EFFECTS OF LUMBAR SPINAL FUSION ON LUMBOPELVIC RHYTHM DURING ACTIVITIES OF DAILY LIVING

Abnormalities in lumbopelvic rhythm (LPR) play a role in occurrence/recurrence of low back pain (LBP). The LPR before spinal fusion surgery and its changes following the surgery are not understood. A repeated measure study was designed to investigate timing and magnitude aspects of LPR in a group of patients (n = 5) with LBP before and after a spinal fusion surgery. Participants completed a forward bending and backward return task at their preferred pace in the sagittal plane. The ranges of thoracic and pelvic rotations and lumbar flexion (as the magnitude aspects of LPR) as well as the mean absolute relative phase (MARP) and deviation phase (DP) between thoracic and pelvic rotations (as the timing aspects) were calculated. Thoracic, pelvic, and lumbar rotations/flexion were respectively 2.19° smaller, 17.69° larger, and 19.85° smaller after the surgery. Also, MARP and DP were smaller during both bending (MARP: 0.0159; DP 0.009) and return (MARP: 0.041; DP: 0.015) phases of the motion after surgery. The alterations in LPR after surgery can be the result of changes in lumbar spine structure due to vertebral fusion and/or new neuromuscular adaptations in response to the changes of lumbar spine structure. The effects of altered LPR on load sharing between passive and active components of lower back tissues and the resultant spinal loads should be further investigated in patients with spinal fusion surgery

Lumbar Posture and Tissue Loading During Short-Term Static Trunk Bending

Low back pain (LBP) is among the most prevalent occupational health problems worldwide and is a leading cause of lost work days. Previous studies have suggested that static prolonged trunk bending could generate lumbar muscle fatigue and introduce creep to the lumbar posterior tissues. Such physical changes could lead to alterations to the lumbar active and passive tissue sharing mechanism and also elevate spinal loading, which is highly associated with the risk of LBP. In the past, most occupational ergonomic studies focused on the instantaneous spine biomechanical responses during task performance. A few studies assessed the changes of spine biomechanics due to spinal tissue creep (introduced by prolonged trunk full flexion) and lumbar muscle fatigue (introduced by prolonged or repetitive trunk bending). However, the dynamic changes of lumbar and trunk postures and spinal tissue loadings during the performance of relatively short-term trunk bending tasks are still unclear. Therefore, the purpose of the current study was to investigate the changes of lumbar biomechanics during short-term, sustained trunk bending.;In the present study, fifteen participants performed short-term (40 seconds) static trunk bending tasks in two different trunk postures (30° or 60°) with two different hand load levels (0 or 15lbs). Results of the current study revealed significant reduction of lumbar muscle activities during the course of task performance. This change was coupled with significant increase of lumbar flexion angle and lumbar passive moment. Such increase of lumbar passive tissue loading could help relief/delay lumbar muscle fatigue by compensating the reduced lumber active tissue loading. Findings of this study suggest that, during the performance of sustained trunk bending, there is an internal mechanism to shift loading from lumbar active tissues to passive tissues by increasing the lumbar flexion. This mechanism is beneficial in reducing the amount of lumbar muscle fatigue; however, lumbar passive tissue creep could be generated at a faster rate

Low Back Pain (LBP)

Low back pain (LBP) is a major public health problem, being the most commonly reported musculoskeletal disorder (MSD) and the leading cause of compromised quality of life and work absenteeism. Indeed, LBP is the leading worldwide cause of years lost to disability, and its burden is growing alongside the increasing and aging population. The etiology, pathogenesis, and occupational risk factors of LBP are still not fully understood. It is crucial to give a stronger focus to reducing the consequences of LBP, as well as preventing its onset. Primary prevention at the occupational level remains important for highly exposed groups. Therefore, it is essential to identify which treatment options and workplace-based intervention strategies are effective in increasing participation at work and encouraging early return-to-work to reduce the consequences of LBP. The present Special Issue offers a unique opportunity to update many of the recent advances and perspectives of this health problem. A number of topics will be covered in order to attract high-quality research papers, including the following major areas: prevalence and epidemiological data, etiology, prevention, assessment and treatment approaches, and health promotion strategies for LBP. We have received a wide range of submissions, including research on the physical, psychosocial, environmental, and occupational perspectives, also focused on workplace interventions

Lumbar spine kinematics and kinetics during heavy barbell squat and deadlift variations

