A quantitative study of humeral cartilage in individuals with spinal cord injury.

STUDY DESIGN: Cross-sectional design. OBJECTIVES: In this in vivo study, we investigated the influence of different load situations on humeral cartilage thickness in individuals with paraplegia and quadriplegia. SETTING: ETH Zurich and Swiss Paraplegic Centre Nottwil, Switzerland. METHODS: A previously validated three-dimensional (3D) gradient echo MRI-sequence with selective water excitation was used. Three groups were compared: individuals with paraplegia with high shoulder demand (n=11), individuals with quadriplegia with reduced load on the shoulder joint (n=8) and a control group (n=9). After 3D reconstruction, the mean cartilage thickness, local thicknesses (superior, medial, inferior) and the minimum joint space were calculated. RESULTS: The mean humeral cartilage thickness (1.40+/-0.14 mm) as well as the minimum joint space (2.57+/-0.50 mm) did not differ between groups. In individuals with paraplegia, the superior cartilage thickness was significantly greater than in individuals with quadriplegia (1.47 mm compared to 1.28 mm, P<0.05). In the control group, there was a significant negative correlation between mean cartilage thickness and age (r=-0.81). CONCLUSION: Neither higher shoulder demand nor reduced shoulder loading leads to thinning of humeral cartilage. It is hypothesized that higher local stresses prevent local cartilage degeneration, as in normal load situations humeral cartilage thinning is occurring with age. Furthermore, joint space narrowing was only associated with inferior cartilage thickness and cartilage thickness is not related to shoulder pain.

Dynamic behaviour of half-sarcomeres during and after stretch in activated rabbit psoas myofibrils: sarcomere asymmetry but no 'sarcomere popping'.

We examined length changes of individual half-sarcomeres during and after stretch in actively contracting, single rabbit psoas myofibrils containing 10-30 sarcomeres. The myofibrils were fluorescently immunostained so that both Z-lines and M-bands of sarcomeres could be monitored by video microscopy simultaneously with the force measurement. Half-sarcomere lengths were determined by processing of video images and tracking the fluorescent Z-line and M-band signals. Upon Ca2+ activation, during the rise in force, active half-sarcomeres predominantly shorten but to different extents so that an active myofibril consists of half-sarcomeres of different lengths and thus asymmetric sarcomeres, i.e. shifted A-bands, indicating different amounts of filament overlap in the two halves. When force reached a plateau, the myofibril was stretched by 15-20% resting length (L0) at a velocity of approximately 0.2 L0 s(-1). The myofibril force response to a ramp stretch is similar to that reported from muscle fibres. Despite the approximately 2.5-fold increase in force due to the stretch, the variability in half-sarcomere length remained almost constant during the stretch and A-band shifts did not progress further, independent of whether half-sarcomeres shortened or lengthened during the initial Ca2+ activation. Moreover, albeit half-sarcomeres lengthened to different extents during a stretch, rapid elongation of individual sarcomeres beyond filament overlap ('popping') was not observed. Thus, in contrast to predictions of the 'popping sarcomere' hypothesis, a stretch rather stabilizes the uniformity of half-sarcomere lengths and sarcomere symmetry. In general, the half-sarcomere length changes (dynamics) before and after stretch were slow and the dynamics after stretch were not readily predictable on the basis of the steady-state force-sarcomere length relation.

Long-term changes in the tibia and radius bone mineral density following spinal cord injury.

DESIGN: A prospective inception cohort study with an observational analytic design in a spinal cord injury (SCI) centre hospital. OBJECTIVE: To assess changes in trabecular and compact bone of the tibia and radius prospectively in subjects with SCI. SUBJECTS: In total, 10 individuals with an acute SCI. METHODS: Trabecular and compact bone density of the tibia and radius by peripheral quantitative computerised tomography. RESULTS: Analysis of the individual gradients of the curve coefficient showed changes in trabecular bone between -0.19 and -2.46 and in cortical bone between +0.07 and -0.93 in the tibia within 34 months after the SCI. Both trabecular and cortical bone showed a group mean loss of 99 mg/cm(3). No changes were observed in the radius. CONCLUSION: There is a major decrease in tibia mineral density over 3 years; however, no change is observed for the radius mineral content. Large interindividual differences existed in the patterns of loss in the tibia bone substance after SCI. These patterns indicate that there is no steady state of bone mineral density following 3 years of spinal cord injury.

