Differential spirochetal infectivities to vector ticks of mice chronically infected by the agent of Lyme disease

We determined whether the infectivity of the Lyme disease spirochete (Borrelia burgdorferi) to vector ticks varies with the duration of infection in laboratory mice. Thus, noninfected nymphal deer ticks were permitted to feed on two strains of early (2 months after infection) and late (8 months after infection) spirochete-infected mice. The attached ticks were removed from their hosts at specified time intervals and were thereafter examined for spirochetes by direct immunofluorescence microscopy. Spirochetes can be acquired by nymphal ticks as fast as 8 h after attachment. More than 80% of the attached ticks acquired spirochetal infection within 48 h after feeding on early spirochete-infected mice. In contrast, spirochetal infectivity to ticks was less than 50% after feeding on late spirochete-infected mice. The overall infectivity of spirochete-infected mice to ticks correlated with the duration of tick attachment. In addition, there was no adverse effect on the spirochetal infectivity to ticks by high levels of host antibody against spirochetes, and no obvious differences in infectivity to ticks was observed by the site of tick feeding. We conclude that the span of spirochetal infectivity to ticks varies with the duration of infection in mice and suggest that spirochetes may persist and may be evenly distributed in the skin of infected hosts, regardless of prominent host immunity.

Effect of ambient temperature on competence of deer ticks as hosts for Lyme disease spirochetes

We determined whether the temperature of extrinsic incubation affects the competence of vector ticks as hosts for Lyme disease spirochetes (Borrelia burgdorferi). Larval Ixodes dammini ticks that had engorged on spirochete-infected C3H mice were incubated continuously at various temperatures, and the gut contents of the resulting nymphs were examined for spirochetes by direct immunofluorescence microscopy. Spirochetes were present in virtually all nymphs kept at 27 degrees C or less for 6 months, in only 10% of those kept at 33 degrees C, and in none kept at 37 degrees C. Spirochetes became undetectable within 8 weeks when nymphs were warmed from 27 to 33 degrees C beginning at the time of molting. Nymphs became virtually noninfective for mice after incubation at temperatures higher than 27 degrees C for 2 weeks or longer. We conclude that ambient temperatures in excess of 27 degrees C are not permissive for transmission of the agent of Lyme disease.

Modulation of the trans-suppression activity of hepatitis C virus core protein by phosphorylation

We previously demonstrated that the core protein of hepatitis C virus (HCV) can suppress gene expression and replication of hepatitis B virus (HBV) in a human hepatoma cell line (HuH-7). In this study, we have characterized the phosphorylation property of HCV core protein and examined the effect of phosphorylation on its suppressive activity of HBV. Our results indicated that both the full-length HCV core protein (22 kDa) and its processed or degraded forms (14 to 18 kDa) were phosphorylated in insect cells. As demonstrated by using the glutathione S-transferase fusion protein expression system and in vitro transcription and translation system, the phosphorylation of HCV core protein was carried out by protein kinase A (PKA) and protein kinase C (PKC) in vitro. In both kinase reactions, it was determined that the phosphorylated amino acid was a serine residue. The potential phosphorylated sites in core protein were identified as residues Ser-53 and Ser-116 for PKA and Ser-53 and Ser-99 for PKC. Comparison of the phosphorylation intensities of the wild type and Ser mutants suggested that Ser-99 and Ser-116 were the major phosphorylation sites for PKC and PKA, respectively. The phosphorylation of Ser-99 and Ser-116, but not Ser-53, in HCV core protein was essential for the suppressive activity of HCV core protein on HBV gene expression and replication in HuH-7 cells. Mutation of the former two serine residues to alanine or aspartate residues led to a drastic loss of the inhibitory effects of HCV core protein on HBV gene expression (both transcription and antigen production) and pregenomic RNA encapsidation, as well as the release of HBV virus particles. In contrast, the Ser-53 mutant conferred the same level of suppressive activity as the wild type did. This property is in accordance with the observation that Ser-99 and Ser-116 are the predominant phosphorylation sites in the HCV core construct. All serine mutants (including those with mutations in PKA, PKC, and both kinase recognition sites) of HCV core protein retained the ability to translocate into the nucleus. Furthermore, wild-type HCV core protein diminished its suppressive activity when cells were treated with PKA or PKC inhibitor. In conclusion, HCV core protein is a phospho-protein and in HuH-7 cells, its trans suppression of HBV gene expression and replication is positively regulated by PKA and PKC. The role of phosphorylation in the control of trans-suppressive activity cannot be reproduced by introducing an acidic residue.(ABSTRACT TRUNCATED AT 250 WORDS)

