Total Hip Replacement - Direct Anterior Approach (DAA)

Primary indication. End-stage hip arthritis that has failed an adequate trial of conservative care (NSAIDs, physiotherapy, weight loss, activity modification and at least one intra-articular corticosteroid injection), with pain and functional limitation affecting quality of life and radiographic joint destruction. Indications by pathology

• Primary osteoarthritis (most common, about 70 percent) - joint-space narrowing, osteophytes, subchondral sclerosis and cysts.
• Avascular necrosis - Ficat-Arlet stage III to IV with femoral head collapse, having failed core decompression or vascularised grafting (causes include corticosteroids, alcohol, SLE, post-traumatic, sickle cell, Gaucher's, idiopathic).
• Inflammatory arthropathies - rheumatoid arthritis with joint destruction, ankylosing spondylitis with hip ankylosis or severe restriction, psoriatic and IBD-associated arthritis.
• Femoral neck fractures - displaced Garden III or IV in the elderly (typically over 65 years), failed fixation, or non-union.
• Failed previous hip surgery - failed hip preservation (periacetabular osteotomy, femoral osteotomy, hip arthroscopy), failed hemiarthroplasty, or revision scenarios. Patient selection for DAA. The approach is a technical choice, not a different operation. Use the table to weigh the DAA against patient factors:

Preoperative planning

• Clinical: document ROM (a flexion contracture affects femoral exposure), measure leg-length discrepancy (true versus apparent), perform a neurovascular examination to record a baseline, and assess previous hip scars.
• Radiographic templating: AP pelvis (include femoral heads, obturator foramina and iliac wings) and a lateral hip (cross-table or frog-leg) with a magnification marker (typically about 20 percent); template the acetabular cup (size and position) and femoral stem (size, neck length, offset) and identify leg-length discrepancy by comparing the lesser trochanters and teardrops.
• Special investigations: CT for complex deformity, DDH or previous fracture malunion; MRI to stage AVN or assess soft tissue; FBC, CRP and ESR if infection is suspected; HbA1c in diabetics (optimise to under 7 percent ideally). Consent specifically for bleeding and transfusion, infection, dislocation, leg-length discrepancy, lateral thigh numbness (LFCN), periprosthetic fracture, venous thromboembolism, and the possibility of future revision. Setup. Supine on a standard or radiolucent table with an extension attachment; secure the pelvis with padded posts to prevent rotation; C-arm brought in from the contralateral side. The operative leg must be free to extend, externally rotate and adduct off the side of the table.

The goal is to expose the hip through the true internervous interval between tensor fascia lata (TFL, superior gluteal nerve) and sartorius (femoral nerve), remove the arthritic femoral head, implant the acetabular cup and femoral stem in the correct position, and restore offset and leg length - all without detaching any muscle. The exposure is laid out in full below. The internervous interval and the structures you must respect. Deep to the TFL-sartorius interval lies rectus femoris (reflected head from the anterior capsule, straight head from the AIIS). The ascending branch of the lateral femoral circumflex artery (LFCA) runs 2 to 3 cm distal to the capsule, deep to rectus femoris, and must be controlled early. Know the five structures at risk before you cut:

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Rehabilitation - the DAA allows immediate weight-bearing as tolerated with no movement restrictions. | Phase | Timing | Weight-bearing / restrictions | Milestones | |-------|--------|-------------------------------|------------| | Day 0 | Day of surgery | WBAT, no precautions | Mobilise same day; frame or crutches; start VTE prophylaxis | | Early | Days 1 to 2 | WBAT, no precautions | Stairs; discharge when medically stable and safe | | Week 2 | 2 weeks | WBAT | Wound check; suture or staple removal; progress from frame to crutches to stick | | Week 6 | 6 weeks | WBAT | X-ray (AP pelvis, lateral hip); return to driving if safe (right hip: able to emergency-stop) | | Month 3 | 3 months | Full | Low-impact sport (golf, swimming, cycling); return to sedentary or light work | | Month 6+ | 6 months | Full | Heavy manual work; impact sport controversial and not universally recommended | | Surveillance | Years 1, 3, 5, 10 then 5-yearly | - | X-ray for wear, loosening, osteolysis, infection | VTE prophylaxis. Extended pharmacological prophylaxis for elective THR, commonly 28 to 35 days (AAOS / NICE / ACCP-aligned): LMWH (enoxaparin 40 mg daily), a low-dose DOAC (rivaroxaban 10 mg daily, apixaban 2.5 mg twice daily), or aspirin in selected low-risk patients. Combine with mechanical prophylaxis (intermittent pneumatic compression) and early mobilisation. Routine intra-operative tranexamic acid reduces blood loss and transfusion (strong cross-guideline support). Complications

