Kinematics of the thoracic spine in trunk lateral bending: in vivo three-dimensional analysis

OCCUPATIONAL APPLICATIONSTrunk lateral bending and axial twisting are common in the workplace, and are associated with an increase in the risk of low back pain (LBP). We investigated the motions of the lumbar spine and pelvis during these activities, in a laboratory setting, and determined if there are age-related differences. No age-related differences were found in the ranges-of-motion of the lumbar spine or pelvis segment in the primary planes of motion during trunk lateral bending and axial twisting. There were, however, some important differences in coupled motions, outside of the primary planes of trunk motion; where such differences were evident, coupled motions were larger among older individuals. These age-related differences in lumbo-pelvic kinematics, together with earlier evidence of differences in the active and passive mechanical behavior of lower back tissues, imply age-related differences in spinal loads that may contribute to a differential risk of LBP.TECHNICAL ABSTRACT Background: Trunk lateral bending and axial twisting are associated with pelvic and lumbar motions that do not occur solely in the frontal and transverse planes, respectively; rather, there are components (coupled motions) in other anatomical planes. Purpose: We determined if there are age-related differences in the kinematics of the lumbar spine and pelvis in both primary and secondary planes during lateral bending and axial twisting. Methods: Ranges-of-motion (RoMs) in the lumbar spine and pelvis was measured in primary and secondary planes during trunk lateral bending and axial twisting, and compared between 71 participants in five age groups (aged 20–70 years). RoMs in secondary planes was normalized to values in the primary plane, and are reported as coupled motion ratios (CMRs). Results: Lumbar CMR in the transverse plane during lateral bending to left, and pelvic CMR in the sagittal plane during the axial twisting to right, were both significantly larger in older age groups. Additionally, lumbar CMR in the sagittal plane during the lateral bending to left, and pelvic RoM in the frontal plane during the lateral bending to both directions, were both larger among males. Conclusions: The observed age-related differences in lumbo-pelvic kinematics during trunk lateral bending and axial twisting likely impose different levels of risk for low back pain due to excessive spinal loads. The underlying sources of the age-related differences found here, particularly given known age-related differences in the active and passive mechanical behavior of lower back tissues, should be investigated in future work, along with their impacts on spinal loads.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P9. Potential proximal junctional kyphosis prophylaxis using a novel rib and transverse process band tethering technique in the thoracic spine: a biomechanical study

Kinematics of the cervical spine during lateral bending were investigated using a novel system of three-dimensional motion analysis. To demonstrate in vivo intervertebral coupled motions of the cervical spine during lateral bending of the neck. No previous studies have successfully documented in vivo three-dimensional intervertebral motions of the cervical spine during lateral bending. Twelve healthy volunteers underwent three-dimensional magnetic resonance imaging (MRI) of the cervical spine in 7 positions with 10 degrees increments of lateral bending. Relative motions of the cervical spine were calculated automatically by superimposing a segmented three-dimensional-MRI of the vertebra in the neutral position over images of each position using volume registration. Mean maximum lateral bending of the cervical spine to one side was 1.6 degrees to 5.7 degrees at each level. Coupled axial rotation opposite to lateral bending was observed in the upper cervical levels (Oc-C1, 0.2 degrees ; C1-C2, 17.1 degrees ), while in the subaxial cervical levels, it was observed in the same direction as lateral bending except for at C7-T1. Coupled flexion-extension motion was small at all vertebral levels (<1.1 degrees). We succeeded in identifying in vivo coupled motions of the cervical spine in lateral bending for the first time.

