Greater postoperative relatively medial loose gap at 90 degrees of flexion for varus knees improves patient-reported outcome measurements in anatomical bi-cruciate retaining total knee arthroplasty

Background: The purpose of the present study was to measure the intraoperative joint gap using tensor device and pre- and, postoperative joint stability at 0, 30 and 90 degrees of flexion using stress radiography and to identify whether these factors influence patient-reported outcome measurement (PROM) in anatomical bi-cruciate retaining (BCR) knee arthroplasty (TKA). Methods: Fifty-three knees with preoperative varus osteoarthritis of the knee underwent anatomical BCRTKA with oblique three-degree angle femorotibial joint line. The intraoperative medial and lateral joint gap using a tensor device and gap difference (lateral minus medial; varus laxity) were also calculated. Postoperative joint stability was measured using stress radiographs. PROM was also evaluated at 15 years postoperatively. The effect of intraoperative and postoperative joint stabilities on PROMs were analyzed using Spearman's rank correlation analysis. Results: Intraoperative greater difference between medial joint gap at 140 degrees and 0 degrees of flexion showed significant positive correlation with postoperative function of patellofemoral joint. Intraoperative varus laxity at extension improved postoperative symptoms in 2011 Knee Society Score (2011 KSS); greater postoperative lateral stability at 30 and 90 degrees of flexion with the varus stress test was associated with the better patient expectation in 2011 KSS. Postoperative medial laxity at 90 degrees of flexion with the valgus stress test positively correlated with the patient expectation and satisfaction in 2011 KSS. Conclusions: Surgeons should notice that the postoperative lateral stability and medial laxity at 90 degrees of flexion improved PROM in anatomical BCR TKA. (C) 2020 Elsevier B.V. All rights reserved.