Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Motility of the upper extremities is the sum of movements of an open kinematic chain made up of the hands and the lower and upper arms in the humero-scapular joints which are integrated in the closed kinematic chains of the bilateral symmetrical shoulder girdles. Each shoulder girdle assembles three kinematic links (scapula, clavicle, hemithorax), with three joints (sternoclavicular, acromioclavicular, thoraco-scapular), creating a three-bar linkage. This linkage may be characterized as an effective transformer of motion with 11 degrees of freedom ensuring wide ranges of motions. This motion-transformer acts strictly as a guided linkage, allowing a precise reference between initial motion and functional result. The operative transfixation of acromioclavicular joints in the case of either dislocation or arthrodesis, also of the sternoclavicular joint reduces the degree of kinematic freedom from 11 to 8 and alters the shoulder as a motion-transformer into a rigid girdle with a variable length of support, with degeneration of the shoulder linkage. Surgical treatment of acromioclavicular dislocation with coraco-clavicular fusion using a screw as described by Bosworth produces osseus strain and a girdle under twofold static in determination (F = -2) with pressure forces causing bone deformation, loosening of the screw and fatigue fractures. This operation therefore cannot yet be recommended. Additional cadaver experiments with means of strain gauge cells have shown that lengthening of the clavicle by 0.5 cm increases the forces transmitted from the elevated arm to the hemithorax by 16%. Shortening of the osteotomized clavicle by only 1 cm leads to an increase of these forces by about 40%.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:[kinematic consideration of the shoulder girdle and its consequences on common surgical methods]. 194 8

L-rod procedures with sublaminar wiring have become widespread in orthopaedic practice, and serious mechanical problems involving fatigue failure, creep, and fixation have been reported. To address these problems, numerical [corrected] analysis was developed to provide estimates for the maximum bending stresses, approximately equal to maximum tensile stresses, in L-rods subject to various axial loads and postoperative Cobb angles. The superior load capacity of L-rods made from MP35N multiphase alloy compared with 316L stainless steel was demonstrated. Bending stresses in excess of the fatigue limit were predicted for eight patients with broken rods, suggesting that such failures might be prevented by prior analysis. This analytic approach provides a foundation for future studies of custom-designed L-rods and perhaps the successful use of L-rods without arthrodesis.
 ...
PMID:Numerical [corrected] analysis of the load capacity of the human spine fitted with L-rod instrumentation. 228 72

Posterior arthrodesis is a preferred treatment for posttraumatic instability of the cervical spine. While most surgical constructs yield predictably high rates of fusion in satisfactory alignment, certain injury patterns involving fractures of the lamina or spinous processes may preclude rigid immobilization by simple wiring techniques. Plate fixation of the posterolateral masses has been advocated for such injuries. The purpose of this biomechanical study was to test the relative stiffness provided by different posterior fusion constructs, including lateral mass plating. All testing was performed on fresh, unembalmed cadaveric spines divided into two vertebral segment units. Muscular tissue was stripped from the specimens, but all discal and ligamentous structures were preserved. Four different posterior fixation constructs were tested. These included 1) Rogers interspinous wiring, 2) Halifax laminar clamps, 3) bilateral 1/3 tubular plates on the lateral masses, using unicortical screws, and 4) bilateral 1/3 tubular plates on the lateral masses, using bicortical screws. Stiffness measurements were taken in both flexion and extension on all specimens. Yield strength and fatigue strength of the spines were not measured. It was found that 1/3 tubular plates secured with bicortical screws to the lateral masses provided the highest mean stiffness. Less stiffness was found in spines stabilized by Halifax clamps, interspinous wiring, and plates secured with unicortical screws. There was, however, no statistically significant difference in stiffness provided by any of these four implants. It was concluded that there is no advantage in plate fixation over standard fusion constructs in augmenting the stiffness of posterior fixation of the cervical spine.
 ...
PMID:Posterior plating of the cervical spine. A biomechanical comparison of different posterior fusion techniques. 319 91

