Biomechanical study of different approach for lumbar interbody fusion surgeries under vibration load / 生物医学工程学杂志

The human spine injury and various lumbar spine diseases caused by vibration have attracted extensive attention at home and abroad. To explore the biomechanical characteristics of different approaches for lumbar interbody fusion surgery combined with an interspinous internal fixator, device for intervertebral assisted motion (DIAM), finite element models of anterior lumbar interbody fusion (ALIF), transforaminal lumbar interbody fusion (TLIF) and lateral lumbar interbody fusion (LLIF) are created by simulating clinical operation based on a three-dimensional finite element model of normal human whole lumbar spine. The fusion level is at L4-L5, and the DIAM is implanted between spinous process of L4 and L5. Transient dynamic analysis is conducted on the ALIF, TLIF and LLIF models, respectively, to compute and compare their stress responses to an axial cyclic load. The results show that compared with those in ALIF and TILF models, contact forces between endplate and cage are higher in LLIF model, where the von-Mises stress in endplate and DIAM is lower. This implies that the LLIF have a better biomechanical performance under vibration. After bony fusion between vertebrae, the endplate and DIAM stresses for all the three surgical models are decreased. It is expected that this study can provide references for selection of surgical approaches in the fusion surgery and vibration protection for the postsurgical lumbar spine.

Prognostic Factors of Locking Unicortical System in Internal Fixation for Cervical Spine Lesions

Although anterior cervical plate provide excellent fixation for anterior column, the potential risk for injury to spinal cord or soft tissue has been the reason why they have not gained universal acceptance. For this reason, anterior cervical locking plating systems were designed to avoid such surgical complications. The authors reviewed 98 patients who underwent anterior cervical fusion with anterior cervical locking unicortical system during the period of January 1995 to December 1997. Mean follow up period was 8.4months. Morscher plate placement was done in 24 and Orion plate was applied in 74. We compare the safety and efficacy of these tow plates. The two groups were comparable in demographic details, mean age(Morscher 41, Orion 47) average fusion level(Morscher 1.25, Orion 1.55) and fusion rate(Morscher 95.8%, Orion 100%). For comparison of hardware related complication, two patients(2.7%) showed screw loosening without without need for reoperation in Orion plate group. In Morscher plate group, 1 patient(4.1%) developed plate fracture and 1 patient (4.1%) developed screw loosening, but did not require delete(re) operation. Non-hardware related complications in Morscher group were seen in 2 patients(8.2%): one delete CSF leakage and the other being postoperative hematoma collection. In Orion plate group, complications were developed in 9 patients(12%): two nerve injuries(recurrent laryngeal and hypoglossal nerve), two CSF leakages, two wound infections, one postoperative hematoma collection, two donor graft site pains. Reoperations were done in two cases(2%) due to two postoperative hematoma collection one in Morscher plate group and one in Orion plate group. In one level fusion, longer operation time was required in Morscher plate group(217+/-93.7min) compared to Orion plate group(157+/-47min)(p<0.05). In this study two types of anterior cervical locking plate and screw system had good bony fusion and cervical stabilization with few instrument related complication. Moreover, allograft bone fusion with anterior cervical locking plate and screw system had good solid bony fusion without donor site morbidity. Instrument related complications were more common in Morscher locking plate and screw system.

A Case of Basilar Impression

A case of basilar impression surgically treated in a female patient aged 22 years is presented. A myriad of abnormal neurologic findings were present that were secondary to compression of neural tissue by anormalous bony structure at craniovertebral junction. Metrizamide computerized tomography with coronal and sagittal reconstruction identified bony abnomalities and displacement of the surrounding neural structures. The surgical intervention for the treatment of the basilar impression consisted of ventral decompression by transoral odontoidectomy and of dorsal decompression by an enlargement of foramen magnum and by laminectomy of C1, followed by occipito-atlanto-axial bony fusion.