Figures in this Article

Modular hip stems provide versatility in revision total hip arthroplasty. They allow a single prosthesis to accommodate a variety of proximal bone defects and proximal-distal endosteal diameter mismatches, while optimizing the rotational position of the stem. Proximal bone ingrowth into a cementless prosthesis theoretically enhances proximal load transfer and minimizes proximal bone stress-shielding^1,2, and it can be achieved either by porous coating or by hydroxyapatite coating of the implant.

In the present randomized, prospective study, we compared the performance of a hydroxyapatite-coated proximal sleeve with a porous-coated proximal sleeve in the S-ROM modular hip system (DePuy, a Johnson and Johnson company, Warsaw, Indiana) in revision total hip arthroplasty. The specific aims of this study were to detect whether there are radiographic differences in bone fixation between the two sleeve types and to evaluate the performance of this stem with clinical failure or revision used as the end point.

Materials and Methods

Materials and Methods | Results | Discussion | References

Patient Data

From August 1992 to December 1996, seventy-six femoral revision arthroplasties were performed by the senior author (T.P.V.). The inclusion criterion for enrollment in this study was the need for a revision because of septic or aseptic loosening of the stem. The exclusion criteria were segmental loss of the proximal femoral bone, necessitating revision with a proximal femoral allograft, or the presence of sufficient cancellous bone and normal proximal femoral anatomy in an active patient to allow revision with a standard, cemented stem. Twenty-three revisions performed during this time-period were excluded from the study because of one of the two reasons. The remaining fifty-three consecutive femoral revisions in fifty-two patients were prospectively randomized to hydroxyapatite (twenty-seven hips) or porous coating (twenty-six hips) at the time of surgery. Randomization was performed in the operating room on the day of surgery with use of a coin toss prior to starting the procedure.

Among the patients entered into the study, three in the hydroxyapatite group and seven in the porous-coated sleeve group did not have a minimum of two years of follow-up data available. Six patients died prior to the two-year evaluation, and four were lost to follow-up. Thus, the final study group consisted of forty-two patients with forty-three femoral revisions with use of either a porous-coated (nineteen hips) or hydroxyapatite-coated (twenty-four) proximal sleeve. Informed consent and institutional review board approval were obtained.

The diagnosis at the time of the primary hip replacement in the forty-two patients (forty-three hips) who had been followed for a minimum of two years (average, four years; range, two to 7.5 years) was osteoarthritis in twenty-five hips, trauma or fracture in seven hips, osteonecrosis in seven hips, rheumatoid arthritis in two hips, ankylosing spondylitis in one hip, and dysplasia in one hip. There were twenty-four men and eighteen women with an average age at the time of revision of seventy years (range, thirty-four to eighty-six years). The indication for the index revision was aseptic loosening in thirty-four hips, periprosthetic fracture in conjunction with loosening in five hips (one cemented stem), reconstruction after resection arthroplasty for the treatment of infection in two hips, and persistent pain with a press-fit prosthesis in two hips. The index revision was the first femoral revision in thirty-two hips, the second femoral revision in ten hips, and the third femoral revision in one hip. Strut onlay allografts were applied to the proximal aspect of the femur in eight of the forty-three hips, all of which had type-III femoral bone deficiencies³. No significant difference was detected between the hydroxyapatite-coated sleeve group and the porous-coated sleeve group with respect to age, gender, bone defect, length of follow-up, preoperative Harris hip score, or the use of osteotomy at the time of revision surgery (Table I).

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TABLE I Comparison of the Hydroxyapatite-Coated and Porous-Coated Sleeve Groups

Variable	Hydroxyapatite-Coated Sleeve Group (N = 24)	Porous-Coated Sleeve Group (N = 19)	P Value
Female gender (no. of hips)	9	10	0.2900
Age^*(yr)	70 ± 2.5	70.3 ± 2.6	0.9360
Type of bone defect			0.3860
I	3	0
II	13	11
IIIA	7	6
IIIB	1	2
Duration of follow-up^*(mo)	47.8 ± 4.3	46.8 ± 4.2	0.8717
Osteotomy (no. of hips)	6	4	0.2260
Harris hip score (points)
Preoperative	42.8 ± 2.8	39.8 ± 5.0	0.5962
Postoperative	81 ± 20	71 ± 20	>0.5

The values are given as the mean and the standard deviation.

