In normal, physiological circumstances there is ample room in the spinal canal to accommodate the spinal cord. Our study aimed to identify the degree of compromise of the spinal canal which could be anticipated in various atlantoaxial pathological states. We examined paired atlas and axis vertebrae using high-definition radiography and simultaneous photography in both normal and simulated pathological orientations in order to measure the resultant dimension of the spinal canal and its percentage occlusion. At the extreme of physiological axial rotation (47°) the spinal canal is reduced to 61% of its cross-sectional area in neutral rotation. The spinal cord is thus safe from compromise. Atlantoaxial subluxation of up to 9 mm reduces the area of the spinal canal, in neutral rotation, to 60% with no cord compromise. Any rotation is, however, likely to cause cord compression. The mechanism of fixation in atlantoaxial rotatory subluxation could be explained by bony interlocking of the facet joint, reproducible in dry bones

Summary Statement. Bilaretal epiphysiodesis of he neurocentral cartilages causes shortening of the sagittal length of the pedicles and a subsequent spinal stenosis at the operated segments, resembling that found in patients with achrondroplasia. Introduction. The introduction of pedicle screws in the immature spine may have implications for the growth of the vertebra. The effect of blocking the growth of neurocentral cartilage (NC) is not yet fully defined. Block hypothetically leads to a bilateral symmetrical alteration of the vertebral growth. Using an experimental animal model, our goal is to analyze if a bilateral epiphysiodesis of the NC using pedicle screws is able to induce narrowing of the spinal canal in the thoracolumbar spine. Experimental animals and Methods. A total of 24 domestic pigs were operated on by bilateral blocking of the NC using pedicle screws. The animals were divided into 4 groups depending on the level of blockage: A, low thoracic levels; B, thoracolumbar transitional hinge; C, upper lumbar spine; and D, blocking of the caudal lumbar level below L5 segment. Different morphological, morphometric and standard radiological parameters were analyzed at the thoracic and lumbar vertebrae of the animals. The deviation from the physiological parameters was established by comparing all parameters obtained in the NC-blocked animals with those acquired in 14 pigs without NC blocking. These animals were considered as the control group. Results. None of the animals that underwent NC epiphysiodesis showed asymmetrical spinal growth inducing deformities in the coronal plane. There was neither rotation nor wedging of the vertebral bodies. Whatever the level involved, NC epiphysiodesis caused shortening of the sagittal length of the pedicles and a subsequent decreasing of the antero-posterior diameter of the spinal canal. These features resulted in a frank spinal stenosis at the operated levels. However, the transverse diameter of the spinal canal was conserved in the coronal plane. In the sagittal plane, blocking of the neurocentral cartilage conditioned a lumbar hyperlordosis with compensatory kyphosis of the upper level to the operated vertebra. Conclusions. Symmetrical growth arresting of neurocentral cartilages induces a narrow spinal canal by decreasing the sagittal diameter similar to that observed in patients with achondroplasia. The most affected structure was the development of the vertebral pedicles

Lumbar Spinal Canal Stenosis is a common condition in the ageing population. In Spinal decompression surgery a balance needs to be struck between the need to decompress the neural elements in the spinal canal and the risk of worsening the segmental instability that often coexists in this condition. Traditionally decompression has been supplemented with rigid stabilization e.g. fusion, which is irreversible. Recently semi-rigid or ‘soft’ stabilization philosophies have evolved. The Wallis Device is a second generation interspinous distraction/stabilization implant designed to achieve ‘soft’ segmental stabilization. In addition to stabilising the decompressed segment, it also provides a ‘block’ to full segmental extension, helping to maintain spinal canal dimensions even in the erect position. We followed up and assessed outcomes in 50 patients (25 spinal decompression + Wallis implant and 25 spinal decompression alone). The two arms of the study were matched for gender, age and level of lumbar decompression. A single surgeon was involved in each case and carried out a standard procedure of fenestration and medial facetectomy. Outcomes were assessed during clinical follow-up as well as by telephone, and included the VAS, the Oswestry Disability Index (ODI) and the EQ5D Health Domain. Early results suggest decreased incidence of recurrent symptoms and global improvement in all parameters measured, in those subjects that underwent Spinal decompression with Wallis stabilisation

Summary Statement. The spinal cord showed marked sensibility to acute compression causing complete and irreversible injury. On the contrary, the spinal cord has more ability for adaptation to slow progressive compression mechanisms having the possibility of neural recovery after compression release. Introduction. The aim of this experimental study was to establish, by means of neurophysiologic monitoring, the degree of compression needed to cause neurologic injury to the spinal cord, and analyze whether these limits are different making fast or slow compression. Material and Methods. Spinal cord was exposed from T7 to T11 in 5 domestic pigs with a mean weight of 35 kg. The T8 and T9 spinal roots were also exposed. A pair of sticks, attached to a precise compression device, was set up to both sides of the spinal cord between T8 and T9 roots. Sequentially, the sticks were approximated 0.5 mm every 2 minutes causing progressive spinal cord compression. An acute compression of the spinal cord was also reproduced by a 2.5 mm displacement of the sticks. Cord to cord motor evoked potentials were obtained with two epidural catheters, stimulating proximal to T6 and recording below the compression level, distal to T10, for each sequential approach of the sticks. Results. The mean width of the dural sac was 7.1 mm. For progressive compression, increasing latency and decreasing amplitude of the evoked potentials were observed after a mean displacement of the sticks of 3.2 ± 0.9 mm, the evoked potential finally disappearing after a mean displacement of 4.6 ± 1.2 mm. The potential returned 16.8 ± 3.2 minutes after the compression was stopped in every case. The evoked potentials immediately disappeared after an acute compression 2.5 ± 0.3 mm, without any sign of recovering after 30 minutes. Conclusion. The proposed experimental model replicates the mechanism of a spinal cord injury caused by medially displaced screws into the spinal canal, causing therefore lateral compression to the spinal cord. The spinal cord showed marked sensibility to acute compression, which caused complete and irreversible injury. On the contrary, the spinal cord has more ability for adaptation to progressive and slow compression mechanisms. From a clinical point of view, it seems mandatory to avoid maneuvers of rapid mobilization or acute, even minimal, contusions of the thoracic cord

