Bizot P, Meunier A, Christel P, Witvoët J
Laboratoire de Recherches Orthopédiques (Pr SEDEL), Faculté de Médecine Lariboisière-Saint-Louis, Université Paris VII.
Rev Chir Orthop Reparatrice Appar Mot. 1995;81(3):211-20.
Passive hyperextension is a rare mechanism of injury of knee ligaments in clinical practice. The lesions are often complex and no consensus exists about their sequence. Our purpose was to study the mechanical behavior and the anatomical lesions of the knee following passive hyperextension until rupture.
12 pairs of fresh human cadaveric knees were tested after resection of soft tissue except for the ligaments and the Popliteus muscle. Some of them had specific ligaments sections (PCL or posterior capsule). We used a "four point bending" model at a constant rate (V = 3 10E-4 m/s) and measured failure torque and bending stiffness of the knee. Results were expressed as percent of the response of the normal contra lateral knee.
A wide range of absolute data was noted and correlated to the age and bone quality. Bony avulsion was constant. The posterior capsule was the first structure injured at an average of 23 degrees of recurvatum, followed by the posterolateral ligament. The PCL was the ultimate structure to fail at its femoral attachment, preceding complete dislocation of the knee. No ruptures of the ACL and medial collateral ligament were noted. After section of the posterior capsule, the stiffness of the knee decreased 40 to 80 percent compared to the normal opposite knee, whereas the isolated section of the PCL had no significant effect.
The method used in this study appears reliable. "The four point bending" is a reproducible model and the use of paired specimens allows a quantitative approach. The use of elderly specimens at a low strain rate in this experiment remains a questionable point. Passive hyperextension is characterized by automatic external rotation resulting in asymmetrical posterior lesions and tears of the PCL at its femoral attachment. On the contrary, active hyperextension of the knee can produce ACL injury by anterior translation of the tibia under the femur consecutive to Quadriceps femoris contraction.
Our experimental model is an effective and reproducible method to create passive hyperextension of the knee. The first structure to fail is the posterior capsule followed by the posterolateral ligament. The PCL is the ultimate structure to fail and no ACL rupture has been noted before dislocation.
if passive hyperextension mechanism is suspected, isolated posterior capsule lesion may occur and should be repaired. On the contrary, PCL tear should never be isolated and always associated with peripheral ligament injuries.
被动膝关节过伸在临床实践中是一种罕见的膝关节韧带损伤机制。损伤往往较为复杂，对于其损伤顺序尚无共识。我们的目的是研究被动膝关节过伸直至断裂后膝关节的力学行为和解剖损伤。
切除除韧带和腘肌外的软组织后，对12对新鲜人尸体膝关节进行测试。其中一些膝关节进行了特定韧带的切断（后交叉韧带或后关节囊）。我们采用“四点弯曲”模型，以恒定速率（V = 3×10⁻⁴ m/s）进行测试，并测量膝关节的破坏扭矩和弯曲刚度。结果以对侧正常膝关节反应的百分比表示。
记录到广泛的绝对数据，并与年龄和骨质相关。骨撕脱是恒定的。后关节囊是在平均23度反曲时首先受损的结构，其次是后外侧韧带。后交叉韧带是在其股骨附着处最终失效的结构，先于膝关节完全脱位。未观察到前交叉韧带和内侧副韧带断裂。切断后关节囊后，膝关节的刚度比正常对侧膝关节降低了40%至80%，而单独切断后交叉韧带则无显著影响。
本研究中使用的方法似乎可靠。“四点弯曲”是一个可重复的模型，使用配对标本允许进行定量研究。在本实验中以低应变率使用老年标本仍是一个有问题的点。被动膝关节过伸的特征是自动外旋，导致不对称的后部损伤和后交叉韧带在其股骨附着处撕裂。相反，膝关节主动过伸可因股四头肌收缩导致胫骨在股骨下向前移位而产生前交叉韧带损伤。
我们的实验模型是一种有效且可重复的产生被动膝关节过伸的方法。首先失效的结构是后关节囊，其次是后外侧韧带。后交叉韧带是最终失效的结构，在脱位前未观察到前交叉韧带断裂。
如果怀疑存在被动膝关节过伸机制，可能会发生孤立的后关节囊损伤，应进行修复。相反，后交叉韧带撕裂绝不应孤立存在，总是与周围韧带损伤相关。
