Category: Research and Articles

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Static vs dynamic loads as an influence on bone remodeling.

date: 01/01/2004
author: Lanyon LE, Rubin CT.
publication: J Biomech. 1984;17(12):897-905.
pubmed_ID: 6520138

Remodeling activity in the avian ulna was assessed under conditions of disuse alone, disuse with a superimposed continuous compressive load, and disuse interrupted by a short daily period of intermittent loading. The ulnar preparation consisted of the 110mm section of the bone shaft between two submetaphyseal osteotomies. Each end of the preparation was transfixed by a stainless steel pin and the shaft either protected from normal functional loading with the pins joined by external fixators, loaded continuously in compression by joining the pins with springs, or loaded intermittently in compression for a single 100s period per day by engaging the pins in an Instron machine. Similar loads (525 N) were used in both static and dynamic cases. The strains engendered were determined by strain gauges, and at their maximum around the bone’s midshaft were -0.002. The intermittent load was applied at a frequency of 1 Hz as a ramped square wave, with a rate of change of strain during the ramp of 0.01 s-1. Peak strain at the midshaft of the ulna during wing flapping in the intact bone was recorded from bone bonded strain gauges in vivo as -0.0033 with a maximum rate of change of strain of 0.056 s-1. Examination of bone sections from the midpoint of the preparation after an 8 week period indicated that in both non-loaded and statically loaded bones there was an increase in both endosteal diameter and intra cortical porosity. These changes produced a decrease in cross sectional area which was similar in the two groups (-13%).(ABSTRACT TRUNCATED AT 250 WORDS)

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Calcium balance in paraplegic patients: influence of injury duration and ambulation.

date: 10/01/1978
author: Kaplan PE, Gandhavadi B, Richards L, Goldschmidt J.
publication: Arch Phys Med Rehabil. 1978 Oct;59(10):447-50.
pubmed_ID: 718407

Calcium metabolic balance determinations, which have been done in various clinical and experimental conditions, were applied to the study of 8 spinal cord injured patients receiving a diet with 1600 mg calcium and 85 to 120 gm protein daily. All of the patients had hypercalciuria prior to ambulation. Those with spinal cord injuries of less than 3 months duration (early group) had a calcium balance of -27 mg before ambulation and 235 mg after ambulation. Patients with spinal cord injuries of 6 months or more duration (late group) had calcium balances of 55 mg before ambulation and 175 mg after ambulation. Ambulation significantly decreased the hypercalciuria and modified the calcium balance in a positive direction. Smaller changes were noted in the responses of the late group than in those of the early group. Early ambulation will probably prevent bone loss, calcium stones in the genitourinary tract, and other sequellae of negative calcium balance.

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The effect of a weight-bearing physical activity program on bone mineral content and estimated volumetric density in children with spastic cerebral palsy.

date: 07/01/1999
author: Chad KE, Bailey DA, McKay HA, Zello GA, Snyder RE.
publication: J Pediatr 1999 Jul;135(1):115-7.
pubmed_ID: 10393617

After an 8-month physical activity intervention in children with cerebral palsy, increases in femoral neck bone mineral content (BMC) (9.6%), volumetric bone mineral density (v BMD) (5.6%), and total proximal femur BMC (11.5%) were observed in the intervention group (n = 9) compared with control subjects (n = 9; femoral neck BMC, -5. 8%; v BMD, -6.3%; total proximal femur BMC, 3.5%).

Publication Types:
? Clinical Trial
? Randomized Controlled Trial

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Bone mineral status in paraplegic patients who do or do not perform standing.

date: 05/01/1994
author: Goemaere S, Van Laere M, De Neve P, Kaufman JM.
publication: Osteoporos Int. 1994 May;4(3):138-43.
pubmed_ID: 8069052
:
Bone mineral density (BMD) was assessed by dual-photon X-ray absorptiometry at the lumbar spine (L3, L4), the proximal femur and the femoral shaft, and by single-photon absorptiometry at the forearm in 53 patients with complete traumatic paraplegia of at least 1 year’s duration and in age- and sex-matched healthy controls. The patients did (n = 38) or did not (n = 15) regularly perform passive weightbearing standing with the aid of a standing device. Compared with the controls, the BMD of paraplegic patients was preserved in the lumbar spine and was markedly decreased in the proximal femur (33%) and the femoral shaft (25%). When considering all patients performing standing, they had a better-preserved BMD at the femoral shaft (p = 0.009), but not at the proximal femur, than patients not performing standing. BMD at the lumbar spine (L3, L4) was marginally higher in the standing group (significant only for L3; p = 0.040). A subgroup of patients performing standing with use of long leg braces had a significantly higher BMD at the proximal femur than patients using a standing frame or a standing wheelchair (p = 0.030). The present results suggest that passive mechanical loading can have a beneficial effect on the preservation of bone mass in osteoporosis found in paraplegics.