In vivo precision of quantitative shoulder cartilage measurements, and changes after spinal cord injury.

Recent advances in MRI have enabled the quantitative assessment of articular cartilage morphology in human joints. In this study, we tested the hypothesis that the precision of quantitative shoulder cartilage measurements is sufficient to detect changes between and within patients, and that shoulder cartilage thickness in paraplegic patients increases due to increased loading. We imaged the shoulders of seven healthy volunteers four times using a coronal 3D, fat-suppressed, gradient-echo sequence. The humeral head cartilage in seven paraplegic patients was evaluated soon after injury and 1 year post injury. A precision of 4.5% (root mean square (RMS) average coefficient of variation (CV) %) was found for shoulder cartilage thickness measurements in the humeral head. Whereas a significant decrease of cartilage thickness (-11%, P < 0.05) was observed in the knee, there was no significant change in articular cartilage thickness in the shoulder (-1.1%). Our data show, for the first time, that articular cartilage of the humeral head can be quantified with acceptable precision in vivo. It was demonstrated that, in contrast to the knee, the articular cartilage morphology of the humeral head changes very little (i.e., there is no significant increase or decrease in thickness) after spinal cord injury (SCI).

Prediction of elasticity constants in small biomaterial samples such as bone. A comparison between classical optimization techniques and identification with artificial neural networks.

Measuring the elasticity constants of biological materials often sets important constraints, such as the limited size or the irregular geometry of the samples. In this paper, the identification approach as applied to the specific problem of accurately retrieving the material properties of small bone samples from a measured displacement field is discussed. The identification procedure can be formulated as an optimization problem with the goal of minimizing the difference between computed and measured displacements by searching for an appropriate set of material parameters using dedicated algorithms. Alternatively, the backcalculation of the material properties from displacement maps can be implemented using artificial neural networks. In a practical situation, however, measurement errors strongly affect the identification results, calling for robust optimization approaches in order accurately to retrieve the material properties from error-polluted sample deformation maps. Using a simple model problem, the performances of both classical and neural network driven optimization are compared. When performed before the collection of experimental data, this evaluation can be very helpful in pinpointing potential problems with the envisaged experiments such as the need for a sufficient signal-to-noise ratio, particularly important when working with small tissue samples such as specimens cut from rodent bones or single bone trabeculae.

Longitudinal analysis of cartilage atrophy in the knees of patients with spinal cord injury.

OBJECTIVE: A previous cross-sectional study indicated that the morphology of patellar and tibial cartilage is subject to change after spinal cord injury (SCI). The aim of this study was to perform a longitudinal analysis of cartilage atrophy in all knee compartments, including the femoral condyles, in SCI patients over 12 months. METHODS: The right knees of 9 patients with complete, traumatic SCI were examined shortly after the injury (mean +/- SD 9 +/- 4 weeks) and at 6 and 12 months postinjury. Three-dimensional morphology of the patellar, tibial, and femoral cartilage (mean and maximum thickness, volume, and surface area) was determined from coronal and transversal magnetic resonance images (fat-suppressed gradient-echo sequences) using validated postprocessing techniques. RESULTS: The mean thickness of knee joint cartilage decreased significantly during the first 6 months after injury (range 5-7%; P < 0.05). The mean change at 12 months was 9% in the patella, 11% in the medial tibia, 11% in the medial femoral condyle, 13% in the lateral tibia, and 10% in the lateral femoral condyle (P < 0.05 for all compartments). CONCLUSION: This is the first report of a longitudinal analysis of cartilage atrophy in patients with SCI. These data show that human cartilage atrophies in the absence of normal joint loading and movement after SCI, with a rate of change that is higher than that observed in osteoarthritis (OA). A potential clinical implication is that cartilage thinning after SCI may affect the stress distribution in the joint and render it vulnerable to OA. Future studies should focus on whether specific exercise protocols and rehabilitation programs can prevent cartilage thinning.

