Application of Advanced Biomechanical Methods in Studying Low Back Pain – Recent Development in Estimation of Lower Back Loads and Large-Array Surface Electromyography and Findings

Low back pain (LBP) is a major public health problem and the leading disabling musculoskeletal disorder globally. A number of biomechanical methods using kinematic, kinetic and/or neuromuscular approaches have been used to study LBP. In this narrative review, we report recent developments in two biomechanical methods: estimation of lower back loads and large-array surface electromyography (LA-SEMG) and the findings associated with LBP. The ability to estimate lower back loads is very important for the prevention and the management of work-related low back injuries based on the mechanical loading model as one category of LBP classification. The methods used for estimation of lower back loads vary from simple rigid link-segment models to sophisticated, optimization-based finite element models. In general, reviewed reports of differences in mechanical loads experienced in lower back tissues between patients with LBP and asymptomatic individuals are not consistent. Such lack of consistency is primarily due to differences in activities under which lower back mechanical loads were investigated as well as heterogeneity of patient populations. The ability to examine trunk neuromuscular behavior is particularly relevant to the motor control model, another category of LBP classification. LA-SEMG not only is noninvasive but also provides spatial resolution within and across muscle groups. Studies using LA-SEMG showed that healthy individuals exhibit highly organized, symmetric back muscle activity patterns, suggesting an orderly recruitment of muscle fibers. In contrast, back muscle activity patterns in LBP patients are asymmetric or multifocal, suggesting lack of orderly muscle recruitment. LA-SEMG was also shown capable of capturing unique back muscle response to manual therapy. In conclusion, estimation of low back load and LA-SEMG techniques demonstrated promising potentials for understanding LBP and treatment effects. Future studies are warranted to fully establish clinical validity of these two biomechanical methods

Passive elastic contribution of hip extensors to joint moments during walking in people with low back pain

Background: It has been found that alterations in passive muscle properties may be associated with low back pain, and these may be responsible for the altered gait parameters often observed in subjects with back pain. The purpose of the present study was to assess total hip and passive hip extensor moments in people with or without low back pain during the hip flexion component of walking. Methods: 52 subjects volunteered for this study (low back pain group, n=25 (male n=13, female n=12), control group, n=27 (male n=15, female n=12)). Passive hip moments were calculated using an adapted force transducer during supine testing. A biomechanical model and predictive equation were used to calculate passive hip moments during walking. Total hip moments were calculated with the use of a 9 camera, 3-D motioncapture system.Findings: Independent samples t-tests demonstrated no significant differences between groups for gait parameters or hip or knee angles. Results of the ANOVAs demonstrated significant differences in passive hip flexor moments during the second half of hip flexion (P < 0.05).There were also significant differences in hip power and work done during peaks of power absorption and the second peak of power generation (P < 0.05). Interpretation: The present data demonstrates that subjects with low back pain have altered passive hip extensor and total power and work done during walking compared with healthy controls. Biomechanical models should include individual measurements of passive joint moments. © 2018, Elsevier. The attached document (embargoed until 14/10/2019) is an author produced version of a paper published in CLINICAL BIOMECHANICS uploaded in accordance with the publisher’s self- archiving policy. The final published version (version of record) is available online at the link below. Some minor differences between this version and the final published version may remain. We suggest you refer to the final published version should you wish to cite from it

