Knee Dislocation from Minor Trauma in Morbidly Obese Patients

OBJECTIVES: To present a series of atraumatic knee dislocations in obese and morbidly obese patients. METHODS: An IRB approved retrospective study was preformed at a level 1 tertiary care trauma center. Eighteen patients who presented with a knee dislocation from a minor injury were included in the study. Charts, Radiographs, MRI’s were reviewed and patients were contacted in to examine them at latest follow up. We include patients in our database from 2001-2011. RESULTS: The mean age at presentation was 33 (range of 15-74 years) with 4 males and 14 females. The average BMI was 43 range (34- 64.4) with an average follow up of 29 months (range 9- 72 months) Five patients (27%) had a popliteal artery injury and 8 (44.4%) had a peroneal nerve injury at presentation. All 5 had a vascular repair, and 4/8 patients had return of peroneal nerve. Surgical repair was preformed on 10 individuals. The average operating time for ligament reconstruction was 183% of that with injury matched patients. All patients had external fixation to protect the repair post op which was removed at 6 weeks post op and accompanied with a manipulation intra-op. Two patients failed reconstruction, one at 5 years due to a second injury and another at 4 months from a fall. We were unable to fit custom braces on these individuals so it was abandoned. Opposite knees were determined to have hyper mobility in all 16 patients who had an adequate exam. Eight operative patients who complied with therapy had an average range of 91.4 degrees (60-110). One patient was noncompliant by not taking therapy and ended up with only 40 degrees of flexion..The non operative patients had an avg ROM of 53.6 degrees (range 30-90) and may have been that they had less aggressive rehabilitation. Three of these had gone on to TKA. CONCLUSION: Knee dislocations from minor falls occur in obese patients and often have neurovascular complications. Surgical reconstruction is more time consuming and more difficult then in normal weighted individuals. It may be preferable to non operative treatment