Intrinsic Radiosensitivity and PLD Repair in Osteosarcoma Cell Lines

The response to radiation of seven osteosarcoma cell lines was analysed by in vitro colony-forming assay and compared with that of eight human fibroblast strains. The values of D0, the surviving fraction after 2 Gy (S2Gy), and the mean inactivation dose (D) of osteosarcoma cells in log-phase culture were significantly higher than those of fibroblast strains (p less than 0.01). PLD (potentially lethal damage) repair of osteosarcoma cells evaluated in the plateau phase of growth showed great variation for enhancement of survival, although all of the values were maximized within 12 h after irradiation. In the osteosarcoma, intrinsic radiosensitivity in vitro reflected the clinical response to radiation. However, the capacity for PLD repair might not be a good indicator for predicting the results of radiation therapy.

Synthesis and chirality analysis of carbocyclic 5'-nor nucleosides

Achiral carbocyclic "DL-like" 5'-nor nucleosides have been synthesized and analyzed by the chiral capillary electrophoresis to elucidate the "D-like" monomers.

Structure and properties of carbocyclic 5'-nor oligodeoxynucleotides

The hybridization properties of carbocyclic 5'-nor oligodeoxynucleotides 1, 2 (24 mer, B = A) with DNA and RNA were investigated by CD melting curves. These oligomers formed unstable duplexes with DNA, but formed stable duplexes with RNA selectively.

Kashin-Beck disease: a historical overview

In 1919, the first report on Kashin-Beck disease (KBD) made by a Japanese doctor described an endemic occurrence in the northern district of Korea. In the 1930s, Dr. Takamori and his colleagues at Manchuria Medical College produced a series of reports on its endemiology, clinical and roentgenological findings observed in the north-eastern district of China. In 1940s, a Tokyo University group led by Dr. Ogata found that the salivary glands of KBD patients were markedly degenerated. Administration of the condensed water taken from the endemic area into experimental rats produced degeneration of the salivary glands and changes in bones and joints similar to those of KBD. Thus, they proposed parotin deficiency theory as the etiology of KBD, and they recommended parotin therapy for KBD in its early stage. In the 1950s, Dr. Takizawa and his colleagues at Chiba University demonstrated that ferulic acid and p-hydroxy-cinnamic acid, found in the drinking water in the endemic area, caused degeneration of the salivary gland in rats. They recommended boiling the drinking water or using activated charcoal for the prevention of KBD. In the 1970s, the Japanese Ministry of Health and Welfare made a nationwide survey for the incidence of KBD in Japan. They concluded that there was no case of KBD in Japan with the exception of a few patients who had been brought up in the northeastern district of China and later had moved to Japan.

Acetabular augmentation using a glass-ceramic block: 3 patients followed 3-4 years

We have developed a block of glass-ceramic to augment the dysplastic acetabulum. 3 patients with acetabular dysplasia underwent implantation of a block of glass-ceramic on the lateral surface of the ilium just above the hip joint. The patients did not require immobilization and returned to their daily lives, walking without a cane 4 weeks after the operation. The mean Harris hip score was 47 points preoperatively and 94 points 3 years postoperatively.

Cemented total hip arthroplasty with acetabular bone graft for developmental dysplasia. Long-term results and survivorship analysis

Although the technique of autogenous acetabular bone grafting has been widely used to augment containment of the acetabulum in total hip arthroplasty (THA) for developmental dysplasia, the role of this technique in improving long-term results remains controversial. We present the long-term results of cemented THA with acetabular bone grafting in 112 patients (133 hips) in order to clarify the factors which affect the outcome. The mean follow-up was for 12.3 years (8 to 24). Kaplan-Meier survivorship analysis predicted a rate of survival of the acetabular component at 15 years of 96% (95% confidence interval (CI) 92 to 99) with revision for aseptic loosening as the endpoint, and of 75% (95% CI 65 to 85) when radiological loosening was used. Parametric survivorship analysis using the Cox proportional-hazards model indicated that trochanteric nonunion, lateral placement of the socket, and delayed trabecular reorientation of the bone graft were risk factors for loosening of the acetabular component. Our findings have shown that autologous acetabular bone grafting is of value for long-term success provided that the risk factors are reduced.

