Are overground or treadmill runners more likely to sustain tibial stress fracture?
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BACKGROUND: Repetitive high bone strain and/or strain rates, such as those that occur during running, contribute to stress fractures as well as promoting maintenance of or increase in bone mass. Kinematic differences are known to exist between overground and treadmill running and these may be reflected in different bone strains and strain rates during the two running techniques. AIM: To measure in vivo strains and strain rates in human tibia during treadmill and overground running and determine if there are significant differences in strain and strain rate levels between the two running techniques. METHODS: A strain gauged bone staple was mounted percutaneously along the axial direction in the mid diaphysis of the medial tibia in three subjects, and in vivo tibial strains were measured during treadmill and overground running at 11 km/h. RESULTS: Axial compression strains (p<0.0001), tension strains (p<0.001), compression strain rates (p<0.0001), and tension strain rates (p<0.0001) were 48-285% higher during overground running than during treadmill running. CONCLUSIONS: On the basis of lower in vivo strains and strain rates, treadmill runners are at lower risk of developing tibial stress fractures, but less likely to achieve tibial bone strengthening, than overground runners. (+info)
Regional differences in cortical bone organization and microdamage prevalence in Rocky Mountain mule deer.
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The limb bones of cursorial mammals may exhibit regional structural/material variations for local mechanical requirements. For example, it has been hypothesized that mineral content (%ash) and secondary osteon population density (OPD) progressively change from proximal (e.g., humerus) to distal (e.g., phalanx), in accordance with corresponding progressive changes in stress and mechanical/metabolic cost of functional use (both greatest in the distal limb). We tested this hypothesis in wild-shot Rocky Mountain mule deer by examining transverse segments from mid-diaphyses of medial proximal phalanges, principal metacarpals, radii, and humeri, as well as the lateral aspects of sixth ribs from each of 11 mature males. Quantified structural parameters included the section modulus (Z), polar moment of inertia (J), cortical area/total area ratio (CA/TA), bone girth, and cortical thickness. In addition, %ash and the prevalence of in vivo microcracks were measured in each bone. Thin sections from seven animals were further examined for OPD and population densities of new remodeling events (NREs). Results showed a significant progressive decrease in %ash from the humerus (75.4% +/- 0.9%) to the phalanx (69.4% +/- 1.1%) (P < 0.0001), with general proximal-to-distal increases in OPD and general decreases in J and Z. Thirteen microcracks were identified in the rib sections, and only two were observed in the limb bones. Although the ribs had considerably greater NREs, no significant differences in NREs were found between the limb bones, indicating that they had similar remodeling rates. Equivalent microcrack prevalence, but nonequivalent structural/material organization, suggests that there are regional adaptations that minimize microcrack production in locations with differences in loading conditions. The progressive proximal-to-distal decrease in %ash (up to 6%); moderate-to-high correlations between OPD, %ash, J, and CA/TA; and additional moderate-to-high correlations of these parameters with each bone's radius of gyration support the possibility that these variations are adaptations for regional loading conditions. (+info)
Detecting microdamage in bone.
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Fatigue-induced microdamage in bone contributes to stress and fragility fractures and acts as a stimulus for bone remodelling. Detecting such microdamage is difficult as pre-existing microdamage sustained in vivo must be differentiated from artefactual damage incurred during specimen preparation. This was addressed by bulk staining specimens in alcohol-soluble basic fuchsin dye, but cutting and grinding them in an aqueous medium. Nonetheless, some artefactual cracks are partially stained and careful observation under transmitted light, or epifluorescence microscopy, is required. Fuchsin lodges in cracks, but is not site-specific. Cracks are discontinuities in the calcium-rich bone matrix and chelating agents, which bind calcium, can selectively label them. Oxytetracycline, alizarin complexone, calcein, calcein blue and xylenol orange all selectively bind microcracks and, as they fluoresce at different wavelengths and colours, can be used in sequence to label microcrack growth. New agents that only fluoresce when involved in a chelate are currently being developed--fluorescent photoinduced electron transfer (PET) sensors. Such agents enable microdamage to be quantified and crack growth to be measured and are useful histological tools in providing data for modelling the material behaviour of bone. However, a non-invasive method is needed to measure microdamage in patients. Micro-CT is being studied and initial work with iodine dyes linked to a chelating group has shown some promise. In the long term, it is hoped that repeated measurements can be made at critical sites and microdamage accumulation monitored. Quantification of microdamage, together with bone mass measurements, will help in predicting and preventing bone fracture failure in patients with osteoporosis. (+info)
Microdamage and mechanical behaviour: predicting failure and remodelling in compact bone.
