Abstract & Commentary
Synopsis: The incidence of heterotopic ossification associated with knee dislocations was approximately 25% in this study. Approximately half of these were severe.
Source: Stannard JP, et al. Heterotopic ossification associated with knee dislocation. Arthroscopy. 2002;18(8):835-839.
Knee dislocation, like other orthopaedic trauma, is often associated with high-energy trauma. A known complication of knee dislocations, regardless of treatment, is heterotopic bone formation. This can adversely affect outcome and severely restrict knee motion. Stannard and colleagues state that the purpose was to determine the prevalence of heterotopic ossification (HO) following knee dislocation.
Stannard et al reviewed 56 knee dislocations that were treated at their institution over a 2½ year period. They classified the injuries based on Wascher’s modification of Schenk’s grading system. Basically, this system assigns higher numbers to higher degrees of injury ranging from PCL intact injuries (KDI) to knee dislocations with periarticular fractures (KDV). Their treatment protocol involves reconstructing the PCL and associated posterolateral and/or posteromedial structures acutely with delayed ACL reconstruction.
A total of 14 of 56 dislocations developed HO, for an incidence of 25%. Half of these were considered severe (grade III or IV) HO. Stannard et al found a higher incidence with open dislocations (three fifths of patients). There was also a significant increase in HO formation seen with HO at other anatomical sites, motor vehicle vs. pedestrian injuries, and knees that developed arthrofibrosis. There was a trend toward significance with higher grade injuries and injuries that required irrigation and debridement. Interestingly, there was no association of HO with head injury in this study.
Comment by Mark D. Miller, MD
Knee dislocations are relatively uncommon but certainly not rare. Since the advent of automobile air bags, the incidence of these injuries appears to be on the rise. Accidents that may have previously been unsurvivable now roll into emergency rooms across the country with major extremity trauma, including knee dislocations. Stannard et al report 56 knee dislocations that they treated over a 2½ year period—about 2 a month. I have found that these injuries can seriously affect both your elective operative schedule and your lifestyle. Although arthrofibrosis is a well-recognized and even expected sequela of knee dislocations, the incidence of HO—25% in the current study—is higher than I expected.
Although this is a retrospective study and suffers all of the statistical problems associated with this form of research, this paper does highlight some key points that should make us consider some type of prophylaxis for HO (single dose radiation or perhaps indomethicin) in certain patients. These include patients with open dislocations, those who require a return to the OR for either lysis of adhesions or irrigation and debridement, and perhaps more severe injuries. This has not been routine practice, at least not in my hands but, as a result of this study, will be now.
Dr. Miller, Associate Professor, UVA Health System, Department of Orthopaedic Surgery, Charlottesville, VA, is Associate Editor of Sports Medicine Reports.