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Posterior Sloping Angle as a Predictor of Contralateral Slip in Slipped Capital Femoral Epiphysis
Paul M. Phillips, MBChB1; Joideep Phadnis, MBChB, MRCS1; Richard Willoughby, MBChB, FRACS1; Lyn Hunt, MSc, DPhil2
1 Orthopaedic Outpatients, Waikato Hospital, Pembroke Street, Hamilton 3204, New Zealand
2 Department of Statistics, University of Waikato, Hillcrest Road, Hamilton 3204, New Zealand
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Investigation performed at the Orthopaedics Department, Waikato Hospital, Hamilton, New Zealand, and the Department of Statistics, University of Waikato, Hamilton, New Zealand

Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. None of the authors, or their institution(s), have had any financial relationship, in the thirty-six months prior to submission of this work, with any entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, no author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.

Copyright © 2013 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2013 Jan 16;95(2):146-150. doi: 10.2106/JBJS.L.00365
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Slipped capital femoral epiphysis is a condition with potentially severe complications. Controversy remains as to when to undertake prophylactic pinning. We aimed to assess the utility of the posterior sloping angle as a predictor for contralateral slip in a large, multi-ethnic cohort including Polynesian children with a high incidence of slipped capital femoral epiphysis.


All patients presenting to our hospital between 2000 and 2009 were identified and records were reviewed to determine demographic data and determine whether they subsequently developed a contralateral slip. The presenting radiographs were reviewed and the posterior sloping angle was measured. Patients with bilateral slips at presentation and those without initial radiographs were excluded.


Records and radiographs of 132 patients were analyzed for the posterior sloping angle in the unaffected hip. Forty-two patients who had subsequently developed a contralateral slip had a mean posterior sloping angle (and standard deviation) of 17.2° ± 5.6°, which was significantly higher (p < 0.001) than that of 10.8° ± 4.2° for the ninety patients who had had a unilateral slip. Children who had developed a subsequent contralateral slip were significantly younger (11.1 years) than those who had developed a unilateral slip (12.2 years) (p < 0.001). If a posterior sloping angle of 14° were used as an indication for prophylactic fixation in this population, thirty-five (83.3%) of forty-two contralateral slips would have been prevented, and nineteen (21.1%) of ninety hips would have been pinned unnecessarily. The number needed to treat to prevent one subsequent contralateral slip is 1.79.


To our knowledge, this is the largest study to date that confirms that the posterior sloping angle is a reliable predictor of contralateral slip and can be used to guide prophylactic pinning. The posterior sloping angle is applicable in the high-risk Polynesian population and could be useful in preventing future slips in populations that are difficult to follow up.

Level of Evidence: 

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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