The Comprehensive Biomechanics and Load-Sharing of Semirigid PEEK and Semirigid Posterior Dynamic Stabilization Systems.

Alternatives to conventional rigid fusion have been proposed for several conditions related to degenerative disc disease when nonoperative treatment has failed. Semirigid fixation, in the form of dynamic stabilization or PEEK rods, is expected to provide compression under loading as well as an intermediate level of stabilization. This study systematically examines both the load-sharing characteristics and kinematics of these two devices compared to the standard of internal rigid fixators. Load-sharing was studied by using digital pressure films inserted between an artificially machined disc and two loading fixtures. Rigid rods, PEEK rods, and the dynamic stabilization system were inserted posteriorly for stabilization. The kinematics were quantified on ten, human, cadaver lumbosacral spines (L3-S1) which were tested under a pure bending moment, in flexion-extension, lateral bending, and axial rotation. The magnitude of load transmission through the anterior column was significantly greater with the dynamic device compared to PEEK rods and rigid rods. The contact pressures were distributed more uniformly, throughout the disc with the dynamic stabilization devices, and had smaller maximum point-loading (pressures) on any particular point within the disc. Kinematically, the motion was reduced by both semirigid devices similarly in all directions, with slight rigidity imparted by a lateral interbody device.

Electrokinetic and adsorption studies of alumina suspensions using Darvan C as dispersant.

The electrokinetic and adsorption characteristics of alumina suspensions in the presence of Darvan C as dispersant have been investigated. The interaction of Darvan C with alumina has been interpreted in terms of electrokinetic and adsorption measurements. The adsorption density of Darvan C increases greatly with decreasing pH. The isoelectric point (iep) of the sample under investigation is found to be located at pH 9.1. For pH values near and below the point of zero charge, there is an added electrostatic attractive potential for adsorption, which results in high-affinity adsorption behavior. Possible mechanisms of interaction between alumina and Darvan C are described and discussed.

Dynamic stabilization devices in the treatment of low back pain.

Soft stabilization has an important role in the treatment of the degenerative lumbar spine. Fusion of one or two motion segments may not make a big difference in the total range of motion of the lumbar spine, but preserving flexibility of a motion segment may prevent adjacent segment disease and may permit disc replacement, even when facet joints need to be excised. A favourable environment is created in the motion segment by unloading the disc and permitting near normal motion, the disc may be able to repair itself or may supplement reparative potential of gene therapy.

Results of hemivertebrectomy and fusion for symptomatic thoracic disc herniation.

We retrospectively analysed ten consecutive patients (age range 32-77 years) treated surgically from 1994 to 1999 for symptomatic thoracic disc herniation between the 6th and 12th thoracic discs. Clinically, eight patients had varying grades of back pain and eight patients had paraparesis. Radiography showed calcification in 50% of the herniated discs. Two patients had two-level thoracic disc herniation. Hemivertebrectomy followed by discectomy and fusion was carried out in all patients. Instrumentation with cages was performed in eight patients and bone grafting alone in two patients. The average follow-up was 24 months (range 13-36 months). Six patients had an excellent or good outcome, three had a fair outcome and one had a poor outcome. One patient had atelectasis, which recovered within 2 days of surgery. Another patient had developed complete paraplegia, detected at surgery by SSEPs, and underwent resurgery following magnetic resonance (MR) scan with complete corpectomy and instrumented fusion. At 2 years, she had a functional recovery. The patient with poor outcome had undergone a previous discectomy at T9/10. He developed severe back pain and generalised hyper-reflexia following corpectomy and fusion for disc herniation at T10/11. We advocate anterior transthoracic discectomy following partial corpectomy for symptomatic thoracic disc herniation between the 6th and 12th thoracic discs. This procedure offers improved access to the thoracic disc for an instrumented fusion, which is likely to decrease the risk of iatrogenic injury to the spinal cord.

Flexion osteotomy of the cervical spine: a new technique for correction of iatrogenic extension deformity in ankylosing spondylitis.

STUDY DESIGN: A new surgical technique of cervical osteotomy to correct an extension deformity of the cervical spine is described, and a case is reported. OBJECTIVES: To emphasize the disparate effect of osteotomy level on sagittal balance and gaze angle in surgical correction of global kyphotic deformity, and to describe a new surgical technique. SUMMARY OF BACKGROUND DATA: Previous reports of cervical osteotomy essentially have described extension osteotomy for correction of severe flexion deformity. To the authors' knowledge, flexion osteotomy to correct extension deformity of the cervical spine has not been described previously. METHODS: A 44-year-old woman with global kyphotic deformity caused by ankylosing spondylitis underwent corrective lumbar osteotomy at another institution. Ten years later, she experienced further development of the kyphosis, predominantly at the thoracic level, with resultant restriction of forward gaze. Thoracic corrective osteotomy was performed, which resulted in an upward deviation of her visual field. A flexion osteotomy was performed at C7-T1, using two separate posterior and anterior approaches, in one-stage, in the lateral decubitus. The use of transparent drapes permitted direct visualization of the chin-brow angle during operation. Anterior plate fixation prevented any translation at the osteotomy site. RESULTS: The osteotomy united; the gaze angle was fully corrected (45 degrees to -30 degrees ). No deterioration was noted at 2-year follow-up. CONCLUSIONS: Osteotomy at a higher level in the spine for correction of global kyphotic deformity may result in a significant overcorrection of the gaze angle upward. The authors believe that the new technique described in this report is a technically demanding but adequate and safe approach for correcting such a rare deformity.

