Between 1996 and 2009, we treated 89 patients at two centers (University Hospital-Bern and Children’s Hospital-Boston) with the modified Dunn procedure through a surgical hip dislocation approach [20
]. Sufficient clinical data based on the patients’ records were available for 82 hips to retrospectively classify the SCFE according to the acute/chronic [3
] and stable/unstable [35
] classifications and to classify intraoperative physeal stability as intact or disrupted with visible and demonstrable mobility between metaphysis and epiphysis. Thirty-nine patients were female and 43 were male, with a mean age at surgery of 12 ± 1.7 years (range, 7–18 years), and the average duration of symptoms before surgery was 12 ± 20.7 weeks (range, 0–156 weeks) (Table ). The slip angle was assessed using the frog lateral or cross-table lateral radiographs and classified as mild, moderate, or severe [7
] (Table ). Minimum followup was 2 months (mean, 37 months; range, 2–96 months). Institutional review board approval was obtained for this study in both institutions.
Characteristics of the patients with intact and disrupted physeal integrity*
The preoperative status of the hips was classified using the system based on the onset of symptoms [3
]. Using the acute/chronic classification, 11 slips were classified as acute, 40 as acute-on-chronic, and 31 as chronic. With the stable/unstable classification [35
], hips that allowed walking without or with crutches were defined as stable and those that did not allow walking as unstable. Twenty-four patients were unable to walk and therefore were classified as unstable and 58 were stable (Table ).
Clinical classifications of the 82 hips with SCFE and intraoperative physeal integrity
Only hips classified as unstable, acute, or acute-on-chronic were operated on as emergencies. Subcapital realignment of the epiphysis was performed for the moderate and severe slips using surgical hip dislocation and an extended retinacular soft tissue flap (modified Dunn procedure) [14
], whereas mild stable slips only had surgical hip subluxation for osteoplasty of the prominent anterior metaphysis combined with pinning in situ. The technique of surgical hip dislocation has been described in detail [20
]. Briefly, the dislocation approach includes a trochanteric flip osteotomy, and a Z-shaped capsular incision is used to access the joint. When we were concerned by lack of mechanical stability of the physis or when capsulotomy revealed a hematoma and/or visible disconnection, we avoided the risk of stretching or rupturing the retinacular vessels to the epiphysis by pinning the femoral head in situ before subluxation. To avoid tension or rupture of the retinaculum when reducing the slipped epiphysis, an extended retinacular flap was created [21
]. The first step was careful subperiosteal resection of the part of the stable greater trochanter proximal to the physis including all external rotators. Proximally this dissection was extended onto the neck as a longitudinal incision of the periosteum anterior to the retinaculum and distally the dissection was extended starting with a longitudinal periosteal incision reaching the most proximal fibers of the gluteus maximus tendon. The periosteum then was meticulously peeled off the lateral and posterior neck from the superior border of the lesser trochanter to the attachment of the retinaculum near the border of the epiphysis. The flap so created contains the deep branch of the medial femoral circumflex artery, the anastomoses with the inferior gluteal artery, and its retinacular end branches; it clearly is longer than with the retinacular tunneling produced with the classic Dunn procedure [14
] and therefore allows better compensation of adverse stretching during manipulation. After developing the posterolateral flap portion, we created an anteromedial flap containing a constant branch of the medial femoral circumflex artery, running in the synovial surface of Weitbrecht’s ligament and giving blood supply to the inferomedial portion of the epiphysis [43
], again with strictly subperiosteal dissection. Both flaps were connected posteriorly and allowed circumferential access to the osseous neck. An important part of the procedure was resection of the callus formation on the posterior neck before manual reorientation of the epiphysis. Resection of callus from the posterior neck before reorientation of the epiphysis is documented in the reports of 68 of the 75 hips with subcapital reorientation, including all 28 hips with complete physeal disruption.
We intraoperatively classified physeal integrity as intact or disrupted. The mechanical stability of the physis was considered intact if the periosteum was intact and if several deep chisel cuts were necessary to separate the epiphysis as part of the reorientation procedure (Fig. ). The physis was considered disrupted when the epiphysis was completely mobile without the need to free the physis (Fig. ). The presence of an intracapsular hematoma was not considered in this classification and was not always present. Integrity of the retinaculum and of its attachment on the epiphysis was evaluated by visual inspection at the time of surgical dislocation and presentation of the femoral head-neck junction. The intraoperative physeal integrity was intact in 54 hips and disrupted in 28 hips (Table ).
An intraoperative photograph shows the periosteum of the femoral head is stretched but intact (arrow).
Fig. 2 The intraoperative photograph shows the femoral head is in a dislocated position. The physis is disrupted, and the periosteum is torn (arrow). A mobile metaphyseal fragment with callous formation (triangle) is present. The femoral head was pinned prophylactically (more ...)
We determined the sensitivity and specificity of the two clinical classification systems (acute/acute-on-chronic/chronic and stable/unstable) to predict the presence of intraoperatively confirmed physeal instability (disrupted physis). All statistical analyses were performed with Microsoft® Excel (Microsoft®, Redmond, WA, USA) and SPSS 16.0 (SPSS Institute, Chicago, IL, USA).