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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↗
PubMed2003

Long-term study of high-strength hydroxyapatite/poly(L-lactide) composite rods for the internal fixation of bone fractures: a 2-4-year follow-up study in rabbits.

Biodegradation of hydroxyapatite (HA)/poly(L-lactide)(PLLA) composite bone implant rods was studied with the use of two types of HA particles as reinforcing fillers: uncalcined HA (u-HA) or calcined HA (c-HA). Composite rods of u-HA/PLLA and c-HA/PLLA containing 30 or 40% (w/w) HA were implanted in the distal femur of 21 rabbits, and specimens were examined by light microscopy, scanning-electron microscopy (SEM), and transmission-electron microscopy (TEM) 2-4 years later. For u-HA/PLLA, trabecular bone bonding directly onto the rod was maintained for up to 2 years. By 3 years, surface collapse had begun, and the implants were shrinking. By 4 years, they had shrunk further, with complete bone encapsulation. The u-HA particles were small and needle shaped in the peripheries, and TEM confirmed their resorption. The cross-sectional area after 4 years decreased by 23.3+/-8.4%. The mean ratio of bony ingrowth to the initial cross-sectional area around the shrunken rods was 6.7+/-1.3 %. The viscosity molecular weight of PLLA reduced from 2 x 10(5) to less than 1 x 10(3). Thus, most of the PLLA had released from the rods. The c-HA/PLLA implants also showed good osteoconductivity, but shrinkage and infiltration of histiocytes were less. No osteolytic or osteoarthritic changes were found.

Absorbable Implants↗
PubMed2000

[Arthroscopically controlled minimal invasive screw fixation of scaphoid fractures. A pilot study].

We could not find any systematic studies about the value of arthroscopy in scaphoid fractures in the literature, and therefore undertook a pilot study of 20 scaphoid fractures which were treated arthroscopically by the Herbert-Whipple screw and were minimally invasive. We found very good radiological and clinical results in 17 patients and good results in 3 patients evaluated by the Wozasek and Moser score. For reduction of dislocated fractures we used distraction with 5 kg in the wine waiters position. In four cases we used additional K wires as joysticks. Arthroscopy is less valuable in reduction, however, it is important in verification of the compression force of the Herbert-Whipple screw and for diagnosis and therapy of lesions of the scapholunate ligament and TFC complex. We found seven SL instabilities, two lesions of the meniscus, and one Palmer 1B lesion of the TFC complex. From these results we conclude that arthroscopy should necessarily be done by minimally invasive osteosynthesis of scaphoid fractures to detect and treat discoligamentous injuries of the wrist.

Adult↗
PubMed2006

Comparison of accuracy of lag screw placement in cephalocondylic nails and sliding hip screw plate fixation for extracapsular fractures of the neck of femur.

This study compared the accuracy of lag screw placement between extracapsular femoral fractures fixed with sliding hip screw plate systems and those fixed with cephalocondylic nails. It involved 75 retrospective radiographs of fractures fixed with either a cephalocondylic nail (32) or a sliding hip screw plate system (43). Postoperative anteroposterior and lateral radiographs of the hip were scanned using a digital X-ray scanner and measured using computer software. Measurements were conducted by two independent observers, and the radiographs were calibrated to correct for magnification. Accuracy of lag screw placement was determined by "tip apex distance," described by Baumgaertner et al., and by the ratio method described by Parker. The mean tip apex distance was 24.0 mm in sliding hip screw plate systems and 21.1 mm in cephalocondylic nails. This was found to be statistically significant. Lag screw placement through cephalocondylic nails is more accurate and therefore has less chance of cut-out compared with sliding hip screw plate systems. There was no statistically significant difference using Parker's ratio method because this method quantifies the direction of the screw rather than the depth of penetration.

Bone Nails↗
PubMed1988

Screw fixation of odontoid fractures: preliminary report.

In the period from 1981 to 1985, 32 odontoid fractures were treated in the National Institute of Traumatology. In four cases anterior stabilization was provided with compression screws inserted from the front. Two cases of odontoid fracture are shown, one accompanied by ventral, the other by dorsal dislocation. A brief review is provided of the results obtained with different methods of treatment drawing on the international literature.

Adult↗
PubMed2005

A 5-7 year in vivo study of high-strength hydroxyapatite/poly(L-lactide) composite rods for the internal fixation of bone fractures.

The biocompatibility and biodegradation of hydroxyapatite (HA)/poly(L-lactide) (PLLA) composite bone implant rods were studied using two types of HA particles as reinforcing fillers, uncalcined-HA (u-HA) or calcined-HA (c-HA). Composite rods of u-HA/PLLA and c-HA/PLLA were implanted into the distal femurs of 25 rabbits. Four of these rabbits lived for more than 5 years after implantation, with one living for 7 years 4 months. Samples were retrieved after the rabbits died naturally and specimens were examined by light microscopy and scanning electron microscopy (SEM). For u-HA/PLLA, the shrinkage of the rods progressed further after 4 years, and some were almost completely resorbed. We could not find traces of the rod in some sections from more than 6 years. Remodeled bone encircled the residual material, and trabecular bone bonded directly to the rod was found toward the center. For u-HA/PLLA 30%, results were similar to u-HA/PLLA 40%, and the cross-sectional area had decreased by 4.0% at over 7 years. Most of the PLLA had been released from the rods. Neither obvious osteolytic nor osteoarthritic changes were found after 4 years.

Animals↗
PubMed2003

Fixation of femoral fractures in multiple-injury patients with combined chest and head injuries.

BACKGROUND: The purpose of the present paper was to study the effects of a femoral shaft fracture and its early stabilization on the morbidity, mortality, and outcome of multiple-injury patients with combined blunt head and chest trauma. The clinical course of patients was analysed using a prospectively gathered data base. METHODS: Out of 352 multitrauma patients, from September 1992 to June 2000, we identified 28 patients with combined blunt chest and head trauma (abbreviated injury scale >/= 2) and a femoral fracture as the study group. A total of 120 patients with combined chest and head trauma but without femoral fracture formed the control group. Parameters examined included injury severity, injury pattern, haemodynamics at admission, mortality, duration of ventilation, length of stay in intensive care unit, and outcome. RESULTS: There were no significant differences regarding the demographics and injury severity (injury severity score) between the two groups. No significant differences were found in terms of mortality, duration of ventilation\intensive care unit stay and outcome. Injury severity (P < 0.0001), age (P = 0.0153), and haemodynamics at admission (P = 0.0036) were shown to have a significant effect on mortality and outcome. Injury severity (P < 0.0001) and age (P = 0.017) had a significant effect on the duration of ventilation\intensive care unit stay. CONCLUSIONS: The present study suggests that a femoral shaft fracture and its early stabilization in a multitrauma patient with combined chest and head injury do not adversely affect mortality and outcome and supports aggressive surgical management for these patients.

Adolescent↗
PubMed1987

A method for fixation of femoral fractures below previous hip implants.

Previously applied plates and screws or endoprosthetic implants of the proximal femur create a recurrent problem in surgery for fractures below such implants. Of 13 elderly women (mean age, 81 years) six had had a hip arthroplasty, five a nail and plate, and two a nail or a plate only. The fresh fractures were stabilized from the condylar region by intramedullary nails connected to a coupling-piece with two transverse screws preventing extrusion or intrusion of the nails. All fractures healed uneventfully without rotatory and angulatory malalignment. The maximum shortening was 2 cm in two patients and was less in the others. Patients walking before surgery were mobilized the day after. The system is more stable than Rush pins or Ender nails only and does not require good quality of bone needed for plating.

Aged↗