ABSTRACT
Objective To develop a set of loading device that can simulate the spinal movement in vitro so as to carry out the biomechanical experiment on human spine. Methods Based on the principle of bearing, the rotary locking device was designed and fixed on the loading plate, which was rotated to the position for testing and then locked by the bolt before loading. And then, with the auto-loading power provided by the universal testing machine, the pure moment of flexion/extension, left/right bending and left/right axial rotation were applied on the spine specimen to simulate the spinal movement in vivo. Finally, the position of the spine specimen before/after loading was measured by the 3D scanner. With the loading device, the range of motion under these six loading conditions for six fresh (one-year age) porcine cervical spines (C2-C6) was tested, and precision of the loading device as well as error analysis were testified by experiments. Results A set of experimental device for the three-dimensional movement measuring for human spine was developed. Data of neutral zone and range of motion for the porcine cervical spine in six directions were acquired with the total measurement error being less than 3.5％. Conclusions The delicate design of this loading device could simulate the spinal motion in vitro and thus achieve the rapid loading of the human spine. This is an inexpensive, simple and practical device, which can significantly increase the test efficiency and has great application value in loading on the spine in vitro.
ABSTRACT
Objective To identify whether the calf or porcine cervical spine is a suitable substitute specimen for vitro spine study by comparing the biomechanical characteristics of porcin, calf and human cervical segments. Method Twelve fresh (age: 1 year; average weight: 60-80 kg) porcine cervical spines (C0-T1) and twelve fresh (age: 1 week; average weight： 40-50 kg) calf cervical spines (C0 T1) were taken. The twelve specimens were divided into two groups. One group of six was divided into C2-C3, C4-C5, C6-C7; the other group was divided into C3-C4, C5-C6. The muscle and soft tissue of each functional segment (C2-C3, C3-C4, C4-C5, C5-C6, C6-C7) were removed, preserving the full ligament, and then each functional segment was tested respectively. The flexion/extension, axial left/right rotation, and right/left lateral bending were applied continuously on the range of motion(ROM) and neutral zone(NZ). The findings in the study were compared with the published data of human cervical spine. Results In rotating and extension/flexion of NZ, the calf and human cervical spines were relatively similar, but they were far greater than that of the porcine cervical spine. In the lateral bending, the NZ of porcine C2-C3 was 69.7% of human, the NZ of porcine C6-C7 was 60.4% of human, and other segments were far smaller than human; the calf cervical spines were different from human, except the C2-C3. In bending and extension flexion of ROM, the porcine and human cervical spines were very similar. But they were far less than the calf, approximately 50% of calf; in the rotation, C2-C3 of porcin was about 69% of human, and other segments were less than the human. The calf cervical spine was much larger than human, and the smallest gap was in C4-C5 of 3.5 °. Conclusions The C2-C3 and C6-C7 of porcin can replace the human cervical spine in nearly all biomechanical experiments on spines. The ROM of calf is bigger than human cervical, but the C2-C3 and C3-C4 of calf are similar to human in biomechanics.