Structural and biomechanical aspects of equine sacroiliac joint function and their relationship to clinical disease.

Pain originating from the sacroiliac joint (SIJ) in horses has long been associated with poor performance, yet specific diagnosis of sacroiliac dysfunction (SID) has been difficult to achieve. Clinical presentation of SID appears to fall into two categories. The first, presenting as pain and poor performance, is responsive to local analgesia of periarticular structures with poorly defined pathology. The second presents primarily as poor performance with bony pathological changes as a result of chronic instability. Diagnostic tests based on biomechanics as well as manual provocation for SIJ pain have formed the basis of tests currently used to diagnose SIJ dysfunction in humans. This review summarises the anatomy and biomechanics of the equine SIJ and current biomechanical, innervation and motor control concepts in human SID. The relationship between abnormal SIJ motion and altered neuromotor control with clinical disease of the equine SIJ are discussed. Future utilisation of these principles to develop new diagnostic and management tools for the equine SID is promising.

Movement between the equine ilium and sacrum: in vivo and in vitro studies.

REASONS FOR PERFORMING STUDY: Sacroiliac disease (SID) is an important cause of loss of performance in horses, yet little is known about the biomechanics of movement of the sacroiliac joint (SIJ). OBJECTIVES: (a) To document the presence of equine SIJ motion by measuring the change in cross-sectional area (CSA) of the dorsal portion of the dorsal sacroiliac ligament (DSIL) during application of manual forces to the pelvis, and to ascertain if this varied between horses with SID and normal horses; (b) To determine the amount and direction of motion available at the equine SIJ using 3-D orientation sensors, and how motion is limited by the DSIL and sacrotuberous ligament. METHODS: Study 1: CSA obtained ultrasonographically was compared before and during manual force application to the ilium, on a group of 10 horses, 5 with SID and 5 clinically normal. Study 2: direction and degrees of motion between sacrum and ilium were measured in 8 cadaveric SIJs. 3D orientation sensors were mounted to the fixated sacrum and the moveable ilium, and relative motion recorded between the 2 bones when manual forces were applied to the ilium. RESULTS: Study 1 showed a significant decrease in the CSA of the equine DSIL during application of manual forces to both tuber coxae (TC) (P<0.001) and tuber sacrale (TS) (P<0.001) when compared to at rest. Study 2 described range of motion to be greatest in the transverse or coronal plane, when lateral and oblique forces were applied to the pelvis, and recorded significant increases (P<0.05) in range of motion in the sagittal plane following resection of both the DSIL and sacrotuberous ligament. CONCLUSION AND POTENTIAL RELEVANCE: The change in DSIL CSA with application of manual force may be due to a lengthening of the ligament, reflecting equine SIJ motion in vivo. The motion recorded between ilium and sacrum in vitro suggests that greatest sacroiliac motion may occur in the transverse plane. Increases in range of motion following resection of ligaments give some indication of the role of each ligament.

Knowledge of results, movement type, and sex in coincidence timing.

The experiment tested 24 subjects (12 men and 12 women) on a Bassin anticipation timing task with a light stimulus velocity of 3 mph. The first aim was to compare the effects of three different types of movement responses, a simple key press with a finger, an arm movement to a key press, and a whole-body movement culminating with a kick to strike a target. The expectation that sensorimotor integra tion of the movement responses would be reflected in the accuracy and consistency of anticipation timing was supported by the results which showed that the key-press task was superior to either the arm or whole-body movement responses. This finding emphasises the role movement variables have in defining situational constraints and indicate that proficiency in coincidence anticipation appears to be influenced by the planning and organisation required for movement execution. The second aim was to examine the question of whether verbal knowledge of results was redundant. Analysis showed that verbal knowledge of results was redundant under all movement conditions. Further research is needed to identify conditions in which the visual system does not provide the motor control system with adequate information for appropriate execution of movement. An evaluation of sex differences in performance and learning comprised the third aim. That men were significantly more accurate and more consistent was in accord with previous evidence. Women might have a more conservative approach to responding than men. Effects of repeated practice, an inherent part of these studies, supported the principle that effective learning accrues from repeatedly solving the coincidence-timing problem. It was concluded that further investigation of movement variables is needed to develop understanding of how they are coupled with perceptual variables in coincidence-timing contexts.

Coincidence timing of finger, arm, and whole body movements.

