Femoral Neck Growth and Remodeling With Free-Gliding Screw Fixation of Slipped Capital Femoral Epiphysis

Abstract

Background: Treatment of stable slipped capital femoral epiphysis (SCFE) most commonly involves in situ fixation with a standard cannulated screw, leading to physeal arrest. Recently, Pega Medical (Laval, Canada) introduced the free-gliding (FG) SCFE screw, which employs a growth-friendly, telescopic design. This study examines femoral neck growth and remodeling over the first 2 postoperative years in stable SCFE treated with FG versus standard screws. Methods: We retrospectively reviewed 32 hips (19 SCFE, 13 prophylactic) in 16 patients treated with FG screws for stable SCFE. We also reviewed 102 hips (63 SCFE, 19 prophylactic, 20 controls) in 55 patients treated with standard screws. Immediate postoperative radiographs were compared with 1- and 2-year follow-up images. Results: For the overall study cohort, mean age at surgery was 12.2±1.9 years, with a mean slip angle of 26.9±18.0 degrees. In FG SCFE hips, the alpha angle remodeled 12.9±19.2 degrees in the first postoperative year (P=0.018) and articulotrochanteric distance decreased by 4.2±4.6 mm at 2 years (P=0.018). In standard SCFE hips, the alpha angle remodeled 4.3±11.3 degrees at 1 year (P=0.014), while articulotrochanteric distance decreased by 4.5±3.2 mm at 2 years (P<0.001). By 2 years, FG screws lengthened more in prophylactic (4.8±3.4 mm) than SCFE hips (1.7±1.8 mm, P=0.027). Conclusions: Greater remodeling of femoral neck cam deformity occurs when treating SCFE using an FG screw. Further research is required to measure the impact of this finding on femoroacetabular impingement and degenerative arthritis. In addition, FG screws allow ongoing growth of prophylactically treated hips, while standard screws promote coxa breva. Level of Evidence: Level III—retrospective comparative, therapeutic study.

Is the modified Dunn’s procedure superior to in situ fixation? A systematic review and meta-analysis of comparative studies for management of moderate and severe slipped capital femoral epiphysis

“…For instance, the use of unthreaded fixation using the Hansson hook-pin, proximally threaded screws, or growing implants, such as the Pega Medical Free Gliding (FG) screws and Synthes SCFE screws, may encourage more remodeling of the hip, preventing coxa breva following fixation. [33][34][35][36] Previous research has shown that in moderate to severe slips, the incidence of remodeling was 50% following conventional pinning. 37 The extent of improvement in remodeling and its impact on long-term clinical outcomes, with the use of these systems, however, have yet to be fully ascertained.…”

Is there a persistent capital femoral epiphysis growth after screw fixation for slipped capital femoral epiphysis?

“…An alternative may be to use fully threaded screws; however, they are associated with less compression in cases of instability. Some surgeons use ‘inverse threaded’ or ‘free-gliding’ screws to prevent growth disorders [ 40 ]. We do not recommend the use of pins because of the risk of complications due to secondary displacement.…”

Leg length discrepancy after in situ fixation with screw for slipped capital femoral epiphysis

“…Traditionally, SCFE has been treated by in situ fixation of the femoral head with a single cannulated screw to inhibit further slippage 5 , 6 . In situ fixation with screws can consequentially cause a physeal arrest, which leads to a relative shortening of the femoral neck 7 – 9 and subsequent LLD 4 , 10 .…”

“…Thus, our results indicate that monitoring for LLD in mild slip may be unnecessary. Moreover, the alternative growth-preserving implant for in situ pinning 5 , 18 , which has been a longstanding interest in treating SCFE, may be unnecessary for mild slips. It seems reasonable to carefully monitor the LLD in patients with moderate slips.…”