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Predicting Risk of Contralateral Slip in Unilateral Slipped Capital Femoral Epiphysis

Posterior Epiphyseal Tilt Increases and Superior Epiphyseal Extension Reduces Risk

Maranho, Daniel A., MD, PhD1,2; Ferrer, Mariana G., MD1; Kim, Young-Jo, MD, PhD1; Miller, Patricia E., MS1; Novais, Eduardo N., MD1

doi: 10.2106/JBJS.18.00440
Scientific Articles
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Background: Femoral morphology may influence the etiology of slipped capital femoral epiphysis (SCFE). We investigated whether radiographic parameters of femoral head-neck morphology are associated with a subsequent contralateral slip in patients presenting with unilateral SCFE.

Methods: We evaluated 318 patients treated for unilateral SCFE between 2000 and 2017. There were 145 males (46%), and the mean age in the series was 12.4 ± 1.7 years. The patients were followed for a minimum of 18 months or until the development of a contralateral slip (70 patients, 22%). We measured the epiphyseal tilt, epiphyseal extension ratio, alpha angle, and epiphyseal angle of the uninvolved, contralateral hip at initial presentation. Multivariable logistic regression analysis was used to assess whether femoral measurements were associated with the occurrence of a contralateral slip. Receiver operating characteristic (ROC) curves were used to determine optimal thresholds of radiographic measures to determine an increased risk of a contralateral slip. A number-needed-to-treat (NNT) analysis was conducted to evaluate the effectiveness of the femoral measurement thresholds in preventing a contralateral slip.

Results: Multivariable analysis, controlling for triradiate cartilage status, identified the lateral tilt angle and the superior epiphyseal extension ratio as independent factors associated with the likelihood of a contralateral slip. For each additional degree of posterior tilt, the odds of a contralateral slip increase by 8% (odds ratio [OR] = 1.08; 95% confidence interval [CI] = 1.02 to 1.14; p = 0.008), and for each 0.01 increase in the superior epiphyseal extension ratio, the odds of a contralateral slip decrease by 6% (OR = 0.94; 95% CI = 0.88 to 0.99; p = 0.03). A threshold for the epiphyseal tilt of 10° corresponded to a predicted probability of a contralateral slip of 54% in patients with open triradiate cartilage and an NNT of 3.3.

Conclusions: In patients presenting with unilateral SCFE, a higher posterior tilt of the epiphysis increases the risk while an increased superior extension of the epiphysis reduces the risk of a contralateral slip. Our findings may assist the discussion about contralateral prophylactic pinning in patients with unilateral SCFE.

Level of Evidence: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

1Department of Orthopedic Surgery, Boston Children’s Hospital, Boston, Massachusetts

2Department of Biomechanics, Medicine and Rehabilitation of the Locomotor System, Ribeirao Preto Medical School, University of Sao Paulo, Ribeirao Preto, Brazil

E-mail address for E.N. Novais:

Investigation performed at Boston Children’s Hospital, Boston, Massachusetts

Disclosure: No specific source of funding was available for this study. On the Disclosure of Potential Conflicts of Interest forms, which are provided with the online version of the article, one or more of the authors checked “yes” to indicate that the author had other relationships or activities that could be perceived to influence, or have the potential to influence, what was written in this work (

Copyright © 2019 by The Journal of Bone and Joint Surgery, Incorporated
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