Surgical Hip Dislocation (Ganz Trochanteric Flip)

the blood supply to the femoral head is predominantly from the deep branch of the medial femoral circumflex artery (MFCA), which courses along the posterosuperior femoral neck within a synovial retinacular fold. By performing a specific anterior trochanteric flip osteotomy that preserves the posterior soft-tissue envelope (including the short external rotators and the MFCA retinacular branches), the hip can be safely dislocated anteriorly without devascularising the femoral head.

• Femoroacetabular impingement (FAI) - cam, pincer, or mixed type requiring osteochondroplasty, acetabuloplasty, labral repair or refixation
• Intra-articular loose bodies - synovial chondromatosis, fracture fragments, osteochondral loose bodies
• Femoral head fractures - Pipkin type I and II, allowing ORIF with direct joint visualisation
• Acetabular fractures - posterior wall, transverse, and T-type fractures where joint surface visualisation is essential
• Early avascular necrosis - staging, core decompression, or bone grafting under direct vision
• Slipped capital femoral epiphysis (SCFE) - modified Dunn procedure for realignment with vascular protection
• Pigmented villonodular synovitis (PVNS) and other synovial pathology requiring complete synovectomy
• Complex labral pathology - labral reconstruction, refixation in the setting of dysplasia or FAI
• Chondral lesions - assessment and treatment of osteochondral defects of the femoral head

• Legg-Calve-Perthes disease deformity correction in the healed stage
• Post-traumatic deformity of the femoral head or acetabular rim
• Ischiofemoral impingement requiring lesser trochanteric osteoplasty
• Revision after failed hip arthroscopy with residual impingement

The blood supply to the adult femoral head is predominantly from the medial femoral circumflex artery (MFCA), with a minor contribution from the lateral epiphyseal vessels (from the MFCA retinacular branches) and the artery of the ligamentum teres (variable and usually insufficient to sustain the head alone).

• The deep branch of the MFCA originates from the profunda femoris artery, passes posteriorly between the pectineus and iliopsoas tendons, then courses between the obturator externus and adductor brevis muscles. It pierces the hip capsule at the posterosuperior aspect of the femoral neck.
• At the capsule, the MFCA gives off retinacular branches that run along the posterosuperior femoral neck within a synovial fold (the retinaculum of Weitbrecht). These are the superior retinacular arteries (also called lateral epiphyseal arteries) - the dominant supply to the weight-bearing segment of the femoral head.
• The MFCA forms an extracapsular anastomotic ring at the base of the femoral neck with branches of the lateral femoral circumflex artery and the inferior gluteal artery.

the trochanteric flip osteotomy is designed so that the entire retinacular vascular chain remains attached to the trochanteric fragment and the posterior soft tissues. The osteotomy is performed anterior to the insertion of the external rotators, and the short external rotators (obturator internus, gemelli, piriformis) are NOT divided - they are mobilised posteriorly with the trochanteric fragment, carrying the MFCA within their protective soft-tissue envelope.

• The gluteus medius inserts on the posterosuperior and lateral greater trochanter
• The gluteus minimus inserts on the anterior facet of the greater trochanter
• The vastus lateralis originates from the inferior aspect of the greater trochanter
• The trochanteric fossa (digital fossa) is the posterior depression where the obturator externus tendon inserts - the osteotomy must NOT extend into this fossa
• The piriformis fossa is the entry point for the MFCA deep branch - this must be protected

• The hip capsule attaches to the acetabular labrum and transverse ligament centrally and to the intertrochanteric line anteriorly and the femoral neck posteriorly (mid-neck level)
• The Z-shaped capsulotomy used in the Ganz technique runs from the anterosuperior acetabular rim along the femoral neck, then turns posterosuperiorly along the head-neck junction, avoiding the inferior capsule where additional retinacular vessels may be present

• A lateral or posterolateral skin incision is made centred over the greater trochanter, extending approximately 15-20 cm. The incision can be straight (standard) or slightly curved posteriorly (modified Gibson approach).
• The iliotibial band (ITB) is incised in line with the skin incision, and the gluteus maximus fibres are split bluntly along their posterior border if a Gibson-type approach is used.