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TABLE I Comparison of the Hydroxyapatite-Coated and Porous-Coated Sleeve Groups

Variable	Hydroxyapatite-Coated Sleeve Group (N = 24)	Porous-Coated Sleeve Group (N = 19)	P Value
Female gender (no. of hips)	9	10	0.2900
Age^*(yr)	70 ± 2.5	70.3 ± 2.6	0.9360
Type of bone defect			0.3860
I	3	0
II	13	11
IIIA	7	6
IIIB	1	2
Duration of follow-up^*(mo)	47.8 ± 4.3	46.8 ± 4.2	0.8717
Osteotomy (no. of hips)	6	4	0.2260
Harris hip score (points)
Preoperative	42.8 ± 2.8	39.8 ± 5.0	0.5962
Postoperative	81 ± 20	71 ± 20	>0.5

The values are given as the mean and the standard deviation.

Surgical Technique

The proximal fit of the S-ROM stem is provided by a modular proximal sleeve (Fig. 1). The sleeve is conical with terracing of its outer surface. The porous-coated sleeve has titanium beads. In contrast, hydroxyapatite is coated onto a grit-blasted surface.

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Fig. 1: A hydroxyapatite-coated implant was placed into a hip with a type-II defect. A nondisplaced fracture of the greater trochanter is shown in the immediate anteroposterior postoperative radiograph (left). Anteroposterior radiographs made two years (center) and four years (right) postoperatively show a healed fracture with an increase in bone mineral density around the sleeve suggesting areas of proximal load transfer.

A posterolateral approach was used in all patients. Prophylactic antibiotics, ultraviolet lights, and personal exhaust suits were used to decrease the risk of infection. Osteotomy of the femur was performed in ten hips; three had a standard osteotomy of the greater trochanter; one, a trochanteric slide; two, an extended trochanteric osteotomy; two, a cortical window to facilitate cement or device removal; one, a closing-wedge osteotomy distal to the lesser trochanter in a patient with a valgus deformity; and one, a subtrochanteric osteotomy for correction of angular deformity in the diaphysis. Six osteotomies were performed in the hydroxyapatite-coated sleeve group, and four were done in the porous-coated sleeve group. The standard trochanteric osteotomies were fixed with a three-wire technique, placing one wire medially around the lesser trochanter and two wires laterally as tension bands. The extended osteotomies were fixed with cerclage cables.

The femoral canal was prepared with cylindrical reaming of the diaphysis. The distal flutes on the stem measured 1.25 mm greater than the circumference of the stem at the base of the flutes. The diaphysis was reamed to 1.25 mm less than the outer diameter of the distal flutes for straight stems, to encourage diaphyseal engagement of the flutes for rotational stability, and 1.75 mm more than the outer diameter of the flutes for longer, curved stems that engaged the femur through its natural anterior bow. Diaphyseal reaming was followed by preparation of the metaphysis with a short tapered reamer and a finishing cone reamer to the appropriate size, which was determined on the basis of contact with structurally sound cortical bone. The acetabular component was retained with liner exchange in seven hips, was revised for loosening or malposition in twenty-seven hips, was unchanged in six hips, and was the first primary cup implanted in three hips. The acetabular components implanted in this series were all S-ROM titanium, porous-coated acetabular cups (DePuy, a Johnson and Johnson company).

Repair of the short external rotators and posterior capsule or suturing of scar tissue was performed when tissue was available at the time of closure. No capsular augmentation was performed when tissue was not available. Surgical drains were used in all hips. The Harris hip scores⁴ were determined and radiographic examinations were performed at three months, six months, one year, and at one to two-year intervals thereafter.

