The Effects Of Immobilization On The Biological Characteristics Of Posterior Cruciate Ligament Of Rabbits

Objective: This study supposed to immobilize the knee of therabbits, then investigate the change of the initial length, cross section area,maximum load, maximum stretched length, maximum stress, maximumstrain, modulus of elasticity, stress relaxation, creep deformation,histological change under microscope, used the statistic analysis toinvestigate the effects of immobilization on the biological characteristicsof posterior cruciate ligament of rabbitsMethods: 26 rabbits with no significant difference existed betweenthe bodyweight. The range of motion of the both knee were: flexionbetween 120°-150°,extention 0°,hyperextention5°-10°, posterior draw test(-). Rabbits with less range of motion, injury of the knee, swelling of theknee, posterior draw test (+) (posteior motion of the tibia more than0.5cm) were excluded. The rabbits were randomized to receive kneeimmobilization for 6 weeks (groupⅠ, n=6), 8 weeks (groupⅡ, n=8),immobilized for 6 weeks then remmobilized for 2 weeks (groupⅢ, n=6),control group ((groupⅣ, n=6). "U" type plastic immobilization frominguinal groove to toe tip, with knee extention 180°and ankle dorslflexion 60°were used. For groupⅢ, passive remmobilization for first 3days were used. After enough immobilization time the rabbits weresacrificed withair embolism, knee joint of both sides were gained, all theknee structure except PCL were disconnected, initial length, cross sectionarea, maximum load, maximum stretched length, maximum stress,maximum strain, modulus of elasticity, stress relaxation, creepdeformation of the PCL were measured. Histological change undermicroscope were observed. Statistics treatment: The measurement datawas expressed as "(?)±s", and using Independent-samples T test programof SPSS 13.0 software to analyze it.when the value of "p" is lower than 0.05,it has significance.Results: The body weight had no significant difference in all groups(P＞0.05). The initial length, cross section area in all immobilizationgroups had no significant difference. The maximum load, maximumstretched length, maximum stress, maximum strain, modulus of elasticity,stress relaxation, creep deformation decreased significantly compared toboth contralateral and control group. The HE stained preparation of theimmobilization groups showed derangement of the collagen fibers.Conclusion: Long time immobilization of the knee of the rabbitscan change the biological characteristics of posterior cruciate ligament,and can not been restored by short time remmobilization. These resultsindicate that long time immobilization of the knee of the rabbits maycause influation of the function of the PCL.