Kinematic posture analysis of orthodontists in their daily working practice.

PURPOSE: The aim of this study is to conduct a kinematic analysis of occupational posture in orthodontists. METHODS: A representative sample of 21 (13 female/8 male) residents in orthodontics and orthodontists was studied. The CUELA system collects kinematic data of the occupational posture. Alongside the kinematic analysis, the tasks performed on-site were also subject to a detailed computerized analysis. Data analysis comprised the evaluation and comparison of joint angle distribution in accordance with ergonomic standards categorized as neutral, moderate or awkward posture. RESULTS: The most common activities were executed in a seated position. During "treatment" (28% of total time) participants most often worked with a straight back (84.7%), whereas a "bent or twisted" torso posture was observed 23.4% of the time. For head and cervical spine, the 75th and 95th percentiles presented worse (higher) values during treatment as compared to non-orthodontic activities. The seated position next to the patient during treatment showed a stronger inclination of the thoracic spine to the right and an inclination of the lumber spine to the left. CONCLUSIONS: Orthodontists do take characteristic postures during treatment activities with highest angle values. The postures differ in the area of head and cervical spine with regard to the various activities carried out in the 3 categories.

Motion analysis in the field of dentistry: a kinematic comparison of dentists and orthodontists.

OBJECTIVES: To conduct a kinematic comparison of occupational posture in orthodontists and dentists in their workplace. DESIGN: Observational study. SETTING: Dentist surgeries and departments of orthodontics at university medical centres in Germany. PARTICIPANTS: A representative sample of 21 (10 female, 11 male) dentists (group G1) and 21 (13 female, 8 male) orthodontists (G2) with one male dropout in G2. OUTCOME MEASURES: The CUELA (computer-assisted acquisition and long-term analysis of musculoskeletal loads) system was used to analyse occupational posture. Parallel to the recording through the CUELA system, a software-supported analysis of the activities performed (I: treatment; II: office; III: other activities) was carried out. In line with ergonomic standards the measured body angles are categorised into neutral, moderate and awkward postures. Activities between the aforementioned groups are compared using the stratified van Elteren U test and the Wilcoxon-Mann-Whitney U test. All p values are subject to the Bonferroni-Holm correction. The level of significance is set at 5%. RESULTS: The percentage of time spent on activities in categories I-II-III was as follows: dentists 41%-23%-36% and orthodontists 28%-37%-35%. The posture analysis of both groups showed, for all percentiles (P5-95), angle values primarily in the neutral or moderate range. However, depending on the activity performed, between 5% and 25% of working hours were spent in unfavourable postures, especially in the head-and-neck area. Orthodontists have a greater tendency than dentists to perform treatment activities with the head and torso in unfavourable positions. The statistically significant differences between the two groups with regard to the duration and the relevance of the activities performed confirm this assumption for all three categories (p<0.01, p<0.05). CONCLUSIONS: Generally, both groups perform treatment activities in postures that are in the neutral or medium range; however, dentists had slightly more unfavourable postures during treatment for a greater share of their work day.

Topographic deformation patterns of knee cartilage after exercises with high knee flexion: an in vivo 3D MRI study using voxel-based analysis at 3T.

OBJECTIVES: To implement a novel voxel-based technique to identify statistically significant local cartilage deformation and analyze in-vivo topographic knee cartilage deformation patterns using a voxel-based thickness map approach for high-flexion postures. METHODS: Sagittal 3T 3D-T1w-FLASH-WE-sequences of 10 healthy knees were acquired before and immediately after loading (kneeling/squatting/heel sitting/knee bends). After cartilage segmentation, 3D-reconstruction and 3D-registration, colour-coded deformation maps were generated by voxel-based subtraction of loaded from unloaded datasets to visualize cartilage thickness changes in all knee compartments. RESULTS: Compression areas were found bifocal at the peripheral medial/caudolateral patella, both posterior femoral condyles and both anterior/central tibiae. Local cartilage thickening were found adjacent to the compression areas. Significant local strain ranged from +13 to -15 %. Changes were most pronounced after squatting, least after knee bends. Shape and location of deformation areas varied slightly with the loading paradigm, but followed a similar pattern consistent between different individuals. CONCLUSIONS: Voxel-based deformation maps identify individual in-vivo load-specific and posture-associated strain distribution in the articular cartilage. The data facilitate understanding individual knee loading properties and contribute to improve biomechanical 3 models. They lay a base to investigate the relationship between cartilage degeneration patterns in common osteoarthritis and areas at risk of cartilage wear due to mechanical loading in work-related activities. KEY POINTS: • 3D MRI helps differentiate true knee-cartilage deformation from random measurement error • 3D MRI maps depict in vivo topographic distribution of cartilage deformation after loading • 3D MRI maps depict in vivo intensity of cartilage deformation after loading • Locating cartilage contact areas might aid differentiating common and work-related osteoarthritis.

