Direct Anterior Approach Total Hip Arthroplasty (DAA THA)

Step 1: Patient positioning supine on OR table, operative side at table edge

Patient positioning supine on OR table, operative side at table edge: Standard OR table or specialized DAA table (allows hyperextension). Patient supine, operative hip at edge of table to allow extension/adduction for femoral exposure. Non-operative leg: abducted and slightly flexed (some tables have leg holder/split configuration). Both legs prepared into sterile field (allows comparison for leg length). Ensure ability to extend hip fully and adduct across midline (test before draping). Fluoroscopy access confirmed (C-arm from contralateral side for AP pelvis)

Step 2: Palpate bony landmarks

Palpate bony landmarks: ASIS, AIIS, greater trochanter, femoral artery: Mark ASIS (prominent anterior superior iliac spine). Palpate AIIS 20-30mm distal and medial to ASIS (rectus femoris direct head origin). Palpate greater trochanter laterally (reference for incision length). Palpate femoral artery pulse in groin crease (stay lateral to vessels). Internervous interval: 20-40mm lateral to femoral artery, corresponds to TFL-sartorius interval

Step 3: Skin incision

Skin incision: start 2-3cm lateral and distal to ASIS, extend distally 8-12cm: Incision orientation: longitudinal (parallel to TFL/femoral shaft) or slightly oblique (toward lateral femoral shaft). Length 8-12cm for primary THA (can extend if needed). Incise through skin and subcutaneous fat. Identify and cauterize crossing superficial vessels. Expose fascia overlying TFL laterally and sartorius medially. Identify interval between muscles (slight depression between TFL and sartorius)

Step 4: Develop interval between TFL (lateral) and sartorius/rectus femoris (medial)

Develop interval between TFL (lateral) and sartorius/rectus femoris (medial): Identify fascia overlying TFL laterally (shiny, thick). Incise fascia just lateral to TFL (over muscle belly, not medial edge where LFCN crosses). Bluntly develop interval between TFL (retract laterally) and sartorius/rectus femoris complex (retract medially). This is internervous plane (TFL = superior gluteal nerve, sartorius = femoral nerve). Interval relatively avascular, contains loose areolar tissue. Develop interval from superficial (subcutaneous) to deep (hip capsule). Protect LFCN which crosses field medially (runs on deep surface of TFL or in interval) - identify if visible (thin white nerve 2-3mm diameter), protect with gentle retraction or release if tethering

Step 5: Deepen dissection to hip capsule, release rectus femoris if needed for exposure

Deepen dissection to hip capsule, release rectus femoris if needed for exposure: Continue blunt dissection deep between TFL (lateral) and sartorius/rectus (medial). Ascending branch of LFCA encountered on anterior capsule - identify and cauterize or ligate to prevent bleeding (runs longitudinally on capsule, 1-2mm diameter). Expose anterior hip capsule from acetabular rim (superiorly) to femoral neck (inferiorly). In muscular patients or tight hips, rectus femoris (direct head from AIIS, reflected head from acetabular rim) may obscure exposure - release direct head from AIIS with diathermy or sharp dissection, tag for later repair if desired. Reflected head usually left attached unless extensive acetabular exposure needed

Step 6: Capsulotomy - T-shaped or H-shaped capsular incision for exposure

Capsulotomy - T-shaped or H-shaped capsular incision for exposure: Perform capsulotomy to expose femoral head-neck junction and acetabular rim. Options: T-shaped (vertical incision along femoral neck, transverse at base), H-shaped (two vertical, connected by horizontal), or box/rectangular capsulectomy (excise anterior capsule). Tag capsular flaps with sutures if planning repair. Expose femoral head-neck junction (neck cut location) and anterior/superior acetabular rim. Some surgeons excise capsule (faster, no repair needed), others preserve for closure (theoretical stability benefit but no clear evidence)

Step 7: Dislocation and femoral neck osteotomy

Dislocation and femoral neck osteotomy: Externally rotate leg, extend hip slightly, apply anterior force to femoral head (assistant or specialized retractors). Head should deliver anteriorly into wound with gentle force (if difficult, release more capsule or check for osteophytes). Perform femoral neck osteotomy using oscillating saw at predetermined level (templating: typically 10mm above lesser trochanter, adjust for head size and leg length plan). Cut perpendicular to neck axis or slightly oblique. Protect soft tissues with retractors. Remove femoral head with corkscrew or Kocher clamp. Measure head size, save head for autograft if needed

Step 8: Acetabular exposure with specialized retractors, protect femoral nerve medially

