Journal of Capital Medical University ›› 2024, Vol. 45 ›› Issue (5): 773-782.doi: 10.3969/j.issn.1006-7795.2024.05.005

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Analytical medial unicondylar knee arthroplasty: surgical procedure and early clinical practice 

Deng Wang1,2, Yang Dejin1,2, Zhao Yongqiang3, Lu Jiahao3, Shi Hongwei3, Tang Hao1,2, Wang Zhaolun1,2, Zhang Yunfeng1,2, Shao Hongyi1,2, Zhou Yixin1,2*   

  1. 1.Department of Orthopedic Surgery, Beijing Jishuitan Hospital, Capital Medical University, Beijing 100035, China; 2. The Fourth Clinical College of Peking University, Beijing 100035, China; 3. TianJi Laboratory, Beijing Tinavi Medical Technology Co, Beijing 100096, China
  • Received:2024-07-02 Online:2024-10-21 Published:2024-10-18
  • Supported by:
    This study was supported by National Key R&D Program of China (2023YFC2411000).

Abstract: 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.

Key words: unicompartmental knee arthroplasty, analytical surgery, robot-assisted surgery, gap balancing

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