Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Internal Fixators”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources
PubMed1997

Fiber-matrix interface studies on bioabsorbable composite materials for internal fixation of bone fractures. I. Raw material evaluation and measurement of fiber-matrix interfacial adhesion.

The objective of this study was to characterize and evaluate the performance of various fiber-matrix composite systems by studying the mechanical, thermal, and physical properties of the fiber and matrix components, and by studying the fiber-matrix interface adhesion strength using both microbond and fragmentation methods. The composites studies were poly(L-lactic acid) (PLLA) matrix reinforced with continuous fibers of either nonabsorbable AS4 carbon (C), absorbable calcium phosphate (CaP), poly(glycolic acid) (PGA), or chitin. Carbon and CaP single fibers had high Young's moduli and failed in a brittle manner. PGA and chitin single fibers had relatively lower Young's moduli and relatively higher ductility. Upon in vitro hydrolysis, CaP fibers retained 17% of their tensile strength and 39% of their Young's modulus after 12 h, PCA fibers retained 10% of their tensile strength and 52% of their Young's modulus after 16 days, and chitin fibers retained 87% of their tensile strength and 130% of their Young's modulus after 25 days. PLLA films had much lower strength and Young's moduli, but much higher ductility relative to the single fibers. Using the microbond method, the initial fiber-matrix interfacial shear strength (IFSS) of C/PLLA and CaP/PLLA microcomposites was 33.9 and 12.6 MPa, respectively. Upon in vitro hydrolysis, C/PLLA retained 49% of IFSS after 15 days and CaP/PLLA retained 46% of IFSS after 6 h. Using a fiber fragmentation method, the initial IFSS of C/PLLA, CaP/PLLA, and chitin/ PLLA was 22.2, 15.6, and 28.3 MPa, respectively. The performance of carbon fibers and C/PLLA composites was superior to the other fibers and fiber/PLLA systems, but the carbon fiber was nonabsorbable. CaP had the most suitable modulus of the absorbable fibers for fixing cortical bone fracture, but its rapid deterioration of mechanical properties and loss of IFSS limits its use. PGA and chitin fibers had suitable mechanical properties and their retention for fixing cancellous bone fractures, but likely had insufficient stiffness for applications such as bone plates for fixing cortical bone fractures.

Adhesiveness↗
PubMed1997

Fiber-matrix interface studies on bioabsorbable composite materials for internal fixation of bone fractures. II. A new method using laser scanning confocal microscopy.

In this study, a new visual characterization method was developed using laser scanning confocal microscopy (LSCM) to study morphologic properties, particularly at the fiber-matrix interface, by optical sectioning of bioabsorbable single-fiber composites. The interface gap width (IGW) between the fiber and matrix, and the changes in IGW after in vitro hydrolysis, named the gap rate (Rg), were measured from images obtained using the LSCM. Higher values for IGW and Rg showed faster degradation of the fiber-matrix interface. These parameters were used to investigate the effects of strain, wicking, different reinforcing fibers, and gamma-irradiation on the fiber-matrix interface morphology. The component materials used were nonbioabsorbable AS4 carbon (C) fibers, bioabsorbable calcium phosphate (CaP), poly(glycolic acid) (PGA), and chitin fibers, and bioabsorbable poly(L-lactic acid) (PLLA) matrix. The application of strain on CaP/PLLA composites increased the IGW up to about 15%, after which there was no change up to 25%. The Rg for CaP/PLLA composites with the fiber ends exposed in vitro (permitting wicking) was greater than for CaP/PLLA with the fiber ends embedded completely within the matrix (preventing wicking). Open-end C/PLLA composites had the slowest rate of interface degradation in vitro, followed by chitin/PLLA, PGA/PLLA, and CaP/PLLA. The exposure of closed-end CaP/PLLA composites to 4 Mrad of gamma-irradiation, in air at room temperature or in vaccuum at 77K, accelerated the rate of interface degradation in vitro. In conclusion, an effective new visual characterization method was developed using LSCM, and it was used to show that (a) moderate strain could accelerate the degradation of the interface, (b) fiber-matrix interface wicking could accelerate the rate of degradation of the interface, (c) the rate of interface degradation depends on the type of fiber used, and (d) gamma-irradiation could accelerate the rate of interface degradation. Furthermore, the results of LSCM analysis of different reinforcing fibers with a PLLA matrix agree with measurements of interfacial shear strength (IFSS) and single-fiber tensile strength reported in Part I of this study.

Chitin↗
PubMed1991

Ultra-high-strength absorbable self-reinforced polyglycolide (SR-PGA) composite rods for internal fixation of bone fractures: in vitro and in vivo study.

