The Research Of Biomechanics Of Lower Cervical Spine Facet Joint

zygapophysial joints are made up of adjacent upper and lower articular facet. Bilateral zygapophysial joints,the front disc and spinal vertebrae constitute the functional spinal units together to maintain the stability of cervical spine. The activity of cervical is larger. cervical zygapophysial joints in its stability plays a vital role. cervical instability caused by Facet joint injury, degeneration is one of the most common reason of chronic neck pain which has been hailed as the engine of chronic neck pain . Cervical disc degeneration, facet hyperplasia,cohesion, such as ligamentum flavum hypertrophy may also lead to nerve root compression. Posterior facet joint excision is a relatively good nerve root decompression surgery. compared to anterior surgery , it can provide better exposure to the vision to the nerve root and surrounding structures . For hard reseted locked facet and subluxation . excising of zygapophysial joints was necessary. However, doctor must consider the relationship between excising degree and stability, excessive resection easily cause the loss of stability of cervical spine, resulting in the effect of the recent surgery good and long-term symptoms bad. clinicians often give external fixation and bone grafting after decompression in order to avoid cervical spine instability. Through biomechanical experiment ,Domestic scholars have already researched the relationship between the degree of lumbar facet joint resection, thoracic facet joint resection, bilateral cervical zygapophysial joints and the stability after resection . But for unilateral resection of cervical zygapophysial joints reported is less . This experiment by measuring the load and the activity degree of the normal cervical spine, unilateral facet joint excision, bilateral facet excision to illustrate the relationship between resection degree and the stability, and provid theoretical support for study of spinal cord injury and clinical operations.Methods:This study selected five bodies of fresh goat spine segments C2-6 level, one hour after death .examination by x-ray without tumors, deformities, trauma. On that date to embedded C2 with tooth powder .do not have embedded remote. Packaged with double-sealed plastic bag, placed in -20°C refrigerator to preserve in order to maintain its biomechanical properties similar to those with normal tissues. Removed the next day, thaw at room temperature to retain the surrounding muscles and other soft tissue. Experiments have classified into five groups,①complete specimens②left facet 25% resection group③left facet 50% resection group④left facet 75% resection group⑤left facet 100% resection group. Each facet resection specimens were between C4-5, measuring the load and the activiti in six directions (flexion, extension, left and right flexor, left and right axial rotation)after each resection. Through analysis of test data ,to study the the relationship between resetion degree and stability.Results: The experimental data analysis shows that: With the removal of articular, in the same load ,the activity is also increased. after resection25% of Unilateral facet theactivity was no significant change; after resection 50%, 75%, 100% of unilateral facet the change of activity is significant in all derections. One of the largest growth occurred in 50% -75% between the resection group, and the growth rate on average, about 19.7%. Compared with normal group, for 50% resection ,the growth rate ofactivity in four direction is an average of about 8.3% around, but no statistical significance (P> 0.05); after100% excision ,the growth rate of four direction is an average of about 46.7% around. Left and right torque load with the angle changes corresponding shown in Table 5-6. to left and right torque it has the similar law, the twist angle increasing with the facet resection, the largest increase is still 50% -75 %, averaging at around 71.5%. after100% excision, the increase in the right torque is apparent ,about 88.3%. the increase in The left side is about 87.6%. activity increase is lager in the right side, but not statistically significant.in a word after unilateral facet resection ,in the change of activity degree , left and right axial rotation> left and right flexor > flexion, extension.Conclusion: With the increase of the removal zygapophysial joints ,cervical activity gradually increased, when the removal of a broader scope than the 50%, the stability of cervical spinalwas lost.so clinical foraminal decompression surgery, tumor resection and so on ,the scope of surgical resection should be less than 50%, when larger than thisnumber we must consider granting internal fixation and fusion in order to maintain the stability of cervical spine.