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Modulation of bone loss during calcium insufficiency by controlled dynamic loading.

date: 04/01/1986
author: Lanyon LE, Rubin CT, Baust G.
publication: Calcif Tissue Int. 1986 Apr;38(4):209-16.
pubmed_ID: 3085898

Changes in the midshaft cross-sectional area of the ulna were measured in egg-laying turkeys on a diet insufficient in calcium. Left:right comparisons were used to assess the bone loss over a six-week period due to 1) calcium insufficiency, 2) calcium insufficiency plus disuse, and 3) calcium insufficiency and disuse interrupted by a short daily period of intermittent loading applied from an external device. Calcium insufficiency alone in the intact ulna resulted in a 15% reduction in cross-sectional area. In the functionally deprived bones this loss was increased to 32%. In bones where the disuse was interrupted by a single short daily period of loading, the degree of bone loss was significantly modified (P less than 0.006) to 25%. No significant difference in the modulating effect of loading was achieved by varying the peak strain from 0.0015 to 0.003, the strain rate from 0.01 to 0.05, or the duration of the single loading period from 100 sec per day to 25 minutes. All the loading regimes employed had been demonstrated to be osteogenic in mature male birds on a diet sufficient in calcium.

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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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Can Using Standers Increase Bone Density In Non-Ambulatory Children?

date: 10/01/2006
author: Katz, Danielle,MD, Snyder, Bryan MD, PhD, Dodek, Anton MD, Holm, Ingrid MD Miller, Claire BS
publication: Abstract as published in the American Academy of Cerebral Palsy and Developmental Medicine (AACPDM) 2006 Conference Proceedings

Purpose: Pathologic fractures are a significant source of morbidity for non-ambulatory children with neuromuscular dysfunction. We hypothesize that increasing weight-bearing in non-ambulatory children will increase bone material density (BMD) and decrease fracture risk. The aim of this pilot study was to demonstrate that non-ambulatory children participating in a standing program for at least two hours a day will experience an increase in BMD in the weight bearing bones. We also evaluate the reliability of measuring BMD at the calcaneous (weight bearing bones) and distal forearm (non-weight bearing bone) using peripheral DXA in delayed, non-ambulatory children.

Methods: After receiving IRB approval, 12 non-ambulatory, quadriplegic children (ages 12-21) consented to participate in a 2 hour/day, 5 day/week standing program. A history, orthopaedic exam, determination of bone age, laboratory tests for metabolic bone disease and BMD at the calcaneal tuberosity and distal forearm metaphyses were obtained. Compliance with the prescribed standing program was monitored for 6 months. BMD was measured using peripheral DXA at baseline and every 3 months. Using Jan. 2003 BMD data as a baseline, the ratio of change in BMD at the calcaneous and distal forearm was evaluated as a function of percent compliance with standing program.

Results: Intrarater reliability for BMD measured by peripheral DXA was good: Pearson correlation for the calcaneous = 0.90 (p=0.01) and for the forearm = 0.96 (p=0.01). Paired t test between two sets of data measured at each site on the same day were not different for calcaneous (t=0.92, df=15, p=0.37) or forearm (t=0.05, df=15, p=0.96). Compliance with the standing program was inconsistent. No patients were 100% compliant. Patients tended to stand longer at the initiation of the study Jan.-April (Jan vs Apr, p = 0.018; Jan vs Jul, p = 0.89; Apr vs Jul, p = 0.063). Compliance (%) was positively correlated (r = -0.62) with increased calcaneous BMD measured in April. This is in contrast to forearm BMD measured at the same time; which was negatively correlated (r = -0.44) with standing compliance. This support the notion that standing preferentially increases bone mass in the weight-bearing bones. However the BMD at the calcaneous measured in July was decreased, perhaps reflecting the decreased compliance the with standing program over the succeeding interval April-July.

Conclusion: It is feasible to have non-ambulatory children participate in a rigorous standing program. The weight bearing ?dose? affects BMD at the calcaneous but the benefit appears to be transient if the intensive standing program is not sustained.

Significance: The intensive use of standers (10 hours/wk) may have a beneficial effect on BMD of weight bearing bones in non-ambulatory children.

