Clinical Use of a New Nano-Hydroxyapatite/Polyamide66 Composite Artificial Lamina in Spinal Decompression Surgery: More Than 4 Years' Follow-Up.

BACKGROUND Long-term follow-up results showed that epidural scar formation and adhesion after laminectomy always affected the outcomes of repeat operations. The establishment of a barrier between scar tissue and dura was effective in preventing epidural scar formation. MATERIAL AND METHODS A nano-hydroxyapatite/polyamide66 (n-HA/PA66) artificial lamina was designed and fabricated and used to cover the opened spinal canal in patients who received laminectomy. The visual analogue scale (VAS) and Japanese Orthopedic Association (JOA) Scores, X-ray, computed tomography, and magnetic resonance imaging results were periodically recorded and evaluated. RESULTS All patients were followed up for 4-7 years, with an average period of 5.2 years. The clinical symptoms improved significantly after surgery, as the JOA scores were significantly improved after the operation and maintained to last follow-up when compared with preoperative ones (P<0.05). The vertebral canal became noticeably enlarged, from 16.7±4.7 mm to 32.9±2.2 mm, after surgery and well maintained to 32.1±1.8 mm. The lumbar lordosis was well maintained after surgery. No rupture, absorption, or dislodgement of the n-HA/PA66 lamina was found. MRI showed the spinal canal had the correct morphology, with no stenosis, no obvious scar formation, and no nerve roots or epidural sac compression. CONCLUSIONS The artificial lamina is a reasonable choice for prevention of epidural scar formation after laminectomy, in spite of the results from a small sample of cases.

Development of an in vivo mouse model of discogenic low back pain.

Discogenic low back pain (DLBP) is extremely common and costly. Effective treatments are lacking due to DLBP's unknown pathogenesis. Currently, there are no in vivo mouse models of DLBP, which restricts research in this field. The aim of this study was to establish a reliable DLBP model in mouse that captures the pathological changes in the disc and allows longitudinal pain testing. The model was generated by puncturing the mouse lumbar discs (L4/5, L5/6, and L6/S1) and removing the nucleus pulposus using a microscalpel under the microscope. Histology, molecular pathways, and pain-related behaviors were examined. Over 12 weeks post-surgery, animals displayed the mechanical, heat, and cold hyperalgesia along with decreased burrowing and rearing. Histology showed progressive disc degeneration with loss of disc height, nucleus pulposus reduction, proteoglycan depletion, and annular fibrotic disorganization. Immunohistochemistry revealed a substantial increase in inflammatory mediators at 2 and 4 weeks. Nerve growth factor was upregulated from 2 weeks to the end of the experiment. Nerve fiber ingrowth was induced in the injured discs after 4 weeks. Disc-puncture also produced an upregulation of neuropeptides in dorsal root ganglia neurons and an activation of glial cells in the spinal cord dorsal horn. These findings indicate that the cellular and structural changes in discs, as well as peripheral and central nervous system plasticity, paralleled persistent, and robust behavioral pain responses. Therefore, this mouse DLBP model could be used to investigate mechanisms underlying discogenic pain, thereby facilitating effective drug screening and development of treatments for DLBP.

The incidence of nerve root injury by high-speed drill can be reduced by chilled saline irrigation in a rabbit model.

AIMS: We aimed to evaluate the temperature around the nerve root during drilling of the lamina and to determine whether irrigation during drilling can reduce the chance of nerve root injury. MATERIALS AND METHODS: Lumbar nerve roots were exposed to frictional heat by high-speed drilling of the lamina in a live rabbit model, with saline (room temperature (RT) or chilled saline) or without saline (control) irrigation. We measured temperatures surrounding the nerve root and made histological evaluations. RESULTS: In the control group, the mean temperature around the nerve root was 52.0°C (38.0°C to 75.5°C) after 60 seconds of drilling, and nerve root injuries were found in one out of 13 (7.7%) immediately, three out of 14 (21.4%) at three days, and 11 out of 25 (44.0%) at seven days post-operatively. While the RT group showed a significantly lower temperature around the nerve root compared with the control group (mean 46.5°C; 34.5°C to 66.9°C, p < 0.001), RT saline failed to significantly reduce the incidence of nerve root injury (ten out of 26; 38.5%; odds ratio (OR) 0.96; 95% confidence interval (CI) 0.516 to 1.785; p = 0.563). However, chilled saline irrigation resulted in a significantly lower temperature than the control group (mean 39.0°C; 35.3°C to 52.3°C; p < 0.001) and a lower rate of nerve root injury (two out of 21; 9.5%, OR 0.13; 95% CI 0.02 to 0.703, p = 0.010). CONCLUSION: Frictional heat caused by a high-speed drill can cause histological nerve root injury. Chilled saline irrigation had a more prominent effect than RT in reducing the incidence of the thermal injury during extended drilling. Cite this article: Bone Joint J 2017;99-B:554-60.

Keyhole interlaminar dorsal rhizotomy for spastic diplegia in cerebral palsy.

BACKGROUND: The efficiency and safety of dorsal rhizotomies for cerebral palsy lie in the accuracy of radicular identification together with selectivity of root sectioning. Two different exposures are currently in use. The first is extended laminotomy/laminectomy from the upper lumbar level to the sacrum, which allows accurate identification of all L2-S2 roots/rootlets. The second is limited laminotomy exposing the conus/cauda equina at the thoracolumbar junction; this less invasive method limits accessibility to the roots. To optimize the accuracy and selectivity while minimizing invasiveness, the authors developed a tailored interlaminar procedure targeting the radicular levels involved in the harmful components of spasticity directly and individually. METHODS: Six patients with spastic diplegia at different levels of the Gross Motor Functional Classification System were selected. In each patient, two to three interlaminar spaces, preselected according to planning, were enlarged in the "keyhole" fashion, respecting the spinous processes and interspinous ligaments. Ventral root stimulation identified the radicular level. Dorsal root stimulation evaluated its implication in the hyperactive segmental circuits, helping quantify the percentage of rootlets to be cut. RESULTS: There were neither wound-related nor general complications. At 1 year of follow-up, X-ray examination did not reveal kyphosis or instability. In all children, the excess of spasticity was reduced. The Ashworth score decreased from 3.2 on average to 0.6 postoperatively (range: 2-4 to 0-2). Regarding the functional status at 1 year of follow-up for the three ambulatory children, the Gillette ability-to-walk score increased from 3/10 on average to 7.3/10 postoperatively (range: 2-4 to 7-8). For the three non-ambulatory children, abnormal postures, painful contractures and ease of care were much improved. CONCLUSION: Keyhole interlaminar dorsal rhizotomy (KIDr) offers direct intradural access to each of the ventral/dorsal roots, thus maximizing the reliability of anatomical mapping and allowing individual physiological testing of all targeted roots. The interlaminar approach minimizes invasiveness by respecting the posterior spine structures.