2019 年 38 巻 2 号 p. 107-113
Objective: In unicompartmental knee arthroplasty (UKA), it has been reported that preoperative coronal tibiofemoral subluxation (CTFS) can be corrected partly after surgery. However, large CTFS after UKA may be a risk factor for tibial edge-loading. The purpose of this study was to clarify whether the residual CTFS after medial UKA could be improved the during postoperative period and to identify risk factors in order to make the postoperative CTFS large.
Methods: The pre- and postoperative two-week, one-, two-, and three-year radiographic data of all UKAs (56 knees in 47 patients, performed for medial knee osteoarthritis between January 2012 and December 2013) were analyzed using standardized knee radiographs. Radiographs were obtained as standing anteroposterior films and under preoperative stress. The amount of the CTFS was measured by a method described by Nam D, et al.
Results: The CTFS was significantly corrected from 4.9 mm±1.7 in preoperative standing radiographs to 3.7 mm±1.4 in valgus stress radiographs (P＝0.001) and to 3.8 mm±1.3 in postoperative 2-week radiographs (P＝0.002). The mean CTFS in postoperative two-week, one-, two-, and three-year radiographs were 3.9 mm±1.2, 3.6 mm±1.4, 3.5 mm±1.5, and 3.4 mm±1.4, respectively. Significant correlations were noted between the CTFS in preoperative standing radiographs and the 2-week postoperative CTFS (R＝0.62, P<0.001), the preoperative CTFS under stress imaging and the 2-week postoperative CTFS (R＝0.55, P<0.001), and between the 2-week postoperative CTFS and the three-year postoperative CTFS (R＝0.83, P<0.001). There was a significant relationship between the 2-week postoperative CTFS and pre- and postoperative tibial medial slope (TMS) (R＝0.52, P<0.001 and R＝0.32, P＝0.01, respectively).
Conclusion: The results of this study indicates that the residual CTFS after medial UKA does not change during the postoperative period. Further, the CTFS on preoperative standing and on stress radiographs are useful to predict the postoperative residual CTFS. Patients with a large burden of CTFS on preoperative radiographs including stress imaging and preoperative TMS angle may be excluded from the indication of the medial UKA to avoid edge loading after medial UKA.
