Large-head metal-on-metal (MoM) total hip replacements (THR) have given rise to concern. Comparative studies of small-head MoM THRs over a longer follow-up period are lacking. Our objective was to compare the incidence of complications such as infection, dislocation, revision, adverse local tissue reactions, mortality and radiological and clinical outcomes in small-head (28 mm) MoM and ceramic-on-polyethylene (CoP) THRs up to 12 years post-operatively.

A prospective cohort study included 3341 THRs in 2714 patients. The mean age was 69.1 years (range 24 to 98) and 1848 (55.3%) were performed in women, with a mean follow-up of 115 months (18 to 201). There were 883 MoM and 2458 CoP bearings. Crude incidence rates (cases/1000 person-years) were: infection 1.3 vs 0.8; dislocation 3.3 vs 3.1 and all-cause revision 4.3 vs 2.2, respectively. There was a significantly higher revision rate after ten years (adjusted hazard ratio 9.4; 95% CI 2.6 to 33.6) in the MoM group, and ten of 26 patients presented with an adverse local tissue reaction at revision. No differences in mortality, osteolysis or clinical outcome were seen.

In conclusion, we found similar results for small-head MoM and CoP bearings up to ten years post-operatively, but after ten years MoM THRs had a higher risk of all-cause revision. Furthermore, the presence of an adverse response to metal debris seen in the small-head MOM group at revision is a cause for concern.

Cite this article: Bone Joint J 2014; 96-B:868–75.

Introduction

A recent review of the literature on metal-on-metal total hip arthroplasties (THA) revealed the lack of comparative clinical studies with a sufficient sample size and the inclusion of patient-reported outcomes as well as patient activity levels.

Introduction

Large diameter metal on metal cups have been used in total hip arthroplasty advocating superior results with respect to dislocation rates, range of motion and long term survival. The Durom cup used as part of the Durom hip resurfacing system has been incriminated with poor short term results sometimes correlated to incorrect positioning of either the femoral or acetabular component. Our objective was to evaluate short term results of the Durom cup used in conjunction with standard stems.

Introduction

Orthopaedic surgeons are frequently asked to perform a revision total hip arthroplasty (THA) in patients over 80 years of age. Our objective was to evaluate the outcomes after revision THA in patients 80 years or older and compare them to a cohort of patients less than 80 years of age.

Background: Among patients undergoing total hip arthroplasty (THA) 24–36% are obese. The most important long-term complication is periprosthetic osteolysis. While patient activity, implant type and quality of fixation are known risk factors for osteolysis, the literature concerning obesity is sparse and controversial. Our objective was to evaluate the influence of obesity on femoral osteolysis five and ten years after primary THA with a cemented stem.

Methods: Prospective cohort study conducted between 1996 and 2003 among patients undergoing THA (uncemented cup, cemented stem, 28mm head and ceramic-polyethylene bearing surface) inserted with a third generation cementing technique. All patients were seen at either five or ten years, with information regarding BMI and activity, and with radiographic follow-up. BMI was evaluated in three and four categories (< 25, 25–29.9 (reference category), 30–34.9 and ≥35 kg/m²). Activity was assessed using the University of California, Los Angeles (UCLA) activity scale (1–10 points). Main outcome was the radiographic assessment of femoral osteolysis. Secondary outcomes were polyethylene wear and revision for aseptic loosening.

Results: We included 503 THAs in 433 patients. Of those 241 THAs (48%) were seen at five years and 262 (52%) at ten years. Osteolytic lesions were identified in forty-four cases, twenty-four in 181 normal weight patients (13.3%), eleven in 205 overweight (5.4%), seven in ninety-six obese class I (7.3%), and two in twenty-one obese class II patients (9.5%). Activity was highest in normal weight patients (mean UCLA score 5.5, ±2.0) and lowest in patients obese class II (mean UCLA score 4.8, ±1.7). Univariate as well as multivariate logistic regression analysis adjusting for activity, cementing quality, age, and sex did not show an increased risk of osteolysis in obese compared to overweight patients (adjusted OR 1.4, 95% CI 0.6; 3.7). A significantly higher risk was found in normal weight patients (adjusted OR 2.6, 95% CI 1.2; 5.7). Total mean polyethylene wear was significantly lower in obese compared to normal/overweight patients (p=0.024). Revision for aseptic loosening of the stem was necessary in 4 patients (3 normal weight patients and 1 overweight patient).

Conclusions: We did not find an increased risk for femoral osteolysis or revision for aseptic loosening in obese patients five and ten years after primary THA with a cemented stem.

Objective: The Morscher press-fit cup is a cementless, porous-coated acetabular component. The objective of this study was to assess clinical and radiological outcomes, patient satisfaction and complications at 10 years.

Methods: Prospective cohort study including all consecutive primary THAs with the Morscher cup operated by multiple surgeons of a University hospital between March 1996 and April 1998. Patients were evaluated at 120 months (±7.2 months) with clinical and radiological follow-up, patient satisfaction and questionnaire assessment, using the Harris Hip Score (HHS), WOMAC and SF-12. Follow-up examination was done by two physicians who had not performed the operations.

Results: 421 THAs were performed in 389 patients (54.6% women; mean age 69.3, range 28–98). In 80% the diagnosis was primary osteoarthritis. All stems were cemented except for 18 patients (4.3%). One-hundred-twenty-two patients (29.0%) had died, 27 (6.4%) were lost-to follow-up, 24 (5.7%) were unable to attend because of poor general health and 27 (6.4%) refused, thus leaving 221 hips, for which 176 x-rays were available.

None of the patients required cup revision for aseptic loosening. Complications included 12 dislocations and 3 deep infections resulting in 2 total revisions. In 3 patients the stem was revised for aseptic loosening at a mean of 63 months. At 10-years the survivorship was 98.6% (95% CI 96.7; 99.4) with endpoint revision for any cause.

Mean total wear was 0.89 mm (±0.5). 32 cups (18.8%) with a cup inclination > 45° had a mean wear of 1.06 mm (±0.5), whereas 138 cups (81.2%) with inclination < 45° had a mean wear of 0.86 mm (±0.5), p=0.036. In 16 cases osteolytic defects around the stem were present. The outcome scores at 10 years were: HHS 85.9 (±14.1), WOMAC pain 70.7 (±24.7), WOMAC function 68.8 (±24.5), SF-12 physical score 40.3 (±9.2) and mental score 47.0 (±10.4). Ninety-four percent of the patients were satisfied or very satisfied.

Conclusions: The Morscher acetabular replacement cup provides excellent results at 10 years. None of the patients had to be revised for aseptic loosening of the cup, patient satisfaction was high, and clinical results were very good.