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J D Wark

Publications and source records attributed to J D Wark.

At least 37 records · Page 2Linked to original sources
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

Does childhood and adolescence provide a unique opportunity for exercise to strengthen the skeleton?

Osteoporosis is a major, and increasing, public health problem. In this review we examine the evidence that childhood physical activity is an important determinant of bone mineral in adult years, and as such, may help to prevent osteoporosis. Animal studies provide incontrovertible evidence that growing bone has a greater capacity to add new bone to the skeleton than does adult bone. Observational studies in children undertaking routine physical activity and cross-sectional athlete studies in young sportspeople both reveal that activity is positively associated with bone mineral density (BMD). Longitudinal studies in pre- and peripubertal gymnasts reveal BMD gains far in excess of those that can be achieved in adulthood. However, such studies permit only limited conclusions as they contain the potential for selection bias and can be confounded by other determinants of bone mineral (e.g. dietary and lifestyle factors). Thus, research comparing inter-individual playing-to-nonplaying arm differences in bone mineral (e.g., in racquet sports) have proven to be extremely useful. These studies suggest that the BMD differences are clearly greater when bone is subjected to mechanical loading prior to the end of puberty and longitudinal growth of the body (in women, before menarche) rather than after it. Tanner stage II and III appears to be the maturational stage when the association between exercise and BMD becomes manifest in most adolescents. Do conclusions drawn from athlete studies apply to the general population? Randomised intervention studies of physical activity and bone mineral accrual in normal children confirm that childhood activity is strongly associated with bone mineral accrual. Furthermore, some retired athlete studies and a detraining study suggest that adolescent bone gain may, at least partly, persist despite reduced adult physical activity. Mechanisms that may underlie the association between childhood physical activity and bone mineral accrual are outlined. Thus, it appears that physical activity during the most active period of maturity (with respect to longitudinal growth of the body) plays a vital role in optimising peak bone mass and that benefits may extend into adulthood.

Adult↗
PubMed2000

Studies of surgical outcome after patellar tendinopathy: clinical significance of methodological deficiencies and guidelines for future studies. Victorian Institute of Sport Tendon Study Group.

Patellar tendinopathy is often treated surgically after failure of conservative treatment but clinical experience suggests that results are not uniformly excellent. The aim of this review was to (i) identify the different surgical techniques that have been reported and compare their success rates, and (ii) critically assess the methodology of studies that have reported surgical outcomes. Twenty-three papers and two abstracts were included in the review. Surgical procedures were categorized and outcomes summarized. Using ten criteria, an overall methodology score was derived for each paper. Criteria for which scores were generally low (indicating methodological deficiency) concerned the type of study, subject selection process and outcome measures. We found a negative correlation between papers' reported success rates and overall methodology scores (r= -0.57, P<0.01). There was a positive correlation between year of publication and overall methodology score (r=0.68, P<0.001). We conclude that study methodology may influence reported surgical outcome. We suggest practical guidelines for improving study design in this area of clinical research, as improved study design would provide clinicians with a more rigorous evidence-base for treating patients who have recalcitrant patellar tendinopathy.

Bias↗
PubMed2000

Urine calcium and urine sodium concentrations are not related, after adjustment for urine magnesium.

BACKGROUND AND OBJECTIVES: Urine calcium correlates with urine sodium. The aims of this study were to investigate whether the urine sodium-calcium relationship persists into old age and whether it holds after adjustment for urine magnesium. DESIGN: Cross-sectional descriptive analysis. PATIENTS: Residents of two aged care institutions (median age 84 years) who were not taking diuretics, calcium or vitamin D supplements. MEASUREMENTS: Early morning urine calcium, sodium and magnesium, plasma creatinine and serum 25-hydroxyvitamin D and parathyroid hormone. RESULTS: Urine calcium correlated with urine sodium (r = 0.29, P < 0.01) and with urine magnesium (r = 0.56, P < 0.001). After adjustment for urine magnesium, the relationship between urine sodium and urine calcium was no longer significant. Forty-five percent of the interindividual variation in urine calcium was explained by a linear model on the basis of urine magnesium and plasma creatinine. CONCLUSION: The data indicate that a correlation between urine sodium and calcium persists in very old age. However, this correlation no longer holds after adjustment for urine magnesium. Further studies examining urine calcium excretion should also consider urine magnesium.

