增加胫骨平台后倾角度、后交叉韧带部分松解对全膝关节置换术后膝关节运动影响的实验研究

目的通过增加胫骨平台后倾角度或后交叉韧带（PCL）部分松解对全膝关节置换术（TKA）中屈曲间隙过紧进行处理,分析这两种方法对TKA术后膝关节运动学的影响。方法测量6例新鲜尸体膝关节标本在完整状态下、正常TKA、屈曲间隙过紧、增加胫骨平台后倾角以及PCL部分松解TKA术后膝关节屈曲0°、30°、60°、90°、120°时的前后松弛度、内外翻松弛度、旋转松弛度及最大屈曲度。结果屈曲过紧TKA与正常TKA相比,在屈曲30°、60°、90°和120°时前后松弛度、内外翻松弛度及旋转松弛度均显著较小（P〈0．05）。与屈曲过紧TKA相比,增加胫骨后倾角后,在屈曲30°、60°、90°和120°时前后松弛度、内外翻松弛度和旋转松弛度均明显增大（P〈0．05）。PCL部分松解与屈曲过紧TKA相比,在屈曲30°、60°、90°和120°时前后松弛度明显增加（P〈0．05）;旋转松弛度在屈曲30°、60°、90°时明显增加（P〈0．05）。与PCL部分松解相比,增加胫骨后倾角的内外翻松弛度在屈曲30°、60°、90°时明显较大（P〈0．05）;旋转松弛度在屈曲0°、30°、60°和90°时明显较大（P〈0．05）。屈曲过紧TKA的最大屈曲度（120．4°）与正常TKA（130．3°）及增加胫骨后倾角（131．1°）相比明显较小（P〈0．05）。增加后倾角与PCL部分松解（124．0°）相比,最大屈曲度较大,但差异无统计学意义（P=0．0816）。结论屈曲间隙过紧TKA术后膝关节的前后松弛度、内外翻松弛度、旋转松弛度和最大屈曲度均减小;增加胫骨平台后倾角后,前后松弛度、内外翻松弛度、旋转松弛度和最大屈曲度均明显增大;PCL部分松解仅能明显增大前后松弛度。因此对于TKA术中屈曲紧张的膝关节,增加胫骨平台后倾角比PCL部分松解能更好地改善膝关节的运动学。

Effect of increased posterior tibial slope or partial posterior cruciate ligament release on knee kinematics of total knee arthroplasty

OBJECTIVE: To compare the effects of increased posterior tibial slope or partial posterior cruciate ligament (PCL) release on knee kinematics of total knee arthroplasty (TKA). METHODS: Anteroposterior laxity, rotational laxity, varus and valgus laxity and maximum flexion angle were evaluated in 6 normal cadaver knees and the knees after TKA at flexion 0 degrees , 30 degrees , 60 degrees , 90 degrees and 120 degrees . Then the femoral prosthesis was shifted 5 mm posteriorly to simulate the tightly implanted knee. The same tests were performed on the tightly implanted knees. After that, the posterior tibial slope was increased 4 degrees or the PCL was partially released, and the same tests were made as in the normal knees respectively. Statistical analysis of the results was made using student's t test. RESULTS: Anteroposterior laxity, rotational laxity and varus and valgus laxity of the tightly implanted knees at flexion 30 degrees , 60 degrees , 90 degrees and 120 degrees were significantly less than those of the normal TKA knees (P < 0.05). Compared with the tightly implanted knees, anteroposterior laxity, rotational laxity and varus and valgus laxity at flexion 30 degrees , 60 degrees , 90 degrees and 120 degrees significantly improved after increased 4 degrees posterior tibial slope (P < 0.05); in the partial PCL released group, anteroposterior laxity at flexion 30 degrees , 60 degrees , 90 degrees and 120 degrees was significantly improved (P < 0.05), varus and valgus laxity was significantly improved only at flexion 90 degrees (P < 0.05), and rotational laxity was significantly improved at flexion 30 degrees , 60 degrees and 90 degrees (P < 0.05). Compared with PCL released group, varus and valgus laxity at flexion 30 degrees , 60 degrees and 90 degrees and rotational laxity at flexion 0 degrees , 30 degrees , 60 degrees and 90 degrees were significantly improved in the group of increased 4 degrees posterior tibial slope (P < 0.05). Maximum flexion angle of the tightly implanted knee (120.4 degrees ) was less than that of the normal TKA knees (130.3 degrees , P < 0.05) and that of increased 4 degrees posterior tibial slope group (131.1 degrees , P < 0.05). There was no significant difference at the maximum flexion angle between the increased 4 degrees posterior tibial slope group and the PCL released group (131.1 degrees vs 124.0 degrees , P = 0.0816). CONCLUSIONS: Anteroposterior laxity, varus and valgus laxity, rotational laxity and maximum flexion angle of the tightly implanted knees are less than those of the normal TKA knees. After increased 4 degrees posterior tibial slope, these indexes are improved significantly. Partial PCL released can significantly improve the anteroposterior laxity and had less effect on the varus and valgus laxity, rotational laxity and maximum flexion angle. So, a knee that is tight in flexion can be more likely to be corrected by increasing posterior tibial slope than by partially releasing PCL.