Ganz Trochanteric Flip Approach to the Hip

The Ganz trochanteric flip approach provides safe surgical dislocation of the hip, allowing 360-degree access to the femoral head and acetabular rim while preserving the blood supply from the deep branch of the medial femoral circumflex artery. The key technical innovation is the digastric greater trochanteric osteotomy that maintains continuity between the gluteus medius and vastus lateralis, protecting the MFCA which runs along the quadratus femoris. A Z-capsulotomy permits anterior dislocation without compromising posterior stability. This approach has revolutionised the treatment of femoroacetabular impingement, femoral head fractures, and selected acetabular pathologies by providing extensile exposure with low AVN rates when performed correctly.

The approach is performed through the Gibson interval between gluteus maximus and tensor fasciae latae. The greater trochanter is osteotomised in a digastric fashion preserving the vastus lateralis attachment. This allows the trochanter to be flipped anteriorly, exposing the hip capsule. The MFCA deep branch is protected as it courses posterior to the osteotomy site along the quadratus femoris. The Z-capsulotomy is the final step before dislocation, allowing the femoral head to be delivered anteriorly for complete inspection and treatment of pathology on both the head and acetabular rim.

Primary Indications

• Symptomatic femoroacetabular impingement (cam, pincer, or mixed) requiring osteochondroplasty and labral repair when arthroscopic access is insufficient
• Displaced femoral head fractures (Pipkin types I-IV) needing anatomic reduction and fixation
• Osteochondral lesions of the femoral head requiring grafting, microfracture, or fixation
• Acetabular rim fractures and associated labral pathology
• Synovial chondromatosis or pigmented villonodular synovitis requiring complete synovectomy
• Selected benign tumours of the femoral head and neck (chondroblastoma, osteochondroma)
• Residual deformity after Perthes disease or slipped capital femoral epiphysis requiring correction

Why This Approach is Chosen

Traditional posterior or anterior approaches to the hip do not provide circumferential access to the femoral head without risking avascular necrosis. The Ganz approach was developed specifically to allow safe dislocation by preserving the MFCA blood supply. It provides unparalleled visualisation of the entire femoral head and acetabular rim while maintaining the posterior capsule and labrum for stability.

Contraindications

• Active infection around the hip
• Severe osteoporosis precluding secure trochanteric fixation
• Previous surgery with extensive scarring that would compromise the MFCA
• Medical comorbidities precluding major surgery
• Isolated posterior wall acetabular fractures better treated through Kocher-Langenbeck

Alternative Approaches

• Hip arthroscopy for contained cam lesions and simple labral tears
• Smith-Petersen anterior approach for limited anterior pathology
• Kocher-Langenbeck for posterior wall and column acetabular fractures
• Combined approaches for complex pelvic deformities

Bony Anatomy

The greater trochanter is a broad bony prominence on the proximal femur serving as the insertion for the gluteus medius, gluteus minimus, and piriformis. The vastus ridge marks the inferior border where the vastus lateralis originates. The piriformis fossa lies medial to the trochanter and is the entry point for intramedullary nails. The femoral head is covered by hyaline cartilage except at the fovea capitis where the ligamentum teres attaches.

Muscular Layers and Attachments

The gluteus maximus inserts on the posterior femur and iliotibial band. The tensor fasciae latae lies anteriorly within the fascia lata. The gluteus medius inserts on the lateral and superolateral trochanter. The vastus lateralis originates from the vastus ridge and linea aspera. The short external rotators (piriformis, gemelli, obturator internus, quadratus femoris) insert on the posterior trochanter and intertrochanteric crest.

Neurovascular Anatomy - Critical for the Approach

The medial femoral circumflex artery arises from the profunda femoris or femoral artery. Its deep branch courses posteriorly along the quadratus femoris, ascends along the posterior capsule, and enters the femoral head at the superolateral head-neck junction. This vessel provides the majority of the blood supply to the femoral head. The ascending branch of the lateral femoral circumflex artery supplies the anterior head-neck junction but is less critical.

The sciatic nerve exits the greater sciatic notch and lies medial to the gluteus maximus. The superior gluteal nerve exits the greater sciatic notch and runs in the interval between gluteus medius and minimus. The nerve to vastus lateralis runs along the anterior border of the vastus lateralis.

Capsular Anatomy

The hip capsule is thick anteriorly and superiorly, thinner posteriorly. The iliofemoral ligament (Y ligament of Bigelow) is the strongest component. The pubofemoral and ischiofemoral ligaments provide additional stability. The labrum attaches to the acetabular rim and deepens the socket. The posterior capsule and labrum are preserved during the Ganz approach to maintain stability after dislocation.

Superficial Internervous Plane

The Gibson interval lies between the gluteus maximus (inferior gluteal nerve) posteriorly and the tensor fasciae latae (superior gluteal nerve) anteriorly. This plane is developed by incising the fascia lata and bluntly separating the muscle fibres. The interval is relatively bloodless and provides direct access to the greater trochanter. The inferior branch of the superior gluteal nerve to the TFL must be protected during anterior retraction.

Deep Internervous Plane

There is no classical deep internervous plane. The approach relies on the digastric osteotomy that maintains continuity between the gluteus medius (superior gluteal nerve) and vastus lateralis (femoral nerve). This continuity preserves the MFCA blood supply because the vessel runs posterior to the osteotomy site along the quadratus femoris and is not disrupted. The osteotomy fragment is flipped anteriorly as a single musculotendinous unit.

Structures at Risk in Each Layer

Superficial layer: inferior branch of superior gluteal nerve to TFL, lateral femoral cutaneous nerve with excessive anterior retraction.