Effect of electrical stimulation-induced cycling on bone mineral density in spinal cord-injured patients.

BACKGROUND: Bone atrophy in spinal cord-injured people (SCI) is, among other factors, caused by immobilization and is initiated shortly after the injury. The present study measured the effect of an functional electrical stimulation (FES)-cycling intervention on bone mineral density (BMD) of the tibia in recently injured SCI people. METHODS: As soon as possible after the injury (mean 4.5 weeks), para- and tetraplegic patients were recruited into an intervention and control group comparable with regard to gender, age, and lesion level. The intervention consisted of 30-min functional electrical stimulation-cycling three times a week for the duration of their primary rehabilitation (mean = 6 months). Computed tomography (CT) scans of the right tibia diaphysis were taken at the beginning and at the end of the intervention. Bone mineral density of cortical bone was calculated from the CT scans. RESULTS: A total of 38 subjects (19 in each group) were included in the study. Both groups showed a reduction in tibial cortical BMD of 0-10% of initial values within 3-10 months. The mean decrease in BMD was 0.3% (+/- 0.6) per month in the intervention group and 0.7% (+/- 0.8) in the control group. This difference did not reach statistical significance. Decrease of BMD was linearly correlated to initial BMD and age in the pooled data of both groups; subjects who had a high initial BMD and/or were older lost more bone. In neither group was bone loss associated with duration of immobilization nor lesion level. CONCLUSIONS: Functional electrical stimulation-cycling applied shortly after SCI did not significantly attenuate bone loss.

Knee cartilage of spinal cord-injured patients displays progressive thinning in the absence of normal joint loading and movement.

OBJECTIVE: Alterations in the morphologic, biochemical, and mechanical properties of cartilage occur after unloading and immobilization in animals. However, the findings have been inconsistent and it is unclear whether such changes also take place in humans. This study tested the hypothesis that progressive thinning of knee joint cartilage is observed after spinal cord injury. METHODS: In this in vivo study, knee cartilage was assessed in patients with complete, traumatic spinal cord injury at 6 (n = 9), 12 (n = 11), and 24 months (n = 6) after injury. Morphologic parameters of the knee cartilage (mean and maximum thickness as well as surface area) were computed from magnetic resonance imaging (MRI) data, and results were compared with those in young, healthy volunteers (n = 9). RESULTS: After 6 months of injury, the mean articular-cartilage thickness was significantly less in the patella and medial tibia (decrease of 10% and 16%, respectively; P < 0.05), but not in the lateral tibia (decrease of 10%), compared with the MRI findings in healthy volunteers. After 12 and 24 months of injury, the differences amounted to a reduction of 21% and 23%, respectively, in the patella, 24% and 25%, respectively, in the medial tibia, and 16% and 19%, respectively, in the lateral tibia. The changes were significant in all 3 surfaces of the spinal cord-injured joint cartilage (P < 0.05-0.01). CONCLUSION: Our data show, for the first time, that progressive thinning (atrophy) of human cartilage occurs in the absence of normal joint loading and movement. This may have important implications for patient management, in particular for spinal cord-injured patients and patients who are immobilized after surgery.

The effects of immobilization on the characteristics of articular cartilage: current concepts and future directions.

OBJECTIVE: The purpose of this paper is to review current data and concepts concerning the effect of immobilization on articular cartilage in animal models. We also evaluate the methods to measure articular cartilage changes in humans. METHODS: Studies looking at the effects of immobilization on morphological, biochemical, and biomechanical characteristics of articular cartilage are reviewed. RESULTS: Articular cartilage changes in immobilized animals include altered proteoglycan synthesis, as well as thinning and softening of the tissue. The overall thickness of articular cartilage in the knee decreases up to 9% after 11 weeks of immobilization and the deformation rate under test load increases up to 42%. Quantitative data about changes in human articular cartilage following immobilization are not available. This is mainly due to the lack of an accurate, reproducible, and non-invasive method to characterize articular cartilage. DISCUSSION: An understanding of the alterations in articular cartilage following short and long term immobilization in humans is essential for the optimization of rehabilitation programs. Refined imaging techniques combined with state-of-the-art visualization tools could allow the systematical monitoring of articular cartilage morphology changes in immobilized humans.

