Pathologic fractures occur through bone weakened by underlying disease, most commonly metastatic carcinoma (breast, lung, prostate, renal, thyroid) or multiple myeloma. The Mirels' scoring system (site, pain, lesion type, size) guides prophylactic fixation decisions - a score ≥9 indicates high fracture risk warranting stabilization. The principle of biopsy before fixation applies unless the primary tumor is known with certainty. Reconstruction choice depends on expected survival: short survival favours load-sharing devices (IM nails, endoprostheses), while longer survival may warrant more durable reconstructions. Lytic lesions in the femur (especially peritrochanteric) carry highest fracture risk.

Bone Weakening Mechanisms

History Components

Pain Characterization:

• Onset: Gradual vs sudden (fracture event)
• Duration: Weeks to months of preceding pain typical
• Character: Dull, aching, progressive
• Timing: Night pain suggests tumor
• Relieving factors: Activity modification, NSAIDs often ineffective
• Red flag symptoms: Fever, night sweats, weight loss, anorexia

Mechanism of Injury:

• Detailed mechanism assessment critical
• "Twisted getting out of chair" or "stepping off curb" suggests pathologic
• High-energy trauma can occur through pathologic bone (confounding)
• Pain before the fall indicates pre-existing pathology
• Multiple witnesses may clarify mechanism

Medical History:

• Current or previous malignancy (type, stage, treatments)
• Radiation therapy to bone (radiation-induced fractures)
• Prolonged corticosteroid use (osteoporosis, osteonecrosis)
• Metabolic bone disease history
• Previous fractures (pattern recognition)
• Family history (hereditary bone disorders)

Functional Impact:

• Pre-fracture ambulatory status
• Weight-bearing ability
• Pain limiting function
• Social support and home environment
• Goals and expectations (align with prognosis)

Physical Examination

Inspection:

• Swelling, ecchymosis (may be disproportionate)
• Deformity, limb shortening, rotation
• Previous surgical scars (biopsy sites)
• Skin changes (radiation, infection, tumor ulceration)
• Muscle wasting (chronic pain, denervation)

Palpation:

• Point tenderness over fracture site
• Palpable mass or cortical defect
• Temperature (infection, inflammation)
• Crepitus with gentle range of motion
• Proximal and distal joint examination

Neurovascular Examination:

• Pulse assessment (ABI if concern)
• Capillary refill
• Sensory examination (nerve compression or injury)
• Motor function (avoid stressing fracture)
• Document findings precisely (medicolegal, surgical planning)

Systematic Survey:

• Spine palpation and percussion
• Pelvis compression and distraction
• Contralateral limb examination
• Abdominal examination (organomegaly)
• Chest auscultation (lung metastases)

The examination should identify fracture complications while gathering clues to underlying diagnosis without causing additional patient discomfort or fracture displacement.

Imaging Modalities

Biopsy Principles

Non-Operative Management

Surgical Management

Prognostic Factors

Primary Tumor Type (Most Important):

Favorable Prognosis (Median Survival greater than 12 Months):

• Breast cancer (especially hormone receptor positive)
• Prostate cancer
• Thyroid cancer (follicular)
• Multiple myeloma
• Renal cell carcinoma (selected patients)

Intermediate Prognosis (6-12 Months):

• Renal cell carcinoma
• Colorectal cancer
• Melanoma
• Unknown primary

Poor Prognosis (Less than 6 Months):

• Lung cancer (especially small cell)
• Pancreatic cancer
• Gastric cancer
• Hepatocellular carcinoma

Burden of Disease:

• Solitary skeletal metastasis: better prognosis
• Multiple skeletal sites: intermediate
• Visceral metastases present: poor prognosis
• Spinal cord compression: worse outcomes
• Hypercalcemia: poor prognostic sign

Performance Status:

• Ambulatory, independent: better survival and quality of life
• Requires assistance: intermediate
• Bedridden: poor prognosis, limited benefit from surgery

Laboratory Markers:

• Elevated alkaline phosphatase: worse prognosis
• Anemia: associated with reduced survival
• Hypoalbuminemia: malnutrition, poor outcomes
• Hypercalcemia: advanced disease

Functional Outcomes

Expected Functional Recovery:

Lower Extremity Fractures:

• 75-85% regain ambulatory status
• Median time to weight-bearing: 3-7 days
• Ambulation level may not return to baseline
• Walking aids often required
• Rehabilitation limited by systemic disease progression

