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. We conducted a prospective cohort study including all metal-on-metal and conventional polyethylene (PE)-ceramic THAs with an uncemented cup (Morscher press-fit cup), a 28mm head and operated upon via a lateral approach at our University hospital between 1/1999 and 12/2008. Only THAs for primary osteoarthritis were included. The study population is part of the Geneva Hip Arthroplasty Registry, a prospective cohort followed since 1996. The following outcomes were compared between the two groups (metal-on-metal=group 1 vs. PE-ceramic bearing=group 2): (1) Complication rates with respect to infection, dislocation and revision, (2) Radiographic outcomes (presence of linear or focal femoral osteolysis, loosening), and (3) Clinical outcomes (Harris Hip score increase, SF-12, activity and patient satisfaction evaluation, presence of groin pain). Patients operated between 1/1999 and 12/2004 were evaluated five years postoperatively by an independent assessor. Cox regression analysis was used to compare incidence rates while adjusting for differences in baseline characteristics.Introduction
Methods
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. We prospectively followed all patients with a large diameter metal-on-metal articulation (Durom) and a standard stem operated upon between 9/2004 and 9/2008. Patients were seen at follow-up for a clinical (Harris hip score=HHS, UCLA scale and patient satisfaction), radiographic and questionnaire assessment.Introduction
Methods
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.
We present two patients with swelling of the groin following metal-on-metal total hip replacement without radiological signs of component loosening. MRI in both patients showed a round shaped intrapelvic lesion ventral to the femoral head. During surgery we found cystic structures filled with fluid and necrotic masses. After resection the metal head and insert were changed to a ceramic head and a polyethylene insert. Although two different kinds of CoCrMo alloy were used in the metal-on-metal THR (Sikomet: low carbon content-Metasul: high carbon content) histopathological analysis in both cases showed typical morphological signs of hypersensetively determined inflammation. Despite the distinct soft tissue reaction bony component integration was unaffected. In our opinion open resecion of the cystic lesion and changing of the metal-on-metal articulation is the treatment of choice. As we do not have any reliable testing for clinical use to predict a hypersensitive reaction to metal wear after implantation of metal-on-metal THR this articulation surface should not be used in cases where allergy to metal is suspected.