Knee arthroplasty with a medially conforming ball-and-socket tibiofemoral articulation provides better function.

BACKGROUND

A knee design with a ball-and-socket articulation of the medial compartment has a femoral rollback profile similar to the native knee. Compared to a conventional, posterior-stabilized knee design, it provides AP stability throughout the entire ROM. However, it is unclear whether this design difference translates to clinical and functional improvement.

QUESTIONS/PURPOSES: We asked whether the medially conforming ball-and-socket design differences would be associated with (1) improved ROM; and (2) improved American Knee Society, WOMAC, Oxford Knee, SF-36, and Total Knee Function Questionnaire scores compared to a conventional, fixed-bearing posterior-stabilized TKA.

PATIENTS AND METHODS

We enrolled 82 patients in a single-center, single-blinded, randomized, controlled trial comparing the medially conforming ball-and-socket design knee prosthesis to a posterior-stabilized total knee prosthesis. Our primary end point was ROM. Our secondary end points were American Knee Society, WOMAC, Oxford Knee, SF-36, and Total Knee Function Questionnaire scores. All patients were followed at 1 and 2 years.

RESULTS

The mean ROM was 100.1° and 114.9° in the posterior-stabilized and medially conforming ball-and-socket groups, respectively. The physical component scores of SF-36 and Total Knee Function Questionnaire were better in the medially conforming ball-and-socket group. We found no difference in American Knee Society, WOMAC, and Oxford Knee scores.

CONCLUSIONS

Both implant designs similarly relieved pain and improved function. The medially conforming ball-and-socket articulation provided better high-end function as reflected by the Total Knee Function Questionnaire.

LEVEL OF EVIDENCE

Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.