Clinical Case Study: Pathologic Subtrochanteric Femur Fracture Revealing Multiple Myeloma
Key Takeaway
Multiple myeloma diagnosis following a pathologic femur fracture involves key steps. Imaging reveals lytic lesions and osteopenia. Lab findings include hypercalcemia, anemia, and elevated creatinine. Definitive diagnosis relies on serum protein electrophoresis showing monoclonal gammopathy and urine protein electrophoresis detecting Bence-Jones proteinuria.
A 72-year-old male presents with sudden left hip pain after a trivial fall at home. He describes a 6-month history of worsening back pain and recent constitutional symptoms. Examine these radiographs and describe your initial assessment and differential diagnosis.
Candidate: The radiograph shows a comminuted subtrochanteric femur fracture. The bone quality is poor, showing lytic lesions and cortical thinning. Given the history of back pain and weight loss, this is a pathologic fracture. I would suspect metastatic disease, particularly Multiple Myeloma, lung, or prostate cancer. My next step would be a full systemic workup including FBC, Calcium, Renal function, and myeloma screen.
Focusing purely on the fracture classification (e.g., "This is an AO 32-A3 fracture") and jumping to surgical planning before addressing the systemic pathology. Failing to mention specific screening markers (CRAB criteria) or dismissing the back pain as "just arthritis" despite the red flags.
The candidate should state: "This is a pathologic subtrochanteric fracture. Radiographically, I see extensive lytic destruction with cortical breach and a 'moth-eaten' appearance. My primary differential is Multiple Myeloma, given the age, constitutional symptoms (weight loss, fatigue), and reported axial bone pain. I would investigate with the CRAB criteria (Calcium, Renal, Anemia, Bone lesions). I must rule out metastatic carcinoma (prostate, breast, lung, kidney) by checking PSA, protein electrophoresis, and staging imaging. The patient requires urgent stabilization after medical stabilization of potential hypercalcemia and anemia."
The patient is diagnosed with Stage III Multiple Myeloma. You are planning surgical intervention for the subtrochanteric fracture. What are your primary surgical objectives and your implant of choice?
Candidate: My objectives are pain relief, early mobilization, and local stability to prevent further collapse. I would choose a long cephalomedullary nail. This provides load-sharing fixation and allows me to bypass the entire femoral diaphysis to protect against future fractures in the lytic bone.
Suggesting an extramedullary device like a dynamic hip screw (DHS) or a locking plate. In the setting of diffuse, poor-quality bone in myeloma, these constructs suffer high rates of hardware failure and pull-out due to the inability to achieve adequate purchase.
Structure the answer: 1) Biomechanical strategy: Use a long intramedullary nail for load-sharing fixation. 2) Implant length: The nail must extend to the distal femoral metaphysis to bypass all proximal lytic lesions and prevent stress risers. 3) Augmentation: Given the severe bone compromise, I would strongly advocate for PMMA cement augmentation of the femoral head/neck screws to ensure mechanical integrity. 4) Procedure: Always perform an intra-operative biopsy of the lesion to confirm tissue diagnosis.
How does the Mirels scoring system influence your surgical threshold in this patient, and would you consider prophylactic fixation for the contralateral femur?
Candidate: The Mirels score assesses the risk of impending fracture based on site, size, nature, and pain. A score of 9-12 indicates a high risk of fracture. If the contralateral side shows similar lytic lesions in a weight-bearing location, I would consider prophylactic fixation to prevent a future pathologic fracture, especially if the patient is symptomatic.
Failing to understand the "preventative" philosophy of orthopedic oncology. Simply waiting for the patient to return with a second fracture is a failure in the duty of care for a systemic malignancy where the patient's survival is limited and quality of life is the primary goal.
Systematically break down the Mirels criteria (Location, Size, Type, Pain). For this patient, the lesion is high risk. I would evaluate the entire skeletal survey. If the contralateral femur has a Mirels score ≥ 9, prophylactic intramedullary fixation is indicated. This minimizes the risk of a "second hit," allowing the patient to focus on their oncology treatment rather than further orthopedic complications.
