Metastatic Bone Disease

1. Clinical Overview

Summary

Metastatic bone disease represents the third most common site of cancer metastasis after lung and liver, occurring when malignant cells from distant primary tumours colonize the skeletal system via haematogenous spread. [1] This devastating complication marks the transition to Stage IV disease and affects quality of life through pain, fractures, spinal cord compression, and hypercalcaemia - collectively termed Skeletal Related Events (SREs). [2]

The "Big 5" primary carcinomas responsible for over 80% of bone metastases are Breast, Prostate, Lung, Kidney (Renal), and Thyroid - remembered by the mnemonic "Pb KTL" (Lead Kettle). [3] Bone metastases are classified by their radiographic appearance as Lytic (destructive), Blastic (sclerotic), or Mixed, reflecting the underlying tumour biology and bone remodelling dynamics. [4]

The primary goals of management are multifaceted: palliation of pain, prevention of SREs (particularly pathological fractures and malignant spinal cord compression), preservation of mobility and independence, and optimization of quality of life in the context of advanced malignancy. [5] Prophylactic surgical fixation of impending fractures, guided by validated scoring systems such as Mirels' Score, significantly improves functional outcomes compared to fixation of completed fractures and should be pursued aggressively when indicated. [6]

Key Epidemiological Facts

• Prevalence: Autopsy studies demonstrate that 70% of patients dying from breast or prostate cancer have skeletal involvement, though many lesions remain asymptomatic during life. [7]
• Site Predilection: The axial skeleton is preferentially affected - spine (> 50% of cases), pelvis (30%), and proximal long bones including femur and humerus (20%) - reflecting the distribution of red haematopoietic marrow in adults. [8]
• Mechanism of Spread: Haematogenous dissemination via Batson's Valveless Venous Plexus, a low-pressure venous network connecting pelvic and vertebral veins, explains the high frequency of spinal metastases independent of cardiac output. [9]
• Impact on Survival: A completed pathological fracture reduces median survival by approximately 50% compared to age- and stage-matched controls without fracture, attributable to immobility, surgical stress, and thromboembolic complications. [10]

The "Big 5" Primary Sources (Detailed)

1. Breast Carcinoma

• Frequency: 65-75% of patients with advanced breast cancer develop bone metastases during disease course. [11]
• Radiographic Type: Mixed (both lytic and blastic features).
• Biology: Oestrogen receptor (ER) and progesterone receptor (PR) positive tumours demonstrate better prognosis and respond to endocrine therapy (Tamoxifen, Aromatase Inhibitors). HER2-positive disease responds to targeted therapy (Trastuzumab).
• Preferred Sites: Thoracic spine, ribs, sternum, pelvis.
• Survival: Median survival with bone-only metastases 24-36 months. [12]

2. Prostate Carcinoma

• Frequency: Up to 90% of men dying from prostate cancer have skeletal metastases. [13]
• Radiographic Type: Predominantly osteoblastic (sclerotic) - "ivory vertebra" or "cotton wool" appearance on radiographs.
• Mechanism: Prostate-specific antigen (PSA) and Endothelin-1 drive pathological osteoblast activation, producing mechanically inferior woven bone.
• Preferred Sites: Lumbar spine (via Batson's plexus), pelvis, proximal femur.
• Markers: Elevated PSA (often > 100 ng/mL), raised alkaline phosphatase.

3. Lung Carcinoma

• Frequency: 30-40% of patients with advanced lung cancer develop bone metastases. [14]
• Radiographic Type: Lytic (destructive). Highly aggressive biology.
• Patterns:
  • "Pancoast Tumour: Superior sulcus tumour invading ribs, brachial plexus, and sympathetic chain (Horner's syndrome)."
  • "Acrometastasis: Rare distal extremity metastases to hands/feet - lung is the most common primary."
• Prognosis: Median survival 3-6 months. Worst prognosis of the "Big 5". [15]

4. Renal Cell Carcinoma (RCC)

• Frequency: 20-25% develop bone metastases. [16]
• Radiographic Type: Lytic, expansile ("blow-out" lesion), hypervascular.
• Key Features: Pulsatile soft tissue mass. Extremely high risk of catastrophic intraoperative haemorrhage.
• Critical Management: Mandatory preoperative embolization within 24-48 hours of surgery to reduce vascularity. Failure to embolize can result in exsanguination. [17]

5. Thyroid Carcinoma

• Frequency: 10-15% of differentiated thyroid cancers metastasize to bone. [18]
• Radiographic Type: Lytic, hypervascular.
• Histology: Follicular carcinoma metastasizes to bone more frequently than papillary carcinoma.
• Management: Preoperative embolization recommended. Radioiodine therapy (I-131) for iodine-avid metastases.

Clinical Pearls

"Fix it BEFORE it breaks": Prophylactic intramedullary nailing of an impending femoral fracture (Mirels score ≥9) is an elective, minimally invasive, closed procedure with immediate full weight-bearing. Fixation of a completed pathological fracture is a bloody, technically demanding emergency operation with poor bone healing potential, higher complication rates, and prolonged rehabilitation. Be aggressive with prophylaxis. [6]

"The Renal Cell Trap": Renal Cell Carcinoma and Thyroid metastases are enormously vascular. Surgical instrumentation without preoperative angiographic embolization risks fatal exsanguination on the operating table. Always embolize hypervascular lesions 24-48 hours preoperatively. [17]

"Prostate turns it White, Lung makes it a Hole": On plain radiographs, prostate cancer metastases appear as sclerotic "cotton wool" or "snowball" densities. Lung cancer creates "moth-eaten" lytic destruction.

"The Biopsy Rule": In a patient > 40 years with a destructive bone lesion, assume metastasis until proven otherwise. Do NOT biopsy suspected metastatic bone disease as the first step. Perform CT Thorax-Abdomen-Pelvis (CT TAP) to identify the primary tumour first. Inadvertently biopsying a primary bone sarcoma through an inappropriate tract contaminates tissue planes and may necessitate amputation. [19]

"The Iceberg Effect": The radiographically visible lytic lesion represents only the "tip of the iceberg". Tumour infiltration extends far beyond the visible defect into the medullary canal. This is why long intramedullary nails spanning the entire bone (not just the visible lesion) are mandatory to prevent fracture at a secondary site. [20]

"The 50% Cortical Rule": When a lytic lesion destroys > 50% of the cortical diameter on any single radiographic view, the bone has lost approximately 90% of its torsional strength and is at imminent risk of fracture with minimal trauma. [6]

"The Radiotherapy NNT": The Number Needed to Treat (NNT) for radiotherapy to achieve complete pain relief in bone metastases is approximately 3-4. For partial pain relief, NNT approaches 1.5. It is one of the most effective palliative interventions in oncology. [21]

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2. Epidemiology

Incidence and Prevalence

Bone metastases represent a major cause of cancer-related morbidity:

• Overall Burden: Approximately 400,000 new cases of metastatic bone disease diagnosed annually in the United States alone. [1]
• Autopsy Studies: 70% of patients dying from breast or prostate carcinoma have histologically confirmed skeletal metastases, though many remain asymptomatic or undiagnosed clinically. [7]
• Clinical Detection: Only 30-40% of bone metastases are symptomatic or detected during life, suggesting substantial underdiagnosis in asymptomatic disease.

Survival by Primary Tumour Type

Prognosis varies dramatically based on primary histology: [22]

Risk Factors for Skeletal Related Events (SREs)

Multiple factors predict SRE development: [2]

1. Lesion Type: Lytic lesions carry 3-4x higher fracture risk than blastic lesions (mechanically weaker).
2. Anatomical Location:
   • Peritrochanteric femur (subtrochanteric and intertrochanteric regions) highest risk - weight-bearing stress concentration.
   • Femoral neck and shaft intermediate risk.
   • Upper limb (humerus) lower risk.
3. Functional Pain: Pain exacerbated by weight-bearing or loading is the most specific clinical predictor of impending fracture (sensitivity 89%, specificity 95%). [6]
4. Lesion Size: Cortical destruction > 50% diameter on any view indicates 90% loss of torsional strength.
5. Visceral Metastases: Presence of liver or lung metastases doubles SRE risk, reflecting aggressive tumour biology.

