Breaking strength retention and histologic effects around 1.3-mm. ORTHOSORB polydioxanone absorbable pins at various sites in the rabbit

Absorbable 1.3-mm polydioxanone (ORTHOSORB) pins were implanted in 75 New Zealand White rabbits in three sites: within the lateral subcutaneous tissue parallel to the femur, down the femoral intramedullary canal, and mediolaterally across the femoral condyles (transcondylar). Pins were harvested at periodic intervals up to 56 and 365 days for mechanical and histologic analyses, respectively. Mechanical analyses were performed by loading the pin in double shear. Histologic analyses were performed on the pin and surrounding tissue. Histologic observations revealed a typical nonspecific foreign-body reaction at all implant sites that resolved at 1 year after resorption of the pin. On histologic examination, there was complete resorption of the pin material in the subcutaneous site by day 182, and there was complete resolution of all response to the pin in six of nine rabbits by day 365. In the intramedullary site, pin material was completely resorbed, based on histologic examination, in five of six rabbits by day 182, and there was complete resolution of the response to the pin in eight of nine rabbits by day 365. The pin material was completely resorbed based on histologic examination of the transcondylar site by day 210, and there was complete resolution of the response to the pin in four of six rabbits by day 270 and in four of nine rabbits by day 365. No enlarged pin tracks or sinus formations were observed in or near the implants sites. The average initial shear strength as 171.4+/ 5.1 MPa, and the breaking strength retention decreased with increasing implantation time. Pins from the subcutaneous regions maintained above 97% of their initial strengths at 28 days, and those from the intramedullary canals maintained above 92%. At later times the strength of the pins implanted in the intramedullary canal decreased more rapidly than those from the subcutaneous region. Overall, the average breaking strength of the subcutaneous pins was significantly greater than that of the intramedullary pins at all time points beyond 14 days. These data indicate that the pins exhibited a strength retention profile sufficient to allow normal healing of bone without enlarged pin tracts, allergic reactions, or sinus formations.     

Complications after treatment of patients with osteogenesis imperfecta with a Bailey-Dubow rod

The purpose of this study was to analyse the complications using the Bailey-Dubow expanding intramedullary rods in patients with osteogenesis imperfecta. Between 1985 and 1996 intramedullary rodding of 107 long bones with expanding Bailey-Dubow rods was performed in 29 patients suffering from osteogenesis imperfecta. Indications for using rods included osseous deformities and bone deformities in combination with fractures. The average follow-up was 3.5 years (range 2 months to 9 years). The total complication rate in these patients was 63.5% (68 rods). The main complication was rod migration often combined with perforation of joint, bone and soft tissue. Additionally, there was a high incidence of new fractures as well as refractures. Other complications like infections, pseudarthrosis, lack of elongation or over-elongation of the rods, and loosening of the T-piece were only rarely seen. Based on our experience and the information available in the literature, the Bailey-Dubow rod is currently the most successful way to stabilize the growing long bones of patients suffering from osteogenesis imperfecta. However, when using this device, the surgeon as well as the parents of the patient must be aware of the high incidence of complications.     

Preservation of alveolar bone in extraction sockets using bioabsorbable membranes

The purpose of this study was to evaluate the clinical effectiveness of a bioabsorbable membrane made of glycolide and lactide polymers in preserving alveolar ridges following tooth extraction using a surgical technique based on the principles of guided bone regeneration. Sixteen patients requiring extractions of 2 anterior teeth or bicuspids participated in the study (split-mouth design). Following elevation of buccal and lingual full-thickness flaps and extraction of teeth, experimental sites were covered with bioabsorbable membranes; control sites did not receive any membrane. Titanium pins served as fixed reference points for measurements. Flaps were advanced in order to achieve primary closure of the surgical wound. No membrane became exposed in the course of healing. Reentry surgeries were performed at 6 months. Results showed that experimental sites presented with significantly less loss of alveolar bone height, more internal socket bone fill, and less horizontal resorption of the alveolar bone ridge. This study suggests that treatment of extraction sockets with membranes made of glycolide and lactide polymers is valuable in preserving alveolar bone in extraction sockets and preventing alveolar ridge defects.     

