Midlevel Constraint Without Stem Extensions in Primary Total Knee Arthroplasty Provides Stability Without Compromising Fixation.

Background: Many total knee arthroplasty (TKA) systems allow for so-called midlevel constraint (MLC) articular bearings that can be used with primary implants. The purpose of this study is to report the early outcomes with MLC bearings in primary TKA.

Materials/methods: From December 2005 to June 2015, minimum 2-year follow-up was available on 96 patients (103 TKA) who underwent primary TKA with an MLC bearing using the Vanguard Total Knee System. Outcomes included pain, Knee Society clinical and functional score, range of motion, and need for revision.

Results: Mean follow-up was 5 years (range, 2-11 years). Range of motion improved from 103 to 113. Knee Society clinical and function scores improved from 28 and 43 to 88 and 62, respectively. There were 10 manipulations (9.9%). There were no failures for aseptic loosening of any components; however, 10% of patients were lost to follow-up. There were 3 revisions (3%): 1 patellar tendon rupture, 1 open lysis of adhesions for stiffness, and 1 2-stage treatment of infection.

Conclusion: In cases of intraoperative medial collateral ligament incompetence, severe deformity, or valgus deformity requiring release of the lateral collateral ligament, the use of MLC showed good survivorship with no cases of aseptic loosening or instability.