Total Hip Replacement - Direct Anterior Approach (DAA/Hueter)

Ideal Indications for DAA

Primary Indications

• Primary hip osteoarthritis - especially younger, active patients who benefit from rapid recovery and no precautions
• AVN femoral head - all stages requiring arthroplasty
• Inflammatory arthritis (RA, AS) - when medical management fails
• Post-traumatic arthritis - following acetabular or femoral neck fracture
• Failed osteotomy or proximal femoral fracture malunion

Ideal Patient Characteristics

• BMI less than 35 - obesity increases difficulty of femoral exposure significantly
• Non-muscular build - muscular thighs/buttocks make femoral exposure very challenging
• Good bone quality - osteoporotic bone increases fracture risk during broaching
• Standard anatomy - not severe protrusio or dysplasia (more difficult acetabular exposure)
• High dislocation risk - cognitive impairment, Parkinson's disease, seizure disorder, substance abuse
• Bilateral disease - can perform bilateral single-stage DAA safely (both hips supine)
• Occupation requiring rapid return - athletes, physical workers who benefit from no precautions

Relative Contraindications

• Severe obesity (BMI greater than 40) - very difficult femoral exposure, high complication rates
• Severe protrusio - difficult to ream without medial wall perforation via anterior approach
• DDH with high dislocation - limited femoral visualization for complex reconstruction
• Previous anterior hip surgery - scarring in interval complicates approach
• Heterotopic ossification bridging anterior structures - prevents internervous plane development
• Severe hip flexion contracture - prevents leg extension for femoral access
• Very muscular patients - bodybuilders, powerlifters have difficult femoral exposure

DAA vs Posterior Approach - Selection Criteria

Choose DAA when:

• Patient prioritizes rapid recovery and no precautions
• High dislocation risk (posterior instability concerns)
• Bilateral procedures planned
• Younger active patient
• Non-obese, non-muscular build

Choose Posterior when:

• Severe obesity or muscular build
• Complex acetabular reconstruction needed
• DDH or protrusio requiring extensile exposure
• Surgeon early in learning curve and complex case
• Previous anterior hip surgery

Anatomical Basis of DAA

First Internervous Plane (Superficial)

Lateral: Tensor Fascia Lata

• Innervation: Superior gluteal nerve (L4-S1)
• Origin: Anterior iliac crest, ASIS
• Insertion: Iliotibial tract
• Function: Hip abduction, flexion, internal rotation
• Appearance: Tight, broad muscle mass laterally

Medial: Sartorius

• Innervation: Femoral nerve (L2-L4)
• Origin: ASIS
• Insertion: Pes anserinus (medial proximal tibia)
• Function: Hip flexion, abduction, external rotation; knee flexion
• Appearance: Thin, rope-like muscle medially

Second Internervous Plane (Deep)

Medial: Rectus Femoris

• Innervation: Femoral nerve (L2-L4)
• Origin: AIIS (straight head), acetabular rim (reflected head)
• Insertion: Patella via quadriceps tendon
• Function: Hip flexion, knee extension
• Note: Vulnerable to avulsion if excessive medial retraction

Lateral: Gluteus Medius

• Innervation: Superior gluteal nerve (L4-S1)
• Origin: External ilium between iliac crest and posterior/anterior gluteal lines
• Insertion: Greater trochanter (lateral facet)
• Function: Hip abduction, anterior fibers internally rotate
• Note: Contains superior gluteal nerve - avoid proximal extension

Critical Vascular Anatomy

Lateral Femoral Circumflex Artery (LFCA)

• Origin: Profunda femoris (deep femoral artery)
• Branches:
  • Ascending branch: Runs between rectus femoris and vastus lateralis toward greater trochanter - CROSSES SURGICAL FIELD and must be ligated/cauterized
  • Transverse branch: To hip capsule
  • Descending branch: Along vastus lateralis
• Injury: Persistent bleeding if not controlled

Femoral Vessels

• Location: Medial to surgical field beneath inguinal ligament
• Femoral artery lateral, femoral vein medial (within femoral sheath)
• Protection: Keep retraction lateral; medial capsular retractor placement should not be too deep or medial
• At risk: If medial retractor placed blindly or excessively medial

Neural Anatomy

Lateral Femoral Cutaneous Nerve (LFCN)

• Course: Emerges under/through inguinal ligament medial to ASIS, runs subcutaneously over sartorius
• High variability: May run 1-3cm medial to ASIS, or up to 2-3cm lateral
• Sensory distribution: Anterolateral thigh from hip to knee
• Injury: Meralgia paresthetica (10-20% DAA, most temporary)

