Arnold Markus P, Lie Denny T T, Verdonschot Nico, de Graaf Ruurd, Amis Andrew A, van Kampen Albert
Department of Orthopaedic Surgery, University Hospital, Hanzeplein 1, NL- 9700 RB Groningen, the Netherlands.
Am J Sports Med. 2005 Apr;33(4):536-42. doi: 10.1177/0363546504269938. Epub 2005 Feb 16.
There is sometimes a return of excess knee laxity after anterior cruciate ligament reconstruction. One of the contributing factors might be a loss in graft tension. It is unknown whether the tension imposed on an anterior cruciate ligament graft degrades with time and, if so, the effect of that loss of tension on knee laxity.
The pretension in the anterior cruciate ligament graft reduces significantly within the first 500 motion cycles, and this decrease in graft tension causes an increase in knee laxity.
Controlled laboratory study.
This study measured the remains of bone-patellar tendon-bone graft pretension after cyclical flexion-extension and the effect of any tension loss on knee laxity, using 8 cadaveric knees. A tension transducer was inserted into the graft and calibrated in situ. The reconstruction tension was 40 N at 20 degrees of flexion. In test 1, the graft tension was measured under cyclical flexion-extension in a motorized rig up to 1500 cycles. Test 2, with a new graft, also included anteroposterior and internal-external rotational knee laxity measurements at 0, 500, and 1500 cycles.
The graft tension at 0 degrees of flexion dropped from 208 N, by 25% after 50 cycles, 41% by 500, and 46% by 1500 cycles. Anterior laxity increased from +1.4 to +2.8 mm by 500 cycles, and performing these laxity tests also caused significant tension losses.
These results provide one possible explanation for early slackening of anterior cruciate ligament reconstructions.
前交叉韧带重建术后有时会出现膝关节松弛度增加的情况。其中一个促成因素可能是移植物张力的丧失。目前尚不清楚施加在前交叉韧带移植物上的张力是否会随时间而降低，如果会降低，那么这种张力丧失对膝关节松弛度会有怎样的影响。
在前交叉韧带移植物的前500个运动周期内，其预张力会显著降低，而这种移植物张力的降低会导致膝关节松弛度增加。
对照实验室研究。
本研究使用8具尸体膝关节，测量了周期性屈伸运动后髌腱骨移植物的预张力残留情况以及任何张力丧失对膝关节松弛度的影响。将一个张力传感器插入移植物中并在原位进行校准。在20度屈曲时重建张力为40牛。在测试1中，在电动装置上对移植物进行周期性屈伸运动，直至1500个周期，并测量移植物张力。测试2使用新的移植物，还包括在0、500和1500个周期时测量膝关节前后向和内外旋转方向的松弛度。
在0度屈曲时，移植物张力从208牛开始下降，50个周期后下降25%，500个周期后下降41%，1500个周期后下降46%。到500个周期时，前向松弛度从+1.4毫米增加到+2.8毫米，并且进行这些松弛度测试也会导致显著的张力丧失。
这些结果为前交叉韧带重建早期松弛提供了一种可能的解释。
