ABSTRACT Changes in load transmission through facet and facet orientation have been considered as... more ABSTRACT Changes in load transmission through facet and facet orientation have been considered as an important factor in intervertebral disc degeneration and osteoarthritic changes of the facet joint. (1)(2)(3) Facet joint surface area and orientation of the facets play key roles in load transmission. Their information is important for designing implants of the spine. They have been 2-dimentionally measured using CT and MRI. (4)(5) The purpose of the current study was to establish a three-dimensional (3D) technique for measuring lumbar facet joint area and orientation in vivo.
In a laboratory study, 21 human lumbar spine segments were used to determine whether intraosseous... more In a laboratory study, 21 human lumbar spine segments were used to determine whether intraosseous pressure increases occur during axial-compressive loading conditions under two displacement rates. To determine whether an intraosseous pressure rise is associated with burst fracture formation. Burst fractures are high-speed injuries usually associated with neurologic deficit. An internal pressure rise has been implicated as a critical factor in burst fracture formation. The authors hypothesize that the internal pressure increases with increasing input velocity. The internal pressure changes were measured in spine segments using two displacement rates: 10 mm/s (slow speed) and 2500 mm/s (high speed). Failure load and energy absorption were determined for both groups. The resultant fracture types were determined from postinjury radiographs. The initial peak internal pressure decreased from slow- to high-speed tests (P < 0.01). Overall peak pressure, failure load, and energy absorbed at failure were not significantly different. Slow-speed tests resulted in compression fractures, whereas high-speed tests resulted in burst and compression fractures. The current research did not support the current theory of burst fracture formation. There was a decrease in measured internal pressure from the slow- to high-speed groups, and burst fractures still were produced. The theory could be potentially modified to suggest that the nucleus entering the vertebral body acts as a wedge, splitting the vertebral body apart and enabling the bony fragments to be pushed into the canal space.
Fifteen asymptomatic volunteers were externally rotated and CT scanned to determine lumbar segmen... more Fifteen asymptomatic volunteers were externally rotated and CT scanned to determine lumbar segmental motion. To measure three-dimensional segmental motion in vivo using a noninvasive measurement technique. Spinal instability has been implicated as a potential cause of low back pain, especially, axial rotational instability. Typically, flexion-extension lateral radiographs were used to quantify instability, but inaccurately measured translations and inability to capture out-of-plane rotations are limitations. Using a custom-calibrated rotation jig, L1-S1 CT reconstructions were created of volunteers in each of 3 positions: supine and left and right rotations of the torso with respect to the hips. Segmental motions were calculated using Euler angles and volume merge methods in three major planes. Segmental motions were small (< 4 degrees or 6 mm) with the greatest motions seen in axial rotation (range, 0.6 degrees to 2.2 degrees ), lateral bending (range, -3.6 degrees to 3.0 degrees ), and frontal translation (-1.2 mm to 5.4 mm). Largest motions were in the levels: L1-L2 to L3-L4. Complex coupled motions were measured due to external torsion and could be indicative of instability chronic patients with low back pain. The presented data provide baseline segmental motions for future comparisons to symptomatic subjects.
INTRODUCTION Spinal instability has been suggested as a potential cause of low back pain and axia... more INTRODUCTION Spinal instability has been suggested as a potential cause of low back pain and axial rotational instability, in particular, has been implicated in its pathogenesis due to the presence of disc degeneration (DD) [1]. The use of radiographs has been under scrutiny ...
Twenty-one intact human lumbar vertebral bodies (L3 and L4) were used to determine the changes in... more Twenty-one intact human lumbar vertebral bodies (L3 and L4) were used to determine the changes in measured intraosseous pressure for 2 volumetric flow rates and to calculate hydraulic resistance in both cases. To evaluate changes in hydraulic resistance in intact vertebral bodies under different rates of flow. Hydraulic resistance has been implicated in the creation of high-speed vertebral injuries, such as burst fracture, but no previous study has measured hydraulic resistance under high-speed loading conditions. Previous work in whole bone preparations showed that hydraulic resistance was constant under low-speed conditions. The authors hypothesized that: (1) measured pressure would increase with increasing input flow rates, and (2) hydraulic resistance would remain constant at increased input flow rates. Using 2 input velocity conditions (10 mm/s and 2500 mm/s), resultant pressures were measured and hydraulic resistance calculated. Trabecular architecture was determined using micro-computerized tomography after testing. Measured pressure increased with increasing input flow rates. However, average hydraulic resistance decreased significantly when comparing low-speed (3.40 +/- 1.58kPa*s/mL) and high-speed (0.16 +/- 0.08kPa*s/mL) groups. Current hydraulic resistance results contradict previous findings. The observed decrease in hydraulic resistance suggests that, during high-speed injury events, marrow flow may damage the trabeculae and thereby weaken the vertebra.