Upper Extremity Fractures:

• Greater than 90% achieve functional use
• Earlier return to activities of daily living
• Pain relief more consistent
• Better overall satisfaction

Quality of Life Improvements:

• Pain reduction (most consistent benefit)
• Independence in activities of daily living
• Psychological benefit (sense of control)
• Reduced caregiver burden
• Ability to receive oncologic treatments
• Facilitation of hospice care at home vs hospital

Factors Limiting Recovery:

• Disease progression (new metastases, visceral involvement)
• Complications (infection, nonunion, implant failure)
• Deconditioning during recovery
• Chemotherapy side effects
• Depression and anxiety
• Inadequate social support

Survival Data by Treatment

Key Insights:

• Surgery does not prolong survival (systemic disease determines longevity)
• Surgery dramatically improves quality of life metrics
• Functional outcomes justify surgical morbidity in appropriate candidates
• Patient selection critical (avoid surgery in moribund patients)
• Goals: palliation, function, independence - not cure

The evidence supports surgical stabilization for functional restoration and quality of life, even in patients with limited prognosis, provided they are medically fit for anesthesia.

Pelvic & Acetabular Lesions

Spine Metastases with Pathologic Fracture

Spinal Instability Neoplastic Score (SINS):

Predicts spinal instability in metastatic disease (score 0-18):

Components:

1. Location (junctional vs non-junctional)
2. Pain (mechanical vs positional vs none)
3. Bone lesion (lytic vs mixed vs blastic)
4. Spinal alignment (subluxation, kyphosis, scoliosis)
5. Vertebral body collapse (greater than 50%, less than 50%, none)
6. Posterolateral involvement (bilateral, unilateral, none)

Score Interpretation:

• 0-6: Stable (radiation ± chemotherapy)
• 7-12: Potentially unstable (individualized decision)
• 13-18: Unstable (surgical stabilization indicated)

Surgical Indications:

• Spinal instability (SINS greater than or equal to 13)
• Neurologic deficit (cord compression, radiculopathy)
• Intractable pain despite radiation
• Radioresistant tumor
• Tissue diagnosis needed

Surgical Options:

Decompression + Instrumented Fusion:

• Relieves neural compression
• Provides immediate stability
• Allows early mobilization
• Does not address anterior column destruction (may fail)

Separation Surgery + Stereotactic Radiation:

• Minimal decompression (create space for radiation)
• Short-segment stabilization
• High-dose focused radiation post-op
• Emerging paradigm for radiosensitive tumors

Vertebroplasty/Kyphoplasty:

• Compression fractures without instability or cord compression
• Cement stabilization
• Pain relief in 70-90%
• Complications: cement leak, neural injury (rare)

Corpectomy + Reconstruction:

• Anterior column structural support
• Expandable cage or cement
• Combined with posterior stabilization
• Major surgery, reserved for longer survival expected

Spine pathologic fractures require neurosurgical or spine surgery expertise with oncology multidisciplinary team involvement.

Pediatric Pathologic Fractures

Unique Considerations:

Etiology Differences:

• Benign lesions more common (unicameral bone cyst, fibrous dysplasia, enchondroma)
• Primary malignant tumors (osteosarcoma, Ewing sarcoma) vs metastatic
• Langerhan cell histiocytosis
• Leukemia/lymphoma

Growth Considerations:

• Avoid physeal injury if possible
• Limb-length discrepancy potential
• Remodeling potential greater than adults
• Long-term implant effects

Management Principles:

Benign Lesions:

• Many heal spontaneously after fracture (unicameral bone cyst 15%)
• Initial treatment: fracture immobilization
• Definitive treatment after healing (curettage, grafting)
• Avoid unnecessary surgery during acute phase

Malignant Lesions:

• Multimodal treatment (chemotherapy + surgery ± radiation)
• Limb salvage preferred when feasible
• Physeal-sparing techniques when possible
• Expandable prostheses for young children (accommodate growth)

The pediatric population requires subspecialty expertise with different treatment paradigms focused on cure and long-term function.

The first task when a fracture looks pathologic is deciding what the bone is made of. Confusing a primary sarcoma for a metastasis - and nailing it - is the single most damaging error in this topic. The table below frames the differential the way examiners probe it.