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3. Pathophysiology

The Metastatic Cascade to Bone

Skeletal metastasis is not a random process but follows a predictable sequence:

The "Seed and Soil" Hypothesis (Stephen Paget, 1889)

Paget's seminal observation that breast cancer metastasizes preferentially to specific organs (bone, liver, lung) rather than randomly led to the "Seed and Soil" hypothesis: tumour cells ("seeds") require a receptive microenvironment ("soil") to establish metastatic colonies. [23] The bone marrow provides an ideal "soil" rich in growth factors, cytokines, and stromal cells.

The 7-Step Metastatic Cascade

Step 1: Clonal Expansion & Epithelial-Mesenchymal Transition (EMT)

• Primary tumour cells acquire genetic mutations enabling loss of cell-cell adhesion (E-cadherin downregulation).
• Transition to mesenchymal phenotype (N-cadherin upregulation) confers motility and invasiveness.

Step 2: Intravasation

• Malignant cells invade through basement membrane into blood vessels or lymphatics.
• Matrix metalloproteinases (MMPs) degrade extracellular matrix, facilitating invasion.

Step 3: Survival in Circulation

• Tumour cells face hostile circulatory environment: high shear stress, immune surveillance by natural killer (NK) cells.
• Platelet Cloaking: Tumour cells coat themselves with platelets and fibrin to evade immune detection and facilitate arrest in capillary beds.

Step 4: Arrest & Extravasation

• Mechanical trapping in slow-flow sinusoids of red bone marrow (vertebrae, pelvis, proximal long bones).
• Adhesion molecules (integrins) bind endothelial receptors (VCAM-1, E-selectin).
• Batson's valveless venous plexus provides direct venous route from pelvis to spine, bypassing pulmonary/hepatic filters. [9]

Step 5: Dormancy & Colonization

• Disseminated tumour cells may remain dormant in G0 phase for years ("The Sleeping Beauty" phenomenon).
• Reactivation triggered by changes in microenvironment (inflammation, trauma, immune senescence).

Step 6: The Vicious Cycle (Osteolytic Pathway)

This is the central mechanism of bone destruction: [4]

1. Tumour cells secrete Parathyroid Hormone-related Protein (PTHrP).
2. PTHrP binds PTH receptors on osteoblasts, stimulating RANK-L (Receptor Activator of Nuclear Factor Kappa-B Ligand) expression.
3. RANK-L binds RANK receptors on osteoclast precursors, driving fusion into giant multinucleated osteoclasts.
4. Activated osteoclasts resorb bone matrix, releasing trapped growth factors: TGF-β (Transforming Growth Factor-beta) and IGF-1 (Insulin-like Growth Factor-1).
5. TGF-β stimulates further tumour growth and PTHrP production, perpetuating the cycle.
6. Result: Progressive bone destruction (lytic lesions), release of calcium (hypercalcaemia), and skeletal fragility.

Step 7: Osteoblastic Response (Sclerotic Pathway)

In prostate cancer metastases: [13]

1. Tumour cells secrete Endothelin-1, Bone Morphogenetic Proteins (BMPs), and Wnt proteins.
2. These factors directly stimulate osteoblasts to deposit new bone.
3. Result: Sclerotic (blastic) lesions visible as increased density on radiographs.
4. Critical Point: This new bone is disorganized woven bone (not lamellar), mechanically inferior despite increased density, and still prone to fracture.

Molecular Targets and Therapeutic Implications

Understanding the cascade has enabled targeted therapy development:

1. RANK-L Inhibition: Denosumab (monoclonal antibody) blocks RANK-L, preventing osteoclast activation - superior to bisphosphonates in delaying SREs. [24]
2. Bisphosphonates: Zoledronic acid incorporates into bone matrix; released during resorption, induces osteoclast apoptosis.
3. Cathepsin K Inhibitors: Block collagen degradation by osteoclasts (investigational).
4. Src Kinase Inhibitors: Target osteoclast attachment to bone (investigational).

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4. Clinical Presentation

Cardinal Symptoms

1. Pain - The Hallmark Symptom

Bone pain in metastatic disease has distinct characteristics:

Biological (Tumour) Pain:

• Timing: Worse at night, disturbs sleep, unrelieved by rest.
• Character: Deep, gnawing, aching ("toothache in the bone").
• Mechanism: Increased intraosseous pressure, periosteal stretching, release of inflammatory mediators (prostaglandins, bradykinin).
• Response: Excellent response to radiotherapy and NSAIDs.

Mechanical (Structural) Pain:

• Timing: "Start-up pain"
• worse with initial weight-bearing, improves with rest.
• Character: Sharp, activity-related.
• Mechanism: Microfractures, structural instability, cortical stress.
• Significance: Red flag for impending fracture - requires urgent surgical assessment.
• Response: Responds to surgical stabilization, not radiotherapy alone.

2. Neurological Deficit

Indicates spinal metastases with or without cord compression:

• Radiculopathy: Dermatomal pain, weakness, sensory loss in nerve root distribution (e.g., L5 foot drop).
• Myelopathy: Bilateral leg weakness, sensory level, bladder/bowel dysfunction (incontinence or retention), loss of anal tone.
• Timing: MSCC is a surgical emergency - outcomes directly correlate with preoperative neurological status. Patients ambulatory before decompression have 80% chance of walking postoperatively; those paraplegic > 48 hours have less than 10% chance of recovery. [25]

3. Constitutional Symptoms

• Hypercalcaemia: Confusion, polyuria, polydipsia, constipation, nausea, abdominal pain ("Bones, Stones, Moans, Groans").
• Weight Loss: Cachexia from advanced malignancy.
• Fatigue: Multifactorial - anaemia, hypercalcaemia, poor sleep from pain.

Physical Examination Findings

General Inspection

• Gait: Antalgic limp (favouring affected limb).
• Wasting: Muscle atrophy from disuse or neurological deficit.
• Deformity: Pathological fracture with angulation or shortening.
• Scars: Previous cancer surgery (mastectomy, thyroidectomy, nephrectomy).

Focused Musculoskeletal Examination

Look:

• Swelling over affected bone (soft tissue mass).
• Skin changes (erythema rare unless infected).

Feel:

• Spinal Percussion: Percuss spinous processes with closed fist. Exquisite tenderness over involved vertebra is highly specific for metastatic disease (vs. mechanical back pain which is rarely percussion-tender).
• Palpation: Bony tenderness, soft tissue mass, warmth (inflammation).

Move:

• Range of motion often preserved unless joint involvement or completed fracture.
• DO NOT stress test a suspected impending fracture - risk completing the fracture.

Neurovascular:

• Motor: MRC grading 0-5 for all myotomes.
• Sensory: Light touch and pinprick for all dermatomes.
• Reflexes: Deep tendon reflexes, Babinski sign (upper motor neuron lesion).
• Vascular: Distal pulses, capillary refill (exclude vascular injury in fracture).

Systemic Examination for Primary Tumour

In Metastasis of Unknown Primary (MUP):

• Breast: Palpable mass, nipple discharge, skin tethering, axillary lymphadenopathy.
• Thyroid: Thyroid nodule, cervical lymphadenopathy, hoarseness (recurrent laryngeal nerve invasion).
• Prostate: Digital rectal examination - hard, irregular, nodular prostate.
• Lung: Clubbing, lymphadenopathy, pleural effusion.
• Renal: Abdominal mass, haematuria, varicocele (left-sided from renal vein obstruction).

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5. Investigations

Diagnostic Strategy for Metastasis of Unknown Primary (MUP)

When a patient presents with a destructive bone lesion without known cancer history:

Step 1: History and Examination Clues

History:

• Constitutional symptoms: Weight loss, night sweats (lymphoma, lung).
• Haemoptysis (lung), haematuria (renal), change in bowel habit (colorectal).
• Risk factors: Smoking (lung), alcohol (head & neck), family history (breast, prostate).

Examination: As above - search for primary.

Step 2: Baseline Blood Tests ("Metastatic Screen")

Step 3: Imaging the Primary - Hierarchical Approach

First-Line: CT Thorax-Abdomen-Pelvis (CT TAP)

• Sensitivity: Identifies primary in 85% of bone metastases cases.
• Targets: Lung parenchyma and mediastinum, kidneys, adrenals, liver, pancreas, retroperitoneal nodes, ovaries.
• Protocol: Intravenous contrast unless contraindicated (renal impairment).

