Biomedical subjects

A Kaigle

Publications and source records attributed to A Kaigle.

6 recordsLinked to original sources

PubMed1999

Sacroiliac joint involvement in activation of the porcine spinal and gluteal musculature.

In the search for causes of low back pain, the sacroiliac joint has gained renewed interest as a possible pain generator. There is reason to believe that the sacroiliac joint plays a regulatory role involving reflex muscle activation, which controls trunk mobility and stability, as well as locomotion. The aim of this experimental study was to determine whether stimulation of nerves in the sacroiliac joint and joint capsule could elicit contractions in porcine gluteal or lumbar spinal muscles. Via a lateral retroperitoneal approach and using hypodermic needles, bipolar stimulating wire electrodes were inserted into the ventral area of the sacroiliac joint and directly under the surface of the capsular membrane, in 10 adolescent pigs (45 kg). This procedure was performed bilaterally, thus establishing two bilateral stimulation sites in the joints. Six electromyographic electrodes were unilaterally inserted into the following muscles: multifidus, gluteus medius, gluteus maximus, and quadratus lumborum. On stimulation within the ventral area of the joint, predominant responses occurred in both the gluteus maximus and quadratus lumborum muscles. However, when stimulating the capsule, the greatest muscular responses were detected in the multifidus muscles. This study addressed the possible regulatory function of the sacroiliac joint, namely, its involvement in activation of the spinal and gluteal muscles, which help control locomotion and body posture, as well as provide stability on the segmental level in the lumbar spine.

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PubMed1998

Inflammatory cells in full-thickness anulus injury in pigs. An experimental disc herniation animal model.

STUDY DESIGN: Inflammatory cells were studied by indirect immunocytochemistry in experimental full-thickness anulus fibrosus lesions in pigs. OBJECTIVES: First, to determine the occurrence, by immunocytochemistry, of T lymphocytes and macrophages in experimentally produced, anterolateral full-thickness disc lesions in pigs, and second, to compare the presence of inflammatory cells in 1) the injury area, 2) the adjacent noninjured part of the disc, and 3) control discs. SUMMARY OF BACKGROUND DATA: Previous studies on disc herniation material obtained from human disc surgeries have demonstrated inflammatory cells in a subgroup of herniations. Macrophages were most prevalent, being more numerous than lymphocytes. Macrophages have furthermore been suggested to be important in the resorption process of extruded disc tissue. No similar studies on an animal model of disc herniation, however, have so far been presented. METHODS: A full thickness anular incision, 10 mm long, was made with a scalpel in the L3-L4 or L4-L5 intervertebral discs of 12 adult pigs. The incision was made in the anterolateral part of the disc. Nucleus material was observed outside the injury site when tissue samples were taken, suggesting a disc herniation. Tissue then was analyzed from the area of injury, from the area adjacent to the injury, and from separate control discs from three additional pigs of the same age. Thin frozen sections were studied by indirect immunocytochemistry (alkaline phosphatase anti-alkaline phosphatase method) using monoclonal anti-human antibodies applicable to porcine tissues, T lymphocytes (CD3), and macrophages (CD68). Cells were graded as: -, absent; (+), only a few scattered cells; and +, abundant cells. Disc tissue samples were taken 1 month (three discs), 2 months (four discs), and 3 months (five discs) after the operation. RESULTS: Macrophages were present more commonly than T cells, and were abundant in seven of 12 discs (58%), with T cells abundant in four of 12 discs (33%). Only a few macrophages were present in the injured tissue from one additional disc, and scattered T cells were seen in four additional discs. Abundant macrophages were also observed in one of two discs in the adjacent noninjured area, whereas only a few T lymphocytes at the most were present in such noninjured disc tissue. In four (33%) and three (25%) injured discs, respectively, no macrophages or T lymphocytes could be found. No inflammatory cells were observed in three of 12 discs (25%). The three control discs showed no inflammatory cells. CONCLUSIONS: Inflammatory cells, predominantly macrophages, were present in a subsample of experimental discs with full-thickness anulus defects, as has previously been observed for human disc herniations. In this animal model, macrophages may have spread to adjacent noninjured parts of the disc. The induced herniation in this animal model is, however, anterolateral and may not fully correspond to clinical disc herniations, most of which are posterolateral. However, the results from this model support a role for inflammation in disc herniation.

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PubMed1998

In vivo dynamic stiffness of the porcine lumbar spine exposed to cyclic loading: influence of load and degeneration.

The dynamic axial stiffness of the L2-3 motion segment subjected to vibratory loading under intact and injured states of the intervertebral disc was studied using an in vivo porcine model. Three groups of animals with the following states of the intervertebral discs were studied: intact disc, acutely injured disc, and degenerated disc. A miniaturized servo-hydraulic exciter was used to sinusoidally vibrate the motion segment from 0.05 to 25 Hz under a compressive load with a peak value of either 100 or 200 N. The dynamic axial stiffness of the intervertebral disc was calculated at 1-Hz intervals over the frequency range. The results showed that the dynamic axial stiffness was frequency dependent. A positive relationship was found between an increase in mean dynamic stiffness and load magnitude. An increase in mean stiffness with successive exposures at the same load magnitude was observed, despite the allowance of a recovery period between loading. The greatest difference was noted between the first and second load sets. No significant change in stiffness was found due to an acute disc injury, whereas a significant increase in mean stiffness was found for the degenerated disc group as compared with the intact group. The form of the frequency response curve, however, remained relatively unaltered regardless of the degenerated state of the disc. With heavier loads, repeated loading, and/or disc degeneration, the stiffness of the intervertebral disc increases. An increase in stiffness can mean a reduction in the amount of allowable motion within the motion segment or a potentially harmful increase in force to obtain the desired motion. This may locally result in greater stresses due to an altered ability of the disc to distribute loads.