Epidemiology. Primary osteoarthritis is the commonest indication for total hip replacement (about 70 percent). AVN, inflammatory arthropathies and femoral neck fractures make up most of the remainder. Across major registries the 10-year cumulative revision rate for primary OA THR is about 4 to 6 percent, rising to about 8 to 10 percent for fracture indications and 15 to 20 percent re-revision at 10 years after revision THR. Classifications referenced in DAA THR

What the evidence shows. The RCT and meta-analysis evidence converges on a consistent message: the DAA gives a genuine early-recovery advantage in the first 6 to 12 weeks and more reliable cup placement, but at the cost of a large excess of (sensory) LFCN injury, and - against the lateral approach in particular - a higher periprosthetic-fracture and nerve-injury signal during the learning curve. Long-term survivorship is equivalent across approaches.

• Barrett (2013, with 5-year follow-up 2019) - single-surgeon RCT of 87 hips: DAA had lower day-1 pain and better early function, converging with the posterior approach by 3 to 12 months; at 5 years there was no difference in Harris Hip Score, UCLA activity, HOOS-Jr or survivorship.
• Mjaaland (2015) - Norwegian RCT: DAA versus direct lateral showed lower markers of muscle damage, inflammation and pain with DAA - the mechanistic basis for the early advantage.
• Yang (2020) and Huang (2021) meta-analyses - DAA versus posterior: lower early pain and more cups in the Lewinnek safe zone, with a large excess of LFCN injury; DAA versus lateral: better component accuracy and abductor function but higher dislocation, periprosthetic-fracture and nerve-injury rates.
• Sheth (2015), Kaiser registry - anterior and anterolateral approaches had a lower adjusted dislocation risk (DAA hazard ratio about 0.44 versus posterior) with no increase in revision risk. Global registry and guideline evidence. AOANJRR, NJR (England, Wales, Northern Ireland), AJRR (USA) and the Nordic registries are concordant: 10-year survivorship for primary OA THR is about 94 to 96 percent across all approaches; cemented femoral fixation has higher survivorship in the elderly (especially over 75 years and in fracture indications); a 36 mm head or dual-mobility reduces dislocation where the cup allows; and surgical approach is not an independent driver of long-term revision - surgeon volume and implant choice dominate. Named-society guidance (AAOS, NICE TA304, BOA/BOAST, EFORT consensus) does not recommend any single approach as superior for routine primary THR and emphasises shared decision-making, surgeon experience and ODEP-benchmarked implants. Reasons for revision across registries, in order: loosening or lysis (30 to 35 percent), dislocation or instability (20 to 25 percent), infection (15 to 20 percent), periprosthetic fracture (10 to 15 percent), liner or head wear (5 to 10 percent). Outcome measures and satisfaction. Oxford Hip Score rises from a pre-operative average of 15 to 20 to a post-operative average of 38 to 42 (minimum clinically important difference 5 points); WOMAC improves in all subscales, most dramatically in pain; and EQ-5D shows that THR produces one of the largest quality-of-life gains of any elective surgery (about 0.3 to 0.4 on a 0 to 1 scale). Overall satisfaction is 85 to 90 percent at one year, with dissatisfaction most commonly driven by residual pain, leg-length discrepancy or unmet expectations. Bearing surfaces in the young patient. In younger, high-demand patients, hard-on-soft bearings using highly cross-linked polyethylene against a ceramic (or oxidised-zirconium) head give very low wear with no squeaking and no ceramic-fracture risk, and are the most widely used choice internationally. Ceramic-on-ceramic offers very low wear but carries a small risk of squeaking (about 1 to 5 percent) and rare catastrophic fracture (under 0.1 percent). Metal-on-metal is now largely abandoned because of adverse local tissue reaction.