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PubMed2005

Segment-specific resistivity improves body fluid volume estimates from bioimpedance spectroscopy in hemodialysis patients.

Discrepancies in body fluid estimates between segmental bioimpedance spectroscopy (SBIS) and gold-standard methods may be due to the use of a uniform value of tissue resistivity to compute extracellular fluid volume (ECV) and intracellular fluid volume (ICV). Discrepancies may also arise from the exclusion of fluid volumes of hands, feet, neck, and head from measurements due to electrode positions. The aim of this study was to define the specific resistivity of various body segments and to use those values for computation of ECV and ICV along with a correction for unmeasured fluid volumes. Twenty-nine maintenance hemodialysis patients (16 men) underwent body composition analysis including whole body MRI, whole body potassium (40K) content, deuterium, and sodium bromide dilution, and segmental and wrist-to-ankle bioimpedance spectroscopy, all performed on the same day before a hemodialysis. Segment-specific resistivity was determined from segmental fat-free mass (FFM; by MRI), hydration status of FFM (by deuterium and sodium bromide), tissue resistance (by SBIS), and segment length. Segmental FFM was higher and extracellular hydration of FFM was lower in men compared with women. Segment-specific resistivity values for arm, trunk, and leg all differed from the uniform resistivity used in traditional SBIS algorithms. Estimates for whole body ECV, ICV, and total body water from SBIS using segmental instead of uniform resistivity values and after adjustment for unmeasured fluid volumes of the body did not differ significantly from gold-standard measures. The uniform tissue resistivity values used in traditional SBIS algorithms result in underestimation of ECV, ICV, and total body water. Use of segmental resistivity values combined with adjustment for body volumes that are neglected by traditional SBIS technique significantly improves estimations of body fluid volume in hemodialysis patients.

Algorithms↗
PubMed2002

Period differences between segmental oscillators produce intersegmental phase differences in the leech heartbeat timing network.

Considerable experimental and theoretical effort has been exerted to understand how constant intersegmental phase relationships are produced between oscillators in segmentally organized pattern generating networks. The phase relationship between the segmental oscillators in the isolated timing network of the leech heartbeat central pattern generator is quite regular within individual preparations. However, it varies considerably among different preparations. Our goal is to determine how the phase relationships in this network are established. Here we assess whether inherent period differences, as suggested by the excitability-gradient hypothesis, play a role in establishing the phase relationships between the two coupled segmental oscillators of the leech heartbeat timing network. To do this we developed methods for reversibly uncoupling the segmental oscillators (sucrose knife) and pharmacological manipulation of the individual oscillators (split bath). Differences in inherent cycle periods between the third and fourth segmental oscillators (G3 and G4) were present in most (20 of 26) preparations. These period differences correlated with the phase differences observed between the segmental oscillators in the recoupled timing network, such that the oscillator with the faster cycle period, regardless of the segment in which it was located, led in phase in proportion to its period difference with the other oscillator. The phase differences between the original (coupled) and recoupled states of individual preparations were similar. Thus application and removal of the sucrose knife did not alter the period difference between the segmental oscillators in the timing network. Pharmacological manipulation of the uncoupled oscillators to alter the period difference between the oscillators led to similar correlated phase differences in the recoupled timing network. Across all experiments the uncoupled segmental oscillator with the faster cycle period established the cycle period of the timing network when recoupled. In conclusion, our findings indicate that an excitability-gradient plays a role in establishing the phase relationship between the segmental oscillators of the leech heartbeat central pattern generator since inherent period differences present between the oscillators are correlated to the phase relationships of the coupled/recoupled timing network.

Animals↗
PubMed2002

Algorithms for cytoplasm segmentation of fluorescence labelled cells.

Automatic cell segmentation has various applications in cytometry, and while the nucleus is often very distinct and easy to identify, the cytoplasm provides a lot more challenge. A new combination of image analysis algorithms for segmentation of cells imaged by fluorescence microscopy is presented. The algorithm consists of an image pre-processing step, a general segmentation and merging step followed by a segmentation quality measurement. The quality measurement consists of a statistical analysis of a number of shape descriptive features. Objects that have features that differ to that of correctly segmented single cells can be further processed by a splitting step. By statistical analysis we therefore get a feedback system for separation of clustered cells. After the segmentation is completed, the quality of the final segmentation is evaluated. By training the algorithm on a representative set of training images, the algorithm is made fully automatic for subsequent images created under similar conditions. Automatic cytoplasm segmentation was tested on CHO-cells stained with calcein. The fully automatic method showed between 89% and 97% correct segmentation as compared to manual segmentation.