A bovine nucleus pulposus explant culture model

Low back pain is a global health problem that is frequently caused by intervertebral disc degeneration (IVDD). Sulfated glycosaminoglycans (sGAGs) give the healthy nucleus pulposus (NP) a high fixed charge density (FCD), which creates an osmotic pressure that enables the disc to withstand high compressive forces. However, during IVDD sGAG reduction in the NP compromises biomechanical function. The aim of this study was to develop an ex vivo NP explant model with reduced sGAG content and subsequently investigate biomechanical restoration via injection of proteoglycan-containing notochordal cell-derived matrix (NCM). Bovine coccygeal NP explants were cultured in a bioreactor chamber and sGAG loss was induced by chondroitinase ABC (chABC) and cultured for up to 14 days. Afterwards, diurnal loading was studied, and explant restoration was investigated via injection of NCM. Explants were analyzed via histology, biochemistry, and biomechanical testing via stress relaxation tests and height measurements. ChABC injection induced dose-dependent sGAG reduction on Day 3, however, no dosing effects were detected after 7 and 14 days. Diurnal loading reduced sGAG loss after injection of chABC. NCM did not show an instant biomechanical (equilibrium pressure) or biochemical (FCD) restoration, as the injected fixed charges leached into the medium, however, NCM stimulated proliferation and increased Alcian blue staining intensity and matrix organization. NCM has biological repair potential and biomaterial/NCM combinations, which could better entrap NCM within the NP tissue, should be investigated in future studies. Concluding, chABC induced progressive, time-, dose- and loading-dependent sGAG reduction that led to a loss of biomechanical function. Keywords. biomechanics | intervertebral disc | matrix degradation | low back pain | proteoglycans.</p

Low back pain, the stiffness of the sacroiliac joint: A new method using ultrasound

Abnormal biomechanical properties of the sacroiliac joints are believed to be related to low back and pelvic pain. Presently, physiotherapists judge the condition of the sacroiliac joints by function and provocation tests, and palpation. No objective measuring device is available. Research is ongoing to identify the biomechanical properties of the sacroiliac joints from the dynamic behaviour of the pelvic bones. A new concept based on ultrasound (US) for the measurement of bone vibration is under investigation. The objective of this study was to validate this concept on a physical model and to assess the applicability in vivo. A model consisting of a piezo shaker covered by a layer of US transmission gel (representing bone and soft tissue) has been used. A packet of US detection signals is directed onto the shaker and correlation-based processing is used to estimate the difference in time-of-flight of their echoes. These variations of time are used to compute the displacement of the shaker at each pulse reflection. To assess the validity of our US technique, we compared the obtained measurements with the readings of the built-in strain gauge sensor. The experimental procedure has been tested on a volunteer where low-frequency excitation was provided through the ilium and vibration detected on the sacrum and ilia. The results demonstrated that the correlation-based approach is capable of reproducing the piezo shaker displacements with high accuracy (± 7%). Vibration amplitudes from 0.25 μm to 3 μm could be measured. The US technique was able to detect bone vibration in vivo. In conclusion, the principle based on US waves can be used to develop a new measurement tool, instrumental in studying the relation between the biomechanical properties of the sacroiliac joints and low back pain

Validation Testing of a Synthetic Spine and Upgraded Protocol for a Biomechanical Evaluation of a Lumbar Spinal Orthosis

Low back pain (LBP) is highly prevalent in all walks of life. Standard conservative treatment methods may work for some, but others go on to have spinal injections, opioids, or surgical procedures to alleviate pain. The Distractive and Mobility-Enabling Orthosis (DMO) was developed to meet the need for a conservative, drug-free treatment method. In this research, the low back support test protocol for evaluating DMO success was upgraded with a new synthetic lumbar spine model. The latest generation of the DMO project was then evaluated using the new system in a laboratory setting and on a pilot physical therapy patient.First, a biomechanical evaluation study of the new full-length synthetic lumbar spine model was performed to validate its use in the low back support test protocol. Markers placed at each vertebral body level enabled the local and global instantaneous axis of rotation of each spinal segment to be defined. Combined with moment data, the moment-rotational stiffness properties was compared to similar published data from other in vitro and in vivo studies of the lumbar spine. These comparisons provided validation and justification for using the synthetic model in the low back support test protocol. The design of the fourth generation (DMO4) is then detailed. DMO4 borrowed some characteristics from previous generations but was modified to lower the complexity of the parts and increase user comfort. DMO4 utilized hip and torso belts to secure itself to the patient. A distractive force applied via gas springs on the lateral sides of the belts separated the belts in order to offload the lumbar spine. DMO4 reduced the side profile, reduced the component count by half, and redesigned the torso belt to be more conforming to patient anatomy.DMO4 was then evaluated with the low back support test protocol that was set to match daily living activities (DLAs) and offload an average human torso weight. Placed under a 150N vertical load, DMO4 successfully offloaded the lumbar spine in upright stance through 25° of flexion and 10° of extension. DMO4 was also successful at providing unconstrained axial rotation beyond the range required for DLAs. Pilot data of a physical therapy patient with low back pain was ascertained. The patient wore the DMO during six physical therapy sessions over a four week period. At each session, the patient’s pain score significantly dropped to a pain rating score of one and the modified Oswestry Disability Index also saw a reduction

