The Effect of Spinal Implant Rigidity on Vertebral Bone Density A Canine Mode

McAfee, Paul C.; Farey, Ian D.; Sutterlin, Chete E.; Gurr, Kevin R.; Warden, Karen E.; Cunningham, Bryan W.

doi:10.1097/00007632-199106001-00003

Cited by 152 publications

(60 citation statements)

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“…Aside from calf spines, those of pigs [2,3,21,28,30], goats [5, 38,64], sheep [1,27,46,51], and canines [8,22,24,25,48,52,63,66] have been used for biomechanical experiments. Calf spines are the most widely used specimens as they appear to approximate most closely the properties of the human spine [7].…”

Section: Introductionmentioning

confidence: 99%

Load-displacement properties of the thoracolumbar calf spine: Experimental results and comparison to known human data

et al. 1997

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The availability of human cadaveric spine specimens for in vitro tests is limited and the risk of infection is now of vital concern. As an alternative or supplement, calf spines have been used as models for human spines, in particular to evaluate spinal implants. However, neither qualitative nor quantitative biomechanical data on calf spines are available for comparison with data on human specimens. The purpose of this study was to determine the fundamental biomechanical properties of calf spines and to compare them with existing data from human specimens. Range of motion, neutral zone, and stiffness properties of thoracolumbar calf spines (T6-L6) were determined under pure moment loading in flexion and extension, axial left/right rotation and right/left lateral bending. Biomechanical similarities were observed between the calf and reported human data, most notably in axial rotation and lateral bending. Range of motion in the lumbar spine in flexion and extension was somewhat less in the calf than that typically reported for the human, though still within the range. These results suggest that the calf spine can be considered on a limited basis as a model for the human spine in certain in vitro tests.

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Section: Introductionmentioning

confidence: 99%

Load-displacement properties of the thoracolumbar calf spine: Experimental results and comparison to known human data

et al. 1997

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“…B The screw allows adjustment of the longitudinal element within a 30 ° range with a low-profile single locking nut, thus facilitating full three-dimensional adaptation of the instrumentation to the physiological shape of the spine. C The two types of longitudinal element are depicted: cable (semirigid) and rod (rigid) ity and decreased bone formation rate in the vertebral body after posterolateral fusion [5,22,23].…”

Section: Figmentioning

confidence: 99%

In vitro testing of a new transpedicular stabilization technique

et al. 1997

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The rigidity of a pedicle screw implant is a critical biomechanical variable in lumbar spinal fusions. Sufficient rigidity is required for integration of bone grafts and to promote healing. Osteopenia, stress shielding, and compensatory hypermobility have been described as consequences of excessive rigidity. Little is known about the biomechanical characteristics of "semirigid" compared to "rigid" implants. A new implant, whose rigidity can be varied by selection of different implant components, was tested in vitro under well-defined loading conditions. The three-dimensional load-displacement behavior of all lumbar vertebrae involved in or adjacent to the two-level fusion was evaluated for two fusion modifications: bilateral rigid and bilateral semirigid. Cyclic fatigue loading was subsequently carried out under realistic conditions and motion testing repeated. The rigid device reduced the motion of the L3-4 transfixed segment in the primary movement planes by 87.3% with respect to the intact spine value in flexion/extension (FE), 86.3% in lateral bending (LB), and 76.8% in axial rotation (AR). The semirigid device achieved a reduction in motion of 79.6% (FE), 82.7% (LB), and 51.7% (AR). The semirigid implant was particularly easy to insert, because no bending of rods or plates was necessary. The implants showed no loosening or breakage after the fatigue testing. The results are compared to other available systems and the underlying biomechanics discussed.

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“…Hyper-rigid instrumentation for lumbar spinal fusion is said to promote adjacent segment instability, stress shielding, and retarded load transfer from the implant to the bony fusion mass [3,5,7,10,14,19,20,22,23,35]. Adjacent segment instability is attributed to rigid instrumentation [38].…”

Section: Introductionmentioning

confidence: 99%