Hip Anterior Approach (Smith-Petersen)

Approach Variants Classification:

The approach variant chosen depends primarily on the indication and required exposure.

LFCN Anatomical Variations (Sartorius Classification):

The lateral femoral cutaneous nerve has significant anatomical variability, impacting surgical planning.

Pre-operative counseling about LFCN injury risk is essential given the variable anatomy.

Acetabular Fracture Classification (Judet-Letournel):

For acetabular work via this approach, understand the fracture patterns.

Elementary types (5):

• Anterior wall
• Anterior column
• Posterior wall
• Posterior column
• Transverse

Associated types (5):

• Both-column
• T-shaped
• Transverse + posterior wall
• Anterior column/posterior hemitransverse
• Anterior wall/posterior hemitransverse

Smith-Petersen approach (with iliofemoral extension) is indicated for:

• Anterior column fractures
• Anterior wall fractures
• Both-column fractures
• Anterior column + posterior hemitransverse

Ideal candidates for anterior approach THA:

• BMI under 35 (obesity increases difficulty)
• Normal femoral anatomy (not severe retroversion/valgus)
• No previous anterior hip surgery
• Preserved hip flexion (over 90 degrees)
• Primary arthroplasty (revisions more challenging)

Physical examination findings:

• Hip range of motion assessment
• Flexion contracture evaluation
• Leg length discrepancy measurement
• Neurovascular status (especially LFCN distribution)
• Skin quality over anterior approach

Contraindications/caution:

• Morbid obesity (BMI over 40)
• Severe femoral retroversion or valgus deformity
• Proximal femoral hardware or deformity
• Previous anterior approach surgery
• Ankylosed hip

Careful patient selection optimizes outcomes for anterior approach THA.

History and mechanism:

• High-energy trauma (dashboard injury, fall from height)
• Associated injuries (Letournel: 40% have other significant injuries)
• Time from injury (ideally surgery within 5-14 days)
• Medical optimization status

Physical examination:

• Hemodynamic stability (retroperitoneal hemorrhage common)
• Sciatic nerve function (10% of posterior fracture-dislocations)
• Skin integrity (Morel-Lavallee lesion assessment)
• Associated lower extremity injuries

Red flags requiring urgent intervention:

• Open fracture
• Irreducible dislocation
• Sciatic nerve deficit with displaced fragment
• Vascular compromise

Red flags require urgent surgical intervention within 24-48 hours.

Clinical assessment:

• Walking pattern (if ambulatory)
• Leg length discrepancy
• Range of motion assessment
• Galeazzi sign (leg appears short in flexion)
• Trendelenburg test

Age-specific considerations:

• 6-18 months: Open reduction candidacy
• 18 months - 6 years: PAO or Pemberton consideration
• Over 6 years: Salvage procedures (shelf, Chiari)

Imaging correlation required:

• Ultrasound (under 6 months)
• AP pelvis radiograph
• CT arthrography for surgical planning

Imaging modality selection is age-dependent for pediatric DDH assessment.

Decision Algorithm - Approach Selection:

The decision pathway should systematically address all factors before committing to approach selection.

Approach Selection by Indication:

Choose the approach based on surgeon experience and patient-specific factors.

Recognizing when NOT to use the anterior approach is as important as knowing when to use it.

Direct Anterior Approach (DAA) for THA:

Ideal candidates:

• Young, active patients seeking faster recovery
• Normal to increased femoral anteversion
• Non-obese patients (BMI under 35 preferred)
• Primary THA with normal anatomy

Relative contraindications:

• Severe obesity (BMI over 40) - difficult femoral exposure
• Severe retroversion or valgus femur - challenging femoral preparation
• Previous anterior hip surgery - scarring complicates dissection
• Severe flexion contracture - limits femoral access

Advantages:

• True muscle-sparing approach
• Lower dislocation risk (theoretically)
• Faster early recovery and mobilization
• Supine positioning allows bilateral procedures

Disadvantages:

• Steep learning curve (30-50 cases)
• Limited femoral exposure (difficult revisions)
• LFCN injury risk
• Specialized table/equipment often used

This approach has gained significant popularity as the DAA for THA due to perceived faster recovery, though long-term outcomes are similar to other approaches.

Gold standard for anterior acetabular access:

Ideal fracture patterns:

• Anterior column fractures
• Anterior wall fractures
• Both-column fractures (can access both columns)
• T-type fractures (with posterior approach)

Surgical approach: Standard Smith-Petersen with iliofemoral extension:

• Allows 360-degree acetabular visualization
• Access to inner and outer tables
• Quadrilateral plate visualization
• Superior dome visualization

Key steps for fracture work:

1. Expose anterior column along pelvic brim
2. Detach external oblique from iliac crest for proximal extension
3. Reflect iliacus from inner table
4. Visualize fracture lines and reduction
5. Apply reconstruction plate along pelvic brim

The extensile nature of this approach makes it essential for acetabular fracture surgeons.