Radiographic Analysis

Radiographic review was performed at the time of the most recent follow-up, with comparison with the initial postoperative radiographs. All radiographs were read by the same two reviewers, who were blinded with respect to the implant type (hydroxyapatite-coated or porous-coated sleeve). The radiolucencies along the metal-bone interface were documented by a modification of the method of Gruen et al.⁵. Each linear segment of the proximal sleeve was considered as a separate zone, while the distal portions of the stem were evaluated according to the method of Gruen et al. Cortical hypertrophy, osteolysis, changes in cancellous bone density, calcar resorption, heterotopic bone⁶, and subsidence relative to the acetabular teardrop were recorded. Radiographs were assessed for loosening, stable fibrous fixation, or bone ingrowth around the porous proximal sleeve of the prosthesis with use of the criteria described by Engh et al.⁷. Femoral defects were categorized with use of the criteria described by Paprosky et al.⁸. Type-I defects are those with minimal bone damage. Type-II defects are those with metaphyseal bone damage and minimal diaphyseal damage. Type-IIIA defects have metaphyseal and diaphyseal damage, but there is still >4 cm of diaphysis available for femoral fixation, while type-IIIB defects have metaphyseal and diaphyseal damage, with <4 cm of diaphysis available for femoral fixation.

Statistics

Descriptive statistics were performed with use of means and standard deviations or frequencies and percentages. Bivariate analyses were performed with use of t tests and analysis of variance. Two-by-two tables were used to calculate odds ratios with 95% confidence intervals. Multiple regression analysis was used to obtain risk-adjusted estimates of the impact of baseline factors on the change in the Harris hip scores. Trends in the association between Harris hip scores and progressive bone loss were evaluated with use of incremental odds ratios⁹. Sample size calculation was based on the assumption that hydroxyapatite-coated and porous-coated sleeves would have a 35% difference in the rates of radiographic bone ingrowth. Assuming an alpha of 0.05 (two-sided), and power of 80%, the required sample size was estimated to be twenty-six subjects per group.

Results

Materials and Methods | Results | Discussion | References

At the time of the most recent follow-up, the average Harris hip score for the entire group had improved from 41 ± 16 points (range, 6 to 74 points) preoperatively to 77 ± 21 points (range, 24 to 100 points) postoperatively. A power analysis with use of an alpha of 0.05 indicated that 250 patients (125 per group) would be necessary to demonstrate a significant difference between the hydroxyapatite-coated sleeve and porous-coated sleeve groups. Thus, with the numbers available, no significant difference was detected between the groups with respect to the latest Harris hip score or improvement in Harris hip scores at the time of the most recent follow-up. A significant association (p < 0.05) was found between an increasing severity of the bone defect and the postoperative Harris hip score, indicating a higher degree of dysfunction in patients with greater degrees of proximal femoral bone loss (Table II).

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TABLE II Femoral Defect Classification and Harris Hip Score

		Harris Hip Score (points)
Type of Bone Defect	No. (%) of Hips	Preoperative	Postoperative
I	3 (7)	57.0	86.0
II	24 (56)	43.1	70.8
IIIA	13 (30)	37.2	73.8
IIIB	3 (7)	19.0	41.6

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TABLE II Femoral Defect Classification and Harris Hip Score

		Harris Hip Score (points)
Type of Bone Defect	No. (%) of Hips	Preoperative	Postoperative
I	3 (7)	57.0	86.0
II	24 (56)	43.1	70.8
IIIA	13 (30)	37.2	73.8
IIIB	3 (7)	19.0	41.6

Three hips had type-I defects, twenty-four had type-II defects, thirteen had type-IIIA defects, three had type-IIIB defects, and none had type-IV defects in this series of patients. Radiographic evidence of bone ingrowth was seen in 96% (twenty-six) of the twenty-seven femora with type-I or II defects and in thirteen of the sixteen femora with type-III defects. With the numbers available, the difference was not significant (p = 0.1). Patients with type-I or II defects were 2.7 (95% confidence interval, 0.5 to 14.8) times more likely to show radiographic evidence of bone ingrowth than were patients with type-III defects, but this trend did not reach significance (p = 0.1). No significant difference in bone ingrowth was detected between the two types of sleeves for patients with type-I or II bone defects. Similarly, all patients in the hydroxyapatite-coated group were 2.4 (95% confidence interval, 0.4 to 13.1) times more likely to have bone ingrowth than were patients in the porous-coated sleeve group, but this trend also did not reach significance (p = 0.193).