Femoral Nerve

• Course: Descends in groove between psoas and iliacus, passes under inguinal ligament lateral to femoral artery
• Branches to: Iliopsoas, sartorius, rectus femoris, vastii
• Protection: Medial retraction of sartorius/rectus protects nerve (contained with muscles)
• Injury risk: <0.5% with proper technique

Superior Gluteal Nerve

• Course: Exits pelvis through greater sciatic foramen above piriformis, runs between gluteus medius and minimus
• Innervates: Gluteus medius, gluteus minimus, tensor fascia lata
• At risk: If approach extended proximally beyond greater trochanter or excessive lateral retraction
• Injury: Abductor weakness, Trendelenburg gait

Capsular Anatomy

Anterior Capsule

• Thickest anteriorly - provides primary flexion/external rotation stability
• Iliofemoral ligament (Y-ligament of Bigelow): Strongest capsular ligament, from AIIS to intertrochanteric line
• Pubofemoral ligament: From pubis to intertrochanteric line, limits abduction
• Posterior capsule remains INTACT in DAA - this is why dislocation rate so low
• Capsulotomy: Can be T-shaped, longitudinal, or anterior capsulectomy

Detailed Operative Steps

Step 1: Patient Positioning and Table Setup

Position patient SUPINE on specialized DAA table (Hana table, PRO-FX table, or similar) or standard table with hip extension capability. Secure pelvis with positioning device to prevent rotation during femoral preparation. Position contralateral leg in flexion, abduction, and external rotation using leg holder to allow operative leg extension later. If using standard table, ensure ability to extend operative leg off side of table and provide anterior support for femoral elevation. Prepare and drape from umbilicus to knee, including entire leg mobile in field.

Step 2: Surface Landmarks and Skin Incision

Palpate ASIS and mark. Incision starts 2-3cm DISTAL and 2cm LATERAL to ASIS. Extend 8-10cm distally and laterally along line from ASIS toward lateral patella. Incision can be oblique (following skin lines) or longitudinal (along fascial plane). This is smaller than posterior (10-12cm) or lateral (12-15cm) approaches. Incise skin with knife. Develop subcutaneous tissue with electrocautery or dissection, being aware of potential LFCN location (highly variable - may be 1-3cm medial or lateral to ASIS in subcutaneous fat).

Step 3: Fascia Lata Incision and Identify First Intermuscular Interval

Incise fascia lata in line with skin incision using electrocautery. Identify TENSOR FASCIA LATA laterally (appears as tight, broad muscle mass with vertical fibers) and SARTORIUS medially (thin, rope-like muscle that can be palpated as a cord). This is the FIRST INTERNERVOUS PLANE: TFL innervated by superior gluteal nerve (L4-S1) versus sartorius innervated by femoral nerve (L2-L4). Use blunt dissection (finger or sponge stick) to develop this interval. Lateral femoral cutaneous nerve may be visualized in this superficial dissection - attempt to preserve if seen, but injury often occurs before nerve identified due to variable anatomy.

Step 4: Deep Dissection and Second Internervous Plane

Retract TFL laterally and sartorius medially using self-retaining or handheld retractors. Proceed deeper through fatty layer to identify the deeper muscle layer. The deeper interval is between RECTUS FEMORIS (medial, part of quadriceps, innervated by femoral nerve) and GLUTEUS MEDIUS (lateral, innervated by superior gluteal nerve) - this is the SECOND INTERNERVOUS PLANE. Ascending branch of lateral femoral circumflex artery (LFCA) crosses surgical field between rectus femoris and vastus lateralis at this level - identify and LIGATE with ties or CAUTERIZE with bipolar electrocautery before proceeding (prevents persistent bleeding). Place Hohmann retractors: medial retractor over femoral neck (protects medial structures), lateral retractor over gluteus medius/acetabular rim. May need to release some rectus reflected head attachment to expose anterior capsule fully.

Step 5: Capsule Exposure and Anterior Capsulotomy

Expose anterior hip capsule by retracting rectus femoris medially and gluteus medius laterally. Hip should be in neutral position. Place capsular retractors: medial Hohmann retractor over femoral neck (curved, protects medial structures), lateral Hohmann retractor over acetabular rim/anterior capsule. Identify anterior capsule and iliofemoral ligament (Y-ligament). Perform ANTERIOR CAPSULOTOMY using electrocautery: can do longitudinal capsulotomy along axis of femoral neck, or T-shaped capsulotomy (longitudinal plus transverse limb), or anterior capsulectomy for better exposure. Some surgeons preserve capsule for later repair, others excise for visualization. Extend capsulotomy proximally and distally to expose femoral neck and head-neck junction. Tag capsule with sutures if planning repair at closure.