Effects of shoe sole construction on skeletal motion during running.

PURPOSE: The purpose of this study was to quantify effects of shoe sole modification on skeletal kinematics of the calcaneus and tibia during the stance phase of running. METHODS: Intracortical bone pins with reflective marker triads were inserted under standard local anesthetic into the calcaneus and tibia of five healthy male subjects. The three-dimensional tibiocalcaneal rotations were determined using a joint coordinate system approach. Three shoe sole modifications were tested with different sole geometry: a lateral heel flare of 25 degrees (flared), no flare 0 degrees (straight), and a rounded sole. RESULTS: The results showed that these shoe sole modifications did not change tibiocalcaneal rotations substantially. The shoe sole effects at the bone level were small and unsystematic (mean effects being less than 1 degrees ) compared with the differences between the subjects (up to 7 degrees ). Shoe eversion measured simultaneously with shoe markers showed no systematic shoe sole effects. A comparison of shoe and bone results showed the total shoe eversion and maximum shoe eversion velocity to be approximately twice as large as the respective measurements based on bone markers (correlations being r = 0.79 for maximum eversion velocity; r = 0.88 for total eversion), indicating that there may be a relationship or coupling effect between the shoes and the bone. CONCLUSIONS: It is concluded that the tibiocalcaneal kinematics of running may be individually unique and that shoe sole modifications may not be able to change them substantially.

Functional donor-site morbidity during level and uphill gait after a gastrocnemius or soleus muscle-flap procedure.

BACKGROUND: There is only limited objective information about functional donor-site morbidity after harvest of one head of the triceps surae muscles to cover a severe soft-tissue defect of the leg. The purpose of the present study was to investigate whether a functional deficit is present during level and uphill walking after such a procedure. METHODS: Five subjects who had completely recovered from the initial injury were studied with use of comprehensive gait analysis during free level, fast level, and uphill walking on a ramp at a 10 degrees inclination. RESULTS: Gait analysis revealed no relevant donor-site morbidity affecting level gait at a free walking speed (mean, 1.27 m/sec; range, 1.18 to 1.40 m/sec). When the subjects walked at a higher velocity (mean, 1.89 m/sec; range, 1.58 to 2.43 m/sec), an asymmetry of the ground-reaction forces was seen. The second vertical peak force during push-off was reduced by a mean of 7.3% (range, 0.94% to 12.24%), and the impulse in the direction of progression was reduced by a mean of 8.7% (range, 0.13% to 17.87%) on the affected side (p = 0.04). During uphill walking, a compensatory strategy to reduce the demand on the posterior calf muscles was seen in all subjects-that is, they shortened the length of the step on the contralateral side by a mean of 3.9 cm (range, 2.2 to 6.2 cm), which corresponded to a mean side-to-side difference of 5.6% (range, 2.18% to 6.18%) (p = 0.04). A calcaneal motion pattern, denoted as increased ankle dorsiflexion, was seen in three of the five subjects during uphill walking as a sign of decreased function of the posterior calf muscles. Two of them (both with a soleus flap) also had a calcaneal pattern during fast gait. CONCLUSIONS: We concluded from this study that the functional donor-site morbidity after harvest of one head of the triceps surae muscles is mild in subjects who have had a complete recovery from their initial injury. Normal level gait is possible. However, deficits are seen in more demanding tasks such as fast walking or uphill walking.

Investigation of bone changes in microgravity during long and short duration space flight: comparison of techniques.