Most patients with symptomatic osteoarthritis of the proximal interphalangeal joint should be managed nonoperatively. When operative intervention becomes necessary, therapeutic options include joint fusion or flexible implant arthroplasty. Both relieve pain; however, an implant, while preserving mobility, is subject to fatigue and ultimate failure.
 ...
PMID:Osteoarthritis of the proximal interphalangeal joint. 365 72

A modified osteocutaneous digital fillet flap was used to reconstruct the thumb of a fifty-three year old male with a severe gunshot wound to the dominant hand. An arthrodesis in the central portion of the bone graft sustained a fatigue fracture that progressed to union without treatment. The one stage procedure avoided the immobilization of a distant pedicle flap, revisional surgery of a complex free flap, and donor site morbidity.
 ...
PMID:Osteocutaneous digital fillet flap. A technical modification. 399 10

This study is designed to analyse the behavior, in the sagittal plane, of a complete human dorso-lumbar rachis, made rigid by the posterior instrumentation used for the treatment of scoliosis, on subjects suffering from DMD (Duchenne Muscular Dystrophy). The object of this analysis is to demonstrate the reliability of early surgery made possible by new instrumentation. Close review of the literature shows that the currently used Harrington or Luque instrumentations lead to mechanical complications, especially rod breaking, at the thoraco-lumbar junction. 8 specimens were non-destructively tested in-vitro. Compression and flexion were applied. For each test, rachis movements with and then without instrumentation, and also rod restraints were noted. The results show a linear stiffness multiplied by 8.3 in flexion and 11.6 in extension. The maximum restraint recorded for physiological displacements is 77 MPa. This remains largely under the fatigue-breaking limit of the metal used (stainless steel hammer-hardened 316 L, Young's modulus = 200,000 MPa, Poisson's ratio = 0.21, endurance limit = 350 MPa at 5 x 10(6) cycles). The results of this study encourage us to continue and develop early surgery in children affected by myopathy, with fixation of the complete rachis, including a lumbo-sacral arthrodesis and a supple dorsal part of the mounting, in the sagittal plane.
 ...
PMID:In-vitro biomechanical study of a dorso-lumbo-sacral posterior supple instrumentation with variable section. 893 35

Arthrodesis of the lumbosacral spine, although satisfactory for a majority of patients, has long term sequelae in 30% of patients. This is particularly true for adjacent segment degeneration. Numerous attempts at providing a mobile motion segment have been made in the past. The current status of the development of dynamic intervertebral prosthesis, including biomechanical and clinical data have been presented. The relevant material properties of plastics, ceramics, and metal are presented with the conclusion that metals currently present with the greatest longevity without undue fatigue and wear as many as 100,000,000 cycles (40 years use) as an alternative to spinal fusion. An analysis of the kinematics of the motion segment have resulted, together with the material properties in the development of a dynamic intervertebral disc for use in the lumbar spine. The disc resembles a normal motion segment. In motion stiffness and center of rotation, wear debris development in 1/300 equivalent to that of a total hip prosthesis for the same given time. Safety features include immediate screw fixation to prevent displacement, a wedge elastic (spring) shape, and a bony porous ingrowth surface. The prosthesis is constructed of cobalt chromium and titanium with minimal corrosive properties on long term testing.
 ...
PMID:Intervertebral disc replacement. Experimental study. 913 73