Two experiments investigated the effects of different types of movement responses on coincidence timing skill. The view was taken that the sensory-motor integration of the movement responses would be reflected in the accuracy and consistency of anticipation timing. A Bassin anticipation timer provided a light stimulus velocity of 3 mph for both experiments and the movements studied included a simple key press using a finger, an arm movement to a key press, and whole body movements culminating with a kick or step to a target. The experiments were modelled closely on the seminal study by Grose (1967). The results of Exp. 1 supported our prediction by demonstrating superiority of the finger task over the two larger movements for all measures of coincidence timing ability. The purpose of Exp. 2 was to compare the slightly different versions of the whole body task-that used in the first experiment and that used by Grose (1967). The results confirmed the close similarity of the two movement tasks and re-affirmed the results of Exp. 1. Exp. 2 also investigated sex effects on coincidence timing ability and, in contrast to previous evidence indicating that females perform with less accuracy and consistency than do males, no significant differences were found. Analysis of practice effects showed that, although there were no significant improvements over trial blocks in Exp. 1, there were significant improvements in Exp. 2. Comparisons with other research suggests that repeated practice in solving a coincident timing problem using whole body movements can lead to improved performance. In general, the findings are consistent with the constructs of action theory and emphasize the roles perceptual and movement variables have in defining situational constraints. Also, findings indicate that proficiency in coincidence anticipation appears to be influenced by the planning and organisation required for movement execution.

Development of postural responses during standing in healthy children and children with spastic diplegia.

Studies on the development of balance control show a clear developmental progression of the emergence of organized muscle response patterns, with tonic background muscle activity decreasing and phasic bursts of activity emerging in all three agonist muscles in a synergic group (gastrocnemius-hamstrings-trunk extensors or tibialis anterior-quadriceps-abdominals) just prior to the onset of independent stance. The rudimentary ability to adapt postural responses to changing task conditions is present in children as young as 1 year of age. Older children with spastic diplegia have muscle activation patterns typically seen in normal children who are at the pull-to-stand stage of development, including poorly organized (proximal activated before distal muscles) responses with a high degree of antagonist co-activation. When normal children were asked to stand in a crouched posture like the CP children, the additional constraint caused muscle response patterns to resemble those of CP children, suggesting that differences in balance control in CP children are due to both CNS deficits and biomechanical changes in postural alignment.

Response Timing Accuracy as a Function of Movement Velocity and Distance.

In two experiments, patterns of response error during a timing accuracy task were investigated. In Experiment 1, these patterns were examined across a full range of movement velocities, which provided a test of the hypothesis that as movement velocity increases, constant error (CE) shifts from a negative to a positive response bias, with the zero CE point occurring at approximately 50% of maximum movement velocity (Hancock & Newell, 1985). Additionally, by examining variable error (VE), timing error variability patterns over a full range of movement velocities were established. Subjects (N = 6) performed a series of forearm flexion movements requiring 19 different movement velocities. Results corroborated previous observations that variability of timing error primarily decreased as movement velocity increased from 6 to 42% of maximum velocity. Additionally, CE data across the velocity spectrum did not support the proposed timing error function. In Experiment 2, the effect(s) of responding at 3 movement distances with 6 movement velocities on response timing error were investigated. VE was significantly lower for the 3 high-velocity movements than for the 3 low-velocity movements. Additionally, when MT was mathematically factored out, VE was less at the long movement distance than at the short distance. As in Experiment 1, CE was unaffected by distance or velocity effects and the predicted CE timing error function was not evident.

Patterns of adrenergic receptors and adrenergic agonists underlying cardiovascular responses to a psychological challenge.

Numerous physiological and biochemical factors contribute to the dynamic regulation of the cardiovascular system. This study used a cluster analytic statistical technique to discern patterns of adrenergic receptors and adrenergic agonists underlying cardiovascular responses to a laboratory challenge. Fifty hypertensive and normotensive black and white individuals had their beta- and alpha-adrenergic receptor sensitivity determined through agonist infusions. Norepinephrine, epinephrine, blood pressure, and heart rate responses to a standardized mental arithmetic task were also obtained. The cluster analysis identified four subgroups of individuals having distinct patterns of receptor and neurohormonal regulation of end-organ responses. In general, the data indicated that end-organ cardiovascular responses are, in part determined by the sensitivity of adrenergic receptors and the accompanying catecholamine responses. The findings also suggest that for some individuals nonadrenergic factors play a more dominant role than adrenergic mechanisms in determining cardiovascular pressor responses.

[Experimental study on the possibility of tuberculosis transmission by coitus]. / Ansteckungsmöglichkeit der Tuberkulose durch Kohabitation im Tierexperiment.

The following conslusion can be drawn from the results obtained: 1. A male guinea pig, in which tuberculosis of genitals was caused by BK-typus humanus, might infect a healthy female guinea pig in cohabitation. The experiments proved that the possibility of such infection was expressed as the ratio of 1:6. 2. On the basis of the results obtained, we feel entitled to draw our patients' attention to the possibility of infection resulting from sexual intercourse and the necessity of application of suitable contraceptives. It should also be noted that appropriate examination of the patients' present partners is indispensable.