title: Hips with synovial chondromatosis may display the features of femoroacetabular impingement.
abstract: BACKGROUND
  Both synovial chondromatosis and femoroacetabular impingement present with hip pain and may lead to hip osteoarthritis. We present a small case series and describe the clinical presentation, investigation, and treatment of patients with synovial chondromatosis who also had cam-type femoroacetabular impingement involving the same hip.
  
  
  METHODS
  Five patients (four men and one woman with a mean age of thirty-four years [range, thirty to thirty-seven years]) with unilateral synovial chondromatosis of the hip presented with clinical and radiographic features of ipsilateral cam-type femoroacetabular impingement. The diagnosis of associated synovial chondromatosis was made on the basis of preoperative imaging in four of the cases. All patients were treated with surgical hip dislocation, excision of the synovial chondromatosis loose bodies, and reshaping of the femoral head-neck junction.
  
  
  RESULTS
  These hips exhibited radiographic features that are not typically seen with idiopathic cam-type femoroacetabular impingement, including femoral head hypertrophy, lateralization of the femoral head, and haziness in the acetabular fossa. None of the hips showed signs of advanced osteoarthritis intraoperatively. The alpha angle improved from a mean of 72.4° preoperatively to 42.6° postoperatively. At a mean of twenty-two months of follow-up, the patients had a mean Harris hip score of 80.6, substantially improved from the preoperative value of 39.
  
  
  CONCLUSIONS
  Hips with synovial chondromatosis may present with clinical and radiographic features resembling those of cam-type femoroacetabular impingement. As simultaneous treatment of both conditions is best accomplished with surgical hip dislocation rather than other, less-extensive surgical approaches, we recommend preoperative consideration of synovial chondromatosis in patients presenting with unilateral cam-type femoroacetabular impingement.
authors.affiliation: Department of Orthopaedics, Shafa Hospital, Iran University of Medical Sciences, Jaleh Street, Baharestan Square, 1157637131 Tehran, Iran. E-mail addresses for M. Abolghasemian: m-abolghasemian@tums.ac.ir; mn.abolghasemi@yahoo.com.
authors.forename: Mansour
authors.initials: M
authors.lastname: Abolghasemian
authors.affiliation: Department of Orthopaedics, Shafa Hospital, Iran University of Medical Sciences, Jaleh Street, Baharestan Square, 1157637131 Tehran, Iran. E-mail addresses for M. Abolghasemian: m-abolghasemian@tums.ac.ir; mn.abolghasemi@yahoo.com.
authors.forename: Kaveh
authors.initials: K
authors.lastname: Gharanizadeh
authors.affiliation: Division of Orthopaedics, University of Toronto, 600 University Avenue, Suite 476(A), Toronto, ON M5G 1X5, Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Kuzyk
authors.affiliation: Department of Orthopaedics, Shafa Hospital, Iran University of Medical Sciences, Jaleh Street, Baharestan Square, 1157637131 Tehran, Iran. E-mail addresses for M. Abolghasemian: m-abolghasemian@tums.ac.ir; mn.abolghasemi@yahoo.com.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Masdari
authors.affiliation: Mostafa Hospital, Shahed University, Italy Street, 1416643491 Tehran, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Fakharian
authors.affiliation: Division of Orthopaedics, University of Toronto, 600 University Avenue, Suite 476(A), Toronto, ON M5G 1X5, Canada.
authors.forename: Oleg
authors.initials: O
authors.lastname: Safir
mesh_terms: D000077:Acetabulum / Q000601:surgery; D000328:Adult; D001707:Biopsy, Needle; D015838:Chondromatosis, Synovial / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000601:surgery*; D003937:Diagnosis, Differential; D005260:Female; D057925:Femoracetabular Impingement / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000601:surgery; D005270:Femur Head / Q000601:surgery; D006617:Hip Dislocation / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000601:surgery*; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D019637:Orthopedic Procedures / Q000379:methods*; D010147:Pain Measurement; D016059:Range of Motion, Articular / Q000502:physiology; D012189:Retrospective Studies; D018570:Risk Assessment; D012494:Sampling Studies; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome