Person:

Bouxsein, Mary

Purpose

Current standard methods to quantify disc height, namely distortion compensated Roentgen analysis (DCRA), have been mostly utilized in the lumbar and cervical spine and have strict exclusion criteria. Specifically, discs adjacent to a vertebral fracture are excluded from measurement, thus limiting the use of DCRA in studies that include older populations with a high prevalence of vertebral fractures. Thus, we developed and tested a modified DCRA algorithm that does not depend on vertebral shape.

Methods

Participants included 1186 men and women from the Framingham Heart Study Offspring and Third Generation Multidetector CT Study. Lateral CT scout images were used to place 6 morphometry points around each vertebra at 13 vertebral levels in each participant. Disc heights were calculated utilizing these morphometry points using DCRA methodology and our modified version of DCRA, which requires information from fewer morphometry points than the standard DCRA.

Results

Modified DCRA and standard DCRA measures of disc height are highly correlated, with concordance correlation coefficients above 0.999. Both measures demonstrate good inter- and intra-operator reproducibility. 13.9 % of available disc heights were not evaluable or excluded using the standard DCRA algorithm, while only 3.3 % of disc heights were not evaluable using our modified DCRA algorithm.

Conclusions

Using our modified DCRA algorithm, it is not necessary to exclude vertebrae with fracture or other deformity from disc height measurements as in the standard DCRA. Modified DCRA also yields identical measurements to the standard DCRA. Thus, the use of modified DCRA for quantitative assessment of disc height will lead to less missing data without any loss of accuracy, making it a preferred alternative to the current standard methodology.

Musculoskeletal modeling requires information on muscle parameters such as cross-sectional area (CSA) and moment arms. A variety of previous studies have reported muscle parameters in the trunk based on in vivo imaging, but there remain gaps in the available data as well as limitations in the generalizability of such data. Specifically, available trunk muscle CSA data is very limited for older adults, lacking entirely in the thoracic region. In addition, previous studies have made measurements in groups of healthy volunteers or hospital patients who may not be representative of the population in general. Finally, such studies have not reported data for the major muscles connecting the upper limb to the thoracic trunk. In this study, muscle morphology measurements were made for major muscles present in the trunk between vertebral levels T6 and L5 using quantitative computed tomography scans from a community-based sample of 100 men and women aged 36–87. We present regression equations to predict trunk muscle CSA and position relative to the vertebral body in the transverse plane from sex, age, height and weight at vertebral levels T6 to L5. Regressions were also developed for predicting anatomical CSA and muscle moment arms, which were estimated using literature data on muscle line of action. This work thus provides a resource for estimating muscle parameters in the general population for musculoskeletal modeling of the thoraco-lumbar trunk.