Influence of Sequential Ponte Osteotomies on the Human Thoracic Spine With a Rib Cage

Biomechanical Evaluation of a Novel Total Cervical Prosthesis in a Single-Level Cervical Subtotal Corpectomy Model: An In Vitro Human Cadaveric Study

It was recently reported that the epaxial muscles of a lizard, Varanus salvator, function to stabilize the trunk during locomotion, and it was suggested that this stabilizing role may be a shared derived feature of amniotes. This result was unexpected because it had previously been assumed that the epaxial muscles of lizards function to produce lateral bending during locomotion and that only in mammals and birds were the epaxial muscles active in stabilizing the trunk. These results and the inferences made from them lead to two questions. (1) Is the pattern of epaxial muscle activity observed in V. salvator representative of a basal lizard condition or is it a derived condition that evolved within lizards? (2) If the epaxial muscles do not produce lateral bending, which muscles do carry out this function? These questions were addressed by collecting synchronous electromyographic (EMG) and kinematic data from two lizard species during walking and running. EMG data were collected from the epaxial muscles of a lizard species from a basal clade, Iguana iguana, in order to address the first question. EMG data were collected from the hypaxial muscles of both Iguana iguana and Varanus salvator to address the second question. The timing of epaxial muscle activity in Iguana iguana relative to the kinematics of limb support and lateral trunk bending is similar to that observed in Varanus salvator, a finding that supports the hypothesis that the epaxial muscles stabilize the trunk during locomotion in lizards and that this stabilizing role is a basal feature of lizards. Therefore, a stabilizing function of the epaxial muscles is most parsimoniously interpreted as a basal amniote feature. In both Iguana iguana and Varanus salvator, the activity of two of the hypaxial muscles, the external oblique and rectus abdominis, is appropriately timed for the production of lateral bending. This indicates that elements of the hypaxial musculature, not the epaxial musculature, are the primary lateral bending muscles of lizards.

Stabilizing effect of the rib cage on adjacent segment motion following thoracolumbar posterior fixation of the human thoracic cadaveric spine: A biomechanical study

Thoracic spinal kinematics is affected by the grade of intervertebral disc degeneration, but not by the presence of the ribs: An in vitro study

Background: The most common problem in patient transfemoral short stump is lack of stability during walking and creates gait deviation. One of the things that can increase the stability is which socket that used. Socket is the most important part of prosthesis for increasing stability for the patient itself. Because of that really important to decide which socket that has gait deviation close to normal especially for patient transfemoral short stump. Objectives: To know which socket that has gait deviation especially for lateral trunk bending and abducted gait those close to normal gait for patient transfemoral short stump with using quadrilateral socket and IC socket. Methods: This research is using case study method. Sample of this research is patient transfemoral short stump, male, 54 years old. Patient asked for use quadrilateral socket and IC socket 2 days each. Observation of gait deviation is using recorder. Degree of lateral trunk bending and distance of abducted gait were measured by recording in 2nd meter until 6th meter. This research has done in Clinic ortothotics prosthetics Poltekkes Kemenkes Jakarta I. Results: Result of the research shows that socket that have gait deviation less than ideal normal espsecially degree of lateral trunk bending and distance of abducted gait is IC socket compare to quadrilateral socket. Degree of lateral trunk bending while using ic socket got 10,07° but for quadrilateral socket got 12,57° with ideal normal is 11,32°. Distance of abducted gait for IC sockets is 25,8 cm but quadrilateral is 29 cm with distance ideal normal is 27,4 cm. Conclusion: This research shows that there is any effect of difference sockets toward gait deviation especially lateral trunk bending and abducted gait for patient transfemoral short stump. From this research get results socket that better for patient transfemoral short stump is IC socket.

Spinal tumors and unstable vertebral body fractures usually require surgical treatment including vertebral body replacement. Regarding primary stability, however, the best possible treatment depends on the spinal region. The purpose of this in vitro study was to evaluate the effects of instrumentation length and approach size on thoracic spinal stability including the entire rib cage. Six fresh frozen human thoracic spine specimens with intact rib cages (C7-L1) were loaded with pure moments of 5 Nm in flexion/extension, lateral bending, and axial rotation, while monitoring the relative motions of all spinal segments using optical motion tracking. The specimens were tested (1) in the intact condition, followed by testing after vertebral body replacement at T6 level using a unilateral approach combined with (2) long instrumentation (T4–T8) and (3) short instrumentation (T5–T7) as well as a bilateral approach combined with (4) long and (5) short instrumentation. Significant increases of the range of motion (p < 0.05) were found in the entire thoracic spine (T1–T12) using the bilateral approach and short instrumentation in primary flexion/extension and in secondary axial rotation during primary lateral bending compared to both conditions with long instrumentation, as well as in secondary lateral bending during primary axial rotation compared to unilateral approach and long instrumentation. Compared to the intact condition, the range of motion was significantly decreased using unilateral approach and long instrumentation in flexion extension and secondary lateral bending during primary axial rotation, as well as using bilateral approach and long instrumentation in lateral bending. On the segmental level, the range of motion was significantly increased at T4–T5 level in lateral bending using unilateral approach and short instrumentation and significantly decreased using bilateral approach and long instrumentation compared to their respective previous conditions. Regardless of the approach type, which did not affect thoracic spinal stability in the present study, short instrumentation overall shows sufficient primary stability in the mid-thoracic spine with intact rib cage, while creating considerably more instability compared to long instrumentation, potentially being of importance regarding long-term implant failure. Moreover, short instrumentation could affect adjacent segment disease due to increased motion at the upper segmental level.