Algorithms↗
PubMed1993

Conservation of neuroepithelial and mesodermal segments in the embryonic vertebrate head.

The organization of embryonic efferent cranial nerves is addressed here by interspecies comparison of segmentally patterned neuromeres, efferent neuronal populations and early mesodermal sources of target muscles. The segmental constancy of these three structural patterns is evaluated for elasmobranch, teleost, reptile, bird and mammal embryos and compared with the segmentally restricted expression patterns of Hox genes. A conserved series of hindbrain neuroepithelial segments (rhombomeres) is present in all of these taxa. Dye-labeling experiments demonstrate that the segmental locations of efferent neurons projecting through individual cranial nerves are likewise highly conserved. Notable segmental variation is however shown in the location of the VI and IX-XII motoneurons, suggesting the likelihood of homeotic-like changes in relations between rhombomere and neuronal 'identity' during vertebrate evolution. Since experimentally induced shifts in expression borders of Hox genes appear to be correlated with alterations in segment identity and/or neuronal phenotype, the need for further examination of segmental locations of specific neuronal groups and the segmental expression patterns of Hox genes between species is emphasized. Comparison of early cranial mesodermal subdivisions in elasmobranchs with descriptions of somitomeres in amniotes suggests that a series of axially unique mesodermal populations may also be conserved throughout vertebrates. The possibility is raised that common mechanisms of axial specification may underlie the initial appearance of segmental patterning in both neural and mesodermal layers during gastrulation. Implications of these conserved patterns for understanding the phylogenetic origin of the vertebrate head are briefly discussed.

Animals↗
PubMed1994

Constrictor and dilator responses to intracoronary acetylcholine in adjacent segments of the same coronary artery in patients with coronary artery disease. Endothelial function revisited.

BACKGROUND: In patients with angiographically detectable atherosclerosis or in those with risk factors for coronary artery disease, intracoronary acetylcholine causes coronary constriction instead of endothelium-derived relaxing factor-mediated dilation. Therefore, it has been hypothesized that diffuse endothelial dysfunction precedes development of coronary atherosclerosis. We tested this hypothesis in a systematic investigation of the effects of ascending doses of acetylcholine on the diameters of nonstenotic segments of the left coronary artery in patients with advanced atherosclerosis and coronary risk factors. METHODS AND RESULTS: Effects of intracoronary infusion of acetylcholine (10(-6) to 10(-4) mol/L) on diameters of proximal, middle, and distal nonstenotic segments of the left coronary artery were studied in 28 consecutive patients with chronic stable angina, positive exercise tests, and angiographic evidence of obstructive atherosclerosis (> or = 50% reduction in lumen diameter in at least one vessel). Two patterns of response to the maximal acetylcholine dose (10(-4) mol/L) were observed. In 21 patients (group 1), only constriction was observed in all left anterior descending and circumflex artery segments studied (16 +/- 3%, 19 +/- 4%, and 23 +/- 4%, respectively; P < .01 compared with control). In 7 other patients (group 2), both constriction and dilation were observed in adjacent segments of the same vessel; maximal acetylcholine dose caused constriction in 14 left anterior descending artery segments from a control diameter of 1.94 +/- 0.19 to 1.33 +/- 0.26 mm (37% reduction, P < .01) and dilation in 16 other segments from 1.63 +/- 0.22 to 1.93 +/- 0.21 mm (25% increase, P < .01). In the circumflex artery, this dose caused constriction in 16 segments from a control diameter of 1.88 +/- 0.14 to 1.33 +/- 0.17 mm (31% reduction, P < .01) and dilation in 12 segments from 1.37 +/- 0.12 to 1.71 +/- 0.09 mm (34% increase, P < .01). CONCLUSIONS: In 25% of patients studied with advanced angiographic coronary atherosclerosis and coronary risk factors, coronary segments with acetylcholine-inducible dilatation are present. In these patients, the endothelium is not diffusely dysfunctional as currently believed but rather shows marked segmental heterogeneity in the response to acetylcholine reflecting degrees of endothelial dysfunction.