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Bone measurements by peripheral quantitative computed tomography (pQCT) in children with cerebral palsy

date: 12/01/2005
author: Binkley T, Johnson J, Vogel L, Kecskemethy H, Henderson R, Specker B.
publication: J Pediatr. 2005 Dec;147(6):791-6.
pubmed_ID: 16356433

OBJECTIVE: To use peripheral quantitative computed tomography (pQCT) to determine bone measurements in patients with cerebral palsy (CP) age 3 to 20 years and compare them with control subjects. STUDY DESIGN: A total of 13 (5 male) patients with CP, along with 2 sex- and age-matched controls for each, were included in a mixed-model analysis with matched pairs as random effects for pQCT bone measurements of the 20% distal tibia. RESULTS: Tibia length was similar in the CP and control groups (P = .57). Weight was marginally higher in the control group (P = .06). Cortical bone mineral content (BMC), area, thickness, polar strength-strain index (pSSI), and periosteal and endosteal circumferences were greater in the control group (P < .05 for all). Relationships between bone measurements and weight showed that cortical BMC, area, periosteal circumference, and pSSI were greater at higher weights in the control group (group-by-weight interaction, P < .05 for all). Cortical thickness was greater in the control group and was correlated with weight. Cortical volumetric bone mineral density (vBMD) was greater with higher weights in the CP group (group-by-weight interaction, P = .03). CONCLUSIONS: Bone strength, as indicated by pSSI, is compromised in children with CP due to smaller and thinner bones, not due to lower cortical bone density.

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Longitudinal changes in bone density in children and adolescents with moderate to severe cerebral palsy.

date: 06/01/2005
author: Henderson RC, Kairalla JA, Barrington JW, Abbas A, Stevenson RD.
publication: J Pediatr. 2005 Jun;146(6):769-75
pubmed_ID: 15973316

OBJECTIVE: To assess the natural history of “growth” in bone mineral density (BMD) in children and adolescents with moderate to severe cerebral palsy (CP). STUDY DESIGN: A prospective, longitudinal, observational study of BMD in 69 subjects with moderate to severe spastic CP ages 2.0 to 17.7 years. Fifty-five subjects were observed for more than 2 years and 40 subjects for more than 3 years. Each evaluation also included assessments of growth, nutritional status, Tanner stage, general health, and various clinical features of CP. RESULTS: Lower BMD z-scores at the initial evaluation were associated with greater severity of CP as judged by gross motor function and feeding difficulty, and with poorer growth and nutrition as judged by weight z-scores. BMD increased an average of 2% to 5%/y in the distal femur and lumbar spine, but ranged widely from +42%/y to -31%. In spite of increases in BMD, distal femur BMD z-scores decrease with age in this population. CONCLUSIONS: Children with severe CP develop over the course of their lives clinically significant osteopenia. Unlike elderly adults, this is not primarily from true losses in bone mineral, but from a rate of growth in bone mineral that is diminished relative to healthy children. The efficacy of interventions to increase BMD can truly be assessed only with a clear understanding of the expected changes in BMD without intervention.

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Bone mineral density in children with cerebral palsy.

date: 04/01/2001
author: Tasdemir HA, Buyukavci M, Akcay F, Polat P, Yildiran A, Karakelleoglu C.
publication: Pediatr Int. 2001 Apr;43(2):157-60.
pubmed_ID: 11285068

BACKGROUND: The purpose of the present study was to evaluate the severity of and factors related to osteopenia in children with cerebral palsy (CP). METHODS: Bone mineral density (BMD), calcium (Ca), phosphate (P), alkaline phosphatase (ALP), creatinine, parathyroid hormone (PTH) and 25-hydroxy vitamin D3 (25OHD3) concentrations were determined in 24 children with CP (15 ambulant, nine non-ambulant), aged between 10 months and 12 years (mean (+/-SD) 4.1+/-2.9 years). These vaules were compared with data obtained from a control group. RESULTS: Adjusted mean BMD values were lower in the patient group than in controls (P<0.05). However, there was no difference between BMD values of ambulant and non-ambulant patients. The Ca and P levels of the patient group were significantly higher than those of controls (P<0.05). CONCLUSIONS: The present study showed that BMD was decreased in all children with CP, but to a greater extent in non-ambulant children with CP, and immobilization is the major effective factor on bone mineralization.