Abstract
There have been many reports on the clinical outcomes of Oxford unicompartmental knee
arthroplasty (UKA); however, none have investigated the influence of flexion angle
after UKA on clinical outcomes. The objective of this study was to clarify the relationship
between outcomes and the postoperative maximum flexion angle and reveal the necessary
factors for maximum flexion angle ≥ 140 degrees which is considered necessary for
Asian populations. We categorized 212 UKA patients into the following three groups
based on the postoperative maximum flexion angle: group 1 had flexion angle ≥ 140
degrees in 80 patients (38%), group 2 had 130 degrees ≤ flexion angle < 140 degrees
in 80 patients (38%), and group 3 had flexion angle < 130 degrees in 52 patients (24%).
Furthermore, we compared the postoperative clinical outcomes between the three groups
and conducted multivariable regression analyses to assess parameters affecting the
flexion angle. Postoperative Knee Society function scores for group 1 was significantly
higher than for group 3. Group 1 had higher mean knee injury and osteoarthritis outcome
scores (KOOS) in all subscales and significantly higher KOOS scores in the sports
and quality of life subscales compared with group 2 and in all subscales compared
with group 3. Multivariable logistic regression showed that preoperative flexion angle
and tibial component posterior slope were associated with maximum flexion angle ≥
140 degrees. Maximum flexion angle ≥ 140 degrees after Oxford UKA improved the clinical
results, particularly for patient-reported outcomes. Furthermore, the tibial posterior
slope was an important factor in achieving maximum flexion angle ≥ 140 degrees in
UKA patients.
Keywords
unicompartmental knee arthroplasty - deep flexion - Asian populations - patient-reported
outcomes - tibial posterior slope