Purpose: The primary purpose of this research was to compare barbell deadlifts and squats, as well as two technique variations within each lift, for their effects on lumbar spine kinematics and kinetics. The techniques compared within the deadlift condition were the low-hip deadlift (LHDL) and the high-hip deadlift (HHDL). The techniques compared within the squat condition were the high-bar squat (HBS) and low-bar squat (LBS). The outcome variables measured were peak lumbar flexion, L4-L5 and L5-S1 moments, and L5-S1 joint reaction force. Methods: Data were collected and reported on 17 healthy competitive strength athletes (male = 12, female = 5, age = 26.5 ± 4.7 years, height = 176.1 ± 4.6 cm, body mass = 97.7 ± 22.3 kg). Participants completed three single lifts at 85% of their estimated one-repetition maximum using each lifting technique during a single session. Data were collected using an 8-camera 3D motion capture system and two in-ground force plates then processed using custom Matlab routines. Lumbar flexion was calculated using a custom kinematic driven lumbar spine model. Joint moments were calculated using inverse dynamics. Joint reaction force calculations were based on an equilibrium approach using a single-equivalent muscle model. A 2×2 factorial ANOVA with the factors of lift type (deadlift vs squat) and bar position (anterior vs posterior) was used to determine the effect of each main lift on the outcome variables. Significance for the ANOVA was set at p<.01. Planned paired samples t-test’s were used to compare the effects of lift technique (LHDL vs HHDL and HBS vs LBS) on the outcome variables. Significance was set at p<01. Results: Peak lumbar flexion, expressed as a percentage of maximal voluntary flexion, was significantly greater during the deadlift condition (76.76 ± 16.07%) in comparison to the squat condition (64.2 ± 19.8%, p = .005). Within the squat condition, peak lumbar flexion was significantly greater for the LBS technique (67.9 ± 19.7%) when compared to the HBS technique (60.43% ± 19.79, p<.001). Normalized L5-S1 joint reaction force results displayed that within the deadlift condition, there was significantly greater average shear force during the LHDL technique (2.02 ± 0.23N) in comparison to the HHDL technique (1.98 ± 0.22N, p=.004). Within the squat condition, there was significantly greater peak shear force during the HBS technique (2.59 ± 0.42N) in comparison to the LBS technique (2.47 ± 0.40N, p<.001). Significant differences were not observed between or within lifting conditions for any of the other variables. Conclusion: This is the first study to directly compare lumbar flexion and L5-S1 joint reaction forces between the barbell deadlift and squat, as well as the HHDL/LHDL and HBS/LBS technique variations within each lift. Results suggest that if normalized to barbell load, barbell squats create equivalent loading at the L5-S1 joint when compared to the deadlift. They also suggest significant differences in peak lumbar flexion and peak shear joint reaction force when comparing the HBS and LBS. Past research on barbell squat kinematics have perpetuated the assumption that the torso remains relatively rigid during this exercise; however, these findings indicated the lumbar spine undergoes considerable flexion when squatting to a depth slightly below parallel. Furthermore, the amount of lumbar flexion taking place seems to be influenced by the squat technique used and this can lead to significant differences in peak L5-S1 shear joint reaction force, a variable believed to be related to low back injury

Investigation into the prevalence, spinal kinematics and management of adolescent male rowers with low back pain

This thesis investigated back pain in adolescent rowers. A high prevalence of low back pain was found in adolescent male rowers. Differences in lumbar spine movement patterns during ergometer rowing were observed between genders and in adolescent males with back pain compared to those without. A cognitive functional intervention was tested in a randomized controlled trial and was demonstrated to reduce pain and disability, improve muscle endurance and alter sitting spinal postures in adolescent male rowers

The effect of prolonged sitting on neuromuscular and biomechanical responses of the low back in healthy individuals

Background: Sub-maximally flexed spine postures have the potential to elicit creep (lengthening) in the posterior passive tissues of the spine leading to a delay in the normal muscle reflexes of the spine. This scenario could result in a low back injury when a sudden perturbation is experienced following a prolonged period of sitting. Methods: 17 men and 23 women were recruited to examine the effect sitting in an office chair had on the reflex onset times of muscles in the low back. Surface EMG of the low back, and lumbar spine and pelvic angles were collected continuously through all trials. Muscle reflexes were elicited immediately before and after exposure to 2 hours of sitting, and onset times were compared. Results: Low back muscle reflexes were non-significantly longer after sitting for two hours (72.89 ms ± 38.72) as compared to pre-sitting latencies (60.00 ms ± 27.77). No significant interactions or main effects of pain groups or sex were found for reflex times. Conclusion: Sitting for two-hours in an office chair does not appear to affect the ability of the low back muscles to respond to a sudden perturbation. This conclusion holds for males and females as well as those who develop transient sitting-induced pain. Future work should examine if longer periods of sitting and/or different chair conditions and spine postures induce delayed reflexes

