Compass Knee Hinge favored over standard postop knee braces

Postoperative use of Compass Knee Hinge improved ligament stability and reduced need for revision surgery.

Temporarily using a hinged external fixator for postoperative stabilization of knee dislocations may improve ligament stability and decrease the need for revision surgery, according to researchers at the University of Alabama, Birmingham.

A prospective, randomized study showed that 27% of patients who wore standard postop knee braces had recurring instability and 23% of these patients had failed ligament groups, the researchers said. In contrast, only 4% of patients who wore Compass Knee Hinge (CKH; Smith & Nephew) postoperatively for about six weeks had recurring instability; just 3% of these patients had failed ligament groups.

Stephen L. Brown, MD, of Birmingham, Ala., presented the results of the study at the 2005 International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine Congress (ISAKOS). “Regardless of whether you look at patient failures or ligament complex failures, there are statistically significant differences between groups, favoring the Compass Hinge with P values of <.05 and <.01 respectively,” he said.

Treatment creates a ‘Catch 22’

Brown said that knee injuries have historically had a poor prognosis attributed to either motion problems or persistent instability. “A review of English literature on surgical treatment of knee dislocations published from 1994 to 2003 shows that on average, 38% of patients require a return trip to the OR for motion problems, and 37% of patients were unstable despite reconstruction," he said. "In treating patients with these horrible injuries, we find ourselves in a bit of a ‘Catch 22.’ Do we allow early motion to avoid arthrofibrosis, but perhaps risk instability? Or do we delay motion to improve instability, while risking arthrofibrosis?”

According to Brown, the Compass Knee Hinge allows early controlled motion in the sagittal plane, while restricting motion in the coronal and axial planes. The researchers recommend using the CKH for about six weeks as a supplement to ligament reconstruction if an early and aggressive motion rehabilitation protocol is employed.

Results support use of CKH

The study included 21 patients with 22 dislocations in Group A (standard postop knee brace) and 22 patients in Group B (CKH), both with a minimum 24-month follow-up. Postoperative protocols were identical between the groups. Patients began range of motion (ROM) on the first postop day; both groups were allowed to weight-bear with the hinge or brace locked in extension.

The surgeons used several techniques to reconstruct the ligaments. They operated on the PCL using the tibial inlay with two femoral tunnels. They reconstructed the ACL using the hamstring or bone tendon bone graft; the posterolateral corner, using the modified two-tailed technique; and the posteromedial complex, with construction of the medial collateral ligament and posterior oblique ligament reconstruction.

After the failures were revised, the researchers found no significant differences in final ROM, International Knee Documentation Committee (IKDC) results and Lysholm knee scores. Eighteen percent of patients in both groups returned to the OR for motion problems. After the failures were revised, final IKDC objective results demonstrated normal to near-normal knees in greater than 80% of patients in both groups. Mean ROM for patients in Group A was 1° to 115° compared to 1° to 126° in Group B. During revision reconstruction of failed ligaments, all patients received a Compass Hinge.

For more information:
Stannard J, Brown S, Bankston L, et al. Stabilization of knee dislocations using a hinged external fixator: A prospective randomized study. #189. Presented at the 2005 International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine Congress. April 3-7, 2005. Hollywood, Fla.