Intramedullary pressure and pulmonary function during total knee arthroplasty

Twenty-eight patients who underwent unilateral total knee arthroplasty and 20 patients who underwent simultaneous bilateral total knee arthroplasties participated in this study and were randomized to have either a fluted or round 10-mm diameter femoral intramedullary alignment rod used during surgery. The intramedullary rods were cannulated and connected with pressure tubing to a monitor which provided measurements of pressure at the tip of each rod. Arterial blood gas measurements on room air were obtained before and on the morning after surgery. An arterial line was placed and an arterial blood gas measurement was obtained at the time of skin incision and again after tourniquet release. Pulmonary shunt was calculated from the arterial blood gas measurements. Intramedullary pressure during rod insertion was significantly higher for the groups of patients having the round compared with the fluted rod. The change in pulmonary shunt during surgery was lowest for the patients in the unilateral group having the fluted rod and highest for the patients in the bilateral group having the round rod. A fluted rather than a round intramedullary alignment rod should be used to minimize intramedullary pressure and pulmonary shunting during unilateral and bilateral total knee arthroplasties.     

Fixation with bioabsorbable pins in chevron bunionectomy

Fixation with bioabsorbable pins in distal chevron bunionectomy reduces the inconvenience and the risk of infection associated with fixation with stainless-steel Kirschner wires, which leaves a portion of the wires protruding from the skin. However, use of bioabsorbable implants has been reported to be associated with osteolysis and formation of a sinus with a sterile discharge. We studied the outcome and complications seen with use of poly-p-dioxanone pins and those seen with use of stainless-steel Kirschner wires after chevron bunionectomy in 114 patients (144 feet). We found no difference between the treatment groups with regard to the prevalence of complications or the stability of fixation. Notably, the prevalence of osteolysis was quite similar between the treatment groups; none of the feet that had had fixation with bioabsorbable pins had formation of a sinus with a sterile discharge. We believe that bioabsorbable pins can be used reliably to fix the site of the osteotomy for a distal chevron bunionectomy without undue risk of osteolysis or other complications.     

Long-term results of intramedullary pinning of forearm fractures in a developing country

BACKGROUND: Patients with fractured forearms who were treated with intramedullary Rush pins/nails at Port Moresby General Hospital (Papua New Guinea) were studied. METHODS: Sixteen patients were reviewed 24 months after insertion of the pins/nails. RESULTS: The results indicate that good outcomes could be achieved by the use of intramedullary pins in developing countries. There were no major specific short- or long-term complications (re-fracture or non-union). Disability in terms of pain and stiffness was noted in only three out of six patients with pins in situ. These were considered temporary disabilities. CONCLUSIONS: The pins are much cheaper than plates and screws, require minimal expertise for insertion, and removal was performed under local anesthetic as outpatient cases. They remain a valuable method for managing patients with forearm fractures in developing countries.     

Comminuted supracondylar humeral fractures repaired with a modified type I external skeletal fixator construct

Highly comminuted supracondylar humeral fractures were stabilised in six large-breed dogs with a modified type I external fixator using a craniomedial acrylic connecting column and an intramedullary pin which was incorporated into the connecting frame. This construct provided sufficient stability to allow satisfactory bone healing in five of the six dogs, while premature removal of the intramedullary pin and external fixator resulted in subsequent refracture of the humerus in the remaining dog. Limb function at the time of final assessment was considered excellent in two dogs, good in three dogs and poor in one dog. The craniomedial acrylic connecting column simplified application of this modified type I(a) configuration to the humerus by reducing the number of clamps required; the acrylic column also facilitated contouring of the craniomedial connecting column to the brachium and was readily extended proximally to engage the intramedullary pin. In addition, the acrylic connecting column allowed placement of intramedullary pins of varying diameter.     

