Analytical medial unicondylar knee arthroplasty:surgical procedure and early clinical practice
Objective To report the surgical procedure,early radiographic outcomes and real-time change of joint space balance in analytical medial unicompartmental knee arthroplasty(UKA),and to explore the utilization of analytical UKA in surgical planning and implant design.Methods This study included the robotic analytical UKA performed in our institute between May 2022 and April 2024.The procedures of analytical UKA were reported in detail.The percentage of patients who reached the dynamic joint space balance were calculated,and the curves of dynamic joint space balance were classified according to their patterns.Preoperative and postoperative hip-knee-ankle(HKA)angle,posterior condylar offset ratio(PCOR)and posterior tibial slope(PTS)were compared.Results Eighteen analytical medial UKA cases were included and 9 UKAs(50.0%)reached the dynamic joint space balance.The main types of these curves were U type(44.4%),inverted U type(33.3%)and horizontal type(11.1%).The knee balance solver was used in 13 cases.The curves of the knee balance solver system indicated that before the femoral cutting the gaps at flexion 10°-50°were larger than those at flexion 70°-120° in all cases.After the trial implantation,the knee balance solver curve in four cases(30.8%)changed into linear type while seven cases(53.8%)showed that after 70° the gaps would increase when the knees were at a higher knee flexion angle.Postoperative HKA were improved when compared with preoperative HKA(178.67°±3.09° vs 173.00°±2.88°;P<0.001).There was no significant difference between the preoperative and postoperative PCOR(0.51±0.05 vs 0.52±0.03,P=0.518),while the mean postoperative PTS were significantly smaller than the mean preoperative PTS(7.75°±3.28° vs 10.66°±3.03°,P=0.001).Conclusions Analytical medial unicompartmental knee arthroplasty can guide the surgical planning through the real-time quantitative analysis of multiple parameters.The postoperative radiographic parameters are satisfactory.Some patients can achieve dynamic gap balance during the whole process of flexion and extension.
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