Relationships of Posterior Condylar Offset Change to Condylar Length and Pre/Postoperative Range of Motion in Total Knee Arthroplasty

This study investigated the relationships of pre- to postoperative changes in posterior condylar offset（PCO）to differences in condylar length and range of motion in posterior stabilized（PS）-type total knee arthroplasty（TKA）. Subjects and Methods: We studied 40 knees of 40 patients（10 males and 30 females）treated by PS-type TKA. Slide calipers were used to measure condyle lengths intraoperatively and PCO was measured by standard X-ray. The patients were divided into two groups based on a pre- to postoperative change in PCO of ≥ 3mm or＜3mm, with the differences in both condylar length and range of motion compared between groups. The mean differences in condyle lengths were 2.6mm（33 knees）and 4.3mm（7 knees）in cases with PCO changes of＜3mm and ≥ 3mm, respectively. The means in the respective groups were −6° and −7° for preoperative extension, 116° and 118° for preoperative flexion, −3° and −4° for postoperative extension, and 131° and 129° for postoperative flexion. There was no significant difference in the range of motion between the groups. Cases with a large difference in condylar lengths were likely to have a small PCO postoperatively; however, the postoperative range of knee flexion was not significantly related to a small postoperative PCO. These findings suggested that preoperative range of knee motion, age, and type of TKA could influence both the postoperative range of motion and PCO.