Intermediate layer: sciatic nerve medial to gluteus maximus, superior gluteal neurovascular bundle at the proximal limit.

Deep layer: deep branch of MFCA along quadratus femoris (most critical), ascending branch of lateral femoral circumflex artery, medial circumflex vessels.

Intra-articular: labrum during capsulotomy, acetabular and femoral head cartilage during dislocation manoeuvres.

Position: Lateral Decubitus (Preferred)

The patient is placed on a radiolucent table with the operative hip up. A beanbag or lateral supports maintain position. The entire leg is prepped and draped free to allow unrestricted movement for dislocation. The contralateral leg is padded. Chest rolls and axillary padding prevent brachial plexus injury. The C-arm is positioned to obtain AP and cross-table lateral views without moving the patient.

Position: Supine (Alternative)

Used when combined anterior approaches are planned or surgeon preference. The patient lies supine on a radiolucent table or fracture table. Both legs are prepped. Traction can be applied if needed. This position allows easier conversion to anterior approaches but makes dislocation slightly more difficult.

Pre-positioning Checklist

• Confirm no contraindications to lateral positioning (shoulder pathology, spinal instability)
• Pad all pressure points including axilla, greater trochanter, fibular head, ankles
• Arms positioned with less than 90 degrees abduction
• Radiolucent table verified for C-arm access
• Tourniquet not typically used for this approach

Draping

Free draping of the entire leg from the iliac crest to the foot is essential. This allows full hip flexion, adduction, and external rotation for dislocation. A sterile stockinette or impervious drape covers the foot.

Key Bony Landmarks

• Anterior superior iliac spine (ASIS) - palpable anteriorly, reference for Gibson interval
• Greater trochanter - broad lateral prominence, insertion of abductors
• Vastus ridge - inferior border of trochanter, starting point for osteotomy
• Iliac crest - superior extent of incision
• Posterior superior iliac spine - reference for sciatic notch location

Key Soft Tissue Landmarks

• Gluteus maximus insertion on posterior femur
• Tensor fasciae latae within the fascia lata anteriorly
• Biceps femoris tendon palpable posteriorly
• Sciatic nerve can be palpated in some thin patients medial to gluteus maximus

Incision Planning

The skin incision follows the Gibson interval. It begins approximately 6-8cm proximal to the greater trochanter along a line directed toward the ASIS, curves posteriorly over the trochanter, then extends distally along the lateral femur for 8-10cm. Total length 15-20cm. The proximal limb allows access to the iliac crest if needed. The distal limb allows extension for femoral shaft access.

Proximal Extension

Extend the incision along the iliac crest to access the ilium and acetabular roof. Useful for combined periacetabular osteotomy or extensive rim reconstruction. The superior gluteal neurovascular bundle limits safe extension to approximately 5cm proximal to the ASIS.

Distal Extension

Extend along the lateral femur by splitting the vastus lateralis in its midline. Allows access to the femoral shaft for osteotomy, hardware removal, or fracture fixation. The nerve to vastus lateralis runs in the anterior third of the muscle and should be protected.

Combined Approaches

The Ganz approach can be combined with the Smith-Petersen anterior approach for global acetabular access or with a posterior column approach for complex acetabular fractures. Staged positioning may be required.

Revision Considerations

In revision cases with previous surgery, the MFCA may be scarred or already compromised. Consider preoperative angiography or proceed with extreme caution. Trochanteric nonunion from prior surgery requires careful planning for re-fixation.

Intra-operative Complications

• MFCA injury leading to AVN (5-15 percent)
• Trochanteric fracture during osteotomy (rare with proper technique)
• Sciatic nerve stretch injury (less than 1 percent)
• Intra-articular hardware placement
• Cartilage or labral iatrogenic damage

Post-operative Complications

• Trochanteric nonunion (5-15 percent) - risk factors include poor reduction, inadequate fixation, smoking, osteoporosis
• Heterotopic ossification (10-30 percent) - prophylaxis with indomethacin or radiation in high-risk patients
• AVN of femoral head (5-15 percent) - presents 6-24 months post-operatively
• Infection (1-3 percent)
• Deep vein thrombosis (2-5 percent)
• Abductor weakness and Trendelenburg gait (usually resolves with trochanteric union)

Prevention Strategies

Secure trochanteric fixation with multiple screws and cables, anatomic reduction with compression, protected weight bearing until union, heterotopic ossification prophylaxis in high-risk patients, meticulous MFCA protection throughout.

Immediate Post-operative (0-48 hours)

• Neurovascular checks every 2 hours documenting sciatic and femoral nerve function
• Wound inspection at 24-48 hours
• Elevation and ice for swelling control
• DVT prophylaxis with LMWH or aspirin per protocol
• Multimodal analgesia including regional blocks where appropriate

Weight Bearing Protocol

• Touch weight bearing or partial weight bearing (20-30kg) for 6-8 weeks
• Progression based on radiographic evidence of trochanteric healing
• Full weight bearing typically at 8-12 weeks
• Crutches or walker required until stable gait achieved

Range of Motion

• Passive and active-assisted ROM as pain allows from day 1
• Goal: 0-90 degrees flexion by 6 weeks
• Abduction exercises begin at 6 weeks after trochanteric healing confirmed
• No active abduction against resistance until 8-12 weeks

Follow-up Schedule

• 2 weeks: wound check, suture removal
• 6 weeks: radiographs, assess trochanteric position, progress weight bearing
• 12 weeks: radiographs, confirm union, full weight bearing
• 6 months: clinical and radiographic review, assess for AVN
• 1 year: final functional assessment, MRI if AVN suspected