Does Prophylactic Pinning Affect the Proximal Femur Morphology in Slipped Capital Femoral Epiphysis?

BACKGROUND: The role of prophylactic pinning of the contralateral hip in unilateral SCFE is well established in patients with risk factors for developing contralateral slip. The effect of prophylactic pinning on the growth and morphology of the hip is not well documented in the literature. We aimed to study the effect of prophylactic pinning on the residual growth and morphology of the proximal femur.

MATERIALS & METHODS: The institutional database was searched for all unilateral SCFE cases for the period 2011 to 2020. A total of 171 unilateral SCFE cases were identified. All the radiographs were scanned and those patients who had follow-up X-rays till skeletal maturity were included in the study. Prophylactic pinning was performed using 6.5 mm fully threaded cancellous screws in supine position on a radiolucent table. The following radiological parameters were measured on the post-operative X-rays and at skeletal maturity: (i) neck length (NL), (ii) neck-shaft angle (NSA), (iii) femoral offset (FO), (iv) articulo-trochanteric distance (ATD) and (iv) tip-apex distance (TAD) by two different observers.

RESULTS: The mean age of the cohort was 13.7 years. ATD decreased from the mean value of 25.67 mm in post-operative radiographs to 20.84 mm in final follow-up radiographs. The NL, FO, and TAD were found to be increasing with age with mean final follow-up values of 55.35 mm, 41.41 mm, and 6.19 mm respectively compared to post-operative mean values of 50.95 mm, 37.4 mm, and 4.69 mm. There was no significant change in the neck-shaft angle. The mean post-operative NSA was 132.9° and it was 131.8° at final follow-up radiographs.

CONCLUSION: Prophylactic pinning in unilateral SCFE does not stop the growth of the proximal femur completely. The ATD decreases in all the patients with prophylactic screw fixation probably due to the discrepancy in growth between the trochanteric apophysis and proximal femoral physis. The clinical effects of this subtle change in the morphology of the proximal femur need further investigation.

LEVEL OF EVIDENCE: Level IV Case series.