The Free-Gliding screw for slipped capital femoral epiphysis : is it safe, does it glide, and does age matter?

Fixation techniques used in the treatment of slipped capital femoral epiphysis (SCFE) that allow continued growth of the femoral neck, rather than inducing epiphyseal fusion in situ, have the advantage of allowing remodelling of the deformity. The aims of this study were threefold: to assess whether the Free-Gliding (FG) SCFE screw prevents further slip; to establish whether, in practice, it enables lengthening and gliding; and to determine whether the age of the patient influences the extent of glide.

All patients with SCFE who underwent fixation using FG SCFE screws after its introduction at our institution, with minimum three years' follow-up, were reviewed retrospectively as part of ongoing governance. All pre- and postoperative radiographs were evaluated. The demographics of the patients, the grade of slip, the extent of lengthening of the barrel of the screw and the restoration of Klein's line were recorded. Subanalysis was performed according to sex and age.

A total of 19 hips in 13 patients were included. The mean age of the patients at the time of surgery was 11.5 years (9 to 13) and the mean follow-up was 63 months (45 to 83). A total of 13 FG SCFE screws were used for the fixation of mild or moderate SCFE, with six contralateral prophylactic fixations. No hip with SCFE showed a further slip after fixation and there were no complications. Lengthening occurred in 15 hips (79%), with a mean lengthening of the barrel of 6.8 mm (2.5 to 13.6) at final follow-up. Remodelling occurred in all hips with lengthening of the barrel. There was statistically more lengthening in patients who were aged < 12 years, regardless of sex (p = 0.002).

The FG SCFE screw is effective in preventing further slip in patients with SCFE. Lengthening of the barrel occurred in most hips, and thus allowed remodelling. This was most marked in younger children, regardless of sex. Based on this study, this device should be considered for use in patients with SCFE aged < 12 years instead of standard pinning in situ.Cite this article: Bone Joint J 2023;105-B(2):215-219.