An Early Biopsychosocial Intervention Design for the Prevention of Low Back Pain Chronicity : A Multidisciplinary Empirical Approach

OBJECTIVE: Comprehensive intervention models for prevention of chronification of low back pain, in which the early identification of holistic risk factors is considered are needed. The aim of this study is to design a tailored biopsychosocial intervention for patients with low back pain to prevent pain chronicity. DESIGN: A multidisciplinary empirical approach. METHODS: A multidisciplinary team designed a biopsychosocial intervention following an application from the Medical Research Council's complex intervention framework. The methods used included problem identification, identification of the evidence, theory, and needs, examination of the current context and modelling of the theory. Biomechanical, psychological, social and environmental, and lifestyle and personal risk factors were taken into account. RESULTS: The intervention process was introduced in a logic model. The model presents all the required resources, their activities and outputs, as well as the outcomes and impacts of the intervention. The intervention was tailored according to the underlying risk factors for pain chronification in patients with low back pain. CONCLUSION: A comprehensive tailored intervention may decrease the risk of pain chronicity. Further studies are needed to obtain information on the feasibility, effectiveness and cost-effectiveness of such interventions.publishedVersionPeer reviewe

Low back biomechanics during manual materials handling of beer kegs

2017 Fall.Includes bibliographical references.Biomechanical risk factors such as heavy loads and awkward trunk postures have been associated with occupational low back pain. Those same risk factors are commonly experienced among workers handling beer kegs. The present study used a 3-dimensional motion capture system as a tool to investigate the low back biomechanics during keg handling at a working brewery. Specifically, five workers transferred spent kegs from a pallet to a conveyor to be cleaned and filled with beer in the present study. Data was collected during the portion of the shift workers handled kegs. Low back angular displacements were assessed during keg handling at two heights. Kegs originated from a high or low position and were defined as a high or low lift. Kinematic data from the study was used to estimate compressive and shear forces at the lumbosacral joint from a 2-dimensional static biomechanical model. Repeated measures analyses were performed with each low back angular displacement variable as a function of lift condition. Differences in low back biomechanics between high and low lifts were identified. During low lifts, torso flexion was significantly greater than high lifts. The magnitudes of flexion achieved during low lifts significantly exceeded those of high lifts. Differences between left axial rotation where significant with larger magnitudes of rotation occurring during high lifts. A broader range of angular displacements was observed in high lifts. In both lifting conditions, estimated kinetics exceeded recommended action limits, potentially putting workers at an increased risk for developing low back pain. Work design (lift condition) influenced low back motion during keg handling. Data collection during operational hours was feasible due to the portability and small design of inertial measurement units. Results from the study can help improve workplace design in a craft brewery, reduce risk, and create safer work

ISSLS PRIZE IN BIOENGINEERING SCIENCE 2019: biomechanical changes in dynamic sagittal balance and lower limb compensatory strategies following realignment surgery in adult spinal deformity patients.

