Although total knee arthroplasty (TKA) using a medial pivot insert reportedly improves kinematics compared with a symmetrical insert, improvements in patient-reported outcomes have not yet been reported. The aim of this study was to determine whether insert designs influenced patient-reported outcomes.
Seventy TKAs for osteoarthritis were randomly allocated to a symmetrical dish insert (SD group: 35 knees) or medial pivot insert (MP group: 35 knees). Thirty-two of the SD group (74.4 ± 6.6 years old) and 33 of the MP group (73.8 ± 6.0 years old) completed the two-year follow-up. The knee range of motion (ROM) and 2011 Knee Society score (2011KSS) were analyzed pre-operatively and postoperatively.
There was no difference in pre-operative ROM or 2011KSS (Symptom: 7.3 ± 5.9 in SD group, 8.4 ± 5.4 in MP group, P = 0.432; Satisfaction: 12.6 ± 6.9 in SD group, 11.8 ± 5.9 in MP group, P = 0.581; Activity: 35.8 ± 18.1 in SD group, 35.2 ± 18.6 in MP group, P = 0.883). At two years, although both group showed good improvement, there were no differences in ROM or 2011KSS (Symptom: 19.3 ± 5.0 in SD group, 18.3 ± 4.1 in MP group, P = 0.351; Satisfaction: 24.0 ± 7.6 in SD group, 22.9 ± 7.9 in MP group, P = 0.548; Activity: 60.3 ± 14.8 in SD group, 54.3 ± 17.3 in MP group, P = 0.137).
The medial pivot insert was not superior to the symmetrical insert in patient-reported outcomes at two years after TKA.