• Mirels threshold for prophylactic fixation. A score of 9 or more is the classic cut-off, but the score is sensitive and poorly specific, so it over-predicts fracture and may lead to over-treatment. There is growing interest in CT-based structural metrics (axial cortical involvement greater than 30 mm, circumferential cortical destruction) and CT-based finite-element ("rigidity") analysis as more specific predictors, though none has displaced Mirels in routine practice.
• Biopsy before fixation in the "obvious" metastasis. When widely metastatic disease is established and the lesion is typical, many surgeons proceed to stabilisation with intra-operative sampling. The counter-argument is that solitary or atypical lesions in a cancer survivor occasionally turn out to be a second primary or sarcoma; the safe default in any doubt is biopsy first.
• Endoprosthesis versus intramedullary nailing for the proximal femur. Registry and cohort data show endoprostheses fail far less often than ORIF and somewhat less than nails, but they are bigger operations with higher early dislocation and infection risk. The decision hinges on expected survival, extent of bone loss and joint involvement rather than a single rule.
• Separation surgery plus SBRT versus aggressive decompression for the spine. The Patchell trial established surgery plus conventional radiotherapy for cord compression, but the modern paradigm increasingly favours minimal "separation" surgery followed by high-dose stereotactic radiotherapy, especially for radioresistant tumours - access to SBRT drives this variation.
• Role and duration of bone-modifying agents. Bisphosphonates and denosumab reduce skeletal-related events, but optimal agent, dosing interval and how to manage rebound hypercalcaemia after stopping denosumab remain debated, as does their role around the time of surgery.
• Cemented intramedullary augmentation. Cement improves immediate fixation and adds a tumoricidal thermal effect, but extravasation, embolism and the loss of future MRI surveillance are real trade-offs; routine versus selective use is not standardised.

Global Epidemiology

• Bone is the third most common site of metastasis after lung and liver; skeletal metastases develop in 30-40% of patients with advanced solid-organ cancer.
• The five carcinomas that account for the great majority of bone metastases are breast, prostate, lung, kidney and thyroid (mnemonic "BLT with Kosher Pickle"). Breast and prostate dominate because of their high prevalence and prolonged survival.
• Multiple myeloma is the commonest primary malignancy of bone and a major cause of pathologic fracture, with bone involvement in the majority at diagnosis.
• Roughly one in five patients with symptomatic skeletal metastases will require surgery for a skeletal complication during their disease course.
• An ageing global population and improving systemic cancer survival are increasing the prevalence of metastatic bone disease and the lifetime burden of pathologic fracture.

Side-by-Side Guideline Comparison

Where guidance genuinely converges, it is on three principles: obtain a diagnosis before instrumenting any indeterminate lesion, manage through a multidisciplinary team, and build a durable, immediately weight-bearing construct because biological union is not expected. Divergence is mostly about thresholds and pathways (e.g. NICE mandates 24-hour timelines for cord compression that other bodies state only as principle).

Registry and Outcome Evidence

• National arthroplasty registries (NJR for England/Wales, AOANJRR in Australia, the Swedish SHAR, the Norwegian and New Zealand registries) increasingly capture tumour/oncology endoprostheses, informing revision and infection rates for megaprostheses used in periarticular metastatic disease.
• Dedicated bone-tumour databases such as the Scandinavian Sarcoma Group registry generated much of the implant-failure data above (e.g. higher failure of plating versus nailing in the humerus, and of osteosynthesis versus endoprosthesis in good-prognosis patients).
• Registry signals consistently show that long expected survival is the dominant risk factor for construct failure, reinforcing prognosis-matched reconstruction.

High- vs Limited-Resource Practice Variation

• Well-resourced settings: ready access to MRI/PET-CT staging, image-guided core biopsy, modular tumour prostheses, custom 3D-printed implants, preoperative embolisation for hypervascular tumours, and stereotactic body radiotherapy (SBRT) enabling "separation surgery" for the spine.
• Limited-resource settings: diagnosis may rest on plain radiographs and clinical judgement; intramedullary nailing with cement is often the workhorse because megaprostheses and SBRT are unavailable; embolisation and on-table cell salvage may be inaccessible, raising the threshold for operating on hypervascular renal/thyroid lesions; non-operative palliation with conventional radiotherapy carries greater weight.
• Across all settings the exam-relevant principles are identical - the trade-offs change with available technology and realistic prognosis, not the underlying decision logic.