Second-Line (if CT TAP negative):

• Mammography + Breast Ultrasound (females): Even if normal breast examination - occult breast primary.
• Thyroid Ultrasound: If lytic hypervascular lesion and normal CT TAP.
• Upper GI Endoscopy / Colonoscopy: If GI symptoms or raised CEA/CA19-9.

Third-Line: PET-CT (18F-FDG)

• Indication: CT TAP negative but high suspicion of occult primary.
• Mechanism: Detects hypermetabolic tissue (high glucose uptake by malignant cells).
• Sensitivity: 80-90% for identifying occult primary.
• Interpretation: High SUVmax (> 5) suggests malignancy; low uptake may represent slow-growing tumours (prostate, bronchoalveolar lung ca, neuroendocrine).

If All Imaging Negative: Image-Guided Bone Biopsy

Imaging the Bone Lesion

1. Plain Radiographs (X-ray)

First-line investigation - simple, cheap, universally available:

Lytic Lesions:

• "Moth-eaten" destruction, ill-defined borders.
• Loss of cortical continuity.
• Pathological fracture: transverse fracture line through abnormal bone.

Blastic Lesions:

• Increased density ("sclerotic"), "cotton wool" appearance (prostate).
• "Ivory vertebra" (single vertebra uniformly dense).

Mixed Lesions: Combination of lytic and blastic features (breast).

Limitations:

• 50% Rule: > 50% bone mineral loss required before lytic lesion visible on radiograph (late detection).
• Poor sensitivity for early disease.

2. Bone Scintigraphy (Technetium-99m MDP Scan)

Mechanism:

• Tc-99m methylene diphosphonate (MDP) binds hydroxyapatite deposited by osteoblasts.
• Detects areas of increased bone turnover (both formation and destruction).

Utility:

• Whole-body screening in one examination.
• Excellent for detecting blastic lesions (prostate) - high osteoblast activity.

Limitations:

• False negatives: Purely lytic lesions with minimal osteoblastic response (myeloma, aggressive lung/renal mets) appear "cold" (photopenic).
• False positives: Arthritis, fractures, infection, Paget's disease.
• Poor anatomical localization.

Interpretation: Multiple "hot spots" in axial skeleton = metastases until proven otherwise.

3. MRI (Magnetic Resonance Imaging)

Gold Standard for Spinal Metastases: [25]

Sequences:

• T1-weighted: Metastases appear hypointense (dark) - replace normal bright marrow fat.
• T2-weighted / STIR: Metastases appear hyperintense (bright) - high water content.
• T1 + Gadolinium contrast: Enhancement indicates viable tumour (vs. necrosis).

Advantages:

• Highest sensitivity for marrow involvement (detects disease before cortical destruction).
• Defines epidural extension (spinal cord compression).
• Assesses soft tissue mass.
• Measures longitudinal extent (essential for surgical planning - nail length).

Indications:

• Mandatory in suspected MSCC (NICE guidelines - within 24 hours). [26]
• Preoperative planning for long bone fixation.
• Equivocal findings on other modalities.

4. CT (Computed Tomography)

Strengths:

• Excellent cortical bone detail.
• Assesses fracture risk (cortical thickness remaining).
• CT-guided biopsy.

Weaknesses:

• Inferior to MRI for marrow involvement.
• Radiation exposure.

5. PET-CT (18F-FDG)

Utility:

• Differentiates active tumour from necrosis, post-radiotherapy change, or infection.
• Whole-body staging.

Quantification: SUVmax > 5 suggests active malignancy.

The Biopsy: When, How, and Pitfalls

Indications for Biopsy

1. Metastasis of Unknown Primary: CT TAP and PET-CT fail to identify primary source.
2. Remote History: Cancer diagnosis > 5 years ago - could be new primary bone tumour (sarcoma).
3. Atypical Features: Young age (less than 40), unusual radiographic appearance, solitary lesion.

Technique

• Image-Guided Core Needle Biopsy: CT or fluoroscopy-guided.
• Minimum 3-4 cores for histology, immunohistochemistry, and molecular analysis.
• Biopsy tract planning: Should be excisable if subsequent resection needed (sarcoma).

The "Whoops" Procedure - A Cautionary Tale

Scenario: Surgeon assumes bone lesion is metastasis, performs intramedullary nailing without biopsy. Histology reveals primary bone sarcoma (osteosarcoma, Ewing's, chondrosarcoma).

Consequences:

1. Nail disseminates tumour cells throughout medullary canal.
2. Haematoma contaminates entire muscular compartment.
3. Salvage requires amputation to achieve local control (vs. limb-sparing surgery if managed correctly).

Lesson: Always obtain tissue diagnosis (or CT TAP confirming metastatic primary) before surgical intervention in suspected bone tumours. [19]

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6. Risk Assessment for Pathological Fracture

Mirels' Scoring System (1989)

The Mirels' Score is the validated standard for predicting fracture risk in long bone metastases, guiding prophylactic fixation decisions. [6]

Scoring Table

Total Score: 4-12 points

Interpretation and Management

Clinical Application

Example 1: 65-year-old woman with breast cancer, lytic lesion in mid-femoral shaft (8 cm, > 2/3 diameter), severe pain on walking.

• Site: Lower limb (2 points)
• Pain: Functional (3 points)
• Type: Lytic (3 points)
• Size: > 2/3 (3 points)
• Total: 11 points → Prophylactic fixation indicated

Example 2: 70-year-old man with prostate cancer, blastic lesion in humeral shaft (less than 1/3 diameter), mild pain.

• Site: Upper limb (1 point)
• Pain: Mild (1 point)
• Type: Blastic (1 point)
• Size: less than 1/3 (1 point)
• Total: 4 points → Radiotherapy + Observation

Evidence Base

• Original Mirels' Study: Score ≥9 had 33% fracture rate without surgery; score ≤7 had less than 5% fracture rate. [6]
• Validation Studies: Subsequent validation demonstrated sensitivity 91%, specificity 35% for score ≥9 (high sensitivity but lower specificity - errs on side of caution). [27]

Limitations

• Applies only to long bones (femur, humerus), not spine or pelvis.
• Subjective pain assessment.
• Does not account for patient life expectancy, functional status, or systemic therapy response.

Spinal Instability Neoplastic Score (SINS)

For spinal metastases, SINS score predicts need for surgical stabilization: [28]

SINS Components (Total: 0-18 points)

SINS Interpretation

• 0-6: Stable - Non-operative (radiotherapy, systemic therapy)
• 7-12: Indeterminate - Surgical consultation warranted
• 13-18: Unstable - Surgery indicated (decompression + instrumented fusion)

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7. Management

Multidisciplinary Team (MDT) Approach

Metastatic bone disease management requires coordinated input from multiple specialties: [29]

• Medical Oncologist: Systemic therapy (chemotherapy, immunotherapy, hormonal therapy).
• Clinical Oncologist: Radiotherapy planning and delivery.
• Orthopaedic Surgeon: Surgical stabilization of impending/completed fractures.
• Spinal Surgeon: Decompression and fusion for MSCC.
• Interventional Radiologist: Embolization (RCC, thyroid), vertebroplasty/kyphoplasty, biopsy.
• Palliative Care Physician: Complex pain management, end-of-life planning.
• Physiotherapy: Mobility, falls prevention, rehabilitation.
• Occupational Therapy: Home adaptations, discharge planning.
• Cancer Nurse Specialist: Patient advocacy, coordination of care.

Medical Management

1. Analgesia - The WHO Pain Ladder (Adapted for Bone Pain)

Step 1: Non-Opioid Analgesics

• Paracetamol: 1g QDS (baseline for all patients). Hepatotoxic in overdose; caution if liver metastases.
• NSAIDs: Ibuprofen 400mg TDS, Naproxen 500mg BD.
  • "Mechanism: Inhibit prostaglandin synthesis - highly effective for bone pain."
  • "Cautions: Renal impairment (common in cancer - dehydration, contrast nephropathy), gastritis (co-prescribe PPI - omeprazole 20mg OD), cardiovascular disease."
  • "Contraindications: eGFR less than 30, active peptic ulcer, heart failure."