Step 6: Femoral Neck Osteotomy

Identify femoral head-neck junction by palpation and visualization. Make neck osteotomy at templated level (typically 1cm above lesser trochanter for standard stems, may adjust for short stems or level based on templating). Use oscillating saw with blade perpendicular to neck axis. External rotation of leg improves visualization of anterolateral femoral neck. Protect soft tissues with retractors during sawing. Cut should be horizontal to preserve calcar bone stock for stem support. After first cut, may need second cut if cancellous bone of head prevents removal - make second cut more proximally on head. Avoid excessively distal cut (causes shortening) or excessively proximal cut (causes lengthening and may complicate head removal).

Step 7: Femoral Head Removal and Acetabular Exposure

Remove femoral head using corkscrew or head extraction device. May need to disimpact head by external rotation and gentle leverage - avoid excessive force causing femoral fracture. After head removal, clear remaining capsule and labrum from acetabular rim using electrocautery and/or rongeur. Remove labrum circumferentially. This provides excellent acetabular visualization - a KEY ADVANTAGE of DAA approach as surgeon looks directly into acetabulum from anatomic position. Place retractors around acetabulum: anterosuperior Hohmann (at 12 o'clock), posterosuperior Hohmann (at 10-11 o'clock position over posterior wall), and inferior Hohmann or bent Hohmann in obturator foramen (6 o'clock). Identify transverse acetabular ligament at inferior margin - key landmark for determining anatomic version and inclination during reaming/cup insertion.

Step 8: Acetabular Reaming

Excellent acetabular visualization in DAA with patient supine. Identify fovea (anatomic center). Start with smallest reamer (typically 44-46mm) to identify anatomic center and version. Ream toward fovea - aim to restore anatomic center, avoid excessive medialization (weakens medial wall) or lateralization (uncovers cup). Sequential reaming in 2mm increments to subchondral bone - feel and hear change in resistance as you reach subchondral bone. Look for 'crescent sign' of bleeding subchondral bone superiorly indicating correct reaming depth. Final reamer size should be 1-2mm smaller than planned cup size to achieve press-fit. Assess for posterior wall deficiency during reaming. Clear debris from acetabulum with suction and pulsatile lavage. Dry acetabulum with sponge before cup insertion.

Step 9: Acetabular Cup Insertion

Insert hemispherical acetabular cup in LEWINNEK SAFE ZONE: 40-45 degrees inclination (abduction), 15-20 degrees anteversion. DAA advantage: anatomic positioning - with patient supine, the anterior pelvic plane (defined by ASIS and pubic tubercle) is perpendicular to floor, making cup orientation more intuitive than lateral positioning where pelvic rotation affects version assessment. Use cup introducer/impactor. Press-fit cup 1-2mm larger than final reamer size. Impact cup into position - feel and hear change in pitch when fully seated. Assess stability - should be rigid with no motion. Add supplemental screw fixation posterosuperiorly if poor initial stability, poor bone quality, or surgeon preference. Typically use 1-2 screws in posterosuperior quadrant. Avoid anteroinferior screws (external iliac vessels/obturator vessels at risk). Insert liner - may be polyethylene, ceramic, or metal depending on bearing surface chosen.

Step 10: Femoral Exposure - Most Technically Demanding Step

THIS IS THE MOST TECHNICALLY DEMANDING STEP OF DAA AND WHERE LEARNING CURVE IS STEEPEST. To expose proximal femur for preparation, manipulate operative leg into extension, external rotation, and adduction. If using specialized DAA table, release operative leg and allow it to extend, externally rotate, and adduct off side of table using table mechanisms. If using standard table, hyperextend leg off side of table with assistant support or leg positioner. Place anterior femoral neck retractor (elevator or curved retractor) under proximal femur to lift it anteriorly into the wound - this effectively translates the femoral canal toward the incision. May need to release remaining anterior capsule attachments to greater trochanter to allow femoral mobilization. Goal is to deliver piriformis fossa entry point into wound for visual or palpable access. If exposure inadequate despite proper technique, may need to convert to extensile approach (extend proximally) or different approach.