Summary Statement. Tandem stenosis is a prevalent condition in an Asian population with the narrowest cervical canal diameters and risk factors include advanced age and increased levels of lumbar canal stenosis. Introduction. Tandem spinal stenosis (TSS) is defined as patient with concomitant spinal canal stenosis found in both cervical (C) and lumbar (L) spinal region. Few studies have reported the incidence of TSS is ranged from 5–25%, but these are all noncomparative, small cohort studies. To the best of author knowledge this is the 1st study aims to compare the prevalence of TSS and its risk factors of development in a large multiracial Asian population. Methods. A retrospective review of all mid-sagittal T2MRI whole spine image was carried out at a University hospital in year 2007. Patients with spinal tumour, fracture and congenital stenosis were excluded. Spinal stenosis was defined as canal diameter of ≤10mm, measured from the posterior cervical vertebral/disc wall to anterior surface of the corresponding lamina. Patients were divided into 4 groups, no stenosis(NS), lumbar stenosis only(LS), cervical stenosis only(CS) and TSS. Patients’ demographics, race, co-morbidities and lumbar radiological report data were examined. Potential risk factors for the development of TSS were analyzed using SPSS software. Results. 926 (479 male, 447 female) patients with average age 50 (20–96) yrs were studied. Cervical canal diameters (mm) in TSS patients were the narrowest among the 4groups with C2/3 disc: 11.6, C3/4: 9.7, C4/5: 9.4, C5/6: 8.9, C6/7: 10.0 and C7T1: 11.4mm. The incidence of TSS was 26.2%. The prevalence of TSS in Chinese was 30.7%, Indian 12.5%, Malay 22.5%. The TSS prevalence in patients with 1 level lumbar canal stenosis was 12.5%, 2 levels lumbar stenosis was 6.4% and 3 levels was 4.1%. Multivariate analysis showed patients aged between 40–59 yrs (p=0.000, Exp(B):5.8, 95%CI 2.8–12.0), aged > 60yrs (p=0.000, Exp(B): 10.5, 95%CI 4.8–22.9), Chinese race (p=0.008, Exp(B): 2.5, 95%CI 1.3–4.9), patients with 1 level lumbar stenosis (p=0.000, Exp(B): 63.3, 95%CI 29.2–137.3), 2 levels lumbar stenosis (p=0.000, Exp(B): 67.7, 95%CI 29.4–155.7) and 3 levels lumbar stenosis (p=0.000, Exp(B): 106.6, 95%CI 43.6–260.5) are statistical significant risk factors for TSS development. Conclusion. The incidence of TSS was 26.2%. TSS patients have the narrowest cervical canal measurements among the studied groups. The prevalence of TSS in Chinese is the highest (30.7%). Patients advancing in age or have increased levels of lumbar canal stenosis are at risk of developing TSS

A rat model of lumbar root constriction with an additional sympathectomy in some animals was used to assess whether the sympathetic nerves influenced radicular pain. Behavioural tests were undertaken before and after the operation.

On the 28th post-operative day, both dorsal root ganglia and the spinal roots of L4 and L5 were removed, frozen and sectioned on a cryostat (8 μm to 10 μm). Immunostaining was then performed with antibodies to tyrosine hydroxylase (TH) according to the Avidin Biotin Complex method. In order to quantify the presence of sympathetic nerve fibres, we counted TH-immunoreactive fibres in the dorsal root ganglia using a light microscope equipped with a micrometer graticule (10 x 10 squares, 500 mm x 500 mm). We counted the squares of the graticule which contained TH-immunoreactive fibres for each of five randomly-selected sections of the dorsal root ganglia.

The root constriction group showed mechanical allodynia and thermal hyperalgesia. In this group, TH-immunoreactive fibres were abundant in the ipsilateral dorsal root ganglia at L5 and L4 compared with the opposite side. In the sympathectomy group, mechanical hypersensitivity was attenuated significantly.

We consider that the sympathetic nervous system plays an important role in the generation of radicular pain.

Human bone-marrow mesenchymal stem cells have an important role in the repair of musculoskeletal tissues by migrating from the bone marrow into the injured site and undergoing differentiation. We investigated the use of autologous human serum as a substitute for fetal bovine serum in the ex vivo expansion medium to avoid the transmission of dangerous transfectants during clinical reconstruction procedures.

Autologous human serum was as effective in stimulating growth of bone-marrow stem cells as fetal bovine serum. Furthermore, medium supplemented with autologous human serum was more effective in promoting motility than medium with fetal bovine serum in all cases. Addition of B-fibroblast growth factor to medium with human serum stimulated growth, but not motility. Our results suggest that autologous human serum may provide sufficient ex vivo expansion of human bone-marrow mesenchymal stem cells possessing multidifferentiation potential and may be better than fetal bovine serum in preserving high motility.