Short report: mode of action of protective immunity to Lyme disease spirochetes

To determine whether protective immunity against the agent of Lyme disease may be expressed mainly within its tick vector prior to transmission, we passively immunized mice at various intervals after infected ticks had attached, and assayed such mice for evidence of spirochetal infection by xenodiagnosis one month after challenge. Groups of CD-1 mice were intraperitoneally infused with 0.5 ml of hyperimmune rabbit or mouse serum, reagents and quantities previously determined to protect against syringe-challenge with 10(6) low-passage JD1 spirochetes 12 hr after passive transfer. Comparison groups received normal rabbit serum or saline. All mice were protected from infection when infused no more than one day after infective ticks were allowed to attach. However, if infused three or five days post-tick attachment, 60-100% of the mice became infected. All mice became persistently infected when infused with saline or normal rabbit serum. We conclude that antibody is protective against tick-transmitted spirochetal infection only when passively administered before the spirochetes are deposited in the skin of the host. Ingested antibody may destroy spirochetes or interfere with activation and replication within the tick gut, or with dissemination to the salivary glands. Lyme disease vaccines may thus be uniquely effective because of the vulnerability of the spirochetal agent within its vector.

Ultrasound-guided biopsy of thoracic masses

BACKGROUND

Fine needle aspiration cytologic examination may be sufficient for managing patients with primary lung cancer. However, the procedure is not reliable for benign lesions and metastatic lung cancers. An attempt was made to find the influence of cell type on the results of fine needle aspiration and cutting biopsy.

METHODS

One hundred and sixteen patients with thoracic nodules or masses underwent chest ultrasound examination and percutaneous ultrasound-guided needle biopsy. All patients underwent ultrasound-guided fine needle aspiration biopsy (UGAB) and thirty-eight of them also underwent ultrasound-guided cutting biopsy (UGCB). Thoracic lesions were divided into seven groups.

RESULTS

Using UGAB alone, the diagnostic rate varied from 56% (mediastinal tumor) to 91% (lung mass). When both methods of UGAB and UGCB were evaluated, the diagnostic rate varied from 67% (pulmonary nodule) to 100% (collapsed lung with mass and pancoast tumor). When thoracic lesions were divided into carcinomatous neoplasms (n = 88) and noncarcinomatous lesions (n = 21), a higher diagnostic rate was found in the carcinomatous group than in the noncarcinomatous group (92% versus 53%, p < 0.001). Correct histologic results between both groups had no statistical significance (64% versus 56%, p > 0.05).

CONCLUSIONS

Ultrasound-guided needle biopsy has a high diagnostic yield of thoracic tumors, and carcinomatous masses can be easily diagnosed by UGCB. Noncarcinomatous masses and benign tumors frequently need UGAB to obtain a histologic diagnosis.

Use of signal-distinguishable probes in differential or sequential autoradiography in hybridization analysis

To avoid the time-consuming reprobing process in hybridization analysis, signal-distinguishable probes (32P, 35S or antigenic hapten-labeled DNA) can be added to the same hybridization mixture. After hybridization, an unambiguous result can be obtained by differential or sequential autoradiography.

