Biomedical subjects

J M McMeeken

Publications and source records attributed to J M McMeeken.

16 recordsLinked to original sources

PubMed2004

The relationship between EMG and change in thickness of transversus abdominis.

OBJECTIVE: To investigate the relationship between changes in thickness and EMG activity in the transversus abdominis muscle of healthy subjects and the reliability of ultrasound measurements using different modes and transducers. DESIGN: Convenience sampling. BACKGROUND: Chronic low back pain is associated with transversus abdominis dysfunction but EMG studies of this muscle are restricted to invasive techniques. Since the thickness of transversus abdominis changes with activity, such changes measured from ultrasound images might provide insight into this muscle's function non-invasively. In addition, little is known about the comparability of ultrasound measurements from different modes and transducers, nor the reliability of transversus abdominis measurements. METHODS: In 9 healthy subjects (aged 29-52 years, four male) transversus abdominis was studied at rest and during activity (5-80% max) with simultaneous EMG and ultrasound (M mode, 5 MHz curvilinear transducer) measurements. Intra-rater reliability for thickness measurements was studied on 13 subjects using 7.5 MHz linear and 5 MHz curvilinear transducers in B and M modes. RESULTS: Muscle thickness changes correlated well with EMG activity (P < 0.001, R2 = 0.87) and there were no significant differences between subjects (P > 0.05). Using 7.5 MHz head, the ICC for B mode was 0.989 and for M mode was 0.981 for between days reliability. The ICC for between transducer reliability was 0.817. CONCLUSIONS: Changes in thickness of transversus abdominis can be used to indicate changes in the electrical activity in this muscle. RELEVANCE: Ultrasound scanning can be used in the clinical setting to provide objective information about transversus abdominis function.

Abdominal Muscles↗

PubMed2002

Quantitative ultrasound assessment of acute bone loss following spinal cord injury: a longitudinal pilot study.

Spinal cord injury (SCI) results in substantial and rapid osteoporosis. Given its rapid onset, assessment of bone changes in the early stages (first 6 months) following SCI is important. This is particularly pertinent if intervention is to be implemented. Quantitative ultrasound (QUS) represents a potential assessment tool for the evaluation of skeletal changes in the early stages following SCI. This longitudinal pilot study assessed changes in QUS measures of calcaneal broadband ultrasound attenuation (BUA) and speed of sound (SOS) in 15 male subjects (age 23.9+/-7.3 years) over a 6-week period. Their mean time since SCI was 110.3+/-34.5 days. Also assessed were bone mineral density of the calcaneus (BMDc) and proximal tibia (BMDt) using dual-energy X-ray absorptiometry (DXA). Confirming the rapid onset of bone loss following SCI, BMDc and BMDt decreased by 7.5+/-3.0% ( p<0.001) and 5.3+/-4.2% ( p<0.001), respectively. QUS was sensitive to these changes. BUA decreased by 8.5+/-6.9% ( p<0.001), whilst SOS decreased by 1.5+/- 1.3% ( p<0.001). Suggesting an influence of the material properties of bone on BUA, BUA was correlated with BMDc at both the initial ( r = 0.68, p<0.01) and final ( r = 0.62, p<0.01) assessments. There were no significant correlations in the magnitude of change over the 6-week assessment period between any of the skeletal measures (all p>0.05). This suggests that skeletal qualities other than material properties also influence QUS measures. Overall, this study confirmed the rapid onset of bone loss following SCI and showed QUS to be a useful portable measure of acute bone changes. This may allow assessment of bone loss and the efficacy of intervention on this loss in the early stages following injury, a period where traditional axial DXA assessment is limited by practical constraints.

Absorptiometry, Photon↗

PubMed2002

The position of the spine in the recovery position--an experimental comparison between the lateral recovery position and the modified HAINES position.

