Biomechanical Properties Of Stability And Clinical Application In Hangman Fracture Treated With Internal Fixation And Clinical Application

Objective To observe biomechanical properties of stability on both of thedifferent types of Hangman fracture and different types of internal fixation and evaluate clinical application. Methods The study is divided in twoparts:biomechanical experiments and research of clinical case, Using six fresh humanupper cervical vertebra specimens (including C2-C4) in biomechanical experiments:the intact specimen group (Intact group), the bilateral osteotomy of the C2isthmusgroup (I group), separation of the anterior longitudinal ligament C2-3group (II group),the incision of the disk C2-3group (III group), the posterior internal fixation with C2transpedicle screws teat I group (Ⅳgroup), the posterior internal fixation with C2transpedicle screws teatⅡ group(Ⅴgroup), the posterior Short-segment C2-3transpedicle screws group (Ⅵgroup),the C2-3intervertebral fusion and anteriorinternal fixation with Zephir plate group (Ⅶ), and the C3corpectomy and C2-4anterior fusion and internal fixation with Zephir plate group (Ⅷgroup). Measurebiomechanical stabilities of all types Hangman’s fracture and internal fixation, andstatistical analysis the date which were collected. In clinical case study, we dividedthe67patients who sufferd from diffterent types of Hangman fracture in laltely5years into4groups.The posterior internal fixation with C2transpedicle screws(groupA) and the posterior short-segment C2-3transpedicle screws(group B) and the C2-3intervertebral fusion and anterior internal fixation with Zephir plate(group C) and theC3corpectomy and C2-4anterior fusion and internal fixation with Zephir plate(groupD), During follow-up, the average displacement and the average angle of C2-3weremeasured by hyperextension and hyperflexion X-rays. Results Under2.5Nmloading condition, as the instability of C2-3segment rises,ROM（range of motion）of all six directions rises, there was no significant difference.Compare to Intactgroup,all the ROMs of groupⅥ，groupⅦ，groupⅧ rise,but there was no significantdifference among the three groups.. The average follow up duration was28.6monthsin all the67patients, The average displacement and the average Angle of groupB、C and D were significant smaller than group A, but there was no significantdifference among three groups. Conclusion Both biomechanical experiments andresearch of clinical case indicate:(1) Injury of anterior longitudinal ligament C2-3and the disk C2-3can result instability of C2-3segment;(2) Although there isless effect of C2transpedicle screws on adjacent segment, C2transpedicle screws is suited to Hangman fracture type I;(3)All the C2-3intervertebral fusion andthe C3corpectomy and C2-4anterior fusion and internal fixation with Zephir plategroup and the posterior Short-segment C2-3transpedicle screws are the effectivemethods to treat Hangman fracture type II,and the posterior Short-segment C2-3transpedicle screws are also suited to Hangman fracture type III.