Acetabular fracture displacement, roof arc angles and 2 years outcome.

Four hundred and fifty acetabular fractures in a prospectively recorded cohort were studied. Forty-one patients had died, 201 had a follow-up of more than 2 years and 25 were excluded which left a study population of 176 patients. Harris Hip Score (HHS) and modified HHS were used as outcome instruments. Acetabular fracture displacement and roof arc angles converted into a Roof Arc Score were assessed and correlated with clinical outcome at 2 years follow-up. For surgically treated fractures with residual steps and diastases after operation the correlation between steps and 2 year outcome was good. The location of fracture lines in the acetabular dome, expressed as a Roof Arc Score, proved to be more important than the residual step for 2 years clinical outcome (p<0.05). The impact of location of fracture lines in the acetabular dome on clinical outcome disappeared when open reduction and internal fixation (ORIF) resulted in a perfect anatomic reduction, i.e. without any residual steps or diastases assessed in the three radiographic views. The general association between fracture diastases and functional outcome was poor, except for non-operatively treated fractures without measurable steps.