Acetabular exposure with specialized retractors, protect femoral nerve medially: Place specialized retractors to expose acetabulum: 1) Anterior/superior retractor (double-pronged or curved blade) on anterior rim/AIIS area (retracts rectus and TFL superiorly), 2) Inferior retractor on inferior/medial rim (over obturator internus or ischium - careful placement, MUST be on bone not soft tissue to protect femoral nerve 40-60mm medially), 3) Lateral retractor on lateral rim/GT area (retracts femur and vastus). Confirm 360° rim visualization. Adequate retraction critical for reaming/cup placement - more difficult than posterior approach due to anterior access angle

Step 9: Acetabular preparation

Acetabular preparation: labrum excision, reaming, cup insertion (same as posterior approach): Remove labrum and osteophytes to expose true acetabular rim (transverse ligament marks inferior rim and fovea). Sequential reaming from small to final size (templated size), ream to bleeding subchondral bone (Christmas tree sign), medialize to anatomic center of rotation. Final reamer = cup size minus 1-2mm (press-fit). Insert cup at 40° ± 5° inclination, 15-25° anteversion (Lewinnek safe zone). Assess press-fit stability (scratch test, levering). Add screws if needed in safe zones (posterior-superior, anterior-superior). Insert liner, confirm locking

Step 10: Femoral exposure

Femoral exposure: hyperextend hip, externally rotate, adduct across midline: Release retractors from acetabulum. Position leg for femoral exposure: 1) Hyperextend hip (bring proximal femur anterior, hang leg off table edge or use table-mounted femoral elevator), 2) Externally rotate to 90° (brings posterior femur into wound), 3) Adduct across midline (relaxes soft tissues, improves access). Specialized DAA tables facilitate positioning with hyperextension and leg holders. Standard tables: assistant holds leg, or femoral elevator device hooks around proximal femur to lift. Goal: bring proximal femur anteriorly and superficially into wound for broaching

Step 11: Femoral canal preparation

Femoral canal preparation: open canal, sequential broaching to metaphyseal fill: Identify entry point on piriformis fossa or GT tip (depends on stem design: straight vs anatomic). Open canal with box chisel directed along femoral axis (slight anterior/lateral). Insert sequential broaches starting small, advance incrementally until achieve: 1) Rotational and axial stability, 2) Appropriate seating level vs neck cut, 3) Metaphyseal fill/cortical contact. Final broach size = final stem size. Version: control stem anteversion during broaching (typically 10-15° AF target, assess by knee position when broach stable)

Step 12: Trial reduction

Trial reduction: assess leg length, offset, stability with trial components: Insert trial stem and trial head (matched to final sizes). Reduce hip (bring leg back to neutral position: extension, neutral rotation). Assessment: 1) Leg length - compare to contralateral leg (both legs in same plane supine, easier than lateral position), use sterile ruler/calipers, measure from fixed pelvic landmark (ASIS or pubis) to medial malleolus, compare heel height, 2) Offset - assess abductor tension (firm not tight), 3) ROM - flexion 110°, IR/ER, 4) Stability - flexion 90° + IR (anterior approach stable in this position unlike posterior), extension + ER. Adjust if needed (head size, stem size/offset)

Step 13: Final femoral component insertion, head impaction, reduction, stability check

Final femoral component insertion, head impaction, reduction, stability check: Remove trial components. CEMENTLESS: clean canal, insert final stem in same trajectory/rotation as final broach, impact to predetermined level (usually flush with neck cut), confirm seating. CEMENTED: clean canal, dry, restrictor, cement gun retrograde pressurization, insert stem in doughy phase, hold position until polymerization. Insert final femoral head (clean/dry trunnion, align head, impact firmly until fully seated, check no gap). Reduce hip, confirm stable reduction with ROM testing

Step 14: Closure

Closure: capsule (optional), TFL fascia, subcutaneous, skin, no drains usually: If capsule preserved: repair capsular flaps with absorbable suture (restore anterior capsular integrity). Most surgeons excise capsule and don't repair (low dislocation rate without capsular repair in DAA, posterior capsule intact provides stability). Close TFL fascia with absorbable suture (restore muscle envelope). Subcutaneous layer closure (2-0 Vicryl). Skin: staples or subcuticular suture. Drains: not routinely used in DAA (less soft tissue dissection vs posterior/lateral approaches, lower bleeding). Waterproof dressing

