Rest Cannot Always Recover the Dynamic Properties of Fatigue-Loaded Intervertebral Disc
Resource
Spine 33 (17): 1863-1869
Journal
Spine
Journal Volume
33
Journal Issue
17
Pages
1863-1869
Date Issued
2008
Date
2008
Author(s)
Wang, Jaw-Lin
Wu, Tai-Kuan
Lin, Tzu-Cheng
Cheng, Chih-Hsiuch
Huang, Shyh-Chin
Abstract
Study Design. An in vitro biomechanical study using adolescent porcine discs. Objective. To find the effect of fatigue loading and rest on the dynamic properties of healthy intervertebral disc. Summary of Background Data. The fatigue loading is a risk factor for low back pain. The disc dynamic properties describe the shock attenuation capability of disc. Knowledge of effect of fatigue loading and rest on the disc dynamic properties can be beneficial for the study of fatigue loading induced spinal disorder. Methods. Specimens were divided into short-term (0.5 hours at 5 Hz, n = 9) and long-term (2 hours at 5 Hz, n = 9) fatigue loading groups. The specimen was applied with fatigue loading, followed by a 12-hours rest, and then applied with the second fatigue loading again. The impulse loading was applied at 0, 10, 20, and 30 minutes during short-term group and at 0, 0.5, 1, and 2 hours during long-term group using a drop-tower apparatus. The stiffness, damping coefficient, and ratio were calculated using impulse loading information. Dynamic properties between first and second fatigue loading were compared. Results. The stiffness increased, but the damping coefficient and ratio decreased with fatigue loadings. A 12-hours rest can fully restore the dynamic properties of fatigue loaded disc to original status. However, the degradation of dynamic properties during the subsequent fatigue loading was faster than the previous fatigue loading if the disc experienced a long-term fatigue loading. Conclusion. A 12-hours rest can largely restore disc dynamic properties during fatigue loading; hence fully recover disc dynamic properties. A long-term fatigue loading squeezes the disc fluid and injures the disc integrity. The 12-hours rest can recover the fluid loss but not the injury of disc. Hence, the disc degradation during the second fatigue loading was faster than the first fatigue loading. © 2008 Lippincott Williams & Wilkins.
Subjects
Damping coefficient; Damping ratio; Disc; Fatigue; Impulse loading; Stiffness
Other Subjects
article; biomechanics; calculation; dynamics; fatigue; intervertebral disk; lumbar disk; priority journal; rest; rigidity; animal; comparative study; compressive strength; lumbar vertebra; muscle fatigue; physiology; swine; weight bearing; Animals; Biomechanics; Compressive Strength; Intervertebral Disk; Lumbar Vertebrae; Muscle Fatigue; Rest; Swine; Weight-Bearing
Type
journal article
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