Sixteen femora in this series were classified as having type-IIIA or IIIB bone defects. Eight of the sixteen femora had a porous-coated sleeve implanted, and eight received a hydroxyapatite-coated sleeve. Of the eight femora with a type-III defect that received a porous-coated prosthesis, three demonstrated fibrous union radiographically. In contrast, all eight of the hydroxyapatite-coated sleeves demonstrated bone ingrowth radiographically (Table III). Statistical analysis indicated that stems implanted in femora with type-III defects in the hydroxyapatite-coated sleeve group were 2.6 (95% confidence interval, 1.3 to 5.17) times more likely to develop bone ingrowth than were stems in the porous-coated sleeve group (p = 0.05).

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TABLE III Radiographic Bone Ingrowth Stratified by Implant Type

	Radiographic Bone Ingrowth
Proximal Coating	All Defect Types			Type-III Defect
	Total No. of Hips	Hips with Ingrowth	Total No. of Hips	Hips with Ingrowth
Hydroxyapatite	24	23	8	8
Porous bead	19	16	8	5^*

Compared with the hips with a type-III defect in the hydroxyapatite-coated sleeve group, the difference was significant (p = 0.05).

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TABLE III Radiographic Bone Ingrowth Stratified by Implant Type

	Radiographic Bone Ingrowth
Proximal Coating	All Defect Types			Type-III Defect
	Total No. of Hips	Hips with Ingrowth	Total No. of Hips	Hips with Ingrowth
Hydroxyapatite	24	23	8	8
Porous bead	19	16	8	5^*

Compared with the hips with a type-III defect in the hydroxyapatite-coated sleeve group, the difference was significant (p = 0.05).

With revision as the end point, the probability of femoral stem survival at an average of 3.9 years was 95% for the entire group of patients. Two femoral components were revised; both had hydroxyapatite-coated sleeves. One stem that was placed into a femur with a type-II bone defect was revised because of subsidence and loosening at thirty-three months. The other stem revision was performed in a patient who had a well-fixed stem with persistent thigh pain. This hip had been revised for the second time; the patient had first been seen with a type-IIIB femoral defect requiring cortical strut grafts and a 315-mm stem at the time of the index revision.

Two reoperations were performed because of recurrent dislocation that did not include repeat revision of the implanted stem. One hip dislocated at five months postoperatively and was treated with an acetabular liner exchange and femoral head exchange in addition to trochanteric advancement after several dislocations. The femoral stem was noted to be well fixed at the time of revision. Another hip dislocated initially at twenty-six months postoperatively and was managed with cup revision and head exchange to a longer neck. The femoral stem was well fixed at the time of revision. There were no deep infections.

Eleven hips had a periprosthetic fracture, which included a diaphyseal fracture in six, a nondisplaced fracture of the greater trochanter in two, and a calcar split in three. One diaphyseal fracture occurred as an intraoperative complication, and the remaining five were present prior to surgery. The shaft fractures and calcar splits were fixed with cerclage wires and were thought to be stable after fixation. The six diaphyseal fractures were seen in association with two type-II defects, three type-IIIA defects, and one type-IIIB defect. Both of the hips with a type-II defect (one in the porous-coated sleeve group and one in the hydroxyapatite-coated sleeve group) went on to bone ingrowth and had Harris hip scores of 72 and 77 points at the time of follow-up. Of the three diaphyseal fractures associated with a type-IIIA defect (all in the porous-coated sleeve group), two went on to a fibrous union and one went on to achieve bone ingrowth. The Harris hip scores were 64, 78, and 72 points, respectively, at the time of follow-up. The patient in the hydroxyapatite-coated sleeve group who had a single type-IIIB defect with an associated diaphyseal fracture went on to achieve ingrowth but had a Harris hip score of 30 points at the time of the most recent follow-up because of multiple medical problems. Of the three hips with a calcar split, two had type-II defects and one had a type-IIIA defect. All three went on to achieve bone ingrowth and the Harris hip scores were 51, 55, and 71 points, respectively. With the small numbers available, no independent correlation was found between the presence of an intraoperative fracture and later clinical or radiographic outcome.

