Foot stiffness under different speed compression. Experimental study

Leg stiffness is an important parameter when performing various motions. Ground reaction force, duration of support, displacement of the body mass center as well as step frequency during running or jumping depend on stiffness of the leg (McMahon, 1990; Farley, 1996; Granata, 2001). It is not clear yet how foot stiffness changes with deformation, how it is related to the deformation speed, to the number of repetitions, what influence do soft tissues have on stiffness of a foot. The aim of this research is to determine whether foot compression-displacement dependency changes when compressing foot repeatedly, does foot stiffness depend on compression speed. The specimen was a right foot with normal longitudinal arch from a Caucasian female. 25 kN force Tinius Olsen H25K-T testing machine was used in the study. The compression rate was 25 mm/min, 50 mm/min, 100 mm/min and 500 mm/min until 1000 N force was reached. The deformation and stiffness of the foot at different compression speeds were analyzed when 400 N and 700 N force was reached. Despite the compression speed differences the values of Intraclass correlation coefficient show data repeatability when compressing the foot repeatedly. The foot stiffness remained stable at 25-100 mm/min foot compression speed. At compression speed higher than 100 mm/min foot stiffness decreased significantly. The regression equation was derived to describe dependence between stiffness and relative deformation of foot with soft tissue

Foot stiffness under different speed compression: experimental study

Leg stiffness is an important parameter when performing various motions. Ground reaction force, duration of support, displacement of the body mass center as well as step frequency during running or jumping depend on stiffness of the leg (McMahon, 1990; Farley, 1996; Granata, 2001). It is not clear yet how foot stiffness changes with deformation, how it is related to the deformation speed, to the number of repetitions, what influence do soft tissues have on stiffness of a foot. The aim of this research is to determine whether foot compression-displacement dependency changes when compressing foot repeatedly, does foot stiffness depend on compression speed. The specimen was a right foot with normal longitudinal arch from a Caucasian female. 25 kN force Tinius Olsen H25K-T testing machine was used in the study. The compression rate was 25 mm/min, 50 mm/min, 100 mm/min and 500 mm/min until 1000 N force was reached. The deformation and stiffness of the foot at different compression speeds were analyzed when 400 N and 700 N force was reached. Despite the compression speed differences the values of Intraclass correlation coefficient show data repeatability when compressing the foot repeatedly. The foot stiffness remained stable at 25-100 mm/min foot compression speed. At compression speed higher than 100 mm/min foot stiffness decreased significantly. The regression equation was derived to describe dependence between stiffness and relative deformation of foot with soft tissue

Biomechanical Aspects of Locking Reconstruction Plate Positioning in Osteosynthesis of Transverse Clavicle Fracture

The aim of this study was to evaluate and compare the biomechanical effects of locking reconstruction plate positioning on the osteosynthesis of clavicle midshaft simulated transverse fractures. Material and Methods. Twelve synthetic clavicles with simulated midshaft transverse fractures were repaired with a 3.5-mm locking reconstruction plate in the anteroinferior or the superior position. The clavicles were randomly assigned to 2 groups (6 per group). Each repaired clavicle was tested in cantilever bending by using the universal testing machine. The maximal load and the displacement of the specimens at a load of 40 N were recorded for each group. Results. The anteroinferior plating osteosynthesis with a 3.5-mm locking reconstruction plate could bear an average maximal load of 183.3 N (SD, 11.3); the corresponding load for the superior plating osteosynthesis with the identical implants was 444.8 N (SD, 102.3), and the mean displacement was 1.5 mm (SD, 0.5) and 0.7 mm (SD, 0.2), respectively. Conclusions. The superior plating osteosynthesis of simulated midshaft transverse clavicle fractures with the 7-hole 3.5-mm locking reconstruction plate had a significantly higher bending (from top to bottom) load to failure in comparison with the anteroinferior plating osteosynthesis of the clavicle with the identical implants. Clavicles plated with the 7-hole 3.5-mm locking reconstruction plate at the superior aspect exhibited a significantly greater biomechanical stability at a load of 40 N than those plated at the anteroinferior aspect

Pathophysiology of acute spinal cord injury

Spinal cord injury is one of the most devastating of all traumatic conditions that can be encountered by patients. Over the past years much research has been performed on elucidating the mechanisms of spinal cord injury. Experimental and clinical studies have suggested that acute spinal cord injury is a twostep process involving primary and secondary mechanisms. Primary injury of the spinal cord refers to the initial mechanical damage due to local deformation of the spine. Direct compression and damage of neural elements and blood vessels by fractured and displaced bone fragments or disc material occur after mechanical trauma. The secondary mechanism is initiated by the primary injury. The secondary mechanism includes a cascade of biochemical and cellular processes, such as electrolyte abnormalities, formation free radicals, vascular ischemia, edema, posttraumatic inflammatory reaction, apoptosis or genetically programmed cell death and another processes. This review describes the pathophysiology of acute spinal cord injury. Knowledge of the pathophysiology of the acute spinal cord injury is crucial for successful management of the patients with these injuries