Can hindbrain decompression for syringomyelia lead to regression of scoliosis?

Scoliosis in childhood develops secondary to syringomyelia in some children. The existing literature does not provide a clear answer as to whether surgical treatment of the syrinx can allow subsequent improvement of the spinal deformity, thus preventing the need for scoliosis surgery. This series comprised 16 patients with syringomyelia who presented with significant scoliosis in the absence of major neurological deficit. All underwent a hindbrain decompression, and follow-up ranged from 1 to 6 years (mean 2.5 years). Subsequent deformity surgery was necessary in eight cases, but the scoliosis was seen to improve or arrest its progression in six (37.5%). Improvement was found to be statistically more likely in children of younger age at the time of syrinx surgery and in those with left thoracic curves. Improvement occurred in 71.4% of those under the age of 10 at the time of hindbrain decompression.

Laparoscopic approach to L4-L5 for interbody fusion using BAK cages: experience in the first 58 cases.

STUDY DESIGN: Operative reports were reviewed for patients who underwent laparoscopic fusion at the L4-L5 level and information regarding the mobilization of the vessels was recorded. OBJECTIVE: The purpose of this study was to describe variations in the approach used to address anatomical variations in the location of the great vessel bifurcation in the region of the L4-L5 intervertebral disc space when performing laparoscopic interbody fusion procedures. SUMMARY OF BACKGROUND DATA: Recent interest in laparoscopic spine surgery using threaded cages has resulted in questions regarding the ability to safely access the L4-L5 disc using this approach. The laparoscopic transperitoneal approach to L5-S1 is below the bifurcation of the great vessels, thus requiring minimal mobilization of the iliac vessels. However, the transperitoneal approach to L4-L5 may be complicated by the bifurcation of the great vessels anterior to this disc space. Difficulty in placing two cages may occur if the vessels cannot be adequately mobilized. METHODS: Data were collected for the consecutive series of the first 58 patients (40 males, 18 females; mean age 42.5 years) undergoing laparoscopic anterior lumbar interbody fusion (ALIF) at the L4-L5 level using BAK cages. Operative notes were reviewed to determine variations in the operative approach. In particular, it was recorded if the L4-L5 disc was accessed above, or below the bifurcation of the aorta and the vena cava, or between these structures. The blood loss, operative time, and length of hospitalization were compared with respect to approach variation. RESULTS: In 30 patients, the L4-L5 disc was accessed above the great vessel bifurcation, in 18 patients below the bifurcation, and in the remaining 10 patients, by passing between the vessels. There were no statistically significant differences in the operative time, blood loss, or length of hospitalization with respect to the approach used. Three patients were converted to open procedures as a result of bleeding from segmental veins. None required transfusions and there were no postoperative sequelae. In two patients, successful endoscopic repair of segmental vein avulsion from the vena cava was performed using endoscopic loop ligatures. One patient had a secondary procedure to remove a cage that was causingnerve irritation, and one patient reported retrograde ejaculation after a two level fusion. Another patient, in whom a posterior herniation was removed, later presented with a cerebrospinal fluid leak. Most of the operative complications occurred early in the series. CONCLUSIONS: Laparoscopic transperitoneal approach to L4-L5 for insertion of threaded fusion cages is feasible. The laparoscopic L4-L5 procedure can be accomplished with few complications, provided a dedicated team of collaborative surgeons with experience in laparoscopic spine techniques is employed. Variations in vascular anatomy did not prevent successful insertion of two threaded fusion cages.

The value of MR imaging in differentiating between hard and soft cervical disc disease: a comparison with intraoperative findings.

