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.

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.

We conducted a longitudinal study including patients with the same type of primary hybrid total hip replacement and evaluated patient activity and femoral osteolysis at either five or ten years post-operatively. Activity was measured using the University of California, Los Angeles scale. The primary outcome was the radiological assessment of femoral osteolysis. Secondary outcomes were revision of the femoral component for aseptic loosening and the patients’ quality of life. Of 503 hip replacements in 433 patients with a mean age of 67.7 years (30 to 91), 241 (48%) were seen at five and 262 (52%) at ten years post-operatively. Osteolytic lesions were identified in nine of 166 total hip replacements (5.4%) in patients with low activity, 21 of 279 (7.5%) with moderate activity, and 14 of 58 (24.1%) patients with high activity. The risk of osteolysis increased with participation in a greater number of sporting activities. In multivariate logistic regression adjusting for age, gender, body mass index and the inclination angle of the acetabular component, the adjusted odds ratio for osteolysis comparing high vs moderate activity was 3.6 (95% confidence interval 1.6 to 8.3). Stratification for the cementing technique revealed that lower quality cementing increased the effect of high activity on osteolysis. Revision for aseptic loosening was most frequent with high activity. Patients with the highest activity had the best outcome and highest satisfaction.

In conclusion, of patients engaged in high activity, 24% had developed femoral osteolysis five to ten years post-operatively.

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.

Purpose of the study: Revision total hip arthroplasty (rTHA) is associated with higher mortality than primary total hip arthroplasty (pTHA). The functional outcome after rTHA is globally satisfactory but less so than with primary implantation. Nevertheless, data are scarce. Patients undergoing revision procedures are older and have more co-morbid conditions. In this context, we evaluated quality-of-life and patient satisfaction five years after implantation, comparing rTHA versus pTHA. We analyzed the impact of age, obesity, and co-morbid conditions.

Material and methods: The study cohort included all patients undergoing pTHA (n=471) OR rTHA (n=124) in our unit between 1996 and 2000. Five years postoperatively, we noted the Harris hip score (HHS) and patient satisfaction, assessed on a visual analog scale (VAS) from 1 to 10.

Results: The rTHA patients were older (72 yeras versus 68 years, p=0.004), more frequently obese (BMI30: 33% versus 19%, p=0.003) and presented more co-morbid conditions involving medical ( 2: 46% versus 21%, p< 0.001) and orthopedic ( 2: 13% versus 7%, p=0.053) problems. Five years after surgery, quality-of-life and patient satisfaction were much lower after rTHA than after pTHA (HHS < 70; 31% versus 9%, p< 0.001; satisfaction score 8: 68% versus 85%, p< 0.001). Adjustment for the preoprative status (ASA, medical and orthopedic comorbidity, BMI, gender, age) attenuated these differences which nevertheless remained significant [non-adjusted HHS difference: 11.5 (95%CI: 7.4–15.7); adjusted difference: 8.8 (95%CI: 5.5–12.1)]. In both groups, a low HHS was associated with BMI ≥ 30, poor preoperative function, 2 joints affected, elderly age. Obesity was associated with even poorer results after rTHA than after pTHA (non-adjusted difference, p=0.026).

Discussion: Quality-of-life and patient satisfaction at five years were clearly poorer after rTHA than after pTHA. This is in agreement with data in the literature. The difference is explained in particular by greater patient age and more associated comorbidities for rTHA. Obesity is a prognostic factor which is more unfavorable after rTHA than after pTHA.

Conclusion: Considering the risks and benefits of revision surgery, it is important to recognize not only the surgical factors but also the characteristic features of the patients.