Alison M. Greig

The vertebral fracture cascade in osteoporosis: a review of aetiopathogenesis

Once an initial vertebral fracture is sustained, the risk of subsequent vertebral fracture increases significantly. This phenomenon has been termed the “vertebral fracture cascade”. Mechanisms underlying this fracture cascade are inadequately understood, creating uncertainty in the clinical environment regarding prevention of further fractures. The cascade cannot be explained by low bone mass alone, suggesting that factors independent of this parameter contribute to its aetiopathogenesis. This review explores physiologic properties that may help to explain the vertebral fracture cascade. Differences in bone properties, including bone mineral density and bone quality, between individuals with and those without osteoporotic vertebral fractures are discussed. Evidence suggests that non-bone parameters differ between individuals with and those without osteoporotic vertebral fractures. Spinal properties, including vertebral macroarchitecture, intervertebral disc integrity, spinal curvature and spinal loading are compared in these groups of individuals. Cross-sectional studies also indicate that neurophysiologic properties, particularly trunk control and balance, are affected by the presence of a vertebral fracture. This review provides a synthesis of the literature to highlight the multi-factorial aetiopathogenesis of the vertebral fracture cascade. With a more comprehensive understanding of the mechanisms underlying this clinical problem, more effective preventative strategies may be developed to offset the fracture cascade.

Thoracic Kyphosis Affects Spinal Loads and Trunk Muscle Force

Background and Purpose Patients with increased thoracic curvature often come to physical therapists for management of spinal pain and disorders. Although treatment approaches are aimed at normalizing or minimizing progression of kyphosis, the biomechanical rationales remain unsubstantiated. Subjects Forty-four subjects (mean age [±SD]=62.3±7.1 years) were dichotomized into high kyphosis and low kyphosis groups. Methods Lateral standing radiographs and photographs were captured and then digitized. These data were input into biomechanical models to estimate net segmental loading from T2–L5 as well as trunk muscle forces. Results The high kyphosis group demonstrated significantly greater normalized flexion moments and net compression and shear forces. Trunk muscle forces also were significantly greater in the high kyphosis group. A strong relationship existed between thoracic curvature and net segmental loads (r =.85–.93) and between thoracic curvature and muscle forces (r =.70–.82). Discussion and Conclusion This study provides biomechanical evidence that increases in thoracic kyphosis are associated with significantly higher multisegmental spinal loads and trunk muscle forces in upright stance. These factors are likely to accelerate degenerative processes in spinal motion segments and contribute to the development of dysfunction and pain.

Radiographic measures of thoracic kyphosis in osteoporosis: Cobb and vertebral centroid angles

ObjectiveSeveral measures can quantify thoracic kyphosis from radiographs, yet their suitability for people with osteoporosis remains uncertain. The aim of this study was to examine the validity and reliability of the vertebral centroid and Cobb angles in people with osteoporosis.Design and patientsLateral radiographs of the thoracic spine were captured in 31 elderly women with osteoporosis. Thoracic kyphosis was measured globally (T1–T12) and regionally (T4–T9) using Cobb and vertebral centroid angles. Multisegmental curvature was also measured by fitting polynomial functions to the thoracic curvature profile. Canonical and Pearson correlations were used to examine correspondence; agreement between measures was examined with linear regression.ResultsModerate to high intra- and inter-rater reliability was achieved (SEM = 0.9–4.0°). Concurrent validity of the simple measures was established against multisegmental curvature (r = 0.88–0.98). Strong association was observed between the Cobb and centroid angles globally (r = 0.84) and regionally (r = 0.83). Correspondence between measures was moderate for the Cobb method r = 0.72), yet stronger for the centroid method (r = 0.80). The Cobb angle was 20% greater for regional measures due to the influence of endplate tilt.ConclusionsRegional Cobb and centroid angles are valid and reliable measures of thoracic kyphosis in people with osteoporosis. However, the Cobb angle is biased by endplate tilt, suggesting that the centroid angle is more appropriate for this population.

Balance impairment is related to vertebral fracture rather than thoracic kyphosis in individuals with osteoporosis.