Pain perception and stabilometric parameters in people with chronic low back pain after a pilates exercise program: A randomized controlled trial

Various exercise interventions, such as Pilates exercises and traditional physical therapy methods, are employed to decrease low back pain (LBP). Nonspecific low back pain (NSLBP) is distinct from LBP, however, as the distribution of pain is restricted to the region between the costal margin and the inferior gluteal. The aim of our randomized controlled trial was to evaluate the effects of a program of Pilates exercises on pain perception and stabilometric parameters in patients with NSLBP.Thirty-eight participants were randomly allocated, using a 1:1 scheme, to either the experimental group (EG) or control group (CG). The EG completed a 14-week program of Pilates exercises, performed thrice per week under the supervision of an exercise specialist, while the CG was managed with a social program only. Measures of posturography and Oswestry Disability Index (ODI) for pain perception were obtained at baseline (T0) and after the 14 weeks of intervention (T)1.Posturography measures improved for patients in the EG, with both eyes open and eyes closed (P\u200a<\u200a0.05). There were no statistical differences in posturography in the CG. ODI decreased significantly in both groups over the 14 weeks of the study protocol: EG, T0, 13.7\u200a\ub1\u200a5.0 compared with T1, 6.5\u200a\ub1\u200a4.0 (P\u200a<\u200a0.001); and CG, T0, 10.7\u200a\ub1\u200a7.8 compared with T1, 8.4\u200a\ub1\u200a7.8 (P\u200a<\u200a0.01). A greater extent of reduction in pain was achieved in the EG.The Pilates exercise program yielded improvements in pain and posturography outcomes. Our study also confirms the applicability of posturography in evaluating postural instability in patients with NSLBP. Due to our relatively small study group, future studies would be necessary to confirm our findings

Stereophotogrammetric approaches to multi-segmental kinematics of the thoracolumbar spine: a systematic review

Spine disorders are becoming more prevalent in today's ageing society. Motion abnormalities have been linked to the prevalence and recurrence of these disorders. Various protocols exist to measure thoracolumbar spine motion, but a standard multi-segmental approach is still missing. This study aims to systematically evaluate the literature on stereophotogrammetric motion analysis approaches to quantify thoracolumbar spine kinematics in terms of measurement reliability, suitability of protocols for clinical application and clinical significance of the resulting functional assessment

Axial twist loading of the spine: Modulators of injury mechanisms and the potential for pain generation.

