Surgical Hip Dislocation for Small Posterior Wall Fracture After Hip Subluxation

Abstract

Summary: 

This case demonstrates a recognized association between an acetabular injury pattern and underlying morphology of the hip. In the patient discussed, hyperflexion of the hip results in the engagement of the present CAM lesion, and the resulting subluxation leads to a fracture of the posterior wall and instability of the hip. This combination of pathologies was addressed with a surgical dislocation approach to address both the CAM lesion and fix the posterior wall.

Surgical dislocation of the hip is indicated for the management of small posterior wall fractures after hip subluxation and has been proven to be a safe procedure through various anatomic studies.^1–3 Described by Ganz et al,⁴ surgical dislocation of the hip involves an anterior dislocation from a posterior approach with a trochanteric flip osteotomy. During dislocation, the deep branch of the medial femoral circumflex artery is protected by the intact obturator externus muscle. This approach has been demonstrated to be safe and efficacious based on several outcome-based studies by Matta et al, Hafeli et al, and Tannast et al.⁷

The patient is positioned lateral decubitus, and a Kocher–Langenbeck incision is made through the skin and subcutaneous tissue. The fascia lata is incised between the anterior and posterior borders of the greater trochanter and carried distally along the femoral shaft past the insertion of the gluteus maximus on the femur. Proximally, this split is in the interval between the tensor fascia lata muscle and the gluteus maximus and should avoid violating gluteus maximus fibers.

The vastus lateralis is elevated to visualize the trochanteric osteotomy landmarks, and electrocautery is used to mark the level with the hip extended and internally rotated. The osteotomy splits the tip of the trochanter through the tendon of the gluteus medius and exists distal to the vastus ridge. A 5-mm vertical osteotomy step cut is added in the middle of the osteotomy because there is no plan to advance the trochanter. An oscillating saw is used to create the osteotomy with a maximal thickness of ∼1.5 cm. The step cut is added with a 10-mm osteotome connecting the proximal and distal parts of the osteotomy, creating 2 ridges. This anterior ridge and the step cut creates a more stable bed for the osteotomy, allowing it to sit firmly with no need to predrill for final fixation. Any portion of the gluteus medius tendon still attached should be released to open the interval between the piriformis tendon and the minimus. The trochanteric osteotomy is mobilized anteriorly by releasing the vastus lateralis from the lateral femur to about the level of the midportion of the gluteus maximus tendon insertion. Occasionally, a small portion of the piriformis tendon must be released from the trochanteric fragment.

The leg is flexed and externally rotated. The capsule is then exposed by elevating the gluteus minimus fibers. The sciatic nerve is examined to define the patient's individual anatomy. If the sciatic nerve is exposed, care should be taken to maintain the integrity of the anastomotic branch from the inferior gluteal artery that runs on the inferior aspect of the piriformis and can contribute to femoral head vascularity. The piriformis can be released (10–15 mm away from the insertion) to avoid stretching of the branches of the sciatic nerve during dislocation.

The capsule is incised in a Z-shaped configuration, with the first limb of the incision along the anterolateral axis of the femoral neck. The second limb of the incision is made starting at the anterior border of the piriformis tendon and coursing anteroinferior. This incision must remain anterior to the lesser trochanter and not too inferior to avoid the main branch of the medial femoral circumflex artery. These 2 incisions create an anteroinferior flap that is elevated to visualize the labrum before the creation of the final capsular incision. A curved knife is then used in an inside-out manner to create the final limb by incising posteriorly from the first incision, parallel to the labrum and the acetabular rim.

The leg is flexed, abducted, and externally rotated to enable anterior dislocation of the hip. Combinations of 3 retractors are then placed to enable exposure. The first retractor (a pointed Hohman) is impacted into the supraacetabular pelvis. A second intracapsular retractor (pointed cobra-like) is hooked around the anterior acetabular rim. A third retractor (thin cobra-like) is positioned under the transverse acetabular ligament. Positioning of the leg in 90 degrees of flexion, slight adduction by lowering the knee, and axial pressure by an assistant allows the surgeon 360 degrees access to the acetabulum, acetabular rim/labrum, anterior inferior iliac spine, femoral head, and proximal femur. From this exposure, a variety of interventions can be used.

Our patient has an increased alpha angle and CAM lesion, predisposing the patient to subluxation of the femoral head. The labrum is noted intraoperatively to be attached to the posterior wall, not requiring repair. The alpha angle is corrected with a femoral osteochondroplasty, and the posterior wall is plated with a 2.4-mm mini-fragment plate placed directly on the rim because of the small size of the wall. The capsule is closed and cortical screws are used to lag the trochanteric osteotomy into place.

Patients are 30 lb partial weight-bearing with crutches for 2–4 weeks. Continuous passive motion is used 4–6 hours a day for 4 weeks. Passive motion and active-assisted exercises are performed the first 4 weeks with a stationary bicycle as tolerated. At 4 weeks, patients are full weight-bearing with progressive active strengthening. At 8 weeks, resistance strengthening, swimming, and elliptical machine are introduced, regardless of the size of the wall fragment. Patients are released to full activity 4 months after surgery.