title: Predictors of Time to Union After Operative Fixation of Closed Ankle Fractures.
abstract: BACKGROUND
  Ankle fractures are common and represent a significant burden to society. We aim to report the rate of union as determined by clinical and radiographic data, and to identify factors that predict time to union.
  
  
  METHODS
  A cohort of 112 consecutive patients with isolated, closed, operative malleolar ankle fractures treated with open reduction and internal fixation was retrospectively reviewed for time to clinical union. Clinical union was defined based on radiographic and clinical parameters, and delayed union was defined by time to union >12 weeks. Injury characteristics, patient factors and treatment variables were recorded, and statistical techniques employed included the Chi-square test, the Student's T-test, and multivariate linear regression modeling.
  
  
  RESULTS
  Forty-two (37.5%) of patients who achieved union did so in less than 12 weeks, and 69 (61.6%) of these patients demonstrated delayed union at a mean of 16.7 weeks (range, 12.1-26.7 weeks), and the remaining patient required revision surgery. Factors associated with higher rates of delayed union or increased time to union included tobacco use, bimalleolar fixation, and high energy mechanism (all p<0.05). In regression analysis, statistically significant negative predictors of time to union were BMI, dislocation of the tibiotalar joint, external fixation for initial stabilization and delay of definitive management (all p<0.05).
  
  
  CONCLUSIONS
  Patient characteristics, injury factors and treatment variables are predictive of time to union following open reduction and internal fixation of closed ankle fractures. These findings should assist with patient counseling, and help guide the provider when considering adjunctive therapies that promote bone healing.
  
  
  METHODS
  Prognostic, Level IV: Case series.
authors.affiliation: Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Matson
authors.affiliation: Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina.
authors.forename: Kamran S
authors.initials: KS
authors.lastname: Hamid
authors.affiliation: Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina.
authors.forename: Samuel B
authors.initials: SB
authors.lastname: Adams
mesh_terms: D000368:Aged; D064386:Ankle Fractures / Q000601:surgery*; D015992:Body Mass Index; D015331:Cohort Studies; D016267:External Fixators; D005260:Female; D000072039:Fracture Dislocation / Q000150:complications; D005593:Fracture Fixation, Internal; D017102:Fracture Healing; D005596:Fractures, Closed / Q000601:surgery*; D006801:Humans; D008297:Male; D000070799:Open Fracture Reduction; D012189:Retrospective Studies; D012907:Smoking / Q000009:adverse effects; D013997:Time Factors
keywords: ankle injuries; bone healing; internal fixation; trauma