Comparison of a hydroxyapatite-coated sleeve and a porous-coated sleeve with a modular revision hip stem. A prospective, randomized study.
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.


METHODS
Prognostic study, Level II-1 (retrospective study). See Instructions to Authors for a complete description of levels of evidence.
Bolognesi
Michael P
MP
Division of Orthopaedic Surgery, Duke University Medical Center, Box 3332, Durham, NC 27710, USA.
Pietrobon
Ricardo
R
Clifford
Phillip E
PE
Vail
T Parker
TP
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D020099:Coated Materials, Biocompatible; D017886:Durapatite; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D016348:Osseointegration; D016062:Porosity; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation; D013499:Surface Properties
D020099:Coated Materials, Biocompatible; D017886:Durapatite