Dynamically and statically determined low back moments during lifting

Assessment of the effects of lifting on the low back has most frequently been done with the aid of static models. Many lifting movements appear to have substantial inertial components. It was of interest, therefore, to determine the size of the difference between statically and dynamically calculated lumbar moments during a demanding but not unusual manual lift observed in a metal fabrication industry.

The results of several trials by four young men showed that the dynamic model resulted in peak L4 L5 moments 19% higher on average, with a maximum difference of 52%, than those determined from the static model. The technique adopted in the lift could minimize the difference. When the inertial forces of the load itself and the load weight were incorporated into an otherwise static model (quasi-dynamic) then the resulting L4/L5 moments exceeded those of the fully dynamic model by 25%.

In many industrial tasks static analyses may severely underestimate the demands of dynamic lifts. These results show that a reasonably inexpensive approach in lifting task analysis is to measure the dynamic forces of the load on the hands and to use these in an otherwise static model. This results in a conservative assessment of the injury risk of lifts at least of the type reported in this study.     

Manipulation in treatment of low back pain: a multicentre study.

In a multicentre trial 456 selected patients with low back pain were randomly allocated to one of four treatments-manipulation, definitive physiotherapy, corset, or analgesic tablets. Patients were reassessed clinically after three weeks'' treatment and again after a further three weeks. Questionnaires were used to find out the patients'' condition three months and one year after admission to the trial. There were never any important differences among the four groups of patients. A few patients responded well and quickly to manipulation, but there was no way of identifying such patients in advance. The response to a corset was slow, but the long-tern effects were at least as good as those of the other treatments. Patients treated only with analgesics fared marginally worse than those on the other three treatments. There is no strong reason, however, for recommending manipulation over physiotherapy or corset.     

Outcome of low back pain in general practice: a prospective study

Objectives: To investigate the claim that 90% of episodes of low back pain that present to general practice have resolved within one month. Design: Prospective study of all adults consulting in general practice because of low back pain over 12 months with follow up at 1 week, 3 months, and 12 months after consultation. Setting: Two general practices in south Manchester. Subjects: 490 subjects (203 men, 287 women) aged 18-75 years. Main outcome measures: Proportion of patients who have ceased to consult with low back pain after 3 months; proportion of patients who are free of pain and back related disability at 3 and 12 months. Results: Annual cumulative consultation rate among adults in the practices was 6.4%. Of the 463 patients who consulted with a new episode of low back pain, 275 (59%) had only a single consultation, and 150 (32%) had repeat consultations confined to the 3 months after initial consultation. However, of those interviewed at 3 and 12 months follow up, only 39/188 (21%) and 42/170 (25%) respectively had completely recovered in terms of pain and disability. Conclusions: The results are consistent with the interpretation that 90% of patients with low back pain in primary care will have stopped consulting with symptoms within three months. However most will still be experiencing low back pain and related disability one year after consultation.

Key messages

• It is widely believed that 90% of episodes of low back pain seen in general practice resolve within one month
• In a large population based study we examined the outcome of episodes of low back pain in general practice with respect to both consultation behaviour and self reported pain and disability
• While 90% of subjects consulting general practice with low back pain ceased to consult about the symptoms within three months, most still had substantial low back pain and related disability
• Only 25% of the patients who consulted about low back pain had fully recovered 12 months later
• Since most consulters continue to have long term low back pain and disability, effective early treatment could reduce the burden of these symptoms and their social, economic, and medical impact

     

Flow cytometry analysis of atherosclerotic plaque cells from human carotids: a validation study

