An impending pathological fracture · Mirels 9 or more
- Prophylactic fixation is for an IMPENDING pathological fracture — a bone containing metastatic disease that has not yet broken but is at high risk. The decision rests on the Mirels score: a score of 9 or more predicts roughly a one-in-three fracture risk and is the threshold to fix, while a score of 8 or less is managed with radiotherapy and systemic therapy.
- Fix the WHOLE bone. Metastatic disease is multifocal, so a short device or a plate over only the lesion invites a fracture at the tip of the implant or at a second site. For the proximal femur this means a long cephalomedullary nail spanning from the femoral head to the distal metaphysis.
- Pre-operatively embolise vascular metastases — renal cell and thyroid — within 24 to 48 hours of surgery, otherwise intra-operative blood loss can be torrential.
- If there is no known primary, BIOPSY first, along the line of any future resection: a primary sarcoma changes everything about the implant and the plan.
- Plan post-operative radiotherapy to the entire length of the construct and start bone-targeted systemic therapy (a bisphosphonate or denosumab).
- Reserve endoprosthetic reconstruction for a bone too destroyed to hold a nail or plate (a complete cortical ring gone), or for a solitary, radioresistant lesion such as renal cell carcinoma where survival is measured in years.
When & Why
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 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:
A long cephalomedullary nail (proximal femur) or a long locked nail splints the WHOLE bone, load-shares, and allows immediate weight-bearing. The evidence-based default for most diaphyseal and peri-trochanteric impending fractures.
For a juxta-articular lesion that a nail cannot reach (e.g. a distal femoral or proximal tibial metaphysis), a locking plate augmented with PMMA cement fills the lytic void and buttresses the cortex.
When the cortical ring is completely destroyed or the lesion is a solitary, radioresistant metastasis (e.g. renal cell), an endoprosthesis (megaprosthesis) removes the tumour and gives durable, immediate stability. See the endoprosthetic reconstruction page.
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 Operation
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.
AP radiograph of the proximal femur showing a large lytic metastatic deposit in the intertrochanteric region with cortical thinning, alongside the post-operative image of a long cephalomedullary nail with a lag screw into the femoral head spanning the full femur.
Context: A verified image is being sourced.
Operative sequence
- Supine on a radiolucent table with a bump under the ipsilateral buttock; the whole limb is prepped and draped free.
- Confirm the C-arm images the entire femur in AP and lateral before draping — the head and neck, the lesion, the diaphysis and the distal metaphysis must all be visible in both planes.
- For renal or thyroid metastases, confirm embolisation was completed 24 to 48 hours ago.
- A 3 to 5 cm longitudinal incision over the proximal greater trochanter, extending proximally from the trochanteric tip.
- Split the gluteus medius and minimus fibres in line with the incision down to the trochanteric tip — a small, internervous (superior gluteal nerve) interval.
- The superior gluteal nerve runs about 5 cm above the greater trochanter: stay distal to it. No major vessel or tendon is crossed.
- If there is no known primary, take tissue for histology and microbiology BEFORE definitive fixation, through a tract along the line of any future resection.
- Send fresh tissue — a primary sarcoma, lymphoma or infection changes the implant and the entire plan. Do not commit to a nail across an unbiopsied destructive lesion.
- Open the trochanteric tip (or the piriformis fossa, per the device) and seat the entry reamer.
- Pass the guidewire into the femoral head, confirmed on AP and lateral fluoroscopy to be central and deep within the head and neck. Correct any collapse or angulation at the lesion.
- Ream the canal with flexible reamers, passing across the metastatic defect, to a diameter about 1 to 1.5 mm larger than the selected nail.
- Reaming opens the whole canal and the reamings decompress tumour, but over-reaming risks fat embolism and bleeding — ream slowly and only as much as is needed to pass a long nail.
- Pass a long nail spanning from the femoral head to the distal metaphysis — the whole bone.
- Place the lag screw (or blade) into the femoral head and neck over the guidewire, controlling the neck and intertrochanteric region. This single construct now bridges the femoral neck, the trochanters and the diaphysis.
- For a large lytic void, inject PMMA (polymethylmethacrylate) around the screw and nail to restore structural continuity and lock the construct.
- Fill the defect but do not overpressurise. Cement augmentation is most useful where tumour has destroyed the load-bearing cortex.
- Insert the distal static locking screw or screws.
- Image the entire femur in both planes and confirm the nail bridges the full length, the head screw is central, and there is no second lesion at risk beyond the tip of the implant.
- Wash, achieve haemostasis, and close in layers.
- The construct is load-bearing: mobilise with protected weight-bearing as comfort allows.
- Book post-operative radiotherapy to the whole construct and start (or continue) bone-targeted systemic therapy.
Renal cell, thyroid, and occasionally hepatocellular and melanoma metastases are highly vascular. Without pre-operative arterial embolisation, intra-operative blood loss can be torrential and uncontrollable. Arrange embolisation within 24 to 48 hours of surgery, cross-match blood, use large-bore access and invasive monitoring, and be prepared for a hypotensive, transfusion-heavy case. If bleeding is encountered from an un-embolised vascular lesion, pack, call for help, and control the feeding vessels.