Upper cervical spine injuries and their diagnostic features

The upper cervical spine includes the articulations of the occiput with atlas and the atlas with the axis, as well as the bony structures of the base of the skull, axis, and atlas. The unique anatomy of the upper cervical spine and the typical mechanisms of injury yield a predictable variety of injury patterns. Injuries to this area include occipital condyle fractures, occipitoatlantal dislocations, subluxations and dislocations of the atlantoaxial articulation, atlas fractures, odontoid fractures, and fractures of the arch of the axis. Injuries to this region are relatively common and can be easily overlooked because patients with the upper cervical injury may have an associated head injury, which can alter their level of consciousness and complicate obtaining an accurate history and physical examination. The complex regional anatomy and overlying structures make plain radiographic images difficult to interpret. Delayed recognition can result in significant disability. A thorough understanding of the clinical presentation, radiographic assessment, and mechanisms of injury can minimize morbidity and enhance treatment effectiveness for the more common upper cervical ligamentous and bony injuries

Gerokai pasislinkusių kaklo antrojo slankstelio danties lūžių gydymo ypatybės

Objective. The purpose of this study was to determine the treatment features of odontoid fractures with a significant displacement. Material and methods. Thirty-seven patients with acute odontoid fractures were treated in Kaunas University of Medicine Hospital between 1998 and 2003. Seventeen persons with displacement of fragments less than 5 mm or 5 mm (according to E. A. Seybold and J. C. Bayley method) were in the first group. Twenty patients with displacement of fragments more than 5 mm were in the second group. The attempt of closed reduction of the cervical spine axis was performed for all patients. If successful closed reduction was achieved, patients were placed in halo-vest device for 8 weeks. If closed reduction failed, patient was operated according to W. E. Gallie. Postoperatively, all patients wore a halo-vest device during the first 8 weeks. Results. Demographics including age, sex, neurological condition, and associated spinal fractures were similar in patients from these groups (p>0.05). Successful closed reduction of the cervical spine axis was achieved in 11 (64.7%) patients from the first group and in 13 (65%) patients from the second group (p>0.05). Six (35.3%) patients from the first group and seven (35%) from the second group were treated with immediate C1–C2 posterior fusion (p>0.05). Two (16.7%) from twelve patients from the second group were treated by external immobilization by halo-vest device and had nonunion of fracture 8 weeks after the treatment. All operated patients had a solid fusion. Conclusions. If closed reduction of the odontoid fracture with a significant displacement was achieved then external immobilization by halo-vest device can be used [...]

Osteosynthesis of the clavicle after osteotomy in brachial plexus surgery: A biomechanical cadaver study

Objective: The aim of this study was to evaluate and compare the biomechanical effects of locking plate superior and anteroinferior positioning on the osteosynthesis of the clavicles osteotomized obliquely. Materials and methods: Ten matched pairs of fresh cadaveric clavicles osteotomized through the mid-shaft obliquely were repaired with a titanium 7-hole 3.5-mm reconstruction locking plate in the superior or the anteroinferior position. The maximal failure loads and the displacement of the specimens at 166 N, 183 N, 203 N loads were recorded by the machine in 3-point cantilever bending. Bending failure stiffness was calculated between 10–150 N and 151 N to maximal bending failure loads. Results: The mean maximal failure load was 396.2 N (SD, 117.3) for superior constructs and 220.1 N (SD, 51.1) for anteroinferior one (P < 0.05). There was significant difference in displacement between superior and anteroinferior plated specimens at 183 N (6.3 [SD, 2] vs. 9.9 [SD, 3.6]) and 203 N (6.4 [SD, 0.6] vs. 11.7 [SD, 6.6]) loads; P < 0.05). Mean bending failure stiffness between 151 N and maximal loads was 22.6 N/mm (SD, 13.2) for superior plates and 11 N/mm (SD, 9) for anteroinferior plated clavicles (P < 0.05). Conclusions: The superior plating of obliquely osteotomized clavicles with the titanium 7-hole 3.5-mm locking reconstruction plate had a significantly greater biomechanical stability at fixed loads of 183 N and 203 N than the anteroinferior plating in the inferior directed cantilever bending. The superior plating osteosynthesis exhibited a significantly greater stiffness from 151 N to maximal bending failure loads as well