Epiphyseal Morphology Following Successful Modified Dunn Procedure for SCFE.

Abstract

Since its initial description, the modified Dunn procedure has emerged as a valuable surgical option for treating slipped capital femoral epiphysis (SCFE), particularly in cases of severe deformity. Previous literature has focused on complications and short-term results following this procedure, but little is known about the morphologic development of the upper femoral epiphysis following successful treatment with the modified Dunn technique, uncomplicated by osteonecrosis. A retrospective study was conducted, including all modified Dunn procedures performed by 7 surgeons from 4 centers. Patients who developed osteonecrosis or other significant healing complications were excluded. Demographic and clinical data were recorded from chart review. Preoperative and postoperative AP and frog lateral radiographs were analyzed for slip angle, AP alpha angle, lateral alpha angle, and Mose sphericity. Binary and stepwise linear regression were used to determine relationships between variables and femoral head sphericity. A total of 130 hips from 128 patients were identified and followed until at least full radiographic healing (mean follow-up 30.1 mo). Approximately one third of the cohort were each acute, acute-on-chronic, and chronic; 74 hips (57%) were unstable and 56 (43%) were stable. Based on the Mose sphericity scale, only 35 of the epiphyses (29.2%) were graded spherical, while 85 (70.8%) were aspherical in both the AP and lateral projections at the most recent follow-up. Female patients were more likely to be spherical compared with male patients (P=0.007), but patient age (P=0.5), temporal class (P=0.87), and Loder stability (P=0.36) were not significantly different between spherical and aspherical hips. Follow-up length showed moderate inverse correlation with joint space width but did not seem to correlate with slip angle (P=0.2), AP alpha angle (0.54), or lateral alpha angle (0.82). Our data suggests that even after a successful modified Dunn procedure uncomplicated by osteonecrosis, the femoral epiphysis is often aspherical and therefore not "normal." In addition, epiphyseal shape seems not to improve over time and joint space seems to narrow within our study's length of follow-up. Future investigations and longer follow-up may reveal potential etiologies and longer-term sequelae of these morphologic changes and determine the significance of these radiographic findings. Level IV.