BACKGROUND: Loss of bone mass is a continuing problem in long-term space flight. Although counter-measure programmes have been developed, effective assessment of these programmes is hampered by a lack of monitoring techniques that can be used in-flight. MATERIALS AND METHODS: Three techniques were used to evaluate changes in bone during two missions of 180 and 20 days to the MIR space station, involving three subjects. Dual energy X-ray absorptiometry (DXA) was used before and after flight to measure whole body and regional bone mineral density (BMD). Ultrasonic measurements of velocity (SOS) and broadband attenuation (BUA) of the calcaneus were measured during the 180 day mission and before and after the 20 day mission. Phase velocity of flexural waves in the tibia was also measured on the same days as the ultrasonic measurements of the calcaneus. RESULTS: DXA measurements demonstrated significant variation between different sites in the body for changes in BMD, with the greatest changes occurring in the lumbar spine and proximal femur. There was a trend for increasing phase velocity in the tibia during the 180 mission, but this was not significant. BUA and SOS measurements of the calcaneus showed consistent but divergent patterns of changes during the mission. CONCLUSION: Although in-flight measurements of bone using ultrasound or phase velocity may provide information on the kinetics of bone loss in space flight, the heterogeneity of response in the skeleton means that it is difficult to predict overall bone loss from measurements at one particular site.

[Effect of shoe shaft and shoe sole height on the upper ankle joint in lateral movements in floorball (uni-hockey)]. / Einfluss des Schuhschaft- und der Schuhsohlenhöhe auf das obere Sprunggelenk bei Seitwärtsbewegung im Floorball (Unihockey).

Improvements of the shoe design to increase ankle stability have been discussed for a number of years. This accounts also for floorball where the incidence of ankle injuries is very high. The purpose of the present study was to describe the influence of the shoe upper on a typical floorball sideward cutting movement. A film analysis was conducted (200 Hz) where the achilles tendon angle beta was measured on the shoe as well as within the shoe. Subjects were twelve active floorball players who performed a defined sideward cutting movement with a low-cut and high-cut shoe as well as in the barefoot condition. The results of part 1 of the study showed the stabilizing effect of the shoe upper with respect to supination. The range of supination of the barefoot inside the shoe (between touchdown and maximum) of the low-cut shoe (23.7 degrees +/- 5.7 degrees) was decreased when using the high-cut shoe (12.3 degrees +/- 4.6 degrees). In addition, a reduced shoe sole thickness and an anisotropic shoe sole design showed reducing effects on supination. Part 2 of the study showed significant differences in supination between two different touchdown techniques. With a forefoot touchdown supination was much less (12.0 degrees +/- 4.8 degrees) than with a touchdown in the neutral position (31.7 degrees +/- 4.2 degrees; p < 0.001). Furthermore, possibilities to improve the design of future floorball shoes are discussed.

Effects of 17 days bedrest on the maximal voluntary isometric torque and neuromuscular activation of the plantar and dorsal flexors of the ankle.

Maximal voluntary isometric torque values of the ankle plantar (Tim,PF) and dorsal flexors (Tim,DF) were assessed in eight healthy adult males at 5 degrees and 15 degrees of dorsal flexion (DF) and at 5 degrees, 15 degrees and 25 degrees of plantar flexion (PF) with the knee at right angles, before (two times), during (three times) and after (three times) 17 days of 6 degrees head-down tilt bedrest (BR). Integrated electromyograms (iEMG) were also recorded from the gastrocnemius medialis and tibialis anterior. Tim,PF and the iEMG of the gastrocnemius medialis were significantly larger (by 14% and by 27%, respectively) at the end of recovery than before BR. This was probably the consequence of training and/or habituation leading to: (1) increased activation of the plantar flexors; and (2) decreased co-activation of the antagonist muscles. Neither Tim,DF nor the tibialis anterior iEMG changed significantly. The effects of BR on muscle performance were evaluated as follows. The net torque generated by a given muscle group was assumed to be the algebraic sum of the torque generated by the agonists and by the antagonists. Thus, for the plantar flexors Tim,PF = alpha iEMGGm - beta iEMGTa, where: (1) iEMGGm and iEMGTa are the iEMGs of gastrocnemius medialis and of tibialis anterior during maximal PF; and (2) the constants alpha and beta represent the electromechanical coupling of the plantar (alpha) and dorsal (beta) flexors. Similarly for the dorsal flexors: Tim,DF = beta iEMGTa - alpha iEMGGm, where iEMGTa and iEMGGm are the iEMGs of tibialis anterior and gastrocnemius medialis during maximal DF. Torque and iEMG values were assessed for all subjects under all experimental conditions. Thus, since the biomechanical leverage of the system was constant, alpha and beta could be calculated. During BR, alpha decreased by 25% and it dropped by a further 30% during recovery. In contrast, beta remained almost unchanged. This suggests that, in spite of training and/or habituation, BR significantly impaired the maximal isometric performance of the plantar flexors, an effect that continued during the initial 10 days of recovery.