Improving ergonomics in milking parlors: empirical findings for optimal working heights in five milking parlor types.

Milking postures have shifted from seated milking in tethered stalls to milking in a standing position in parlors. However, the musculoskeletal workload of dairy farmers remains high. Previous studies have shown that different working heights affect ergonomics, but they could not objectively evaluate and quantify the workload. The aim of the present study was to assess the effect of working height in different milking parlor types on the milker's workload during the task of attaching milking clusters. Computer-assisted recording and long-term analysis of movements were used to record positions of joints and body regions while performing certain tasks in terms of angular degrees of joints (ADJ) according to the neutral zero method. The 5th, 50th, and 95th percentiles described the distribution of angular degree values measured for each joint. The ADJ were evaluated according to international standards and other scientific literature on the issue to assess the muscular load. The workload was compared between 5 parlor types (auto tandem, herringbone 30°, herringbone 50°, parallel, and rotary) on 15 farms with 2 subjects per parlor and 1 milking period per subject. The working height was defined as a coefficient based on the milker's body height, the floor level, and the cow's udder height. The data recorded during the attachment task were analyzed using generalized linear mixed-effects models taking into account the hierarchical experimental design. The results indicated that the interaction of the cow's udder height, the milker's body height, and the parlor type had a larger effect on ergonomics than each parameter had independently. The interaction was significant in at least 1 of the 3 percentiles in 28 out of 31 ADJ. The postural differences between parlor types, however, were minor. A milking health formula was created to calculate the ideal depth of pit by considering the parlor type, the milker's height, and the mean herd udder height. This formula can be used to develop individual recommendations for future parlor construction.

A randomized intervention trial to reduce mechanical exposures in the Colombian flower industry.

BACKGROUND: Evidence on effectiveness of ergonomic interventions to reduce mechanical demands of the upper extremity is scarce in agriculture. OBJECTIVE: To conduct an ergonomic intervention to reduce mechanical exposures on workers during manual flower cutting, while emphasizing postural education and reduction of force requirements. PARTICIPANTS: Seventy seven workers (20 to 55 years old; 80% women) from six companies that cultivate roses participated in this study. METHODS: Participants from three companies were randomly assigned to control and intervention groups. A postural education program and a maintenance program was designed and implemented in the intervention group aiming to achieve more neutral postures of the wrist and forearm and to reduce force requirements during rose cutting. Changes in self-reported effort and upper extremity postures, kinematics and muscular activity between baseline and follow-up assessments were evaluated. RESULTS: Most of the observed changes in the evaluated mechanical exposures were moderate for both groups. The intervention group showed differential improvements compared to the control group for 95th percentile forearm pronation (intervention group went from 50.6 to 35.6°; control group went from 18.4 to 34.7°); and to some degree for the maximum wrist radial deviation (the intervention group went from 17° to 7.6°; control group went from 10.1° to 7.8°). Also, the mean elbow flexion for the control group was reduced from 62.3 to 48.4°, whereas it increased from 52.2 to 57.3° in the intervention group. No differential changes between the intervention and control groups were observed for the kinematic variables, except for an unexpected reduction in the 95th percentile velocity of wrist flexion-extension in the control group, which was not observed in the intervention group. Lastly, although observed changes in muscular activity were not statistically significant, improvements were observed for the intervention group for the flexor and extensor carpi radialis and the flexor carpi ulnaris; although the opposite was true for the extensor carpi ulnaris. CONCLUSIONS: Important although sometimes mixed results were achieved with this field intervention, focusing on postural and force requirement demands. The positive results are encouraging considering the presence of typical limitations observed in field intervention studies.