UNLABELLED: The lateral recovery position is widely used for the positioning of unconscious patients. Ideally, in the setting of trauma it is avoided because of concerns about spinal cord injury. However, unconscious individuals with unsuspected trauma or trauma victims attended by partially trained first-aiders may be placed in the recovery position, potentially endangering the cord. Excessive movement of the spine in the recovery position may increase the risk of spinal cord injury in these situations. A new recovery position, termed the modified HAINES position, is described and the position of the spine in this position is compared with the lateral recovery position. HYPOTHESIS: That the modified HAINES position results in less distortion of the position of the spine than the lateral recovery position. METHODS: Thirty-eight healthy volunteers were imaged in the two different positions. Measurements of rotation, flexion and lateral flexion of the cervical and thoraco-lumbar spine were made. Two tailed paired t-tests were employed to compare measurements of the two positions and a McNemar test was used to compare the subjects' subjective experiences. RESULTS: The modified HAINES position resulted in 13.0 degrees (99% CI: 7.5-18.5) less lateral flexion and 12.6 degrees (99% CI: 9.4-15.9) less extension of the cervical spine while the position of the thoraco-lumbar spine was similar in both positions. Nineteen of 28 subjects found the modified HAINES position more comfortable (not significant). CONCLUSION: The modified HAINES position results in a more neutral position of the spine making it preferable to the lateral recovery position in the management of patients when trauma may have occurred. Further research is required to ensure that the recovery positions in use today are the best possible.

Adolescent↗

PubMed2001

Low-intensity pulsed ultrasound stimulates a bone-forming response in UMR-106 cells.

Low-intensity (<100 mW/cm(2)) pulsed ultrasound (US) is an established therapy for fracture repair. In both animal and human trials, such US has been shown to facilitate fresh fracture repair and initiate healing in fractures with repair defects. However, the mechanism by which US achieves these outcomes is not clear. One possible mechanism is the direct stimulation of bone formation. To investigate this hypothesis, the current study investigated the mRNA response of isolated bone-forming cells (UMR-106 cells) to a single 20-min dose of low-intensity pulsed US. Using a novel US-cell coupling method, US was found to stimulate expression of the immediate-early response genes c-fos and COX-2 and elevate mRNA levels for the bone matrix proteins ALP and OC. These findings suggest that low-intensity pulsed US has a direct effect on bone formation. This may contribute to the beneficial effect of low-intensity pulsed US on fracture repair.

Alkaline Phosphatase↗

PubMed2001

The role of weightbearing in the clinical assessment of knee joint position sense.

Knee joint position sense was assessed by active tests with active limb matching responses in supine lying and in unilateral weightbearing (WB) stance using (re)positioning of the whole limb whilst focusing on the knee, and in supine lying using (re)positioning confined to the knee. Following five tests at approximately 45 degrees knee flexion in all three test conditions, position sense was found to be significantly more accurate and reliable following the WB procedure. Possible explanations are, first, that during WB the subjects were more able to assist identification of the test positions using cues obtained during movement of the knee to and from these positions. Second, a larger volume of proprioceptive afferent information may have been derived from sources outside the examined knee, and even outside the examined limb. Whilst WB joint position sense assessments are more functional, the obtained results may not characterise the capacity of the proprioceptors in and around the examined (knee) joint. Since the WB and NWB results were not correlated, one procedure cannot be used to predict results from the others. Also, predominantly unilateral WB stance is often impractical for subjects with limited balance or WB pain.

Adult↗

PubMed2001

Skeletal effects of low-intensity pulsed ultrasound on the ovariectomized rodent.

Growing evidence supports low-intensity pulsed ultrasound (US) as an osteogenic mechanical stimulus. Its effects on isolated bone cells and on fractured bone are established. However, its effects on osteoporosis are not clear. This study examined US effects on ovariectomy (OVX) induced bone changes within the rodent hindlimb (distal femur and proximal tibia), and on normal bone in animals following sham-OVX. Animals were exposed to daily unilateral active-US and contralateral inactive-US for 12 weeks. Bone status was assessed using dual energy X-ray absorptiometry and histomorphometry. Ovariectomy resulted in significant bone changes. Low-intensity pulsed US did not influence these changes. These results suggest that the US dose introduced may not be a beneficial treatment for osteoporosis, and that intact bone may be less sensitive to US than fractured bone and isolated bone cells. This may relate to the biophysical mechanisms of action of US, US-bone interactions and tissue level processes taking place.