Radiographic Analysis

The radiographic assessment revealed proximal radiolucencies at the implant-bone interface in eight hips (19%). Three of the eight stems with radiolucencies around the modular sleeve of the prosthesis were fixed with stable fibrous attachment. One additional stem was loose and causing pain, requiring revision. Cortical thickening at the distal junction of the modular sleeve was seen in six hips (Fig. 1). Condensation of intramedullary cancellous bone was present distally around the polished portion of the stem tip in seventeen hips (40%). Sixteen of the seventeen stems with distal bone condensation had bone-ingrown sleeves. Calcar-remodeling changes were noted in ten hips (23%). Heterotopic ossification was seen in nine hips (21%), with five classified according to the system of Brooker et al.⁶ as stage I; two, as stage II; one, as stage III; and one, as stage IV. Pedestal formation was seen in eight hips (19%). Three of the eight pedestals were incomplete, and four were small complete pedestals in continuity with the cancellous condensation around the distal end of the stem. The remaining pedestal was seen in one hip with a fibrous union, which had had a type-IIIA femoral defect at the time of revision. No hip had severe osteolysis radiographically. All allograft strut grafts were incorporated radiographically by twenty-four months.

Discussion

Materials and Methods | Results | Discussion | References

While successful results have been reported with the use of femoral components with hydroxyapatite coatings in primary hip arthroplasty^10-12, to our knowledge, hydroxyapatite-coated stems have not been evaluated in revision hip surgery. The current study prospectively compares the performance of porous-coated and hydroxyapatite-coated sleeves in otherwise identical S-ROM femoral stems used in revision surgery. While no significant difference was found in bone ingrowth radiographically between the hydroxyapatite-coated and the porous-coated sleeves in hips with type-I or II femoral defects, a significant difference in bone ingrowth was detected between the hydroxyapatite-coated sleeves and the porous-coated sleeves in the subcategory of hips with type-III bone defects. All three fibrous unions were seen in hips with type-III defects. Also, of the six periprosthetic fractures (involving the diaphysis), four were seen in hips with type-III defects. Two of the three fibrous unions occurred in patients with a diaphyseal fracture.

Despite the extensive comparison of the two groups and consideration of as many variables as possible, the analysis is limited by the fact that the numbers are relatively small and the variability of revision arthroplasties is great. Our initial power analysis indicated that the study design would detect significance with twenty-six hips in each arm of the study, assuming a 35% difference between groups. However, we would have needed 125 hips in each group to detect significance given the actual difference in Harris hip scores noted at the time of the most recent follow-up. The variation in the clinical presentation makes the interpretation of results very difficult as well. We tried to address this concern by considering other complicating factors such as periprosthetic fracture, the use of osteotomy in the approach, the diagnosis, and patient demographics. These variables were found to be evenly distributed in both arms of the study and were independent of the type of sleeve used. While the hydroxyapatite coating was superior to porous coating in femora with type-III bone defects, the results cannot be considered to demonstrate an overwhelming superiority of hydroxyapatite coating over porous coating.

The modularity and proximal ingrowth of this stem design may confer some clinical advantage. Cancellous bone loss coupled with cortical expansion proximally can often create a size mismatch between the proximal and distal portions of the femur, which can be accommodated with modular systems. The modular implant used in this study is designed to load the proximal aspect of the bone, making it less likely to result in proximal stress-shielding^13,14. We found some evidence of new bone formation in the proximal part of the femur around well-fixed components. In reports on the S-ROM implant in type-III bone defects with two to eight years of follow-up, Cameron reported that 81% of 104 hips demonstrated a good or excellent result and the rate of repeat revision was 4%^15,16. The results of the current study were similar with respect to clinical outcome (a repeat revision rate of 5%) and radiographic results.