Physical workloads of the upper-extremity among workers of the Colombian flower industry.

BACKGROUND: We report the prevalence of symptoms of common upper-limb disorders and describe comprehensively mechanical workloads in a sample of workers of the Colombian flower industry. METHODS: One hundred fifty eight workers from eight flower manufacturers were assessed. Assessments included Borg self-reported exertion and working practices, medical examinations, video-based observations and kinematic and surface muscular activity assessments of upper-limb. RESULTS: Point prevalence of signs and symptoms of CTS, epicondylitis, and De Quervain's disease was 32.9%, 15.2%, and 13.3%, respectively. All tasks are executed on average in wrist extension, ulnar deviation, and high elbow flexion. Average median muscle activity across tasks ranged between 3.6% and 27.3%. Forearm muscles were mainly active. CONCLUSIONS: The occurrence of signs and symptoms of upper-extremity musculoskeletal disorders was high among the sample. The classification and cutting task showed the highest mechanical demands. Interventions in this working population are required and should be directed to allow for muscular rest on regular basis.

A randomized intervention trial to reduce mechanical exposures in the Colombian flower industry.

Evidence on the effectiveness of ergonomic interventions to reduce mechanical demands and upper-extremity MSDs is scarce in agriculture. We conducted an intervention to reduce mechanical exposures during manual flower cutting through job rotation, education and reduction of force requirements. One-hundred and twenty workers (20 to 60 years old; 89% women) from six companies that cultivate roses participated in this study. Three companies were randomly assigned to control and intervention groups. We studied changes between baseline and follow-up in self-reported effort and upper-extremity postures, kinematics and muscular activity. Most of the observed changes were moderate for both groups. The intervention group showed differential improvements compared to the control group for the maximum wrist radial deviation and forearm pronation, and acceleration of the forearm supination-pronation and elbow flexion-extension; and the muscular activity of the flexor and extensor carpi radialis and the flexor carpi ulnaris. However, we also observed that the maximum ulnar deviation, velocity of the wrist flexion-extension and muscular activity of the extensor carpi ulnaris improved more in the control group. These mixed results may be related to limited time for intervention adjustment, and uncontrolled task changes in the control group. Future research should address these issues and test other solutions.

[Locoregional deformation pattern of the patellar cartilage after different loading types - high-resolution 3D-MRI volumetry at 3 T in-vivo]. / Lokoregionäre Deformationsmuster im Patellarknorpel nach unterschiedlichen Belastungsparadigmen - hochauflösende 3-D-MR-Volumetrie bei 3 T in vivo.

PURPOSE: To analyze locoregional deformation patterns indicative of contact areas in patellar cartilage after different loading exercises. MATERIALS AND METHODS: 7 healthy patellae were examined in-vivo before and immediately after standardized loading (kneeling, squatting or knee bends) and after 90 minutes of rest using a sagittal 3D-T1-w FLASH WE sequence (22 msec/ 9.8 msec/ 15°/ 0.3 × 0.3 × 1.5 mm³) at 3 T. After cartilage segmentation and 3D reconstruction, voxel-based and global precision errors (PR) were calculated. The former were used to determine significant differences in local cartilage thickness. Voxel-based 2σ-thickness difference maps were calculated to visualize locoregional deformation patterns. Global changes in volume (Vol), mean thickness (mTh) and cartilage-bone-interface area (CBIA) were calculated. RESULTS: The voxel-based PR depended on cartilage thickness (D) ranging from 0.12 - 0.35 mm. For D ≥ 1 mm the RF was < 0.31 mm (< voxel size), and for D ≥ 2 mm, the RF was < 0.22 mm. The global PR was 83 mm³ (2.4 %) for Vol, 0.06 mm (2.0 %) for mTh and 16 mm² (1.4 %) for CBIA. The focal cartilage deformation equaled 14 % of the local thickness reduction. The deformation areas were oval and located in the peripheral medial (more vertically oriented, all exercises) and caudo-lateral (more horizontally oriented, kneeling and knee bends) aspects of the patella and were least pronounced in knee bends. Significant changes for Vol/mTh ranged from 2.1 to 3.7 %. CONCLUSION: This MRI-based study is the first to identify in-vivo voxel-based patellar cartilage deformation patterns indicating contact and loading zones after kneeling and squatting. These zones are anatomically and functionally plausible and may represent areas where stress induced degeneration and subsequent OA can originate. The data may facilitate understanding of individual knee loading properties and help to improve and validate biomechanical models for the knee.

