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Larger diameter femoral head
6%
73/1324
Ceramic femoral head
88%
1166/1324
Cemented femoral fixation
3%
35/1324
Cemented acetabular fixation
2%
20/1324
Diaphyseal engaging femoral stem
1%
17/1324
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This patient has osteolysis along the medial femoral calcar in the setting of elevated cobalt and chromium levels, indicative of trunnionosis. Use of a ceramic head eliminates the interaction between the cobalt chromium femoral head and the titanium femoral stem. Trunnionosis is wear that occurs at the femoral head-neck interface and has recently been identified as a more recognized source of THA failure. Metal ions released from this interface may lead to adverse local tissue reactions (ALTRs), osteolysis and failure. Cobalt chrome femoral heads can release ions at the trunnion junction with the titanium stem. Treatment for this problem consists of removing the metal femoral head and replacing it with a ceramic head and titanium sleeve, thereby eliminating the offending cobalt and chromium ions entirely. Metal on polyethylene hip replacements with ion levels >1.0 mcg/L should raise suspicion for possible trunnion issues and warrant further workup and evaluation. Jacobs et al reviewed corrosion at the head-neck junction. They report that ALTR is related to the summation of debris released from both the bearing surface and the modular taper junction, and that this has only been reported in instances in which at least one component was CoCr alloy. They conclude that optimizing material selection is one way in which surgeons can combat this phenomenon. Urish et al reviewed the basic concepts relating to trunnion corrosion in THA. They report that the femoral head-neck trunnion creates an optimal environment for corrosion to occur because of the limited fluid diffusion, acidic environment and increased bending moment. They conclude that femoral head material also effects the amount of corrosion and that ceramic heads should be considered. Figures A demonstrates a well-positioned total hip arthroplasty. Figure B shows significant lysis and resorption of the medial femoral calcar. Figurer C is an MRI demonstrating large pseudotumor around the left hip replacement. Incorrect Answers: Answer 1: Larger femoral heads have been associated with increased risk of trunnionosis. Answer 3 & 4: Component fixation is not related to the development of trunnionosis. Answer 5: The problem in this case is related to trunnion wear, not femoral stem fixation.
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