25-Hydroxyvitamin D 2↗
PubMed2000

Determination of age at death using combined morphology and histology of the femur.

Bone is characterised by age-related morphological and histological changes. We have previously established an automated method of recording bone morphometry and histology from entire transverse sections of cortical bone. Our aim was to determine whether data acquired using this automated system were useful in the prediction of age. Ninety-six specimens of human femoral middiaphysis were studied from subjects aged 21-92 y. Equations predicting specimen age were constructed using macroscopic data (total subperiosteal area (TSPA), periosteal perimeter (PP), endosteal perimeter (EP), cortical bone area (CA) and moments of area) and microscopic data (the number, size and diversity of pores and intracortical porosity) together with sex, height and weight. Both TSPA and PP were independent predictors of age but the number of pores was not a significant predictor of age in any equation. The age predicted by these equations was inaccurate by more than 8 y in over half the subjects. We conclude that we could not predict age at a clinically acceptable level using data from our automated system. This most likely reflects an insensitivity to regional age-related changes in bone histology because we recorded data from each entire cortex. Automated bone measurement according to cortical region might be more useful in the prediction of age. The inclusion of TSPA together with PP as independent predictors of age raises the possibility that a future measure of periosteal shape at the femoral diaphysis could also be helpful in the prediction of age. The accuracy reached with the relatively simple methods described here is sufficient to encourage the development of image-analysis systems for the automatic detection of more complex features.

Adult↗
PubMed2000

Compressive and shear force generated in the lumbar spine of female rowers.

Rowers have and accrue greater lumbar spine bone mineral density (BMD) associated with mechanical loading produced during rowing. The aim of this study was to estimate the mechanical loading generated at the lumbar spine (LS) that is apparently providing an osteogenic benefit. The cohort comprised 14 female rowers (average age: 19.7yrs; height: 170.9 cm, weight: 59.5 kg) and 14 female matched controls (average age: 20.9 m yrs; height: 167.5 cm; weight: 58.1 kg). BMD was assessed using the Hologic QDR 2000+ bone densitometer, indicating higher lumbar spine BMD in the rowers compared to the control subjects (1,069 +/- 0.1 vs. 1,027 +/- 0.1 g/cm2). No significant difference existed for BMD at any other site. All rowers performed a six-minute simulated race on a Concept II rowing ergometer. Mechanical loading generated at the lumbar spine during this task was assessed using a two-dimensional model of the spine, enabling the calculation of the compressive and shear forces at L4/L5. The shear force was the joint reaction force perpendicular to the spine at the L4/L5 joint. Peak compressive and shear force at the lumbar spine of the rowers were 2,694 +/- 609 (N) and 660 +/- 117 (N), respectively. Peak compressive force at the LS relative to body weight was 4.6 times body weight. The literature would suggest that forces of this magnitude, generated at the LS during maximal rowing, may be contributing to the site specific higher LS BMD found in the rowers.

Adolescent↗
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↗
PubMed1999

The impact of intense training on endogenous estrogen and progesterone concentrations and bone mineral acquisition in adolescent rowers.