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Osteoporosis, calcium and physical activity.

date: 03/15/1987
author: Martin AD, Houston CS.
publication: CMAJ. 1987 Mar 15;136(6):587-93.
pubmed_ID: 3545420

Sales of calcium supplements have increased dramatically since 1983, as middle-aged women seek to prevent or treat bone loss due to osteoporosis. However, epidemiologic studies have failed to support the hypothesis that larger amounts of calcium are associated with increased bone density or a decreased incidence of fractures. The authors examine the evidence from controlled trials on the effects of calcium supplementation and physical activity on bone loss and find that weight-bearing activity, if undertaken early in life and on a regular basis, can increase the peak bone mass of early adulthood, delay the onset of bone loss and reduce the rate of loss. All of these factors will delay the onset of fractures. Carefully planned and supervised physical activity programs can also provide a safe, effective therapy for people who have osteoporosis.

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Weight-bearing exercise training and lumbar bone mineral content in postmenopausal women.

date: 06/01/1988
author: Dalsky GP, Stocke KS, Ehsani AA, Slatopolsky E, Lee WC, Birge SJ.
publication: Ann Intern Med. 1988 Jun;108(6):824-8.
pubmed_ID: 3259410

STUDY OBJECTIVE: To assess the effect of weight-bearing exercise training and subsequent detraining on lumbar bone mineral content in postmenopausal women. DESIGN: Non-randomized, controlled, short-term (9 months) trial and long-term (22 months) exercise training and detraining (13 months). SETTING: Section of applied physiology at a university school of medicine. PATIENTS: Thirty-five healthy, sedentary postmenopausal women, 55 to 70 years old. All women completed the study. There was 90% compliance with exercise training. INTERVENTIONS: All women were given calcium, 1500 mg daily. The exercise group did weight-bearing exercise (walking, jogging, stair climbing) at 70% to 90% of maximal oxygen uptake capacity for 50 to 60 min, 3 times weekly. MEASUREMENTS AND MAIN RESULTS: Bone mineral content increased 5.2% (95% confidence interval [CI], 2.0% to 8.4%; P = 0.0037) above baseline after short-term training whereas there was no change (-1.4%) in the control group. After 22 months of exercise, bone mineral content was 6.1% (95% CI, 3.9% to 8.3% above baseline; P = 0.0001) in the long-term training group. After 13 months of decreased activity, bone mass was 1.1% above baseline in the detraining group. CONCLUSIONS: Weight-bearing exercise led to significant increases above baseline in bone mineral content which were maintained with continued training in older, postmenopausal women. With reduced weight-bearing exercise, bone mass reverted to baseline levels. Further studies are needed to determine the threshold exercise prescription that will produce significant increases in bone mass.

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The influence of activity on calcium metabolism.

date: 12/01/1985
author: Whedon GD.
publication: J Nutr Sci Vitaminol (Tokyo). 1985 Dec;31 Suppl:S41-4.
pubmed_ID: 3915756
Outside_URL: http://www.ncbi.nlm.nih.gov/pubmed/3915756
Many studies and observations have shown the bone-losing effects of physical inactivity of various forms. Contrariwise, less precise studies and observations have supported the reasonable premise that mechanical loading of the skeleton via physical activity shifts the balance of bone remodeling in favor of bone formation, and appears to do so at all ages. Some interesting starts have been made in research to discover the mechanisms of the action on bone of mechanical loading, but many pathways remain to be explored. Besides the mechanical forces, we need to know more about the interrelations of muscle function, probably mediated through muscle-tendon pull on periosteum, and more about other likely influences, notably changes in circulation to bones. The practical significance relative to calcium metabolism and aging of what has been learned thus far on the effects of activity, is that prolonged inactivity, either in a chair or in bed, is to be avoided, because of its deleterious effects, and that reasonably energetic gravitational exercise, such as walking or possibly jogging, promotes maintenance of bone health.

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Low magnitude mechanical loading is osteogenic in children with disabling conditions.

date: 03/19/2004
author: Ward K, Alsop C, Caulton J, Rubin C, Adams J, Mughal Z.
publication: J Bone Miner Res. 2004 Mar;19(3):360-9. Epub 2004 Jan 27.
pubmed_ID: 15040823

