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Boyle MJ, Lirola JF, Hogue GD, et al. The alpha angle as a predictor of contralateral slipped capital femoral epiphysis. J Child Orthop. 2016;10(3):201-7doi: 10.1007/s11832-016-0732-x.
Boyle, M. J., Lirola, J. F., Hogue, G. D., Yen, Y. M., Millis, M. B., & Kim, Y. J. (2016). The alpha angle as a predictor of contralateral slipped capital femoral epiphysis. Journal of children's orthopaedics, 10(3), 201-7. https://doi.org/10.1007/s11832-016-0732-x
Boyle, Matthew J, et al. "The alpha angle as a predictor of contralateral slipped capital femoral epiphysis." Journal of children's orthopaedics vol. 10,3 (2016): 201-7. doi: https://doi.org/10.1007/s11832-016-0732-x
Boyle MJ, Lirola JF, Hogue GD, Yen YM, Millis MB, Kim YJ. The alpha angle as a predictor of contralateral slipped capital femoral epiphysis. J Child Orthop. 2016 Jun;10(3):201-7. doi: 10.1007/s11832-016-0732-x. Epub 2016 Apr 06. PMID: 27052742; PMCID: PMC4909647.
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J Child Orthop. 2016 Jun;10(3):201-7. doi: 10.1007/s11832-016-0732-x. Epub 2016 Apr 06.

The alpha angle as a predictor of contralateral slipped capital femoral epiphysis.

Journal of children's orthopaedics

Matthew J Boyle, Jose F Lirola, Grant D Hogue, Yi-Meng Yen, Michael B Millis, Young-Jo Kim

Affiliations

  1. Department of Orthopaedic Surgery, Harvard Medical School, Children's Hospital Boston, Boston, USA. [email protected].
  2. Department of Pediatric Orthopaedics, Starship Children's Hospital, Auckland Central, Private Bag 92 024, Auckland, 1142, New Zealand. [email protected].
  3. Department of Orthopaedic Surgery, Harvard Medical School, Children's Hospital Boston, Boston, USA.
  4. Department of Pediatric Orthopaedics, Hospital Universitario Virgen del Rocío, Seville, Spain.
  5. Department of Pediatric Orthopaedics, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.

PMID: 27052742 PMCID: PMC4909647 DOI: 10.1007/s11832-016-0732-x

Abstract

PURPOSE: Contralateral hip involvement in slipped capital femoral epiphysis (SCFE) is common. Femoral head-neck asphericity, as measured by an elevated alpha angle, has not previously been assessed with respect to SCFE risk. Our aim was to assess the utility of the alpha angle in predicting contralateral SCFE.

METHODS: We retrospectively reviewed 168 patients (94 males) managed surgically for unilateral SCFE between 2001 and 2013 who had a minimum of 18 months follow-up. The alpha angle, the posterior sloping angle (PSA), and the modified Oxford score were recorded for every patient at the time of initial SCFE presentation. Follow-up clinical records and radiographs were assessed to determine the presence of absence of contralateral SCFE.

RESULTS: Forty-five patients (27 %) developed a contralateral SCFE. Patients who developed a contralateral SCFE had a significantly higher alpha angle (51° vs 45°, p < 0.001) than patients who did not develop a contralateral SCFE. There was no significant difference in PSA or modified Oxford score (both p > 0.10) between patients who developed a contralateral SCFE and those who did not. Using a proposed alpha angle of 50.5° as a threshold for prophylactic fixation, 26 (58 %) of the 45 cases of contralateral SCFE in our study would have been prevented and 18 (15 %) of 123 patients would have undergone fixation unnecessarily.

CONCLUSIONS: We found the alpha angle to positively correlate with contralateral SCFE risk. Patients with significantly elevated alpha angles may be at greater risk of contralateral SCFE and benefit from further investigation or prophylactic hip fixation.

Keywords: Alpha angle; Fixation; Hip; Slipped capital femoral epiphysis

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