Acetylcholine↗
PubMed1994

ST segment depression detected by continuous electrocardiography in patients with acute ischemic stroke or transient ischemic attack.

BACKGROUND AND PURPOSE: Forty percent of patients with a history of ischemic stroke or transient ischemic attack (TIA) have concomitant coronary artery disease. ST segment depression, detected by continuous electrocardiography, is associated with increased cardiac morbidity and mortality in patients with known coronary artery disease. While electrocardiographic changes have been associated with acute stroke, the etiology and significance of these changes remain unclear. In this pilot study we report the prevalence of ST segment depression and ventricular arrhythmias in patients with acute ischemic stroke or TIA monitored by continuous electrocardiography. Clinical predictors of ST segment depression and ventricular arrhythmia are also identified. METHODS: Consecutive patients presenting with acute ischemic stroke or TIA were enrolled within 72 hours of hospital admission and monitored by continuous electrocardiography for 48 hours. The electrocardiographic results were analyzed for periods of ST segment depression and ventricular arrhythmias. RESULTS: Of 51 patients with ischemic stroke or TIA, 15 (29%) had episodes of ST segment depression (95% confidence interval, 15% to 43%), and 18 (35%) had ventricular arrhythmias (95% confidence interval, 21% to 49%). In logistic regression analysis, increasing age (P < .02) and a left-sided neurological event (P < .01) were significant predictors of ST segment depression. Increasing numbers of atherosclerotic risk factors, a history of cardiac disease, and increasing or decreasing mean arterial pressure were not predictive of ST segment depression. CONCLUSIONS: Patients with acute ischemic stroke or TIA have a 29% prevalence of ST segment depression within the first 5 days after their event. In comparison, the prevalence of ST depression is 2.5% to 8% in asymptomatic adults and 43% to 60% in patients with symptomatic coronary artery disease. The association of ST segment depression with left-sided neurological events suggests that the electrocardiographic changes are in part neurologically mediated. Further study is necessary to better define the brain-heart interaction and to determine whether ST segment depression in patients with ischemic stroke or TIA reflects underlying coronary artery disease.

Acute Disease↗
PubMed1999

Associations of risk factors with segment-specific intimal-medial thickness of the extracranial carotid artery.

BACKGROUND AND PURPOSE: It is generally assumed that risk factors affect extracranial carotid intimal-medial thickness similarly among all arterial segments. This assumption underlies use of single segments or walls of segments as outcome variables for risk factor studies and clinical trials. However, if the impact of risk factors was unequal for various segments or circumferentially asymmetrical within segments, then inferences drawn from a single segment or wall might not be generalizable; furthermore, since individual segments and walls have unique histological characteristics and are differentially exposed to turbulent flow, risk factor relationships with a particular segment or wall may provide inferences regarding pathogenesis of atherosclerosis. METHODS: We evaluated associations of risk factors with intimal-medial thickness at the near and far walls of the common carotid artery, bifurcation, and internal carotid artery in 280 individuals older than 45 years equally divided between coronary artery disease cases and controls and between men and women. RESULTS: The patterns of differences in mean intimal-medial thickness among segments vary, depending on age, history of hypertension, body mass index in women, and coronary (case-control) status. The asymmetry of disease depended on blood glucose concentrations, prior history of diabetes, smoking, and coronary status. Sex, postmenopausal status, LDL cholesterol, systolic blood pressure, and history of myocardial infarction all had statistically significant relationships with intimal-medial thickness that were fairly homogeneous among arterial sites. CONCLUSIONS: Focus on an individual segments or walls of the extracranial carotid arteries may lead to overestimation or underestimation of associations of risk factors with extracranial carotid intimal-medial thickness.

Aged↗
PubMed1994

Localization of proliferating cell nuclear antigen, vimentin, c-Fos, and clusterin in the postischemic kidney. Evidence for a heterogenous genetic response among nephron segments, and a large pool of mitotically active and dedifferentiated cells.

