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PubMed1980

Studies of limb-dislodging forces acting on an ejection seat occupant.

A mathematical theory is being developed in order to calculate the aerodynamic loading to which a pilot is exposed during high-speed ejections. Neglecting the initial effects of flow separation, results thus far indicate that a pilot's musculoskeletal system is not likely to withstand the tendency for limb-flailing if he is ejecting at Mach numbers in excess of about 0.7. This tendency depends very strongly upon the angle at which the pilot's limbs intercept a high-speed flow; the forces that cause limb dislodgement increase dramatically with speed of ejection. Examining the time-course of limb-dislodging forces after the initial onset of windblast, the theory further predicts the generation of a double vortex street pattern on the downstream side of the limbs of an ejection seat occupant. This results in the corresponding appearance of oscillating forces tending to cause lateral motion (vibration) of the limbs. The amplitude and frequency of these oscillating forces are also very dependent on the Mach number of ejection and the angle at which the pilot's limbs intercept the flow. However, even at moderate Mach numbers, the frequency can be as high as 100 cycles per second, and the amplitude rapidly exceeds a pilot's musculo-skeletal resistive powers for Mach numbers above 0.7.

Aerospace Medicine↗
PubMed1996

Size and myosin heavy chain profiles of rat hindlimb extensor muscle fibers after 2 weeks at 2G.

METHOD: The effects of 14 d of continuous centrifugation at approximately 2G on the hindlimb extensor musculature of male rats were studied. RESULTS: The mean body mass of centrifuged rats was 17% smaller than age-matched controls. In centrifuged rats, the mean absolute masses of the soleus and medial gastrocnemius (MG) were similar to control, while the mean relative masses (expressed as milligram muscle mass/gram of body mass) were larger than control. Based on a battery of monoclonal antibodies for specific myosin heavy chains (MHC), the soleus of centrifuged rats had a lower percentage (68 vs. 74%) of fibers expressing type I MHC only and a higher percentage (15 vs. 10%) that co-expressed type I and IIa MHC's. The MHC composition of fibers from the deep portion of the MG was unaffected by centrifugation. The MHC compositions based on SDS-PAGE gel electrophoresis for each muscle were similar in the two groups. Mean fiber size of each fiber type in the soleus was unaffected by centrifugation. In the MG, the fibers, expressing only type IIb MHC were smaller in the centrifuge compared to control rats. CONCLUSION: Although 2 weeks of chronic centrifugation at 2G resulted in a cessation of body growth, there was essentially no effect on the muscle masses or fiber size in either a slow or fast extensor muscle. These data suggest that periods of centrifugation may be beneficial in maintaining extensor muscle mass in an animal that is not growing at a normal rate e.g., during chronic unloading.

Adaptation, Physiological↗
PubMed2004

[Joint hypermobility: prevalence and relationship with musculoskeletal pain].

OBJECTIVES: (1) To determine the prevalence of joint hypermobility in children aged 4-14 years old without organic disease of the locomotor system; (2) to compare the prevalence of hypermobility in children with and without arthralgia and (3) to analyze the influence of certain variables on the development of arthralgia. PATIENTS AND METHODS: We performed an observational study in a sample of children aged 4-14 years old living in Area 4 of the Community of Madrid (Spain). Joint hypermobility was evaluated using a goniometer. Hypermobility was defined using Beighton's criteria. RESULTS: A total of 222 subjects were analyzed: 176 in the primary care setting and 46 in the emergency department of a referral hospital. Of the 222 children, 43 reported arthralgia. The prevalence of hypermobility (> or = 4 criteria) was 55 % (123/222), reaching 71 % (49/69) in children aged less than 8 years. No significant differences were found in the prevalence of hypermobility in children with and without arthralgia (65 % and 53 % respectively). Of the variables analyzed (age, sex, country of origin, primary care/emergency department setting) only differences in the absolute number of Beighton criteria present in children with and without arthralgia (4.34 +/- 2.47 and 3.48 +/- 2.35, p = 0.03) were detected, which disappeared when at least four criteria (definition of hypermobility) were required. CONCLUSIONS: Fifty-five percent of the population studied and 71 % of those younger than 8 years old met the criteria for joint hypermobility. In the sample analyzed, the presence of joint hypermobility did not seem to favor the development of arthralgias.

Adolescent↗
PubMedDate not supplied

[The diabetic hand].