There are several reasons to research the effects of axial twist exposures and the resulting loading on the spine. The lack of consensus from the limited work that has previously examined the role of axial twist moments and motions in the development of spine injuries or generation of low back pain is the primary reason. From recently published works, axial twist moments appear to represent an increased risk for injury development when it acts in concert with loading about other physiological axes (i.e. flexion, extension, and compression). However, there is a large body of epidemiologic data identifying axial twist moments and/or motion as risk factors for low back disorders and pain, demonstrating the need for this series of investigations. It is likely that these combined exposures increase risk through altering the spine’s load distribution (passive resistance) by modifying the mechanics, but this deduction and related causal mechanism need to be researched. The global objective of this research was focused on determining whether there is evidence to support altered load distribution in the spine, specifically between the intervertebral disc and facets, in response to applied axial twist moments (when added in combination with one and two axes of additional loading). Also included was whether these modes of loading can modify spine mechanics and contribute and/or alter the development of damage and pain. This objective was addressed through one in-vivo (Drake and Callaghan, 2008a– Chapter #2) and three in-vitro (Drake et al., 2008– Chapter #4; Drake and Callaghan, 2008b– Chapter #5; Drake and Callaghan, 2008c– Chapter #6) studies that: (1) Quantified the amount of passive twist motion in the lumbar spine when coupled with various flexion-extension postures; (2) Documented the effects of flexion-extension postures and loading history on the distance between the facet articular surfaces; (3) Evaluated the result of axial twist rotation rates on acute failure of the spine in a neutral flexion posture; and (4) Explored whether repetitive combined loading has the ability to cause enough deformation to the spine to generate pain. Through the combination of findings previously reported in the literature and the outcomes of Drake and Callaghan (2008a– Chapter #2) and Drake et al. (2008– Chapter #4), a postural mediated mechanism was hypothesized to be responsible for governing the load distribution between the facet joints and other structures of the spine (i.e. disc, ligaments). Increased flexed postures were found to decrease the rotational stiffness by resulting in larger twist angles for the same applied twist moment in-vivo relative to a neutral flexion posture (Drake and Callaghan, 2008a– Chapter #2). This suggested there might be an increased load on the disc due to a change in facet coupling in these combined postures. Similarly, increased angles were observed in flexed and twisted postures for in-vitro specimens relative to a neutral flexion posture. These observed differences were found to correspond with altered facet joint mechanics. Specifically that flexed twisted postures increased the inter-facet spacing relative to the initial state of facet articulation (Drake et al., 2008– Chapter #4). These finding supported the postulated postural mechanism. Therefore, in a neutral posture the facet joints likely resisted the majority of any applied twist moment based on the limited range of motion and higher axial rotational stiffness responses observed. It was suspected that the changes in mechanics would likely cause a change in the load distribution however the magnitude of change in load distribution remains to be quantified. Further support for this postulated postural mechanism comes from the mode of failure for specimens that were exposed to 10,000 cycles of 5° axial twist rotation while in a static flexed posture (Drake and Callaghan, 2008c– Chapter #6), and neutrally flexed specimens exposed to 1.5° of rotation for 10,000 cycles reported in the literature. Without flexion, the failure patterns were reported to occur in the endplates, facets, laminae and capsular ligaments, but not the disc. However, with flexion the repetitive axial twist rotational displacements caused damage primarily to the disc. If the load distribution was unchanged, the higher axial rotation angle should have caused the specimen to fail in less cycles of loading, and the failure pattern should not have changed. Modulators of this hypothesized mechanism include the velocity of the applied twist moment and the effects these have on the failure parameters and injury outcomes. The three physiologic loading rates investigated in this work were not shown to affect the ultimate axial twist rotational failure angle or moment in a neutral flexion/extension posture, but were shown to modify flexion-extension stiffness (Drake and Callaghan, 2008b– Chapter #5). All of the flexion-extension stiffness values post failure, from a one-time axial twist exposure, was less than those from a repetitive combined loading exposure that has been established to damage the intervertebral disc but not the facets. Therefore, it is likely that the facet joint provides the primary resistance to acute axial twist moments when the spine is in a neutral flexion posture, but there appears to be a redistribution of the applied load from the facets to the disc in repetitive exposures. The aforementioned studies determined there are changes in load distribution and load response caused by altered mechanics resulting from twist loading, but whether the exposures could possibly produce pain needed to be addressed. Previous research has determined that the disc has relatively low innervation in comparison to the richly innervated facet capsule and vertebra, with only the outer regions being innervated. Likewise, it is assumed that pain could be directly generated as the nucleus pulposus disrupted the innervated outer annular fibres in the process of herniation. Also, direct compression of the spinal cord or nerve roots has been shown to occur from the extruded nucleus and result in the generation of pain responses. Additionally, the nucleus pulposus has been shown to be a noxious stimulus that damages the function and structure of nerves on contact. The other source of nerve root compression commonly recognized is a decrease in intervertebral foramina space, which was previously believed to only be caused through losses in disc height. However, decreased intervertebral foramina space due to repetitive motions appears to be a viable pain generating pathway that may not directly correspond to simply a loss of specimen or disc height (Drake and Callaghan, 2008c– Chapter #6). This is new evidence for combined loading to generate pain through spinal deformation. The objective of many traditional treatments for nerve root compression focus on restoring lost disc height to remove the nerve root compression. Unfortunately, nerve root compression caused by repetitive loading may not be alleviated through this approach. This collection of studies was focused on determining whether altered load distribution in the spine, specifically between the intervertebral disc and facets, in response to applied axial twist loading (when added in combination with one and two axes of additional loading) was occurring, and examining how these modes of loading can contribute and/or alter the development of injury and pain. Therefore, findings generated from this thesis may have important implications for clinicians, researchers, and ergonomists