Effects of bioabsorbable and non-resorbable barrier membranes on bone augmentation in rabbit calvaria

The aim of this study was to compare the effects of bioabsorbable and non-resorbable membranes on experimental guided bone augmentation in 8 Japanese white rabbits. A cutaneous flap was demarcated and raised from the forehead of each animal, the periosteum was lifted, and the calvarial bone on both sides of the midline was exposed. A titanium screw was inserted into the bone on each side of the midline and one screw was covered with a bioabsorbable (polylactic acid) membrane and the other with a non-resorbable (expanded polytetrafluoroethylene) membrane. The implanted screws and membranes were then covered with the periosteum and cutaneous flap. After healing for 6 months, the animals were euthanized and the experimental area was prepared for histological investigation. New bone had formed under both membranes with no sign of infection or membrane exposure. The amount of newly generated bone (89.0 +/- 17.3% versus 54.7 +/- 14.0%, P <0.05) and the percentage of newly generated bone height (81.5 +/- 6.3% versus 58.9 +/- 7.8%, P <0.05) in the space beneath the non-resorbable membrane was greater than that beneath the bioabsorbable membrane. However, there were no statistically significant differences between the bioabsorbable and non-resorbable membranes with respect to the percentage areas of mineralized bone (52.3 +/- 11.3% versus 47.1 +/- 6.7%, P = 0.8658) and bone marrow (47.7 +/- 11.3% versus 52.9 +/- 6.7%, P = 0.4838) and bone contact with the screw (88.3 +/- 6.9% versus 89.2 +/- 7.3%, P = 0.9999). In conclusion, at least within the limitations of this rabbit model, we suggest that non-resorbable membranes with sufficient stiffness should be used to obtain greater bone volume and height instead of bioabsorbable membranes for the GBR procedure, and that this will facilitate predictable bone augmentation in spaces beyond the bone surface. Therefore, the bioabsorbable membrane could not replace the non-resorbable membrane used in this model.     

Haptically perceiving the distances reachable with hand-held objects.

Nine experiments are reported on the ability of people to perceive the distances reachable with hand-held rods that they could wield by movements about the wrist but not see. An observed linear relation between perceived and actual reaching distances with the rods held at one end was found to be unaffected by the density of the rods, the direction relative to the body in which they were wielded, and the frequency at which they were wielded. Manipulating (a) the position of an attached weight on an otherwise uniformly dense rod and (b) where a rod was grasped revealed that perceived reaching distance was governed by the principle movement(s) of inertia (I) of the hand-rod system about the axis of rotation. This dependency on moment of inertia (I) was found to hold even when the reaching distance was limited to the length of rod extending beyond an intermediate grasp. An account is given of the haptic subsystem (hand–muscles–joints–nerves) as a smart perceptual instrument in the Runeson (1977) sense, characterizable by an operator equation in which one operator functionally diagonalizes the inertia and strain tensors. Attunement to the invariants of the inertia tensor over major physical transformations may be the defining property of the haptic subsystem. This property is discussed from the Gibsonian (ecological) perspectives of information as invariants over transformations and of intentions as extraordinary constraints on natural law. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acoustic Emission Characterization of Damage in Hybrid Fiber-Reinforced Polymer Rods

The development and testing of a pseudoductile hybrid fiber-reinforced polymer rod consisting of glass and carbon fibers is described. Two different hybrid forms were considered for the development of the hybrid rods, including (1) random dispersion of the glass and carbon fibers; and (2) a core-shell design with a glass fiber core protected by the carbon fiber shells. The mechanical properties of the hybrids were evaluated through uniaxial tension tests. The hybrid rods developed by way of the core-shell approach exhibited pseudoductile properties that included a yield point of 1,153 MPa and an ultimate strength of 1,191 MPa, with a strain of 3.5% at ultimate. The experimental program also included damage assessment by way of a single-channel fiber optic acoustic emission (AE) sensor. The acoustic emission technique was employed for real-time determination of the progressive damage due to rupture of fibers. Moreover, the spectral energies of the frequency spectrum from the AE signals were employed for assessment of the state of damage in the rods. The spectral energies distinguish between the carbon and glass fiber ruptures. This differentiation of signals provides information about the condition and the state of health of the hybrid rod.     