Diabetes mellitus is a chronic metabolic condition characterized by persistent hyperglycaemia with resultant morbidity and mortality related to its microvascular and macrovascular complications. In addition diabetes is also associated with several musculoskeletal disorders of the hand, that can be debilitating. There is increased incidence of these abnormalities in patients with type 1 and type 2 diabetes compared with the general population, related to disease duration but not to the age or sex. Typical diabetes associated hand condition include the palmar flexor tenosynovitis, Dupuytren's contracture, syndrome of limited joint mobility, carpal tunnel syndrome, Charcot arthropathy and reflex sympathetic dystrophy. Maintaining good glycaemic control by exercise, diet and drugs improves or prevents the development of these hand rheumatic condition. In this brief report we review the rational therapeutic approach to these disorders.

Arthropathy, Neurogenic↗
PubMed2005

Static compressive loading reduces the mRNA expression of type II and X collagen in rat growth-plate chondrocytes during postnatal growth.

The mechanisms by which chondrocytes modulate longitudinal bone growth are not well understood. This in vitro study investigated the effects of loading on the mRNA expression pattern of key molecular components of the growth-plate related to the extracellular matrix (type II and type X collagen) and the PTH-PTHrP feedback loop. Short-term static compressive loading was applied to rat proximal tibial growth-plate explants. Four age groups at specific developmental stages were investigated. The spatial variation in the mRNA expression was compared among loaded explants, their contralateral sham controls, and uncultured growth plates from normal animals. Basic cell metabolism (18S rRNA) was unaffected by load. Results indicated a narrower spatial distribution of mRNA expression of type II collagen throughout the growth plate; similarly, a narrowed distribution of expression of type X collagen was noted in the lower hypertrophic zone of the growth-plate. This suggests that mechanical compression influences chondrocytes of the hypertrophic zone to alter their expression of specific genes encoding proteins of the extracellular matrix, while PTH-PTHrP receptor mRNA, a regulatory protein, remained unaffected by loading. The effects of compression were similar at the different stages of growth, suggesting that additional factors may be involved in the clinical progression of skeletal deformities observed during growth spurts. Although this study was done in vitro and limited to static loading, it furthers our understanding of growth-plate mechanobiology as a first step toward providing a scientific rationale for treating progressive musculoskeletal deformities.

Animals↗
PubMed2006

Pathophysiology and therapeutic potential of purinergic signaling.

The concept of a purinergic signaling system, using purine nucleotides and nucleosides as extracellular messengers, was first proposed over 30 years ago. After a brief introduction and update of purinoceptor subtypes, this article focuses on the diverse pathophysiological roles of purines and pyrimidines as signaling molecules. These molecules mediate short-term (acute) signaling functions in neurotransmission, mechanosensory transduction, secretion and vasodilatation, and long-term (chronic) signaling functions in cell proliferation, differentiation, and death involved in development and regeneration. Plasticity of purinoceptor expression in pathological conditions is frequently observed, including an increase in the purinergic component of autonomic cotransmission. Recent advances in therapies using purinergic-related drugs in a wide range of pathological conditions will be addressed with speculation on future developments in the field.

Animals↗
PubMed2001

The physiological kinetics of nitrogen and the prevention of decompression sickness.

Decompression sickness (DCS) is a potentially crippling disease caused by intracorporeal bubble formation during or after decompression from a compressed gas underwater dive. Bubbles most commonly evolve from dissolved inert gas accumulated during the exposure to increased ambient pressure. Most diving is performed breathing air, and the inert gas of interest is nitrogen. Divers use algorithms based on nitrogen kinetic models to plan the duration and degree of exposure to increased ambient pressure and to control their ascent rate. However, even correct execution of dives planned using such algorithms often results in bubble formation and may result in DCS. This reflects the importance of idiosyncratic host factors that are difficult to model, and deficiencies in current nitrogen kinetic models. Models describing the exchange of nitrogen between tissues and blood may be based on distributed capillary units or lumped compartments, either of which may be perfusion- or diffusion-limited. However, such simplistic models are usually poor predictors of experimental nitrogen kinetics at the organ or tissue level, probably because they fail to account for factors such as heterogeneity in both tissue composition and blood perfusion and non-capillary exchange mechanisms. The modelling of safe decompression procedures is further complicated by incomplete understanding of the processes that determine bubble formation. Moreover, any formation of bubbles during decompression alters subsequent nitrogen kinetics. Although these factors mandate complex resolutions to account for the interaction between dissolved nitrogen kinetics and bubble formation and growth, most decompression schedules are based on relatively simple perfusion-limited lumped compartment models of blood: tissue nitrogen exchange. Not surprisingly, all models inevitably require empirical adjustment based on outcomes in the field. Improvements in the predictive power of decompression calculations are being achieved using probabilistic bubble models, but divers will always be subject to the possibility of developing DCS despite adherence to prescribed limits.

