, Volume 472, Issue 2, pp 430-436

The Otto Aufranc Award. On the Etiology of the Cam Deformity: A Cross-sectional Pediatric MRI Study

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Femoroacetabular impingement (FAI) has been recognized as a common cause of hip pain as well as a cause of hip arthritis, yet despite this, little is known about the etiology of the cam morphology or possible risk factors associated with its development.


The purposes of our study were to determine when the cam morphology associated with FAI developed in a cross-sectional cohort study of pediatric patients pre- and postphyseal closure using MRI and whether increased activity level during the period of physeal closure is associated with an increased likelihood that the cam deformity will develop.


Alpha angles were measured at the 3 o’clock (anterior head-neck junction) and 1:30 (anterosuperior head-neck junction) positions in both hips with a cam deformity defined as an alpha angle ≥ 50.5° at the 3 o’clock position. Forty-four volunteers (88 hips) were studied: 23 with open physes (12 females, mean age 9.7 years; 11 males, age 11.7 years) and 21 with closed physes (five females, age 15.2 years; 16 males, age 16.2 years). Daily activity level using the validated Habitual Activity Estimation Scale was compared for patients in whom cam morphology did and did not develop.


None of the 23 (0%) patients prephyseal closure had cam morphology, whereas three of 21 (14%, p = 0.02; all males) postclosure had at least one hip with cam morphology. Daily activity level was higher (p = 0.02) for patients with the cam morphology (7.1 hours versus 2.9 hours). Mean alpha angles at the 3 o’clock head-neck position were 38° (95% confidence interval [CI], 37.2°–39.1°) in the open physes group and 42° (95% CI, 40.16°–43.90°) in the closed physes group; at the 1:30 head-neck position, they were 45° (95% CI, 44.0°–46.4°) in the open physes group and 50° (47.9°–52.3°) in the closed physes group.


The fact that cam morphology was present exclusively in the closed physeal group strongly supports its development during the period of physeal closure with increased activity level as a possible risk factor.

Level of Evidence

Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

This research project was funded through only internal funding, from the Children’s Hospital of Eastern Ontario Bone Health Research Group (LMW) and the Department of Surgery Research Fund (RBW) as well as The Discovery Fund (PEB).
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request.
Each author certifies that his or her institution approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained.
This research was performed at the Children’s Hospital of Eastern Ontario, Ottawa, Ontario, Canada.