Emergency department recognition of pulmonary embolism

The cases of forty-six patients who were admitted via the Emergency Department (ED) with suspected pulmonary embolism (PE), during a ten-year period, were reviewed. Ventilation perfusion lung scans were done in all patients, and pulmonary angiography was performed in 26. Thirty-six PE patients (78%) were correctly diagnosed by emergency physicians. Ten patients (22%) were erroneously diagnosed at the ED but were proved otherwise after hospitalization. The average age of the patients was 54 years, with males dominantly 67%. Overall mortality rate was 8.7%. Predisposing risk factors for PE were documented in 20 patients (43%). Prior history of thrombophlebitis (17%) or pulmonary embolism (13%), and immobilization (13%) were significant. The most common clinical features were dyspnea (76%), pleuritic pain (74%) and hemoptysis (41%). Thirty patients (65%) had tachypnea and 20 patients (43%) had tachycardia. Chest radiographs were abnormal in 35 cases (76%), and abnormal ECG findings were noted in 27 patients (59%). However, these abnormalities of chest radiographs or ECG were not sufficiently specific to confirm or exclude the diagnosis of PE. Noninvasive or contrast venography for deep vein thrombosis were performed in 31 patients (67%), of whom 17 cases (37%) had positive results. All patient received anticoagulation treatment. And six patients had thrombolytic agents as well.

Accelerated transmission of Lyme disease spirochetes by partially fed vector ticks

To determine how rapidly Lyme disease spirochetes (Borrelia burgdorferi) can be transmitted by partially fed vector ticks (Ixodes dammini), attached nymphs were removed from their hosts at various intervals post-attachment and subsequently permitted to re-feed to repletion on noninfected mice. We confirm previous reports that ticks deposit Lyme disease spirochetes in the skin of their hosts mainly after 2 days of attachment. Those that have been removed from a host within this interval can reattach and commence feeding. Spirochete-infected nymphs that have previously been attached to a host for 1 day become infectious to other hosts within another day. Noninfected nymphs acquire infection from spirochete-infected hosts within a day of attachment and become infectious to other hosts 3 to 5 days later. Virtually all ticks transmitted infection when reattaching after first feeding for 2 days. We conclude that partially fed nymphal ticks transmit spirochetal infection more rapidly than do ticks that have never been attached to a host and that infected ticks become infectious before they molt.

Topical prophylaxis for Lyme disease after tick bite in a rodent model

To determine whether infection with the Lyme disease spirochete (Borrelia burgdorferi) can be aborted by topical application of antibiotic to the site of tick attachment, individual infected nymphal deer ticks (Ixodes dammini) were permitted to feed on the ears of mice, and various antibiotics were applied to the feeding site at intervals after the replete infecting tick had detached. Infection in each mouse was determined by serology and by xenodiagnosis at 4 weeks after the bite of the infected tick. None of these mice became infected when antibiotic was topically applied to the site of tick attachment within 2 days after the spirochete-infected ticks had detached. In contrast, all nontreated and virtually all solvent-treated mice became persistently infected. Thus, persistent infection by the agent of Lyme disease can be aborted by appropriate topical application of antibiotic.

Suppression of hepatitis B virus expression and replication by hepatitis C virus core protein in HuH-7 cells

Hepatitis B and C viruses (HBV and HCV, respectively) are associated with acute and chronic liver diseases and hepatocellular carcinoma. To elucidate the molecular status of superinfection with these two hepatitis viruses, we cotransfected the full-length or truncated version of HCV structural genes (core and envelope 1) together with the cloned HBV DNA into a human hepatoma cell line (HuH-7). Expression of HBV-specific major transcripts (3.5 and 2.1 kb), as well as HBV antigens (hepatitis B surface antigen and hepatitis B e and core antigens), was reduced about two- to fourfold by the presence of the HCV structural genes. In addition, the secretion of HBV viral particles, including the viral nucleocapsid and mature virion, was drastically suppressed about 20-fold. Analysis of the intracellular HBV core protein-associated nucleic acid indicated that the encapsidated HBV pregenomic RNA was similarly reduced about 14-fold. Deletion analysis of the HCV structural genes demonstrated that the core gene alone or the fragment containing the core protein's N-terminal 122 amino acid residues conferred the same level of suppressive activity as the full-length structural genes. By indirect immunofluorescence, we found that the core protein of HCV was located in the cytoplasm of transfected HuH-7 cells at day 3 posttransfection and was targeted to the nucleus at day 6. Thus, the kinetics of the suppressive effect exerted by HCV constructs matched the timing of core protein entrance into the nucleus. Our results substantiate the clinical finding that HBV markers are suppressed by superinfection with HCV and further imply that this inhibitory effect may occur in the processes of transcription and encapsidation of HBV pregenomic RNA and may be mediated by the core protein of HCV. The deduced amino acid sequence of the HCV core protein has revealed that it is a basic protein which contains a putative DNA-binding motif (SPRG), as well as triplicate nuclear localization signals and several putative protein kinase A and C recognition sites. These characteristics imply that the HCV core protein can also function as a gene-regulatory protein.