The effect of 18 months of training on the ovarian hormone concentrations and bone mineral density (BMD) accrual was assessed longitudinally in 14 adolescent rowers and 10 matched controls, aged 14-15 years. Ovarian hormone levels were assessed by urinary estrone glucuronide (E(1)G) and pregnanediol glucuronide (PdG) excretion rates, classifying the menstrual cycles as ovulatory or anovulatory. Total body (TB), total proximal femur (PF), femoral neck (FN) and lumbar spine (LS) (L2-4) bone mass were measured at baseline and 18 months using dual-energy X-ray densitometry. Results were expressed as bone mineral content (BMC), BMD and bone mineral apparent density (BMAD). Five rowers had anovulatory menstrual cycles compared with zero prevalence for the control subjects. Baseline TB BMD was significantly higher in the ovulatory rowers, with PF BMD, FN BMD and LS BMD similar for all groups. At completion, the LS bone accrual of the ovulatory rowers was significantly greater (BMC 8.1%, BMD 6.2%, BMAD 6.2%) than that of the anovulatory rowers (BMC 1.1%, BMD 3.9%, BMAD 1.6%) and ovulatory controls (BMC 0.5%, BMD 1.1%, BMAD 1.1%). No difference in TB, PF or FN bone accrual was observed among groups. This study demonstrated an osteogenic response to mechanical loading, with the rowers accruing greater bone mass than the controls at the lumbar spine. However, the exercise-induced osteogenic benefits were less when rowing training was associated with low estrogen and progesterone metabolite excretion.

Adolescent↗
PubMed1999

Correlation of ultrasound and magnetic resonance imaging with clinical outcome after patellar tenotomy: prospective and retrospective studies. Victorian Institute of Sport Tendon Study Group.

OBJECTIVE: To report the appearances of ultrasound (US) and magnetic resonance imaging (MRI) before and after surgery for chronic patellar tendinopathy and to correlate postoperative appearances with clinical outcome. DESIGN: A 12-month prospective longitudinal study and a retrospective study, each part using different patients. Prospective study included clinical assessment, ultrasound, and MRI all performed before and 12 months after surgery. Retrospective study included ultrasound and clinical assessment only (i.e., no MRI) 24 to 67 months after surgery. SETTING: Institutional athlete study group in Australia (Victorian Institute of Sport Tendon Study Group). PATIENTS: In the prospective study, 13 patients (all male; 15 tendons) who underwent patellar tenotomy; in the retrospective study, 17 different patients (18 tendons) who had undergone identical surgery. MAIN OUTCOME MEASURES: Ultrasound and MRI appearances and clinical assessment at baseline and 12 months after surgery (prospective study). Ultrasound appearance and clinical assessment 24 to 67 months after surgery (retrospective study). Dimensions of abnormal regions on imaging were measured. Clinical assessment included categorical rating and numerical Victorian Institute of Sport Assessment (VISA) score. RESULTS: In the prospective study, preoperative ultrasound and MRI appearances confirmed the clinical diagnosis of patellar tendinopathy. Postoperative ultrasound and MRI also revealed abnormalities consistent with patellar tendinopathy. Despite this, 11 of 15 (73%) tendons were rated clinically as either good or excellent. Imaging modalities were unable to distinguish tendons rated as good or excellent from those rated poor at 12 months. In the retrospective study, ultrasound images revealed abnormalities despite full clinical recovery. There was no correlation between dimension of ultrasound abnormality and either VISA score or time since surgery. CONCLUSION: After open patellar tenotomy, MRI and ultrasound findings remain abnormal despite clinical recovery. Thus, clinicians ought to base postoperative management of patients undergoing patellar tenotomy on clinical grounds rather than imaging findings. At present, there appears to be no role for routine postoperative imaging of patients recovering slowly after patellar tenotomy. However, this is not to suggest that imaging cannot play a role in special circumstances.

Adolescent↗
PubMed1999

Risk factors for osteoporosis and fracture in patients attending rheumatology outpatient clinics.