A new bioactive bone cement: its histological and mechanical characterization

We have developed a bioactive bone cement using CaO-SiO 2-P 2O 5-CaF 2 glass powders and ammonium phosphate solution, and investigated its histological and mechanical characteristics in vivo. A bone defect was drilled in proximal metaphysis of the rat tibia and filled with the bioactive bone cement in paste form or polymethylmethacrylate (PMMA) bone cement in the dough state. The cements were allowed to harden in situ. Histological examination demonstrated direct bonding between the new cement and bone by 4 weeks. The bioactive bone cement did not degrade up to 24 weeks postimplantation. The inflammatory reaction to the bioactive bone cement was less intense than the reaction induced by PMMA. Changes in the mechanical properties of the cement in vivo were studied by implanting hardened cylindrical specimens of both types of cement into the hindlimb muscles of rats for 12 weeks. The compressive strength of the bioactive cement increased significantly after implantation, and reached 68 MPa in 1 week and 73 MPa in 4 weeks. These values were comparable to those of PMMA, and were maintained up to 12 weeks after implantation. This bioactive bone cement hardens in situ within a few minutes with negligible rise of temperature and can be easily handled as a paste for filling bone cavities of different shapes. In addition, this cement has good osteoconductive and bone bonding potential and fairly high mechanical strength. Therefore, this new cement could be used both as a bioactive bone cement and bone defect filler.

A bioactive glass powder-ammonium hydrogen phosphate composite for repairing bone defects

Bioactive glass powder (AW-G) was made into a rigid compound by mixing with ammonium hydrogen phosphate and was evaluated as a bone-defect filler. The proximal metaphysis of the rat tibia was drilled and packed with (a) polymethyl-methacrylate (PMMA) bone cement, (b) AW-G powder, (c) AW-G powder with ammonium hydrogen phosphate (AW-G)-(A-P), or (d) nothing, as a control. The animals, with different implantation periods up to 24 weeks, were sacrificed and the defective sites were histologically analyzed. The results revealed direct bonding between the bone tissue and the (AW-G)-(A-P). The general inflammatory reaction of (AW-G)-(A-P) was less than that of PMMA bone cement. The compressive strength of (AW-G)-(A-P) implanted subcutaneously into rats was measured chronologically and deterioration did not occur during a period of 24 weeks. The rigidity increased to 1.6 times 6 months after implantation as compared with the initial value. This compound can be used as paste and is transformed into a rigid compound in about 4 min without noticeable elevation of the temperature. Thus, this (AW-G)-(A-P) composite can be used as a bone defect filler, and there is a possibility that it can even be used as a bone cement if higher rigidity can be attained.

A new bioactive glass--ceramic as a coating material on titanium alloy

Apatite--wollastonite-containing glass--ceramic (A--W . GC) has a strong ability to bond to bone and relatively high mechanical strength. Therefore, as a bulk material it has recently been applied clinically even in load-bearing sites. In this study, we modified A--W . GC by altering its composition ratio with the removal of CaF 2 and the addition of B 2O 3, and examined the potential use of the resulting new glass--ceramic as a material for coating on a titanium (Ti) alloy. The bioactivity of this new coating (NC) material and its bonding ability to bone were investigated mechanically and histologically. After implantation of the Ti alloy plate coated with this material into the tibiae of rabbits for 2, 3, 4, 8, and 25 weeks, a detaching test was performed. The detaching failure load of the NC plates was compared with those of A--W . GC plates, hydroxyapatite (HA) plates, and uncoated Ti alloy plates implanted in the same way. The failure load of NC was as high as that of A--W . GC for all periods, whereas it was significantly higher at 3 and 4 weeks than that of HA. Uncoated Ti alloy showed lower failure loads for all periods, differing significantly from the other materials. There was no breakage or detachment of the coating layer observed after the detaching test. Histological examinations by CMR, Giemsa surface staining, and SEM-EPMA showed that NC bonded directly to bone without any intervening soft tissue layer. A calcium--phosphorus-rich layer (apatite layer) was observed within the coating layer, as is the case in A--W . GC. These results indicate that this new glass--ceramic has earlier bone-bonding ability and high mechanical strength, making it a promising coating material.

