Overview
Metastatic carcinoma is the most common malignancy treated by orthopaedic surgeons: about 8,000 new sarcomas are diagnosed yearly in the United States versus over a million carcinomas, and an estimated 50% to 80% of carcinoma patients have bone metastases at death. As systemic treatment improves, survival after the diagnosis of bone metastases is lengthening, so the surgeon should not approach these patients fatalistically. Orthopaedic care aims to minimize pain, maintain function and independence, and improve quality of life. (Campbell)
Epidemiology and Presentation
Most bone metastases come from breast and prostate, then lung, kidney, thyroid and gastrointestinal primaries. In metastases of unknown origin the most common primaries are lung and kidney.
With a prior carcinoma, even remote, a new bone lesion is most likely a metastasis. In anyone over 40, a new aggressive-appearing bone lesion is most likely metastatic carcinoma or myeloma.
Once metastatic carcinoma is confirmed, later bone metastases can be treated without biopsy.
Imaging patterns: lesions may be lytic, blastic or mixed. Prostate is typically blastic and breast typically lytic; kidney and thyroid are usually purely lytic; lung may be mixed. A lesion distal to the elbow or knee is most likely lung in origin, and lung metastasis may show a "bite" out of the cortex.
(Campbell)
Work-up of a Lesion of Unknown Origin (Campbell's Concepts)
A proper work-up identifies the primary in over 85% of patients.
History and examination (including breast and prostate), basic labs with serum protein electrophoresis and, in men, PSA.
Radiographs of the entire involved bone and the chest, bone scan, and CT of chest, abdomen and pelvis.
Biopsy only after the work-up is complete. Even with a known carcinoma, biopsy the first bone lesion to confirm the relationship. Biopsy it as a suspected primary sarcoma, because it may prove to be a sarcoma or a different malignancy. In one case a presumed breast metastasis in the femoral neck proved to be a malignant fibrous histiocytoma, and prophylactic fixation would have severely compromised the outcome.
Nonoperative and Adjunctive Treatment (Campbell)
Multimodal care: systemic cytotoxic therapy directed by the medical oncologist; hormonal manipulation for breast and prostate cancer; radioactive iodine for some thyroid cancers.
Bisphosphonates help prevent new lesions and slow existing ones by inhibiting osteoclastic resorption.
Most symptomatic metastases respond to radiation; kidney cancer is typically radioresistant. Multi-fraction radiation is preferred over single-fraction to reduce fracture risk.
Radiofrequency ablation and cryoablation are options for selected lesions.
Prophylactic Fixation of Impending Fractures
Suggested indications: pain unresponsive to radiation, lesion larger than 2.5 cm, destruction of more than 50% of the cortex, and avulsion of the lesser trochanter. No single criterion is absolute.
Mirels score (site, pain, lesion type, size, each scored 1 to 3): prophylactic fixation should be considered at a score of 8 or higher. Site: upper limb 1, lower limb 2, peritrochanteric 3. Pain: mild 1, moderate 2, functional 3. Lesion: blastic 1, mixed 2, lytic 3. Size: under one third of the cortex 1, one third to two thirds 2, over two thirds 3.
Principles: fixing an impending fracture is technically easier than fixing an actual fracture, and morbidity is lower.
(Campbell)
Surgical Principles
The fixation must be stable enough for immediate full weight bearing, so the patient is not subjected to prolonged rehabilitation with limited life expectancy, and durable enough to last years if the patient does well.
Debulk the tumor before internal fixation and fill the cavity with methacrylate to augment fixation.
Protect the entire bone with intramedullary fixation in most cases.
If that cannot give stability for immediate full weight bearing, consider resection and prosthetic reconstruction. Femoral neck lesions are candidates for hemiarthroplasty or total hip arthroplasty. Components are often cemented because the bone is usually irradiated, although modern press-fit implants (especially trabecular metal) appear to obtain adequate fixation. Use a long-stem hemiarthroplasty only when additional distal lesions exist.
Acetabular lesions: curettage, supplemental screws and cement, and an acetabular cage with a cemented cup; consider preoperative embolization to limit blood loss (for example in lung or renal metastases).
Metaphyseal lesions: curettage, plate fixation and cement packing allows immediate ambulation.
An isolated kidney cancer metastasis can be treated with curative intent by wide resection and reconstruction.
(Campbell)
Postoperative Care
Radiation to the whole operative field is usually started 2 to 3 weeks after surgery if the wound has healed. Because of the patients' medical condition, the extent of surgery, and chemotherapy and radiation, infection risk is relatively high; consider a prolonged course of postoperative antibiotics, though protocols need further study. (Campbell)
Prognosis
Survival is unpredictable. Most patients with pathologic fracture from lung cancer die within 6 months, but some live 4 to 5 years with good quality of life. Breast, prostate and kidney patients commonly survive many years after bone metastases are diagnosed. (Campbell)
References
Toy PC, Heck RK Jr. Malignant tumors of bone. In: Azar FM, Sawyer JR, Throckmorton TW, eds. Campbell's Operative Orthopaedics. 15th ed. Philadelphia: Elsevier; 2026. Chapter 29, Metastatic carcinoma.