| Objective:Establish an articular hyperplastic, stable fixation-fusion and interspinous dynamic 3-dimensional lumbar spine finite element models, comparing mechanical aspects under various loads of all three models. Followed by a clinical prospective study of the DIAM interspinous dynamic stabilization system, comparatively observe the relationship between finite element model mechanical analysis and clinical results, to determine biomechanical feasibility and clinical value of the DIAM interspinous dynamic stabilization system.Method:Using computed topography scanning (CT), obtain lumbar spine DICOM setting imaging data of healthy Chinese male volunteers to design and form a sample model, followed by laser scanning production of DIAM interspinous dynamic stabilization system image data with conversion using Mimics software. Using Mimics graphically depict pedicle screws, portray and mimic articular hyperplasia, stable fixation and fusion, and interspinous dynamic fixation of lumbar spine segments L4-L5, forming a dynamically mobile realistic model. Performing comparative analysis of all three models using Abaqus software, observing axial pressure, torque pressure under flexion and extension upon spinal stress points of each 3-dimensional model. Following Clinical Studies Ethical Committee approval for clinical study using the DIAM interspinous dynamic stabilization system, between June 2006 and January 2008, performed prospective investigation of DIAM interspinous dynamic stabilization system in 8 lumbar cases; obtaining pre-surgical standing position lumbar anteroposterior and sagittal/extension/flexion X rays, CTM, post-surgical standing position lumbar anteroposterior and sagittal X ray and standing position lumbar anteroposterior and sagittal/extension/flexion X rays during follow up, measuring the following parameters from each set of X rays: interspinous gap height, active angle between surgical segment and adjacent segmental vertebrae, intervertebral disc index, lumbar lordosis, as well as collecting ODI (Oswestry Disability Index) and VAS (Visual Analogue Scale) data to compare surgical efficacy, analyzing the various parametric factors on surgery, feasibility of the DIAM system in clinical analysis.Results:During finite element analysis in cases with articular hyperplasia, under various loading conditions upon vertebral articular joints of superior and inferior vertebrae, stress is concentrated in the isthmus and lower vertebral articular, and increased median vertebral articular stress, intervertebral disc stress is lower than that of bone structure, with concentrated stress upon the exterior posterior fibrous annulus. After stable fixation and fusion, there is significant reduction in stress of vertebral articular joints, isthmus and fibrous annulus, however there is increased stress along the pedicle screw pathway and pedicle screw-cage junction point. With the DIAM system, despite concentrated stress upon the superior, inferior vertebral articular joints and isthmus, stress fulcrum and peak is magnificently reduced, including that of fibrous annulus, the DIAM system also prevents direct internal contact with the skeletal structure affecting adjacent segment concentrated stress. Prospective clinical analysis of DIAM system transplantation presents satisfactory with favorable ODI and VAS scores compared through pre-surgical and post-surgical scores, with positive statistical significance (P<0.05), there is no statistical significance (P> 0.05) between post-surgical time point results; surgical segment (L4/5) mobility pre and post surgery indicated statistical significance (P<0.05), with little variation and significance in post surgical time difference (P> 0.05); surgical segment interspinous gap height pre, immediately post surgery and 3 months post surgery indicated statistical significance (P< 0.05), again with no difference in post surgical time (P>0.05); presenting with no statistical significance between pre and post surgical sub-surgical segments mobility range(L3/4, L5/S1), intervertebral disc index and lumbar lordosis. There is negative dependency between ODI, VAS scores and surgical segment mobility.Conclusion:DIAM interspinous dynamic stabilization system opens up intervertebral space through expanding distraction, thus decreasing superior, inferior vertebral articular joint and isthmus stress, without disturbing internal skeletal structure and direct transplant-skeletal interference. Thus system is favorable to the pedicle screw internal fixation and articular fusion surgery. The DIAM system expands interspinous space, increasing posterior intervertebral height, technically decreasing posterior fibrous annulus stress, postponing degeneration, increasing ligament tensility to decrease surgical segment mobility, improving stability. The system offers a generalized stable platform, improving lumbar degenerative disease induced pain, with positive clinical results. However still requiring long term observation and further examination for prolonged efficacy. |
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