title: The cam-type deformity of the proximal femur arises in childhood in response to vigorous sporting activity.
abstract: BACKGROUND
  The prevalence of a cam-type deformity in athletes and its association with vigorous sports activities during and after the growth period is unknown.
  
  
  OBJECTIVE
  We therefore compared the prevalence and occurrence of a cam-type deformity by MRI in athletes during childhood and adolescence with an age-matched control group.
  
  
  METHODS
  We retrospectively reviewed 72 hips in 37 male basketball players with a mean age of 17.6 years (range, 9-25 years) and 76 asymptomatic hips of 38 age-matched volunteers who had not participated in sporting activities at a high level.
  
  
  RESULTS
  Eleven (15%) of the 72 hips in the athletes were painful and had positive anterior impingement tests on physical examination. Internal rotation of the hip averaged 30.1° (range, 15°-45°) in the control group compared with only 18.9° (range, 0°-45°) in the athletes. The maximum value of the alpha angle throughout the anterosuperior head segment was larger in the athletes (average, 60.5° ± 9°), compared with the control group (47.4° ± 4°). These differences became more pronounced after closure of the capital growth plate. Overall, the athletes had a 10-fold increased likelihood of having an alpha angle greater than 55° at least at one measurement position.
  
  
  CONCLUSIONS
  Our observations suggest a high intensity of sports activity during adolescence is associated with a substantial increase in the risk of cam-type impingement. These patients also may be at increased risk of subsequent development of secondary coxarthrosis.
  
  
  METHODS
  Level II, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopedic Surgery, University of Bern, Inselspital, CH 3010 Bern, Switzerland. klaus.siebenrock@insel.ch
authors.forename: K A
authors.initials: KA
authors.lastname: Siebenrock
authors.forename: F
authors.initials: F
authors.lastname: Ferner
authors.forename: P C
authors.initials: PC
authors.lastname: Noble
authors.forename: R F
authors.initials: RF
authors.lastname: Santore
authors.forename: S
authors.initials: S
authors.lastname: Werlen
authors.forename: T C
authors.initials: TC
authors.lastname: Mamisch
mesh_terms: D000293:Adolescent; D000328:Adult; D001265:Athletic Injuries / Q000453:epidemiology / Q000473:pathology* / Q000503:physiopathology; D001490:Basketball; D002648:Child; D005269:Femur / Q000473:pathology*; D025981:Hip Injuries / Q000453:epidemiology / Q000473:pathology* / Q000503:physiopathology; D006621:Hip Joint / Q000473:pathology* / Q000503:physiopathology; D006801:Humans; D008297:Male; D010146:Pain / Q000209:etiology / Q000503:physiopathology; D015995:Prevalence; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D013557:Switzerland / Q000453:epidemiology; D014481:United States / Q000453:epidemiology; D055815:Young Adult