Molecular cloning and sequence analysis of the cDNA for ancrod, a thrombin-like enzyme from the venom of Calloselasma rhodostoma

The 1.54 kb cDNA for ancrod, a thrombin-like enzyme, was cloned from a lambda ZAP cDNA library derived from the venom glands of Calloselasma (Agkistrodon) rhodostoma. The cDNA sequence reveals that ancrod is synthesized as a pre-zymogen of 258 amino acids, including a putative secretory peptide of 18 amino acids and a proposed zymogen peptide of 6 amino-acid residues. The amino-acid sequence of the predicted active form of the enzyme exhibits a high degree of sequence similarity to those of mammalian serine proteases (trypsin and pancreatic kallikrein) and other thrombin-like enzymes (batroxobin and flavoxobin). Key amino-acid residues (His43, Asp88, Ser182 and Asp176) that are thought to be involved in the substrate cleavage and in the substrate-binding reaction are conserved. Ancrod contains 13 cysteine residues. Based on alignment with the amino-acid sequences of trypsin and batroxobin, six disulphide bridges can be predicted to be present in the ancrod protein. The existence of a free cysteine, which changes the common sequence surrounding the Ser182 active site from Gly-Asp-Ser-Gly-Gly-Pro to Cys-Asp-Ser-Gly-Gly-Pro, is unusual for a serine protease.

Rapid dissemination by the agent of Lyme disease in hosts that permit fulminating infection

We determined whether the agent of Lyme disease (Borrelia burgdorferi) disseminates more rapidly following deposition in hosts that permit fulminating infection than in hosts in which infection is relatively benign. Thus, individual infected nymphal deer ticks (Ixodes dammini) were permitted to engorge on the ears of C3H mice, and the site of attachment was excised at intervals thereafter. Infection in each mouse was determined by serology and by examining previously noninfected ticks that had engorged on these mice. These results were compared with data obtained similarly by using the CD-1 strain of mice in which the agent is relatively nonpathogenic. When the site of inoculation was ablated within 2 days after the infected tick became replete, dissemination was aborted. Spirochetemia could not be demonstrated in any of these mice. We conclude that Lyme disease spirochetes disseminate from the feeding lesion of an infecting tick more rapidly in certain highly spirochete-susceptible mice than in others in which pathogenesis is less severe.

Evaluation of prognostic indices based on pulmonary and hemodynamic variables in patients with adult respiratory distress syndrome (ARDS)

Patients with established ARDS have a high mortality rate. We continuously monitored hemodynamic and respiratory parameters of 30 patients in our ICU, all had acute respiratory failure during admission then progressively developed ARDS. We compared demographic characteristics, APACHE II (acute physiology and chronic health evaluation) score, ALI (acute lung injury) score, associated MSOF (multiple systems organ failure) in the disease process, pulmonary variables, and hemodynamic variables between survivors and nonsurvivors. Six of the 12 female patients and two of the 18 male patients survived. Our female patients had a better outcome than the males (P < 0.02); and, those who were younger than 35 years old and those who had less than two organ failures during the evolution of ARDS also had a better outcome (P < 0.001 vs. P < 0.03). After ARDS had developed, there were significant differences between survivors and nonsurvivors in the APACHE II score (P < 0.03), serum albumin level (P < 0.02), mean airway pressure (P < 0.05), PCWP (P < 0.02) and SaO2 (P < 0.02). Having a higher APACHE (> or = 15, P < 0.003), lower serum ablumin level (Alb < 2.5 gm/dl, P < 0.04), higher mean airway pressure (> or = 25 cm H2O, P < 0.04), higher PCWP (> or = 14 mmHg, P < 0.006), and lower SaO2 (< 93%, P < 0.002) predicted a poorer outcome. All patients received PEEP therapy and there were no significant differences between survivors and nonsurvivors in the PEEP level applied, either at the beginning of respiratory failure, or after development of ARDS. But those who had PEEP of 6 cm H2O or higher applied at the beginning of respiratory failure and those had PEEP of less than 10 cm H2O after development of ARDS had a better outcome (P < 0.04 vs. P < 0.05). Nevertheless, more controlled trials are needed before we make any conclusion about PEEP therapy.

