Variables affecting functional outcome in floating knee injuries

The surgical outcome of floating knee injuries is difficult to predict. The high-velocity nature of the injury, complex fracture pattern and associated soft tissue/visceral injuries may have some impact on the functional outcome. The present study evaluates the variables affecting the clinical and radiological outcomes of floating knee injuries.

The clinical, radiological and functional outcome (Karlstrom and Olegrud criteria) of 89 patients with 90 floating knee injuries were evaluated at the end of one year who were managed in our level 1 trauma center between January 2013 and December 2016. The details of the injury, fracture pattern, management and complications were collected retrospectively from their records.

There were 81 (91.1%) males and 8 (8.9%) females with mean age of 34.34 ± 12.28 years. The mean time for tibia and femur union was 9.52 (±6.6) and 10.5 (±7.37) months. There was significant delay (p < 0.005) in time taken for union in segmental femur fractures (14.3 ± 9.6 months) compared to nonsegmental femur fractures (8.68 ± 5.18 months). Such significant difference in time taken for union was not seen in tibial segmental (10.6 ± 4.62 months) and nonsegmental fractures (9.05 ± 7.27 months). As per the Karlstrom and Olegrud criteria, there were 22 (24.4%) excellent, 26 (28.9%) good, 24 (26.7%) fair and 11 (12.2%) poor outcome. There were 15 patients with malunited tibia, 6 with malunited femur, 10 with limb length discrepancy and 39 with knee stiffness. 28 (33.3%) patients underwent major additional procedures such as bone grafting, re-fixation or bone transport or tendon transfer. It was observed that open tibia fracture, segmental fracture, intra-articular fracture, additional surgical procedures, initial external-fixator (ex-fix) application were significantly associated with development of knee stiffness, limb shortening, malalignment and unsatisfactory (Karlstrom and Olegrud fair to poor) functional outcome.

Open tibial fractures, segmental fractures, intraarticular involvement, additional surgical procedures and initial external fixator application are the poor prognostic indicators of floating knee injuries.