Predictors of outcome of floating knee injuries in adults: 89 patients followed for 2-12 years.

Of the 98 floating knee injuries that were consecutively treated from 1987 to 1997, 89 patients were available for analysis. There were 80 males and 9 females, ranging from 15 to 70 years old. Average follow-up was 5 (2-12) years. Injury severity scores ranged from 18 to 45. 21 fractures were intra-articular. 55 fractures were open. Substantial comminuted and segmental fractures occurred in 57 cases and 35 cases, respectively. Multivariate analysis showed that increasing age was associated with delays in bony union and full weight bearing ability. An increase in the number of pack years smoked at the time of injury predicted the likelihood of knee stiffness, delays in bony union and full weight bearing ability. Higher injury severity scores were associated with delayed full weight bearing ability. The presence of open fractures predicted the likelihood of knee stiffness and delayed full weight bearing ability. Comminuted fractures were associated with malunion, and segmental fractures with delayed bony union. Using the outcome of floating knee injuries as fair or poor, according to Karlström and Olerud's criteria, we constructed a preoperative prognostic scoring scale which showed a sensitivity of 0.72 and a specificity of 0.90.