Biomechanical evaluation was performed to investigate the stability of the thoracic spine. Unilateral resection of the intervertebral disc, the rib head joint, and the costotransverse joint were sequentially performed, and nondestructive cyclic loading tests were conducted at each injury stage to examine the roles of the intervertebral disc and the costovertebral joint of the thoracic spine. The effects of each resection were three-dimensionally analyzed as the main motion and the associated coupled motions. To examine the role of the intervertebral disc and the costovertebral joint in stability of the thoracic spine. The effects of unilateral resection of the intervertebral disc and the costovertebral joints in the thoracic spine with the rib cage have not been documented three-dimensionally in a biomechanical study. Ten canine rib cage-thoracic spine complexes, consisting of the sixth to eighth ribs, the sternum and T5-T8 vertebrae, were used. Six pure moments along three axes, flexion-extension, lateral bending, and axial rotation, were applied to the specimen, and the angular deformation between T6-T7 was recorded by a stereophotogrammetric method. After the intact specimens were tested, staged resections were conducted in the following manner: partial resection of the T6-T7 intervertebral disc, performed as a resection of the anterior longitudinal ligament, the nucleus pulposus, and the annulus fibrosus on the approach side, leaving the posterior longitudinal ligament intact; resection of the right seventh rib head with the joint capsule; and resection of the right seventh costotransverse joint. At each stage, the main motion and associated coupled motions were determined three dimensionally. The ranges of motion (ROM) in flexion-extension, lateral bending, and axial rotation were significantly increased after partial discectomy (P < 0.01). Moreover, along with large increases in the ROM of the main motions in left axial rotation and right lateral bending, coupled motions, expressed by right lateral bending and left axial rotation, showed marked increases after resection of the rib head joint (P < 0.05). The neutral zones also increased in lateral bending, axial rotation, and flexion-extension after partial discectomy (P < 0.01). A further increase in the neutral zone was observed in lateral bending after resection of the right seventh rib head (P < 0.01). In this canine spine model, the intervertebral disc regulates the stability of the thoracic spine in flexion-extension, lateral bending, and axial rotation. Moreover, the articulation of the rib head with the vertebral bodies provides stability to the thoracic spine in lateral bending and axial rotation. Unilateral resection of the rib head joint after partial discectomy on the same side produces significant coupled motions in lateral bending and axial rotation, resulting in a significant decrease in thoracic spinal stability, and integrity.

