Abstract
Introduction
Appropriate intraoperative soft tissue balancing is recognized to be essential in total knee arthroplasty (TKA). However, it has been rarely reported whether intraoperative soft tissue balance reflects postoperative outcomes. In this study, we therefore assessed the relationship between the intra-operative soft tissue balance measurements and the post-operative stress radiographs at a minimum 1-year follow-up in cruciate-retaining (CR) TKA, and further analyzed the postoperative clinical outcome.
Methods
The subjects were 25 patients diagnosed with osteoarthritis with varus deformity and underwent primary TKA. The mean age at surgery was 72.0 ± 7.5 years (range, 47–84 years). The Surgeries were performed with the tibia first gap technique using CR-TKA (e motion, B. Braun Aesculap) and the image-free navigation system (Orthopilot). We intraoperatively measured varus ligament balance (°, varus angle; VA) and joint component gap (mm, center gap; CG) at 10° and 90° knee flexion guided by the navigation system, with the patella reduced. At a minimum 1-year follow-up, post-operative coronal laxity at extension was assessed by varus and valgus stress radiographs of the knees with 1.5 kgf using a Telos SE arthrometer (Fa Telos) and that at flexion was assessed by epicondylar view radiographs of the knees with a 1.5-kg weight at the ankle. After calculating postoperative VA and CG from measurements of radiographs, measurements and preoperative and postoperative clinical outcome, such as Knee Society Clinical Rating System (Knee score; KSS, Functional score; KSFS) and postoperative knee flexion, were analyzed statistically using linear regression models and Pearson's correlation coefficient.
Results
The mean follow-up duration was 22.0 months (range, 12–36 months). The average pre-operative KSS and KSFS was 57.0 points and 62.8, respectively, and the average post-operative scores were 98.4 points and 91.5, respectively. The both scores were significantly improved. The mean preoperative knee flexion angle was 121.8°, and postoperative knee flexion angle was 124.8°.ã��The mean pre- and post-operative joint component gaps at extension and flexion were 14.4 and 14.4 mm, and 15.6 and 16.5 mm, respectively. The mean pre- and post-operative values of varus ligament balance at extension and flexion were 2.5° and 2.7°, and 1.7° and 4.4°, respectively. Regression analysis revealed that the intraoperative CG was positively correlated with the postoperative CG at both extension and flexion (R = 0.45, P < 0.05; R = 0.52, P < 0.05, respectively) and intraoperative VA was positively correlated with the postoperative VA at extension (R = 0.52, P < 0.05) (Figure 1). Furthermore, postoperative flexion angle was positively correlated with the postoperative CG and VA at flexion (R=0.43, p<0.05, R=0.44, p<0.05, respectively) (Figure 2).
Conclusion
We revealed that intraoperative soft tissue balance reflect postoperative soft tissue balance in CR-TKA. Furthermore, postoperative lateral laxity at flexion may permit the improvement of postoperative flexion angle.