The osteogenic potential of short durations of low-level mechanical stimuli was examined in children with disabling conditions. The mean change in tibia vTBMD was +6.3% in the intervention group compared with -11.9% in the control group. This pilot randomized controlled trial provides preliminary evidence that low-level mechanical stimuli represent a noninvasive, non-pharmacological treatment of low BMD in children with disabling conditions. INTRODUCTION: Recent animal studies have demonstrated the anabolic potential of low-magnitude, high-frequency mechanical stimuli to the trabecular bone of weight-bearing regions of the skeleton. The main aim of this prospective, double-blind, randomized placebo-controlled pilot trial (RCT) was to examine whether these signals could effectively increase tibial and spinal volumetric trabecular BMD (vTBMD; mg/ml) in children with disabling conditions. MATERIALS AND METHODS: Twenty pre-or postpubertal disabled, ambulant, children (14 males, 6 females; mean age, 9.1 +/- 4.3 years; range, 4-19 years) were randomized to standing on active (n = 10; 0.3g, 90 Hz) or placebo (n = 10) devices for 10 minutes/day, 5 days/week for 6 months. The primary outcomes of the trial were proximal tibial and spinal (L2) vTBMD (mg/ml), measured using 3-D QCT. Posthoc analyses were performed to determine whether the treatment had an effect on diaphyseal cortical bone and muscle parameters. RESULTS AND CONCLUSIONS: Compliance was 44% (4.4 minutes per day), as determined by mean time on treatment (567.9 minutes) compared with expected time on treatment over the 6 months (1300 minutes). After 6 months, the mean change in proximal tibial vTBMD in children who stood on active devices was 6.27 mg/ml (+6.3%); in children who stood on placebo devices, vTBMD decreased by -9.45 mg/ml (-11.9%). Thus, the net benefit of treatment was +15.72 mg/ml (17.7%; p = 0.0033). In the spine, the net benefit of treatment, compared with placebo, was +6.72 mg/ml, (p = 0.14). Diaphyseal bone and muscle parameters did not show a response to treatment. The results of this pilot RCT have shown for the first time that low-magnitude, high-frequency mechanical stimuli are anabolic to trabecular bone in children, possibly by providing a surrogate for suppressed muscular activity in the disabled. Over the course of a longer treatment period, harnessing bone’s sensitivity to these stimuli may provide a non-pharmacological treatment for bone fragility in children.

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Pathological fractures in patients with cerebral palsy.

date: 10/01/1996
author: Brunner R, Doderlein L.
publication: J Pediatr Orthop B. 1996 Fall;5(4):232-8. Comment in: J Pediatr Orthop B. 1996 Fall;5(4):223-4.
pubmed_ID: 8897254

A retrospective study was made of 37 patients with 54 fractures that occurred without significant trauma. The morbidity and causes of these pathological fractures in patients with cerebral palsy were analyzed. The major causes for the fractures were long and fragile lever arms and stiffness in major joints, particularly the hips and knees. An additional factor was severe osteoporosis following a long period of postoperative immobilization. Seventy-four percent of the fractures occurred in the femoral shaft and supracondylar region. Stress fractures were rare (7%) and involved only the patella. Conservative treatment was sufficient in most cases but surgical fixation provided a good alternative for fractures of the femoral shaft. Intraarticular fractures with joint incongruity resulted in a decreased level of activity of the patient. Since osteoporosis is a major risk factor, patients with cerebral palsy should bear weight to prevent pathological fractures. Any stiffness of major joints and extended periods of immobilization should be avoided.

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Cardiopulmonary response in spinal cord injury patients: effect of pneumatic compressive devices.

date: 03/01/1983
author: Huang CT, Kuhlemeier KV, Ratanaubol U, McEachran AB, DeVivo MJ, Fine PR.
publication: Arch Phys Med Rehabil. 1983 Mar;64(3):101-6.
pubmed_ID: 6830418

The purpose of this study was to determine the effects of an inflatable abdominal corset and bilateral pneumatic leg splints on certain physiologic parameters during and after postural change in 27 quadriplegic patients. Data reflecting respiratory rate, tidal volume, heart rate, systolic and diastolic blood pressure were collected and analyzed. Measurements were acquired with patients in supine, 20 degrees head-up, 45 degrees head-up, and 20 degrees head-down positions. The study population was divided into 2 groups of cervical spinal cord injured patients: group I included 13 patients with C6 or C7 lesions; group II included 14 patients with C4 or C5 lesions. The mean time between injury and data collection was 47 days. Several trends were identified: (1) the neurologic level of lesion in quadriplegics appears relatively unimportant in determining cardiopulmonary response to postural change; (2) the use of assistive compressive devices does not improve pulmonary ventilatory parameters during postural change, although such devices do help maintain cardiovascular parameters; and (3) the abdominal corset appears more effective than pneumatic leg splints in maintaining blood pressure at pretilt levels. A tidal volume of 350ml to 400ml is most easily maintained by placing patients in a supine position and eschewing assistive compressive devices. Because the pneumatic devices proved successful in helping quadriplegic patients maintain cardiovascular stability during postural changes, therapeutic modalities, such as tilt table treatments, may be initiated at an earlier stage in the rehabilitation process.