We concluded that the extent of preoperative femoral bone loss must be considered when planning femoral stem revision and component selection. We found that use of proximal ingrowth prostheses with modularity and either a porous-coated or a hydroxyapatite-coated surface can yield excellent results in patients with type-I or II defects. In contrast, in patients with type-III proximal femoral deficiencies our findings suggest that surgeons using a proximally modular stem design should consider the use of a hydroxyapatite-coated proximal sleeve. ?

References

Materials and Methods | Results | Discussion | References

Engh CA, Bobyn JD. The influence of stem size and extent of porous coating on femoral bone resorption after primary cementless hip arthroplasty. Clin Orthop.1988;231: 7-28.2317 1988 [PubMed]

Sumner DR, Galante JO. Determinants of stress shielding: design versus materials versus interface. Clin Orthop.1992;274: 202-12.274202 1992 [PubMed]

Glassman AH, Engh CA. Cementless revision for femoral failure. Orthopedics.1995;18: 851-3.18851 1995 [PubMed]

Harris WH. Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty. An end-result study using a new method of result evaluation. J Bone Joint Surg Am.1969;51: 737-55.51737 1969 [PubMed]

Gruen TA, McNeice GM, Amstutz HC. "Modes of failure" of cemented stemtype femoral components: a radiographic analysis of loosening. Clin Orthop.1979;141: 17-27.14117 1979 [PubMed]

Brooker AF, Bowerman JW, Robinson RA, Riley LH Jr. Ectopic ossification following total hip replacement. Incidence and a method of classification. J Bone Joint Surg Am.1973;55: 1629-32.551629 1973

Engh CA, Massin P, Suthers KE. Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components. Clin Orthop. 1990;257:107-28. Erratum in: Clin Orthop.1992;284: 310-2.284310 1992 [PubMed]

Paprosky WG, Greidanus NV, Antoniou J. Minimum 10-year-results of extensively porous-coated stems in revision hip arthroplasty. Clin Orthop.1999; 369: 230-42.369230 1999 [PubMed][CrossRef]

Maclure M, Greenland S. Tests for trend and dose response: misinterpretations and alternatives. Am J Epidemiol.1992;135: 96-104.13596 1992

Capello WN, D'Antonio JA, Manley MT, Feinberg JR. Hydroxyapatite in total hip arthroplasty. Clinical results and critical issues. Clin Orthop.1998;355: 200-11.355200 1998 [PubMed][CrossRef]

D'Antonio JA, Capello WN, Manley MT, Feinberg J. Hydroxyapatite coated implants. Total hip arthroplasty in the young patient and patients with avascular necrosis. Clin Orthop.1997;344: 124-38.344124 1997

Jaffe WL, Scott DF. Total hip arthroplasty with hydroxyapatite-coated prostheses. J Bone Joint Surg Am.1996;78: 1918-34.781918 1996

Vail TP, Glisson RR, Koukoubis TD, Guilak F. The effect of hip stem material modulus on surface strain in human femora. J Biomech.1998;31: 619-28.31619 1998 [PubMed][CrossRef]

Musgrave DS, Glisson RR, Graham RD, Guilak F, Vail TP. Effects of coronally slotted femoral prostheses on cortical bone strain. J Arthroplasty.1997;12: 657-69.12657 1997 [PubMed][CrossRef]

Cameron HU. The two- to six-year results with a proximally modular noncemented total hip replacement used in hip revisions. Clin Orthop.1994;298: 47-53.29847 1994 [PubMed]

Cameron H. Experience with proximal ingrowth implantation in hip revision surgery. Acta Orthop Belg.1997;63 Suppl 1: 66-8.6366 1997

Topics

durapatite ; femur ; hip region ; hip joint ; hydroxyapatites

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Michael P. Bolognesi, Ricardo Pietrobon, Phillip E. Clifford, T. Parker Vail; Comparison of a Hydroxyapatite-Coated Sleeve and a Porous-Coated Sleeve with a Modular Revision Hip StemA Prospective, Randomized Study. The Journal of Bone & Joint Surgery. 2004 Dec;86(12):2720-2725.

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