scholarly journals Biomechanical aspects of the initial stability of instrumental fixation in the treatment of subaxial cervical dislocations: an experimental study

2021 ◽  
Vol 18 (3) ◽  
pp. 43-52
Author(s):  
A. D. Lastevsky ◽  
A. I. Popelyukh ◽  
S. V. Veselov ◽  
V. A. Bataev ◽  
V. V. Rerikh
Keyword(s):  
Yield Point ◽  
Testing Machine ◽  
Shear Displacement ◽  
Spinal Segment ◽  
Thoracic Inlet ◽  
Initial Strength ◽  
T1 Slope ◽  
Articular Process ◽  
Initial Stability ◽  
Spinal Segments

Objective. To study the influence of thoracic inlet angle (TIA) and the fracture of the articular process on the initial strength of the fixation of the spinal segment during its anterior and circular instrumental surgical stabilization in an experiment on a model of the lower cervical spinal segment.Material and Methods. The material of the study was assembled models of C6–C7 spinal segments made using addictive technologies by 3D printing. After preliminary instrumentation, spinal segments were installed on the stand testing machine using specially manufactured equipment. A metered axial load simulating the native one was applied along the axis of the parameters SVA COG–C7 and C2–C7 SVA, which values were close to the value of 20 mm, at a rate of 1 mm/min until the shear strain was reached. The system’s resistance to displacement was measured, and the resulting load was evaluated. Four study groups were formed depending on the modeling of the T1 slope parameter, the integrity of the facets, and the type of instrumentation. Three tests were conducted in each group. The graphical curves were analyzed, and the values of the parameters of the neutral and elastic zones, the yield point, time to yield point, and the value of the applied load for the implementation of shear displacement were recorded. The data were subjected to comparative analysis.Results. In Group 1, anterior shear displacement of the C6 vertebra could not be induced in all series. In groups 2, 3, and 4 a shear displacement of ≥4 mm was noted in all series. In Group 3 where a fracture of the articular process was additionally modeled, the average value of the yield point was 423.5 ± 46.8 N. Elastic zone, the time to the onset of the yield point, the time at the end point or at a shear of C6 ≥4 mm did not differ significantly. In Group 4, a translational displacement of ≥4 mm was observed, though the average yield point was 1536.0 ± 40.0 N.Conclusion. The direction of the load applied to the fixed spinal segment, as well as the presence of damage to the articular processes, play a crucial role in maintaining resistance to shear deformation of the spinal segment during its instrumental stabilization. At high values of TIA (T1 slope) and the presence of fractures of the articular processes, the isolated anterior stabilization is less effective, circular fixation of 360° under these conditions gives a high initial stability to the spinal segment.

scholarly journals Commissural Interneurons in Rhythm Generation and Intersegmental Coupling in the Lamprey Spinal Cord

1999 ◽  
Vol 81 (5) ◽  
pp. 2037-2045 ◽  
Author(s):  
James T. Buchanan
Keyword(s):  
Spinal Cord ◽  
Amino Acid ◽  
Excitatory Amino Acid ◽  
Rhythmic Activity ◽  
Ventral Root ◽  
Rhythm Generation ◽  
Spinal Segment ◽  
Spinal Segments ◽  
Autocorrelation Method

Commissural interneurons in rhythm generation and intersegmental coupling in the lamprey spinal cord. To test the necessity of spinal commissural interneurons in the generation of the swim rhythm in lamprey, longitudinal midline cuts of the isolated spinal cord preparation were made. Fictive swimming was then induced by bath perfusion with an excitatory amino acid while recording ventral root activity. When the spinal cord preparation was cut completely along the midline into two lateral hemicords, the rhythmic activity of fictive swimming was lost, usually replaced with continuous ventral root spiking. The loss of the fictive swim rhythm was not due to nonspecific damage produced by the cut because rhythmic activity was present in split regions of spinal cord when the split region was still attached to intact cord. The quality of this persistent rhythmic activity, quantified with an autocorrelation method, declined with the distance of the split spinal segment from the remaining intact spinal cord. The deterioration of the rhythm was characterized by a lengthening of burst durations and a shortening of the interburst silent phases. This pattern of deterioration suggests a loss of rhythmic inhibitory inputs. The same pattern of rhythm deterioration was seen in preparations with the rostral end of the spinal cord cut compared with those with the caudal end cut. The results of this study indicate that commissural interneurons are necessary for the generation of the swimming rhythm in the lamprey spinal cord, and the characteristic loss of the silent interburst phases of the swimming rhythm is consistent with a loss of inhibitory commissural interneurons. The results also suggest that both descending and ascending commissural interneurons are important in the generation of the swimming rhythm. The swim rhythm that persists in the split cord while still attached to an intact portion of spinal cord is thus imposed by interneurons projecting from the intact region of cord into the split region. These projections are functionally short because rhythmic activity was lost within approximately five spinal segments from the intact region of spinal cord.

