title: Incidence of radiographic cam-type impingement in young patients (<50) after femoral neck fracture treated with reduction and internal fixation.
abstract: BACKGROUND
  Cam-type femoral impingement is caused by structural abnormalities of the hip and is recognized as a cause of degenerative hip arthritis. Identifiable etiologies of this structural abnormality include congenital malformation, pediatric hip disease, and malunion of femoral neck fractures after internal fixation.
  
  
  OBJECTIVE
  The purpose of this study was to determine the prevalence of radiographic impingement in healed Orthopaedic Trauma Association (OTA) type 31B fractures treated with reduction and internal fixation.
  
  
  METHODS
  Seventy OTA 31B hip fractures treated with internal fixation were identified from our institutional trauma database and radiographs were retrospectively reviewed for signs of impingement. Mean follow-up was 53 months after fracture. Alpha angle, Mose templates, and femoral head retroversion were the measurements used to determine impingement.
  
  
  RESULTS
  The overall prevalence of any sign of radiographic impingement was 75%. Alpha angle was elevated in 32 hips (46%), asphericity was present in 46 femoral heads (65%), and femoral head retroversion was present in 26 hips (37%). The rates were highest in displaced subcapital fractures (OTA 31B-3) with a 63% (13/19) prevalence of elevated alpha angle, 68% (14/19) prevalence of asphericity, and 47% (10/19) prevalence of retroversion.
  
  
  CONCLUSIONS
  Prevalence of radiographic signs of impingement in this population is higher than expected based on population-based controls. Surgeons must be vigilant about reduction and fixation of femoral neck fractures. Malunion should be recognized as early intervention may be beneficial in improving long-term outcomes.
authors.affiliation: Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Wendt
authors.affiliation: Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA.
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Cass
authors.affiliation: Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA.
authors.forename: Robert R
authors.initials: RR
authors.lastname: Trousdale
keywords: alpha angle; cam lesion; femoral neck fracture; femoroacetabular impingement