title: Risk factors for the development of heterotopic ossification after knee dislocation.
abstract: BACKGROUND
  Results of treatment for acute knee dislocations and multiligament knee injuries may be influenced by a multitude of patient- and injury-related factors, including neurologic function, vascular status, ipsilateral fractures, and joint stability. The development of heterotopic ossification (HO) may nullify any benefits of reconstruction, because it can cause stiffness and discomfort. Identifying factors associated with HO after knee dislocation may help identify patients who might benefit from prophylaxis.
  
  
  OBJECTIVE
  The purposes of this study were (1) to identify specific risk factors for the development of HO in patients with knee dislocation; and (2) to elucidate the relationship between the presence of absence of HO and postoperative range of motion.
  
  
  METHODS
  Between 2005 and 2010, we performed 101 multiligament reconstructions for patients with knee dislocations, of which 91 (90%) in 91 patients were available for followup at a minimum of 6 months (mean, 18 months; range, 6-44 months), and were reviewed here. AP and lateral radiographs were reviewed for all patients and HO was classified according to the Mills and Tejwani classification system. This knee dislocation cohort was separated into two groups based on the presence or absence of HO for comparison. Using a significance level of p < 0.05 for factors in the univariate analyses, we identified potential variables for a multivariate logistic regression model to identify risk factors predicting development of HO in patients with multiligament knee injuries; multivariate analysis then was performed to mitigate the influence of potentially confounding variables. Thirty patients (34%) developed HO after multiligament knee injury in our series.
  
  
  RESULTS
  Posterior cruciate ligament reconstruction was the only independent predictor of HO that we identified (odds ratio, 6.3; 95% confidence interval, 1.2-34.6). Patients who developed HO were more likely to develop stiff knees and undergo surgery (50%; 15 of 30 patients) versus those without HO (12%; seven of 58 patients) to attempt to restore functional range of motion (p < 0.001).
  
  
  CONCLUSIONS
  HO is a common complication after knee dislocation and can diminish range of motion and cause patients to undergo further surgery. Posterior cruciate ligament reconstruction is an independent risk factor for the development of HO. Strategies to identify risk factors for, and safe prevention of, HO after multiple ligament injury and surgery should be investigated going forward.
  
  
  METHODS
  Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Surgery, University of Toronto, c/o St Michael's Orthopaedic Associates, 55 Queen Street E, Suite 800, Toronto, ON, M5C 1R6, Canada, wheland@smh.ca.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Whelan
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Dold
authors.forename: Tomce
authors.initials: T
authors.lastname: Trajkovski
authors.forename: Jas
authors.initials: J
authors.lastname: Chahal
mesh_terms: D000328:Adult; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D031221:Knee Dislocation / Q000150:complications* / Q000175:diagnosis / Q000601:surgery; D007718:Knee Injuries / Q000150:complications* / Q000175:diagnosis / Q000601:surgery; D008023:Ligaments, Articular / Q000293:injuries* / Q000601:surgery; D008297:Male; D009864:Ontario / Q000453:epidemiology; D019637:Orthopedic Procedures / Q000379:methods*; D009999:Ossification, Heterotopic / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D011183:Postoperative Complications; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D013997:Time Factors