Total Hip Arthroplasty Indications

Total hip arthroplasty (THA) is one of the most successful surgical procedures in modern medicine. The primary indication for THA is end-stage hip arthritis causing pain and disability that has failed conservative management.

Historical perspective:

• Sir John Charnley pioneered modern THA in the 1960s with the low-friction arthroplasty concept
• Cemented metal-on-polyethylene became the gold standard
• Evolution to modular implants, improved bearing surfaces, and minimally invasive techniques
• Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) established 1999 - world-leading registry

Epidemiology in Australia (AOANJRR 2023 data):

Normal hip joint anatomy:

• Ball-and-socket joint with excellent stability and range of motion
• Femoral head (2/3 sphere) articulates with acetabulum (horseshoe-shaped lunate surface)
• Articular cartilage 2-4mm thick, allows load distribution and low-friction movement
• Labrum deepens socket and creates suction seal
• Capsule reinforced by ligaments (iliofemoral, pubofemoral, ischiofemoral)

Pathophysiology of osteoarthritis:

Radiographic changes:

History and physical examination for THA candidacy:

History:

• Pain characteristics: Location (groin vs lateral), severity, progression
• Functional limitation: Walking distance, stairs, ADLs, sleep disturbance
• Previous treatments: Physio, injections, medications, duration and response
• Medical comorbidities: Cardiac, pulmonary, diabetes, immunosuppression
• Patient goals: Expectations for pain relief, function, activity level

Physical examination:

• Gait: Antalgic, Trendelenburg (abductor weakness), leg length discrepancy
• ROM: Flexion, extension, abduction, adduction, internal/external rotation (IR lost first in OA)
• Leg length: Measure true vs apparent LLD (ASIS to medial malleolus)
• Neurovascular: Femoral/dorsalis pedis pulses, sensation, motor function
• Associated pathology: Spine (flexion deformity), knee (referred pain pattern)

Patient-reported outcome measures:

• Oxford Hip Score (0-48, under 30 indicates severe impairment)
• WOMAC (Western Ontario and McMaster Universities Arthritis Index)
• HOOS (Hip disability and Osteoarthritis Outcome Score)
• SF-36 (quality of life measure)

Differential diagnosis of hip-region pain. Before attributing pain to arthritis and offering THA, confirm the pain is genuinely intra-articular hip pain and exclude mimics - a key examiner probe because operating on the wrong source of pain is a classic cause of a dissatisfied "failed" THA.

Imaging studies:

Plain radiographs (essential):

• AP pelvis (standing, weight-bearing, both hips visible)
• Lateral hip (cross-table or frog-leg)
• Findings: Joint space narrowing, osteophytes, sclerosis, cysts
• Measurement: Hip center, leg length, offset

Advanced imaging (selective):

• MRI: Early AVN detection (Stage I), soft tissue pathology, occult fracture
• CT scan: DDH planning, post-traumatic deformity, bone stock assessment
• Nuclear medicine: Bone scan for infection vs loosening differentiation (rare preoperative)

Laboratory investigations:

• FBC: Anemia (may need preoperative iron/EPO)
• UEC: Renal function for NSAID use, perioperative hydration
• HbA1c: If diabetic (target under 8%)
• ESR/CRP: Elevated suggests infection (investigate before elective THA)
• Coagulation studies: If on anticoagulation

Special investigations:

• ECG: All patients over 50 or with cardiac history
• Echocardiogram: If cardiac symptoms or murmur
• Pulmonary function tests: If severe COPD
• Urinalysis: Rule out UTI before elective surgery

Primary indication: End-stage hip arthritis causing pain and functional disability that has failed adequate conservative management.

The Three Pillars of THA Indication:

1. Pain and Disability

   • Pain that affects quality of life (sleep, ADLs, recreation)
   • Functional limitation (walking distance, stairs, getting out of chair)
   • Patient-reported outcome measures (HOOS, WOMAC, Oxford Hip Score) document severity

2. Radiographic Evidence

   • Plain radiographs show joint space loss, osteophytes, sclerosis, cysts
   • Confirms diagnosis but does NOT alone indicate need for surgery
   • Severity on X-ray does not correlate perfectly with symptoms

3. Failed Conservative Treatment

   • At least 6 months of appropriate non-operative management
   • Includes: physiotherapy, weight loss, activity modification, analgesia (NSAIDs, paracetamol), intra-articular injection
   • Patient compliance with conservative measures documented

Specific diagnostic categories:

Special contraindication scenarios:

Patient selection is the single most important determinant of THA outcome.