Identification and distribution of photoreceptor subtypes in the neotenic tiger salamander retina

The neotenic tiger salamander retina is a major model system for the study of retinal physiology and circuitry, yet there are unresolved issues regarding the organization of the photoreceptors and the photoreceptor mosaic. The rod and cone subtypes in the salamander retina were identified using a combination of morphological and immunocytochemical markers for specific rod and cone opsin epitopes. Because the visual pigment mechanisms present in the tiger salamander retina are well characterized and the antibodies employed in these studies are specific for particular rod and cone opsin epitopes, we also were able to identify the spectral class of the various rod and cone subtypes. Two classes of rods corresponding to the "red" and "green" rods previously reported in amphibian retinas were identified. In serial semithin section analyses, rods and cones comprised 62.4+/-1.4% and 37.6+/-1.4% of all photoreceptors, respectively. One rod type comprising 98.0+/-0.7% of all rods showed the immunological and morphological characteristics of "red" rods, which are maximally sensitive to middle wavelengths. The second rod subtype comprised 2.0+/-0.7% of all rods and possessed the immunological and morphological characteristics of "green" rods, which are maximally sensitive to short wavelengths. By morphology four cone types were identified, showing three distinct immunological signatures. Most cones (84.8+/-1.5% of all cones), including most large single cones, the accessory and principal members of the double cone, and some small single cones, showed immunolabeling by antisera that recognize long wavelength-sensitive cone opsins. A subpopulation of small single cones (8.4+/-1.7% of all cones) showed immunolabeling for short wavelength-sensitive cone opsin. A separate subpopulation of single cones which included both large and small types (6.8+/-1.4% of all cones) was identified as the UV-Cone population and showed immunolabeling by antibodies that recognize rod opsin epitopes. Analysis of flatmounted retinas yielded similar results. All photoreceptor types appeared to be distributed in all retinal regions. There was no obvious crystalline organization of the various photoreceptor subtypes in the photoreceptor mosaic.     

Different acute effects of single-axis and multi-axis hand-arm vibration

The present study was designed to comparatively evaluate the bone-pin interface in a long-term unloaded experimental study in two groups of pins, uncoated and coated with hydroxyapatite. Forty pins made of stainless steel were used. Half of the pins were plasma-sprayed with hydroxyapatite, and the other half remained uncoated. Four adult sheep were selected. Each sheep tibia was implanted with five pins. Two sheep were euthanized 4 months after surgery and the remaining two 12 months after surgery. Extraction torque was higher in the hydroxyapatite-coated pins compared with the uncoated ones at both 4 (p < or = 0.0005) and 12 months (p < or = 0.0005) after implantation. The histological patterns observed in the sheep euthanized 4 and 12 months after implantation were very similar. An extensive bony coverage of the hydroxyapatite-coated pins without any coating resorption and delamination from the metallic substrate was observed. Fibrous tissue encapsulation was found in the uncoated pins. These results demonstrate that the hydroxyapatite coating significantly improved the bone-pin interface. A similar improvement of bone-pin interface rigidity in many clinical situations is likewise possible.     

Compartment pressure monitoring during intramedullary fixation of tibial fractures

Twenty-six legs in 25 patients were monitored prospectively for compartment pressures during intramedullary nailing of open and closed tibial shaft fractures. Twenty-three patients were treated within 24 hours of admission. Twenty-three unreamed and three reamed intramedullary rods were utilized. Compartment pressures were measured initially, following fracture reduction, and during reaming. Pressures were also measured at the completion of nailing with the ankle dorsiflexed and at rest (plantar flexed) to determine positional effects on compartment pressures. Nine fractures (35%) were found to have persistently elevated pressures (> 40 mm Hg) and underwent immediate four-compartment fasciotomy. The remaining group of 17 fractures (65%) was monitored throughout the intraoperative period. No patient monitored intraoperatively developed postoperative compartment syndrome.     

