Advanced Diagnosis & Surgical Planning for Periprosthetic Hip Fractures
Key Takeaway
Diagnosing periprosthetic hip fractures combines clinical examination and comprehensive imaging. Initial AP/lateral X-rays assess fracture pattern and stem relation. A CT scan is vital to delineate comminution, evaluate existing stem stability, and quantify bone loss. This advanced imaging guides meticulous pre-operative templating, crucial for selecting the appropriate revision stem and planning fixation strategies for complex cases.
You are on-call and receive a 78-year-old female patient who sustained a low-energy torsional injury to her right hip. She has a history of a cemented total hip arthroplasty (THA). Radiographs show a spiral fracture of the femoral shaft extending to the tip of the prosthetic stem. Describe your initial assessment and the importance of the classification system you would use.
Candidate: I would perform a thorough clinical assessment, including neurovascular status and skin integrity. I would classify the injury using the Vancouver Classification. Based on the radiographs showing a fracture at the stem tip, I would provisionally call it a Vancouver Type B1, implying a stable stem. This guides the treatment, as B1 fractures are typically treated with internal fixation, whereas B2 or B3 would require revision surgery.
Candidates often rely solely on plain films, forgetting that up to 20% of B1 fractures are actually loose (B2) intraoperatively. Failing to mention the limitation of plain radiographs or the potential need for revision equipment in the OR is a significant oversight.
The candidate must explicitly state: "The Vancouver Classification is the gold standard because it links anatomy, implant stability, and bone stock to the surgical plan." They should highlight that while the fracture appears B1 (stable stem), clinical decision-making requires caution as radiographs have low sensitivity for micromotion. A perfect answer notes the requirement for CT imaging (MARS) to assess the cement mantle and states that a "revision-ready" setup is mandatory regardless of the B1 radiographic appearance.
You have decided to proceed with ORIF for this Vancouver B1 fracture. What are the specific biomechanical principles you must adhere to, particularly concerning the proximal fixation around the cemented stem?
Candidate: The goal is relative stability. I would use a long locking plate that spans the fracture and overlaps the tip of the prosthesis by at least two femoral diameters to avoid a new stress riser. Proximally, because the canal is occupied by the stem and cement, I would use cerclage cables or unicortical locking screws to avoid damaging the implant.
Neglecting the "working length" concept or failing to emphasize the vascularity of the bone. Candidates often ignore the posterior vascular supply (perforating branches of the profunda femoris) and risk devascularizing the fracture during plate application.
The candidate should categorize the answer into three pillars: 1. **Biomechanical:** Load sharing construct, long plate with adequate proximal overlap (2x cortical diameter). 2. **Biological:** Preservation of the posterior periosteal blood supply by avoiding stripping the linea aspera. 3. **Fixation Technique:** Circumferential cable fixation proximally to maintain stability without violating the cement mantle/implant, and bicortical distal screw fixation to provide an adequate bridge.
During the procedure, you perform a "push-pull" test on the stem and it demonstrates subtle motion. How does this change your management, and what is your immediate surgical priority?
Candidate: This indicates a Vancouver Type B2 fracture, as the stem is loose. I would abandon the plan for isolated ORIF and proceed to revision arthroplasty. My priority would be to extract the existing stem and cement, and replace it with a long, diaphyseal-engaging revision stem to achieve stability.
Trying to "salvage" the situation by adding more cables or trying to bone graft a loose stem. A loose stem in a periprosthetic fracture is an indication for revision; anything less will lead to early implant failure.
The candidate must demonstrate surgical decisiveness: "The diagnosis is now Vancouver B2. I will transition to revision arthroplasty." They should mention using an extensile approach, careful cement removal to avoid cortical perforation, and the use of a fluted, tapered, modular long-stem prosthesis that bypasses the fracture site by at least two cortical diameters to regain distal fixation.
