Catastrophic Wear in Total Hip Arthroplasty. Complete Wear-Through of a Metal-Backed Acetabular Component

A unique case of catastrophic wear of a total hip arthroplasty is presented. This brief report demonstrates the presentation of catastrophic wear of a modular acetabular component with protrusion of the femoral head through a modular metal-backed titanium cup. During the revision surgery, the polyethylene was found to have disengaged from the cup, and the cup was pistoning on the femoral neck. Significant metallosis and bone loss was found. The presence of severe metallosis mimicked bone on the preoperative radiograph and obscured the severity of the osteolysis seen on imaging.

Key Points

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Severe metallosis can occur from nonarticulating surfaces of the implants.
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It is important that patients be routinely monitored to prevent catastrophic complications associated with older-generation implants.
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The amount of metallosis and bony destruction should not be underestimated on plain radiographs, and surgeons must be prepared to deal with massive bone loss that can be caused by metal debris.

The presentation of catastrophic wear of a metal-backed modular titanium acetabular component with complete wear-through of the acetabulum is discussed. Intraoperative findings of significant metallosis and bone loss were found. Treatment of the hip is outlined.

Case report

The patient was referred to clinic owing to concerns about increased hip pain and decreased hip motion after a total hip arthroplasty conducted 17 years previously. This 49-year-old man had a history of coronary artery disease with previous stent placement, hypertension, and a rotator cuff repair. He was on disability, and had smoked for 30 years.

His hip replacement was conducted elsewhere, with good initial results and function. A year before presentation he began to have progressive hip pain, popping, and squeaking. Four months before presentation, his complaints were isolated to increasing groin pain, limited motion, and progressive leg-length discrepancy. Physical examination revealed an obese man (body mass index, 38 kg/m ²). He was neurovascularly intact, and had an antalgic gait and positive Trendelenburg gait. His motion was limited to 70° of flexion, with no internal or external rotation. His leg-length discrepancy was 1.5 cm. Imaging revealed his femoral head had worn through the Harris-Galante 1 metal cup and was articulating within a halo of bone medial to his acetabulum ( Fig. 1 ).

Blood work was negative for infection, with an erythrocyte sedimentation rate of 17 mm/h and a C-reactive protein level less than 0.29 mg/dL.

He was consented and taken to the operating room for a revision total hip arthroplasty. Significant metallosis and proximal femoral bone loss was found ( Fig. 2 ). What appeared on imaging to suggest a hypertrophic bony response around the proximal femur was actually hypertrophic tissue containing metal debris with complete loss of proximal femoral bone. The polyethylene liner was found floating free in the inferior pouch of the capsule, and was not worn through. However, the titanium acetabular component had completely worn through ( Fig. 3 ). The acetabulum was grossly loose, and the femoral component was able to piston axially through the metal cup. Where visible or prominent after reaming the acetabulum, screws were removed. The cup was revised to a 60-mm trabecular metal cup with screw augmentation. Although grossly stable, there was significant bone loss proximally around the fiber metal mesh, and femoral fixation was considered to be insufficient. The stem was therefore revised to an 8-inch, fully porous, coated stem with excellent distal fixation. In an attempt to protect the very thin greater trochanter and lateral bone, an extended trochanteric osteotomy was conducted. Because of the extremely fragile nature of the greater trochanter, the patient was placed in an abduction brace and was toe-touch weight bearing only.