The ultra-high-strength, self-reinforced (SR) absorbable polymeric composites, consisting of reinforcement elements, like fibers, and of matrix polymer which have the same chemical element composition as reinforcement, were defined. A method to manufacture self-reinforced, absorbable polyglycolide (SR-PGA) rods of polyglycolide sutures (Dexon) by sintering them partially together at elevated temperature and pressure was presented. The rods with nominal diameters of 1.5 mm, 2.0 mm, 3.2 mm, and 4.5 mm showed initial bending modulus and strength values of 8-15 GPa and 220-405 MPa, respectively. Their initial shear strengths were 165-255 MPa. The smallest rods (diam. 1.5 mm) lost their mechanical strength after implantation in the subcutis of rabbits in 4-5 weeks while the thickest rods retained their strength over 8 weeks. The ultra-high-strength SR-PGA rods were concluded to be suitable for fixation of cancellous bone fractures, osteotomies, and epiphyseal plate fractures where the fixation is not exposed to excessive mechanical stresses and where the loads are predominantly of a shear nature.

Animals↗
PubMed1987

Torsion and bending analysis of internal fixation techniques for femoral neck fractures: the role of implant design and bone density.

To evaluate pin/screw/plate fixation for management of femoral neck fractures, 39 proximal femora were tested in both torsion and flexion under physiological loading conditions. Three, four, or five implants of six commonly used multiple-fixation devices, and a sliding hip screw with and without an additional 6.5-mm cancellous screw were examined in paired femora. The intact and postfixation femora were initially subjected to a single applied moment, and the torsion and bending stiffness were determined from the load-deformation data. Postfixation femora were also subjected to cyclic loading in flexion at three load ranges, and fixation was judged successful if no failure occurred on or before 1,500 cycles of 667 to 2,000 N of a combined compressive force and moment. Anterior-posterior and lateral radiographs of each specimen were taken after fixation in order to evaluate Singh's index of bone density, fracture reduction, implant placement, and cross-sectional diameter of the femoral neck. Bone density was also evaluated by computed tomography (CT) and physical measurement of core samples obtained from the femoral head. The results indicate that there appears to be no justification for the use of more than three pin/screw implants for management of femoral neck fractures. Bone density was found to correlate with fracture stability and may be a useful predictor of fixation success.

Aged↗
PubMed1991

Anterior and posterior internal fixation of vertical shear fractures of the pelvis.

A laboratory study was undertaken to evaluate the effectiveness of alternative methods of fixation of unilateral vertical shear fractures of the pelvis. Prior to experimental testing, a biomechanical analysis was performed to estimate the forces that displace the hemipelvis in the presence of two different patterns of injury: an interforaminal sacral fracture and a disruption of the sacroiliac joint. These lesions were then experimentally created in five unembalmed human pelvises and sequentially fixed with an external Hoffmann frame alone, a Hoffmann frame with sacral bars, or sacral bars with either one or two bone plates placed across the symphysis pubis. Each pelvis/fixator system was mechanically tested by loading along the direction of the resultant muscle force predicted by the biomechanical analysis. During loading the proximal migration of the ilium was continuously recorded with a transducer. At intervals during loading, the three-dimensional displacement of the detached hemipelvis at the pubic symphysis was also measured using a stereophotographic technique. With both the sacral fracture and the sacroiliac disruption, the addition of posterior sacral rods substantially increased the strength and rigidity of fixation provided by the Hoffmann fixation frame alone (p less than 0.01). In specimens with a sacral fracture, the use of anterior plates with posterior rods restored 65-71% of the strength of the intact pelvis, in comparison with 46% observed with the combination of sacral rods with an anterior Hoffmann frame (p less than 0.01). All of the methods of fixation evaluated in this study were less successful in stabilizing the sacroiliac disruption.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗
PubMed1982

The use of the "Bousquet" internal fixation device for trochanteric fractures. Report on 120 patients.

Two-hundred fractures of the upper femur were treated with the Bousquet nail-plate system between July 1977 and June 1981. One-hundred and twenty of these patients--37 males and 83 females, aged 26-96 years, constitute the material of the present study. Ninety-eight fractures were trochanteric, nineteen sub-trochanteric, and three of the basal type. The follow-up time ranged from two to four years. The Bousquet nail and plate was found adequately to fulfil the mechanical needs of fractures of the trochanteric region. The operation is simple, safe and fast, and an appropriate angle between the nail and the plate can be easily selected. All fractures satisfactorily united in good position and no pseudarthrosis was observed. Mortality and rate of complications was comparatively low.

Adult↗
PubMed1993

Subcapital fracture of the hip after internal fixation of an intertrochanteric fracture. A case report.

We report a case of a subcapital fracture that occurred after reduction and fixation of an intertrochanteric fracture of the hip with a sliding screw. The subcapital fracture occurred 4 months after surgery for the intertrochanteric hip fracture. The subcapital fracture was undisplaced and occurred in an area supported by the screw without damaging the implant. This patient was treated conservatively with bedrest.

Aged↗
PubMed1998

Dislocated fractures of the talus treated with biodegradable internal fixation.

Six patients with a displaced fracture of the neck or body of the talus were treated using biodegradable screws and rods. During an average follow-up time of 24 (range, 18-31) months, there were no redisplacements nor collapses due to avascular necrosis. All the fractures united. The functional result was mainly dependent on the presence or absence of other injuries, being excellent in 4, good in 1 and poor in 1 patient who also had bilateral highly comminuted calcaneal fractures. Thus, biodegradable implants seem to be suitable for the fixation of displaced fractures of the talus.

Adult↗