Gross trunnion failure in an elderly obese patient presenting 10 years after total hip arthroplasty with a cobalt chromium femoral head: A case report.

INTRODUCTION: Trunnionosis of total hip prosthesis is defined as corrosion at the head-neck taper junction combined with local tissue reaction. Trunnionosis is a rare complication of total hip arthroplasty (THA) that is often missed in diagnosis. Severe trunnionosis can result in head-neck dissociation, which is called gross trunnion failure (GTF).

CASE PRESENTATION: We describe a case of GTF in a 70-year-old male patient 10 years after right total hip arthroplasty with a cobalt chromium (CoCr) femoral head and a titanium alloy stem. A revision of the stem, cup and femoral head was performed. Six months after surgery, the patient is recovering well and walking.

DISCUSSION: Trunnionosis is associated with hip prostheses with a CoCr femoral head and a titanium alloy stem. Metal Artefact Reduction Sequence (MARS) and serum cobalt and chromium levels are diagnostic tools that can be useful when trunnionosis is suspected.

CONCLUSION: Trunnionosis remains hard to diagnose in an early stage when gross trunnion failure is not present. This case of a 70-year-old patient with gross trunnion failure 10 years after right total hip arthroplasty supports the literature suggesting that a CoCr femoral head, a high body mass index (BMI), and a longer implantation time are risk factors for developing trunnionosis. When conventional X ray and C-reactive protein are inconclusive, serum cobalt and chromium levels should be determined. When serum cobalt and chromium levels are elevated, a MARS MRI should be performed to confirm trunnionosis.