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Low back pain (LBP) is a substantial secondary disability among persons with lower-limb amputation (LLA). Abnormal mechanics of movement subsequent to LLA may increase the stability demands on the spinal column, and repetitive exposures to such abnormal movements may alter trunk passive properties and/or the coordination of surrounding trunk muscle responses. Further, preferential use of the sound limb may lead to asymmetries in these behaviors. Spine biomechanics (e.g., loading and stability) are substantially influenced by trunk passive properties and neuromuscular control, and alterations in these behaviors are associated with abnormal mechanics of the spinal column and an increased LBP risk. However, there is limited evidence regarding whether prolonged repeated exposures to abnormal gait and movement resulting from LLA and subsequent repeated use of a prosthetic device affect these trunk behaviors. Eight males with unilateral LLA and a matched sample of non-amputation controls completed three studies in which several measures of trunk passive properties, neuromuscular control, and spine biomechanics were quantified using laboratory experiments and biomechanical analyses. Each study involved a distinct task to investigate potential alterations and/or asymmetries in trunk passive properties and neuromuscular control. The first study used a seated balance task to assess trunk postural control and stability. The second study used multidirectional trunk perturbations to assess trunk mechanical and neuromuscular behaviors. Finally, the third study used controlled quasi-static trunk movements to assess load-sharing mechanisms between active and passive low back tissues. Significant alterations and asymmetries in trunk passive properties and trunk neuromuscular responses were present among participants with LLA, specifically reduced and asymmetric trunk stiffness and reflex response; decreased and asymmetric passive contributions to trunk movements; and increased trunk muscle activities. Significant increases in trunk postural sway and trunk muscle activities were also present during seated stability measures. Such alterations in these behaviors may be a result of repetitive exposures to abnormal gait and movement subsequent to LLA and the use of a prosthetic device, and could play a contributing role in the development of LBP in this population. Future work should investigate the temporal relationship between altered trunk behaviors and repeated exposure to abnormal gait and movement subsequent to LLA, to better identify critical years for rehabilitation and preventative care. / Ph. D.

Pathologic processes and surgical manipulations of the spinal column may result in alterations of the biomechanical properties of the spine through increases or decreases in the range of motion or stability of the spine. A decrease in range of motion between two adjacent vertebrae subsequent to arthrodesis or ankylosis appears, clinically, to be well tolerated without significant alterations to the functions of the spine; however, a decrease in spinal column stability as a result of pathologic changes or surgical alterations can result in catastrophic spinal cord injury. In order to determine the effect of various surgical procedures and trauma on the spinal column, in vitro biomechanical studies may be employed using a servohydraulic testing apparatus and cadaver vertebral motion units. The T₁₃ - L₁ vertebral motion units of 48 mix breed dogs were dissected free of surrounding musculature and prepared for biomechanical testing by mounting with cross pins and polymethylmethacrylate. Specimens were surgically altered by facetectomy, lateral fenestration, diskectomy, and combinations of these procedures. Specimens were subjected to lateral bending at a rate of 2.5 cm per minute to failure in a swing arm bending jig designed to simulate four point bending. The slopes of bending moment vs. angular displacement curves were compared and significance determined by the method of least squares. A statistical difference (p < 0.05) was found between the stiffness of all diskectomy groups when compared to any other group. Unilateral and bilateral facetectomies, and fenestration induced a non-significant decrease in stiffness in comparison to control specimens. This data may be combined with that of previous testing of the canine thoracolumbar spine in flexion-extension and rotation to determine the clinical effects of surgical manipulations and trauma on spinal stability. These results suggest that fenestrations and facetectomies do not appear to increase the risk of injury to the canine thoracolumbar spinal cord during lateral bending in the in vitro model; however, thoracolumbar spinal fractures involving the vertebral body as represented by the diskectomy in vitro model may significantly destabilize the spine in lateral bending. / Master of Science

Degeneration of the cervical spine is part of the normal aging process, usually occurring without clinical symptoms. Symptomatic degeneration most often occurs in the lower cervical spine, presenting as axial neck pain, radiculopathy, myelopathy, or any combination of the three. When conservative treatment does not adequately manage these symptoms, surgical intervention may be required. The longstanding surgical treatment for cervical degeneration is arthrodesis achieved through anterior cervical discectomy and fusion (ACDF). A relatively newer treatment is arthroplasty with a cervical total disc replacement (CTDR), a motion-sparing procedure designed to maintain adjacent-level loading. While literature exists comparing the effects of cervical arthrodesis and cervical arthroplasty on neck kinematics and loading, the vast majority of these studies applied only quasi-static, non-injurious loading conditions. This dissertation research used a state-of-the-art, full body human finite element (FE) model to investigate the effects of these surgical procedures on neck response during simulated dynamic impacts. A method was developed to measure cross-sectional forces and moments at each level of the neck in the FE model. Neck loading was captured during three automobile impact simulations: a frontal impact of a belted driver with airbag deployment, a frontal impact of a belted passenger without airbag deployment, and an unbelted side impact. The measured neck forces and moments were compared to existing injury threshold values and used to calculate injury criteria values. Four additional simulations of the frontal impact with the belted driver were conducted with neck modifications representative of either a fusion or arthroplasty of C5-6. While cross-sectional loading above and below the implants did not vary appreciably, key differences were noted in both the interbody and facet response. However, no neck injury thresholds were exceeded in any of the simulations. With cervical radiculopathy diagnosed in 24,742 active-duty U.S. military personnel between 2000 and 2009, interest in cervical arthroplasty as treatment for symptomatic cervical degeneration in this population has increased. This motion-sparing procedure has the potential to expedite post-operative recovery time, allowing for these highly trained individuals to return to active-duty sooner than with a fusion. Due to the physically demanding nature of the military environment, it is important to ensure that this surgical procedure does not increase the likelihood of a neck injury. An FE simulation environment was developed to investigate aviator head and neck response during a survivable, rotary-wing aircraft impact with the ground using both an anthropomorphic test device (ATD) and a human body model. The head and neck response of the ATD FE simulation was successfully validated against the results of a previously conducted experimental sled test. A more biofidelic head and neck response was produced with the human body model, including realistic changes in neck curvature. Additional simulations were conducted with the human body model to investigate the neck response after cervical arthroplasty of C5-6. While the adjacent-level, cross-sectional loading for the C5-6 segment was not appreciably altered by the CTDRs, the interbody range-of-motion was increased; subsequently altering both the interbody and cervical facet loading. Again, no neck injury thresholds were exceeded in these simulations. Overall, cervical arthroplasty did not appear to have a deleterious effect on the dynamic neck response during a simulated rotary-wing aircraft impact. / Ph. D.

