The lower lumbar motion segments L4-5 and L5-S1 showed larger AP and PD translations, respectively, than the higher vertebral motion segments during the weight-lifting motion. The data provide insight into the physiological motion characteristics of the lumbar spine and potential mechanical mechanisms of lumbar disease development.

BACKGROUND CONTEXT Previous studies have reported position-dependent changes of the lumbar intervertebral foramen (LIVF) dimensions at different static flexion-extension postures. However, the changes of the LIVF dimensions during dynamic body motion have not been reported. PURPOSE The objective of this study was to investigate the in-vivo dimensions of the LIVF during a dynamic weight-lifting activity. STUDY DESIGN/SETTING A retrospective study. METHODS Ten asymptomatic subjects were recruited for this study. 3D vertebral models of the lumbar segments from L2 to S1 were constructed for each subject using MR images. The lumbar spine was then imaged using a dual fluoroscopic imaging system as the subject performed a dynamic weight-lifting activity from an upper body position of 45° to a maximal extension position. The in-vivo positions of the vertebrae along the motion path were reproduced using the 3D vertebral models and the fluoroscopic images. The minimal area, height, and width of each LIVF during the dynamic body motion were analyzed. RESULTS The LIVF area and width monotonically decreased with lumbar extension at all levels except L5-S1 (p < 0.05). On average, the LIVF area decreased by 7.4 ± 6.7 %, 10.8 ± 7.7 % and 10.0 ± 8.0 % at the L2–3, L3–4 and L4–5 levels, respectively, from the flexion to the upright standing position, and by 6.4 ± 5.0 %, 7.7 ± 7.4 % and 5.1 ± 5.1 %, respectively, from the upright standing to the extension position. LIVF height remained relatively constant at all segments during the dynamic activity. The foramen area, height, and width of the L5-S1 remained relatively constant throughout the activity. CONCLUSIONS Human lumbar foramen dimensions show segment-dependent characteristics during the dynamic weight-lifting activity.

Recent biomechanics studies have revealed distinct kinematic behavior of different lumbar segments. The mechanisms behind these segment-specific biomechanical features are unknown. This study investigated the in vivo geometric characteristics of human lumbar intervertebral discs.Magnetic resonance images of the lumbar spine of 41 young Chinese individuals were acquired. Disc geometry in the sagittal plane was measured for each subject, including the dimensions of the discs, nucleus pulposus (NP), and annulus fibrosus (AF). Segmental lordosis was also measured using the Cobb method.In general, the disc length increased from upper to lower lumbar levels, except that the L4/5 and L5/S1 discs had similar lengths. The L4/5 NP had a height of 8.6 ± 1.3 mm, which was significantly higher than all other levels (P < 0.05). The L5/S1 NP had a length of 21.6 ± 3.1 mm, which was significantly longer than all other levels (P < 0.05). At L4/5, the NP occupied 64.0% of the disc length, which was significantly less than the NP of the L5/S1 segment (72.4%) (P < 0.05). The anterior AF occupied 20.5% of the L4/5 disc length, which was significantly greater than that of the posterior AF (15.6%) (P < 0.05). At the L5/S1 segment, the anterior and posterior AFs were similar in length (14.1% and 13.6% of the disc, respectively). The height to length (H/L) ratio of the L4/5 NP was 0.45 ± 0.06, which was significantly greater than all other segments (P < 0.05). There was no correlation between the NP H/L ratio and lordosis.Although the lengths of the lower lumbar discs were similar, the geometry of the AF and NP showed segment-dependent properties. These data may provide insight into the understanding of segment-specific biomechanics in the lower lumbar spine. The data could also provide baseline knowledge for the development of segment-specific surgical treatments of lumbar diseases.