Introduction and hypothesisBalance impairments have been identified in people with osteoporosis. Although an association between thoracic kyphosis and impaired balance has been reported, the specific role of vertebral fractures has not been considered. This study aimed to investigate the independent effects of osteoporotic vertebral fracture and thoracic kyphosis on balance characteristics in an osteoporotic population.MethodsTwenty-two individuals with osteoporosis were divided into groups with (n=10) and without (n=12) radiologically diagnosed fracture, and into groups with low (n=11) and high (n=11) thoracic kyphosis. Force-plate-derived balance parameters were recorded during three static standing tasks of 70-s duration. Balance measures were compared between fracture and kyphosis groups, and significant differences were further explored through subgroup analyses, to tease out the relationships between confounded independent variables (fracture and kyphosis) and balance measures.ResultsIn the anterior–posterior direction, the range and root mean square of shear forces (p=0.048 and p=0.032, respectively), and range of displacement of the centre of pressure (p=0.049) were greater in the fracture group. There were no differences between groups when comparison was based on the magnitude of thoracic kyphosis (all p≥0.264). Analyses of subgroups supported these findings.DiscussionVertebral fracture but not thoracic kyphosis is associated with impaired balance characteristics in the osteoporosis population. This finding has important implications for fracture prevention and conservative management regimes.

Trunk Muscle Activity Is Modified in Osteoporotic Vertebral Fracture and Thoracic Kyphosis with Potential Consequences for Vertebral Health

This study explored inter-relationships between vertebral fracture, thoracic kyphosis and trunk muscle control in elderly people with osteoporosis. Osteoporotic vertebral fractures are associated with increased risk of further vertebral fractures; but underlying mechanisms remain unclear. Several factors may explain this association, including changes in postural alignment (thoracic kyphosis) and altered trunk muscle contraction patterns. Both factors may increase risk of further fracture because of increased vertebral loading and impaired balance, which may increase falls risk. This study compared postural adjustments in 24 individuals with osteoporosis with and without vertebral fracture and with varying degrees of thoracic kyphosis. Trunk muscle electromyographic activity (EMG) associated with voluntary arm movements was recorded and compared between individuals with and without vertebral fracture, and between those with low and high thoracic kyphosis. Overall, elderly participants in the study demonstrated co-contraction of the trunk flexor and extensor muscles during forwards arm movements, but those with vertebral fractures demonstrated a more pronounced co-contraction than those without fracture. Individuals with high thoracic kyphosis demonstrated more pronounced alternating flexor and extensor EMG bursts than those with less kyphosis. Co-contraction of trunk flexor and extensor muscles in older individuals contrasts the alternating bursts of antagonist muscle activity in previous studies of young individuals. This may have several consequences, including altered balance efficacy and the potential for increased compressive loads through the spine. Both of these outcomes may have consequences in a population with fragile vertebrae who are susceptible to fracture.

Program evaluation of a model to integrate internationally educated health professionals into clinical practice

BackgroundThe demand for health professionals continues to increase, partially due to the aging population and the high proportion of practitioners nearing retirement. The University of British Columbia (UBC) has developed a program to address this demand, by providing support for internationally trained Physiotherapists in their preparation for taking the National Physiotherapy competency examinations.The aim was to create a program comprised of the educational tools and infrastructure to support internationally educated physiotherapists (IEPs) in their preparation for entry to practice in Canada and, to improve their pass rate on the national competency examination.MethodsThe program was developed using a logic model and evaluated using program evaluation methodology. Program tools and resources included educational modules and curricular packages which were developed and refined based on feedback from clinical experts, IEPs and clinical physical therapy mentors. An examination bank was created and used to include test-enhanced education. Clinical mentors were recruited and trained to provide clinical and cultural support for participants.ResultsThe IEP program has recruited 124 IEPs, with 69 now integrated into the Canadian physiotherapy workforce, and more IEPs continuing to apply to the program. International graduates who participated in the program had an improved pass rate on the national Physiotherapy Competency Examination (PCE); participation in the program resulted in them having a 28% (95% CI, 2% to 59%) greater possibility of passing the written section than their counterparts who did not take the program. In 2010, 81% of all IEP candidates who completed the UBC program passed the written component, and 82% passed the clinical component.ConclusionThe program has proven to be successful and sustainable. This program model could be replicated to support the successful integration of other international health professionals into the workforce.