Biomedical subjects

K M Refshauge

Publications and source records attributed to K M Refshauge.

6 recordsLinked to original sources

PubMed1998

Movement detection at the human big toe.

1. To be detected, movements of the interphalangeal joint of the big toe must be greater than at other joints. This poor acuity may arise because the anatomy of the foot and ankle results in poor coupling between the toe and the muscles that operate it. To vary this coupling, the effect of ankle position on proprioceptive acuity at the toe was measured. 2. We measured proprioceptive acuity at the toe with the ankle in different positions and found that ankle plantarflexion did improve acuity. This implies that, with the ankle at mid-range or dorsiflexed, toe movement is inadequately transferred to muscle fascicles. 3. To determine actual changes in fascicle length of the toe extensor, movements of extensor hallucis longus near the toe and at the muscle-tendon junction were measured during surgical exposure in one subject. Ankle position greatly affected movement transfer from toe to muscle-tendon junction: no tendon movement was transferred with the ankle dorsiflexed, but all movement was transferred with the ankle plantarflexed. 4. When the relationship between joint rotation and muscle fascicle length measured in vivo was used to express the smallest detectable movements of the toe as proportional changes in muscle fascicle length, these detectable changes were similar to those at all other limb joints. This suggests that change in muscle fascicle length is of major interest to the nervous system.

Adult↗

PubMed1998

Movement detection at the distal joint of the human thumb and fingers.

To determine whether proprioceptive acuity is the same at all digits, particularly when postured as in a 'grasp', we imposed 10 degrees movements at the distal joint of the thumb, index and ring finger, at three velocities; 1.25 degrees/s, 2.5 degrees/s and 5 degrees/s. The test joint was initially flexed by 25 degrees and the joints proximal to the test joint were maintained in a standard posture for each study. When in a grasp posture that disengaged the extensor muscles at the distal joint of the finger, movement detection at the thumb was superior to that at the fingers for all velocities. However, when the fingers were positioned so that all proprioceptive inputs were able to contribute (i.e. cutaneous, joint and both flexor and extensor muscle afferents), proprioceptive acuity was similar for the three digits. Loss of local cutaneous (and joint) inputs by digital anaesthesia significantly impaired performance at all digits, suggesting a critical role for cutaneous input in normal proprioceptive sensibility at all distal joints of the digits. Anaesthesia of the extensor muscle afferents innervating the thumb did not affect its proprioceptive acuity. Thus, for the thumb, the extensor muscle afferents do not provide critical information. The greater change in muscle fascicle length for the thumb's long flexor muscle (3% per 10 degrees) compared with that in the finger flexor muscles (e.g. 0.1% per 10 degrees) could contribute to the thumb's performance. There appears to be less redundancy of muscle and non-muscle signals for the fingers than for the thumb, because a reduction in either cutaneous or muscle input significantly impaired acuity at the fingers. Overall, when the hand is in a grasping posture, irrespective of the contribution of local cutaneous inputs, the long flexor acting on the thumb may contribute more to its proprioceptive acuity than the long finger flexors contribute to acuity at the fingers.

Adolescent↗

PubMed1995

Detection of movements imposed on human hip, knee, ankle and toe joints.

1. The angular displacements necessary for 70% correct detection were determined in normal subjects at the hip, knee and ankle joints, and the interphalangeal joint of the big toe. Angular velocities between 0.1 and 50 deg s-1 were tested. The hip and knee joints were tested in slight flexion and the ankle and toe joints were tested in the mid-range of the normal excursion. The joints were carefully supported for testing and the muscles acting at the joints were relaxed. 2. When detection thresholds and velocities were assessed in terms of angular displacements and angular velocities, proprioceptive performances at the hip, knee and ankle joints were superior to that at the toe joint. 3. When detection levels and displacement velocities were expressed in terms of linear displacements and velocities at the tip of the extended toe for all four joints, instead of in angular terms, the ankle gave the best performance and the hip and knee the worst. 4. The detection level and velocity data were expressed also in terms of proportional changes in the fascicle lengths of muscles operating these joints. Analysis in these terms showed that performance was similar at the hip, knee and ankle joints, but that performance for the toe was much poorer than for the other joints. 5. These results for the hip, knee and ankle are similar to those previously measured for the elbow and distal interphlangeal joint of the finger, and are consistent with the theory that muscle fascicle length is the variable of significance to the central nervous system. However, the proprioceptive performance at the big toe is notably poorer than all other joints studied and analysed in terms of this variable.

