Unusual Failure of Modular TKA Prosthesis and Screw Migration following Revision Total Knee Arthroplasty.

INTRODUCTION

The use of modular implants for revision TKA are ever increasing in number due to their definitive advantage over their monoblock counterparts by providing the surgeon with the versatility needed to achieve equal gaps and manage bone defects. This superiority comes at the cost of certain unique complications attributable to its modular design such as loosening and fractures at the areas of component coupling that are prone to fatigue failure with suboptimal fixation.

CASE REPORT

We present a case of modular femoral component failure in a 59-year man of Asian decent after revision TKA secondary to disengagement and migration of the extension stem locking bolt of a Total Condylar-III prosthesis. Patient presented with pain, effusion, and instability 2.5 years after stage-2 revision TKA. Radiographs revealed migration of the femur-stem locking bolt into the joint cavity. The femoral component and stem were loose. The locking bolt was extracted, and he underwent re-revision surgery with revised femoral components.

CONCLUSION

Stem-condylar junction of modern modular TKA implants are prone to early loosening and failure. This diagnosis should be anticipated on serial follow-up radiographs and in patients who complain of sudden onset of instability following revision surgery.