ABSTRACT Changes in load transmission through facet and facet orientation have been considered as... more ABSTRACT Changes in load transmission through facet and facet orientation have been considered as an important factor in intervertebral disc degeneration and osteoarthritic changes of the facet joint. (1)(2)(3) Facet joint surface area and orientation of the facets play key roles in load transmission. Their information is important for designing implants of the spine. They have been 2-dimentionally measured using CT and MRI. (4)(5) The purpose of the current study was to establish a three-dimensional (3D) technique for measuring lumbar facet joint area and orientation in vivo.
In a laboratory study, 21 human lumbar spine segments were used to determine whether intraosseous... more In a laboratory study, 21 human lumbar spine segments were used to determine whether intraosseous pressure increases occur during axial-compressive loading conditions under two displacement rates. To determine whether an intraosseous pressure rise is associated with burst fracture formation. Burst fractures are high-speed injuries usually associated with neurologic deficit. An internal pressure rise has been implicated as a critical factor in burst fracture formation. The authors hypothesize that the internal pressure increases with increasing input velocity. The internal pressure changes were measured in spine segments using two displacement rates: 10 mm/s (slow speed) and 2500 mm/s (high speed). Failure load and energy absorption were determined for both groups. The resultant fracture types were determined from postinjury radiographs. The initial peak internal pressure decreased from slow- to high-speed tests (P < 0.01). Overall peak pressure, failure load, and energy absorbed at failure were not significantly different. Slow-speed tests resulted in compression fractures, whereas high-speed tests resulted in burst and compression fractures. The current research did not support the current theory of burst fracture formation. There was a decrease in measured internal pressure from the slow- to high-speed groups, and burst fractures still were produced. The theory could be potentially modified to suggest that the nucleus entering the vertebral body acts as a wedge, splitting the vertebral body apart and enabling the bony fragments to be pushed into the canal space.
Fifteen asymptomatic volunteers were externally rotated and CT scanned to determine lumbar segmen... more Fifteen asymptomatic volunteers were externally rotated and CT scanned to determine lumbar segmental motion. To measure three-dimensional segmental motion in vivo using a noninvasive measurement technique. Spinal instability has been implicated as a potential cause of low back pain, especially, axial rotational instability. Typically, flexion-extension lateral radiographs were used to quantify instability, but inaccurately measured translations and inability to capture out-of-plane rotations are limitations. Using a custom-calibrated rotation jig, L1-S1 CT reconstructions were created of volunteers in each of 3 positions: supine and left and right rotations of the torso with respect to the hips. Segmental motions were calculated using Euler angles and volume merge methods in three major planes. Segmental motions were small (< 4 degrees or 6 mm) with the greatest motions seen in axial rotation (range, 0.6 degrees to 2.2 degrees ), lateral bending (range, -3.6 degrees to 3.0 degrees ), and frontal translation (-1.2 mm to 5.4 mm). Largest motions were in the levels: L1-L2 to L3-L4. Complex coupled motions were measured due to external torsion and could be indicative of instability chronic patients with low back pain. The presented data provide baseline segmental motions for future comparisons to symptomatic subjects.
INTRODUCTION Spinal instability has been suggested as a potential cause of low back pain and axia... more INTRODUCTION Spinal instability has been suggested as a potential cause of low back pain and axial rotational instability, in particular, has been implicated in its pathogenesis due to the presence of disc degeneration (DD) [1]. The use of radiographs has been under scrutiny ...
Twenty-one intact human lumbar vertebral bodies (L3 and L4) were used to determine the changes in... more Twenty-one intact human lumbar vertebral bodies (L3 and L4) were used to determine the changes in measured intraosseous pressure for 2 volumetric flow rates and to calculate hydraulic resistance in both cases. To evaluate changes in hydraulic resistance in intact vertebral bodies under different rates of flow. Hydraulic resistance has been implicated in the creation of high-speed vertebral injuries, such as burst fracture, but no previous study has measured hydraulic resistance under high-speed loading conditions. Previous work in whole bone preparations showed that hydraulic resistance was constant under low-speed conditions. The authors hypothesized that: (1) measured pressure would increase with increasing input flow rates, and (2) hydraulic resistance would remain constant at increased input flow rates. Using 2 input velocity conditions (10 mm/s and 2500 mm/s), resultant pressures were measured and hydraulic resistance calculated. Trabecular architecture was determined using micro-computerized tomography after testing. Measured pressure increased with increasing input flow rates. However, average hydraulic resistance decreased significantly when comparing low-speed (3.40 +/- 1.58kPa*s/mL) and high-speed (0.16 +/- 0.08kPa*s/mL) groups. Current hydraulic resistance results contradict previous findings. The observed decrease in hydraulic resistance suggests that, during high-speed injury events, marrow flow may damage the trabeculae and thereby weaken the vertebra.
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