Knee dislocations occur as the result of high-energy trauma. These devastating knee injuries have been addressed with a myriad of surgical approaches, and treatment has evolved from primary repair to reconstruction of torn ligaments. Early surgery has shown benefit over delayed surgery1. Cast immobilization has given way to early rehabilitation; however, stiffness remains the greatest obstacle to successful knee function. Balancing the risk of stiffness with the need for a stable environment to encourage healing of multiple ligament reconstructions is a challenge and the impetus for this investigation by Stannard et al.
This study is a prospective randomized controlled trial on the use of a hinged external fixator as an augment to a staged reconstruction protocol. Patients either received a hinged external fixator that was placed during the posterior cruciate ligament (PCL), posterolateral corner, or posteromedial corner reconstruction and retained for six weeks until staged anterior cruciate ligament (ACL) reconstruction, or were treated with a hinged knee brace with an early range-of-motion protocol after undergoing identical surgery. The patients were followed for twelve months and evaluated with standard subjective scores as well a surgeon-graded ligament examination. A total of 100 patients with 103 dislocations were enrolled, and seventy-seven patients (seventy-nine knees) had complete follow-up. The investigators found that the experimental group experienced fewer failed ligament reconstructions compared with the control group: 7% with the hinged external fixator versus 21% with the brace. However, the results with regard to return to work, range of motion, and return to activities had nonsignificant trends favoring the control group.
The authors are to be applauded, as knee dislocations have been the subject of few prospective studies, let alone randomized clinical trials. This work is of high quality and adds substantially to the existing literature. The authors conclude that hinged external fixators should be considered for high-grade knee dislocations in which the risk of recurrent instability is so great that it outweighs the potential increase in stiffness and impacts return-to-work considerations. Treatment with an adjunctive external fixator significantly decreased the risk of ligament reconstruction failure—a finding highly relevant to surgeons caring for these complex injuries. This conclusion may be less relevant for a lower-grade injury.
One striking finding of this study is that while the experimental cohort achieved the desired outcome of preventing failure of ligament reconstruction, external fixation did nothing to improve subjective outcome scores. The current literature on knee dislocation outcomes is humbling, with subjective outcome scores in the mid to high 80s on a 100-point scale, irrespective of surgical technique used1,2. The outcomes in the current study are consistent, with Lysholm scores for each group of 87 at twelve months, and an increase to 90 among those with twenty-four months of follow-up. These results support the conclusion that patients who sustain these devastating knee injuries rarely achieve full function, but substantial improvement can be seen with early surgical intervention.
The authors highlight the limitations of their study, notably the absence of blinded examiner evaluation, a loss of 23% of the original cohort, and a short follow-up period of twelve months. However, the investigators did an excellent job of achieving acceptable numbers in a challenging trauma population. Overall, this prospective randomized controlled trial is refreshing in a field whose literature consists primarily of retrospective case series, technique reports, and expert opinion.