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The authors are from the Department of Orthopaedic Surgery (AGG, STG) and the Division of Vascular Surgery (ADS), Henry Ford Hospital, Detroit, Michigan.
The authors have no relevant financial relationships to disclose. Correspondence should be addressed to: Andrew G. Georgiadis, MD, Department of Orthopaedic Surgery, Henry Ford Hospital, 2799 W Grand Blvd, Detroit, MI 48202 ( [email protected]).
The epidemic of obesity in the United States has had undeniable effects on the practice of musculoskeletal medicine.1 The estimated cost of obesity-related health care was $147 billion in 2008 and is expected to continue to rise.2,3 Treatment of such patients is often fraught with costlier care, higher complication rates, longer surgeries, worse outcomes, and negative prognosticators in both adult and pediatric orthopedic care.4-6 Regardless of the results of national efforts to improve nutrition and combat the obesity epidemic, the orthopedic surgeon needs to remain vigilant in recognizing new presentations of classic musculoskeletal injuries. Seemingly innocuous trauma in an obese patient can be deferred or overlooked entirely, with devastating consequences. One such injury is the recently reported "ultra-low-velocity (ULV) knee dislocation (KD)." This is a clinical entity whose presentation, treatment, and complications have been described at a few major centers and that seems associated exclusively with obesity.7-10
Knee dislocation is defined by loss of the tibiofemoral articulation. Traditionally, high-velocity dislocations result from vehicular trauma and are associated with the highest rates of nerve and vascular injury, while low-velocity dislocations are characterized as sports injuries.11,12 There have been recent reports of complete KDs in patients with high body mass index (BMI), sustained merely during falls from standing, falls from a single step, and noncontact injuries. The first descriptions of ULV KD included 2 morbidly obese female patients who had falls while walking.13 These patients' courses were characterized by complete tibiofemoral dislocation, popliteal artery occlusion, open revascularization procedures, and early transfemoral amputation in 1. This was the first series to describe the delay to presentation in such patients, intraoperative difficulty, postoperative complications, and difficult prosthetic fitting.
In the laboratory, 650 psi of force is required to overcome soft tissue restraints and dislocate a knee anteriorly.14 During the gait cycle, as much as 2000 lb of force can be transferred across the tibiofemoral...