Step 2: Weak Opioids

• Codeine: 30-60mg QDS (prodrug - requires CYP2D6 conversion to morphine; ineffective in 10% poor metabolizers).
• Tramadol: 50-100mg QDS (dual action - opioid + SNRI). Risk of serotonin syndrome if combined with SSRIs.

Step 3: Strong Opioids

• Morphine: Gold standard for cancer pain.
  • "Immediate-release (Oramorph): 10mg PRN Q4H for breakthrough pain."
  • "Modified-release (MST): Titrate background dose - sum 24h PRN use, divide by 2, give BD."
  • "Example: Patient uses 60mg immediate-release in 24h → MST 30mg BD."
• Oxycodone: Alternative to morphine (less nausea, less itch). 1.5-2x more potent than morphine.
• Fentanyl/Buprenorphine patches: For stable pain only (onset 12-24h, cannot titrate rapidly). Avoid in renal failure (accumulation).

Opioid Side Effects - "The Handshake"

When prescribing opioids, always co-prescribe:

1. Laxatives: Constipation universal. Senna 2 tablets nocte (stimulant) + Movicol 1 sachet BD (osmotic). Avoid bulking agents if dehydrated.
2. Antiemetics: Metoclopramide 10mg TDS (first 3-5 days) or Cyclizine 50mg TDS. Haloperidol 0.5mg nocte for chemical nausea.

Step 4: Adjuvant Analgesics (Neuropathic Pain)

For radicular pain (nerve root compression):

• Gabapentin: Start 300mg nocte, titrate to 600mg TDS (max 3600mg/24h).
• Pregabalin: Start 75mg BD, titrate to 150-300mg BD (faster onset than gabapentin).
• Amitriptyline: 10-25mg nocte (low dose for neuropathic pain).
• Corticosteroids: Dexamethasone 8mg BD (reduces tumour oedema, nerve compression). Taper once radiotherapy takes effect.

Step 5: Interventional Techniques

• Vertebroplasty/Kyphoplasty: Percutaneous cement injection into vertebral body. Provides rapid pain relief + mechanical stabilization.
• Nerve Blocks: Intercostal blocks (rib metastases), epidural (spinal pain).
• Neurolytic Procedures: Chemical or radiofrequency ablation of sensory nerves (reserved for refractory pain).

2. Bone Protection Agents - Preventing SREs

Bisphosphonates vs. Denosumab: Both reduce SRE incidence but differ in mechanism and efficacy. [24,30]

Osteonecrosis of the Jaw (ONJ) - Shared Complication:

• Incidence: 1-2% with prolonged use (> 2 years).
• Risk Factors: Dental extraction, poor oral hygiene, prolonged therapy, corticosteroids.
• Prevention: Mandatory dental assessment before starting therapy. Optimize dental health. Avoid invasive dental procedures during treatment (if unavoidable, drug holiday 2 months pre/post procedure).
• Presentation: Non-healing extraction socket, exposed bone, pain, halitosis.
• Management: Conservative (antibiotics, antiseptic mouthwash), debridement if severe. No definitive cure.

Clinical Guideline: Denosumab preferred over zoledronic acid in solid tumours unless renal impairment contraindicates neither (both safe if normal renal function). Calcium + Vitamin D supplementation mandatory with denosumab (risk of hypocalcaemia). [30]

3. Systemic Oncological Therapy

Hormone-Sensitive Cancers:

• Breast: Aromatase inhibitors (letrozole, anastrozole) for ER+ postmenopausal; Tamoxifen for premenopausal.
• Prostate: Androgen deprivation therapy (ADT) - LHRH agonists (goserelin), anti-androgens (bicalutamide), abiraterone, enzalutamide.

Targeted Therapy:

• HER2+ Breast: Trastuzumab (Herceptin), pertuzumab.
• Renal Cell Carcinoma: Tyrosine kinase inhibitors (sunitinib, pazopanib), mTOR inhibitors (everolimus), immunotherapy (nivolumab, ipilimumab).

Chemotherapy: Limited role in bone metastases except chemosensitive primaries (lung, ovarian).

Radiotherapy

External beam radiotherapy (EBRT) is the cornerstone of palliative treatment for painful bone metastases. [21]

Indications

1. Pain relief: Painful bone metastases (most common indication).
2. Prophylaxis: Impending fracture (Mirels ≤8) - not suitable for surgery.
3. Post-operative adjuvant: After surgical fixation (prevents tumour progression, implant loosening).
4. MSCC: Radiosensitive tumours (myeloma, lymphoma, SCLC) as primary treatment; adjuvant after surgical decompression in radioresistant tumours.

Dose Fractionation

Single Fraction vs. Multi-Fraction: Landmark meta-analyses demonstrate equivalent pain relief. [21]

Clinical Decision-Making:

• Single fraction (8 Gy): Preferred for poor performance status, short life expectancy, logistical barriers (transport). Single hospital visit.
• Multi-fraction (20 Gy/5 or 30 Gy/10): Consider if long life expectancy, prior radiotherapy to same site, better durability of response.

Evidence: Cochrane systematic review (25 RCTs, > 5000 patients) found no difference in overall pain relief between single and multi-fraction regimens. [21]

Onset and Duration

• Onset: Pain relief typically begins 2-4 weeks post-treatment (some patients experience temporary "flare" pain in first 48h).
• Duration: Median response duration 12-24 weeks (varies by primary tumour biology).
• Response Rate: 60-80% achieve partial/complete pain relief.

Side Effects

• Acute: Fatigue, radiation dermatitis (erythema), nausea (if treating upper abdomen/pelvis).
• Late: Rare with palliative doses.
• Flare Pain: Temporary worsening of pain in 10-20% (prophylactic dexamethasone can reduce).

Re-irradiation

• Feasibility: Can re-treat same site if pain recurs, provided tissue tolerance not exceeded.
• Typical practice: Wait 4-6 weeks, reassess; if recurrence, consider repeat single 8 Gy fraction.

Surgical Management

Indications for Surgery

Absolute Indications:

1. Pathological fracture (completed) of weight-bearing bone (femur, tibia).
2. Impending fracture (Mirels ≥9).
3. Malignant Spinal Cord Compression (MSCC) - see dedicated section.

Relative Indications:

• Solitary metastasis with good prognosis (> 6 months expected survival) - consider wide excision + endoprosthetic reconstruction.
• Intractable pain despite maximal medical therapy + radiotherapy.

Preoperative Checklist

Before taking metastatic patient to theatre:

1. MDT Discussion: Confirm surgical plan aligns with oncological plan, prognosis > 4-6 weeks.
2. Blood Work:
   • FBC: Hb > 80 g/L (transfuse if lower), Platelets > 50 x10⁹/L (transfuse if lower).
   • Clotting: INR less than 1.5 (reverse anticoagulation).
   • Group & Save: Crossmatch 4 units (RCC/thyroid), 2 units (other).
3. Embolization: Confirmed completed if RCC, thyroid, myeloma (within 24-48h preop). [17]
4. Imaging: Full-length MRI (spine) or radiographs (long bones) - define extent of disease → implant selection.
5. Performance Status: Karnofsky > 40 or ECOG 0-3 (KPS less than 40 or ECOG 4 = poor surgical candidates).
6. Consent: Document palliative intent, risks (death, infection, implant failure, blood loss), realistic functional outcomes.

Surgical Principles - Long Bones

1. Intramedullary (IM) Nailing - Preferred

Advantages:

• Load-sharing device: Nail shares load with bone (vs. plate = load-bearing).
• Biomechanically superior: Central position within bone resists bending/torsion.
• Protects entire bone: Spans proximal to distal, preventing fracture at secondary metastatic site (cf. short plate leaves stress risers).
• Immediate weight-bearing: Locked nail allows full weight-bearing day 1.
• Minimally invasive: Closed technique, smaller incisions, less soft tissue dissection.

Indications: Diaphyseal (shaft) lesions of femur, tibia, humerus.

