Study offers quantitative support that UKA restores native knee kinematics better than TKA
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TAMPA, Fla. — Results of a pilot study presented at the Orthopaedic Research Society Annual Meeting provided quantitative evidence that unicompartmental knee arthroplasty restored native kinematics better than total knee arthroplasty.
“Unicompartmental knee arthroplasty more closely approximates native knee kinematics as observed by its kinematic similarities with the contralateral knee,” William J. Anderst, PhD, said.
Using rising from a chair, which is a common activity of daily living that requires deep knee flexion and with which many patients correlate satisfaction after knee arthroplasty, Anderst, assistant professor and director of the biodynamics laboratory at the University of Pittsburgh, and colleagues observed changes in knee motion during chair rise activities for patients after TKA and UKA. Researchers established different hypotheses for how they thought the knees with TKA would behave vs. knees with UKA regarding tibiofemoral kinematics and extent of varus or posterior alignment for seven women and eight men who underwent knee arthroplasty.
Surgeries were performed with a Navio (Smith & Nephew) navigation system to guide implant placement.
The patients’ operated knees had Kellgren-Lawrence scores greater than 2 and their contralateral knees had Kellgren-Lawrence scores less than 2.
Seven patients underwent TKA with a fixed-bearing cruciate-retaining prosthesis. Eight patients underwent fixed-bearing UKA. All patients participated in one preoperative and one postoperative chair rise testing session that consisted of three chair rises, the results of which were averaged.
Researchers used a combination of tracking sensors, CT scans, modeling and other methods to determine knee joint movements during the testing in both the operated and contralateral knees.
Among the findings, Anderst said TKA postoperatively corrects varus deformity toward mechanical alignment and it approximates neutral mechanical alignment.
“Postoperatively the tibia of TKA-operated knees was posterior to the femur,” he said.
According to the abstract, post-TKA knees were more medial and posterior than
post-UKA knees during 20 to 90 degrees of flexion, and both of these differences were statistically significant.
“No significant differences were observed between the UKA knee and the contralateral knees at any flexion angle,” Anderst said.
“Future research is needed to investigate how these findings correlate to long-term functional outcomes and symptomatic improvement in patients,” he said.
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Heidenreich E, et al. Paper 109. Presented at: Orthopaedic Research Society Annual Meeting; Feb. 4-8, 2022; Tampa, Fla.
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