Cross stitch peripheral tendon repair: a mechanical comparison with core stitch techniques.

The purpose of this experimental study was to compare certain mechanical properties of a true epitendineal cross stitch suture with simple and double locking core tendon repairs. Using tensile strength and tendon lengthening until gap formation as measurement parameters, these three types of repair were tested in human flexor and extensor tendons from fresh cadavers. The peripheral cross stitch and the locked core repairs were found to have a greater lengthening capacity than the simple core suture, whereas the latter significantly better withstood axial load. Our findings established that, at least when used as a true epitendinous suture, the cross stitch technique alone was not suited for the repair of severed tendons. However, its design is particularly useful in preventing the suture site from potentially restrictive bulking.

Longitudinal changes in bone in men with spinal cord injury.

INTRODUCTION: Quantitative bone assessment today is primarily based on the analysis of bone mineral density (BMD). The geometric and structural properties of bone, which are important parameters for skeletal strength, are generally not considered in the routine clinical assessment of spinal cord injury-related osteopenia. OBJECTIVE: To study changes in structural and geometric properties of tibia bone longitudinally by means of peripheral quantitative computerized tomography and a biomechanical test method (bone stiffness measurement device Swing) in 12 subjects with spinal cord injury. DESIGN: Measurements were conducted in the 5th week and around the 104th week after the spinal cord injury in a university hospital. RESULTS: Paired Student's t-tests showed a significant decrease in trabecular (p < 0.05) and cortical bone (p < 0.05), as well as a significant decrease in geometric properties of tibia bone (p < 0.05) within two years after the spinal cord injury. Phase velocity propagation changed in three subjects within two years following the spinal cord injury. CONCLUSIONS: This study indicates that beside changes in tissue composition, changes in bone geometric indices and in structural properties occur in the lower extremity after a spinal cord injury. In the tibia, consideration of geometric and biomechanical parameters of bone combined with bone mineral density measurements could result in an improved screening for spinal cord injury-related osteopenia and the prediction of fracture risk in spinal cord injury.

Bone mineral density in upper and lower extremities during 12 months after spinal cord injury measured by peripheral quantitative computed tomography.

OBJECTIVE: To evaluate the loss of trabecular and cortical bone mineral density in radius, ulna and tibia of spinal cord injured persons with different levels of neurologic lesion after 6, 12 and 24 months of spinal cord injury (SCI). DESIGN: Prospective study in a Paraplegic Centre of the University Hospital Balgrist, Zurich. SUBJECTS AND METHODS: Twenty-nine patients (27 males, two females) were examined by the highly precise peripheral quantitative computed tomography (pQCT) soon after injury and subsequently at 6, 12 and in some cases 24 months after SCI. Using analysis of the bone mineral density (BMD), various degrees of trabecular and cortical bone loss were recognised. A rehabilitation program was started as soon as possible (1-4 weeks) after SCI. The influence of the level of neurological lesion was determined by analysis of variance (ANOVA). Spasticity was assessed by the Ashworth Scale. RESULTS: The trabecular bone mineral density of radius and ulna was significantly reduced in subjects with tetraplegia 6 months (radius 19% less, P<0.01; ulna 6% less, P>0.05) and 12 months after SCI (radius 28% less, P<0.01; ulna 15% less, P<0.05). The cortical bone density was significantly reduced 12 months after SCI (radius 3% less, P<0.05; ulna 4% less, P<0.05). No changes in BMD of trabecular or cortical bone of radius and ulna were detected in subjects with paraplegia. The trabecular BMD of tibia was significantly reduced 6 months (5% less, P<0.05) and 12 months after SCI (15% less, P<0.05) in all subjects with SCI. The cortical bone density of the tibia only was decreased after a year following SCI (7% less, P<0.05). No significant difference between both groups, subjects with paraplegia and subjects with tetraplegia was found for tibia cortical or trabecular BMD. There was no significant influence for the physical activity level or the degree of spasticity on bone mineral density in all subjects with SCI. CONCLUSIONS: Twelve months after SCI a significant decrease of BMD was found in trabecular bone in radius and in tibia of subjects with tetraplegia. In subjects paraplegia, a decrease only in tibia BMD occurred. Intensity of physical activity did not significantly influence the loss of BMD in all subjects with para- and tetraplegia. However, in some subjects regular intensive loading exercise activity in early rehabilitation (tilt table, standing) can possibly attenuate the decrease of BMD of tibia. No influence was found for the degree of spasticity on the bone loss in all subjects with SCI.

