Influence of creep deformation on sub-regional lumbar spine motion during manual lifting

Cumulative creep response of viscoelastic lumbar tissue as a function of work-rest schedule

We explore the effect of stress-recovery schedule on the cumulative creep response of lumbar tissues. Twelve participants performed a 48-minute protocol that consisted of 12 min of full trunk flexion and 36 min of upright standing. Two stress-recovery (work-rest) schedules were considered: a) three minutes of full trunk flexion followed by twelve minutes of upright standing (3:12), and b) one minute of full trunk flexion followed by four minutes of upright standing (1:4). Lumbar kinematics and EMG activity of erector spinae muscles were collected. Cumulative creep deformation was explored by considering the changes in peak lumbar flexion angles during full flexion and changes in the angles of flexion-relaxation (EMG-off) of the lumbar extensor musculature after the 48-minute protocol. The results of time-dependent lumbar flexion angle during full flexion revealed a noticeable creep response in both work-rest schedules, but the cumulative creep response was significantly greater in the 3:12 schedule (Δ3.5°) than in the 1:4 schedule (Δ1.6°). Similarly, the change in the EMG-off lumbar flexion angle in the 3:12 schedule was significantly greater than in the 1:4 schedule (Δ2.5° vs -Δ0.2°, respectively). These results indicate that the passive lumbar tissues recover their force producing capability more rapidly with shorter cycle times.

Physical Ergonomic Assessment in Cleaning Hospital Operating Rooms Based on Inertial Measurement Units

Workers involved in hospital operating room cleaning face numerous constraints that may lead to musculoskeletal disorders. This study aimed to perform physical ergonomic assessments on hospital staff by combining a continuous assessment (RULA) based on inertial measurement units with video coding. Eight participants performed cleaning tasks while wearing IMUs and being video recorded. A subjective evaluation was performed through the Nordic questionnaire. Global RULA scores equaled 4.21 ± 1.15 and 4.19 ± 1.20 for the right and left sides, respectively, spending most of the time in the RULA range of 3-4 (right: 63.54 ± 31.59%; left: 64.33 ± 32.33%). Elbows and lower arms were the most exposed upper body areas with the highest percentages of time spent over a risky threshold (right: 86.69 ± 27.27%; left: 91.70 ± 29.07%). The subtask analysis identified 'operating table moving', 'stretcher moving', and 'trolley moving' as the riskiest subtasks. Thus, this method allowed an extensive ergonomic analysis, highlighting both risky anatomical areas and subtasks that need to be reconsidered.

Creep deformation of viscoelastic lumbar tissue during sustained submaximal trunk flexion postures

Most in-vivo human experiments exploring creep deformation of viscoelastic lumbar tissue have used a maximum trunk flexion posture to engage the lumbar passive tissues. Recent evidence suggests that static trunk flexion tasks requiring submaximal trunk flexion can lead to gradual changes in the lumbar lordosis and this leads to our hypothesis that maintaining submaximal trunk flexion postures may lead to significant creep deformation of the viscoelastic lumbar tissues. Sixteen participants maintained a trunk flexion posture that was ten degrees less than the trunk flexion posture eliciting flexion-relaxation phenomenon for 12 min with breaks for a maximal trunk flexion protocol every three minutes. Trunk kinematic and extensor EMG measures were captured during the static, submaximal trunk flexion protocol as well as during the maximal trunk flexion protocol to provide evidence of creep development in the lumbar passive tissues. Results revealed that 12-minutes of submaximal trunk flexion led to significant increases in peak lumbar flexion angle (1.3°) and EMG-off lumbar flexion angle for L3/L4 paraspinals (2.9°). During the submaximal trunk flexion protocol, the changes in the lumbar flexion angle at 3-6 min and 6-9 min (average Δ5.4°) were significantly greater than at 0-3 min (Δ2.0°). The contribution of this study is the demonstration that sustained submaximal trunk flexion posture (i.e., constant global system) can lead to creep deformation of the viscoelastic lumbar tissue due to the increased lumbar flexion (i.e., altered local system) and may be attributed to a reduction in lumbar lordosis as the extensor muscles fatigue.

The effect of walking and stationary work on the acute back pain, muscle activation, posture and postural control of older women

Back pain is associated with activity such as walking or assembly line work that involves upper-body movement. However, no single study has explored the effect of these tasks on back pain, spinal angles and balance in an older adult female population. This study investigated changes in back pain, postural sway, upper-, lower- and full-spine angle and EMG activation of trunk muscles following 30 minutes of walking and a modified quiet standing task. Fourteen older adult females (62 ± 11yrs) with low to moderate chronic back pain were recruited as participants. Findings demonstrated that following these activities, increased acute back pain and upper-spine flexion occur although acute back pain was not clinically significant; postural control and muscle activation remained unchanged. This suggests that walking and modified quiet standing can lead to subtle acute back pain in older females that could be due to an increased upper spinal flexion rather than muscle fatigue. Practitioner summary: Back pain and postural problems are common in older adults. Older adult female participants experienced increased back pain and greater upper-spine flexion following 30-minute walking and standing with trunk rotation, but the practical importance was less clear. However, balance was unaffected, suggesting no increase in fall risk. Abbreviations: CBP: chronic back pain; MQS: modified quiet standing; QS: quiet standing; RPE: rating of perceived exertion; TD: trapezius descendens; TT: trapezius transversalis; TA: trapezius ascendens; ESL: erector spinae longissimus; C7: seventh cervical vertebrae; T7: seventh thoracic vertebrae; T10: tenth thoracic vertebrae; T12: twelfth thoracic vertebrae; L2: second lumbar vertebrae; S2: second sacral vertebrae; AP: anterior-posterior; ML: medial-lateral; SWAYtot: total postural sway; M: mean.

A method of 3D-3D multi-stage non-rigid registration of the spine based on binocular structured light

BACKGROUND

Intraoperative deformation and radiation are common problems in spinal surgery. A three-dimensional multi-stage dynamic iterative non-rigid registration method of the spine based on binocular structured light is proposed in this paper to overcome these problems.

METHOD

The problem of intraoperative radiation in traditional X-ray and CT is overcome by using binocular structured light. A three-dimensional spinal mask based on binary code is designed to reduce the influence of non-interested regions on the operation. Principal component analysis (PCA) algorithm is used to complete the rough registration between the preoperative CT model of the spine and the reconstructed surface of the intraoperative structured light. A new framework of multi-stage dynamic iterative non-rigid registration of the spine is proposed. The Iterative Closest Point (ICP) algorithm based on bidirectional selection is proposed to complete the single-stage registration of the spine. Then the multi-stage dynamic iterative registration of the spine is completed to solve the problem of large registration error caused by the deformation of the spine.

RESULTS

The method proposed in this paper is compared with traditional registration methods, and its application is verified experimentally. The results show that the registration accuracy and time of the proposed method are 0 . 51 ± 0 . 31  mm and 5 . 21 ± 0 . 23  s, respectively. The accuracy of the method is 81.5% and 78.2% higher than that of the contour method and the method of marker points, respectively.

CONCLUSIONS

The method can effectively avoid intraoperative radiation, reduce the registration error caused by the deformation of the spine, and has a high practicability.