Clinical and Radiographic Characteristics of Atypical Slipped Capital Femoral Epiphysis
Authors: Chung Chae Hoon , Ko Kyung Rae , Kim Joo Hwan , Shim Jong Sup 
Published: January 2019

Background:
Slipped capital femoral epiphysis (SCFEs) can be idiopathic or atypical (associated with renal failure, radiation therapy, and endocrine disorders). It is important to estimate the likelihood that atypical SCFE shows different clinical and radiographic characteristics and complications with typical SCFEs.

Methods:
We retrospectively reviewed 53 patients (66 hips) with SCFEs managed between 1995 and 2016. Sex, age, weight, height, the duration of symptoms the laterality of the slip, and complications were recorded. Bilateral hip and lower extremity long bone radiographs were utilized to record slip angle, genu valgus deformity. Statistical analyses were performed.

Results:
Among 53 children (32 boys and 21 girls) with 66 SCFEs, 22 children had 29 atypical SCFEs, and 31 children had 38 typical SCFEs. The average age at the time of presentation for the initial SCFEs was 10.9±0.3 years. The average duration of symptoms was 14.1±21.8 weeks. The average Southwick slip angle difference was 23.3±14.8 degrees. There are 43 mild, 13 moderate, and 10 severe SCFEs. 58 were classified as stable, and 8 were unstable. There were significant differences in terms of average age (10.4±2.6 y for atypical SCFEs, 11.2±1.4 for typical SCFEs; P=0.036), average weight (36.2±22.3 kg for patients with atypical slips, compared with 56.9±9.9 kg for those with typical slips; P<0.001), height (132.1±17.6 cm for those with atypical slips, compared with 148.9±12.1 for those with typical slips; P<0.001), and the body mass index (19.4±5.6 kg/cm2 for those with atypical slips, compared with 25.8±4.6 for those with typical slips; P<0.001). In the group of 22 children with atypical slipped capital epiphysis, there were 19 children with neoplasm (8 neuroblastomas, 3 medulloblastomas, 3 retinoblastomas, 2 ependymomas, 1 craniopharyngioma, 1 Wilms tumor, 1 immature teratoma), 4 children with primary endocrine disorder. We categorized atypical SCFEs in 3 groups by etiology; endocrine disorder–associated (ENDA) SCFEs, chemotherapy-associated (CTA) SCFEs, and radiation therapy–associated (RTA) SCFEs. Subjects of RTA were included if exposed to pelvic irradiation or total body irradiation. There were 4 ENDA, 9 RTA, and 16 CTA. Atypical SCFEs had significantly more valgus slips (P<0.001) and genu valgus deformity (P<0.001) compared with in the group of typical slipped capital epiphysis. Among the group of atypical SCFEs, children with CTA had significantly low body weight, height, and body mass index.

Conclusions:
The markedly greater incidence of valgus displacement of proximal femoral epiphysis and genu valgum in childhood cancer survivors with pelvic irradiation and chemotherapy may be associated with atypical SCFE. The authors conclude that in pediatric cancer survivors with hip pain, consideration should be given to atypical SCFE with valgus slip and long-term follow-up of lower extremity alignment.

Level of Evidence:
Level III—retrospective comparative study. See instructions for authors for a complete description of levels of evidence.