关键词: 数字影像, 术前规划, 膝关节, 内侧间室, 骨关节炎, 单髁置换, LINK, 固定平台

Abstract: BACKGROUND: Unicompartmental knee arthroplasty is the preferred treatment for end-stage medial compartment osteoarthritis. Numerous factors influence the placement of LINK fixed-bearing prosthesis. Does angle deviation have an effect on postoperative clinical efficacy? Can preoperative digital image planning reduce the deviation?
OBJECTIVE: Unicompartmental knee arthroplasty with LINK fixed-bearing prosthesis assisted by digital imaging system is used to treat medial compartment osteoarthritis patients. This thesis is to investigate the clinical significance of preoperative planning for prosthesis placement, and to clarify the relationship between deviation angle and clinical efficacy.
METHODS: From October 2017 to January 2020, 28 patients (32 knees) with medial compartment osteoarthritis who underwent LINK fixed-bearing unicompartmental knee arthroplasty in Department of Orthopedics of 2Wuxi People’s Hospital were analyzed retrospectively. They were divided into planning group (n=17; 18 knees) and conventional group (n=11; 14 knees) on the basis of whether the preoperative imaging planning was carried out. The incidence of patellar impact and bounce was reviewed. The varus or valgus angle of femoral prosthesis (A angle), the flexion and extension angle of femoral prosthesis (B angle), the varus or valgus angle of tibial prosthesis (E angle), the posterior slope angle of tibial prosthesis (F angle) and the line of prosthetic loosening were measured on the reexamined X-ray. The angle variation rate, loosening rate and prosthesis deviation score were calculated and recorded in succession. The range of motion, the score of hospital for special surgery and the complications of knees were also followed up.
RESULTS AND CONCLUSION: (1) The 32 knees were followed up for 6-33 months. (2) No indication of patellar impact or bounce occurred in both groups. (3) In planning group, A angle was measured at [3.90 (-0.66, 6.78)]°, with B angle [4.33 (2.01, 8.05)]°, E angle [-3.28 (-7.61, -0.13)]° and F angle [0.30 (-2.74, 2.50)]°. While in conventional group, A angle was measured at [2.75 (-2.73, 8.29)]°, with B angle [6.45 (1.55, 18.30)]°, E angle [-3.05 (-6.73, 0.54)]° and F angle [3.30 (-2.35, 6.71)]°. (4) The deviation scores of B angle, femoral prosthesis and total prosthesis in planning group were significantly lower than those in conventional group (P < 0.05). There came out to be no obvious differences in tibial prosthesis scores between planning group and conventional group (P > 0.05). (5) In contrast to preoperative period, last follow-up demonstrated apparent improvements in both range of motion and hospital for special surgery scores of two groups (P < 0.05). However, no specific evidence seemed to exist to certify the difference in range of motion and hospital for special surgery scores between two groups at the latest follow up (P > 0.05). (6) A significant negative correlation was verified between A angle deviation score and hospital for special surgery score (r=-0.533, P=0.002). (7) No complications occurred in planning group, while one case in conventional group developed prosthesis loosening and underwent revision. (8) The results confirmed that digital imaging system-assisted preoperative planning can improve the accuracy of prosthesis placement of LINK fixed bearing and reduce the angle deviation. The deviation of A angle from femoral prosthesis has great impacts on postoperative knee functions. 

Key words: digital imaging, preoperative planning, knee joint, medial compartment, osteoarthritis, unicompartmental knee arthroplasty, LINK, fixed-bearing