Results of cervical recapping laminoplasty: gross anatomical changes, biomechanical evaluation at different time points and degrees of level involvement.

BACKGROUND: Recapping laminoplasty has become the frequently-used approach to the spinal canal when bone decompression of the vertebral canal is not the goal. However, what changes will occur after surgery, and whether recapping laminoplasty can actually reduce the risk of delayed deformities remains unknown. METHODOLOGY: We designed an animal experiment using a caprine model, and partitioned the animals into in vitro and in vivo surgical groups. We performed recapping laminoplasty on one group and laminectomy on another group. These animals were sacrificed six months after operating, cervical spines removed, biomechanically tested, and these data were compared to determine whether the recapping laminoplasty technique leads to subsequent differences in range of motion. Image data were also obtained before the surgery and when the animals were killed. Besides, we investigated the initial differences in kinetics between recapping laminoplasty and laminectomy. We did this by comparing data obtained from biomechanical testing of in vitro-performed recapping laminoplasty and laminectomy. Finally, we investigated the effect that longitudinal distance has on cervical mechanics. This was determined by performing a two-level recapping laminoplasty, and then extending the laminoplasty to the next level and repeating the mechanical testing at each step. PRINCIPAL FINDINGS: There were three mainly morphological changes at the six months after laminoplasty: volume reduction and bone nonunion of the recapping laminae, irregular fibrosis formation around the facet joints and re-implanted lamina-ligamentous complex. In the biomechanical test, comparing with laminectomy, recapping laminoplasty didn't show significant differences in the immediate postoperative comparison, while recapping laminoplasty demonstrated significantly decreased motion in flexion/extension six months later. Inclusion of additional levels in the laminotomy procedure didn't lead to changes in immediate biomechanics. CONCLUSIONS: Recapping laminoplasty can't fully restore the posterior structure, but still reduced the risk of delayed cervical instability in a caprine model.

[Application of intraoperative neurophysiological monitoring in spinal cord surgery].

OBJECTIVE: To study application of intraoperative neurophysiological monitoring(IONM) in spinal cord surgery. METHODS: In the study, 24 patients with spinal cord tumors were divided into 4 groups according to the method of monitoring. Group A (ventral tumors) underwent somatosensory evoked potential (SEP) + motor evoked potential (MEP) + electromyography (EMG) monitoring, group B (intramedullary tumors) underwent SEP + MEP monitoring, group C (subdural extramedullary tumors) underwent SEP + EMG monitoring, group D (conus medullary and cauda equina lesions) underwent EMG monitoring. The relationship between changes of IONM and postoperative neurological function was analyzed. RESULTS: All of the 3 patients in group A had IONM alteration which recovered before the end of surgery, but neurological function deteriorated in 1 case. All of the 6 patients in group B had IONM alteration, of whom 5 recovered before the end of surgery, and 1 did not recover and neurological function deteriorated in this case. Seven of the nine patients in group C had IONM alteration which recovered before the end of surgery, but neurological function deteriorated in 1 case. All of the 6 patients in group D had IONM alteration which recovered before the end of surgery, but neurological function deteriorated in 1 case. CONCLUSION: IONM is useful to reduce postoperative neurological deterioration. However, IONM neurophysiological monitoring needs further improvement.

[Clinical analysis of the adolescent patients with multi-segments intramedullary spinal cord tumors].

OBJECTIVE: To prospectively analyze the clinical features and characteristics of multi-segments intramedullary spinal cord tumors in adolescent patients. METHODS: In our study, 25 consecutive adolescent patients with multi-segments intramedullary spinal cord tumors were recruited, who underwent microsurgery for the tumor using a posterior approach and were hospitalized in Peking University Third Hospital within a period of 8 years. The tumor was exposed through dorsal myelotomy. Preoperative and postoperative neurological functions were scored using the improved Japanese orthopaedic association score system (IJOA) grading system. The functional outcome was defined as postoperative IJOA score minus preoperative IJOA score. All the patients were followed-up until Oct. 30, 2011. RESULTS: There were 15 male and 10 female adolescent patients younger than 25 years. Their mean age was (15.3±6.83) years. The most common initial symptom was sensory disturbance (including pain and/or numbness, 52%, 13/25), followed by motor disturbance (including limbs weakness and gait deterioration, 24%, 6/25), pain and motor disturbance (12%, 3/25), as well as fever, limbs deformities, and sphincter dysfunction, respectively. The preoperative IJOA scores of the patients were (14.4±3.38). The postoperative IJOA scores of the patients were (15.5±3.31). The most commonly involved location was the cervicothoracic segments (36%, 9/25), followed by the conus terminalis (24%, 6/25), the cervical region(16%, 4/25), the thoracic region (16%, 4/25), and the lumbus region (8%, 2/25). The average involved segments were (4.4±1.38). The most frequent tumors were neurodevelopmental tumors (including lipoma, epidermoid cyst and teratoma) (32%, 8/25), followed by astrocytomas (28%, 7/25), ependymomas (20%, 5/25), hemangioblastomas (12%, 3/25), and glioblastomas and schwannomas, respectively. CONCLUSION: In adolescent patients with multi-segments intramedullary spinal cord tumors, the most commonly involved locations are the cervicothoracic segments and the conus terminalis, while the most frequent tumors are neurodevelopmental tumors and astrocytomas. Good prognosis in adolescent patients is observed in a long-term follow-up.