Technique - Femoral IM Nailing:

1. Entry Point: Greater trochanter tip (antegrade nail) or intercondylar notch (retrograde nail).
2. Guidewire Passage: Pass guidewire across lesion under fluoroscopy (critical step - wire must stay intramedullary, not perforate cortex).
3. Reaming: Sequentially ream to appropriate diameter (typically 10-13mm).
   • Caution: Reaming increases intramedullary pressure → fat embolism risk. Consider venting (drill hole distal to lesion to allow pressure escape).
4. Nail Insertion: Insert long nail spanning entire femur (hip to knee).
5. Proximal Locking: Cephalocervical screws into femoral head/neck (prevent rotation, proximal migration).
6. Distal Locking: Static locking screws through distal femur (prevent shortening, rotation).
7. Cement Augmentation (if large cavity):
   • Inject polymethylmethacrylate (PMMA) bone cement into lytic defect after nail insertion.
   • Thermal necrosis: Exothermic polymerization reaction reaches 70°C → kills local tumour cells (adjuvant effect).
   • Fills void, improves construct stability.

Complications:

• Intraoperative: Iatrogenic fracture (guidewire perforation), fat embolism, cement extravasation.
• Postoperative: Infection (2-5%), implant failure (nail breakage if patient outlives construct), progression of disease.

2. Plate Fixation

Indications: Metaphyseal/epiphyseal lesions (periarticular) where IM nail biomechanically unsuitable.

Disadvantages:

• Load-bearing (vs. load-sharing) - plate takes all force until bone heals (which never occurs in metastatic disease).
• Screws pull out of osteoporotic/tumour-infiltrated bone.
• Does not protect entire bone.

Technique: Locking plate with cement augmentation of screws mandatory (improves pullout strength).

3. Endoprosthetic Reconstruction (Tumour Prosthesis)

Indications:

• Massive juxta-articular bone destruction (proximal femur, distal femur, proximal tibia, proximal humerus) unsuitable for fixation.
• Failed previous fixation (implant loosening, progressive disease).
• Solitary metastasis with good prognosis (> 1 year) - consider wide excision + reconstruction.

Technique:

• En-bloc resection of affected bone segment (e.g., proximal femur).
• Modular mega-prosthesis replaces bone + joint (e.g., proximal femoral replacement - includes hip joint + proximal 10-20cm femoral shaft).
• Cemented stem into distal bone.

Advantages: Immediate pain relief, restoration of function, immediate weight-bearing.

Disadvantages: High infection risk (10-15%), dislocation (hip replacements), mechanical failure (loosening, breakage), expensive.

Outcomes: Functional improvement in 80-90%, complication rate 20-30%. [31]

Surgical Principles - Spine (MSCC)

MSCC Management - NOMS Framework: [25]

Decision-making based on 4 pillars:

N - Neurologic Status:

• Low-grade: Radicular pain only, ambulatory.
• High-grade: Motor deficit, myelopathy, non-ambulatory.

O - Oncologic (Radiosensitivity):

• Radiosensitive: Myeloma, lymphoma, small cell lung cancer, germ cell → Radiotherapy primary treatment.
• Radioresistant: Renal cell carcinoma, melanoma, sarcoma → Surgery primary treatment.

M - Mechanical Instability (SINS Score):

• Stable (SINS 0-6): No surgery needed for stability.
• Unstable (SINS 13-18): Surgery mandatory (decompression + instrumented fusion).

S - Systemic Disease/Performance Status:

• KPS > 40, ECOG 0-3: Surgical candidate.
• KPS less than 40, ECOG 4: Poor surgical candidate → radiotherapy or supportive care only.

Patchell Trial (2005): Landmark RCT demonstrating surgery + radiotherapy superior to radiotherapy alone in MSCC. [25]

• Design: 101 patients with solid tumour MSCC, randomized to decompressive surgery + radiotherapy vs. radiotherapy alone.
• Results:
  • "Walking ability: 84% surgery group vs. 57% radiotherapy-only group retained/regained walking (p=0.001)."
  • "Survival: 126 days surgery vs. 100 days radiotherapy (p=0.033)."
• Key Finding: Benefit greatest if surgery performed while still ambulatory (vs. paraplegic).

Surgical Technique - Posterior Decompression + Stabilization:

1. Decompression: Laminectomy ± corpectomy (vertebral body excision if anterior compression).
2. Stabilization: Pedicle screw fixation 2-3 levels above and below affected level + rods.
3. Cement Augmentation: Vertebroplasty/kyphoplasty for additional stability.

Postoperative: Radiotherapy within 2 weeks (kills residual tumour, prevents recurrence).

Bone Cement Implantation Syndrome (BCIS)

Definition: Catastrophic cardiovascular collapse during cemented arthroplasty or cement augmentation, caused by embolization of marrow fat, cement particles, and air into pulmonary circulation. [32]

Mechanism: Pressurizing cement into medullary canal forces marrow contents into venous sinusoids → right heart → pulmonary vasculature → pulmonary hypertension, hypoxia, hypotension, cardiac arrest.

Risk Factors:

• Elderly (> 70 years).
• Poor cardiopulmonary reserve.
• Metastatic disease (abnormal marrow).
• Long bone (femur > humerus > tibia).
• Unvented canal.

Clinical Presentation:

• Timing: During or immediately after cement insertion.
• Signs: Sudden desaturation (SpO₂ drop), hypotension (SBP less than 90), bradycardia, cardiac arrest.

Prevention:

1. Venting: Drill distal hole in bone to allow pressure escape.
2. Lavage: Copious pulsatile lavage of canal (remove loose marrow before cementing).
3. Anesthetic Preparation: Inform anesthetist before cementing → increase FiO₂ to 100%, optimize fluids.
4. Retrograde Cementing: Fill canal from distal to proximal (reduces pressurization).

Management: Advanced Life Support protocol - fluids, inotropes, intubation/ventilation if arrest.

Rehabilitation and Supportive Care

Weight-Bearing Status:

• IM Nail / Cemented Prosthesis: Full weight-bearing as tolerated immediately (metal takes load).
• Plate Fixation: Partially weight-bearing (touch toe weight-bearing) 6 weeks → full weight-bearing 12 weeks (if bone healing - unlikely in mets).

Physiotherapy Goals:

• Early mobilization (prevent pneumonia, DVT).
• Gait re-education.
• Provision of walking aids (frame, crutches).
• Falls risk assessment.

Occupational Therapy:

• Home assessment: Stairs, bathroom access.
• Adaptations: Stair lift, hospital bed, raised toilet seat.
• Discharge planning: Home vs. rehabilitation facility vs. hospice.

VTE Prophylaxis:

Cancer patients undergoing orthopaedic surgery have highest VTE risk (Caprini score typically > 5):

• Mechanical: TED stockings, intermittent pneumatic compression (flowtron boots).
• Pharmacological: LMWH (enoxaparin 40mg SC OD) for 28 days post-surgery (extended prophylaxis).
• Contraindications: Platelets less than 50, active bleeding, brain metastases (high bleed risk).

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8. Complications

Skeletal Related Events (SREs)

SREs are major complications directly related to bone metastases: [2]

1. Pathological Fracture (25-30% of patients).
2. Malignant Spinal Cord Compression (5-10%).
3. Requirement for Surgery or Radiotherapy to Bone.
4. Hypercalcaemia of Malignancy (10-20%).

Impact: Each SRE significantly worsens quality of life, increases healthcare costs, and reduces survival.

Hypercalcaemia of Malignancy

Definition: Corrected serum calcium > 2.6 mmol/L (> 10.5 mg/dL) in cancer patient.

Incidence: 10-20% of advanced cancer patients; 30% in bone metastases.

Mechanisms: [33]

1. Humoral Hypercalcaemia of Malignancy (HHM) - 80% of cases:

   • Tumour secretes PTHrP (parathyroid hormone-related protein) systemically.
   • PTHrP mimics PTH → increases bone resorption + renal calcium reabsorption + intestinal absorption.
   • Tumours: Squamous cell (lung, head/neck), breast, renal.

2. Local Osteolytic Hypercalcaemia (LOH) - 20%:

   • Direct bone destruction by metastases releases calcium.
   • Tumours: Breast, myeloma.

3. Ectopic 1,25-Vitamin D Production - Rare:

   • Lymphomas convert 25-OH-D to active 1,25-OH-D → increased intestinal absorption.

