Pathological Fracture

A pathological fracture occurs through bone weakened by disease rather than through otherwise normal bone exposed to sufficient traumatic force.

Important causes include:

Malignant

• Bone metastases
• Multiple myeloma
• Primary malignant bone tumour

Benign tumour or tumour like lesion

• Giant cell tumour
• Unicameral bone cyst
• Aneurysmal bone cyst
• Fibrous dysplasia

Metabolic or structural

• Osteoporosis
• Osteomalacia
• Hyperparathyroidism
• Paget disease
• Osteogenesis imperfecta
• Chronic infection

In an adult with a destructive lesion, metastatic malignancy and myeloma must be considered until excluded.

A critical oncological principle is:

Do not internally fix an unexplained pathological fracture before appropriate staging and biopsy planning.

An incorrectly placed nail or plate through a primary sarcoma can contaminate the entire limb and convert a potentially limb salvageable tumour into one requiring much more extensive surgery.

Mirels score for impending metastatic long bone fracture

Mirels assesses four variables, each scored 1 to 3.

Site

• Upper limb = 1
• Lower limb = 2
• Peritrochanteric = 3

Pain

• Mild = 1
• Moderate = 2
• Functional pain = 3

Lesion type

• Blastic = 1
• Mixed = 2
• Lytic = 3

Size relative to bone diameter

• Less than one third = 1
• One third to two thirds = 2
• More than two thirds = 3

Total score: 4 to 12

Interpretation for lower extremity metastatic lesions:

• 7 or less: relatively low fracture risk
• 8: borderline, individual judgement
• 9 or greater: strong consideration for prophylactic stabilisation

Functional pain, large lytic lesions and peritrochanteric location are particularly concerning. Mirels has limitations and should supplement rather than replace assessment of cortical destruction and CT based structural risk.

The fracture may occur after minor trauma or normal activity.

Ask specifically about pain before the fracture. Progressive night pain or functional pain preceding a low energy fracture strongly suggests underlying bone disease.

Look for:

• Previous malignancy
• Unexplained weight loss
• Night sweats
• Anaemia
• Hypercalcaemia symptoms
• Multiple painful skeletal sites
• Previous radiation
• Long term metabolic bone disease

Examine the whole limb rather than only the fracture.

Before biopsy or definitive fixation of an unexplained lesion:

Plain radiographs of the entire affected bone: determine lesion morphology and look for additional lesions.

Characterise:

• Lytic versus blastic
• Geographic versus permeative destruction
• Cortical destruction
• Periosteal reaction
• Soft tissue mass

Obtain staging investigations according to presentation, commonly including:

• Full blood count
• Renal function
• Calcium
• Phosphate
• Alkaline phosphatase
• Liver function
• Serum protein electrophoresis and free light chains when myeloma is possible
• Disease specific tumour markers where clinically justified

CT chest, abdomen and pelvis: search for a primary carcinoma and metastatic disease.

MRI of the affected region is important when a primary bone tumour is possible because it defines local medullary and soft tissue extent.

Biopsy should occur after staging, with the biopsy trajectory planned by the team that would perform definitive tumour surgery.

Known metastatic disease

Treat pain, stabilise the fracture and treat the underlying malignancy.

Fixation should be sufficiently durable to function for the patient\'s remaining lifetime. Metastatic fractures often have limited biological healing potential, so the construct should not depend on union before it becomes mechanically reliable.

Impending fracture

Prophylactic fixation is usually preferable to waiting for a completed fracture because surgery is technically easier and rehabilitation is faster.

Consider prophylactic stabilisation particularly with:

• Mirels score at least 9 in the lower limb
• Functional mechanical pain
• Extensive cortical destruction
• Large peritrochanteric lesion
• Progressive lesion despite oncological treatment

Completed femoral pathological fracture

Treatment depends on location and remaining bone stock.

Femoral neck: arthroplasty is usually preferred because internal fixation through pathological femoral neck bone has poor reliability.

Peritrochanteric or subtrochanteric region: long cephalomedullary fixation can provide durable load sharing when adequate proximal bone remains.

Extensive proximal femoral destruction: proximal femoral replacement may be preferable.

Femoral shaft: intramedullary fixation commonly spans most or all of the diseased femur.

Distal periarticular destruction: locked fixation, cement augmentation or distal femoral replacement may be appropriate depending on remaining bone.

Cement augmentation can provide immediate mechanical support in extensive metastatic defects.

Primary bone tumour

If the fracture occurs through a suspected primary sarcoma, immobilise and refer to orthopaedic oncology before definitive fixation.

Pathological fracture does not automatically preclude limb salvage, but tumour contamination from inappropriate initial surgery can.

Postoperative oncological treatment

Metastatic lesions frequently require postoperative radiotherapy after wound healing to improve local tumour control and reduce progression around fixation.

Systemic anticancer therapy continues according to tumour biology.