The nail must span from the femoral head to the distal metaphysis. A short nail or a dynamic hip screw addresses only the intertrochanteric region, so a second lesion — or the tip of the implant — will fracture next, often within months. The same whole-bone logic applies to the humerus (a long antegrade nail or a long locking plate).
A plate load-shares only the bone immediately beneath it and concentrates stress at its ends, so a lytic diaphyseal metastasis plated in isolation will fracture at the plate tip. For diaphyseal disease use an intramedullary nail, which load-shares the entire bone, and reserve a plate for juxta-articular lesions a nail cannot reach.
Aftercare & Complications
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
| Complication | Recognition | Prevention | Management |
|---|---|---|---|
| Intra-operative haemorrhage (vascular metastasis) | Torrential bleeding on entry; haemodynamic instability | Pre-op embolisation of renal/thyroid mets 24 to 48 hours prior; cross-match, large-bore access | Pack, control feeding vessels, transfuse, call interventional radiology |
| Fat embolism syndrome | Hypoxia, confusion, petechial rash in the first 24 to 48 hours | Ream slowly and only as much as needed; avoid over-reaming; consider venting | Supportive — high-flow oxygen, ITU, resuscitation |
| Screw or nail cut-out | Loss of fixation, shortening, pain on the table or early post-op | Central guidewire placement; correct entry point; cement augmentation of the head/neck | Revise — reposition the screw or convert to an endoprosthesis |
| Fracture at the nail tip or a second site | New pain and a peri-implant fracture line on radiograph | Fix the WHOLE bone; image the entire skeleton pre-op; radiotherapy to the construct | Revise to a longer construct or an endoprosthesis |
| Wound infection or breakdown | Erythema, discharge, dehiscence in an irradiated, immunosuppressed patient | Prophylactic antibiotics; meticulous handling; avoid operating through irradiated skin where possible | Debridement, antibiotics, plastic cover if needed |
| Venous thromboembolism | Calf pain, swelling, dyspnoea — cancer is a high-risk state | Mechanical and pharmacological thromboprophylaxis | Anticoagulation; investigate for PE |
| Disease progression / non-union | Persistent pain, advancing lysis on serial imaging | Radiotherapy to the whole construct; systemic bone-targeted therapy | Systemic therapy review; revision to endoprosthesis if fixation fails |
Viva & Exam Focus
MIRELSMIRELS — the prophylactic-fixation checklist
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“A 68-year-old woman with metastatic breast cancer has a lytic lesion in her proximal femur and pain on weight-bearing. How do you decide whether to fix it prophylactically?”
“A 55-year-old with a solitary renal cell carcinoma metastasis destroying the proximal femoral metaphysis. Would you fix it or reconstruct it?”
Indication & scoring
- Impending pathological fracture — mechanical/functional pain with cortical destruction
- Mirels score: 9 or more fix, 8 or less radiotherapy
- Femoral neck: axial cortical involvement about 30 mm or circumferential about 50 percent reinforces the decision
Whole-bone principle
- Long cephalomedullary nail, femoral head to distal metaphysis
- Never plate a diaphyseal metastasis in isolation
- Image the whole bone and skeleton pre-operatively
Vascular metastases
- Renal cell and thyroid — embolise 24 to 48 hours pre-op
- Cross-match blood, large-bore access, invasive monitoring
Adjuvant therapy
- Radiotherapy to the entire construct
- Bisphosphonate or denosumab to reduce skeletal-related events
Endoprosthesis vs fixation
- Fixation default for most impending fractures
- Endoprosthesis when the cortical ring is gone or the lesion is a solitary radioresistant (renal) metastasis
- Biopsy first if the primary is unknown
Background & Evidence
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.
| Variable | 1 point | 2 points | 3 points |
|---|---|---|---|
| Site | Upper limb | Lower limb | Peritrochanteric |
| Pain | Mild | Moderate | Functional (mechanical) |
| Lesion type | Blastic | Mixed | Lytic |
| Size (of bone diameter) | Less than one third | One third to two thirds | Greater than two thirds |
References
Metastatic disease in long bones — a proposed scoring system
- Proposed the four-variable (site, pain, lesion type, size) scoring system for impending pathological fractures
- A score of 9 or more identified lesions at high risk of fracture, establishing the operative threshold still in use
Radiographic predictors of fracturing in metastatic femoral lesions
- In femoral metastases, axial cortical involvement and circumferential extent best predicted fracture
- Axial involvement of about 30 mm or more, or circumferential involvement of about 50 percent or more, indicated high risk
Denosumab compared with zoledronic acid for bone metastases
- Randomised trial in patients with bone metastases from breast cancer
- Denosumab was superior to zoledronic acid in delaying the first on-study skeletal-related event
Zoledronic acid versus placebo for skeletal metastases in solid tumours
- Randomised trial in patients with bone metastases from lung cancer and other solid tumours
- Zoledronic acid reduced the proportion of patients with a skeletal-related event and delayed its onset versus placebo