BACKGROUND: Bone mineral density (BMD) using dual energy X-ray absorptiometry (DXA) scanning is the best predictor of osteoporotic fracture but may not be cost effective for all patient groups. Risk factors (RF) other than BMD may be useful for fracture prediction. AIM: To assess the prevalence of RF for osteoporosis (OP) and fracture in patients attending a public hospital rheumatology clinic and to document physician awareness of these RF. METHODS: Two hundred and twenty rheumatology outpatients completed a self-administered questionnaire pertaining to known RF for OP and fracture. Initiatives were documented by the treating rheumatologist. RESULTS: One hundred and fifty-four females and 66 males completed questionnaires: 57% had an inflammatory disorder and 32% had received significant glucocorticoid therapy. Forty-five (68%) males and 126 (82%) females had three or more RF for OP and fracture. Diagnosis of rheumatoid arthritis or connective tissue disorder (CTD) was the variable most significantly associated with increasing numbers of RF. Antiosteoporotic medication (AOM) use at assessment (64/219, 29.2%) was accounted for primarily by the use of hormone replacement therapy in females between 45-54 years. Prednisolone use predicted intervention in 103 (48%) patients. CONCLUSION: Many rheumatology outpatients have multiple RF for OP and fracture. Infrequent AOM use could be explained by inadequate awareness of high risk patients and the lack of an ideal long term agent. With restricted outpatient resources, the feasibility of identifying high risk patients for OP and fracture would increase if the hierarchical status of RF was better understood.

Adolescent↗
PubMed1999

Falls relate to vitamin D and parathyroid hormone in an Australian nursing home and hostel.

OBJECTIVES: To determine whether falling relates to serum levels of vitamin D and parathyroid hormone. DESIGN: A cross-sectional study with retrospective analysis. SETTING: An aged-care institution in Melbourne Australia. PARTICIPANTS: Ambulant nursing home and hostel residents (n = 83). MEASUREMENTS: Frequency of falling, frequency of going outdoors, use of cane or walker, age, sex, weight, type of accommodation, and duration of residence. Serum concentrations of 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and parathyroid hormone (PTH). Plasma concentrations of albumin, calcium, phosphate, and creatinine. Use of furosemide or non-benzodiazepine anticonvulsants. RESULTS: Median age of residents was 84 years. The cohort was vitamin D deficient with a median (interquartile range) 25-hydroxyvitamin D level of 27 (18-37) nmol/L (one-third the reference range median), P < .001. The median (interquartile range) PTH of 5.2 (3.8-7.7) pmol/L exceeded the reference range median, P < .001. Residents who fell (n = 33) had lower serum 25-hydroxyvitamin D levels than other residents (medians 22 vs 29 nmol/L, P = .02) and higher serum PTH levels (medians 6.2 vs 4.8 pmol/L, P < .01). Sixty residents lived in the hostel (72%), and 41 (49%) walked without any walking aid. In a multiple logistic regression for falling, higher serum PTH remained independently associated with falling, with an odds ratio (95% confidence interval) for falling of 5.6 (1.7-18.5) per unit of the natural logarithm of serum PTH. Other terms in the regression were hostel accommodation, odds ratio .04 (.01-.25), and ability to walk without aids, odds ratio .07 (.01-.37). CONCLUSIONS: In ambulant nursing home and hostel residents, residents who fall have lower serum 25-hydroxyvitamin D and higher serum parathyroid hormone levels than other residents. The association between falling and serum PTH persists after adjustment for other variables.

Accidental Falls↗
PubMed1999

Hip and ankle range of motion and hip muscle strength in young female ballet dancers and controls.

OBJECTIVES: To compare the hip and ankle range of motion and hip muscle strength in 8-11 year old novice female ballet dancers and controls. METHODS: Subjects were 77 dancers and 49 controls (mean (SD) age 9.6 (0.8) and 9.6 (0.7) years respectively). Supine right active hip external rotation (ER) and internal rotation (IR) were measured using an inclinometer. A turnout protractor was used to assess standing active turnout range. The measure of ER achieved from below the hip during turnout (non-hip ER) was calculated by subtracting hip ER range from turnout range, and hip ER:IR was derived by dividing ER range by IR range. Range of right weight bearing ankle dorsiflexion was measured in a standing lunge using two methods: the distance from the foot to the wall (in centimetres) and the angle of the shank to the vertical via an inclinometer (in degrees). Right calf muscle range was measured in weight bearing using an inclinometer. A manual muscle tester was used to assess right isometric hip flexor, internal rotator, external rotator, abductor, and adductor strength. RESULTS: Dancers had less ER (p<0.05) and IR (p<0.01) range than controls but greater ER:IR (p<0.01). Although there was no difference in turnout between groups, the dancers had greater non-hip ER. Dancers had greater range of ankle dorsiflexion than controls, measured in both centimetres (p<0.01) and degrees (p<0.05), but similar calf muscle range. After controlling for body weight, controls had stronger hip muscles than dancers except for hip abductor strength which was similar. Regression analyses disclosed a moderate relation between turnout and hip ER (r = 0.40). There were no significant correlations between range of motion and training years and weekly training hours. CONCLUSIONS: Longitudinal follow up will assist in determining whether or not hip and ankle range in young dancers is genetically fixed and unable to be improved with further balletic training.

