Caveat Emptor: Adverse Inflammatory Soft-Tissue Reactions in Total Hip Arthroplasty with Modular Femoral Neck Implants

Abstract

Modular femoral neck (MFN) implants in total hip arthroplasty facilitate optimizing femoral offset and version while minimizing femoroacetabular impingement1, but component fracture and dissociation have been reported with titanium-alloy MFN implants2-6. Cobalt-chromium MFN components have improved strength compared with earlier designs, but the long-term consequences of wear and corrosion at the femoral neck-stem junction are unknown3,7. Inflammatory metal-hypersensitivity reactions have been most frequently reported in cobalt-chromium metal-on-metal articulations used in total hip arthroplasty and hip resurfacing arthroplasty8,9, but to our knowledge, these reactions have not been described in MFN implants with metal-on-polyethylene articulations. We present two patients with MFN implants who developed partially cystic peri-implant soft-tissue masses with histologic features suggestive of metal hypersensitivity requiring revision arthroplasty. Both patients were informed that data concerning their cases would be submitted for publication, and they provided consent. Case 1. A sixty-three-year-old woman (body mass index, 31.3) with severe osteoarthritis had undergone a left total hip arthroplasty with a 50-mm Trilogy Shell (Zimmer, Warsaw, Indiana), a 36-mm highly crosslinked polyethylene liner (Zimmer), an uncemented titanium-alloy ABG II size-3 modular femoral stem with a 130° cobalt-chromium MFN (Stryker, Mahwah, New Jersey), and a +5-mm 36-mm cobalt-chromium head (Stryker). The patient had an uneventful postoperative course and was discharged on postoperative day three. Seven months later, the patient presented with progressive pain in the left hip. Radiographs showed satisfactory component positioning with no osteolysis, aseptic loosening, or periprosthetic fracture. Blood work showed an elevated erythrocyte sedimentation rate (ESR), C-reactive protein level (CRP), and serum metal ion levels without leukocytosis (Table I). Computed tomography (CT) of the hip demonstrated a 2.3 × 3-cm fluid collection between the gluteus maximus and medius muscles. Aspiration of the hip yielded 2 mL of orange-tainted …