title: Femoral neck fractures after arthroscopic femoral neck osteochondroplasty for femoroacetabular impingement.
abstract: OBJECTIVE
  The objective of this study was to evaluate the rate, associated risk factors and outcome of insufficiency femoral neck fractures following arthroscopic femoral neck osteochondroplasty for femoroacetabular impingement.
  
  
  METHODS
  Between 2005 and 2009, a consecutive series of 376 arthroscopic femoral osteochondroplasties for femoroacetabular impingement were performed and analysed. Seven postoperative fractures were found and comprise the fracture group. The amount of femoral head-neck bone resected as assessed on follow-up cross table lateral views, as well as age, gender, height, weight and BMI, was compared between the fracture group and the entire collective. Subjective outcome was recorded using the WOMAC score.
  
  
  RESULTS
  Seven fractures (1.9 %) were identified. All occurred in males at an average of 4.4 weeks postoperatively and were considered insufficiency fractures. The fracture group had a significantly higher mean age (p = 0.01) and height (p = 0.013). Within the fracture group, alpha angles were lower (p = 0.009) and resection depth ratios were higher (p < 0.001). The femoral offset was significantly higher (p = 0.016) in the fracture group and in male patients (p < 0.001). The cut-off value for resection depth ratio on cross table lateral radiograph was 18 % of the femoral head radius. After a mean follow-up of 20 months, an inferior WOMAC (p = 0.030) was recorded in the fracture group.
  
  
  CONCLUSIONS
  Femoral neck insufficiency fractures were identified in 1.9 % of our arthroscopic femoral osteochondroplasty cases. Significant new pain following a period of satisfactory recovery after arthroscopic femoral neck osteochondroplasty should alert the surgeon to the possibility of this complication. If a resection depth ratio of more than 18 % is recognized on the postoperative cross table lateral view, particularly in male patients with a high femoral head-shaft offset, the risk of postoperative insufficiency fracture is increased. This study not only defines the complication rate, but also identifies associated risk factors and determines the influence on the postoperative subjective short-term result. Important information for both the patient and orthopaedic surgeon is provided and may have a direct consequence on the postoperative protocol.
authors.affiliation: Department of Orthopaedics, University of Zurich Balgrist, Forchstrasse 340, 8008, Zurich, Switzerland, patrick.zingg@balgrist.ch.
authors.forename: Patrick O
authors.initials: PO
authors.lastname: Zingg
authors.forename: Tobias C
authors.initials: TC
authors.lastname: Buehler
authors.forename: Vaughan R
authors.initials: VR
authors.lastname: Poutawera
authors.forename: Amin
authors.initials: A
authors.lastname: Alireza
authors.forename: Claudio
authors.initials: C
authors.lastname: Dora
mesh_terms: D000328:Adult; D001178:Arthroplasty / Q000009:adverse effects* / Q000379:methods; D057925:Femoracetabular Impingement / Q000175:diagnosis / Q000601:surgery*; D005265:Femoral Neck Fractures / Q000175:diagnosis / Q000209:etiology*; D005270:Femur Head / Q000000981:diagnostic imaging / Q000601:surgery; D005272:Femur Neck / Q000000981:diagnostic imaging / Q000601:surgery; D015775:Fractures, Stress / Q000175:diagnosis / Q000209:etiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012307:Risk Factors; D055815:Young Adult