van de Pol Gerrit Jan, Arnold Markus P, Verdonschot Nico, van Kampen Albert
Department of Orthopaedics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Am J Sports Med. 2009 Mar;37(3):481-7. doi: 10.1177/0363546508326715. Epub 2008 Dec 16.
Varus thrust of the knee is a dynamic increase of an often preexisting varus angle and it is suspected to be a major reason for failure of anterior cruciate ligament reconstructions. However, it is not known if a direct relationship exists between varus thrust and forces in the anterior cruciate ligament.
Forces in the anterior cruciate ligament increase with increasing varus alignment, and consequently an anterior cruciate ligament deficiency in a varus-aligned leg leads to more lateral tibiofemoral joint opening.
Controlled laboratory study.
Six human cadaver legs were axially loaded with 3 different weightbearing lines--a neutral weightbearing line, a weightbearing line that passes through the middle of the medial tibial plateau (50% varus), and a line passing the edge of the medial tibial plateau (100% varus)--that were used to create a varus moment. The resulting lateral tibiofemoral joint opening and corresponding anterior cruciate ligament tension were measured. The tests were repeated with and without the anterior cruciate ligament in place.
In the neutral aligned legs, there was no apparent lateral joint opening, and no anterior cruciate ligament tension change was noted. The lateral joint opening increased when the weightbearing line increased from 0% to 50% to 100%. The lateral joint opening was significantly higher in 10 degrees of knee flexion compared with knee extension. In the 100% varus weightbearing line, the anterior cruciate ligament tension was significantly higher (53.9 N) compared with neutral (31 N) or the 50% weightbearing line (37.9 N). A thrust could only be observed in the 100% weightbearing line tests. In the absence of an anterior cruciate ligament, there was more lateral joint opening, although this was only significant in the 100% weightbearing line.
There is a direct relationship between varus alignment and anterior cruciate ligament tension. In the absence of an anterior cruciate ligament, the amount of lateral opening tends to increase. With increasing lateral opening, a thrust can sometimes be experimentally observed.
A varus alignment in an anterior cruciate ligament-deficient knee does not necessarily lead to a varus thrust and therefore does not always need operative varus alignment correction. However, in an unstable anterior cruciate ligament-deficient knee with a varus thrust, it might be safer to perform a high valgus tibial osteotomy to minimize the risk of an anterior cruciate ligament reconstruction failure.
膝内翻推力是常已存在的内翻角度的动态增加，被怀疑是前交叉韧带重建失败的主要原因。然而，尚不清楚膝内翻推力与前交叉韧带受力之间是否存在直接关系。
前交叉韧带的受力随着内翻对线增加而增加，因此内翻对线的腿中前交叉韧带缺损会导致更多的胫股关节外侧开口。
对照实验室研究。
对6条人尸体下肢施加3种不同的负重线——中立负重线、穿过胫骨内侧平台中部的负重线（50%内翻）和穿过胫骨内侧平台边缘的线（100%内翻）——以产生内翻力矩。测量由此产生的胫股关节外侧开口及相应的前交叉韧带张力。在前交叉韧带完整和缺失的情况下重复进行测试。
在中立对线的下肢中，未观察到明显的外侧关节开口，前交叉韧带张力也未发生变化。当负重线从0%增加到50%再到100%时，外侧关节开口增加。与膝关节伸直相比，膝关节屈曲10度时外侧关节开口明显更大。在100%内翻负重线时，前交叉韧带张力（53.9牛）明显高于中立（31牛）或50%负重线（37.9牛）。仅在100%负重线测试中观察到推力。在前交叉韧带缺失时，外侧关节开口更大，尽管仅在100%负重线时具有统计学意义。
内翻对线与前交叉韧带张力之间存在直接关系。在前交叉韧带缺失时，外侧开口量往往会增加。随着外侧开口增加，有时可通过实验观察到推力。
前交叉韧带缺损膝关节的内翻对线不一定会导致膝内翻推力，因此不一定总是需要手术矫正内翻对线。然而，在伴有膝内翻推力的不稳定前交叉韧带缺损膝关节中，进行高外翻胫骨截骨术以降低前交叉韧带重建失败的风险可能更安全。