Supplementation of Rotator Cuff Repair with a Bioresorbable Scaffold

2002 ◽  
Vol 30 (3) ◽  
pp. 410-413 ◽  
Author(s):  
Jason L. Koh ◽  
Zoltan Szomor ◽  
George A. C. Murrell ◽  
Russell F. Warren
Keyword(s):  
Rotator Cuff ◽  
Ultimate Strength ◽  
Rotator Cuff Repair ◽  
Suture Anchor ◽  
Testing Machine ◽  
Poly Lactic Acid ◽  
Bone Bridge ◽  
Initial Strength ◽  
Bridge Model ◽  
Cuff Repair

Background Repair of a torn rotator cuff should have sufficient initial strength of the fixation to permit appropriate rehabilitation. Hypothesis Augmentation with a woven polylactic acid scaffold strengthens repairs of the rotator cuff. Study Design Controlled laboratory study. Methods In the suture-anchor model, 10 pairs of sheep infraspinatus tendons were detached and repaired to suture anchors. In half of the matched specimens, the repair was reinforced with a woven poly-lactic acid scaffold repaired with the tendon to bone. In the bone-bridge model, sutures were passed through a trough and over a bone bridge distal to the greater tuberosity; half were reinforced by the scaffold. The repairs were tested to failure with a hydraulic testing machine. Results The mean ultimate strength of suture-anchor repairs augmented with the scaffold (167.3 ± 53.9 N) was significantly greater than that of nonaugmented fixation (133.2 ± 38.2 N). Failure occurred when the tendon pulled through the sutures; the scaffold remained intact. Scaffold reinforcement of the bone bridge significantly increased the ultimate strength from 374.6 ± 117.6 N to 480.9 ± 89.2 N, and the scaffold remained intact in 8 of 10 specimens. Conclusions The scaffold significantly increased the initial strength of rotator cuff repair by approximately 25%.

Shear strength properties of plain and spirally profiled cable bolts

2015 ◽  
Vol 52 (10) ◽  
pp. 1490-1495 ◽  
Author(s):  
Naj Aziz ◽  
Ali Mirzaghorbanali ◽  
Jan Nemcik ◽  
Kay Heemann ◽  
Stefan Mayer
Keyword(s):  
Shear Strength ◽  
Testing Machine ◽  
Peak Load ◽  
Strength Properties ◽  
Shear Displacement ◽  
Vertical Shear ◽  
Cross Sectional ◽  
Cable Bolts ◽  
Strength Capacity ◽  
Cable Bolt

An experimental investigation into the performance of two 22 mm diameter, 60 t tensile strength capacity Hilti cable bolts in shear was conducted using the double-shear testing apparatus at the laboratory of the School of Civil, Mining and Environmental Engineering, Faculty of Engineering and Information Sciences, University of Wollongong. The tested cable bolts were (i) Hilti 19 wire HTT-UXG plain strand and (ii) Hilti 19 wire HTT-IXG spirally profiled (smaller cross-sectional area than the plain one) cable bolt, with indentation only on the surface of the outer strands. These cable bolts are of sealed wire construction type, consisting of an outer 5.5 mm diameter wire layer overlying the middle 3 mm diameter wire strands. Both layers are wrapped around a single solid 7 mm diameter strand wire core. The double-shearing test was carried out in 40 MPa concrete blocks, contained in concrete moulds. Cable bolts were encapsulated in concrete using Orica FB400 pumpable grout. Prior to encapsulation, each cable bolt was pre-tensioned initially to 50 kN axial force. A 500 t capacity servocontrolled compression testing machine was used for both tests, and during each test the vertical shear displacement was limited to 70 mm of travel. The rate of vertical shear displacement was maintained constant at 1 mm/min. The maximum shear load achieved for the plain strand cable was 1024 kN, while the spiral cable peak load was 904 kN, before the cable bolt wires began to individually snap, leading to the cable bolt break-up into two sections. It is apparent that spiral profiles of the outer wires weaken both the tensile and shearing strength. Finally, another set of tests was undertaken using the British Standard single-shear approach, producing lower shear strength values.