The mechanisms leading to the recovery of the kidney after ischemic acute renal failure are poorly understood. To explore the role played by mitogenesis and dedifferentiation in this repair process and to identify whether the genetic response of the nephron segments reflects the level of susceptibility to injury, the temporal and nephron segment expressions of various proteins implicated in mitogenesis, differentiation, and injury were determined. Proliferating cell nuclear antigen (PCNA), a marker for the G1-S transition in the cell cycle and hence mitogenesis, was detected primarily in the S3 segment of the proximal tubule, with maximal expression at 2 d postischemia. Vimentin, normally present in mesenchymal cells but not epithelial cells, and hence a marker for the state of differentiation, was prominently expressed in the S3 segment 2-5 d postischemia. In the S3 segments in the outer stripe of the medulla cells that stained positively for PCNA also stained positively for vimentin. Clusterin, a marker for cell injury, was expressed primarily in the S3 segment and in the distal tubule with distinct staining patterns in each segment. None of the cells that stained with clusterin antibodies were positively stained with PCNA or vimentin antibodies. Likewise, none of the PCNA or vimentin-positive cells expressed clusterin at detectable levels. Thus, in the S3 segment, where there is significant ischemic injury, surviving cells express markers indicating that they undergo mitogenesis and dedifferentiate in the postischemic period. While there is some expression of c-Fos in the S3 segment, c-Fos was expressed predominantly, at 1 and 3 h postischemia, in the nuclei of the distal nephron, particularly in the thick ascending limb. The data support the view that the mature renal S3 segment epithelial cell can be a progenitor cell.

Animals↗
PubMed2005

English-learning infants' segmentation of verbs from fluent speech.

Two experiments sought to extend the demonstration of English-learning infants' abilities to segment nouns from fluent speech to a new lexical class: verbs. Moreover, we explored whether two factors previously shown to influence noun segmentation, stress pattern (strong-weak or weak-strong) and type of initial phoneme (consonant or vowel), also influence verb segmentation. Our results establish the early emergence of verb segmentation in English: by 13.5 months for strong-weak consonant- or vowel-initial verbs and for weak-strong consonant-initial verbs; and by 16.5 months for weak-strong verbs beginning with a vowel. This generalizes previous reports of early segmentation to a new lexical class, thereby providing additional evidence that segmentation is likely to contribute to lexical acquisition. The effects of stress pattern and onset type found are similar to those previously obtained for nouns, in that verbs with a weak-strong stress pattern and verbs beginning with a vowel appear to be at a disadvantage in segmentation. Finally, we present prosodic analyses that suggest a possible effect of prosodic boundary and pitch accent distribution on segmentation. These prosodic differences potentially explain a developmental lag in verb segmentation observed in the present study compared to earlier findings for noun segmentation.

Child Development↗
PubMed2006

Lumbar segmental mobility disorders: comparison of two methods of defining abnormal displacement kinematics in a cohort of patients with non-specific mechanical low back pain.

BACKGROUND: Lumbar segmental rigidity (LSR) and lumbar segmental instability (LSI) are believed to be associated with low back pain (LBP), and identification of these disorders is believed to be useful for directing intervention choices. Previous studies have focussed on lumbar segmental rotation and translation, but have used widely varying methodologies. Cut-off points for the diagnosis of LSR & LSI are largely arbitrary. Prevalence of these lumbar segmental mobility disorders (LSMDs) in a non-surgical, primary care LBP population has not been established. METHODS: A cohort of 138 consecutive patients with recurrent or chronic low back pain (RCLBP) were recruited in this prospective, pragmatic, multi-centre study. Consenting patients completed pain and disability rating instruments, and were referred for flexion-extension radiographs. Sagittal angular rotation and sagittal translation of each lumbar spinal motion segment was measured from the radiographs, and compared to a reference range derived from a study of 30 asymptomatic volunteers. In order to define reference intervals for normal motion, and define LSR and LSI, we approached the kinematic data using two different models. The first model used a conventional Gaussian definition, with motion beyond two standard deviations (2sd) from the reference mean at each segment considered diagnostic of rotational LSMD and translational LSMD. The second model used a novel normalised within-subjects approach, based on mean normalised contribution-to-total-lumbar-motion. An LSMD was then defined as present in any segment that contributed motion beyond 2sd from the reference mean contribution-to-normalised-total-lumbar-motion. We described reference intervals for normal segmental mobility, prevalence of LSMDs under each model, and the association of LSMDs with pain and disability. RESULTS: With the exception of the conventional Gaussian definition of rotational LSI, LSMDs were found in statistically significant prevalences in patients with RCLBP. Prevalences at both the segmental and patient level were generally higher using the normalised within-subjects model (2.8 to 16.8% of segments; 23.3 to 35.5% of individuals) compared to the conventional Gaussian model (0 to 15.8%; 4.7 to 19.6%). LSMDs are associated with presence of LBP, however LSMDs do not appear to be strongly associated with higher levels of pain or disability compared to other forms of non-specific LBP. CONCLUSION: LSMDs are a valid means of defining sub-groups within non-specific LBP, in a conservative care population of patients with RCLBP. Prevalence was higher using the normalised within-subjects contribution-to-total-lumbar-motion approach.

