Prophylactic Fixation of Metastatic Bone Disease (Impending Fracture)

Indication. A patient with known cancer (or a newly found destructive bone lesion) who has an impending pathological fracture — a metastatic deposit in a weight-bearing or functionally critical bone that is at high risk of breaking through with routine activity. The hallmark is mechanical or functional pain (pain on weight-bearing that is relieved by rest, or night pain), combined with radiographic cortical destruction. The aim of operating BEFORE the bone breaks is to preserve mobility, relieve pain, shorten hospital stay and reduce the morbidity that follows a completed fracture. Assess the patient, not just the radiograph. Before committing to surgery, define:

• The primary tumour and its expected biology — breast and prostate are often responsive to hormones and radiotherapy; renal cell and thyroid are vascular and (renal especially) radioresistant; lung and melanoma imply a short prognosis.
• The patient's overall prognosis and performance status — this must justify the operation. Fix for a patient with a reasonable life expectancy; for someone with a prognosis of only weeks, prioritise comfort and radiotherapy.
• The whole bone on imaging (plain radiograph of the entire bone plus CT to assess cortical detail), and stage the skeleton (a whole-body bone scan or, increasingly, a PSMA or FDG PET-CT) — metastatic disease is multifocal and a second lesion may sit just beyond your planned implant. The key decision — the Mirels score. Score the lesion on four variables (site, pain, lesion type, size relative to bone diameter), each one to three points (detailed in Background). A total of 9 or more is the threshold for prophylactic fixation; a score of 8 is borderline and individualised, and 7 or less is treated with radiotherapy and systemic therapy. For a femoral neck lesion specifically, axial cortical involvement of about 30 mm or more, or circumferential involvement of about 50 percent, independently predicts fracture and reinforces the decision. The fixation-versus-resection choice. Having decided to operate, choose the construct that matches the destruction:

Consent specifically for blood loss and transfusion (higher in vascular metastases), tumour seeding, infection and wound breakdown (the immunosuppressed, irradiated cancer patient is high risk), the possibility of progression and the need for adjuvant radiotherapy and systemic therapy, and a frank discussion of prognosis. Setup. Supine on a radiolucent table (or a fracture table) with the limb free; general or regional anaesthesia with invasive monitoring and large-bore access for the vascular cases. Cross-match blood, and for renal or thyroid metastases confirm that pre-operative embolisation was performed 24 to 48 hours beforehand. Set up the C-arm for AP and lateral fluoroscopy of the entire bone BEFORE draping. Prophylactic antibiotics and venous thromboembolism prophylaxis are essential.

The goal: stabilise the impending fracture so the bone will not break, splint the entire bone, restore the structural void with cement where needed, and do so with minimal blood loss — then hand the patient on to radiotherapy and systemic therapy. The canonical case below is the proximal femoral impending fracture stabilised with a long cephalomedullary nail; the same principles apply to the humerus (antegrade nail or long locking plate) and other long bones.

Rehabilitation | Phase | Timing | Weight-bearing | Focus | |-------|--------|----------------|-------| | 1 | 0 to 2 weeks | Protected, as comfort allows (nail is load-bearing) | Pain control, wound care, mobilise | | 2 | 2 to 6 weeks | Progress to full | Radiotherapy to the whole construct; start systemic therapy | | 3 | 6 to 12 weeks | Full | Therapy for adjacent joints; function for remaining life | The goal of prophylactic fixation is comfort and mobility for the patient's remaining life, not bony union — the tumour and the radiation will not heal the bone, so the implant carries the load permanently. Most patients are up walking within a day or two. Complications

Epidemiology. Bone is the third most common site of metastasis after lung and liver. The tumours that most often spread to bone are breast, prostate, lung, renal and thyroid (and multiple myeloma behaves similarly). The femur is the most common long-bone site — typically in the intertrochanteric and subtrochanteric regions — followed by the humerus. A pathological fracture or an impending fracture is a skeletal-related event, and these events carry both a quality-of-life and a survival signal; preventing them is the point of prophylactic fixation. Pathoanatomy. Metastases weaken bone by disturbing the normal remodelling balance. Lytic lesions (breast, lung, renal, thyroid, myeloma) drive osteoclast-mediated resorption that erodes the cortex; blastic lesions (prostate, some breast) lay down disorganised new bone that is strong in compression but still brittle. Either way, as cortical destruction advances the bone fails under physiological load — in bending through the diaphysis, or in compression and torsion at the metaphysis. The risk rises with the axial length of cortical involvement and with circumferential destruction. The Mirels score remains the standard bedside tool for predicting fracture risk.

The total ranges from 4 to 12. A score of 9 or more carries a roughly one-in-three risk of fracture and is the accepted threshold for prophylactic fixation; a score of 8 or less is managed with radiotherapy and systemic therapy. For the femoral neck specifically, the Dutch Bone Metastasis Study showed that axial cortical involvement of about 30 mm or more, or circumferential cortical involvement of about 50 percent or more, independently predicts fracture and is a useful adjunct when the Mirels score is borderline. Bone-targeted systemic therapy rounds out the pathway. Both bisphosphonates (zoledronic acid) and denosumab (a RANKL inhibitor) reduce skeletal-related events — pathological fracture, spinal cord compression and the need for radiotherapy or surgery — and are part of the standard care of bone metastasis alongside the local fixation.