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Biomedical subjects

P A Ballard

Publications and source records attributed to P A Ballard.

9 recordsLinked to original sources
PubMed1998

Prevalence of osteoporosis and related risk factors in UK women in the seventh decade: osteoporosis case finding by clinical referral criteria or predictive model?

The objectives of the study were: to determine the prevalence of osteoporosis in women in their seventh decade; to determine the number of women who conformed to at least one of the current East Yorkshire Clinical Referral Criteria for Osteoporosis; and to determine the sensitivity and specificity of these referral criteria in the diagnosis of osteoporosis and to compare this with the receiver operating characteristic (ROC) curve of a logistic regression model incorporating variables that were significantly associated with the risk of osteoporosis. An observational study was carried out at the Centre for Metabolic Bone Disease, Hull Royal Infirmary, on women in their seventh decade from three general practices. Densitometric assessment of lumbar spine and femoral neck was carried out using dual-energy X-ray absorptiometry (DXA) and a detailed medical history taken. The main outcome measures were prevalence of osteoporosis in women in their seventh decade and efficacy of agreed clinical referral criteria at osteoporosis case finding. Of 823 Caucasian women who underwent DXA, 24% proved to have osteoporosis at hip, spine or both according to WHO criteria. A further 49% had osteopenia detected at hip, spine or both. At least one of the referral criteria was present in 47% of the women assessed. The sensitivity of the clinical referral criteria for detection of osteoporosis was 58% with a corresponding specificity of 60%. This point lies below the ROC curve (area under fitted curve, Az = 0.73) of a logistic regression model incorporating weight, age at menopause and current use of hormone replacement therapy. In conclusion, osteoporosis according to WHO criteria was found in almost 25% of women in their seventh decade. A simple logistic regression model provided a more sensitive method of osteoporosis case finding than the selective screening component of the clinical referral criteria employed in our practice.

Absorptiometry, Photon↗
PubMed1997

Maximising the cost effectiveness of BMD referral for DXA using ultrasound as a selective population pre-screen.

Bone mineral density (BMD) referral for dual energy X-ray absorptiometry (DXA) is generally based upon agreed clinical referral criteria (CRC). The aim of this study was to determine whether ultrasound measurements of Broadband UI-trasound Attenuation (BUA) and velocity (VOS) provide a superior selective pre-screen referral method for BMD assessment by DXA. 107 women aged 60-69 years (64.2 +/- 2.8) had BMD measurements at lumbar spine and right femoral neck along with ultrasound BUA and VOS measurements of the left calcaneus. Each subject completed an extensive clinical and social questionnaire to ascertain those who would have met one or more of the five general clinical referral criteria adopted by our Centre. Each subject was classified by DXA using the WHO criteria as normal, osteopenic or osteoporotic at lumbar spine or femoral neck. The cost per osteoporotic subject correctly identified was calculated. As a reference, based upon DXA measurements alone on all 107 subjects, the cost per osteoporotic subject identified would be Ponds 185. If subjects had been referred using the clinical referral criteria the cost is Ponds 171. For assessment of referral by BUA or VOS, an additional charge for ultrasound measurement of all subjects was incorporated. At a BUA of 60 dB MHz-1 the cost per osteoporotic subject is Ponds 107. Ultrasound velocity or a combination of BUA or VOS with clinical referral criteria did not provide a significantly reduced cost than the current clinical referral criteria alone. This study has demonstrated that BUA provides an improved referral procedure to that currently achieved with clinical referral criteria and supports the concept of BUA being used as a selective pre-screen for DXA in 7th decade subjects.

Absorptiometry, Photon↗
PubMed1988

High-voltage electrical injury: acute pathophysiology.

A reproducible high-voltage electrical injury model was established in the primate using a new approach to energy administration, measurement instrumentation, and data acquisition. Patterns of current repartition and temperature generation were examined in 24 primates. The predominant current load was carried in muscle, which is the tissue group occupying the largest cross-sectional area. Highest temperature values observed were in muscles of small cross-sectional diameter and in tissues of high inherent resistance. Surgeons should be aware of the principles and the pattern of current distribution when performing early debridement and/or definitive coverage procedures.

Animals↗
PubMed1988

High-voltage electrical injury: chronic wound evolution.

A chronic electrical burn model employing documentary and diagnostic techniques was designed in the primate for investigating wound evolution up to 10 days after injury. A standardized 40-kJ, 3500-V, 4.2-A, 2.5-s bilateral, symmetrical upper extremity electrical injury was performed. Gross observation studies documented tissue injury extending more proximally on the deep surfaces of individual muscles and between muscle layers. Specific regions, or "choke" points, in the forearm exist in which decreased cross-sectional areas and highly resistant tissue composition resulted in increased heat production and more severe tissue damage. Muscle injury was analyzed using light microscopy, revealing patchy cellular necrosis intermixed with viable cells. Digital subtraction angiography demonstrated segmental narrowing and "pruning" of large vascular trunks with a significant decrease in nutrient vessels in affected areas. Ulnar nerve conduction studies showed loss of conduction proximal to the cubital fossa with no recovery. Although characteristic patterns of injury were documented in skin, muscle, vessels, and nerves, no experimental evidence was found for progressive necrosis.

Angiography↗
PubMed1985

Permanent human parkinsonism due to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP): seven cases.

Seven patients developed chronic and severe parkinsonism after repeatedly injecting 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intravenously. Levodopa and bromocriptine controlled the symptoms; however, within months, five of the seven patients experienced dyskinesias or on-off fluctuations. Therefore, neither prolonged levodopa treatment nor progressive disease was necessary for on-off phenomena. Because the neurotoxic effects of MPTP seem limited to the substantia nigra, damage to this system alone may produce all the motor features of Parkinson's disease. MPTP differs from other neurotoxins in that it consistently produces a pure parkinsonian state.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1984

Experimental electrical burns: low voltage.

Low-voltage electrical burns were studied in 25 pigs submitted to bilateral thigh burns using 500 volts AC for 10 seconds. In a group of 6 animals, the wounds were observed and histologic specimens obtained at different intervals during the first week. The burn measured approximately 4 cm in diameter and extended through two muscle layers. This tissue underwent further necrosis during the first 48 hours. After 2 days there was no further necrosis. In a second group, the wounds were debrided and covered with either a split-thickness skin graft or a rectus abdominis musculocutaneous flap. All wounds with flap coverage healed primarily and there was no deep necrosis. From our findings we conclude that debridement and definitive closure can safely be performed 2 days after low-voltage electrical burns.

Animals↗
PubMedDate not supplied

The natural history of osteoporosis.

Osteoporosis remains a formidable challenge to medicine. A greater understanding of the variables that influence bone mineralization will allow the development of strategies to determine those at risk of developing osteoporosis. Advances in the management of this disease will probably come from prevention and selective screening.

Adolescent↗