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This paper reports on the development of a theoretical model to simulate the growth and repair of microdamage in bone. Unlike previous theories, which use simplified descriptions of damage, this approach models each individual microcrack explicitly, and also models the basic multicellular units (BMUs) that repair cracks. A computer simulation has been developed that is capable of making a variety of predictions. Firstly, we can predict the mechanical behaviour of dead bone in laboratory experiments, including estimates of the number of cycles to failure and the number and length of microcracks during fatigue tests. Secondly, we can predict the results of bone histomorphometry, including such parameters as BMU activation rates and the changing ratio of primary to secondary bone during ageing. Thirdly, we can predict the occurrence of stress fractures in living bone: these occur when the severity of loading is so great that cracks grow faster than they can be repaired. Finally, we can predict the phenomenon of adaptation, in which bone is deposited to increase cortical thickness and thus prevent stress fractures. In all cases results compare favourably with experimental and clinical data. (+info)
Common stress fractures.
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Lower extremity stress fractures are common injuries most often associated with participation in sports involving running, jumping, or repetitive stress. The initial diagnosis can be made by identifying localized bone pain that increases with weight bearing or repetitive use. Plain film radiographs are frequently unrevealing. Confirmation of a stress fracture is best made using triple phase nuclear medicine bone scan or magnetic resonance imaging. Prevention of stress fractures is most effectively accomplished by increasing the level of exercise slowly, adequately warming up and stretching before exercise, and using cushioned insoles and appropriate footwear. Treatment involves rest of the injured bone, followed by a gradual return to the sport once free of pain. Recent evidence supports the use of air splinting to reduce pain and decrease the time until return to full participation or intensity of exercise. (+info)
OBJECTIVE: To examine etiologic factors, clinical features, and outcome in a series of consecutive patients with fatigue fractures diagnosed at a rheumatology division for a defined population over a 14-month period. METHODS: A prospective study of the patients diagnosed with fatigue fracture at the rheumatology division of the Hospital Xeral-Calde (Lugo, Spain) between July 2000 and August 2001 was conducted. Hormonal status, body mass index, lifestyle, job, underlying diseases, and drug intake, which might be attributable risk factors for the stress fracture, were assessed. In all the patients a followup of at least 6 months was required. RESULTS: Six consecutive patients (4 women) fulfilled the inclusion criteria. All of them were younger than 65 years (median 45 years; range 36-64 years) and had a body mass index lower than 25. In this series no distinctive occupation was found. The delay to diagnosis since the onset of symptoms ranged from 0.5 to 6 months (median 1.5). All patients but 1 were sent to the rheumatology division because of a clinical diagnosis of monarthritis. Pain and swelling were the presenting symptoms. Conventional radiographs were normal and fine needle aspiration of the joints yielded negative results for microcrystals and organisms. Magnetic resonance imaging disclosed the presence and site of fracture in all the cases. Sequelae of mechanical pain and subsequent osteoarthritis were observed in the 3 cases with longer delay to diagnosis. CONCLUSION: Fatigue fractures are not exceptional in unselected adults. Rheumatologists should consider this diagnosis in patients presenting with monarthritis. Physician awareness is required to prevent the development of sequelae. (+info)
99mTc-MDP bone SPECT in evaluation of the knee in asymptomatic soccer players.
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OBJECTIVE: To evaluate stress fractures in leg (particularly around the knee, tibia, and femur) and knee pathology in active asymptomatic (no symptoms in the preceding month) soccer players. METHOD: The study included 42 asymptomatic soccer players (21 women, 21 men; age range 19-31 years). Players from seven teams in the major female professional and amateur male soccer leagues were examined by technetium-99m-methylene diphosphonate ((99m)Tc-MDP) bone scintigraphy during the soccer season. Four hours after intravenous injection of 20 mCi (99m)Tc-MDP, standard imaging included anterior planar spot images of the legs, lateral images of the knee, and single photon emission computed tomography (SPECT). RESULTS: Although the players were asymptomatic, increased tracer uptake, indicating stress fracture, was found in 28 (66%). Most of the stress fractures were in the tibia (62%) and femur (5%). In the 42 subjects (84 legs), 35 sites (42%) showed rupture of the posterior horn of the lateral meniscus and bone bruising of the tibial plateau, 16 sites (19%) showed rupture of the anterior horn of the medial meniscus, 11 sites (13%) showed bone bruising of the lateral femoral condyle, eight sites (10%) showed bone bruising of the medial femoral condyle, and there was avulsion injury to the infrapatellar tendon insertion in the anterior tibia in 34 sites (40%). There were 11 anterior cruciate ligament injuries. CONCLUSION: Bone SPECT is very accurate, easy to perform, cost effective, may give valuable information before magnetic resonance imaging studies in the detection of meniscal tears, and may be used successfully when magnetic resonance imaging is unavailable. (+info)
Fracture of the lateral process of the talus: computed tomographic scan diagnosis.
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Fracture of the lateral process of the talus is rare but can be mistaken for a simple ankle sprain. A case with normal conventional radiographs is presented to draw attention to this diagnosis in the resistant ankle sprain, and to highlight some of the problems that may be encountered with treatment. (+info)