[Radiological diagnosis of lumbar prolaps with quantitative and morphological criteria]. / Die radiologische Befundung des lumbalen Bandscheibenvorfalls nach quantitativen und morphologischen Kriterien.

PURPOSE: The present study examines the differences of radiological diagnosis of lumbar prolaps with quantitative and morphological criteria. Advantages and disadvantages of both methods were analysed. METHOD: Concerning the "Deutsche Wirbelsäulenstudie" (DWS) 286 male and 278 female patients between 25 and 70 years of age undergoing clinical or ambulant therapy for radicular symptoms and the diagnosis of a lumbar prolaps in CT and/or MRT were integrated into our study. Actual MRT and CT pictures of the patients' lumbar spine were analysed by an independent radiologist (primary radiologist). Radiological diagnosis was concerned with quantitative and morphological criteria. Radiological images of 100 selected patients were reexamined by another radiologist (secondary radiologist). On the basis of these results, the interobserver reliability (kappa) was calculated. RESULTS: In 95.2% of all segments a prolaps was seen with quantitative and morphological criteria, in 4.5% a prolaps was analysed with quantitative and in 0.3% a prolaps was seen with morphological criteria. The radiological diagnosis of prolaps by quantitative criteria was confirmed by the operative findings. Many prolapses with lateral localisation were seen in these cases. Therefore radiological diagnosis on the basis of morphological criteria could be difficult. For both radiological methods similar interobserver reliabilities were calculated. To sum up both radiological methods are even equivalent. It is also possible to graduate the diagnosis with quantitative criteria. Detrimental effects of quantitative criteria could be difficulties in measurement with non-digital images. CONCLUSION: Besides several recommendations in the international literature on the radiological analysis of prolaps with morphological criteria, diagnosis with quantitative criteria is also an effective method.

Load weight determination during dynamic working procedures using the pedar foot pressure distribution measuring system.

INTRODUCTION:: In 1994 a new BIA research project was launched, which deals with the development of a portable measuring system for recording of external stress parameters (e.g. body postures and handled load weights) at different places of employment. The investigations are carried out against the background of a newly recognized occupational disease (since 1993), which is that of damage of the spine following long-term repetitive lifting and carrying of heavy loads as well as working in an extreme trunk bending posture. As a part of the study it should be clarified if the worker's handled load weight can be determined by using a foot pressure distribution measuring system. METHODS:: In the case of a static working posture the handled load weight can simply be calculated by taking the difference of the measured weight and the known body rest weight of the worker. In dynamic situations the measured total foot reaction force consists of a static and a dynamic component, which is caused by the body movement and which is normally bigger than the load gravitational force. For load weight determination it is important to separate the dynamic forces from the measured total force to get an idea about its gravitational rest part. Therefore the body dynamics are measured synchronously to the foot pressure by using angle and angular velocity sensors. The herewith received data are used as input values for a developed biomechanical link segment model, with which it is possible to predict the foot reaction force. So even in dynamic situations an estimation of the handled load weight can be made by comparison of the predicted with the measured foot reaction force. RESULTS AND DISCUSSION:: In laboratory tests the load weight could be determinated reliably for different working processes over a total measuring time of 40 seconds. During the measurements the Pedar insoles were placed directly under the foot so that the accuracy of the static force measurement was reasonably high (with a maximal deviation of 5% to the real force). When the insoles were put in shoes, additional forces resulting from the bent shoe leather complicate the load weight determination. This effect still has to be analysed to compensate for it in future measurements. CONCLUSION:: The laboratory results encourage us for future measurements at places of employment. Currently our work focuses on an increase of the total measuring time and on a modification of the measuring system to a portable system without any connection to a computer. A field study is in preparation.