The aim of this study is to assess the accuracy of MRI alone in the differentiation of soft cervical disc protrusion from osteophytic compression in cervical disc disease. In a retrospective study, the MRI scans of 41 patients with cervical disc disease, who had previously undergone surgery, were presented to three independent observers, randomly on two different occasions, to identify the accuracy of the diagnosis of the presence of hard or soft disc or both as a cause of compression. The observers (two neurosurgeons and one neuroradiologist) were not involved with the treatment of the cases at any stage and were unaware of the surgical findings. Their observations were compared with those of the surgeon recorded at operation. The intra-observer agreement was poor for diagnosis into three categories as hard or soft disc or both. In distinguishing between the presence or absence of hard disc, there was moderate to good (Kappa = 0.6) intra observer and fair to moderate (Kappa = 0.4) interobserver agreement. The sensitivity of diagnosis of a hard disc was high (87%) but specificity was low (44%), due to the overestimation of the presence of hard disc. There was a significantly higher incidence of hard disc in the elderly age group (76% over the fifth decade, P = 0.0073). It is concluded that MRI alone is not a very efficient diagnostic tool in distinguishing between hard and soft disc in the cervical disc disease.

Hypoglossal nerve injury as a complication of anterior surgery to the upper cervical spine.

Injury to the hypoglossal nerve is a recognised complication after soft tissue surgery in the upper part of the anterior aspect of the neck, e.g. branchial cyst or carotid body tumour excision. However, this complication has been rarely reported following surgery of the upper cervical spine. We report the case of a 35-year-old woman with tuberculosis of C2-3. She underwent corpectomy and fusion from C2 to C5 using iliac crest bone graft, through a left anterior oblique incision. She developed hypoglossal nerve palsy in the immediate postoperative period, with dysphagia and dysarthria. It was thought to be due to traction neurapraxia with possible spontaneous recovery. At 18 months' follow-up, she had a solid fusion and tuberculosis was controlled. The hypoglossal palsy persisted, although with minimal functional disability. The only other reported case of hypoglossal lesion after anterior cervical spine surgery in the literature also failed to recover. It is concluded that hypoglossal nerve palsy following anterior cervical spine surgery is unlikely to recover spontaneously and it should be carefully identified.

Tagging a Vibrio cholerae El Tor candidate vaccine strain by disruption of its hemagglutinin/protease gene using a novel reporter enzyme: Clostridium thermocellum endoglucanase A.

The celA gene encoding Clostridium thermocellum endoglucanase A was expressed in Vibrio cholerae on its own promoter and used to tag a candidate El Tor biotype cholera vaccine strain. Colonies of the tagged strain could be unequivocally distinguished by overlaying them with CM-cellulose indicator agar and Congo Red staining. Expression of celA did not affect growth of V. cholerae in vitro and in vivo. The celA gene was inserted in the chromosomal hap locus encoding V. cholerae hemagglutinin/protease, a putative "detachase", to create a hap- mutant that could be identified and scored by its halo of cellulolytic activity. The inactivation of hap had a positive effect on colonization in the infant mice model. The above results indicate that celA is a suitable marker gene for V. cholerae and hap is an appropriate locus for insertion of foreign DNA in vaccine development. Inactivation of hap, by increasing the duration of adherence, might decrease excretion of the resulting vaccine vector strain and thus increase its immunogenicity.

Antibody against the capsule of Vibrio cholerae O139 protects against experimental challenge.

Antiserum to the capsular polysaccharide of an opaque variant of Vibrio cholerae O139 strain MDO-12 recognizes capsular antigen in three different colonial variants of the strain, although the amount of recognition varies with the extent of opacity. The anti-capsular-polysaccharide serum, at subagglutinating doses, protected suckling mice against challenge with both the most opaque variant and the most translucent variant. Further studies indicated that the protection was associated with inhibition of intestinal colonization by the vibrios. These results thus highlight the potential importance of the capsule in immunoprophylaxis against cholera caused by V. cholerae O139.

Epidemic isolates of Vibrio cholerae 0139 express antigenically distinct types of colonization pili.

Vibrio cholerae belonging to the recently described serogroup 0139, which are responsible for the current cholera epidemics in India and Bangladesh, were shown to express pilus-like structures partially cross-reacting with the toxin-coregulated pilus of V. cholerae strain (0395) belonging to the 01 serogroup and classical biotype. The 0139 pili were composed of 20 kDa subunit proteins which were antigenically related to the 20 kDa pilus protein of another diarrhoeagenic non-01 V. cholerae strain (serogroup 034) isolated earlier. The pili described in this study were found to be involved in the intestinal colonization process and, therefore, may contribute towards the virulence of the 0139 epidemic isolates.

A 20-kDa pilus protein with haemagglutination and intestinal adherence properties expressed by a clinical isolate of non-01 Vibrio cholerae.