Developmental dysplasia of hip (DDH):

Procedures via anterior approach:

• Open reduction of DDH (age 6-18 months)
• Pemberton osteotomy (acetabuloplasty)
• Periacetabular osteotomy (PAO) - adolescents and adults
• Shelf procedures for acetabular dysplasia

Advantages in children:

• Excellent acetabular exposure
• Safe plane (no motor nerve risk)
• Can address both femoral and acetabular pathology
• Lower infection risk than medial approach

Technical considerations:

• LFCN in children is more medial - protect carefully
• Smaller working space requires fine instruments
• Cartilage injury risk at margins of capsulotomy

This is the standard approach for most pediatric hip reconstruction procedures.

Additional uses:

Tumor resection:

• Access to anterior iliac tumors
• Combined with lateral window for total hip reconstruction after tumor

Hip arthrodesis:

• Historical indication (Smith-Petersen's original use)
• Wide exposure for joint preparation and fixation
• Rarely performed in modern practice

Iliopsoas tenotomy:

• Symptomatic iliopsoas impingement after THA
• Lesser trochanter access

Hip arthroscopy portal placement:

• Anterior portal uses same internervous plane
• Familiarity with anatomy reduces neurovascular injury risk

The versatility of this approach explains its continued relevance across subspecialties.

Surface Landmarks and Incision

Palpable landmarks:

• ASIS (anterior superior iliac spine) - primary landmark
• Greater trochanter - lateral and distal
• Femoral pulse - medial (marks neurovascular bundle)

Incision options:

Standard Smith-Petersen (for acetabular work):

• Start 2cm distal and lateral to ASIS
• Curve distally and laterally toward greater trochanter
• Length: 10-15cm (can extend as needed)
• Stays lateral to neurovascular bundle

Direct Anterior Approach (DAA) for THA:

• Longitudinal incision between ASIS and greater trochanter
• Length: 8-10cm for minimally invasive technique
• Centered over palpable interval between TFL and sartorius

Superficial Layer Dissection

Step 1: Incise skin and subcutaneous tissue

• Deepen through subcutaneous fat using cutting diathermy
• Ligate or cauterize superficial vessels
• Look for LFCN in subcutaneous layer

Step 2: Identify and manage LFCN

• Runs from lateral to medial, usually 1-2cm distal to ASIS
• Variable anatomy: may pass under, through, or lateral to inguinal ligament
• Options: (1) identify and retract medially (preserve), or (2) divide and bury if tented
• Counsel patient preoperatively about meralgia paresthetica risk (10-20%)

Step 3: Identify fascia and muscular interval

• Identify fascia lata and fascia over TFL
• Palpate interval between TFL (lateral - taught, band-like) and sartorius (medial - softer)
• Mark interval with electrocautery

Deep Interval Development

Step 1: Open fascia in line with interval

• Incise fascia between TFL (lateral) and sartorius (medial)
• Interval typically easy to identify by palpation
• Extend incision proximally to just below inguinal ligament

Step 2: Develop internervous plane

• Blunt dissection between TFL and sartorius
• This is a true internervous plane: TFL (superior gluteal), sartorius (femoral)
• Place retractors: self-retaining with care, or hand-held initially

Step 3: Identify and manage rectus femoris

• Rectus lies deep in the interval
• Two heads: straight head (AIIS) and reflected head (superior acetabular rim)
• For THA: retract rectus medially with iliopsoas
• For acetabular work: may need to release reflected head for better visualization

Step 4: Ligate ascending branch of LCFA

• Lateral circumflex femoral artery ascending branch runs between rectus and TFL
• Must be identified and ligated for hemostasis
• Use ties or clips - avoid diathermy near nerve
• This is a consistent bleeder if not addressed early

A clear understanding of the deep anatomy is essential for safe execution of this approach.

Hip Capsule Exposure and Capsulotomy

Step 1: Reflect muscles from capsule

• Retract TFL laterally
• Retract sartorius and rectus femoris medially
• Identify anterior hip capsule

Step 2: Hip capsulotomy pattern

For THA:

• Capsular release: T-shaped or inverted L
• Longitudinal limb along femoral neck
• Transverse limb along acetabular rim
• Excise or preserve capsule per surgeon preference

For acetabular fracture:

• Limited capsulotomy or capsulectomy
• Goal is exposure of anterior column and acetabular rim
• May need to release reflected head of rectus

For pediatric DDH:

• Anterior capsular flap based superiorly
• Preserve capsule for closure
• Open transversely to visualize femoral head

Step 3: Identify key landmarks

• Femoral neck anteriorly
• Acetabular rim superiorly
• Transverse acetabular ligament and labrum
• Ligamentum teres (if preserved)

The capsulotomy pattern depends on the indication and surgeon preference for capsular repair.

