Influence of Design on the Range of Motion After Total Knee Arthroplasty

Summary

The results of the range of motion (ROM) in 271 knee replacements were investigated and their design features were discussed. The 271 knees included 37 total condylar (TC) knees, 47 posterior stabilizer (PS) knees, 97 kinematic condylar (KC) knees, 44 Miller-Galante (MG) knees, and 46 Interax (IX) knees. The postoperative average flexion angle was 102.9° in TC, 109.1° in PS, 107.6° in KC, 106.5° in MG, and 116.3° in IX. The average postoperative ROM improvement angle of each group was +0.6° in TC, −7.9° in PS, −2.3° in KC, +3.0° in MG, and +9.8° in IX. These results suggest that low or moderate tibiofemoral joint conformity with posterior cruciate ligament-preserved designs (MG and IX) was better than the more highly constrained and posterior cruciate ligament-sacrificed design (TC) which does not allow roll-back motion at flexion. On the other hand, the stabilizer design (PS) acts as a roll-back mechanism but might not contribute enough to the sliding mechanism which becomes more important than the rolling motion at deep flexion. Recent design trends (IX) of posterior femoral condyles with short height and small radius could present an alternative solution for this sliding mechanism.