Metal-on-metal hip arthroplasty: does early clinical outcome justify the chance of an adverse local tissue reaction?

Abstract

Larger diameter metal-on-metal (MOM) bearing hips offer the possibility of low wear and reduced risk of dislocation. We reviewed the first 126 patients (131 hips) who had a large-head (36-mm) MOM bearing surface to report the early clinical outcome and especially to determine the occurrence of dislocation and wear-related concerns. The minimum followup was 5 years (mean, 5.6 years; range, 5-7 years). We found a 98% survivorship free of component revision. No hips had been revised for dislocation. Three hips (2%) had small femoral osteolytic lesions. Because this series of patients did not completely represent our experience with this bearing surface, we queried our database for the 828 patients (945 hips) that had the same bearing surface from April 2001 to December 2008. Three patients (0.3%) had a local reaction to the MOM bearing surface on revision-retrieved tissue. All three patients presented with elevated inflammatory indices, and a purulent-appearing joint effusion at revision. The possibility of infection and the delay in diagnosing a reaction to the MOM bearing with pathology complicated management of these three patients. We continue to use this bearing surface because the 5-year results are comparable to other bearing surfaces, however, we counsel patients that a local adverse reaction to the MOM bearing surface may be a factor contributing to reoperation.

Level of evidence: Level IV, retrospective clinical cohort. See Guidelines for Authors for a complete description of levels of evidence.

Figures

Fig. 1

A picture of the bearing surface is shown so that readers unfamiliar with the implant can better understand the design. It is possible that the design and manufacturing of metal-on-metal bearing surfaces may influence the results. The Pinnacle titanium porous-coated cup with locking taper is shown. The bearing surface consists of a high carbon content Ultamet liner and 36-mm ball with 100 μm ± 20 μm clearance.

Fig. 2A–C

(A) An immediate postoperative AP radiograph is shown for comparison to later radiographs. (B) A 5.6-year followup radiograph of the same patient shows greater trochanteric osteolysis having a geographic pattern and well-defined boarders. (C) A lateral view of same osteolytic lesion is shown. The occurrence of radiographically visible osteolysis may be indicative of a reaction to metal-on-metal wear.

Fig. 3

A photomicrograph shows tissue from case 2. There is a high-density and extent of lymphocyte infiltration in this section of capsular tissue. (Stain, hematoxylin and eosin; original magnification, ×40.)