Step 11: Femoral Preparation and Broaching

Once proximal femur is elevated into wound, identify piriformis fossa entry point by palpation or visualization. Entry point is tip of greater trochanter in line with femoral canal axis. Insert box chisel or starter reamer with handle directed slightly LATERAL (valgus orientation, approximately 5-10 degrees from vertical) to prevent varus stem positioning. Open femoral canal and create starting point. Sequential broaching from smallest size with increasing sizes. Broach to cortical contact circumferentially with good rotational and axial stability. Aim for approximately 10-15 degrees anteversion - can assess by forearm position parallel to transverse acetabular ligament or by comparison to contralateral leg position. In DAA, femoral preparation is more challenging than posterior approaches due to limited direct visualization of proximal femur - much of the work is by feel and fluoroscopy (if used). Higher risk of malposition or fracture during learning curve compared to posterior approach. Final broach should be stable in all planes without impaction-related fracture.

Step 12: Trial Reduction and Stability Testing

Insert trial femoral stem to same depth and version as final broach. Select trial femoral head (typically start with +0 or +3mm offset and adjust based on stability and leg length). Return leg to neutral position on table. Reduce hip by bringing leg into slight flexion and gently guiding head into socket - should reduce smoothly. Assess leg length clinically: palpate greater trochanters bilaterally for symmetry, compare knee heights and patella heights to opposite side, assess pelvic obliquity. STABILITY TESTING: (1) Extension with external rotation (tests anterior stability - less relevant for DAA with intact posterior structures); (2) 90 degrees flexion with internal rotation and adduction (tests posterior stability - should be very stable in DAA). Note: In DAA with intact posterior capsule and short external rotators, dislocation risk is very low (less than 0.5%), so aggressive stability testing less critical than in posterior approaches. Assess impingement-free range of motion in flexion, extension, abduction, adduction, rotation. If leg length incorrect, adjust head/neck length or stem depth. If unstable (rare), consider larger head, more anteverted stem, or higher offset head.

Step 13: Final Implant Insertion

After satisfactory trial reduction with appropriate stability and leg length, extend leg again into same position as femoral preparation for final component insertion. Dislocate hip and remove trial components (trial head, trial stem). Insert final femoral stem - can be cementless press-fit or cemented depending on bone quality and implant choice. If cementless, insert stem to same depth and version as final broach with impaction. If cemented, clean and dry femoral canal thoroughly with pulsatile lavage, suction, and canal brush. Dry with suction and sponge. Insert cement restrictor 1-2cm distal to final stem tip. Pressurize cement retrograde with cement gun. Insert stem in correct version and depth while cement still dough-like. Hold position until cement hardens. Insert final modular femoral head with correct size (match trial head size) and neck length (match trial offset). Ensure Morse taper fully seated with impaction. Return leg to neutral position on table. Reduce hip - should reduce easily and smoothly. Perform final stability check identical to trial stability testing. Assess final range of motion in all planes without impingement. Irrigate wound copiously with pulsatile lavage (minimum 3L). Suction debris.

Step 14: Closure

Return leg to neutral position with hip reduced. Ensure meticulous hemostasis - may need to revisit and control ascending LFCA branches if not already done, or any capsular bleeding. CAPSULE: Capsular repair in DAA is controversial. Some surgeons repair anterior capsule with interrupted sutures to iliofemoral ligament remnant to potentially improve stability and reduce anterior dislocation risk, though dislocation rates are already very low (less than 0.5%). Other surgeons do not repair capsule, citing no clear evidence of benefit and faster closure. If repairing, use strong absorbable suture (0 or 1 Vicryl/PDS). Close fascia lata with running or interrupted absorbable suture (0 or 1 Vicryl). Subcutaneous layer closure with 2-0 Vicryl. Skin closure with staples, subcuticular suture, or skin glue based on preference. Apply sterile dressing. No drain typically needed unless significant bleeding or high-risk patient.

Step 15: Post-Operative Protocol and Mobilization

NO HIP PRECAUTIONS required - this is a major patient advantage of DAA. Unlike posterior approach (precautions against flexion greater than 90 degrees, adduction, internal rotation for 6-12 weeks) or lateral approach (precautions against adduction), DAA patients can immediately flex hip beyond 90 degrees, cross legs, tie shoes, sit in low chairs, etc. Mobilize with physiotherapy on post-operative day 1. Weight bearing as tolerated immediately with assistive device for comfort. Full range of motion allowed immediately due to intact posterior structures and very low dislocation risk (less than 0.5%). DVT prophylaxis per institutional protocol (typically aspirin, LMWH, or DOACs for 4-6 weeks). Physical therapy for strengthening, gait training, and functional mobility. Most patients discharge home day 1-2 (shorter hospital stay than posterior/lateral approaches in many studies). Post-operative radiographs: immediate post-op AP pelvis and lateral hip to assess component position, then typically 6 weeks, 3 months, 1 year, and annually thereafter. Educate patient that while no precautions required, general fall prevention and safety still important.