Step 15: Post-operative protocol

Post-operative protocol: immediate mobilization, no hip precautions (DAA advantage): Post-operative advantages of DAA: 1) No formal hip precautions needed (preserved posterior capsule and abductors means flexion/adduction/IR not at-risk position unlike posterior approach), 2) Immediate mobilization (same-day PT, weight-bearing as tolerated if stable fixation), 3) Faster recovery (less pain, shorter LOS in some studies, quicker return to function - though evidence mixed). VTE prophylaxis, post-op XR (AP pelvis, lateral hip to confirm component position, assess for fracture), PT for gait training and strengthening

References

1. Barrett WP, Turner SE, Leopold JP. Prospective randomized study of direct anterior vs postero-lateral approach for total hip arthroplasty. J Arthroplasty. 2013;28(9):1634-1638. RCT comparing DAA vs posterior approach, 100 patients, faster early recovery with DAA (6 weeks) but no difference at 1 year, LFCN injury 15% DAA vs 0% posterior

2. Rykov K, Reininga IHF, Sietsma MS, Knobben BAS, Ten Have BLEF. Posterolateral vs Direct Anterior Approach in Total Hip Arthroplasty (POLADA Trial): A Randomized Controlled Trial to Assess Differences in Serum Markers. J Arthroplasty. 2017;32(12):3652-3658. RCT DAA vs posterior, 120 patients, 2-year follow-up, no difference in pain/function/dislocation, LFCN injury 18% DAA

3. Mjaaland KE, Svenningsen S, Fenstad AM, et al. Implant Survival After Minimally Invasive Anterior or Anterolateral vs Conventional Posterior or Direct Lateral Approach in Total Hip Arthroplasty: A Multicenter Randomized Controlled Trial. J Bone Joint Surg Am. 2019;101(13):1206-1214. RCT comparing DAA vs lateral vs posterior, 300 patients, DAA faster early mobilization (days 1-3) but equal at 3 months, dislocation <1% all approaches

4. Miller LE, Gondusky JS, Bhattacharyya S, Kamath AF, Boettner F, Wright J. Does Surgical Approach Affect Outcomes in Total Hip Arthroplasty Through 90 Days of Follow-Up? A Systematic Review With Meta-Analysis. J Arthroplasty. 2018;33(4):1296-1302. Meta-analysis 15 RCTs, 1,556 patients, dislocation OR 0.37 favoring DAA (lower risk), LFCN injury OR 12.5 favoring posterior (DAA higher risk)

5. Wang Z, Hou JZ, Wu CH, et al. A systematic review and meta-analysis of direct anterior approach versus posterior approach in total hip arthroplasty. J Orthop Surg Res. 2018;13(1):229. Meta-analysis 21 studies, 3,400+ patients, early function advantage DAA at 6 weeks, no difference 3-12 months, femoral fracture slightly higher DAA (learning curve)

6. Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Hip, Knee & Shoulder Arthroplasty: 2023 Annual Report. Adelaide: AOA; 2023. Australian registry data showing DAA usage 15-20% of primary THAs nationally (increasing), 10-year revision rate 5.8% DAA vs 5.4% posterior (not significant), learning curve evident in first 50 cases (8.2% revision vs 5.1% posterior)

7. Hartford JM, Bellino MJ. The learning curve for the direct anterior total hip arthroplasty: a single surgeon's first 500 cases. Hip Int. 2017;27(5):483-488. Learning curve study showing operative time normalization after 50-100 cases (60-90min plateau), femoral complications decrease after 20-50 cases, acetabular positioning consistent after 30-75 cases

8. Jewett BA, Collis DK. High complication rate with anterior total hip arthroplasties on a fracture table. Clin Orthop Relat Res. 2011;469(2):503-507. Study showing higher complication rates (13%) in early DAA experience on fracture table including LFCN injury (30%), femoral fractures (4%), wound complications (5%), highlighting learning curve challenges

9. Meneghini RM, Pagnano MW, Trousdale RT, Hozack WJ. Muscle damage during MIS total hip arthroplasty: Smith-Petersen versus posterior approach. Clin Orthop Relat Res. 2006;453:293-298. Study comparing muscle damage between DAA (Smith-Petersen) and posterior approach using MRI and serum markers, showing less muscle damage with DAA (true internervous plane advantage)

10. Post ZD, Orozco F, Dixit V, Purtill JJ, Ong A, Hozack WJ. Direct Anterior Approach for Total Hip Arthroplasty: Indications, Technique, and Results. J Am Acad Orthop Surg. 2014;22(9):595-603. Comprehensive surgical technique review of DAA including indications, contraindications, step-by-step technique, danger zones (LFCN, femoral nerve), complications management, and learning curve recommendations