Bonnyman (2011) Assessment of Bone Geometry in PostmenopausalWomen with Osteoporosis of the Spine Before and After a 6 Month Aquatic Exercise Program
Increased physical activity is associated with better physical and mental well-being. In postmenopausal women, land-based exercise has a modest effect on bone strength which is predominantly reflected in the spatial distribution(geometry) of bone mineral at the skeletal sites targeted by the exercise .However, the risks and benefits of exercise for women with osteoporotic vertebral fracture (VFs) who are at high risk for future fracture are not known. Women with established osteoporosis may prefer exercising in water where compressive loads are reduced. However, it is not known if the reduced compressive loading is detrimental to bone health. Also contributing to this evidence gap is the limited methods available for measuring vertebral bone geometry which may be expected to respond to exercises targeting the trunk. Bone geometry can be measured using computed tomography scans but this involves exposure to a substantial dose of radiation. Semi-automated analyses of dual energy X-ray absorptiometry (DXA) vertebral fracture assessment (VFA) scans provide measures of vertebral height (VH); however, the measurement properties of this outcome have not been established. Measures of mechanical bone strength and volumetric density also provide insight into bone adaptations to exercise. Noresearch has yet investigated the effect of exercising in water on bone geometry in women with osteoporotic VFs.
The overall purpose of this thesis was to investigate methods of measuring bone geometry in women with osteoporotic VFs that could be used in a future clinical trial to determine the effect of water exercises on bone in women with VFs. The first objective was to determine the relative and absolute intra-rater reliability of VHs in postmenopausal women with and without VFs. In the second study, protocols for recruitment of postmenopausal women with osteoporotic VFsfor a 6 month water exercise intervention and protocols for assessing proposed outcome measures were piloted to determine the recruitment, adherence to the intervention, adherence to the assessment protocol, safety of the intervention and assessment and retention. Methods: To address the first objective, DXA VFA scans were acquired for 32women [mean (SD) age 70(7)] and analyzed on 2 occasions, 4 weeks apart, by a single rater using a predetermined protocol. Semi-automated software derived measures of anterior, middle, and posterior VH. Intra-rater relative reliability was estimated using the intra class correlation coefficient (ICC) with 95% confidence intervals (95% CI). Absolute reliability was estimated using standard error of measurement (SEM) with 95% CI. To address the second objective, women 60years and older with one or more VF were recruited through two osteoporosis clinics and poster advertisements over two months. Feasibility of recruitment was summarized using the CONSORT flow diagram. Adherence to the six monthcommunity-based aquatic exercise program (74 sessions) was evaluated by percentage of sessions attended. Adherence to the assessment protocol was evaluated based on the number of data points lost. The safety was assessed based on the occurrence of adverse events that were documented as major and minor. Retention was assessed as number of participants returning for follow-up.
DXA-based VH intra-rater reliability could be estimated from T9 to L4,with reduced visibility from T4 to T8. The ICCs were > 0.80 and the SEM was less than 1.17 mm for all VH except for the posterior aspect of T9 (ICC = 0.62(0.15, 0.84), SEM = 0.92 mm). For the feasibility study, 10 participants were recruited in 10 weeks by expanding the inclusion criteria. The average adherence to the intervention was 68%. No measures of VH were obtained for two participants. Movement during acquisition and unanticipated protocol changes resulted in loss of 46% of pQCT scans and 10% of physical performance measurement data. There was one major adverse event (fracture). Retention was100% at 6 months and 89% at 12 months.
Intra-rater reliability was acceptable for VH between T10 and L4.Further study is needed to assess other measurement properties of DXA-based VH measures and to identify methods for assessing more proximal vertebral levels. Further study is needed to determine feasible protocols for recruitment and assessment of outcome measures. Screening tests for falls risk and protocol for implementing suitable safety precautions are recommended.