Adult↗
PubMed2006

Segmental stabilizing exercises and low back pain. What is the evidence? A systematic review of randomized controlled trials.

STUDY DESIGN: A systematic review of randomized controlled trials. OBJECTIVES: To evaluate the effectiveness of segmental stabilizing exercises for acute, subacute and chronic low back pain with regard to pain, recurrence of pain, disability and return to work. METHODS: MEDLINE, EMBASE, CINAHL, Cochrane Controlled Trials Register, PEDro and article reference lists were searched from 1988 onward. Randomized controlled trials with segmental stabilizing exercises for adult low back pain patients were included. Four comparisons were foreseen: (1) effectiveness of segmental stabilizing exercises versus treatment by general practitioner (GP); (2) effectiveness of segmental stabilizing exercises versus other physiotherapy treatment; (3) effectiveness of segmental stabilizing exercises combined with other physiotherapy treatment versus treatment by GP and (4) effectiveness of segmental stabilizing exercises combined with other physiotherapy treatment versus other physiotherapy treatment. RESULTS: Seven trials were included. For acute low back pain, segmental stabilizing exercises are equally effective in reducing short-term disability and pain and more effective in reducing long-term recurrence of low back pain than treatment by GP. For chronic low back pain, segmental stabilizing exercises are, in the short and long-term, more effective than GP treatment and may be as effective as other physiotherapy treatments in reducing disability and pain. There is limited evidence that segmental stabilizing exercises additional to other physiotherapy treatment are equally effective for pain and more effective concerning disability than other physiotherapy treatments alone. There is no evidence concerning subacute low back pain. CONCLUSION: For low back pain, segmental stabilizing exercises are more effective than treatment by GP but they are not more effective than other physiotherapy interventions.

Acute Disease↗
PubMed1988

Development of segmentation in zebrafish.

Recent findings on the nature and origin of segmentation in zebrafish, Brachydanio rerio, are reviewed. Segmented peripheral tissues include the trunk and tail myotomes, that are derived from somitic mesoderm, and the pharyngeal arches that are derived from head mesoderm in addition to other sources. Two major regions of the central nervous system, the spinal cord and hindbrain, are also segmentally organized, as deduced from the distribution of identified neurones in both regions and by formation of neuromeres in the hindbrain that contain single sets of these neurones. Neural and mesodermal segments in the same body region can be related to one another by their patterns of motor innervation. This relationship is simple for the spinal/myotomal segments and complex for the hindbrain/pharyngeal arch segments. Development of the segments is also complex. Mesodermal and ectodermal progenitors have separate embryonic origins and indeterminate cell lineages, and the embryonic cells migrate extensively before reaching their definitive segmental positions. Results of heat-shock experiments suggest that development of myotomal and spinal segments are regulated coordinately in postgastrula embryos. Segmental patterning may be a relatively late feature of zebrafish embryonic development.

Animals↗
PubMed2001

The establishment of segmentation in the Drosophila leg.