Adult respiratory distress syndrome in children

Adult respiratory distress syndrome or ARDS as coined by Ashbaugh et al in 1967, has been a great challenge in the field of critical care since then. It is a clinical entity which can be caused by various insults at any age. There have been several case reports of ARDS involving infants and children in the past 10 years, but pediatric ARDS is still not well recognized in Taiwan. A review of admissions to the pediatric intensive care unit in the past 2 years shows that 11 of the cases were included as pediatric ARDS combined with the expanded definition of Murray et al, and that each patient had an acute lung injury score greater than 2.5. Clinical manifestations also presented acute pulmonary distress indicating ARDS. The distribution of age ranged from 13 months to 11 years. The predisposing insults included sepsis, gastrointestinal bleeding with shock and massive blood transfusion, central nervous system infection, major trauma, near drowning, fulminant hepatitis and chemotherapy for acute leukemia. All received mechanical ventilatory support. The average peak inspiratory pressure was 46.7 +/- 6.4 cmH2O and the mean value of maximal PEEP used was 11.9 +/- 4.4 cmH2 O. Three patients developed barotrauma. Two patients survived and nine expired, a mortality rate of 82%. It is important for physicians caring for infants and children with respiratory failure to consider the diagnosis and initiate adequate ventilatory support and other resuscitation management.

Delayed dissemination of Lyme disease spirochetes from the site of deposition in the skin of mice

To determine whether the agent of Lyme disease disseminates in vertebrate hosts directly after deposition by an infecting tick, a 6-mm disk of skin was excised from the sites where nymphal Ixodes dammini ticks infected by Lyme disease spirochetes, Borrelia burgdorferi, had fed. Infection in each mouse was tested by examining xenodiagnostic ticks that had engorged on these mice 4 weeks later and by serologic testing. Generalized infection was aborted when the site of inoculation was excised within 2 days after the infecting tick detached but not after 2 weeks. In contrast, all mice became infected when the bite site remained intact. Spirochetes could be cultured from the tissues around the site of attachment solely when the sample was ablated within a week after infecting ticks detached. These observations suggest that infecting ticks deliver the agent of Lyme disease directly into the skin and that such spirochetes multiply locally for some days before disseminating to remote sites.

Haemolymph monophenol oxidase activity in Armigeres subalbatus infected with Brugia pahangi

The activity of monophenol oxidase can be elicited in the haemolymph of Armigeres subalbatus by both blood and filaria-infected blood feeding. Haemolymph collected from both blood-fed and filaria-infected mosquitoes was investigated using a quantitative radiometric assay that measured the amount of tritiated water formed during the hydroxylation of L-[3,5-3H]tyrosine to dopa. Enzyme activity in filaria-infected mosquitoes was found to be significantly lower than that found in the blood-fed mosquitoes within 3 days post-ingestion, but still remained measurable 72 h post-ingestion. The decreased enzyme activity coincided in time with the development of capsules around the microfilariae. The consumption of monophenol oxidase by the melanization of migrating microfilariae in the haemocoel of filaria-infected mosquitoes and the effects of excretory and secretory products of developing larvae on monophenol oxidase activity are suggested.