• The anterior border of the gluteus medius is identified. The trochanteric osteotomy is performed with an oscillating saw in the sagittal plane, approximately 1-1.5 cm thick at the base, from the posterosuperior aspect of the greater trochanter to a point just distal to the anterior trochanteric ridge.
• The osteotomy is directed from posterior to anterior, leaving the gluteus medius attachment on the trochanteric fragment superiorly and the vastus lateralis origin attached inferiorly. This creates a mobile osteotomised fragment that can be flipped anteriorly with its muscle attachments.
• The short external rotators (piriformis, obturator internus, gemelli) remain attached to the intact posterior femur - they are NOT detached. The MFCA runs deep to these muscles and is protected by keeping them intact.
• The trochanteric fragment, with the gluteus medius and vastus lateralis attached, is mobilised anteriorly by releasing the gluteus minimus from the anterior capsule (the gluteus minimus tendon inserts on the anterior facet and must be carefully elevated).
• The capsule is now exposed anteriorly, superiorly, and posterosuperiorly.

• AAOS (US): the AAOS clinical practice guideline for non-arthroplasty management of OA of the hip recognises FAI treatment as a developing area. Surgical dislocation is supported as an option for comprehensive FAI correction when arthroscopic treatment is insufficient or when the pathology requires open visualisation. AAOS has endorsed labral refixation over resection when technically feasible.
• BOA/BHS (UK): the British Hip Society supports surgical dislocation as a joint-preserving option for complex FAI, femoral head fractures (Pipkin), and intra-articular pathology requiring direct visualisation. The technique is typically performed in specialist hip preservation units.
• EFORT/European consensus: European centres (particularly Bern, Munich, Lausanne, and other high-volume hip preservation centres) have extensive experience with the Ganz technique. European practice has historically favoured open surgical dislocation more than North American practice, where hip arthroscopy gained earlier widespread adoption.

• No national arthroplasty registry specifically tracks surgical dislocation procedures, as they are joint-preserving operations. However, conversion rates to total hip arthroplasty after surgical dislocation are tracked in institutional series and provide surrogate survivorship data.
• Large institutional series from Bern, Melbourne, and Boston report conversion to THA in approximately 10-15% at 10 years, predominantly in patients with pre-existing chondral damage or advanced FAI at the time of the index procedure.
• The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) captures data on patients who subsequently undergo THA after hip preservation procedures, providing real-world conversion rate data.

• European surgeons (particularly in Switzerland, Germany, and France) have the longest experience with surgical dislocation and continue to favour it for complex FAI pathology. The Bernese group's influence remains strong.
• North American practice has shifted toward hip arthroscopy as the first-line treatment for FAI, with surgical dislocation reserved for complex or revision cases, pincer-type FAI requiring extensive rim work, and femoral head fractures. The threshold for open dislocation varies significantly between centres.
• Asian practice, particularly in Japan and South Korea, follows a similar pattern with arthroscopy as first-line and surgical dislocation for complex cases.
• In low- and middle-income settings, surgical dislocation may be more commonly used than arthroscopy due to the lower capital equipment costs (no arthroscopy tower required), though the technical expertise required limits its availability.

• The modified Dunn procedure (surgical dislocation for SCFE deformity correction in the acute or chronic setting) is increasingly adopted in paediatric orthopaedic centres worldwide, with specific protocols for vascular monitoring.
• Combined approaches (surgical dislocation with periacetabular osteotomy for FAI with dysplasia) are performed in specialist centres for complex hip deformity.
• Advances in hip arthroscopy continue to expand the scope of what can be treated arthroscopically, narrowing the indications for open dislocation, but the Ganz approach remains essential for pathology that cannot be addressed arthroscopically.