This study was a prospective case series of adolescents with moderate or severe chronic SCFE who had undergone subcapital realignment using the surgical hip dislocation approach from January 2014 to April 2015. All surgeries were performed by a single pediatric orthopedic surgeon. The Institutional Review Boards (IRB) and Ethics Committee of Menoufia University approved the study. Written consent for the procedure and possible complications was taken from the parents.

Inclusion criteria were patients between 8 and 17 years old who had moderate or severe degrees of chronic stable SCFE with open physis. A minimum of 6 years of follow-up were required for study inclusion.

Exclusion criteria were SCFE with other congenital or acquired hip deformities, SCFE in patients with known endocrinopathies, and a history of prior surgical interference. Those patients were excluded to avoid the effects of those variables on the results of the procedure.

General and local examinations were performed to evaluate the body mass index (BMI), stability of slippage, hip joint range of motion, and preoperative limb length discrepancy (LLD). Plain X-rays of the slipped side were obtained. CT scan was used for the assessment of physeal closure and the attempted healing process in the proximal metaphysis that occurred with chronic displacement of the epiphysis; see Fig. 1. The epiphyseal-shaft and alpha angles were measured on the preoperative X-rays; see Fig. 2.

Preoperative images of a 13-year-old male patient with left chronic SCFE. A Plain X-rays (AP and lateral views). B CT axial cut

A Measurement of the epiphyseal-shaft angle bilaterally. B Measurement of the alpha angle

Preoperative laboratory investigations were done in the form of a complete blood count, a bleeding profile, liver and kidney function tests, and a hormonal assay in patients suspected of associated endocrinopathies (thyroid hormones, growth hormone, and testosterone levels).

Patients were given a third-generation cephalosporin injection 2 h before surgery, with the dose adjusted depending on the weight.

The procedure was done in the lateral position with the affected lower limb up. A straight skin incision was made over the greater trochanter and the fascia lata was incised.

Greater trochanteric osteotomy with a maximum thickness of 1.5 cm was performed using an oscillating saw along a line extending between the posterosuperior edge of the greater trochanter and the posterior border of the vastus lateralis ridge. The trochanteric segment was mobilized anterosuperior by inserting a Hohmann elevator into the osteotomy gap after releasing the remaining tendinous parts of the gluteus medius from the stable trochanter and after subperiosteal dissection of the anterolateral part of the vastus lateralis from the femur; see Fig. 3.

A Straight lateral skin incision and superficial dissection. B Greater trochanteric osteotomy

Z-shaped capsulotomy was performed, where the vertical component started close to the anterosuperior corner of the stable trochanter and then directed proximally along the femoral neck axis. This was followed by an anterior capsular cut parallel to the intertrochanteric line and posterior capsulotomy along the acetabular rim.

The femoral head was temporarily stabilized by the insertion of two 2-mm Kirschner wires from the anterior aspect of the neck toward the center of the head to provide stability before dislocation.

Then the femoral head was dislocated by flexion, adduction, and external rotation of the hip after transection of the ligamentum teres using a scissor. After incising the periosteum along its axis, the retinacular flap was cautiously mobilized proximally with a periosteal elevator. The flap was extended distally to the lesser trochanter; see Fig. 4.

A Z-shaped capsulotomy. B Development of the periosteal-retinacular flap

After removal of the transfixing K-wires, the femoral head was stepwise mobilized using an osteotome beginning from anterior. The femoral epiphysis with the attached periosteal-retinacular flap was gradually separated from the metaphysis, assisted by external rotation.

After complete separation of the epiphysis with its attached periosteal-retinacular flap, the metaphyseal callus was resected. A curette was used to clean the epiphysis from the growth plate tissue.

Manual reduction of the epiphysis on the metaphyseal was made without any tension on the retinacular flap. In the case of a difficult reduction, further neck shortening was done to prevent tension on the retinacular vessels. The epiphysis was provisionally fixed by two or three threaded guide wires of the cannulated screws; see Fig. 5. The threaded guide wires were advanced till they were flush with the articular surface and were checked by fluoroscopy.

Reduction and provisional fixation of the head

Definitive fixation of the epiphysis was done using two 6.5-mm partially threaded cannulated screws. The length of the screws was 5 mm shorter than the actual measure of the threaded guide wires. The correct alignment of the epiphysis was checked by fluoroscopy by restoring the epiphyseal-metaphyseal anterior offset and correcting the epiphyseal-shaft angle after epiphyseal reduction to about 145° on the AP view and 10° on the frog-leg lateral view [8, 25].

Perfusion of the epiphysis was monitored periodically by making a 2-mm drill hole in the epiphysis and observing the resulting bleeding. The anterior periosteum and the posterior retinacular flap were reattached using tension-free sutures, and the capsule was closed without tension. Fixation of the osteotomized greater trochanter with two 4.5-mm cortical fully threaded screws was done in a more distal position (0.5–1 cm) to place the abductors under proper tension. A suction drain was inserted, followed by closure of the fascia lata, subcutaneous tissue, and the skin.

Postoperative plain X-rays were done; see Fig. 6. Passive hip range-of-motion exercises were commenced during the hospital stay. The suction drain was removed after 24 h.

Immediately postoperative X-rays. A AP view. B Lateral view

Follow-up in the outpatient clinic was done with an assessment of wound status and suture removal after 2 weeks. Moreover, evaluation of the radiological union was performed to start weight bearing and physiotherapy after 3 months. Another evaluation was performed after 1 year for clinical and radiological assessment and for the detection of complications. The final clinical and radiological evaluation was done after 6 years of follow-up; see Fig. 7.

Six-year follow-up X-rays. A AP view. B Lateral view

Clinical outcomes were assessed with the Harris Hip Score (HHS) [26]. A satisfactory outcome was considered to be a HHS of ≥ 80 points. Measurement of the epiphyseal-shaft angle and alpha angle was done postoperatively.

At the end of the study, the data were collected, tabulated, and statistically analyzed by IBM SPSS (Statistical Package for the Social Sciences) version 23. The chi-square test and Wilcoxon test were utilized for comparative statistical analysis when appropriate. The significance level was set at P values of less than 0.05.