Good vibrations and strong bones?

Effects of whole-body vibration training with the same amplitude and different frequencies on the proximal femoral bone density in elderly women

BACKGROUND

This study investigated the whole-body vibration training with the same amplitude and different vibration frequencies was used to compare the difference in bone mineral density (BMD) of the proximal femurs in elderly women.

METHODS

This study included three age-, height-, and weight-matched groups; the medium-frequency group (N.=19) received 24 weeks of whole-body vibration training with a vibration frequency of 20 Hz; the high-frequency group (N.=18) received 24 weeks of whole-body vibration training with a vibration frequency of 40 Hz; and the control group (N.=19) received no intervention. Changes in the BMD of the proximal femur on the dominant side in the three groups were measured using dual-energy X-ray absorptiometry.

RESULTS

According to the between-group comparison, the BMD of the greater trochanter and Ward's triangle in the middle-frequency group increased by 7.6% and 13.3%, respectively (P<0.05), while the BMD of the greater trochanter and Ward's triangle in the high-frequency group increased by 10.6% and 16.9%, respectively (P<0.05). There was no significant difference in BMD between the medium-frequency group and the high-frequency group at 24 weeks (P>0.05).

CONCLUSIONS

Whole-body vibration training with a frequency of 20 Hz and 40 Hz improved the BMD of the proximal femurs in elderly women to varying degrees but had no significant effect on femoral neck BMD. Under the same amplitude conditions, an increase in vibration frequency did not cause further changes in BMD.

Evaluation of cortical bone perfusion using dynamic contrast enhanced ultrashort echo time imaging: a feasibility study

Background

Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) has been used to study perfusion in a wide variety of soft tissues including the bone marrow. Study of perfusion in hard tissues such as cortical bone has been much more limited because of the lack of detectable MR signal from them using conventional pulse sequences. However, two-dimensional (2D) ultrashort echo time (UTE) sequences detect signal from cortical bone and allow fast imaging of this tissue. In addition, adiabatic 2D inversion recovery UTE (IR-UTE) sequences can provide excellent signal suppression of soft tissues, such as muscle and marrow, and allow cortical bone to be seen with high contrast and reduced artefacts. We aimed to assess the feasibility of using 2D UTE and 2D IR-UTE sequences to perform DCE-MRI in the cortical bone of rabbits and human volunteers.

Methods

Cortical bone perfusion was studied in rabbits (n=12) and human volunteers (n=3) using 2D UTE and 2D IR-UTE sequences on a clinical 3T scanner. Dynamic data with an in-plane resolution of ~0.5×0.5 mm², single slice thickness of 3 mm for rabbits and 10 mm for human volunteers, and temporal resolution of 23 s for 2D UTE imaging of rabbits, 28 s for 2D UTE imaging of human volunteers, and 60 s for 2D IR-UTE imaging of both the rabbits and human volunteers were acquired before and after the injection of a Gd contrast agent (Gd-BOPTA: Multihance; Bracco Imaging SpA, Milan, Italy). The dose was 0.06 mmol/kg for rabbits and 0.2 mmol/kg for human subjects. Kinetic analyses based on the Brix model, as well as simple calculations of maximum enhancement (ME) and enhancement slope (ES), were performed.

Results

The 12 rabbits showed a mean K^trans of 0.36±0.07 min^-1, K_ep of 8.42±3.17 min^-1, ME of 28.30±6.83, ES of 0.35±0.18 for the femur with the 2D UTE sequence, and a mean K^trans of 0.45±0.10 min^-1, K_ep of 9.80±0.50 min^-1, ME of 48.84±12.12, and ES of 0.69±0.27 for the femur with the 2D IR-UTE sequence. Lower ME and ES values were observed in the tibial midshaft of healthy human volunteers compared to rabbits.

Conclusions

These results show that 2D UTE and 2D IR-UTE sequences are capable of detecting dynamic contrast enhancement in cortical bone in both rabbits and healthy human volunteers. Clinical studies with these techniques are likely to be feasible.

Response to functional electrical stimulation cycling in women with spinal cord injuries using dual-energy X-ray absorptiometry and peripheral quantitative computed tomography: a case series

BACKGROUND

Loss of bone mass is common after spinal cord injury (SCI). One rehabilitation modality that has shown some promise for maintaining bone health is the functional electrical stimulation (FES) cycle ergometer. Although there has been some research investigating bone health and FES cycle ergometry, few have provided a detailed description of the changes that can occur in bone mass and soft-tissue mass.

OBJECTIVE

To use 2 types of bone imaging, peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA), to provide a detailed description of bone and soft-tissue response to FES cycle ergometry training in women with SCI.

STUDY DESIGN

Case series; a 6-month program of FES cycle ergometry for women with chronic motor complete (n = 2) and incomplete (n = 1) SCI.

SETTING

Outpatient rehabilitation center in Canada.

METHODS

Three women participated in a thrice weekly 6-month exercise program of FES cycle ergometry. We used DXA (lower extremity) and pQCT at the midshaft (50%) and distal (5%) sites of the tibia to assess bone density and soft-tissue mass before and after the exercise program.

RESULTS

There was an increase or maintenance in bone mineral density by DXA and pQCT in the lower extremity for all 3 participants. Muscle mass by DXA increased in the lower extremity in 2 participants.

CONCLUSION

In this case series, we note a positive response in bone mass and soft-tissue mass in the lower extremity after a 6-month FES cycle ergometry program.

Association of coronary artery and aortic calcium with lumbar bone density: the MESA Abdominal Aortic Calcium Study

Atherosclerosis and osteoporosis share many risk factors, but their independent association is unclear. The authors investigated the independent associations between volumetric trabecular bone mineral density (vBMD) of the lumbar spine and coronary artery calcium (CAC) and abdominal aortic calcium (AAC). During 2002-2005, they used quantitative computed tomography to assess vBMD and the presence and extent of CAC and AAC among 946 women (mean age = 65.5 years) and 963 men (mean age = 64.1 years) in a substudy of the Multi-Ethnic Study of Atherosclerosis. Prevalences of CAC were 47% and 68% in women and men, respectively, and AAC prevalences were 70% and 73%. Sequential, sex-specific regression models included adjustment for age, ethnicity, body mass index, hypertension, dyslipidemia, diabetes mellitus, smoking, alcohol consumption, physical activity, interleukin-6, C-reactive protein, homocysteine, and sex hormones. After full adjustment, lower vBMD was associated with greater CAC score among women (P < 0.002) and greater AAC score among women (P = 0.004) and men (P < 0.001). After adjustment, vBMD quartile was inversely associated with CAC prevalence (P-trend = 0.05) in women and AAC prevalence (P-trend < 0.01) in men. Partially and fully adjusted models showed similar results. Though modest, these significant, independent associations suggest that atherosclerosis and bone loss may be related.