Orthopedic Oncology and Metabolic Bone Disease
Core rules
- Bone metastases are common in breast, prostate, lung, kidney and thyroid cancer; pathologic fracture risk is estimated with Mirels score and clinical judgment.
- Primary bone tumours have age-specific patterns: osteosarcoma in adolescents, Ewing sarcoma in children, giant cell tumour in young adults, and myeloma in older adults.
- Refer suspected primary bone tumours before biopsy; an ill-planned biopsy can compromise limb salvage.
- Osteoporosis is diagnosed by DXA T-score ≤ −2.5 or fragility fracture; treat with calcium, vitamin D, exercise and antiresorptive or anabolic drugs.
- Paget disease causes bone pain, deformity and elevated alkaline phosphatase; bisphosphonates are used when symptomatic.
Worked example
A 65-year-old with breast cancer has thigh pain and a lytic femoral lesion. Reasoning: assess impending fracture with Mirels criteria, check calcium and renal function, and involve oncology. Prophylactic fixation may be indicated before radiotherapy.
Traps
Do not biopsy a bone lesion before specialist review. Do not ignore hypercalcaemia. Do not treat all lytic lesions as infection.
Key points are listed separately.