Segmentation is a developmental mechanism that subdivides a tissue into repeating functional units, which can then be further elaborated upon during development. In contrast to embryonic segmentation, Drosophila leg segmentation occurs in a tissue that is rapidly growing in size and thus segmentation must be coordinated with tissue growth. I demonstrate that segmentation of the Drosophila leg, as assayed by expression of the key regulators of segmentation, the Notch ligands and fringe, occurs progressively and I define the sequence in which the initial segmental subdivisions arise. I further demonstrate that the proximal-distal patterning genes homothorax and dachshund are positively required, while Distal-less is unexpectedly negatively required, to establish the segmental pattern of Notch ligand and fringe expression. Two Serrate enhancers that respond to regulation by dachshund are also identified. Together, these studies provide evidence that distinct combinations of the proximal-distal patterning genes independently regulate each segmental ring of Notch ligand and fringe expression and that this regulation occurs through distinct enhancers. These studies thus provide a molecular framework for understanding how segmentation during tissue growth is accomplished.

Animals↗
PubMed1995

Identification of a hypoperfused segment in bull's-eye myocardial perfusion images using a feed forward neural network.

Artificial neural networks are computer systems which can be trained to recognize similarities in patterns and which learn by example; one of the more straightforward types being the feed forward neural network (FFNN). We previously reported the use of FFNNs for classification of hypoperfusion patterns in bull's-eye representation of 201Tl single photon emission tomography myocardial perfusion studies and showed that, when such an image was divided into 24 segments, FFNNs could detect perfusion defects without direct comparison to a normal data base. This has been extended in this investigation to assess the ability of an FFNN, trained on data in which only a single segment was hypoperfused, to detect this abnormal segment when the hypoperfusion pattern of the other segments in the image varied. The results indicated that the network could reliably determine whether a segment was normally or under perfused, with accuracies of 99% and 100%, respectively, if all other segments were normally perfused. It could also reliably detect a normally perfused segment, even if other segments were hypoperfused, with accuracies of 95% and 98%. The network was less reliable, however, in detecting a hypoperfused segment when other segments were also hypoperfused, showing accuracies of only 74% and 88%.

Blood Flow Velocity↗
PubMed2004

Grading airway stenosis down to the segmental level using virtual bronchoscopy.

OBJECTIVE: To assess the sensitivity of noninvasive virtual bronchoscopy based on multirow detector CT scanning in detecting and grading central and segmental airway stenosis using flexible bronchoscopic findings as the reference standard. MATERIALS AND METHODS: In a blinded controlled trial, multirow detector CT virtual bronchoscopy and flexible bronchoscopy were used to search for and grade airway stenosis in 20 patients. CT scan data were obtained with a multirow detector CT scanner using 4 x 1 mm collimation. Flexible bronchoscopy findings were graded by a pulmonologist and served as the reference standard for 176 central airway regions (ie, trachea, main bronchi, and lobar bronchi) and 302 segmental airway regions. The extent of airway narrowing was categorized as grade 0 (no narrowing), grade 1 (< 50%), or grade 2 (> or =50%). RESULTS: Flexible bronchoscopy revealed 30 stenoses in the central airways and 10 in the segmental airways. Virtual bronchoscopy detected 32 stenoses in the central airways (sensitivity, 90.0%; specificity, 96.6%; accuracy, 95.5%) and 22 in the segmental airways (sensitivity, 90.0%; specificity, 95.6%; accuracy, 95.5%). The number of false-positive findings was higher in the segmental airways (13 false-positive findings) than in the central airways (5 false-positive findings), which caused a lower positive predictive value for the segmental airways (40.9%) than for the central airways (84.4%). Flexible and virtual bronchoscopic gradings correlated better for central airway stenosis (r = 0.87) than for segmental airway stenosis (r = 0.61). CONCLUSION: Although a high sensitivity was found for the detection of both central and segmental airway stenosis, the number of false-positive findings was higher for segmental airways. However, noninvasive multirow detector CT virtual bronchoscopy enables high-resolution endoluminal imaging of the airways down to the segmental bronchi.

Aged↗
PubMed1989

Cytological response of the principal cells in the initial segment of the epididymal duct to efferent duct cutting in mice.

