Probability analysis of sequential SCFE (PASS score)

Abstract

Purpose The study aimed to develop a scoring system based on clinical and radiological findings to predict the risk of a sequential slipped capital femoral epiphysis (SCFE). Methods Paediatric patients with unilateral SCFE and at least two years of radiographic follow-up were screened for inclusion. Medical records were reviewed for multiple variables including age, gender, body mass index (BMI), stability of SCFE, and time to sequential presentation. Radiographic analysis included triradiate physeal status, Risser staging, superior epiphyseal extension ratio (EER), posterior epiphyseal angle (PEA), posterior sloping angle (PSA) and slip severity. Results In total, 163 patients (88 male, 54%, 75 female, 46%) met inclusion criteria. Of those, 65 (40%) with a mean age of 11.9 ± 1.3 years developed sequential SCFE at a mean of 9.8 ± 6.4 months after the initial slip. Eight independent variables were statistically different (p < 0.05) between unilateral and sequential groups. Following multivariate analysis, Risser stage and triradiate status were no longer significant and did not influence the strength of the final model (overall area under the curve (AUC) = 0.954) and were consequently excluded. We developed the PASS score using three radiographic parameters using chosen cut-off values that were close to their maximized value and weighted the point value assigned to each parameter based on the strength of predictor. Conclusion A PASS score of three or higher predicts a high probability of sequential SCFE with 95% confidence and may warrant prophylactic screw fixation. PASS score calculation can be used to predict a sequential SCFE and provide an objective method to determine the utility prophylactic screw fixation. Level of Evidence II

Can we still use X-rays to predict contralateral slip in primary unilateral slipped capital femoral epiphysis?

“…On the basis of these parameters, a Probability Analysis of Sequential SCFE (PASS score) was created. The amount of ≥3 points anticipates high risk of contralateral slip of above 28% [31]. This study suggests similarly to our findings that a thorough physical and radiological assessment of the patient and not a single radiological parameter should be considered before deciding on the prophylactic contralateral hip fixation [31].…”

The contralateral hip in slipped capital femoral epiphysis: Is there an easy-to-use algorithm to support a decision for prophylactic fixation?

“…However, other studies have shown that the vast majority will develop a subsequent slip within 28 months. 1,8,9,11,27,28 This study did not present the natural history for the contralateral hip in children with a unilateral SCFE. Children were already selected from the initial study population, where a prophylactic fixation of the contralateral hip was performed.…”

“…25 Triradiate cartilage assessment for skeletal maturity as a predictor for a subsequent slip in the second hip has been advocated. 11,23,25,26 However, Danino et al 27 showed that triradiate status and Risser's grade did not influence their final multivariate analysis strength, but so did epiphyseal extension ratio, posterior epiphyseal angle and posterior sloping angle. When evaluating radiographs, the experience and the variation between clinicians must be considered.…”

Idiopathic Slipped Capital Femoral Epiphysis: Demographic Differences and Similarities between Stable, Unstable, and Valgus Types

“…Information regarding the status of the tri-radiate physis in SCFE patients has been primarily used when considering prophylactic fixation of the opposite hip when a patient with a unilateral SCFE presents. Popejoy et al [ 36 ] were instrumental in pointing this out, and the literature regarding the status of the tri-radiate physis in SCFE patients seems to concentrate solely on the consideration for prophylactic fixation of the opposite hip [ 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ]. Our findings that the status of the tri-radiate physis in SCFE patients is also correlated with SCFE severity (LESA) is likely new and needs further corroboration from other centers.…”