Ideal THA candidate:

• Age 50-80 years (optimal risk-benefit balance)
• Severe symptomatic hip arthritis (pain, disability)
• Failed adequate conservative trial (6+ months)
• Motivated patient with realistic expectations
• Able to participate in rehabilitation
• Medical comorbidities optimized
• Social support for postoperative period

Preoperative assessment:

Medical optimization:

Dental clearance:

Recent dental infection or poor dentition can lead to bacteremia and hematogenous seeding of prosthetic joint.

Protocol:

• All patients: Dental examination within 6 months of THA
• Active dental infection: Treat first, wait 6 weeks minimum
• Poor dentition, multiple caries: Consider extraction and healing before THA
• Routine dental prophylaxis: Per ADA guidelines (not routinely recommended for most patients, consider high-risk)

MRSA screening and decolonization:

Templating is essential for:

1. Component size prediction (reduces operative time, inventory needs)
2. Leg length restoration planning
3. Offset restoration (abductor moment arm)
4. Identifying anatomical challenges (DDH, previous surgery, deformity)

Required radiographs:

Digital templating process:

Offset restoration:

Special considerations:

• DDH: High hip center, small canal, increased anteversion - may need structural graft, specialized implants
• AVN in young patient: Consider resurfacing vs THA, templating for both
• Previous surgery: Retained hardware, altered anatomy - plan hardware removal approach
• Leg length discrepancy: Preoperative LLD may be longstanding, patient adapted - discuss postoperative expectations

Before proceeding with THA in younger patients, consider alternatives:

Hip resurfacing:

Once popular in young males, now declining in use due to:

• Metal-on-metal bearing concerns (pseudotumor, metallosis, ARMD)
• AOANJRR data shows higher revision rate than THA (especially in women)
• Requires large femoral head (over 50mm), good bone quality
• Contraindicated: Renal impairment, metal allergy, osteoporosis, cysts

Still considered in: Young male athlete, very large femoral head, strong bone, patient counseled about risks

Algorithm

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THA Decision Pathway:

Immediate postoperative management:

Hip precautions (approach-dependent):

• Posterior approach: No flexion over 90°, no adduction past midline, no internal rotation (6-12 weeks)
• Anterior approach: No extension, external rotation, or adduction (6 weeks)
• Lateral approach: Minimal restrictions, avoid extreme abduction initially

Expected outcomes of THA:

Pain relief:

• 90-95% of patients report significant pain improvement
• Most patients pain-free or minimal pain at rest and activity
• Night pain typically completely resolved
• Groin pain may persist in 5-10% (unexplained, may be from spine or soft tissues)

Functional improvement:

• Walking distance increases dramatically (unlimited in most patients)
• Stair climbing normalized
• ADLs (dressing, bathing, shoe tying) significantly easier
• Return to work: 80-90% return to previous work level
• Return to sport: Low-impact sports encouraged, high-impact discouraged

Patient satisfaction:

• 85-90% "very satisfied" with THA outcome
• 5-10% "satisfied with reservations" (ongoing pain, stiffness, LLD)
• Less than 5% "dissatisfied" (persistent pain, complications, unmet expectations)

Implant survival (AOANJRR data):

• 5 years: 97% survival
• 10 years: 95% survival
• 15 years: 93-95% survival (modern implants)
• 25 years: 85-90% survival (projected)

Factors affecting outcome:

Long-term surveillance:

• Annual clinical review first 5 years
• X-rays at 1 year, then every 2-3 years
• Monitor for: pain (loosening, infection), wear, osteolysis
• AOANJRR tracks all Australian THAs for long-term outcomes

Global epidemiology. Osteoarthritis is the commonest indication for THA worldwide. The GBD 2021 study estimated 595 million people had osteoarthritis globally in 2020 (7.6% of the population), a 132% rise in cases since 1990, with hip OA cases projected to increase 78.6% by 2050; high BMI accounts for roughly 20% of the burden. This rising, ageing, increasingly obese population is driving worldwide growth in THA demand.

Major guidelines, side by side. Recommendations are broadly concordant: a structured trial of non-operative care first, then THA for symptomatic end-stage disease refractory to that care. The threshold and emphasis differ.

Registry evidence. National joint registries are the highest-volume source of revision data and consistently agree on the major messages below.

Global practice variation. Fixation philosophy differs by region: cemented and hybrid THA predominate in Scandinavia, the UK and Australia (registry-driven), whereas cementless fixation predominates in the USA and much of Asia. In high-resource settings the debate is bearing surface and approach; in limited-resource settings access, implant availability and cost dominate, and conventional rather than cross-linked polyethylene or cemented implants may be used for economic reasons. Across all systems the indication itself - disabling symptomatic end-stage hip disease that has failed appropriate conservative care - is universal.