Intraoperative loose flexion gap may restrict postoperative knee flexion after J-curve design posterior-stabilized total knee arthroplasty

IntroductionAlthough soft tissue tension during total knee arthroplasty (TKA) has been targeted to achieve equal flexion and extension gaps, such a perfect gap is not always obtained. This study was performed to investigate the impact of difference between flexion and extension gaps on postoperative knee flexion angle.Materials and methodsWe reviewed 107 consecutive TKAs using a J-curve design posterior-stabilized prosthesis. Soft tissue tension was measured intraoperatively using an offset-type tensor under 30 lb force of joint distraction with the patella reduced. All TKAs were performed in a uniform manner including the subvastus approach and without use of a pneumatic tourniquet. We assessed the association between knee flexion angle 1 year after TKA and the difference between flexion and extension gaps using Pearson's product-moment correlation and multiple regression analysis with age, sex, body mass index, diagnosis, history of diabetes mellitus, preoperative flexion angle, and gap difference as explanatory variables.ResultsThe difference between flexion and extension gaps showed a slight negative correlation with postoperative knee flexion angle in univariate analysis (r=-0.20, 95% CI, -0.38 to -0.01, p=0.04). Multiple regression analysis showed that the gap difference was an independent factor associated with postoperative knee flexion angle (beta=-0.89, 95% CI, -1.60 to -0.18, p=0.01).ConclusionsThe difference between flexion and extension gaps was negatively correlated with postoperative knee flexion angle. Looser flexion gap compared with extension gap should be avoided in J-curve design posterior-stabilized TKA.