Effect of Slope Degree on the Lateral Bending in Gekko geckos

Classic biomechanical models have used thoracic spines disarticulated from the rib cage, but the biomechanical influence of the rib cage on fracture biomechanics has not been investigated. The well-accepted construct for stabilizing midthoracic fractures is posterior instrumentation 3 levels above and 2 levels below the injury. Short-segment fixation failure in thoracolumbar burst fractures has led to kyphosis and implant failure when anterior column support is lacking. Whether shorter constructs are viable in the midthoracic spine is a point of controversy. The objective of this study was the biomechanical evaluation of a burst fracture at T-9 with an intact rib cage using different fixation constructs for stabilizing the spine. A total of 8 human cadaveric spines (C7-L1) with intact rib cages were used in this study. The range of motion (ROM) between T-8 and T-10 was the outcome measure. A robotic spine testing system was programmed to apply pure moment loads (± 5 Nm) in lateral bending, flexion-extension, and axial rotation to whole thoracic specimens. Intersegmental rotations were measured using an optoelectronic system. Flexibility tests were conducted on intact specimens, then sequentially after surgically induced fracture at T-9, and after each of 4 fixation construct patterns. The 4 construct patterns were sequentially tested in a nondestructive protocol, as follows: 1) 3 above/2 below (3A/2B); 2) 1 above/1 below (1A/1B); 3) 1 above/1 below with vertebral body augmentation (1A/1B w/VA); and 4) vertebral body augmentation with no posterior instrumentation (VA). A repeated-measures ANOVA was used to compare the segmental motion between T-8 and T-10 vertebrae. Mean ROM increased by 86%, 151%, and 31% after fracture in lateral bending, flexion-extension, and axial rotation, respectively. In lateral bending, there was significant reduction compared with intact controls for all 3 instrumented constructs: 3A/2B (-92%, p = 0.0004), 1A/1B (-63%, p = 0.0132), and 1A/1B w/VA (-66%, p = 0.0150). In flexion-extension, only the 3A/2B pattern showed a significant reduction (-90%, p = 0.011). In axial rotation, motion was significantly reduced for the 3 instrumented constructs: 3A/2B (-66%, p = 0.0001), 1A/1B (-53%, p = 0.0001), and 1A/1B w/VA (-51%, p = 0.0002). Between the 4 construct patterns, the 3 instrumented constructs (3A/2B, 1A/1B, and 1A/1B w/VA) showed comparable stability in all 3 motion planes. This study showed no significant difference in the stability of the 3 instrumented constructs tested when the rib cage is intact. Fractures that might appear more grossly unstable when tested in the disarticulated spine may be bolstered by the ribs. This may affect the extent of segmental spinal instrumentation needed to restore stability in some spine injuries. While these initial findings suggest that shorter constructs may adequately stabilize the spine in this fracture model, further study is needed before these results can be extrapolated to clinical application.

ABSTRACTBackgroundLenke type 1 is the most common adolescent idiopathic scoliosis (AIS), and its sagittal morphology critically influences progression and treatment. However, its biomechanical characteristics across Roussouly types remain unclear.PurposeTo quantify the biomechanical responses of Lenke type 1 AIS under pure bending moments across different Roussouly classifications.MethodsThis study was based on a validated thoracolumbar finite element model. Using mesh morphing, spinal alignments and vertebral rotations were adjusted to construct finite element models of Lenke type 1 AIS with Roussouly types 1–4. Simulations were conducted under ±7.5 Nm pure bending moments for flexion‐extension, lateral bending, and axial rotation. Spinal range of motion (ROM) and intervertebral disc loadings—including force, moment, and Von Mises stress—were quantified.ResultsCompared to the normal model, the AIS model showed asymmetrical total ROM at the T7–T12 segment, whereas the T1–S1 segment remained relatively symmetrical. At the T9–T10 and T12–L1 discs, shear and compressive forces increased markedly, with peak values of 197 N and secondary moments reaching ~2.8 Nm. Stress in the T9–T10 disc exhibited a distinct concave‐side concentration, with the maximum Von Mises stress reaching 7.7 MPa. The T1–S1 ROM during extension, right bending, and right rotation in Roussouly 1 and 2 was ~10% greater than in Roussouly 3 and 4, with markedly higher shear and compressive forces (up to 50‐fold) at the T6–T7 and T9–T10 discs. Regarding stress distribution, Von Mises stress at the T6–T7 and T9–T10 discs was higher in Roussouly 3 and 4, whereas stress at the T12–L1 disc was more pronounced in Roussouly 1 and 2.ConclusionThe findings underscore the critical role of sagittal morphology in AIS biomechanics. Compared to Roussouly 1 and 2, Roussouly 3 and 4 exhibited reduced ROM, lower disc forces, and more favorable stress distributions, suggesting a biomechanically advantageous load‐bearing pattern.

Global rotations of the cervical spine during arm flexion