The purpose of this study was to determine the oblique plane deformity in slipped upper femoral epiphysis.

A retrospective radiographic review was undertaken in patients admitted with a slipped upper femoral epiphysis between March 2008 and October 2010. Patients in whom a CT scan had been performed in addition to plain radiographs were assessed further. Angular deformity in the coronal and sagittal planes were measured by the angle formed between the femoral neck and a line perpendicular to the physis on the AP pelvic radiograph and the axial CT scan respectively. The magnitude and direction of the resultant deformity was defined in the oblique plane. Additional demographic data (gender, age, side, procedure and complications) was collected.

Seven girls, average age of 12 (range 10 – 13) and 6 boys, average age of 13 (range 10 – 15) were identified. The slip was bilateral in 2, left sided in 6 and right sided in 5 cases. Two patients were pinned in situ, 8 had surgical dislocation performed to facilitate reduction prior to pinning and 3 patients had secondary procedures performed following in situ pinning. The average angulation in the oblique posteroinferior plane (25 degrees) was less than in the coronal (30 degrees) and the sagittal planes (62 degrees). The average magnitude was 67mm (range 31 – 88).

CT is useful adjunct particularly when a frog legged lateral view is not possible because of pain or the fear of further displacement. Determination of the deformity in the oblique plane may aid in positioning of the screw during in situ pinning and may be helpful in identifying patients in whom pinning maybe difficult.