The principal cells in the initial segment of the mouse epididymal duct were observed by light and electron microscopy over a period from 6 h to 4 weeks after efferent duct cutting. These were compared with the cells in Segment II (the segment next to the initial segment), in order to understand the functional differentiation of both segments. In the initial segment, a large number of the principal cells were degenerated and disappeared within 2 days after the operation. The remaining epithelial cells rapidly decreased in height as the degeneration proceeded and the principal cells were light- and electron-microscopically transformed into the cells similar to the principal cells in Segment II. The principal cells in Segment II showed no changes after efferent duct cutting. The findings suggest that the principal cells in the initial segment have a secretory potentiality of Segment II cells, which is normally latent but becomes manifest after the efferent duct interruption that removes the absorptive function of the testicular fluid.

Animals↗
PubMed1999

Radiculopathy and myelopathy at segments adjacent to the site of a previous anterior cervical arthrodesis.

BACKGROUND: We studied the incidence, prevalence, and radiographic progression of symptomatic adjacent-segment disease, which we defined as the development of new radiculopathy or myelopathy referable to a motion segment adjacent to the site of a previous anterior arthrodesis of the cervical spine. METHODS: A consecutive series of 374 patients who had a total of 409 anterior cervical arthrodeses for the treatment of cervical spondylosis with radiculopathy or myelopathy, or both, were followed for a maximum of twenty-one years after the operation. The annual incidence of symptomatic adjacent-segment disease was defined as the percentage of patients who had been disease-free at the start of a given year of follow-up in whom new disease developed during that year. The prevalence was defined as the percentage of all patients in whom symptomatic adjacent-segment disease developed within a given period of follow-up. The natural history of the disease was predicted with use of a Kaplan-Meier survivorship analysis. The hypothesis that new disease at an adjacent level is more likely to develop following a multilevel arthrodesis than it is following a single-level arthrodesis was tested with logistic regression. RESULTS: Symptomatic adjacent-segment disease occurred at a relatively constant incidence of 2.9 percent per year (range, 0.0 to 4.8 percent per year) during the ten years after the operation. Survivorship analysis predicted that 25.6 percent of the patients (95 percent confidence interval, 20 to 32 percent) who had an anterior cervical arthrodesis would have new disease at an adjacent level within ten years after the operation. There were highly significant differences among the motion segments with regard to the likelihood of symptomatic adjacent-segment disease (p<0.0001); the greatest risk was at the interspaces between the fifth and sixth and between the sixth and seventh cervical vertebrae. Contrary to our hypothesis, we found that the risk of new disease at an adjacent level was significantly lower following a multilevel arthrodesis than it was following a single-level arthrodesis (p<0.001). More than two-thirds of all patients in whom the new disease developed had failure of nonoperative management and needed additional operative procedures. CONCLUSIONS: Symptomatic adjacent-segment disease may affect more than one-fourth of all patients within ten years after an anterior cervical arthrodesis. A single-level arthrodesis involving the fifth or sixth cervical vertebra and preexisting radiographic evidence of degeneration at adjacent levels appear to be the greatest risk factors for new disease. Therefore, we believe that all degenerated segments causing radiculopathy or myelopathy should be included in an anterior cervical arthrodesis. Although our findings suggest that symptomatic adjacent-segment disease is the result of progressive spondylosis, patients should be informed of the substantial possibility that new disease will develop at an adjacent level over the long term.

Adolescent↗
PubMed1989

Segmental variation in microstructure, matrix synthesis and cell proliferation in rabbit flexor tendon.

An experimental culture system was designed with the purpose of studying matrix synthesis and cell proliferation in the deep flexor tendon of the rabbit forepaw. Special attention was paid to differences between three consecutive defined segments of the tendon from the region of the tendon sheath. There were two fibrocartilaginous areas in the tendon, one in the dorsal part of the proximal segment and one in the volar part of the distal segment. The intermediate segment consisted of regular tendinous tissue. The dorsal aspect of the distal segment was further characterized by a cell rich area related to the entrance of the vinculum longum. Proteoglycan synthesis in vitro was higher in the proximal and distal segments than in the intermediate, while collagen synthesis was highest in the intermediate tendinous segment. Variations in collagen content were reflected in variations in collagen synthesis. The rate of cell proliferation was highest in the intermediate segment. Segmental biochemical characteristics correlated well with morphological variations of the deep flexor tendon. These variations may reflect an adaptation to different mechanical forces acting on the tendon. The segmental variations may also be relevant for the healing capacity of the flexor tendon.

Animals↗