Study designA longitudinal cohort study.ObjectiveTo define a set of objective biomechanical metrics that are representative of adult spinal deformity (ASD) post-surgical outcomes and that may forecast post-surgical mechanical complications. Current outcomes for ASD surgical planning and post-surgical assessment are limited to static radiographic alignment and patient-reported questionnaires. Little is known about the compensatory biomechanical strategies for stabilizing sagittal balance during functional movements in ASD patients.MethodsWe collected in-clinic motion data from 15 ASD patients and 10 controls during an unassisted sit-to-stand (STS) functional maneuver. Joint motions were measured using noninvasive 3D depth mapping sensor technology. Mathematical methods were used to attain high-fidelity joint-position tracking for biomechanical modeling. This approach provided reliable measurements for biomechanical behaviors at the spine, hip, and knee. These included peak sagittal vertical axis (SVA) over the course of the STS, as well as forces and muscular moments at various joints. We compared changes in dynamic sagittal balance (DSB) metrics between pre- and post-surgery and then separately compared pre- and post-surgical data to controls.ResultsStandard radiographic and patient-reported outcomes significantly improved following realignment surgery. From the DSB biomechanical metrics, peak SVA and biomechanical loads and muscular forces on the lower lumbar spine significantly reduced following surgery (- 19 to - 30%, all p &lt; 0.05). In addition, as SVA improved, hip moments decreased (- 28 to - 65%, all p &lt; 0.05) and knee moments increased (+ 7 to + 28%, p &lt; 0.05), indicating changes in lower limb compensatory strategies. After surgery, DSB data approached values from the controls, with some post-surgical metrics becoming statistically equivalent to controls.ConclusionsLongitudinal changes in DSB following successful multi-level spinal realignment indicate reduced forces on the lower lumbar spine along with altered lower limb dynamics matching that of controls. Inadequate improvement in DSB may indicate increased risk of post-surgical mechanical failure. These slides can be retrieved under Electronic Supplementary Material

Studies on Spinal Fusion from Computational Modelling to ‘Smart’ Implants

Low back pain, the worldwide leading cause of disability, is commonly treated with lumbar interbody fusion surgery to address degeneration, instability, deformity, and trauma of the spine. Following fusion surgery, nearly 20% experience complications requiring reoperation while 1 in 3 do not experience a meaningful improvement in pain. Implant subsidence and pseudarthrosis in particular present a multifaceted challenge in the management of a patient’s painful symptoms. Given the diversity of fusion approaches, materials, and instrumentation, further inputs are required across the treatment spectrum to prevent and manage complications. This thesis comprises biomechanical studies on lumbar spinal fusion that provide new insights into spinal fusion surgery from preoperative planning to postoperative monitoring. A computational model, using the finite element method, is developed to quantify the biomechanical impact of temporal ossification on the spine, examining how the fusion mass stiffness affects loads on the implant and subsequent subsidence risk, while bony growth into the endplates affects load-distribution among the surrounding spinal structures. The computational modelling approach is extended to provide biomechanical inputs to surgical decisions regarding posterior fixation. Where a patient is not clinically pre-disposed to subsidence or pseudarthrosis, the results suggest unilateral fixation is a more economical choice than bilateral fixation to stabilise the joint. While finite element modelling can inform pre-surgical planning, effective postoperative monitoring currently remains a clinical challenge. Periodic radiological follow-up to assess bony fusion is subjective and unreliable. This thesis describes the development of a ‘smart’ interbody cage capable of taking direct measurements from the implant for monitoring fusion progression and complication risk. Biomechanical testing of the ‘smart’ implant demonstrated its ability to distinguish between graft and endplate stiffness states. The device is prepared for wireless actualisation by investigating sensor optimisation and telemetry. The results show that near-field communication is a feasible approach for wireless power and data transfer in this setting, notwithstanding further architectural optimisation required, while a combination of strain and pressure sensors will be more mechanically and clinically informative. Further work in computational modelling of the spine and ‘smart’ implants will enable personalised healthcare for low back pain, and the results presented in this thesis are a step in this direction