Abstract
A new design of the so-called “guided-motion” total knee arthroplasty (TKA) is expected
to produce normal-like kinematics. The implant behaves strictly as a mechanically
constraint-guided motion system. However, no previous reports have demonstrated the
most appropriate surgical technique or soft-tissue balance that would reproduce ideal
kinematics. The purpose of this study was to clarify the relationship between soft-tissue
balance and the intraoperative kinematics of guided-motion TKA. In this study, intraoperative
kinematics of 95 patients whose TKA was performed with a guided-motion prosthesis
(Journey II BCS Smith and Nephew) were measured using the computed tomography (CT)-free
navigation system. All procedures were performed via the same soft-tissue balancing
technique, which focused on the medial compartment because guided-motion TKA must
acquire medial stability to induce medial pivot motion. We measured the extension
and flexion osteotomy gaps using a force-controlled compartment-specific ligament
tensioner with a distraction force of 80 N for each compartment and divided patients
into three groups based on the relationship between extension and flexion joint osteotomy
gaps of the medial compartment: group1– loose flexion gap, group 2–equal joint gap,
and group 3–tight flexion gap. We compared the preoperative demographic characteristics,
implant alignment, and intraoperative kinematics among the three groups. There was
no difference between the preoperative demographic characteristics and postoperative
implant alignment in the three groups. The relative tibial internal rotational angles
in groups 1 and 2 were significantly larger than that in group 3 at 60°, 90°, and
maximum flexion (p < 0.05). The appropriate soft-tissue balance of the medial compartment for guided-motion
TKA was an equal joint osteotomy gap or a larger flexion than extension gap. A tight
flexion gap should be avoided.
Keywords
total knee arthroplasty - guided-motion - soft-tissue balance - medial gap technique
- intraoperative kinematics