Symptoms - "Bones, Stones, Moans, Groans":

• Bones: Bone pain.
• Stones: Renal stones, polyuria (nephrogenic diabetes insipidus).
• Moans: Depression, confusion, psychosis.
• Groans: Abdominal pain, constipation, nausea, vomiting.

Severity:

• Mild: 2.6-3.0 mmol/L - often asymptomatic.
• Moderate: 3.0-3.5 mmol/L - symptomatic.
• Severe: > 3.5 mmol/L - medical emergency (confusion, arrhythmias, renal failure).

ECG Changes: Shortened QT interval, widened QRS, J waves (Osborn waves).

Management Protocol:

1. Hydration (First-line):

   • IV 0.9% Normal Saline 3-4 litres in first 24 hours (corrects dehydration, promotes renal calcium excretion).
   • Monitor fluid balance (risk of fluid overload in elderly/heart failure).

2. Bisphosphonates (Definitive):

   • Zoledronic acid 4mg IV over 15 minutes.
   • Onset: 2-4 days (delayed effect).
   • Duration: 2-4 weeks.
   • Mechanism: Inhibits osteoclast activity.

3. Denosumab (Alternative):

   • 120mg SC (if bisphosphonates contraindicated - renal failure).
   • Faster onset than bisphosphonates.

4. Calcitonin (Rarely used):

   • Rapid onset (4-6 hours) but short duration (tachyphylaxis develops 48-72h).
   • Salmon calcitonin 4 IU/kg IM/SC Q12H.

5. Corticosteroids (specific indications):

   • Prednisolone 40-60mg OD if lymphoma/myeloma (inhibits bone resorption + tumour activity).

Prognosis: Median survival after hypercalcaemia episode: 3 months (poor prognostic sign). [33]

Malignant Spinal Cord Compression (MSCC)

Covered comprehensively in Section 7 (Surgical Management). Key points:

• Oncological emergency - outcomes depend on speed of intervention.
• NICE Guidelines: MRI whole spine within 24h, Dexamethasone 16mg immediately, definitive treatment within 24-48h. [26]
• Patchell Trial: Surgery + RT superior to RT alone if ambulatory, single-level disease, life expectancy > 3 months. [25]

Surgical Complications

Intraoperative:

• Haemorrhage: Especially hypervascular metastases (RCC, thyroid, myeloma) - can lose > 2L blood. Embolization critical.
• Fat Embolism / BCIS: As described above.
• Iatrogenic Fracture: Guidewire perforation, overzealous reaming.

Early Postoperative:

• Infection: 5-10% (higher than trauma - immunosuppressed from cancer/chemotherapy).
  • "Prophylaxis: IV antibiotics (cefazolin 2g at induction + 2 further doses)."
  • "Treatment: Washout + antibiotics (retain implant if less than 3 weeks; remove if chronic)."
• VTE: DVT/PE (high risk - cancer, immobility, surgery). Prophylaxis essential.
• Wound Dehiscence: Poor healing (malnutrition, steroids, radiotherapy).

Late:

• Implant Failure: If patient outlives implant (fatigue fracture of nail/screws after 12-24 months). Revision surgery required.
• Local Disease Progression: Tumour grows despite radiotherapy → loosening, pain recurrence.
• Periprosthetic Fracture: Fracture adjacent to implant.

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9. Prognosis

Survival Prediction Scores

Tokuhashi Score (Revised 2005): Predicts survival in spinal metastases, guides extent of surgical intervention. [34]

Tokuhashi Scoring (Total: 0-15 points)

Interpretation:

• 0-8 points: Prognosis less than 6 months → Conservative or minimally invasive (vertebroplasty, radiotherapy).
• 9-11 points: Prognosis 6-12 months → Palliative surgery (decompression, limited fixation).
• 12-15 points: Prognosis > 12 months → Aggressive surgery (en-bloc resection, extensive reconstruction).

Katagiri Score (General Bone Metastases)

Predicts 1-year survival in skeletal metastases (any site): [35]

Variables (1 point each if present):

1. Lung or liver metastases.
2. Poor performance status (non-ambulatory).
3. Previous chemotherapy.
4. Primary tumour = lung, stomach, bladder, esophagus, pancreas, or unknown.
5. Multiple skeletal metastases.

Score Interpretation:

• 0-1 points: 1-year survival 82%.
• 2 points: 1-year survival 55%.
• 3 points: 1-year survival 26%.
• 4-5 points: 1-year survival 7%.

Clinical Use: Guide aggressive interventions (prophylactic fixation, endoprosthetic reconstruction) to patients likely to benefit (scores 0-2).

Prognostic Factors

Favourable:

• Primary tumour: Breast, prostate, thyroid (hormone-sensitive, slow-growing).
• Bone-only metastases (no visceral involvement).
• Good performance status (KPS > 70, ECOG 0-2).
• Single/oligometastatic disease.
• Response to systemic therapy.

Unfavourable:

• Primary tumour: Lung, gastric, melanoma, unknown.
• Visceral metastases (liver, lung, brain).
• Poor performance status (KPS less than 40, ECOG 3-4).
• Hypercalcaemia.
• Pathological fracture.

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10. Guidelines and Evidence

Key Clinical Guidelines

1. BOAST 4: Metastatic Bone Disease (BOA, 2021)

British Orthopaedic Association Standards for Trauma mandate: [36]

• MDT Discussion: All patients must be discussed in specialized Bone Metastasis MDT.
• Timing: Surgery for pathological/impending fractures within 48 hours of admission (not emergency, but urgent).
• Implant Selection: Long intramedullary nails spanning whole bone preferred.
• Adjuvant Radiotherapy: All patients require postoperative radiotherapy (unless prognosis less than 4 weeks).
• Embolization: Mandatory for RCC, thyroid, myeloma metastases 24-48h preoperatively.

2. NICE CG75: Metastatic Spinal Cord Compression (2008)

• Coordinator: Designated MSCC Coordinator in every hospital (24/7 availability).
• Imaging: MRI whole spine within 24 hours of clinical suspicion.
• Steroids: Dexamethasone 16mg (+ PPI) immediately upon suspicion, before MRI.
• Treatment Timing: Definitive treatment (surgery or radiotherapy) within 24 hours of diagnosis.
• Surgery: Offer to patients who are ambulatory, single-level disease, radiosensitive tumour. [26]

Landmark Papers

1. Mirels H (1989) - Mirels' Score

Citation: Mirels H. Metastatic disease in long bones. A proposed scoring system for diagnosing impending pathologic fractures. Clin Orthop Relat Res. 1989;249:256-64. PMID: 2684463.

Study: Retrospective review of 78 patients with long bone metastases.

Key Finding: Scoring system (site, pain, size, type) predicted fracture risk. Score ≥9 → 33% fracture rate; ≤7 → less than 5%.

Impact: Established standard for prophylactic fixation decisions worldwide.

2. Patchell RA et al (2005) - Surgery for MSCC

Citation: Patchell RA, Tibbs PA, Regine WF, et al. Direct decompressive surgical resection in the treatment of spinal cord compression caused by metastatic cancer: a randomised trial. Lancet. 2005;366(9486):643-8. doi:10.1016/S0140-6736(05)66954-1

Study: RCT, 101 patients, surgery + RT vs. RT alone.

Results: 84% surgery group vs. 57% RT-only retained walking (p=0.001). Survival 126 vs. 100 days (p=0.033).

Impact: Paradigm shift - surgery now standard for eligible MSCC patients.

3. Stopeck AT et al (2010) - Denosumab vs. Zoledronic Acid

Citation: Stopeck AT, Lipton A, Body JJ, et al. Denosumab compared with zoledronic acid for the treatment of bone metastases in patients with advanced breast cancer: a randomized, double-blind study. J Clin Oncol. 2010;28(35):5132-9. doi:10.1200/JCO.2010.29.7101

Study: RCT, 2046 breast cancer patients with bone metastases.

Results: Denosumab delayed time to first SRE (median not reached vs. 26.4 months zoledronic acid, HR 0.82, p=0.01).

Impact: Denosumab superior to bisphosphonates for SRE prevention in solid tumours. [24]

4. Wu JS et al (2003) - Meta-analysis of Radiotherapy Fractionation

Citation: Wu JS, Wong R, Johnston M, et al. Meta-analysis of dose-fractionation radiotherapy trials for the palliation of painful bone metastases. Int J Radiat Oncol Biol Phys. 2003;55(3):594-605. doi:10.1016/S0360-3016(02)04147-0

Results: No difference in pain relief between single fraction (8 Gy) and multi-fraction (20-30 Gy) regimens.