scholarly journals The transition from the elastic to the plastic state in mild steel

1913 ◽  
Vol 88 (605) ◽  
pp. 462-471 ◽  
Keyword(s):  
Stress Distribution ◽  
Mild Steel ◽  
Yield Point ◽  
Testing Machine ◽  
Plastic State ◽  
Inertia Effects ◽  
Direct Bearing ◽  
Minimum Stress ◽  
Complicated Nature

In the ordinary testing of mild steel the yield point is indicated by the sudden extension of the specimen and the accompanying drop of the beam of the testing machine which occur at this point. This fact would suggest that some reduction of the stress in the specimen under test takes place, and autographic records of tests furnish evidence of the existence of a region immediately after yield in which the relation of stress to strain is of a complicated nature, and in which the intensity of the stress is less than that which caused the yield. It has been shown by Sir Alfred Ewing and Dr. Rosenhain that the yield phenomenon is due to the formation of planes of cleavage in the crystals, along which sliding takes place. The fact that a greater stress is required to initiate the sliding movement than to maintain it has a direct bearing upon the stress distribution on surfaces subjected to non-uniform stresses when yield in any part takes place, and the object of the experiments here described was to determine the minimum stress in mild steel during the transition from the elastic to the plastic state. In the usual methods of obtaining autographic records the effect is considerably obscured by the inertia of the loading appliances, and the impossibility of limiting the extension to the degree required, so that the relation of the recorded load to the strain in the region under consideration is, in these circumstances, to a great extent fictitious. Sir Alexander B. W. Kennedy, some 27 years ago, described a method whereby inertia effects were eliminated, and obtained, as a result, a reduction of stress immediately after yield of about 16 per cent. Since the experiments here described by the present writers were carried out, Prof. W. E. Dalby has published an account of an optical autographic recorder, in which the measurement of the load is effected in a manner similar to that adopted by Kennedy, and in tests carried out on mild steel has observed a reduction of stress of about 13 per cent.

scholarly journals Development of the CT Syndesmophyte Score (CTSS) in patients with ankylosing spondylitis: data from the SIAS cohort

2017 ◽  
Vol 77 (3) ◽  
pp. 371-377 ◽  
Author(s):  
Freek de Bruin ◽  
Anoek de Koning ◽  
Rosaline van den Berg ◽  
Xenofon Baraliakos ◽  
Juergen Braun ◽  
...  
Keyword(s):  
Ankylosing Spondylitis ◽  
Structural Damage ◽  
Change Score ◽  
Spinal Segment ◽  
Change Scores ◽  
Status Score ◽  
Smallest Detectable Change ◽  
Baseline Status ◽  
Spinal Segments ◽  
Whole Spine