Algorithms↗
PubMed1981

Age-related reactions of rat bones to their unloading.

The effect was investigated of continued growth of animals on bone formation and resorption under conditions when their musculoskeletal systems were unloaded. Studied were rats aged 1, 2.5, and 6 months. To provide the unloading, the rats were suspended at an angle so that their hindlimbs did not touch the floor. After 22 days, the animals were sacrificed, and the length and width of the diaphysis of the femoral bone and its calcium content were measured. Bone reactions to the suspension were found to be age-dependent. The rats of 2.5 months showed the highest and the rats of 6 months the lowest increase in bone reabsorption at the side of the bone-marrow canal and in reduction of the cortical layer. With age, calcium decrease in the femur of suspended rats became less pronounced compared to controls. The age-related bone reactions to the musculoskeletal unloading must be taken into consideration when planning and conducting rat studies.

Aging↗
PubMed2006

Advances in musculoskeletal radiology: multidetector computed tomography.

The clinical potential of multidetector CT is significantly increased because of the possibility of almost instantaneous isotropic reformations in all planes, increased speed and coverage, and easy interpretation. Multidetector CT has a significant role in the correct and quick diagnosis and treatment of emergency department patients. In complex anatomic regions, it is an important diagnostic aid, and it allows exact classification of the bony lesion, which is important for diagnosis, treatment, and prognosis. Multidetector CT visualizes congenital deformities and is useful in oncology. Ongoing developments comprise diagnosis and treatment, preoperative and postoperative planning, and hard-ware imaging. Relatively new but well-known applications of multidetector CT include intraoperative navigation, implant and prosthesis planning and surgery simulation, vertebroplasty, and pedicle screw installations.

Arthroplasty, Replacement, Hip↗
PubMed1996

The clinical course of musculoskeletal pain in empirically derived groupings of injured workers.

The purpose of this paper is to examine the clinical course of musculoskeletal, soft tissue, work-related injury. An analysis of empirically derived sub-groupings of workers based on prognostically important pain and disability variables assessed on enrollment into the study is described. Multidimensional time-dependent profiles are used to characterize stages in the development of pain, impairment, disability and handicap. The clinical course over the 18 months of study of the three subgroups is examined. The conceptual model, used to examine the workers' changing responses over time, is based on the World Health Organization Classification of Impairments, Disabilities and Handicaps (1980). Methodologically, the study employed a prospective longitudinal design. A randomly selected cohort of workers who had not returned to work by 3 months post-injury were identified from the files of the Workers' Compensation Board of Ontario. The workers were interviewed and examined on enrollment into the study at 3 months and subsequently at 9 months, 15 months and 21 months after injury. The outcomes were return to work or continued work disability. The results are based on those 104 workers who attended all four assessment periods. K means clustering was used to identify homogenous subgroups of workers. Repeated measures ANOVAs were used to characterize the stages of development of pain, impairment, disability and handicap. Duncan's multiple range test was used to compare pairs of means at each assessment period. Cluster groupings, based on three prognostically important clinical variables, number of pain sites, pain behavior and functional disability, obtained at the initial assessment were valid predictors of the number of days to return to work and total number of days on work disability. Prognostic stratification can enhance confidence in predictive decisions of clinical practice and improve clinical trials of therapy.

Adult↗
PubMed1989

Effect of infection with the ts22 mutant of Semliki Forest virus on development of the central nervous system in the fetal mouse.

The A7 strain of Semliki Forest virus induces rapid fetal death in pregnant mice, whereas the ts22 mutant derived from it is teratogenic for a proportion of fetuses. Both A7 and ts22 induce viremia and infect the central nervous systems and fetuses of pregnant mice. Using immunogold-silver staining, a cDNA probe for a Semliki Forest virus nonstructural sequence, and a riboprobe derived from the same sequence, we showed that the skin and musculoskeletal systems of fetuses from mothers infected with ts22 were often heavily infected but the central nervous systems were not labeled before day 17 of pregnancy. Damage to the neural tube, including open-neural-tube defects, was detected in fetuses following infection of the mother at days 8 and 10 of pregnancy with both A7 and ts22. For ts22, neural tube damage induced by fetal infection before day 17 of pregnancy appeared to be indirect and caused by virus infection of mesenchymal cells surrounding the developing neural tube.

Animals↗
PubMed1999

Synovial sarcoma: identification of low and high risk groups.