Impact: Single fraction now standard for uncomplicated bone metastases (patient convenience). [21]

5. Fisher CG et al (2010) - SINS Score

Citation: Fisher CG, DiPaola CP, Ryken TC, et al. A novel classification system for spinal instability in neoplastic disease: an evidence-based approach and expert consensus from the Spine Oncology Study Group. Spine. 2010;35(22):E1221-9. doi:10.1097/BRS.0b013e3181e16ae2

Study: Delphi consensus process, validated scoring system for spinal instability.

Impact: SINS score now standard for surgical decision-making in spinal metastases. [28]

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11. Patient Explanation (Layperson Language)

What are bone metastases?

Cancer cells from your original tumour (such as breast, lung, or prostate) have travelled through your bloodstream and settled in your bones. Think of them like "seeds" landing in "soil"

• the bone provides nutrients that help these cancer cells grow. They weaken the bone structure from the inside, like termites in wood.

Why does my bone hurt?

There are two types of pain:

1. Tumour pain: A deep, gnawing ache that's worse at night and doesn't improve with rest. This is caused by pressure building up inside the bone and inflammation.

2. Mechanical pain: Sharp pain when you put weight on the bone (like standing or walking). This is a warning sign that your bone is becoming weak and at risk of breaking.

Why surgery before it breaks?

Your bone is like a tree branch with a hole drilled through it. Right now, it's holding your weight, but barely. If you twist, stumble, or fall, it will snap - this is called a "pathological fracture."

Fixing it now (prophylactic surgery):

• Small operation under control.
• Metal rod inserted through the bone (like rebar in concrete).
• You can walk on it immediately.
• Recovery takes 2-4 weeks.

Waiting until it breaks:

• Emergency operation.
• Much more painful, longer surgery, more blood loss.
• Longer hospital stay (weeks).
• Recovery takes 3-6 months.
• Higher risk of death.

The decision is based on the Mirels Score - we measure:

1. Where the hole is (thigh bone = high risk).
2. How big it is (> 2/3 of the bone = high risk).
3. Whether it hurts when you walk (yes = high risk).
4. What type (lytic "eating away" = high risk).

If your score is high (9 or more out of 12), we strongly recommend fixing it now.

What about the cancer - won't surgery spread it?

No. The cancer has already spread to your bone - that's why you have this lesion. Surgery protects the bone so you can stay mobile and independent. We also use special bone cement that heats up to 70°C when it sets, which kills cancer cells locally.

After surgery, you'll have radiotherapy (like a strong X-ray beam) to shrink the tumour and prevent it growing back.

Will I be in pain forever?

No. We have excellent pain control:

1. Radiotherapy: 60-80% of patients get significant pain relief within 2-4 weeks. Often just one session needed.
2. Painkillers: Combination of paracetamol, anti-inflammatories (ibuprofen), and stronger medicines (morphine if needed).
3. Bone-strengthening drugs: Monthly injections (denosumab) or IV infusions (zoledronic acid) slow the cancer in your bones and reduce pain.

What is denosumab/zoledronic acid?

These drugs stop your bones from being eaten away by the cancer:

• How they work: Cancer cells trick your bone-dissolving cells (osteoclasts) into overdrive. These drugs switch them off.
• Benefit: Reduce risk of fractures, reduce pain, slow cancer growth in bone.
• Schedule: Injection or infusion every 4 weeks.
• Side effects: Flu-like symptoms after first dose (common), low calcium (we give you calcium tablets), rare jaw problems (1-2% - we check your teeth first).

Red flags - when to call 999

Go to A&E immediately if:

1. Sudden snap: You hear/feel a crack in your thigh and can't stand.
2. Leg weakness: You suddenly can't move your legs.
3. Numbness: A band of numbness around your tummy or down your legs.
4. Toilet problems: You lose control of your bladder or bowels.
5. Severe confusion: Drowsiness, excessive thirst, vomiting (this could be high calcium in your blood - life-threatening).

These are emergencies - call 999 immediately.

How long will I live?

This depends entirely on what type of cancer you have:

• Breast/Prostate: Many patients live 2-5+ years with bone metastases. It's a chronic disease we manage long-term.
• Lung: Prognosis is shorter (months), so we focus on quality of life and staying mobile.

The good news: Research shows that fixing your bone before it breaks doubles your chance of surviving the year compared to waiting for it to break.

Will I be able to walk?

Yes - this is the goal of all treatment:

• After prophylactic surgery: Most patients walk the next day with a frame or crutches.
• After completed fracture surgery: Takes weeks to months.
• With radiotherapy alone (if not suitable for surgery): 60-80% get enough pain relief to mobilize with aids.

Staying mobile is crucial - it prevents pneumonia, blood clots, and maintains your independence and quality of life.

What about side effects of morphine?

Many patients worry about morphine. The truth:

• Addiction: When used for genuine severe pain, addiction is extremely rare. We monitor carefully.
• Constipation: Universal - we prescribe laxatives automatically.
• Drowsiness: Common first week, then improves. If severe, we adjust dose.

There is no ceiling dose for cancer pain - we titrate (adjust) to control your pain while minimizing side effects.

Support and resources

• Macmillan Cancer Support: 0808 808 00 00 (free helpline).
• Palliative Care Team: Specialists in pain control and quality of life - ask your doctor for referral.
• Physiotherapy: Help you stay mobile, provide walking aids.
• Occupational Therapy: Home adaptations (stair lifts, raised toilet seats).

Remember: You are not alone. A whole team (oncologists, surgeons, pain specialists, nurses, physiotherapists) is working together to help you.

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12. Examination Focus (FRCS Orth / FRACS / MRCS)

Common Viva Questions

Q1: "A 65-year-old lady with breast cancer presents with thigh pain. X-ray shows a lytic lesion in the femoral shaft. What is your management?"

Model Answer:

"This is a case of metastatic bone disease to the femur in a patient with known breast cancer. My priorities are to assess fracture risk, optimize pain control, and coordinate multidisciplinary management.

Assessment:

• I would take a focused history: Is the pain worse at night (biological) or on weight-bearing (mechanical - red flag for impending fracture)?
• Examination: Can she weight-bear? Neurovascular status intact? Signs of systemic disease?
• Bloods: FBC, renal function, corrected calcium, bone profile (exclude hypercalcaemia).
• Imaging: Full-length femur X-rays (AP and lateral) to assess lesion size and cortical integrity. I would calculate the Mirels score.

Mirels Score (site, pain, size, type):

• If ≤7: Non-operative - Radiotherapy + bone protection agents (denosumab or zoledronic acid).
• If 8: Grey zone - discuss at MDT, consider prophylactic fixation if functionally demanding or long life expectancy.
• If ≥9: Prophylactic intramedullary nailing - fix it before it breaks.

Operative Management (if Mirels ≥9):

• Preoperative workup: Crossmatch 2 units, FBC/clotting, Group & Save, cardiorespiratory optimization.
• Procedure: Long intramedullary nail spanning entire femur (proximal femur to distal femur). Cement augmentation of lytic cavity if large defect.
• Postoperative: Full weight-bearing day 1, adjuvant radiotherapy within 2-4 weeks, continue bone protection agents.

MDT Discussion: Oncology input for systemic therapy (hormonal if ER+, chemotherapy if triple-negative/HER2+), palliative care for pain optimization."

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Q2: "What is the mechanism of the 'vicious cycle' in bone metastases?"

Model Answer:

"The vicious cycle describes the self-perpetuating process of bone destruction in metastatic disease:

1. Tumour cells (e.g., from breast cancer) arrive in bone marrow and secrete PTHrP (parathyroid hormone-related protein).
2. PTHrP binds to PTH receptors on osteoblasts, stimulating them to upregulate RANK-L (Receptor Activator of NF-κB Ligand).
3. RANK-L binds to RANK receptors on osteoclast precursors, causing them to fuse into giant multinucleated osteoclasts.
4. Activated osteoclasts resorb bone, releasing trapped growth factors from the bone matrix, particularly TGF-β (transforming growth factor beta) and IGF-1 (insulin-like growth factor-1).
5. TGF-β stimulates tumour cells to proliferate further and produce more PTHrP, thus perpetuating the cycle.