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PubMed1996

Intervertebral disc response to cyclic loading--an animal model.

The viscoelastic response of a lumbar motion segment loaded in cyclic compression was studied in an in vivo porcine model (N = 7). Using surgical techniques, a miniaturized servohydraulic exciter was attached to the L2-L3 motion segment via pedicle fixation. A dynamic loading scheme was implemented, which consisted of one hour of sinusoidal vibration at 5 Hz, 50 N peak load, followed by one hour of restitution at zero load and one hour of sinusoidal vibration at 5 Hz, 100 N peak load. The force and displacement responses of the motion segment were sampled at 25 Hz. The experimental data were used for evaluating the parameters of two viscoelastic models: a standard linear solid model (three-parameter) and a linear Burger's fluid model (four-parameter). In this study, the creep behaviour under sinusoidal vibration at 5 Hz closely resembled the creep behaviour under static loading observed in previous studies. Expanding the three-parameter solid model into a four-parameter fluid model made it possible to separate out a progressive linear displacement term. This deformation was not fully recovered during restitution and is therefore an indication of a specific effect caused by the cyclic loading. High variability was observed in the parameters determined from the 50 N experimental data, particularly for the elastic modulus E1. However, at the 100 N load level, significant differences between the models were found. Both models accurately predicted the creep response under the first 800 s of 100 N loading, as displayed by mean absolute errors for the calculated deformation data from the experimental data of 1.26 and 0.97 percent for the solid and fluid models respectively. The linear Burger's fluid model, however, yielded superior predictions particularly for the initial elastic response.

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PubMed1995

Electromyographic response of the porcine multifidus musculature after nerve stimulation.

STUDY DESIGN: In this study, a porcine model was used to study whether a nerve reaction in the anulus fibrosus of a lumbar disc or in a facet joint capsule could cause a muscular response in the multifidus musculature. OBJECTIVES: To determine if there is an interrelationship between the intervertebral disc and facet joint innervation and the multifidus musculature as a possible pain mechanism. SUMMARY OF BACKGROUND DATA: The innervation of the anulus fibrosus of the intervertebral disc and the capsule of the facet joint is well described in the literature, although the functions of these nerves are poorly understood. An interrelationship between this innervation and the paraspinal musculature has not been previously described. METHODS: Fifteen adult pigs were used to measure the electromyographic response in the multifidus musculature to electrical stimulation of the lateral region of the disc anulus and the facet joint capsule in the L1-L2 motion segment. Motor unit action potentials were recorded using three sets of bipolar needle electrodes placed into the deepest fascicles of the multifidus, bilateral to the L2, L3, and L4 spinous processes. The effect of lidocaine injection into the facet joint and subperiosteal muscle detachment on the electromyographic response were studied. RESULTS: Stimulation of the disc anulus fibrosus induced reactions in the multifidus on multiple levels and on the contralateral side, whereas stimulation of the facet joint capsule induced reactions predominantly on the same side and segmental level as the stimulation. Introduction of lidocaine into the facet joint resulted in a significantly reduced electromyographic response to either stimulation, with the most drastic reduction seen when stimulating the facet joint capsule. Subperiosteal detachment of the paraspinal muscles prevented any muscular response. CONCLUSIONS: Stimulation of the disc and the facet joint capsule produced contractions in multifidus fascicles. The clinical implications are that there may be interactive responses between injured or diseased structures, i.e., disc or facet joints, and the paraspinal musculature. Activation of the multifidus muscles may have a stabilizing effect, constraining the motion of the lumbar spine. Longstanding muscular contraction may produce ischemic conditions and may be a potential source of pain.

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PubMed1995

In vivo measurement of spinal column viscoelasticity--an animal model.

The goal of this study was to measure the in vivo viscoelastic response of spinal motion segments loaded in compression using a porcine model. Nine pigs were used in the study. The animals were anaesthetized and, using surgical techniques, four intrapedicular screws were inserted into the vertebrae of the L2-L3 motion segment. A miniaturized servohydraulic exciter capable of compressing the motion segment was mounted on to the screws. In six animals, a loading scheme consisting of 50 N and 100 N of compression, each applied for 10 min, was used. Each loading period was followed by 10 min restitution with zero load. The loading scheme was repeated four times. Three animals were examined for stiffening effects by consecutively repeating eight times 50 N loading for 5 min followed by 5 min restitution with zero load. This loading scheme was repeated using a 100 N load level. The creep-recovery behavior of the motion segment was recorded continuously. Using non-linear regression techniques, the experimental data were used for evaluating the parameters of a three-parameter standard linear solid model. Correlation coefficients of the order of 0.85 or higher were obtained for the three independent parameters of the model. A survey of the data shows that the viscous deformation rate was a function of the load level. Also, repeated loading at 100 N seemed to induce long-lasting changes in the viscoelastic properties of the porcine lumbar motion segment.

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