Absorptiometry, Photon↗

PubMed2001

Efficacy of low-intensity pulsed ultrasound in the prevention of osteoporosis following spinal cord injury.

Ultrasound (US), a high-frequency acoustic energy traveling in the form of a mechanical wave, represents a potential site-specific intervention for osteoporosis. Bone is a dynamic tissue that remodels in response to applied mechanical stimuli. As a form of mechanical stimulation, US is anticipated to produce a similar remodeling response. This theory is supported by growing in vitro and in vivo evidence demonstrating an osteogenic effect of pulsed-wave US at low spatial-averaged temporal-averaged intensities. The aim of this study was to investigate whether low-intensity pulsed US could prevent calcaneal osteoporosis in individuals following spinal cord injury (SCI). Fifteen patients with a 1-6 month history of SCI were recruited. Active US was introduced to one heel for 20 min/day, 5 days/week, over 6 weeks. The contralateral heel was simultaneously treated with inactive US. Patients were blind to which heel was being actively treated. Active US pulsed with a 10 microsec burst of 1.0 MHz sine waves repeating at 3.3 kHz. The spatial-averaged temporal-averaged intensity was set at 30 mW/cm(2). Bone status was assessed at baseline and following the intervention period by dual-energy X-ray absorptiometry and quantitative US. SCI resulted in significant bone loss. Bone mineral content decreased by 7.5 +/- 3.0% in inactive US-treated calcanei (p < 0.001). Broadband US attenuation and speed of sound decreased by 8.5 +/- 6.9% (p < 0.001) and 1.5 +/- 1.3% (p < 0.001), respectively. There were no differences between active and inactive US-treated calcanei for any skeletal measure (p > 0.05). These findings confirm the negative skeletal impact of SCI, and demonstrate that US at the dose and mode administered was not a beneficial intervention for SCI-induced osteoporosis. This latter finding may primarily relate to the inability of US to effectively penetrate the outer cortex of bone due to its acoustic properties.

Absorptiometry, Photon↗

PubMed2000

Acceleration of fresh fracture repair using the sonic accelerated fracture healing system (SAFHS): a review.

The Sonic Accelerated Fracture Healing System (SAFHS) is a relatively new fracture management tool which incorporates the application of a specifically modified diagnostic ultrasound unit to healing fractures with the intention of accelerating repair. In an animal fracture model, this device has been shown to accelerate the rate of biomechanical healing by a factor of 1.4-1.6. In two randomized, controlled trials in humans, the same unit has been shown to reduce the time frame of clinical and radiographic healing by 38%. In the two fracture regions investigated, tibial diaphysis and distal radius, this represented a 58 day and 37 day reduction in healing time, respectively. Despite its effect on the entire process of fresh fracture repair, the effect of the SAFHS on the individual stages and processes involved has not been established. This paper reviews these stages and processes, and discusses the clinical and practical implications of the effect of the SAFHS on fracture repair and the need for further research into this modality.

Animals↗

PubMed2000

Age-related differences in the time course of capsaicin-induced hyperalgesia.

The effect of age on hyperalgesia, one of the most common signs of injury, has not been previously examined in humans. A psychophysical study was conducted in 10 young (26.9+/-4.6 years) and 10 older (79. 0+/-5.7 years) healthy volunteers to investigate the effect of age on the development of hyperalgesia induced by topical application of capsaicin (0.1 ml, 5 mg/ml). The capsaicin patch (diameter 2 cm) was applied for 1 h. The intensity of capsaicin-induced spontaneous sensation, mechanical pain threshold, area of flare, heat and punctate hyperalgesia were measured hourly for 3 h after the application. Older adults took a longer period to report first pain. There was no age effect on the magnitude of spontaneous sensation, flare size and area of heat hyperalgesia. The area of heat hyperalgesia rapidly decreased over time in both age groups. In marked contrast, the area of punctate hyperalgesia and associated reduction in the mechanical pain threshold were maintained in older adults over the entire 3 h test period, but resolved rapidly in young adults. We conclude that, given the same intensity of noxious stimulation, older adults display a similar magnitude of hyperalgesia as younger persons. However, once initiated, punctate hyperalgesia appears to resolve more slowly in older people. This finding may indicate age differences in the plasticity of spinal cord neurons following an acute injury.