Biomechanical studies of the anterior spinal fixators after corpectomy in pigs

An unstable corpectomy porcine spinal model was created for the testing of anterior spinal fixators including: Kaneda device (KD), combination of Polster-Brinckmann prosthesis and Zielke implant (PBZ), and a new prototype device (CH). These spinal implants were examined in a one above/one below corpectomy model to determine the relative stiffness of each construct and the deformation of the adjacent discs under loading. The results indicated that the relative torsion and flexion stiffness were higher for the tested spines fixed with KD and CH. However, the relative compression stiffness of the tested spines was the same for all devices. The rigidity of the spinal constructs, which were measured around the corpectomy region showed the same tendency as above. However, the stiffness of CH and KD constructs were significantly higher than that of the PBZ construct under flexion and torsion. The difference in deformation of the upper and lower adjacent discs was not obvious among the intact spine and the spinal constructs with different devices. Clinical relevances: The corpectomy model represents a "worst case" scenario of spinal instability. In many conditions, spinal reconstructive surgery can restore axial compressive, torsional, and flexural rigidity to normal levels. These experimental conclusions apply to acute restoration of stability, rather than to rigidity after long-term cyclical loading. These three anterior fixators extended to only one cephalad level and one caudal level beyond the corpectomy defect. The new prototype device (CH) has a stability to the Kaneda device. The superior mechanical strength and simpler operative procedure of the new device provide for a potential clinical advantage in restoration of unstable spinal conditions.

Detection of human papillomavirus DNA in human cervical lesions by tissue in situ nucleic acid hybridization

Cervical cancer is one of the most common female cancers in Taiwan. Certain types of human papillomavirus (HPV) are frequently detected in the epithelial precancerous and cancerous lesions of the cervix. By the use of tissue in situ hybridization, we investigated the relationship of various types of HPV (group I, HPV-6 & 11, group II, HPV-16 & 18, group III, HPV-31, 33 & 35) with cervical condyloma, carcinoma as well as precancerous lesions. Group I HPV DNAs were mainly found in cervical condylomatous lesions (2/2) of the cervix and cervical intraepithelial neoplasia I (CIN I) (2/4), but were only occasionally found in CIN II (1/4), CIN III (1/9) or non-keratinized squamous cell carcinoma (1/15). HPV DNAs of groups II and III were mainly detected in lesions of CIN III (5/9) and invasive squamous cell carcinoma (large cell, keratinized type: 4/7; large cell, non-keratinized type: 11/15). HPV DNA sequences were invariably detectable only in the cell nuclei of condyloma or dysplastic epithelium or invasive carcinoma. However, they could not only be detected in the upper layer dysplastic cells and koilocytes but also in the well and poorly differentiated cervical cancer cells. The distribution of HPV DNA positive cells in the carcinomas fell into four different patterns: (1) upper zone and non-invasive regions of the carcinoma (11/22, 50%), (2) basal zone and invasive regions (2/22, 9%), (3) randomly scattered (7/22, 32%), and (4) extensively distributed over the whole tumor lesions (2/22, 9%). Thus, our results are consistent with a strong correlation between the presence of HPV-16, 18, 31, 33 and 35 and malignant conversion of cervical epithelial cells.

Inflammatory cloacogenic polyp of anus: report of three cases

The term of "cloacogenic anal carcinoma", "cloacogenic zone" and "cloacal membrane" have been widely used, but the term of "inflammatory cloacogenic polyp" (ICP) was first applied and published by Lobert PF and Henry DA in 1981. Here we present three cases of ICP to stress its inflammatory property, predilection to invade cloacogenic zone of anus and polypoid shape, and to differentiate it from its related lesions as concise as possible.

Roentgenographic and biomechanical analysis of lumbar fusions: a canine model

An animal model of anterior and posterior column instability was developed to allow in vivo observation of bone remodeling and arthrodesis after spinal instrumentation. Various combinations of spinal fusions and instrumentation procedures were performed after an initial anterior and posterior destabilizing lesion was created at the L5-L6 vertebral levels in 35 adult beagles. After 6 months of postoperative observation, there was improved probability of achieving a spinal fusion if spinal instrumentation had been used. All biomechanical testing was performed after removal of instrumentation to test the inherent stiffnesses and quality of the spinal fusions. The fusions performed in conjunction with instrumentation (group V = Harrington instrumentation and posterolateral fusion; group VI = Luque instrumentation and posterolateral fusion) demonstrated the greatest axial rotation stiffnesses (group V, p less than .05); axial compressive stiffness (group V, p less than .05); and flexural stiffness (group VI, p less than .05). The results show that a spinal fusion can be more reliably achieved and will be more rigid if it is accompanied by spinal instrumentation.