Evidence-Based Outcomes for DAA

Dislocation Rates - Key Advantage

• Meta-analyses: DAA dislocation rate 0.3-0.8% vs 2-5% posterior approach
• Mechanism: Intact posterior capsule and short external rotators provide stability
• Clinical significance: Allows NO hip precautions, major quality of life benefit
• Caveat: Anterior dislocation can occur with poor cup positioning (excessive anteversion)

Early Recovery and Function

• Hospital stay: 0.5-1 day shorter with DAA vs posterior in multiple studies
• Early mobilization: Faster ambulation and stairs at 2-6 weeks (less difference by 12 weeks)
• Pain: Some studies show less early pain (possibly related to muscle-sparing technique)
• Return to activities: Faster return to driving, ADLs in first 6-12 weeks
• 6-12 month outcomes: Most studies show NO significant difference in function scores (HOOS, HHS, WOMAC)
• 1-2 year outcomes: Equivalent functional outcomes across all approaches

Learning Curve and Complications

• Learning curve: Approximately 100 cases to achieve complication rates equivalent to experienced surgeons
• Early surgeon complications (first 50 cases):
  • Femoral fracture: 5-10% (vs less than 1% after 100 cases)
  • Conversion to extensile/alternative approach: 3-5%
  • Longer operative time: 20-40 minutes longer during learning curve
• LFCN injury: 10-20% overall, most temporary (60-80% resolve by 3-6 months), 2-5% permanent meralgia paresthetica
• Femoral nerve injury: Less than 0.5% (lower than sciatic nerve injury in posterior approaches 1-3%)

Revision and Long-Term Outcomes

• Aseptic loosening: Equivalent to other approaches at 5-10 years (98-99% survival)
• Infection: Similar rates 0.5-1% across approaches
• Revision for instability: Lower with DAA (0.1-0.3%) vs posterior (0.5-2%)
• Periprosthetic fracture: Slightly higher Vancouver B fractures reported in some DAA series (possibly related to learning curve or technique)
• Registry evidence (global): Large joint registries (AOANJRR Australia, NJR England & Wales, AJRR USA) show the DAA has grown to roughly 10-25% of primary THAs in many high-income settings, with all-cause revision broadly equivalent to the posterior approach at 5-10 years; registry signal of lower revision for dislocation but a small early signal of femoral component loosening/periprosthetic fracture in some cohorts

Cup Positioning Accuracy

• Lewinnek safe zone: Some studies suggest higher proportion of cups in safe zone with DAA (related to supine positioning and anatomic landmarks)
• Pelvic tilt: Supine position eliminates pelvic tilt variability seen in lateral decubitus
• Version control: Anterior pelvic plane perpendicular to floor aids version assessment
• Caveat: Still requires proper technique and landmarks - malposition can occur

Cost and Efficiency

• Operative time: 10-30 minutes longer during learning curve, equivalent when experienced
• Specialized table: A dedicated DAA traction/extension table (Hana, PRO-FX and similar) is a significant capital investment; the approach can also be performed on a standard table with a femoral elevator and an experienced assistant
• Hospital stay: Shorter length of stay may offset equipment costs
• Readmission: Similar readmission rates across approaches (3-5% at 90 days)

Patient-Reported Outcomes

• Satisfaction: High satisfaction across all approaches (90-95% satisfied)
• Cosmesis: Smaller scar appreciated by patients in some surveys
• Precautions: Patients highly value NO precautions in DAA (improved quality of life, less anxiety)
• Forgotten joint score: Some studies show better early forgotten joint scores with DAA (less difference long-term)

Key Evidence

Comprehensive Complication Analysis

Conversion to Alternative Approach

• Incidence: 1-5% during learning curve (first 50 cases), less than 1% when experienced
• Reasons: Inadequate femoral exposure (most common - obese, muscular, stiff hip), intraoperative fracture requiring different fixation, unexpected acetabular pathology (severe protrusio, tumor), equipment failure
• Options: Convert to lateral approach (extend proximally, split abductors), convert to posterior approach (turn patient), extensile anterior approach (T-extension or release gluteus medius)
• Prevention: Proper patient selection, avoid DAA in very obese (BMI greater than 40) or severe protrusio cases during learning curve