BACKGROUND: Synovial sarcoma, one of the most common soft tissue sarcomas that occur in adolescents and young adults, is generally viewed and treated as a high grade sarcoma. However, the authors' own experience and some previous studies have indicated that it has a wide spectrum of biologic behavior and that low and high risk subgroups of patients with synovial sarcoma can be identified. METHODS: A total of 121 consecutive patients with synovial sarcoma (including 66 males and 55 females ages 9-74 years), treated primarily or secondarily at 2 large referral centers for musculoskeletal tumors, were included in a statistical analysis conducted to identify independent prognostic factors. RESULTS: There were local recurrences in 38 patients (31%), usually after inadequate primary surgery outside the referral centers; 64 patients (54%) developed metastasis, primarily to the lungs. The estimated 5-, 10-, and 15-year survival rates were 60%, 50%, and 45%, respectively (the mean follow-up for surviving patients was 9.8 years, with a range of 1-30 years). In multivariate analysis, independent risk factors for local recurrence included larger tumor size and primary surgical resection outside the referral center. Independent risk factors for metastasis were older patient age, tumor with poor histologic differentiation, and tumor necrosis. For tumor-related death, the independent risk factors were older patient age, tumor with poor histologic differentiation, and larger tumor size. Local recurrence was associated with a 3.66-fold increased risk of tumor-related death. A low risk group (patient age <25 years, tumor size <5 cm, and no histologic evidence of poorly differentiated tumor) with 88% overall disease free survival was identified, as was a high risk group (patient age > or = 25 years, tumor size > or = 5 cm, and poorly differentiated tumor) with 18% overall disease free survival (P < 0.001). CONCLUSIONS: The identification of low and high risk synovial sarcoma patients indicates that synovial sarcomas are not uniformly high grade tumors. It also indicates that treatment strategies should be modified for these risk groups. Adequate primary surgery is essential to both local control and outcome for synovial sarcoma patients.

Adolescent↗
PubMed1998

Motivating factors for return to work.

BACKGROUND AND PURPOSE: A new concept to increase return to work for patients listed as sick with chronic musculoskeletal pain has been used at a rehabilitation centre in Luleå, Sweden. The programme includes work for three days a week and intensive rehabilitation for two days a week, for 12 weeks, as a combination of 'on the job' training and rehabilitation after a period off work sick. The rehabilitation programme focused on pain reduction, identifying and finding solutions to pain problems in actual work and life situations and training of the functional capacities needed in the work and life situation. The aim of the study was to describe patients' perceptions of motivating factors for return to work. METHODS: A phenomenological method was used. A naïve reading of interview notes was followed by structural analyses and reflections on the interpreted whole. Inclusion criteria for the study were musculoskeletal pain for at least one year and a period of at least four weeks' sick leave during that time. Ten patients, aged 30-54 years, participated in the study. An initial conceptual framework was developed to inform the scope of the study and to guide data collection and analysis. RESULTS: Different factors in the study framework influenced motivation to return to work. Among structural factors the division of labour at work was the most important motivator, particularly the ability to do as much as work colleagues, quantitatively and qualitatively. All the patients had jobs in the healthcare or service sectors, jobs with many social contacts. They perceived their work task content as being of minor importance compared to whether the tasks were perceived as meaningful or highly needed by others. All wanted a meaningful job content and a job which they could do in a satisfactory way according to their own norms and compared to colleagues. This highly increased motivation for return to work. Relationships (in terms of co-operation with colleagues and service to patients or clients) were important motivating factors for return to work. Self-confidence was a new factor of importance for return to work; work tasks had to be meaningful and needed by others, work must be done in a way satisfactory for the individual and in a way that was acceptable to others in the group. Everyday responsibility, feedback and support in daily work tasks were important. These aspects increased self-confidence. The results supported the development of a new conceptual framework for possible motivating factors for return to work. CONCLUSIONS: Structure, content, relationships, health and self-confidence were all important motivating factors for return to work.

Adult↗
PubMed1999

Management of Lyme arthritis.

Musculoskeletal complaints and findings can be features of Lyme disease and can occur following treatment. Only with a good understanding of the pathogenesis of these problems can further evaluation and a proper therapeutic scheme be developed.

Anti-Bacterial Agents↗
PubMed2006

[Computer assisted radiological diagnostics of arthritic joint alterations].

Computer assisted diagnosis (CAD) schemes are currently used in the field of musculoskeletal diseases to quantitatively assess vertebral fractures, joint space narrowing, andr erosion. Most systems work semi-automatically, i.e. they are operator dependent in the selection of anatomical landmarks. Fully automatic programs are currently under development. Some CAD products have already been successfully used in clinical trials.