ObjectivesTo develop the CT Syndesmophyte Score (CTSS) for low-dose CT (ldCT) to assess structural damage in the spine of patients with ankylosing spondylitis (AS) and test its reliability.MethodsPatientswith AS in the SIAS cohort had whole spine ldCT at baseline and 2 years. Syndesmophytes were scored in coronal and sagittal planes in eight quadrants per vertebral unit (VU) as absent=0, <50% of the intervertebral disc space (IDS)=1, ≥50%=2 or bridging the IDS=3 (range 0–552). Images were scored by two readers, paired by patient, blinded to time order. Whole spine and spinal segment status and change scores were calculated. Inter-reader reliability was assessed by intraclass correlation coefficient (ICC), smallest detectable change (SDC) and frequency of scores per VU.Results49 patients (mean age 50 years (SD 9.8), 84% men, 88% human leucocyte antigen B27 positive) were included. Mean (SD) scores of reader 1 were: whole spine baseline status score 163 (126) and change score 16 (21), spinal segment baseline status scores 30 (41), 97 (77) and 36 (36) and change scores 2 (7), 12 (18) and 3 (4) for the cervical, thoracic and lumbar spine, respectively. Scores of reader 2 were similar. Whole spine status score ICC was 0.99 and 0.97–0.98 for spinal segments. Whole spine change score ICC was 0.77 and 0.32–0.75 for spinal segments. Whole-spine SDC was 14.4. Score distribution pattern per VU was similar between readers.ConclusionsUsing the CTSS, new bone formation in the spine of patients with AS can be assessed reliably. Most progression was seen in the thoracic spine.

The Development of a Machine for High-Speed Testing of Materials

1937 ◽  
Vol 135 (1) ◽  
pp. 467-483
Author(s):  
R. J. Lean ◽  
H. Quinney
Keyword(s):  
Mild Steel ◽  
Yield Point ◽  
High Speed ◽  
Testing Machine ◽  
Strain Curve ◽  
Maximum Point ◽  
Variable Speed ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
High Speed Machine

The paper contains an account of a research into the effect on metals of different speeds of fracture, using a specially designed high-speed testing machine which is described in detail. The experiments were conducted both in this machine and in a 5-ton variable-speed autographic tensile machine, on five steels, the rate of loading being varied for each. With the high-speed machine toughness, ductility, time to produce fracture, and the stress-strain curve were obtained. The results of these combined tests, given in tables and graphs, show that there is a marked increase in stress due to higher speed of testing; and also that the work required to cause fracture increases with the speed. For mild steel the stress at the initial yield point was found to be in excess of that at the maximum point, when the speed of testing was increased the ductility did not appear to suffer.

The Initiation and Propagation of the Plastic Zone in a Tension Bar of Mild Steel as Influenced by the Speed of Stretching and Rigidity of Testing Machine

1947 ◽  
Vol 14 (1) ◽  
pp. A31-A38
Author(s):  
Julius Miklowitz
Keyword(s):  
Plastic Zone ◽  
Mild Steel ◽  
Yield Point ◽  
Test Piece ◽  
Testing Machine ◽  
Tensile Specimen ◽  
Strain Diagram ◽  
Plastic Working ◽  
Tension Tests ◽  
Initiation And Propagation

Abstract The results of several tension tests with round and flat bars of mild steel and iron, under the influence of variations in speed of stretching and testing-machine rigidity, are presented. The emphasis in this work has been placed upon explaining the yield-point phenomena, as viewed externally on a stress-strain diagram, by the observations made and data taken on the internal localized yielding, as presented by the test piece. The study has been focused on the initiation of the plastic zone and the propagation of the boundaries of this zone, sometimes called the plastic working lengths, along the length of the tensile specimen.

A mechanical evaluation of pre-tapped and self-tapped screws in small bones

2007 ◽  
Vol 20 (04) ◽  
pp. 277-280 ◽  
Author(s):  
J. C. Bell ◽  
M. G. Ness
Keyword(s):  
Yield Point ◽  
Dynamic Compression ◽  
Testing Machine ◽  
Small Animal ◽  
Dorsal Surface ◽  
Materials Testing ◽  
Mean Values ◽  
Deformation Curves ◽  
Small Bones ◽  
Animal Surgery

SummaryThe purpose of this study was to compare the holding powers of 2.7 mm pre-tapped and self-tapped screws placed closely together and tightened in small bones. Pairs of metatarsals were collected from healthy, skeletally mature Greyhounds and part of a 2.7 mm dynamic compression plate was fixed to the dorsal surface of each bone using three 2.7 mm screws. Identical screws were used throughout but only one of each pair of bones had threads pre-cut using a tap prior to insertion. All of the screws were tightened before the constructs were mounted in a materials testing machine and the centrally placed screw was loaded incrementally until failure. Load-deformation curves were plotted and yield point, ultimate load to failure, stiffness and energy prior to yield point were measured. Mean values were recorded for each parameter and Student's T-test was used to test the null hypothesis that there is no difference in holding power between pre-tapped and self-tapped screws. Significant mechanical differences were not found between pre-tapped and self-tapped screws placed closely together and tightened into small bones. Self-tapped screws can be considered for use in small animal surgery even when multiple screws are to be placed closely together in relatively small pieces of bone.