Background Context Neuroforaminal stenosis is one of the key factors causing clinical symptoms in patients with cervical radiculopathy. Previous quantitative studies on the neuroforaminal dimensions have focused on measurements in a static position. Little is known about dimensional changes of the neuroforamen in the cervical spine during functional dynamic neck motion under physiological loading conditions. Purpose To investigate the in vivo dimensional changes of the neuroforamen in human cervical spine (C3-C7) during dynamic flexion-extension neck motion. Study Design A case-control study. Methods 10 asymptomatic subjects were recruited for this study. The cervical spine of each subject underwent magnetic resonance image (MRI) scanning for construction of three dimensional (3D) vertebrae models from C3 to C7. The cervical spine was then imaged using a dual fluoroscopic system while the subject performed a dynamic flexion-extension neck motion in a sitting position. The 3D vertebral models and the fluoroscopic images were used to reproduce the in vivo vertebral motion. The dimensions (area, height and width) were measured for each cervical neuroforamen (C3/C4, C4/C5, C5/C6 and C6/C7) in the following functional positons: neutral positon, maximal flexion and maximal extension. Repeated measures ANOVA and post-hoc analysis were used to examine the differences between levels and positions. Results Compared with the neutral position, almost all dimensional parameters (area, height and width) of the sub-axial cervical neuroforamen decreased in extension and increased in flexion, except the neuroforaminal area at C5/C6 (P=0.07) and the neuroforaminal height at C6/C7 (P=0.05) remained relatively constant from neutral to extension. When comparisons of the overall change from extension to flexion were made between segments, the overall changes of the neuroforaminal area and height revealed no significant differences between segments, the width overall change of the upper levels (C3/C4 and C4/C5) was significantly greater than the lower levels (C5/C6 and C6/C7) (P<0.01). Conclusions The dimensional changes of the cervical neuroforamen showed segment-dependent characteristics during the dynamic flexion-extension. These data may have implications for diagnosis and treatment of patients with cervical radiculopathy.

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A TDFA is often cited as a major analysis needed when developing a new system. However, designing new components for pre-existing U.S. Navy systems presents a unique challenge. This paper describes the application of a modified TDFA to an existing system with new capabilities and functionality. New technologies introduced in the ABMD Baseline 5.1 include the Standard Missile (SM)-3 Block (Blk) IIA, which will provide superior speed, range, and discrimination capabilities relative to earlier SM-3 missile variants. This will lead to better performance against existing threats as well as entirely new mission capabilities. However, the areas impacted by this technology comprise a small subset of the overall AEGIS Weapon System functionality. As a result, a hybrid methodology for the TDFA was developed collaboratively by industry and government teams to ensure that outputs fit into the systems engineering process and ultimately the display design process. The hybrid TDFA methodology was developed as a means to help identify the information considered necessary to support warfighter decision making during mission planning and the ability to achieve the mission goal of successful ballistic missile threat kills during mission execution. An example is provided that shows how the hybrid methodology has impacted the development of prototype displays to date. It is concluded that this hybrid TDFA approach has demonstrated utility in the development of lower level requirements for these displays and is recommended for use when the system is already well-known and only a portion of the system in design will be considered new or changed functionality.

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BACKGROUND CONTEXT-Previous studies have reported position-dependent changes of the lumbar intervertebral foramen (LIVF) dimensions at different static flexion-extension postures. However, the changes of the LIVF dimensions during dynamic body motion have not been reported. PURPOSE-The objective of this study was to investigate the in-vivo dimensions of the LIVF during a dynamic weight-lifting activity. STUDY DESIGN/SETTING-A retrospective study. METHODS-Ten asymptomatic subjects were recruited for this study. 3D vertebral models of the lumbar segments from L2 to S1 were constructed for each subject using MR images. The lumbar spine was then imaged using a dual fluoroscopic imaging system as the subject performed a dynamic weight-lifting activity from an upper body position of 45° to a maximal extension position. The in-vivo positions of the vertebrae along the motion path were reproduced using the 3D vertebral models and the fluoroscopic images. The minimal area, height, and width of each LIVF during the dynamic body motion were analyzed. RESULTS-The LIVF area and width monotonically decreased with lumbar extension at all levels except L5-S1 (p < 0.05). On average, the LIVF area decreased by 7.4 ± 6.7 %,