A clinical isolate of non-01 V. cholerae (10325) was shown to exhibit higher haemagglutination and intestinal adherence activities in vitro when grown in enriched media, such as trypticase soy broth (TSB) as compared to those of cells grown in a synthetic Tris-buffered or 'T'-medium. A comparison of their cell-surface protein and lipopolysaccharide profiles suggested the involvement of a 20-kDa protein in the cellular adherence process. An antiserum, raised specifically against the 20-kDa protein, recognised pilus structures on the surface of TSB grown cells. Further studies showed that the pilus was morphologically as well as antigenically distinct from toxin coregulated pilus (TCP) or other types of pili expressed by both 01 and non-01 organisms. Inhibition data established the involvement of the 20-kDa protein in haemagglutination as well as intestinal tissue adherence activities of the parent organism.

Major outer membrane proteins of Vibrio cholerae and their role in induction of protective immunity through inhibition of intestinal colonization.

Vibrio cholerae O1 organisms belonging to different biotypes and serotypes were shown to express major outer membrane proteins (MOMPs) with subunit molecular masses of 48 to 50, 40 to 43, 35 to 36, 27 to 28, and 20 kDa. Antisera raised against individual MOMPs of a V. cholerae O1 strain recognized MOMPs of corresponding molecular masses in other O1 and non-O1 strains. Serological data also suggested possible differences in the cell surface exposition of these MOMPs. However, no marked differences between V. cholerae cells grown in vitro and in vivo could be noted in respect to the expression or surface exposition of these MOMPs. Of five MOMPs studied in this work, 40- to 43- and 20-kDa cell surface proteins were shown to be of considerable importance, as antisera to these proteins induced significant protection against V. cholerae challenge in the suckling mouse model. Similar protection, although to a lesser extent, was demonstrable with the antiserum to the 27- to 28-kDa protein. These results were corroborated with the Fab (immunoglobulin G) [Fab(IgG)] fragments of the antisera, thereby suggesting that the observed protection induced by anti-MOMP antibodies did not arise as a result of bacterial clumping. Subsequent studies demonstrated that these antisera as well as their Fab (IgG) fragments induced significant inhibition of intestinal colonization of V. cholerae. The 40- to 43- and 27- to 28-kDa proteins appeared to be porinlike, while the 20-kDa protein was found to be antigenically related to TcpA (subunit A of toxin-coregulated pilus). All these results demonstrate the involvement of more than one cell surface antigen of V. cholerae in the induction of protective immunity through inhibition of intestinal colonization of vibrios.

Antibodies to outer membrane proteins of Vibrio cholerae induce protection by inhibition of intestinal colonization of vibrios.

An antiserum was raised against the outer membrane (OM) preparation of a Vibrio cholerae 01 strain (Classical, Ogawa) and rendered specific for the outer membrane proteins (OMPs) by absorption with its lipopolysaccharide (LPS). The anti-OMP serum showed reactivity against OM preparations of other 01 and non-01 V. cholerae strains in enzyme-linked immunosorbent assay. The antiserum also induced significant protection against V. cholerae challenge in the suckling mouse model. This protection was found to be independent of biotype, serotype as well as serovar of the challenge organism and was demonstrable even at subagglutinating dilutions of antiserum. The Fab (IgG) fragment, prepared from the anti-OMP serum, also induced passive protection in similar experiments. Further studies demonstrated that the anti-OMP serum as well as its Fab (IgG) fragment markedly inhibited the intestinal colonization of a highly colonizing V. cholerae 01 strain A17 (El Tor, Ogawa). These results highlight the importance of V. cholerae OMPs in immunoprophylaxis against cholera.

Tonsillitis and respiratory infections of viral aetiology in a developing country.

Among 75 clinically diagnosed cases of tonsillitis, 55 (73.3%) were found to be of viral aetiology. Serological and virological investigations identified adenovirus as the main causative agent in children as well as in adults. In only two instances, both in children, was an association with respiratory syncytial virus (RSV) in tonsillitis detected, an extremely rare finding. A cross-sectional sero-epidemiological study of respiratory infections caused by adenovirus, RSV, influenza (A,B) and para-influenza (types 1,2,3) viruses was carried out in 289 Saudi children (newborn to 15 years of age) and 86 adults (healthy male blood donors and pregnant women) using a single serological technique. In children as well as in adults, adenoviruses were the most predominant respiratory pathogens, with no marked variation in age-specific antibody prevalence rates.

Ear, nose and throat diseases in Saudi Arabia. Microbiology and clinical observations.

Clinical specimens from 243 patients attending the ENT clinics at King Abdul Aziz University Hospital, Riyadh, Saudi Arabia were investigated for the pathogens attributing to otitis media and tonsillitis. In children as well as in adults with otitis media, the main bacterial causative organisms were Staph, aureus and Ps. aeruginosa; Asp. flavus was detected in 1% and 4% of adult and children cases of otitis media. In tonsillitis H. influenzae, Strept. pneumoniae, Staph. aureus, Strept. gr. A were isolated in only 18% of the children and Strept. pneumoniae, Strept. gr A in 16% of adults. A possible involvement of viruses in tonsillitis is indicated.