title: CAM-type impingement in the ankle.
abstract: BACKGROUND
  Anterior ankle impingement with and without ankle osteoarthritis (OA) is a common condition. Bony impingement between the distal tibia and talus aggravated by dorsiflexion has been well described. The etiology of these impingement lesions remains controversial. This study describes a cam-type impingement of the ankle, in which the sagittal contour of the talar dome is a non-circular arc, causing pathologic contact with the anterior aspect of the tibial plafond during dorsiflexion, leading to abnormal ankle joint mechanics by limiting dorsiflexion.
  
  
  METHODS
  A group of 269 consecutive adult patients from the University of Iowa Hospitals and Clinics who were treated for anterior bony impingement syndrome were evaluated as the study population. As a control group, 41 patients without any evidence of impingement or arthrosis were evaluated. Standardized standing lateral ankle radiographs were evaluated to determine the contour of the head/neck relationship in the talus. Two investigators made all the radiographic measurements and intra- and inter-observer reliability were measured.
  
  
  RESULTS
  34% of patients were found to have some anterior extension of the talar dome creating a loss of the normal concavity at the dorsal medial talar neck. A group of 36 patients (13%) were identified as having the most severe cam deformity in order to assess any correlation with coexisting radiographic abnormalities. In these patients, a cavo-varus foot type was more commonly observed. Comparison with a control group showed much lower rates of anterior-medial cam-type deformity of the talus.
  
  
  CONCLUSIONS
  Cam type impingement of the ankle is likely a distinct form of bony impingement of the ankle secondary to a morphological talar bony abnormality. Based on the findings of this study, this form of impingement may be related to a cavovarus foot type. In addition, there may be long term implications in the development of ankle OA.
  
  
  METHODS
  Level III.
authors.affiliation: University of Iowa Hospitals and Clinics Iowa City, IA 52242, USA. Ned-amendola@uiowa.edu
authors.forename: Ned
authors.initials: N
authors.lastname: Amendola
authors.forename: Newhoff
authors.initials: N
authors.lastname: Drew
authors.forename: Tanawat
authors.initials: T
authors.lastname: Vaseenon
authors.forename: John
authors.initials: J
authors.lastname: Femino
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tochigi
authors.forename: Phinit
authors.initials: P
authors.lastname: Phisitkul
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000843:Ankle Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D002648:Child; D005260:Female; D006801:Humans; D007592:Joint Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D011859:Radiography; D013628:Talus / Q000000981:diagnostic imaging*; D055815:Young Adult