Entwicklung und Anpassung der Biegefestigkeit des Extremitätenskelettes durch Training am Beispiel der Tibia

Isokinetic resistance training increases tibial bending stiffness in young women

Bone mineral content (BMC) and bone mineral density (BMD) are common but imperfect surrogate measures of bone strength. The mechanical response tissue analyzer is a device that measures long bone bending stiffness (EI), which strongly predicts bone breaking strength. We hypothesized that isokinetic resistance training of the knee flexor and extensor muscles would increase tibial EI, BMC, and BMD in young women. Fifty-two women, aged 18-26 years, performed concentric (CON, n = 30) or eccentric (ECC, n = 22) isokinetic resistance training with the nondominant leg three times per week for 20 weeks. Before and after the training period, subjects were tested for CON and ECC peak torque of the knee flexor and extensor muscles with isokinetic dynamometry, tibial BMC and BMD using dual-energy X-ray absorptiometry, and tibial EI using mechanical response tissue analysis. Both training groups increased CON (15-21%) and ECC (17-31%) peak torque vs. the untrained leg. Tibial EI increased in the entire cohort (26%) and in each training group (CON 34%, ECC 16%) vs. the untrained tibia. Tibial BMC and BMD increased in the trained and untrained tibiae, with no significant differences between limbs. No differential tibial EI or bone mineral outcomes were observed between the CON and ECC training groups. In summary, CON and ECC isokinetic resistance training increased tibial EI, but not BMC or BMD, in young women.

Flexural wave propagation velocity and bone mineral density in females with and without tibial bone stress injuries

STUDY DESIGN

Case-control nonexperimental design.

OBJECTIVES

To compare flexural wave propagation velocity (FWPV) and tibial bone mineral density (BMD) in women with and without tibial bone stress injuries (BSIs).

BACKGROUND

Physical therapists, particularly in military and sports medicine settings, routinely diagnose and manage stress fractures or bone stress injuries. Improved methods of preparticipation quantification of tibial strength may provide markers of BSI risk and thus potentially reduce morbidity.

METHODS AND MEASURES

Bone mineral density, FWPV, bone geometry, and historical variables were collected from 14 subjects diagnosed with tibial BSIs and 14 age-matched controls; all 28 were undergoing military training.

RESULTS

No difference was found between groups in FWPV and tibial BMD when analyzed with t tests (post hoc power = 0.89 and 0.81, respectively). Furthermore, no difference was found in tibial length, tibial width, femoral neck BMD, and lumbar spine BMD among the groups. There were no differences between the 2 groups in smoking history, birth control pill use, and onset of menarche. Finally, sensitivity and positive likelihood ratios for FWPV (0.14 and 0.63), tibial BMD (0.0 and 0.0), and lumbar BMD (0.18 and 2.0) were low, while specificity was high (0.77, 0.93, and 0.91, respectively).

CONCLUSION

Current bone analysis devices and methods may not be sensitive enough to detect differences in tibial material and structure; local stresses on bone may be more important in the development of BSIs than the overall structural stiffness.

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.

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.

Changes of tibia bone properties after spinal cord injury: effects of early intervention

OBJECTIVE

To evaluate the effectiveness of an early intervention program for attenuating bone mineral density loss after acute spinal cord injury (SCI) and to estimate the usefulness of a multimodality approach in diagnosing osteoporosis in SCI.

DESIGN

A single-case, experimental, multiple-baseline design.

SETTING

An SCI center in a university hospital.

METHODS

Early loading intervention with weight-bearing by standing and treadmill walking.

PATIENTS

Nineteen patients with acute SCI.

OUTCOME MEASURES

(1) Bone density by peripheral computed tomography and (2) flexural wave propagation velocity with a biomechanical testing method.

RESULTS

Analysis of the bone density data revealed a marked decrease of trabecular bone in the nonintervention subjects, whereas early mobilized subjects showed no or insignificant loss of trabecular bone. A significant change was observed in 3 of 10 subjects for maximal and minimal area moment of inertia. Measurements in 19 subjects 5 weeks postinjury revealed a significant correlation between the calculated bending stiffness of the tibia and the maximal and minimal area moment of inertia, respectively.

CONCLUSION

A controlled, single-case, experimental design can contribute to an efficient tracing of the natural history of bone mineral density and can provide relevant information concerning the efficacy of early loading intervention in SCI. The combination of bone density and structural analysis could, in the long term, provide improved fracture risk prediction in patients with SCI and a refined understanding of the bone remodeling processes during initial immobilization after injury.