Revision knee arthroplasty with rotating hinge systems in patients with gross ligament instability.

Purpose: The clinical and radiographic outcomes after revision total knee arthroplasty (TKA) for instability with two rotating hinge knee prostheses were compared.

Methods: Fifty-one patients revised for TKA instability were prospectively randomized to either the Link Endo-Model (N = 26) or the EnduRo (N = 25). Clinical and radiographic outcome scores were compared pre-operatively and at 12 months' follow-up. Failure mechanisms were recorded.

Results: Age, BMI, operation, and tourniquet-time did not differ significantly between groups. Radiographic evaluation demonstrated correct implant alignment. The Endo-Model was implanted with a higher slope (p = 0.0001) and the mechanical lower extremity axis was straighter (p = 0.0323). Except for the patient function Knee Society Score and the Physical Health Component Summary Score in the EnduRo group, all clinical scores (range of motion/knee function Knee Society Score/Oxford Knee Score/Visual Analog Scale/Mental Health Component Summary Score) improved significantly for both prosthesis designs during the follow-up period. The Visual Analog Scale and Mental Health Component Summary score were significantly better (p = 0.045 and p = 0.0148) in the Endo-Model group at the 12 months' follow-up. In the EnduRo group 2 patients (8%) and in the Endo-Model group 1 patient (3.8%) had to be revised for infection.

Conclusion: Both prosthetic designs provide significant improvement in pain and function scores after TKA revision for gross instability. We found slight advantages in favor of the Endo-Model; however, no design yielded superior results throughout the study.