Spinal segment range of motion as a function of in vitro test conditions: effects of exposure period, accumulated cycles, angular-deformation rate, and moisture condition.
The purpose of this study was to thoroughly evaluate the relationship of possible mechanical and environmental conditions in the testing of spinal joint segments, including ambient-temperature exposure, accumulated test cycles, angular-deformation rate, and moisture condition on the motion characteristics of joints, with the example of isolated spinal segments.



In one test, controlled loading was applied to six motion segments every 8 hours in each of the primary anatomical directions while moisture was held constant. In a second test, 18 specimens were divided equally into moisture-static, air-exposed, and slowly irrigated groups and loaded to 500 cycles. In a third test, a similar sample was tested over a range of angular-deformation rates (0.6-5.1 degrees/second).



Range of motion (ROM) increased steadily with ambient-temperature exposure time, resulting in a 10% change at about 20 hours but was most stable in the moisture-static group over both accumulated load cycles and loading rate changes.



The most critical factor for functional testing of spinal segments appears to be length of exposure.
Wilke
H J
HJ
Department Unfallchirurgische Forschung und Biomechanik, Universität Ulm, Germany. wilke@sirius.medizin.uni-ulm.de
Jungkunz
B
B
Wenger
K
K
Claes
L E
LE
D000818:Animals; D006813:Humidity; D008159:Lumbar Vertebrae / Q000502:physiology*; D008953:Models, Anatomic; D018583:Pliability; D011597:Psychomotor Performance / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D012756:Sheep; D013116:Spinal Cord / Q000502:physiology; D013314:Stress, Mechanical; D013552:Swine; D013696:Temperature; D013997:Time Factors; D016474:Weight-Bearing / Q000502:physiology