Yes / Rugby Union and Rugby League are popular sports with high participation across the world. The high impact nature of the sport results in a high proportion of injuries. Rugby has an association with cervical spine injury which has potentially catastrophic consequences for the patient. Anecdotal evidence suggests that radiographers find it challenging to visualise the cervicothoracic junction on the lateral supine cervical spine projection in broad shouldered athletes. This paper intends to analyse the risk factors for cervical spine injuries in rugby and discuss the imaging strategy in respect to radiography and CT scanning in high risk patient groups such as rugby players who are suspected of suffering a cervical spine injury.

Yes / Lumbar radiographs remain a common imaging examination despite strategies to reduce their use. Many authors have demonstrated benefits in changing from traditional supine and recumbent lateral projections to a prone and/or erect orientation. Despite evidence of clinical and radiation dose optimisation, widespread adoption of these strategies has stalled. This article describes the single-centre implementation and evaluation of erect PA and lateral projections. This was an observational study pre- and post-implementation of an erect imaging protocol. Patient BMI, image field size, source image and source object distances and DAP were collected together with assessment of radiographic spinal alignment and disc space demonstration. Effective dose was calculated with organ specific doses. 76 (53.5%) patients were imaged in the supine AP and recumbent lateral position, 66 (46.5%) had erect PA and lateral radiographs. Despite the larger BMI of the erect cohort and similar field sizes, effective dose was lower in the PA position by an average of 20% (p / The full-text of this article will be released for public view at the end of the publisher embargo on 13 May 2024.

The stability of the spine can be estimated from kinematic variability and nonlinear analyses of seated balance tasks. However, processing methods require sufficient signal duration and test-retest experiments require that the assessment must be reliable. Our goal was to characterize the reliability and establish the trial duration for spine stability assessment. Stationarity, kinematic variability and nonlinear dynamic stability were quantified from kinetic and kinematic data collected during balance performance. Stationarity results showed that a minimum 30 seconds test duration is necessary. Intra-session reliability was excellent, however inter-session reliability needed more test trials to achieve excellent reliability. Few studies have investigated the spinal stability during pushing and pulling exertions. Past studies suggest that the spine can be stabilized by paraspinal muscle stiffness as well as reflexes. We hypothesized that the stability of the spine decreases with exertion force and decreases during pushing more than during pulling exertion. Kinematic variability and nonlinear dynamic stability measurements were quantified from the balance performance during isometric pushing and pulling tasks. Results demonstrated that spinal stability decreased with exertion force and decreased a greater amount during pushing task than during pulling task. Stiffness alone may be insufficient to stabilize the trunk. Results may be able to be explained by slower reflex delay. The results suggested that pushing and pulling exertions have a potential risk of low-back disorders. / Master of Science

Few studies have investigated the neuromuscular recruitment and stabilizing control of the spine during pushing and pulling exertions. Past theoretical investigation suggest that co-contraction of the of the paraspinal muscles is necessary to stabilize the spine during pushing exertions. We hypothesized greater levels of co-contraction during pushing exertions. Co-contraction of trunk musculature was quantified during isometric pushing and pulling tasks. The mean value of co-contraction during pushing was two-fold greater (p < 0.01) than during extension. Co-contraction has been shown to increase the stiffness of the ankle but this effect has not been demonstrated in the trunk. Trunk stiffness was measured as a function of co-activation during extension exertions. Results demonstrate trunk stiffness was significantly (p < 0.01) greater with co-activation. Trunk stiffness was calculated during isometric pushing and pulling exertions. We hypothesized trunk stiffness would be greater during pushing tasks due to increased levels of co-contraction to maintain stability of the spine. Results demonstrate trunk stiffness was significantly (p < 0.05) greater during pushing compared to pulling exertions. Results suggest that trunk isometric pushing tasks require more co-contraction than pulling tasks enable to maintain spinal stability. Greater levels of co-contraction during pushing exertions caused trunk stiffness to be greater during pushing compared to pulling tasks. Results may indicate greater risk of spinal instability from motor control error during pushing tasks than pulling exertions. Future studies need to consider co-contraction and neuromuscular control of spinal stability when evaluating the biomechanical risks of pushing and pulling tasks. / Master of Science

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