ABSTRACT
BACKGROUND:Stress shielding in the Achil es tendons induces over-expression of tumor necrosis factor-α. The degree of tendon contracture remains unclear after the intervention with tumor necrosis factor inhibitor. OBJECTIVE:To investigate the effects of tumor necrosis factor-αon tendon contracture and the preventive effects of tumor necrosis factor inhibitor (etanercept) on tendon contracture by observing the morphological changes of the stress-shielded Achil es tendons after the intervention with etanercept. METHODS:A total of 20 healthy male Sprague-Dawley rats were randomly divided into experimental and model groups after stress shielding in Achil es tendons of rat left hind limb. Five rats from either group were randomly selected, and their right hind limbs were considered as normal controls. Immediately after model induction, the rats in the experimental group were subjected with 0.6 mg/kg etanercept, and those in the model group were subcutaneously treated with 1 mL phosphate buffered saline. According to half-life of etanercept, the two groups were separately injected three times. At 2 weeks after intervention, the morphological changes of the Achil es tendons were observed using gross examination and transmission electron microscope. RESULTS AND CONCLUSION:On gross examination, the Achil es tendons in the experimental group were significantly smoother and smal er than those of the model groups, but thicker than those of the normal control group. Under a transmission electron microscope, the col agen fibrils of the model group were looser and more disordered than those of the experimental group. The col agen fibrils of the experimental group were similar to those of the normal control group in cross section and longitudinal section. These indicated that tumor necrosis factor-αantagonist can obviously prevent stress shielding-induced tendon contracture at 2 weeks.