Ankle Joint↗
PubMed1999

Prospective decrease in progesterone concentrations in female lightweight rowers during the competition season compared with the off season: a controlled study examining weight loss and intensive exercise.

The purpose of this study was to monitor ovarian hormone function response to intense exercise and body weight changes in female athletes. Ovarian hormone function was evaluated in 12 female lightweight rowers and 10 age-height-weight matched sedentary controls. Ovarian hormone function was assessed during consecutive competition season and off season, by measurement of peak and average alternative day overnight urinary oestrone glucuronide (E1G) and pregnanediol glucuronide (PdG) excretion. Competition season was associated with a 5.8 kg (9.3%) body weight loss in the lightweight rowers. Significantly lower competition season peak and average urinary excretion of PdG were found in the lightweight rowers compared with the controls. Lower competition season peak and average urinary excretion of E1G were also found in the lightweight rowers compared with the controls, but the difference did not reach significance. The number of rowing training hours was a significant determinant of peak PdG excretion in the rowers (R2 = 0.40; p<0.02). The seasonal suppression of PdG excretion was associated with degree of weight loss (R2 = 0.46; p<0.01). The competition related decrease in E1G and PdG excretion for the lightweight rowers was predominantly restored during the off season when exercise intensity and duration were decreased and body weight increased. These results showed a significant (p<0.05) reduction in progesterone metabolite excretion and a non-significant decrease in oestrone metabolite excretion associated with intensive competition season training loads and body weight reduction in female lightweight rowers.

Adolescent↗
PubMed1999

An automated analysis of intracortical porosity in human femoral bone across age.

The matrix of human cortical bone is arranged around a network of vascular spaces (hereafter referred to as "pores"). Our aim was to investigate age-related differences in human cortical porosity (total pore area divided by cortical bone area), pore size and number, and surface to volume ratios, while adjusting for sex, height, and weight. Ninety-six specimens of entire transverse sections of human femoral diaphysis, from subjects aged 21-92 years, were examined. We used our established automated image acquisition and analysis system which measures pores from entire sections of multiple specimens of bone. Over 400,000 pores were recorded. Results showed a greater porosity in older bone (p < 0.01) but marked variation in porosity for any given age. The cohort median, of the specimen medians, of pore cross-sectional area was 2050 microns 2. Older specimens did not have more pores than younger specimens but had a greater proportion of larger pores (p < 0.05) and greater intraspecimen variation in pore size (p < 0.001). The pore surface to bone matrix volume ratio was a median 2.3 mm2/mm3. This varied more than 4-fold between individuals but did not relate to age. No simple relationships were found between any of the measured parameters and either sex, height, or weight, even after adjustment for age. We conclude that the greater porosity in older specimens is due to greater pore size rather than a larger number of pores. Age, however, explains little of the inter-individual variation in the parameters studied.

Adult↗
PubMed1999

Response to parathyroidectomy at the axial and appendicular skeleton in renal patients.

