You are reviewing this 72-year-old patient who has presented with a 12-month history of worsening groin pain following a primary THA performed 15 years ago. Based on the provided imaging and the Paprosky classification system, how would you systematically describe the findings and plan your surgical approach?
Candidate: The patient has aseptic loosening of both components. On the acetabular side, there is superior migration and a Type IIIA Paprosky defect. The femur has a Type IIB defect with proximal bone loss but an intact distal diaphysis. I would plan for a revision THA using a modular cup with augments and a long, distally fixing revision stem.
Candidates often jump straight to the "what" (implants) without defining the "why" (bone biology/defect mechanics). Failing to mention the status of the distal diaphysis, the specific mechanism of fixation for the revision stem, or the structural implications of the acetabular defect (e.g., hip center rotation) is a common weakness.
A high-scoring answer is structured: 1) Clinical Summary: Confirming aseptic loosening and ruling out infection. 2) Bone Defect Analysis: Specifically identifying the Paprosky IIIA acetabular defect (superior segmental loss, hip center migration) and IIB femoral defect (proximal metaphyseal loss with intact distal diaphysis). 3) Surgical Strategy: Linking the defects to the reconstruction—using a porous-coated cup with superior trabecular metal augments to restore the center of rotation, and a modular, proximally coated, distally fixing stem to bypass proximal bone loss while achieving diaphyseal purchase. 4) Technical Considerations: Emphasizing the need for a trochanteric osteotomy to ensure safe component extraction and address the abductor deficiency.
During the procedure, you perform an extended trochanteric osteotomy (ETO) to remove the well-fixed cemented femoral stem. What are the critical technical goals during the reconstruction phase to ensure long-term stability and functional recovery?
Candidate: I need to reattach the trochanter securely using cables. I must also ensure the new stem is stable distally and that I restore the patient's leg length and offset. I should also manage the soft tissues carefully.
Vague responses like "attach with cables" without specifying the tensioning, the role of impaction grafting, or the impact on abductor lever arms. Failing to mention the specific post-operative weight-bearing protocol required after an ETO is a significant omission.
The answer must be systematic: 1) Trochanteric Fixation: Emphasize the use of tension-band wiring or high-strength cables in a figure-of-eight configuration to promote union and restore the abductor tension. 2) Biomechanical Restoration: Highlight the role of modularity in restoring leg length, offset, and version—essential for preventing dislocation and Trendelenburg gait. 3) Metaphyseal Reconstruction: Mention the use of cancellous impaction grafting within the metaphyseal area to provide a biological scaffold and secondary support. 4) Rehabilitation: State clearly that a protected weight-bearing protocol (e.g., toe-touch for 6 weeks) is mandatory to allow for bony healing of the osteotomy site.
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