Administration, Topical↗

PubMed2000

Increased movement pain in osteoarthritis of the hands is associated with A beta-mediated cutaneous mechanical sensitivity.

The relationship between joint pain and hyperalgesia has been explored in animal models of articular inflammation, but is yet to be shown in the most common rheumatologic condition: osteoarthritis. In this study, cutaneous thermal and mechanical pain thresholds were measured over the thumb of patients with osteoarthritis of the hands. In symptomatic patients, pain was manipulated through resisted active movement of the thumb. Provocation of movement pain (MP) was associated with a sustained fall in mechanical pain thresholds. Thermal pain thresholds remained stable during increases in joint pain. Increased mechanical sensitivity after exacerbation of MP was alleviated by A beta fiber blockade. It appears that superficial tenderness over the osteoarthritic thumb fluctuates with pain arising from movement of the joint. It is concluded that dorsal horn mechanisms contribute to MP-related hyperalgesia in osteoarthritis of the hands.

Journal Article↗

PubMed2000

A technique for restraining rodents during hindlimb interventions.

Recently interest has grown in the skeletal effects of external electrophysical modalities. To introduce these modalities into the rodent hindlimb, restraining the animals is often necessary. This report describes a novel restraint device that was highly successful when used on 10 Sprague-Dawley rats for 20 min daily for 6 days each week over a period of 12 weeks. The restrained animals gained less weight than did 10 cage control animals, suggesting that animals experienced stress. However, this weight loss was significant (p < 0.05) only during the first six weeks, suggesting a degree of acclimatization. Restraint had no observable effect on measures of bone mineral content of the hindlimb. The restraint device we developed restrained animals without the need for anesthetics, enabling our device to be used in future studies investigating the skeletal effect of external electrophysical modalities on the rodent hindlimb.

Animal Husbandry↗

PubMed1998

Aftereffects of resisted muscle contractions on the accuracy of joint position sense in elite male athletes.

OBJECTIVE: To examine the effects of quadriceps and hamstring muscle strength testing on the results of subsequent knee joint position sense tests. DESIGN: A case-control study of 40 elite male athletes divided equally into two groups, experimental and control. METHODS: Both groups underwent position sense tests of both knees, with eyes closed, with isometric maintenance of the knee in each test position, return of the limb to the starting position, then active replication of the perceived test position using the same limb. In the experimental group, joint sense testing commenced 5 to 25 min after strength testing of quadriceps and hamstring muscle strength in both legs using maximum isokinetic contractions at plateau speeds of 60 degrees/sec and 120 degrees/sec. The control group did not undergo pretest muscle strength testing. RESULTS: The difference in the mean absolute (signless) and relative (signed) position sense errors between the experimental and control groups was 0.8 degrees and 1.4 degrees, respectively. The difference between the standard deviation of the relative errors was 1.2 degrees. These results were not statistically significant (analysis of variance p = .24, .12, and .13, respectively). CONCLUSION: In elite male athletes knee joint position sense is unaffected by nonfatiguing strength tests conducted 5 to 25 min before position sense testing.

Adult↗

PubMed1990

Effects of selective blood and tissue heating on blood flow in the dog hindlimb.