Structures,faults, and the rod-plate transition in eutectics

The microstructures of several eutectic alloys were examined by scanning electron microscopy. Eutectic alloys of Ni-W, NiAl-Cr, NiAl-Cr (Mo) were directionally solidified and selectively etched to reveal the microstructure in three dimensions. A variety of rod and plate structures was observed that illustrates the rod-plate transition. In a nonfaceted rod eutectic, a fault structure consisting of branched rods and rod terminations was observed, while in a faceted alloy faults consisted of a web connecting two faceted rods. During solidification, the web structure splits into two faceted rods producing a plate to rod transition. The formation of a web between two rods causes the transition from rods to plate. In Ni-W, the rod structure transformed to plates in grains where the growth direction deviated from being parallel to the facet planes. It was concluded that alignment is a principle factor in the rod plate transition.     

Health hazard amongst chrome industry workers with special reference to nasal septum perforation

Nine years' experience with a combined intramedullary rod and triflanged nail in eighty-four non-pathological fractures in the subtrochanteric region of the femur is reported and a system of classifying these fractures based on morphology is offered. The appliance was successful in permitting early mobilization of patients and afforded a high rate of union of the fractures. The problems of varus displacement of the distal fragment and protrusion of the device into the joint were not encountered, and there was only one mechanical failure.     

Bond to Concrete of FRP Rebars after Cyclic Loading

The bond mechanism of fiber-reinforced polymer (FRP) rebars to concrete was studied to evaluate the effect of cyclic loading. Five different types of 12.0- and 12.7-mm rebars were tested. The FRP rods were embedded in concrete blocks and were subjected to up to 450,000 cycles at service stress level. The loading was accompanied by immersion in water at 60 and 20°C to accelerate deterioration effects. Pullout behavior of the rods was determined at the end of the loading period. The results indicated a reduction in the bond strength after loading. Three mechanisms of failure were identified: (1) Abrasion of the surface of the rod, which, in the case of uniform resin throughout the rod, may lead to a reduction of 20–30% in the bond strength; (2) delamination of the outer layer of the resin at the surface of the rod, which may lead to a reduction of up to 60% in the bond strength; and (3) abrasion of cement particles entrapped between the rod and the concrete, which serves as the main source of “bond” for smooth rods leading to approximately 70% of reduction in the bond strength. There was no significant change in the effect of curing temperature on the loss of bond.     

Fixation of osteotomies using bioabsorbable screws in the canine femur

The purpose of this study was to compare the healing properties of femoral osteotomies fixed by bioabsorbable screws (20:80 polyglycolic copolylactic acid copolymer) to standard stainless steel screws of a similar design in a dog femoral model. Two osteotomies were used, the trephine osteotomy (10 mm diameter) in the metaphyseal lateral femoral condyle and in the femoral diaphysis, and a unilateral osteotomy in the lateral femoral condyle. Two months after the trephine osteotomies, the femurs that contained the polymer screws were not significantly different in mechanical strength from the femurs treated with the stainless steel screws, either in the diaphyseal or metaphyseal model. There was no histological difference in bone healing between the metallic and polymer screws for all periods (2, 9, and 17 months). There was no adverse inflammatory response to the polymeric or metallic screws. By month 17, the polymer screws were resorbed completely. All the diaphyseal screw tracks had healed with bone and areas of remodeling were evident in two specimens. For the femoral condyle osteotomy model at 2 months, the polymer screws were present and intact, and all osteotomies healed with no evidence of inflammation. By 9 months, only one specimen had polymeric material left in the screw track. At 15 months, the screw tracks still were present but no evidence of any polymer remained. The tracks were filled with fibrous and adipose connective tissue. All osteotomies stabilized with either bioabsorbable polymer screws or stainless steel screws did heal satisfactorily without any complications, inflammation, or osteolysis. The polyglycolic polylactic acid copolymer may have a clinical role as a bioabsorbable material without the concerns for the osteolysis, foreign body reaction, and sterile abscess formation that have occurred with bioabsorbable fixation methods in the past.     