Segmental innervation of the chick forelimb following embryonic manipulation

Development ◽  
1979 ◽  
Vol 54 (1) ◽  
pp. 141-154
Author(s):  
M. R. Bennett ◽  
R. Lindeman ◽  
A. G. Pettigrew
Keyword(s):  
Spinal Cord ◽  
The Other ◽  
Abnormal Development ◽  
Motor Axons ◽  
Motor Innervation ◽  
Spinal Segment ◽  
Spinal Segments ◽  
Quantitative Examination ◽  
Developing Muscle ◽  
Segmental Innervation

A number of studies have shown that the segmental innervation of some muscles in the developing limb undergoes some modification during the earliest stages of ontogeny. These observations can be interpreted in support of the hypothesis that the motor axons and muscles are matched during this period of development. As a further test of this suggestion we have made a quantitative examination of the motor innervation of the chick forelimb under conditions of controlled abnormal development. Embryos were surgically manipulated at stages before the motor axons invade the limb. The operations were controlled such that forelimbs were induced with segments deleted or reduplicated or simply that a segment of the spinal cord had been deleted. In preparations with abnormal limbs the motor innervation of the muscles present was the same as for those muscles in the normal limb. Where a spinal segment had been deleted the limbs developed normally and their innervation was completed by the remaining brachial segments. These results suggest that any particular matching property of a developing muscle does not develop as a consequence of its position in the limb relative to those segments of the limb proximal to it. Furthermore, that some muscles which are normally innervated by two spinal segments can be completely innervated by one of those spinal segments, in the absence of the other, suggests that any matching between growing axons and developing muscle cells is hierarchical rather than strictly all-or-nothing.

scholarly journals Spinal segments communicating resting sympathetic activity to postganglionic nerves of the stellate ganglion

1998 ◽  
Vol 275 (2) ◽  
pp. R400-R409 ◽  
Author(s):  
Bernat Kocsis ◽  
Katalin Gyimesi-Pelczer
Keyword(s):  
Spinal Cord ◽  
Sympathetic Activity ◽  
Stellate Ganglion ◽  
Rhythmic Activity ◽  
Spinal Segment ◽  
Preganglionic Neurons ◽  
Spinal Segments ◽  
Sympathetic Reflexes ◽  
Adjacent Segments ◽  
Vertebral Nerve

It has been shown earlier using sympathetic reflexes and anatomic techniques that preganglionic neurons controlling different effectors occupy wide and overlapping ranges of adjacent segments in the spinal cord (cardiac: T1–T7, vertebral: T2–T8). Because, however, the majority of preganglionic neurons are silent at resting states, the present study was designed to estimate the segmental map of subsets of these neurons including only those active at rest using simultaneous recordings from the inferior cardiac and vertebral nerves, under chloralose-urethan or urethan anesthesia. In 22 cats, thoracic white rami T1–T8 were cut in a sequential manner. Three-minute-long data segments were recorded between sectionings and analyzed in the frequency domain using the fast Fourier transform. We found that cardiac and vertebral active maps involved segments T3–T5 and T4–T8, respectively. In individual experiments, however, most of the power of rhythmic activity originated from only one or two segments and the dominant segments for the two nerves never overlapped. Moreover, the separation between dominant segments generating cardiac and vertebral nerve discharges was wider and the distribution of tonically active preganglionic neurons projecting to each nerve was narrower under urethan than chloralose-urethan anesthesia. We conclude that the proportion of active to quiescent preganglionic neurons regulating cardiac and vertebral nerve discharges varies from spinal segment to segment and that active neurons projecting to these nerves are nonoverlapping.

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