Quantitative and qualitative analyses of spinal canal encroachment during cervical laminectomy using the kerrison rongeur versus High-Speed burr.

BACKGROUND: Several cervical laminectomy techniques have been described. One commonly used method involves making bilateral trough laminotomies using either a Kerrison rongeur or a high speed burr, and then removing the lamina en-bloc. Alternatively, some surgeons prefer to thin the lamina with the burr, and then remove the lamina in a piecemeal fashion using Kerrison rongeurs. Some surgeons have warned against the potential risk of iatrogenic spinal cord injury from inserting the Kerrison footplate into a stenotic canal. We aim to quantify the amount of canal encroachment for various methods of cervical laminectomies. METHODS: Three attending spine surgeons and two fellows each performed laminectomies using C5 sawbones models. The canal was completely filled with modeling putty to simulate a stenotic spinal cord. Bilateral trough laminotomies were performed using a 1 mm Kerrison, a 2 mm Kerrison, and a 3 mm matchstick high-speed burr. Piecemeal laminectomies were performed with a 2 mm Kerrison. A blinded spine surgery fellow performed all quantitative measurements. Three blinded researchers qualitatively ranked the amount of "canal encroachment". RESULTS: The average canal encroachment was 0.50 ± 0.45mm for the burr, 1.37 ± 0.68 mm for the 1 mm Kerrison, and 1.47 ± 0.37 mm for the 2 mm Kerrison (p = .002). There was a statistically significant difference between the burr and 1 mm Kerrison (p = .01) and between the burr and the 2 mm Kerrison (p = .001). There was no statistical difference between the 1 mm and 2 mm Kerrison (p = .78). The mean rank of the burr group, the Kerrison rongeur group, and the piecemeal group were 1.41, 1.94, and 2.65, respectively, on an ordinal scale of 1-3. CONCLUSION: When performing a trough laminotomy, the high-speed burr results in less canal encroachment compared to 1 mm or 2 mm Kerrison rongeurs. In the setting of a stenotic spinal canal, spine surgeons should consider using the burr to perform laminectomy to minimize the degree of canal encroachment.

Therapeutic effects of adenovirus-mediated growth and differentiation factor-5 in a mice disc degeneration model induced by annulus needle puncture.

BACKGROUND CONTEXT: The therapeutic strategies that have thus far been used for the treatment of intervertebral disc degeneration (IDD) have focused on relieving the symptoms, although reversal of the degeneration remains an important challenge for the effective treatment of IDD. Growth and differentiation factor-5 (GDF5), of which deficiency leads to early disc degeneration changes, has the potential to increase proliferation of disc cells and expression of extracellular matrix proteins. PURPOSE: The purpose of the study was to develop a lumbar disc degeneration model in mice and determine the effect of adenoviral GDF5 gene therapy. STUDY DESIGN: The study design was to compare the degeneration changes of discs punctured by different-size needles to develop a mice lumbar disc degeneration model and to evaluate the effects of in vivo gene therapy for the mice disc degeneration model by an adenoviral vector carrying GDF5 gene. METHODS: A lumbar disc degeneration model was developed by needle punctures to the discs in Balb/c mice. Afterward, a gene therapy treatment to disc degeneration was evaluated. Two of the mice lumbar discs were randomly chosen to be punctured by a 30-gauge needle and then injected with adenovirus that had been engineered to express either the luciferase gene (Ad-Luc) or the GDF5 gene (Ad-GDF5). Animals were analyzed by bioluminescent imaging, radiographic, and magnetic resonance imaging (MRI) scanning, then sacrificed at 1, 2, 4, or 8 weeks after operation, and subjected to histological and biochemical assays. RESULTS: By the detection of T2-weighted MRI scanning and histological study, the degeneration was found in all of the discs punctured by different-size needles. But the development of the degeneration in the discs injured by the 30-gauge needle was more reliable and moderate compared with that in other groups. The detection of luciferase activity by bioluminescent imaging revealed that adenovirus survived and the introduced genes were expressed over 6 weeks after injection. There were no T2-weighted MRI signals in the mice injected with either Ad-Luc or Ad-GDF5 up to 4 weeks after operation. At 6 and 8 weeks, T2-weighted signals were detected in the Ad-GDF5 group but none in the Ad-Luc control group. The percent disc height index (%DHI) was significantly decreased (approximately 20%) by 1 week after injury in both groups, indicating the development of disc degeneration. At 2 weeks, the %DHI in the mice injected with Ad-GDF5 increased significantly compared with that of the mice injected with Ad-Luc; the increase was sustained for the rest of the experiment period. The disc histology treated with Ad-GDF5 was improved compared with that in the control group. Glycosaminoglycan (GAG) levels were significantly decreased in the Ad-Luc injection group since 2 weeks after injury, and the DNA content had diminished by 4 weeks after the operation. In contrast, in the discs injected with Ad-GDF5, there was no decrease in the GAG and DNA levels after injury throughout the 8-week treatment period. CONCLUSIONS: Disc degeneration animal model can be developed by using needle puncture to the discs in mice. The adenovirus is an effective vehicle for gene delivery with rapid and prolonged expression of target protein and resulting improvement in markers of disc degeneration. Ad-GDF5 gene therapy could restore the functions of injured discs and has the potential to be an effective treatment.