BACKGROUND: Atherosclerotic plaques are heterogeneous vascular lesions. Changes in cell plaque composition are fundamental events inside the plaque microenvironment that are strictly related to the clinical outcome of these lesions (organ damage). The knowledge of these modifications may help to better understand the pathophysiological mechanisms of atherosclerosis. METHODS: We report on a flow cytometry method to characterize and quantify the cell subpopulations in human atherosclerotic plaques. Cells were obtained from endarterectomy specimens after collagenase digestion. Both surface and intracytoplasmic antigens were labeled. RESULTS: Our data demonstrated that the method we described allowed the characterization of cell populations that compose the atherosclerotic plaque, avoiding contamination by tunica media smooth muscle cells and the noise of cellular debris. Moreover this validation study showed that about 50% of cells in the atherosclerotic plaques are inflammatory mononuclear cells (T lymphocytes and monocytes/macrophages). CONCLUSIONS: Reproducible quantitative methods for cell population characterization may increase the understanding of pathophysiological mechanisms responsible for plaque progression. The methodology herein described gave us the possibility of quickly calculating the relative amount of each cell population and studying both surface and intracellular markers to analyze the functional stage of the cells. The clinical correlation was not assessed in the present study, because we used a small patient group to validate the method, but should be the subject of further analyses in a larger patient population.     

Heredity of low back pain in a young population: a classical twin study.

Important genetic influence on intervertebral disc degeneration has been shown previously. However, the role of the disc in pain production is not clear and the genetic influence on the development of the symptoms of low back pain is largely unknown. Therefore, data on lifetime prevalence of low back pain from the young cohort in The Danish Twin Registry (aged 12-41) were analyzed with respect to heredity. Casewise concordance rates, odds ratios, tetrachoric correlation coefficients and biometric liability models were estimated in relation to gender and age. Finally, age-adjusted heritability of liability estimates were obtained. Both concordance rates and odds ratios show significant genetic influence on the liability to develop low back pain. Also, tetrachoric correlation coefficients show genetic influence, but this is not statistically significant for all age groups. The biometric modeling demonstrates shared environment to be a strong component in the youngest age group (12-15), but not above age 15, and it also demonstrates some non-additive genetic effects in the older age groups. Age-adjusted heritability of liability is estimated to 44% (37-50) for males and 40% (34-46) for females aged 16 to 41. Thus, the various analyses all demonstrate significant genetic influence on the liability to low back pain. The shared environment is an important component until age 15. After age 15, this component is unimportant. As people grow older, the effect of the non-shared environment increases and non-additive genetic effects become more evident, indicating an increasing degree of genetic interaction as age increases.     

Thorough validation of protein normal mode analysis: a comparative study with essential dynamics

The deformation patterns of a large set of representative proteins determined by essential dynamics extracted from atomistic simulations and coarse-grained normal mode analysis are compared. Our analysis shows that the deformational space obtained with both approaches is quite similar when taking into account a representative number of modes. The results provide not only a comprehensive validation of the use of a low-frequency modal spectrum to describe protein flexibility, but also a complete picture of normal mode limitations.     

Estimation of low back loading on nurses during patient handling tasks: the importance of bedside reaction force measurement

By means of video recording, measurement of ground reaction forces, and biomechanical modeling of the lower part of the body, the low back loading of nurses during patient handling can be estimated. In this study the force exerted on the bedside by a nurse during different patient handling tasks was measured, and the contribution to the moment at the L4/L5 joint was investigated. It is shown that the bedside reaction moment contributes significantly to the total moment, and could lead to substantial over-estimation if not appropriately included in the calculations, when using an upward biomechanical model for estimating the spinal load of nurses during patient handling tasks.     

Exercise intervention for unilateral amputees with low back pain: study protocol for a randomised,controlled trial

Background

Atraumatic lower limb amputation is a life-changing event for approximately 185,000 persons in the United States each year. A unilateral amputation is associated with rapid changes to the musculoskeletal system including leg and back muscle atrophy, strength loss, gait asymmetries, differential mechanical joint loading and leg length discrepancies. Even with high-quality medical care and prostheses, amputees still develop secondary musculoskeletal conditions such as chronic low back pain (LBP). Resistance training interventions that focus on core stabilization, lumbar strength and dynamic stability during loading have strong potential to reduce LBP and address amputation-related changes to the musculoskeletal system. Home-based resistance exercise programs may be attractive to patients to minimize travel and financial burdens.