Biomechanical analysis of anterior and posterior instrumentation systems after corpectomy. A calf-spine model

To simulate the spinal instability that is found clinically after anterior corpectomy for the treatment of a fracture or a neoplasm, twelve fresh calf-spine segments, each containing five motion segments, were destabilized using a complete anterior corpectomy at the third lumbar level and anterior discectomies at the second and third and the third and fourth lumbar levels. Mechanical non-destructive cyclical testing in axial compression, rotation, and flexion was performed on each spinal segment after stabilization was accomplished. The three anterior-stabilization constructs that were compared were: (1) iliac strut grafting, (2) polymethylmethacrylate and anterior Harrington-rod instrumentation (the technique of Siegal and Siegal), and (3) the Kaneda anterior device. After anterior iliac-crest strut grafting, four types of posterior instrumentation were also tested sequentially: (1) Harrington distraction rods, (2) Luque rectangular instrumentation, (3) Cotrel-Dubousset transpedicular instrumentation, and (4) Steffee transpedicular screws and plates. Rotation, torque, axial displacement, and axial loads were measured during loading across the whole spinal segment between the grip points. Using an anterior extensometer, intervertebral displacement at the second, third, and fourth lumbar levels, and thus across the corpectomy defect at the third lumbar level, was recorded "on line" during testing in flexion and axial load. By recording the intervertebral displacement, the efficacy of each spinal construct in minimizing motion across the corpectomy defect could be quantified. The value for one-way analysis of variance for axial intervertebral displacement across the site of the third lumbar corpectomy was F = 10.5, p less than 0.001. The value for one-way analysis of variance for flexural intervertebral displacement across the corpectomy defect was F = 21.1, p less than 0.001. Homogeneous subsets of rigidity for torsional stiffness revealed that the least rigid constructs were iliac grafting alone, Harrington-rod instrumentation, and Luque rectangular instrumentation. The most rigid constructs were the anterior Kaneda device, transpedicular Cotrel-Dubousset instrumentation, and Steffee screws and plates.

CLINICAL RELEVANCE

After corpectomy, spinal reconstructive surgery can restore axial, torsional, and flexural rigidity to normal levels. These experimental conclusions applied to the acute restoration of stability, rather than to rigidity after long-term cyclical loading. Using the most rigid anterior system, the Kaneda device, the fixation extended only one vertebral level cephalad and one level caudad to the corpectomy defect.(ABSTRACT TRUNCATED AT 400 WORDS)

Biomechanical analysis of posterior instrumentation systems after decompressive laminectomy. An unstable calf-spine model

Mechanical non-destructive cyclical testing in rotation, axial compression, and flexion were performed on twelve fresh spinal segments from calves. Each segment contained five motion segments. Each spine was destabilized with bilateral laminectomy and facetectomy of the fourth and fifth lumbar vertebrae, resection of the pars interarticularis of the fourth lumbar vertebra, and resection of the disc between the fourth and fifth lumbar vertebrae. Sequential stabilization of each spine was used to compare the stiffness of: (1) Harrington distraction instrumentation of five levels, (2) Luque rectangular instrumentation of five levels, (3) modified Steffee transpedicular notched-rod instrumentation of three and five levels, and (4) Cotrel-Dubousset transpedicular instrumentation of three and five levels with and without transverse approximating rods. This in vitro study of a calf-spine model led to three reproducible conclusions: (1) after laminectomy and discectomy, the instrumented spine was more unstable in rotation and flexion than when it was subjected to axial compressive loads; (2) the most rigid implant was the Cotrel-Dubousset transpedicular instrumentation of five vertebral levels (p less than 0.05); and (3) with the Steffee or the Cotrel-Dubousset transpedicular instrumentation of three vertebral levels, it was possible to restore torsional, compressive, and flexural rigidity to the destabilized spine of the calf. Furthermore, transpedicular fixation of only three vertebral levels provided more in vitro stability than either traditional Harrington or Luque rectangular instrumentation, which require fixation of five vertebral levels to stabilize a spine after laminectomy.