This study investigated the effects of independent and combined heating of blood and tissue to 40-44 degrees C on femoral blood flow in the hindlimb of the anaesthetized dog. An increase in arterial blood temperature by means of an extracorporeal circuit increased femoral vascular resistance. An increase in limb tissue temperature, induced by external hot packs, decreased femoral vascular resistance. These responses occurred both before and after sympathetic blockade. Neither blood heating nor tissue heating affected the hyperaemic response to exercise. When blood and tissue heating were combined, femoral vascular resistance remained unaffected. We conclude that changes in blood temperature do not contribute to the hyperaemic effect of limb warming and that exercise combined with limb warming is no more effective as a therapeutic tool for promoting limb flow than exercise alone.

Animals↗

PubMed1990

Effects of microwave irradiation on blood flow in the dog hindlimb.

Physiotherapeutic doses of microwave irradiation to the hindlimb of the anaesthetized dog increased the temperature in the underlying skin and muscle by 5-6 degrees C and, after a latency of 2-8 min, heart rate, blood pressure and femoral conductance all increased. The conductance increase was predominantly in the paw. At this time plasma catecholamine levels were elevated above resting values. At the conclusion of irradiation, heart rate and blood pressure rapidly returned to basal levels, but there was a sustained increase in femoral conductance which was mainly in the leg. The results are discussed in terms of the likely mechanisms underlying the effects of microwave irradiation on limb blood flow and compared with those obtained with direct heating of arterial blood and limb tissue in the accompanying paper.

Animals↗

PubMedDate not supplied

How should an unconscious person with a suspected neck injury be positioned?

INTRODUCTION: Awareness of the risk of spinal-cord damage in moving an unconscious person with a suspected neck injury into the "lateral recovery position," coupled with the even greater risk of inadequate airway management if the person is not moved, has resulted in a suggested modification to the lateral recovery position for use in this circumstance. HYPOTHESIS: It is proposed that the modification to the lateral recovery position reduces movement of the neck. In this modification, one of the patient's arms is raised above the head (in full abduction) to support the head and neck. The position is called the "HAINES modified recovery position." HAINES is an acronym for High Arm IN Endangered Spine. METHODS: Neck movements in two healthy volunteers were measured by the use of video-image analysis and radiographic studies when the volunteers were rolled from the supine position to both the lateral recovery position and the HAINES modified recovery position. RESULTS: For both subjects, the total degree of lateral flexion of the cervical spine in the HAINES modified recovery position was less than half of that measured during use of the lateral recovery position (while an open airway was maintained in each). CONCLUSION: An unconscious person with a suspected neck injury should be positioned in the HAINES modified recovery position. There is less neck movement (and less degree of lateral angulation) than when the lateral recovery position is used, and, therefore, HAINES use carries less risk of spinal-cord damage.

Adult↗

PubMedDate not supplied

When is a change a genuine change? A clinically meaningful interpretation of grip strength measurements in healthy and disabled women.

The aim of this study was twofold: 1) to use estimates of random and systematic error to ascertain the test-retest reliability of grip strength measurements obtained with the Jamar hand dynamometer in healthy and disabled women, and 2) to determine the size of the change required to detect a genuine change in grip strength for accurate and meaningful clinical interpretation. Previous research has shown grip strength measurements obtained with a Jamar hand dynamometer from healthy and disabled subjects on different occasions to be reliable. However, the test-retest reliability has been based on correlation coefficients rather than on the actual size of the test-retest differences required to detect a genuine change in grip. The test-retest reliability of maximum grip strength measurements in 32 healthy women and painfree grip in 10 disabled women with nonspecific regional pain (NSRP) was determined. Reliability, based on estimates of systematic and random error, was high in both subject groups. There was no statistically significant systematic error between tests. Test-retest measurement error was +/-5.7 kg (12.5 lb) and +/-5.9 kg (13.0 lb) in healthy and disabled subjects, respectively, 95% of the time. In this population of healthy women and women with NSRP, any change in grip of less than 6 kg (13.2 lb) could have occurred by chance. The results of our study suggest that a change of more than 6 kg (13.2 lb) is necessary to detect a genuine change in grip strength 95% of the time.

Adult↗