Methods/design

This study will be a single-assessor-blinded, pre-post-test randomised controlled trial involving 40 men and women aged 18–60 years with traumatic, unilateral transtibial amputation. Participants will be randomised to a home-based, resistance exercise group (HBRX) or a wait-list control group (CON). The HBRX will consist of 12 weeks of elastic resistance band and bodyweight training to improve core and lumbopelvic strength. Participants will be monitored via Skype or Facetime on a weekly basis. The primary outcome will be pain severity (11-point Numerical Pain Rating Scale; NRS_pain). Secondary outcomes will include pain impact on quality of life (Medical Outcomes Short Form 36, Oswestry Disability Index and Roland Morris Disability Questionnaire), kinematics and kinetics of walking gait on an instrumented treadmill, muscle morphology (muscle thickness of multifidus, transversus abdominis, internal oblique), maximal muscle strength of key lumbar and core muscles, and daily step count.

Discussion

The study findings will determine whether a HBRX program can decrease pain severity and positively impact several physiological and mechanical factors that contribute to back pain in unilateral transtibial amputees with chronic LBP. We will determine the relative contribution of the exercise-induced changes in these factors on pain responsiveness in this population.

Trial registration

ClinicalTrials.gov, ID: NCT03300375. Registered on 2 October 2017.

     

Effect of low pass filtering on joint moments from inverse dynamics: implications for injury prevention

Analyses of joint moments are important in the study of human motion, and are crucial for our understanding of e.g. how and why ACL injuries occur. Such analyses may be affected by artifacts due to inconsistencies in the equations of motion when force and movement data are filtered with different cut-off frequencies. The purpose of this study was to quantify the effect of these artifacts, and compare joint moments calculated with the same or different cut-off frequency for the filtering of force and movement data. 123 elite handball players performed sidestep cutting while the movement was recorded by eight 240 Hz cameras and the ground reaction forces were recorded by a 960 Hz force plate. Knee and hip joint moments were calculated through inverse dynamics, with four different combinations of cut-off frequencies for signal filtering: movement 10 Hz, force 10 Hz, (10-10); movement 15 Hz, force 15 Hz; movement 10 Hz, force 50 Hz (10-50); movement 15 Hz, force 50 Hz. The results revealed significant differences, especially between conditions with different filtering of force and movement. Mean (SD) peak knee abduction moment for the 10-10 and 10-50 condition were 1.27 (0.53) and 1.64 (0.68) Nm/kg, respectively. Ranking of players based on knee abduction moments were affected by filtering condition. Out of 20 players with peak knee abduction moment higher than mean+1S D with the 10-50 condition, only 11 were still above mean+1 SD when the 10-10 condition was applied. Hip moments were very sensitive to filtering cut-off. Mean (SD) peak hip flexion moment was 3.64 (0.75) and 5.92 (1.80) under the 10-10 and 10-50 conditions, respectively. Based on these findings, force and movement data should be processed with the same filter. Conclusions from previous inverse dynamics studies, where this was not the case, should be treated with caution.     

Assessment of low back muscle fatigue by surface EMG signal analysis: methodological aspects.

This paper focuses on methodological issues related to surface electromyographic (EMG) signal detection from the low back muscles. In particular, we analysed (1) the characteristics (in terms of propagating components) of the signals detected from these muscles; (2) the effect of electrode location on the variables extracted from surface EMG; (3) the effect of the inter-electrode distance (IED) on the same variables; (4) the possibility of assessing fatigue during high and very low force level contractions. To address these issues, we detected single differential surface EMG signals by arrays of eight electrodes from six locations on the two sides of the spine, at the levels of the first (L1), the second (L2), and the fifth (L5) lumbar vertebra. In total, 42 surface EMG channels were acquired at the same time during both high and low force, short and long duration contractions. The main results were: (1) signal quality is poor with predominance of non-travelling components; (2) as a consequence of point (1), in the majority of the cases it is not possible to reliably estimate muscle fiber conduction velocity; (3) despite the poor signal quality, it was possible to distinguish the fatigue properties of the investigated muscles and the fatigability at different contraction levels; (4) IED affects the sensitivity of surface EMG variables to electrode location and large IEDs are suggested when spectral and amplitude analysis is performed; (5) the sensitivity of surface EMG variables to changes in electrode location is on average larger than for other muscles with less complex architecture; (6) IED influences amplitude initial values and slopes, and spectral variable initial values; (7) normalized slopes for both amplitude and spectral variables are not affected by IED and, thus, are suggested for fatigue analysis at different postures or during movement, when IED may change in different conditions (in case of separated electrodes); (8) the surface EMG technique at the global level of amplitude and spectral analysis cannot be used to characterize fatigue properties of low back muscles during very low level, long duration contractions since in these cases the non-stable MU pool has a major influence on the EMG variables. These considerations clarify issues only partially investigated in past studies. The limitations indicated above are important and should be carefully discussed when presenting surface EMG results as a means for low back muscle assessment in clinical practice.     