Three methods of internal fixation for MCP arthrodesis of fifteen cadaveric thumbs were used to analyze the biomechanical stability by applying a palmar force, lateral force, and torsion moment. The techniques used included two K-wires 0.045 in parallel (BK), 2 cerclage metallic wires #25 perpendicular to each other (CP), and a 6-holes plate and screws construct from Synthes (PV). The initial rigidity was measured using a Bionix MTS-858. The results after statistical analysis showed: 1) CP was just as rigid as PV for the palmar and lateral tests; 2) CP was, overall, superior to BK in palmar and lateral tests; 3) no difference existed in torsion between the three types of fixation. A comparison was done between the rigidity of the fixation techniques used and the rates of bony nonunion found in the literature. The mean rates of nonunion were reported to be 0-4.0% for the following techniques: CP, tension band wiring (TB), plate and screws, external fixation, compression screw. The rates of nonunion were higher, 7.5-12.5%, for BK, cerclages not perpendicular (CM), bone pegs. According to the results of this biomechanical study and the review of the literature, fixation with BK is the least rigid, and fixation with CP is just as rigid as with PV. The success clinically of CP is yet to be demonstrated. Other studies on the properties of CP for fatigue would be necessary to give a better analysis.
 ...
PMID:[Biomechanical evaluation and clinical correlation of 3 methods of internal fixation of metacarpophalangeal arthrodesis of the thumb]. 984 22

The role of spinal instrumentation is to provide mechanical stability, obtain and maintain anatomic alignment, and promote fusion. The American Society for Testing and Materials (ASTM) introduced guidelines and procedures so that biomechanical properties of different implant designs could be compared in a consistent manner. Combined with biomechanical analyses, clinical evaluation allows the safety and efficacy of a spinal implant system to be determined before construction. The objective of our study was to determine the biomechanical properties and clinical performance of the OMEGA-21 Spinal Fixation System. Static and dynamic (fatigue) biomechanical testing was performed per ASTM guidelines and recommendations on individual components and on the system assembled in a corpectomy model. Clinical and radiographic evaluation of 57 consecutive patients with indications for instrumented spinal arthrodesis of the lower dorsal lumbar and sacral segments of the spine was performed at a mean follow-up of 31.9 months. Static and fatigue testing revealed superior biomechanical properties of the individual components and of the assembled system. The mechanical-strength values of the system were comparable with maximum reported values for existing implant designs. At final clinical follow-up, 86% of patients obtained relief of their symptoms; 84% considered their clinical results to be excellent or good. Ninety-one percent of patients satisfied radiographic criteria for bony fusion. There were 5 implant-related complications: 2 misplaced screws (2 patients), local pain above the implant (2 patients), and 2 broken expansive screws (1 patient). Biomechanical and clinical results indicate that the OMEGA-21 system is feasible and performs well as a spinal instrumentation system for the lower dorsal, lumbar, and sacral spine.
 ...
PMID:Biomechanical testing and clinical experience with the OMEGA-21 spinal fixation system. 1137 Sep 45

The sublaminar wiring procedure has been commonly used for stabilizing the atlantoaxial complex. Multistrand braided cables were introduced in the early 1990s. In previous biomechanical studies these cables were demonstrated to be superior to monofilament wires in terms of their flexibility, mechanical strength, and fatigue-related characteristics. To the authors' knowledge, they are the first to describe clinically the occurrence of delayed spinal cord compression resulting from multistrand cables after the completion of rigid spinal arthrodesis in the upper cervical spine. Three patients underwent posterior atlantoaxial fusion in which two sublaminar multistrand cables were placed. Between 15 and 48 months postoperatively, they suffered from upper- and lower-extremity numbness as well as gait disturbance. Plain radiography and computerized tomography myelography revealed spinal cord compression caused by the sublaminar cables, although fusion was complete and physiological alignment was maintained at the fused segment. The radiographs obtained immediately after surgery demonstrated that the initial cable placement had been properly performed. The shape of the cable at the initial surgery was oval and then gradually became circular. The anterior arc of the circular shape of the cable in fact led to the spinal cord compression. Considering the mechanism of this late complication, a cable tends to spring open because of its high flexibility and becomes circular shaped even after the complete arthrodesis. When applying multistrand cables for intersegmental fixation at the atlantoaxial complex, delayed complications related to bowing of the cables is possible.
 ...
PMID:Spinal cord compression by multistrand cables after solid posterior atlantoaxial fusion. Report of three cases. 1240 93


1 2 3 Next >>