小直径不锈钢棒样品的火花源原子发射光谱分析

采用自制特制模具制取样品后,把待测样品放入仪器自带的小样品夹具中进行分析,实现了火花源原子发射光谱法对小直径不锈钢棒状样品中碳、硅、锰、磷、硫、铬、镍、钼、铜等元素含量的准确测定。由于目前尚无各种小直径光谱分析标准样品,因此实验从送检的直径6和8 mm钢棒中选择表面质量好,经光谱分析检验均匀性良好的棒材,经化学分析定值作为光谱分析的内部控制样品,试验表明应用“控样系数法”修正用块状光谱标样绘制的校准曲线的标准化数据,用以分析棒状样品可消除分析的系统偏差而提高分析的准确度,从而解决了棒状光谱标样绘制校准曲线的困难。对直径6和8 mm的不锈钢棒进行精密度考察,结果的相对标准偏差分别在0.51%~2.5%和0.10%~6.3%范围内。对4个小直径不锈钢棒样品进行分析,结果同湿法的测定结果基本一致,且测量误差小于国标GB/T222-2006的标准要求。     

Effect of resistance exercise training on bone formation and resorption in young male subjects assessed by biomarkers of bone metabolism

We studied the effects of high intensity resistance exercise training on bone metabolism in 17 young adult Oriental males (23-31 years) by measuring sensitive biomarkers of bone formation and resorption. The subjects were assigned to a training group and a sedentary group. The training group followed a weight training program three times per week for 4 months. In the training group, serum osteocalcin concentration and serum bone-specific alkaline phosphatase activity were significantly increased within the first month after the beginning of resistance exercise training, and the elevated levels remained throughout the training period, while there was no significant change in plasma procollagen type-I C-terminal concentration. Urinary deoxypyridinoline excretion was transiently suppressed and returned to the initial value but was never stimulated during the 4 months. These results suggest that the resistance exercise training enhanced bone formation without prior bone resorption. In the sedentary group, there was no significant difference in bone metabolic markers except plasma procollagen type-I C-terminal, which continuously decreased during the experimental period. There were no significant changes in total and regional bone mineral density in either group. In conclusion, (1) resistance exercise training increased markers of bone formation, while it transiently suppressed a marker of bone resorption, and (2) such adaptive changes of bone metabolism to resistance exercise training occurred during the early period of the training, before changes in bone density were observable through densitometry.     

Microsurgical treatment of intramedullary spinal cord tumors

Eighty patients with intramedullary spinal cord tumors were treated by microsurgical methods between 1988 and 1996. Twenty-nine patients were diagnosed with astrocytoma, 36 with ependymoma, five with metastasis, four with lipoma, three with dermoid or epidermoid tumor, two with neurofibroma, and one with neuroma. Vascular and infectious lesions (such as abscesses and hemangioblastomas) were excluded. After laminectomy, total removal of the lesion was achieved in 68 of 80 patients and subtotal removal in 12. Postoperative radiation therapy was performed in 13 of 80 patients. The follow-up period ranged from 12 to 92 months (mean 42.2 months). All patients underwent preoperative and postoperative magnetic resonance imaging at intervals ranging from 3 months to 5 years postoperatively. Four patients showed clinical and radiological evidence of local tumor recurrence during the follow-up period. Four patients died 5 months to 15 months postoperatively from the re-expansion of their primary metastatic disease. The operative results at long term (after the 6th postoperative month) were better than the results at short term (before the 6th postoperative month) and revealed clinical improvement in 63, no change in 10, and deterioration in seven patients. We recommend early radical surgery, whenever possible, to be performed when the patient's neurological status is still good. Subtotal removal and irradiation are better for malignant or metastatic tumors. Partial decompressive removal is best for large intramedullary lipomas. Plastic laminotomy with preservation of the intervertebral joints is especially recommended in young or middle-aged patients.