Introduction: Although 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 methods: We 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.
Results: The 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 (β = - 0.89, 95% CI, - 1.60 to - 0.18, p = 0.01).
Conclusions: The 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.
Keywords: Knee; Primary arthroplasty; Range of motion; Soft tissue balance; Tensor device.