THA Heterotopic Ossification

Brooker Classification (Most Widely Used)

The Brooker classification is the gold standard for grading HO after THA. It is based on AP pelvis radiograph findings and correlates well with clinical significance.

Della Valle Modification (Research Tool)

This classification subdivides Brooker grades to provide more granular assessment, primarily used in research settings rather than clinical practice.

This modification has NOT shown superior clinical utility compared to standard Brooker classification.

Physical Examination Technique

Non-Operative Management (Brooker I-II, Asymptomatic III)

Most HO does not require treatment. Observation with reassurance is appropriate when HO is asymptomatic or minimally symptomatic.

This approach avoids unnecessary surgery in the majority of patients who have minimal functional impact.

Operative Excision (Symptomatic Brooker III-IV)

Surgical excision is considered when HO causes significant functional limitation and is mature enough for safe removal.

Surgical Outcomes

• ROM improvement: Average 30-50 degree increase in flexion and rotation
• Pain relief: 70-80% report significant pain improvement
• Recurrence: 20-30% with radiation prophylaxis; 50-80% without
• Complications: Nerve injury 2-5% (sciatic most common), infection 1-3%, hematoma 5%
• Patient satisfaction: 80% satisfied if appropriate patient selection

This surgical approach is reserved for patients with significant functional limitation from mature HO.

Surgical Approach Selection

The approach for HO excision depends on the location of the heterotopic bone and the original THA approach used.

Patient Positioning

This positioning allows access to posterior and lateral HO while preserving ability to assess ROM intraoperatively.

Step-by-Step Excision Technique

This systematic technique prioritizes nerve safety while achieving complete HO excision.

Closure Technique and Prophylaxis

Radiation Prophylaxis Timing

Coordinate with radiation oncology pre-operatively to ensure timely prophylaxis - this is the MOST important factor in preventing recurrence.

This protocol ensures optimal prophylaxis compliance while monitoring for complications.

This rehabilitation protocol balances early mobilization with soft tissue protection after excision.

NSAID Prophylaxis (First-Line for Most Patients)

Non-selective NSAIDs and selective COX-2 inhibitors are equally effective at preventing HO. The choice depends on patient risk factors, contraindications, and local availability.

Evidence for NSAIDs

• Efficacy: Reduces severe HO (Brooker III-IV) from 20% to 2-5% in high-risk patients
• Timing critical: Must start within 24 hours - delayed prophylaxis ineffective
• Duration: 6 weeks optimal (shorter duration less effective, longer no additional benefit)
• All NSAIDs equally effective: No single agent superior, choice based on side effect profile
• No effect on osseointegration: Does NOT impair bone-implant interface or fracture healing at standard doses

These prevention strategies work by interrupting the early stem cell differentiation cascade.

Radiation Prophylaxis (Alternative or High-Risk)

Single-dose low-dose radiation therapy is highly effective at preventing HO and is the preferred option when NSAIDs are contraindicated or in very high-risk patients (previous HO, revision with excision).

Radiation Efficacy and Safety

• Efficacy: Equal to NSAIDs (reduces severe HO from 20% to 2-5%)
• No wound complications: Single low dose does NOT impair wound healing
• No increased infection: Multiple studies show no increased infection risk
• Long-term safety: No increased cancer risk at 700cGy dose (too low)
• Gonadal protection: Shielding reduces scatter to acceptable levels
• Combination therapy: NSAIDs + radiation NO additional benefit over single modality

This approach is particularly valuable when NSAIDs cannot be used safely.

High-Risk vs Standard-Risk Patients

Not all THA patients require HO prophylaxis. Risk stratification guides decision-making.

Practice Patterns

• Risk-stratified prescribing: Contemporary practice targets prophylaxis to high-risk hips rather than every THA, reflecting the absence of functional benefit in unselected patients (HIPAID, PMID 16885182)
• Agent choice driven by safety: Selective and non-selective NSAIDs are equally effective, so GI/renal/cardiovascular risk guides selection (Migliorini 2022, PMID 35809109)
• Radiation: Reserved for NSAID contraindications, very high-risk hips, or revision with HO excision
• Trauma exception: In patients with concurrent long-bone fractures, radiation is preferred because indomethacin increases non-union risk (Burd 2003, PMID 12892193)

This risk-based approach optimises prevention while minimising unnecessary medication exposure.

Global Epidemiology (Evidence-Based)

Guideline & Society Positions (Side-by-Side)

Practice Variation

• Agent choice: Selective (COX-2) and non-selective NSAIDs are equally effective, so prescribing is driven by GI, renal and cardiovascular risk rather than anti-HO potency (Migliorini 2022, PMID 35809109).
• NSAIDs vs radiotherapy: Both reduce HO in high-risk hips; some meta-analytic data favour NSAIDs on efficacy while radiation is favoured when NSAIDs are contraindicated or after excision (Shapira 2021, PMID 33736491).
• Trauma caveat: In patients with concurrent long-bone fractures, indomethacin increases non-union risk, so radiation is preferred in this group (Burd 2003, PMID 12892193).
• Approach effect: Direct lateral/anterolateral exposures are generally reported with higher HO rates than posterior approaches, influencing local protocols.