Adult↗

PubMed1995

Perception of movement at the human ankle: effects of leg position.

1. Recent studies show that subjects perceive smaller ankle movements when they are upright in the standing position than when they are seated. To examine this improvement, the ability to perceive ankle movements was tested in five positions of body, knee and ankle. Subjects reported the direction of slow ramp movements of the ankles. 2. The threshold for perceiving ankle movements was unchanged when only one ankle was moved rather than both together. When seated with the knees bent and ankles slightly plantarflexed, subjects perceived movements of 0.65 deg at 0.05 deg s-1. However, when upright or when seated with their knees and ankles in the standing position, subjects perceived movements that were one-third of this size. 3. These findings show that the knee and ankle positions, rather than being upright, explain the better performance in the standing position. During standing, knee extension and ankle dorsiflexion stretch the calf muscles. Thus, enhanced input from intramuscular stretch receptors appears responsible for the better performance.

Adult↗

PubMed1994

The relationship between surface contour and vertebral body measures of upper spine curvature.

STUDY DESIGN: In this study, parameters of sagittal cervical posture obtained from surface markers and from vertebral body locations were compared. OBJECTIVES: Several postural parameters were examined to establish the degree to which surface measures of cervical alignment reflect the underlying vertebral body alignment. SUMMARY OF BACKGROUND DATA: Previous studies of the relation between surface and vertebral alignment in the thoracic and lumbar regions have shown conflicting results. Some data suggest a connection between surface cervical posture and head and neck pain, but the relation between surface and vertebral posture in the cervical region has not been reported. METHODS: Lateral view radiographs of 24 healthy volunteers were used to give the surface alignment of skin markers and the locations of the geometric centers of vertebral bodies. Three angles describing sagittal alignment were investigated: 1) forward inclination of C2 relative to C7 (cervical inclination); 2) cervicothoracic kyphosis; and 3) cervical lordosis. RESULTS: A strong relationship between surface and vertebral data was not established. Two factors were identified as contributing to the observed differences: length of spinous processes and depth of soft tissue overlying the spinous processes at each spinal level. CONCLUSIONS: The assumption that the surface curve is the same as the vertebral curve is not supported by these results, suggesting caution is needed in inferring vertebral alignment from observed surface contours.

Adult↗

PubMed1994

Rotation: a valid premanipulative dizziness test? Does it predict safe manipulation?

OBJECTIVE: The purpose of this study was to investigate the validity of cervical spine rotation as a test of patency of the vertebral arteries (VAs) and the internal carotid arteries (ICAs). DESIGN: A descriptive study was undertaken. SETTING: Testing was carried out in a private clinical vascular unit attached to a large Sydney public hospital. PARTICIPANTS: Twenty healthy volunteers, both male and female, who were free of risk factors commonly associated with vascular disease, participated in the study. INTERVENTIONS AND MAIN OUTCOME MEASURES: An AutoSector 5 Duplex Doppler ultrasound instrument was used to record mean and peak frequency of blood flow (a measure of blood velocity) in the right and left VAs and ICAs in the cervical spine positions of neutral, 45 degrees contralateral rotation and full range contralateral rotation. To determine general hemodynamic stability, blood pressure and heart rate were recorded pre- and posttest, as well as in all tested positions. RESULTS: There was a significant trend for blood velocity to increase in 45 degrees contralateral rotation and to decrease in full rotation (p < .01). This trend was not consistent across vessels. Blood velocity decreased with rotation from neutral head position in the right VA, and continued to increase throughout rotation in the right ICA. CONCLUSION: It appears that sustained rotation influences blood velocity in the extracranial vessels. This may have relevance in patients with abnormal blood flow who are candidates for cervical manipulation.

Adult↗