Movement coupling at the ankle during the stance phase of running.

The purpose of this study was to quantify movement coupling at the ankle during the stance phase of running using bone-mounted markers. Intracortical bone pins with reflective marker triads were inserted under standard local anaesthesia into the calcaneus and the tibia of five healthy male subjects. The three-dimensional rotations were determined using a joint coordinate system approach. Movement coupling was observed in all test subjects and occurred in phases with considerable individual differences. Between the shoe and the calcaneus coupling increased after midstance which suggested that the test shoes provided more coupling for inversion than for eversion. Movement coupling between calcaneus and tibia was higher in the first phase (from heel strike to midstance) compared with the second phase (from midstance to take-off). This finding is in contrast to previous in-vitro studies but may be explained by the higher vertical loads of the present in-vivo study. Thus, movement coupling measured at the bone level changed throughout the stance phase of running and was found to be far more complex than a simple mitered joint or universal joint model.

Estimation of geometric properties of cortical bone in spinal cord injury.

OBJECTIVE: To evaluate structural and geometrical properties of the tibia shaft in subjects with spinal cord injury (SCI) and subjects without SCI and to estimate the potential usefulness of a multimodal approach to diagnosing osteoporosis in SCI. DESIGN: A cross-sectional study of randomly selected SCI and non-SCI subjects. METHODS: Measurements of bone geometric indices by computed tomography, and calculated bending stiffness with a biomechanical testing method. SETTING: An SCI center hospital. SUBJECTS: Ten men without known orthopedic or neurologic impairments (controls), 10 men with SCI who had a history of lower extremity pathologic fracture since SCI, and 10 men with SCI who had never had lower extremity pathologic fracture. RESULTS: Analysis of geometric and structural indices of subjects' tibias found a significant difference in all geometric indices between controls and the SCI subjects with pathologic fracture history. Between the controls and the SCI subjects with no fracture history, however, differences were found only in cross-sectional area and calculated bending stiffness. CONCLUSION: Structural analysis of leg bone, combined with measurement of bone density, may improve the ability to assess fracture risk in patients with SCI.

[Snowboarding accidents]. / Snowboard-Unfälle.

The present review summarises the related literature of the last ten years with request to snowboarding accidents. Sport accident statistics of snowboarding show high and increasing numbers of injuries. Already snowboarding ranks third of all sport accidents in Switzerland. According to the literature the injury risk in snowboarding is twice that of skiing, although the injuries are less serious. About 50% of the injured snowboarders are beginners. Beginners have a higher risk of injury than more advanced snowboarders. Additionally, and a relative large part of them are injured the first day of their snowboard career. The pattern of injury has changed over the last years. Today, injuries to the lower extremities account no longer for more than 50% but are now decreased to about 25%. Nowadays, wrist, knee, ankle, and shoulder are the most frequently injured body parts. It is the authors opinion that with up-to-date protectors, release bindings, and training of falling techniques the numbers and seriousness of injuries could be reduced, in particular injuries to the wrist and ankle.