A 1-year follow-up after a pilot study with Doloteffin for low back pain.

OBJECTIVE: To complete a year's follow-up on patients from a 6-week double-blind pilot comparison between 44 Doloteffin patients and 44 rofecoxib patients being treated for acute exacerbations of chronic low back pain. METHODS: 38 "ex-Doloteffin" (ex-D) and 35 "ex-rofecoxib" (ex-R) received Doloteffin containing 60 mg harpagoside per day for up to 54 weeks. Pain, additional analgesics, mobility, general health and adverse events were assessed from diary records and at 6-week visits. RESULTS: 53 patients remained in the follow-up at 24 weeks and 43 at 54 weeks. There was never any convincing difference between ex-D and ex-R patients in the number of patients remaining in follow-up, diary pain scores, additional analgesics, Arhus Index and health assessment questionnaire scores (HAQ). Individual fluctuations notwithstanding, the follow-up showed a slight overall improvement on the improvements in Arhus and HAQ scores achieved in the pilot study (MANOVA p = 0.016). Of the 21761 patient-days, the respective percentages with no, mild, moderate, severe and excruciating pain were 28%, 39%, 22%, 8.5% and 1.5%, respectively. Few patients requested additional treatments for their pain. Three patients suffered from minor adverse drug reactions. CONCLUSION: Long-term treatment with Doloteffin was well tolerated. Ex-R and ex-D patients behaved similarly during the follow-up.     

Tactile spatial resolution measured manually: a validation study

The purpose of this study was to investigate the validity of manual application of the grating orientation task (GOT), as currently used in fundamental and clinical research. Six examiners tested 12 subjects following recommendations of the literature. The results show that the normal force applied with the domes on the skin varied from one examiner to the next. Nevertheless, it did not affect the performance of the subjects, whose thresholds were consistent with those reported in the literature. This study highlights the inter-examiner reliability in the manual application of this test and validates this procedure.     

Predictors of occurrence and severity of first time low back pain episodes: findings from a military inception cohort

Primary prevention studies suggest that additional research on identifying risk factors predictive of low back pain (LBP) is necessary before additional interventions can be developed. In the current study we assembled a large military cohort that was initially free of LBP and followed over 2 years. The purposes of this study were to identify baseline variables from demographic, socioeconomic, general health, and psychological domains that were predictive of a) occurrence; b) time; and c) severity for first episode of self-reported LBP. Baseline and outcome measures were collected via web-based surveillance system or phone to capture monthly information over 2 years. The assembled cohort consisted of 1230 Soldiers who provided self-report data with 518 (42.1%) reporting at least one episode of LBP over 2 years. Multivariate logistic regression analysis indicated that gender, active duty status, mental and physical health scores were significant predictors of LBP. Cox regression revealed that the time to first episode of LBP was significantly shorter for Soldiers that were female, active duty, reported previous injury, and had increased BMI. Multivariate linear regression analysis investigated severity of the first episode by identifying baseline predictors of pain intensity, disability, and psychological distress. Education level and physical fitness were consistent predictors of pain intensity, while gender, smoking status, and previous injury status were predictors of disability. Gender, smoking status, physical health scores, and beliefs of back pain were consistent predictors of psychological distress. These results provide additional data to confirm the multi-factorial nature of LBP and suggest future preventative interventions focus on multi-modal approaches that target modifiable risk factors specific to the population of interest.