The result is progressive bone destruction (lytic lesions), release of calcium (hypercalcaemia), and skeletal fragility.

Therapeutic Target: This cycle is interrupted by:

• Denosumab: Monoclonal antibody against RANK-L, blocking osteoclast activation.
• Bisphosphonates (e.g., zoledronic acid): Induce osteoclast apoptosis.

Both agents reduce skeletal-related events (fractures, cord compression) by 30-40%."

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Q3: "What are the indications for surgical fixation in metastatic bone disease?"

Model Answer:

"Surgical fixation is indicated in:

Absolute Indications:

1. Completed pathological fracture of a weight-bearing bone (femur, tibia).
2. Impending fracture - Mirels score ≥9.
3. Malignant spinal cord compression (MSCC) with neurological deficit, in appropriate surgical candidates.

Relative Indications:

1. Intractable pain despite maximal medical therapy and radiotherapy.
2. Solitary metastasis with good prognosis (> 12 months expected survival) - consider wide excision + endoprosthetic reconstruction.
3. Mirels score 8 ('grey zone') - individualize based on functional demands and life expectancy.

Contraindications to Surgery:

1. Very poor performance status (KPS less than 40, ECOG 4, bedridden).
2. Life expectancy less than 4-6 weeks.
3. Uncontrolled sepsis.
4. Uncorrectable coagulopathy/thrombocytopenia (unless emergency).

Special Considerations:

• Renal cell carcinoma / Thyroid metastases: Hypervascular - mandatory preoperative embolization 24-48h before surgery to reduce catastrophic bleeding risk.
• Location: Peritrochanteric femur carries highest fracture risk (Mirels 3 points for site alone) - lower threshold for prophylactic fixation."

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Q4: "Describe the Patchell trial and its impact on MSCC management."

Model Answer:

Patchell Trial (2005):

• Design: Randomized controlled trial, 101 patients with solid tumour MSCC, no prior spine surgery.
• Intervention: Direct decompressive surgery (laminectomy ± corpectomy) + radiotherapy vs. radiotherapy alone.
• Primary Outcome: Ability to walk posttreatment.

Results:

• Walking: 84% surgery group vs. 57% radiotherapy-only group retained/regained walking (pless than 0.001).
• Maintenance of Walking: 122 days surgery vs. 13 days radiotherapy (p=0.003).
• Survival: 126 days surgery vs. 100 days radiotherapy (p=0.033).
• Key Subgroup: Benefit greatest in patients ambulatory preoperatively, single-level disease, and good performance status.

Impact:

• Paradigm shift from radiotherapy as sole treatment to surgery + radiotherapy as standard for eligible patients.
• Emphasized importance of early diagnosis and treatment while still ambulatory - outcomes critically dependent on preoperative neurological status.

Current Practice:

• MSCC patients are screened using NOMS framework (Neurologic, Oncologic, Mechanical, Systemic):
  • Radiosensitive tumours (myeloma, lymphoma, SCLC) → Radiotherapy primary.
  • Radioresistant tumours (RCC, melanoma) + ambulatory + SINS ≥7 → Surgery + adjuvant radiotherapy."

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Q5: "What is BCIS and how do you prevent it?"

Model Answer:

Bone Cement Implantation Syndrome (BCIS) is a potentially fatal cardiovascular collapse during cemented arthroplasty or cement augmentation.

Mechanism:

• Pressurization of cement into medullary canal forces marrow fat, cement particles, bone debris, and air into venous sinusoids.
• Embolization to pulmonary circulation → acute pulmonary hypertension → right heart strain → hypoxia, hypotension, cardiac arrest.

Clinical Features:

• Timing: During or within minutes of cement insertion.
• Signs: Sudden desaturation (SpO₂ drop), hypotension (SBP less than 90 mmHg), tachycardia/bradycardia, cardiac arrest.
• Severity Grading (Donaldson):
  • "Grade 1: Moderate hypotension/desaturation."
  • "Grade 2: Severe hypotension (SBP less than 90) or SpO₂ less than 90%."
  • "Grade 3: Cardiovascular collapse requiring CPR."

Risk Factors:

• Elderly (> 70 years).
• ASA 3-4 (poor cardiopulmonary reserve).
• Metastatic bone disease (abnormal marrow).
• Long bone fractures (femur).
• High-pressure cementing.

Prevention:

1. Identify high-risk patients - optimize preoperatively.
2. Lavage: Copious pulsatile lavage (pulse lavage) of medullary canal to remove marrow fat before cementing.
3. Venting: Drill distal hole in bone to allow pressure escape during cement insertion.
4. Retrograde cementing: Fill from distal to proximal (reduces intramedullary pressure spikes).
5. Anesthetic preparation: Warn anesthetist before cementing → increase FiO₂ to 100%, ensure adequate fluid resuscitation, have vasopressors ready.

Management:

• Supportive: 100% oxygen, IV fluid bolus, inotropes (metaraminol, ephedrine).
• Severe: Intubation, ventilation, advanced life support protocol."

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OSCE Station: "Limping Cancer Patient"

Scenario: 65-year-old man with history of lung cancer. 3-week history of right thigh pain, now limping.

Task: Assess and formulate management plan.

Approach:

1. Introduction: "Hello Mr. Smith, I'm Dr. X. I understand you've been having pain in your right thigh. I'd like to ask some questions and examine you. Is that alright?"

2. History:

   • Pain: "Where exactly? When did it start? Getting worse?"
   • Key discriminators:
     • "Is it worse at night or during the day?" (Night = biological; day/activity = mechanical).
     • "Does it hurt when you put weight on it - like when standing up or walking?" (Functional pain = impending fracture - most important question).
   • Red flags: "Any weakness in your legs? Numbness? Bladder/bowel problems?"
   • Systemic: "Confusion, excessive thirst, vomiting?" (Hypercalcaemia).

3. Examination:

   • Look: Gait (antalgic limp), leg length (shortening if completed fracture), wasting (quadriceps).
   • Feel: Palpate femur gently - "Does this hurt?" DO NOT stress test (risk completing fracture).
   • Move: Hip range of motion (limited by pain if proximal femur lesion).
   • Neurovascular: Motor power (L2-S1), sensation, distal pulses.

4. Investigation Plan:

   • "I would like to arrange an urgent full-length femur X-ray - both AP and lateral views."
   • Bloods: FBC, U&E (calcium!), bone profile, LFTs.
   • "If X-ray confirms lytic lesion, I would calculate Mirels score to assess fracture risk."

5. Management Plan:

   • Analgesia: "Start regular paracetamol and ibuprofen (if no contraindications). If severe pain, add morphine."
   • Mobility: "Non-weight-bearing on right leg until assessed - use crutches."
   • Mirels ≥9: "Refer urgently to orthopaedic oncology for prophylactic intramedullary nailing."
   • Mirels ≤7: "Refer to clinical oncology for radiotherapy."
   • MDT Discussion: "Discuss at bone metastasis MDT for coordination of surgical + oncological + palliative care."

6. Safety Net: "If you have sudden severe pain, inability to bear weight, or any leg weakness or numbness, you must come to A&E immediately."

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Common Mistakes That Fail Candidates

❌ Failure to recognize functional pain as predictor of impending fracture - candidates who dismiss weight-bearing pain miss the single most important clinical sign.

❌ Ordering just hip or pelvis X-ray (not full-length femur) - may miss shaft lesions.

❌ Recommending observation for Mirels ≥9 - clear indication for prophylactic fixation.

❌ Not mentioning embolization for RCC/thyroid - critical safety step.

❌ Describing short plate instead of long IM nail - wrong implant choice.

❌ Forgetting MDT discussion - metastatic bone disease is never managed by surgeon alone.

❌ Not assessing neurology in spine mets - missing cord compression is unforgivable.

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Document Status: Gold Standard (54/56) Last Updated: 2026-01-10 Evidence Level: High (Level I-II evidence for all major recommendations) Target Examinations: FRCS (Tr&Orth), FRACS, MRCS, Orthopaedic Oncology Fellowship