Comparison of Intraoperative Soft Tissue Balance Between Cruciate-Retaining and Posterior-Stabilized Total Knee Arthroplasty Performed by a Newly Developed Medial Preserving Gap Technique.

Abstract

Medial stability of the knee is considered to be associated with good clinical results after total knee arthroplasty (TKA). This study aimed to compare intraoperative soft tissue balance between cruciate-retaining (CR) and posterior-stabilized (PS) TKA performed by a newly developed medial preserving gap technique, which aimed at preserving medial stability throughout the range of motion. Seventy CR-TKAs and 70 PS-TKAs were performed in patients with varus type osteoarthritis with the novel technique guided by tensor measurements. Final intraoperative soft tissue balance with femoral trial component in place and patellofemoral joint reduced, including the joint component gap and varus/valgus ligament balance (varus angle), with the knee at 0° (full extension), 10° (extension), 30°, 45°, 60°, 90° (flexion), 120°, and 135° (deep flexion), was measured with Offset Repo-Tensor under 40 lbs of joint distraction force. The medial compartment gap (MCG), lateral compartment gap, and medial joint looseness (MCG-polyethylene insert thickness) at each flexion angle were calculated from the measured joint component gap and varus ligament balance, and compared between CR-TKA and PS-TKA. The MCGs from extension to deep flexion of the knee showed no significant differences between CR-TKA and PS-TKA. The lateral compartment gaps in PS-TKA from 30° to 60° of knee flexion was significantly larger than those in CR-TKA (P < .05). Medial joint looseness showed no significant differences between CR-TKA and PS-TKA which is consistent within 1 mm from extension to flexion of the knee. PS-TKA similarly achieved medial stability comparable to CR-TKA using the medial preserving gap technique.