Absorptiometry, Photon↗
PubMed2001

Innovative therapies in osteoarthritis.

Until recently, osteoarthritis (OA) was classified as a mechanical wear-and-tear disorder of articular cartilage, for which only pain-modifying therapies such as nonaddictive analgesics were prescribed. Little scientific attention had been focused on the patient with OA, who typically was seen as a frail elderly person hobbling down the street with a cane. With the demographic change that is facing medical policy makers, musculoskeletal disability will decrease the quality of life of the elderly population. By way of analogy, the medical establishment viewed osteoporosis as a similar disease paradigm. However, because of huge commitments of funding and drug development effort, new drugs that reduce the frequency of fractures in postmenopausal women are available. OA and the area of cartilage biology will undoubtedly follow a similar course. Recently, new research identified interleukin 1-beta, collagenase and other matrix metalloproteinases, and signal transduction pathways as important pathobiologic targets in OA. Cartilage agonists such as recombinant human growth factors and gene therapy constructs that stimulate the chondrocyte are being studied in animal models and in humans. Orthopedic approaches, including cartilage regeneration and joint resurfacing techniques with or without biomaterials, are being developed. During the next decade, new efforts will modify the structure and function of the joint, which will be layered onto the drugs, devices, and strategies in use that reduce the pain and suffering in patients with this disease.

Acupuncture↗
PubMed1996

A model for solving work related musculoskeletal problems in a profitable way.

Interventions against occupational musculoskeletal disorders are usually performed by ergonomists. An overview of the literature shows that ergonomists often are unsuccessful; musculoskeletal disorders may be prevalent at workplaces where large ergonomic resources have been put in, thus illustrating the significance of other factors in addition to those against which the intervention is applied. It is claimed that some modern rationalization strategies may offer a potential for 'good' ergonomics. Thus, prevailing management approaches often now focus on team building, flat organizations, training of multiple skills and so on. The main scope of the present issue of Applied Ergonomics is to throw light on this possibility of 'achieving ergonomics impact through management intervention'. This present paper presents a historical overview of occupational physical work load as a function of ergonomics, as well as rationalizations and concludes with a more elaborate discussion of the present intervention concept for solving work related musculoskeletal problems in a profitable way. Rationalization and guidelines for physical work load are the basic parameters in the present intervention concept. Due to this the present special issue also presents historical overviews of the development of these parameters (Westgaard and Winkel; Bjorkman). 'Achieving ergonomics impact through management intervention' is illustrated through two case studies (Kadefors et al and Bao et al). They demonstrate an obvious ergonomic potential offered by the presented intervention concept. However, the two case studies also describe several practical obstacles which need to be further investigated in future intervention research.

Editorial↗
PubMed2006

Nonlinear finite element analysis for musculoskeletal biomechanics of medial and lateral plantar longitudinal arch of Virtual Chinese Human after plantar ligamentous structure failures.

BACKGROUND: Musculoskeletal diseases of the foot such as stress fractures, tendonitis and subsequent pain are commonly associated with elevated stresses/strains of abnormal plantar arch after plantar ligamentous structure failures. The goal of this study was to develop anatomically detailed, finite element models of the medial and lateral plantar longitudinal arch, and to investigate bone and muscle stresses resulting from plantar fasciotomy and major plantar ligament injuries. METHODS: Nonlinear finite element models of the second ray and the fifth ray of plantar longitudinal arches were constructed on the basis of CT and MR images of Virtual Chinese Human "female No. 1". The models assumed a balanced standing load configuration. Three different degrees of passive intrinsic muscle tensions (weak, moderate, or severe) were used in conjunction with simulations of plantar fasciotomy and major plantar ligament injury. FINDINGS: Plantar fasciotomy caused von Mises stress increases in the bones and plantar ligaments while major plantar ligament injuries caused stress increases in the bones, flexor tendons, and plantar fascia. Increasing intrinsic muscle passive tensions decreased stress/strain levels in the medial and lateral arch, and adjusted abnormal tension/compression stress flows of both arches to close to the normal biomechanical states. INTERPRETATION: This study shows that plantar longitudinal arches are concordant combination of bony structures, intrinsic muscles, plantar fascia and ligaments. After plantar ligamentous structure failures, intrinsic muscles have to contribute to stabilize the plantar arches. This mechanism may reduce the risk of developing stress fractures, tendonitis and pain syndrome.

Biomechanical Phenomena↗