RESUMO
BACKGROUND: Bone joint immobilization is often used to prevent the injured tissue from secondary injury.OBJECTIVE: To investigate the effects of knee immobilization on biomechanical changes in rabbit patellar tendon and ultrastructure morphology. METHODS: Twenty adult rabbits were assigned into two groups. The left hindlimbs of rabbits in the immobilized group (n = 10) were immobilized by plaster of paris and two adjustable aluminium splints for 6 weeks, while those left hindlimbs in the control group (n = 10) served as controls. Rabbit knees were immobilized in extension and the ankle was immobilized at 90°flexion for 6 weeks. Then the patellar tendon-bone complex was harvested to observe the biomechanical properties and ultrastructure changes of patellar tendon. RESULTS AND CONCLUSION: After 6-week immobilization, the tensile strength and tangent modulus of patellar tendon-bone complex were decreased to 64.44% and 53.08% of the control values (P < 0.01). However, there was no significant difference in the elongation at failure and the maximum load between the immobilized and control groups. The curves of stress and strain of patellar tendon based on the average material constant were greatly different. The cross-sectional area of patellar tendon was significantly larger in the immobilized group than in the control group (P < 0.01). Smaller collagen fibrils took the predominance in the immobilized group. These results showed that immobilization of knee joint could result in biomechanical changes of patellar tendon and produce influence on patellar tendon.