跟骨后关节面骨折后接触面积改变的实验研究

THE CHANGES OF CONTACT AREA OF THE SUBTALAR JOINT AFTER CALCANEUS FRACTURE

目的研究载荷条件下跟骨距下后关节面骨折后,接触面积的改变对后距下关节的影响。方法取6具包括完整足和胫腓骨远端15-20 cm的新鲜标本。剔除皮肤、肌肉和跟腱,保留除外距下关节后方的关节囊部分,保持韧带和关节囊的完整。将压敏片插入距下关节的后关节面,中立位状态下分别在500N载荷下,对6具标本的距下关节进行加载,完成完整足的测试。然后模拟原始骨折线用微型摆动锯将跟骨后关节面分为前内和后外两块,按解剖复位、后外侧骨折块向跖侧移位2、51、0 mm等条件重复上述实验,记录后距下关节接触面积的改变。结果完整距下后关节面平均接触面积为（275.67±46.02）mm^2。跟骨后外侧骨折块向跖侧移位2 mm时,后关节面平均接触面积为（167.67±25.09）mm^2,较完整跟骨接触面积显著下降（P〈0.01）。结论跟骨距下关节后关节面骨折移位≥2 mm其接触面积显著下降,应手术复位。

Objective To observe the changes of contact area of the posterior subtalar joint after calcaneus fracture in the one load condition, to study influence with the posterior subtalar joint. Methods Six fresh speciments consisting of feet and lower legs were used. A specimen, including an intact foot and 15-20 cm of the distal tibia and fibula prepared by removing the skin, musclt and tendons down to the level of the hindfoot. The ligaments and joint capsules were keep intact with the exception of the posterior aspect of the posterior facet. The pressure sensitive film was inserted into the posterior facets of the talocalcaneal articulation, and 500-N load was applied on the specimen in the neutral position. After testing of the intact foot, the calcaneus was splited into anterointernal and posterolateral compoments using microoscillating saw and the primary fracture line of calcaneus was simulated. The test was repeated after the posterolateral fragment was anatomically reduced and displaced 2 mm, 5 mm and 10 mm respectively in a planter direction. The changes of contact area of the posterior subtalar joint was record. Results The average pressure area of the intact posterior facet was （275.67±46.02） mm^2 The average pressure area decreased to （167.67 ± 25.09）mm^2 when the posterolateral compoment was displaced to plantar in 2mm,it was significantly lower （ P 〈0.01） than that of the intact calcaneus. Conclusion A calcaneus fracture with 2 mm of fracture component displacement in the posterior facet of subtalar joint should be reduced by surgery.