AIM AND METHODS: We report increases in axial and appendicular bone density after parathyroidectomy in renal patients. Bone density was recorded pre-operatively and at 6 weeks, 6 months and 1 year post-operatively. We have previously reported that axial bone density increased dramatically at 6 weeks but that there were no early cohort increases at the appendicular skeleton [Stein et al. 1997]. RESULTS: We now report that at six months, bone density had continued to increase at the lumbar spine and femoral neck, with median respective 6 months increases over baseline of 1.3 (p < 0.01) and 0.7 (p < 0.01 ) Z-scores. Bone density then appeared to stabilize at the axial skeleton. At the appendicular skeleton increases were significant at the one year time point with median respective increases at the ultradistal radius and one third radius of 0.46 (p < 0.05) and 0.49 (p < 0.05) Z-scores. The different pattern of responses to parathyroidectomy between the axial and appendicular sites supports the concept that appendicular bone turnover is slower than axial bone turnover. Furthermore, at the appendicular skeleton, bone turnover appears similar between cortical and trabecular bone. CONCLUSION: In renal patients, bone density increases after parathyroidectomy at both the axial and appendicular skeleton. Axial increases are large and occur early. Appendicular increases occur at both cortical and trabecular sites but are slower than the axial changes.

Absorptiometry, Photon↗
PubMed1998

Genetic, common environment, and individual specific components of variance for bone mineral density in 10- to 26-year-old females: a twin study.

Lean mass and areal bone mineral density at the lumbar spine, femoral neck, and total forearm were measured in 215 volunteer female twin pairs (122 monozygotic, 93 dizygotic), aged 10-26 years, using dual energy X-ray absorptiometry. The study was conducted in Melbourne from 1990 to 1994. Under the classic twin model, there was evidence for a genetic component of variation in bone mineral density, adjusted for age or for age and lean mass, at all sites. Adjusting for lean mass almost halved the genetic variances in the adolescent years of peak growth, during which genetic variances peaked. Genetic variances were reduced in the late teenage years and increased in early adulthood. The latter may reflect gene-environment interactions or covariation. Importantly, there was evidence for environmental effects shared by twins on lumbar spine and femoral neck bone mineral density, even when adjusted for lean mass as well as age. These were greatest during the late teenage years, abated over the years when pairs started to live apart, and appear to be independent of lean mass during adolescence but not in early adulthood. In summary, the genetic and environmental etiology of bone mineral density is more complex than previously thought.

Absorptiometry, Photon↗
PubMed1998

Self-reported ballet classes undertaken at age 10-12 years and hip bone mineral density in later life.

The major effect of weightbearing exercise on adult bone mass may be exerted during childhood. We examined the relationship between reported hours of ballet classes per week undertaken as a child and adult bone mineral density (BMD) at the hip, spine, and forearm. We performed a retrospective cohort study in 99 female retired dancers (mean age 51 years, SD 14 years) and 99 normal controls, derived from a twin study, matched hierarchically for age, height, weight and menopausal status. Starting age of ballet was recalled and weekly hours of ballet as a child was self-reported on two occasions. BMD was measured using dualenergy X-ray absorptiometry and reported as a Z-score. Self-reported hours of ballet class undertaken per week at each age between 10 and 12 years was positively associated with a difference in BMD between dancers and controls at both the femoral neck site (beta = 0.73, p = 0.001) and the total hip site (beta = 0.55, p < 0.01). These associations were unaffected by adjustment for covariates including measures of adult activity (current physical activity, years of fulltime ballet), measures of menstrual disturbance (age of menarche, history of irregular menses), dietary history (calcium intake as a child, adolescent or adult) or lifestyle factors (lifetime smoking, lifetime alcohol). Although starting age of ballet was negatively associated with weight-adjusted within-pair hip BMD difference, it was no longer associated after adjustment for weekly hours of ballet. There was no relationship between hours of ballet undertaken as a child and differences in BMD at the lumbar spine or upper limb, at any age. Our data suggest that classical ballet classes undertaken between the ages of 10 and 12 years are independently and positively associated with a difference in hip BMD between dancers and controls. The findings are consistent with the hypothesis that this age range identifies a stage of development when the proximal femur is particularly responsive to weightbearing exercise.

Adolescent↗