송아지와 사람의 요추 모델의 생역학적 비교 = Biomechanical Comparison of Calf and Human Lumbar Spine Models

다국어 초록 (Multilingual Abstract)

Background and Objectives: Calf spines are commonly used in biomechanical research as a substitute for human cadaveric spines. Despite widespread use, the validity of this model has not been thoroughly investigated. The purpose of this study was to perform biomechanical flexibility tests using identical methods and instrumentation on calf and cadaveric lumbar spines to determine whether significant differences exist between the results from the two models. Materials and Methods: Five fresh calf spines and five cadaver lumbar spines (L2-L5) were used for flexibility testing. The L2 and L5 vertebrae were used to attach the loading and base frames, respectively. Three reflective markers were attached to L3 and L4. Specimens underwent nondestructive biomechanical testing using the VICON 3-D motion analysis system. Maximum moments of 6.4 Nm were achieved in five increments of 1.6 Nm. The rotations of L3 with respect to L4 were measured to determine the stability of the specimens in five cases : 1) intact ; 2) partial discectomy, including partial laminectomy and partial facetomy ; 3) partial discectomy with ISOLA pedicle screw instrumentation ; 4) total discectorny with instrumentation and 5) instrumentation with inter body graft. Rotational angles were normalized to the intact case to determine the overall stabilizing effects. Data were analyzed using ANoVA to determine if significant differences existed. Results: In both models an increase in motion was observed after the partial discectorny, instrumentation reduced motion beyond the intact, and the total discectomy increased motion in all cases. Placement of the inter body graft decreased motion in axial rotation, flexion, and extension, but increased motion in lateral bending. A two-way ANoVA showed no significant differences between the two models during flexion and extension (p)O. 05) however, differences were noted during axial rotation and lateral bending (p<0.05). In all loading cases there were differences between the various testing cases (p<.05). Conclusion: This study demonstrated that calf lumbar spines can serve as a substitute for human cadaveric spines in biomechanical testing. Motion trends were similar for the two models in flexion and extension ; however, significant differences were found in axial rotation and lateral bending. These results suggest that the calf lumber spine can be a good model for in vitro biomechanical evalution of spinal instrumentation. The extrapolation of calf spine data to the in vivo case, especially during axial ratation and lateral bending, should carefully consider the variations between the two models.