Femoral Exposure (for THA/Hip Arthroplasty)

Challenge: Limited femoral access compared to posterior/lateral approaches

Step 1: Position hip for femoral exposure

• Extend hip by dropping leg off side of table or using femoral positioner
• Externally rotate hip to bring proximal femur into field
• Flexion of hip relaxes anterior structures for neck osteotomy

Step 2: Perform femoral neck osteotomy

• In situ osteotomy with oscillating saw
• Cut at predetermined level (preoperative templating)
• Remove femoral head with corkscrew or bone hook

Step 3: Access femoral canal

• Place bent Hohmann retractor around proximal femur
• Elevate proximal femur anteriorly
• Externally rotate and extend hip to bring femur into operative field
• Use specialized femoral elevator/positioner if available

Step 4: Prepare femoral canal

• Broach or ream per implant system
• Limited visualization - rely on tactile feedback and fluoroscopy
• Higher learning curve than posterior approach for femoral preparation

Pitfalls:

• Proximal femoral fracture during broaching due to limited visualization
• Varus stem position if not carefully aligned
• Wound extension required in difficult cases (muscular patients, abnormal anatomy)

Mastery of femoral exposure techniques is critical for successful anterior approach THA.

Iliofemoral Extension (for Acetabular Fracture Work)

Indication: Full acetabular visualization for fracture fixation

Step 1: Proximal extension of skin incision

• Extend incision proximally along iliac crest
• Can curve posteriorly to greater sciatic notch if needed
• Subperiosteal dissection along iliac crest

Step 2: Detach external oblique from iliac crest

• Release abdominal muscles (external oblique, internal oblique, transversus) from iliac crest
• Elevate anteriorly to expose inner table of ilium
• Preserve lateral cutaneous nerve of thigh (iliohypogastric)

Step 3: Reflect iliacus from inner table

• Subperiosteal dissection of iliacus from inner pelvic wall
• Work from lateral to medial
• Exposes pelvic brim and quadrilateral plate

Step 4: Visualize acetabulum

• Full 360-degree visualization possible
• Anterior column along pelvic brim
• Anterior wall and dome
• Posterior column (limited - may need separate incision)
• Quadrilateral plate medially

Step 5: Fracture reduction and fixation

• Reduce fracture with pointed reduction forceps
• Temporary K-wire fixation
• Apply reconstruction plate along pelvic brim (typical for anterior column)
• Multiple screw fixation into columns

The extensile capability of this approach makes it invaluable for complex acetabular reconstruction.

Day 0-1 (Immediate postoperative):

• Early mobilization: same day or day 1
• No hip precautions required (advantage of anterior approach)
• Weight bearing as tolerated with walker or crutches
• DVT prophylaxis: Aspirin 100mg BD or rivaroxaban 10mg daily
• Multimodal analgesia: paracetamol, NSAIDs (if appropriate), opioids PRN
• Ice and elevation

Day 1-14 (Early recovery):

• Progress to cane or single crutch
• Physiotherapy: gait training, hip strengthening
• Wound check at day 14
• Remove staples/sutures at 14 days

Week 2-6 (Rehabilitation):

• Wean walking aids (typically by week 4-6)
• Progressive strengthening exercises
• Activity modification as tolerated
• Drive when off narcotics and safe (typically 4-6 weeks)

6 weeks and beyond:

• Review with X-ray
• Return to full activities as tolerated
• Sports typically allowed 3-6 months postoperatively

The absence of hip precautions facilitates faster functional recovery compared to posterior approach.

Immediate (Day 0-2):

• Bed rest 24-48 hours
• DVT prophylaxis essential (enoxaparin 40mg daily)
• Heterotopic ossification prophylaxis: indomethacin 75mg daily for 3 weeks OR radiation (700cGy single dose)
• Pain management: multimodal analgesia
• Hemodynamic monitoring (retroperitoneal bleeding)

Week 1-6:

• Touch weight bearing (maximum 10kg) for 6 weeks minimum
• Early ROM exercises (passive then active)
• DVT prophylaxis continues 4-6 weeks
• Serial X-rays at 2, 6, 12 weeks

Week 6-12:

• Progress weight bearing based on X-ray healing
• Partial weight bearing if bridging callus visible
• Full weight bearing typically by 12 weeks
• Physiotherapy for strengthening

Long-term:

• Risk of post-traumatic arthritis (10-50% depending on injury)
• THA may be required (typically 5-20% at 10 years)
• Monitor for heterotopic ossification symptoms

Anatomic reduction and HO prophylaxis are the two most important factors for long-term outcome.

DDH Open Reduction (Infant/Toddler):

• Hip spica cast immediately postoperatively
• Cast duration: 3 months (typically 6 weeks in "human position" then 6 weeks in abduction)
• Parents education on cast care and positioning
• Close follow-up with serial imaging

Periacetabular Osteotomy (Adolescent/Adult):

• Touch weight bearing for 6 weeks
• CPM or early ROM exercises
• DVT prophylaxis for 4-6 weeks
• Progress to full weight bearing by 8-12 weeks
• Return to sports 4-6 months

Key monitoring:

• Acetabular remodeling assessment
• Femoral head coverage improvement
• Pain and function improvement

Serial imaging confirms adequate coverage and guides return to activity decisions.