A new bioactive bone cement consisting of BIS-GMA resin and bioactive glass powder

We have developed a bioactive bone cement consisting of silane-treated CaO-SiO 2-P 2O 5-CaF 2 glass powder as the filling particles and bisphenol-a-glycidyl methacrylate (BIS-GMA) diluted with triethylene-glycol dimethacrylate (TEGDMA) as the organic matrix. Histological examination demonstrated direct bonding between the cement and bone along the circumference of the cement at 4 weeks after implantation in rat tibia. The compressive strength and toughness of the cement were two and four times greater than those of polymethylmethacrylate (PMMA) cement, respectively. The inflammatory reaction of the skin caused by the new cement was not as intense as that for PMMA 3 days after subcutaneous implantation. This new cement may be applicable as a bioactive bone cement with high mechanical strength.

Biodegradable screw fixation of rabbit tibia proximal osteotomies

The purpose of this study was to evaluate a biodegradable poly(L-lactide) (P-L-LA) screw for osteosynthesis under a load-bearing condition. A proximal tibial osteotomy on 25 rabbits was fixed with a biodegradable screw made of P-L-LA. A follow-up study was done at 1, 2, 4, 8, and 16 weeks. In another 25 rabbits, the tibial osteotomy was fixed with stainless steel (SUS) screws of the same size as the P-L-LA screws with a similar follow-up period. Radiographic, histological, microradiographic, and oxytetracycline-labeling studies showed healing of the osteotomy within 4 to 8 weeks. The displacement of fragments and the mass of newly formed bone around the screws were measured by histomorphometric analysis. There was no significant difference in the displacement of the fragments in these two groups and new bone was more abundantly detected in the P-L-LA group than in the SUS group. Histologically, no inflammatory lesion was detected in either group. All osteotomies united without delay and the displacement was minimal, although no external support was applied and the rabbits were allowed to move freely after the operation. The results of this study suggest a possible use for a P-L-LA screw in the clinical treatment of human bone fractures.

A study of the bioactive bone cement--bone interface: quantitative and histological evaluation

The interface between bone and a bioactive glass cement--a mixture of bioactive glass powder and ammonium phosphate solution, previously reported on by the authors--was evaluated quantitatively and histologically. The materials tested were (1) the original bioactive glass cement (BCI cement); (2) an improved type of bioactive glass cement (BCII cement); (3) polymethylmethacrylate (PMMA) bone cement; and (4) a bioactive, apatite-wollastonite-containing, glass ceramic (A-WGC). Hardened cylindrical specimens of each cement were inserted loosely into canine femora and the interfacial shear strengths were measured using a push-out test. The interfacial strength values of the bioactive glass cements increased with prolonged implantation time. At each postimplantation time studied (8, 12, and 24 weeks), the interfacial strength value of BCI cement did not differ significantly from that of A-WGC. BCII cement interfacial strength was greater than that of BCI cement, whereas the interfacial strength of PMMA bone cement remained at a very low level throughout the study. Histological examinations revealed that direct bonding of both bioactive glass cements to bone had occurred without pathologic degradation. After 24 weeks, the defects between the bone and the bioactive glass cements had been filled with mature lamellar bone. Because the bioactive glass cement system developed by the authors, especially BCII cement, shows excellent osteoconductivity and bonds to bone tightly, we consider it to be a promising material for fixing prostheses into bone.

Osteoconduction of bioceramics in normal and osteopenic rats: comparison between bioactive and bioinert ceramics

Rats with experimental osteopenia, which was induced by resecting both ovaries and sciatic nerves (OVX + NX), were used to evaluate osteoconduction of an apatite and wollastonite-containing glass-ceramic (designated A-W.GC) and an alumina ceramic. The bone mineral densities (BMDs) of the femurs were measured by dural energy X-ray absorptiometry (DEXA) and determination of the ash weight. Twelve weeks after the first operation, when the BMDs in the OVX + NX groups were about 20% less than that in the sham-treated groups (Sham), the bioceramics were implanted into the proximal tibiae. The bone mineral masses around the implants in the proximal tibiae were evaluated by histological examination of undecalcified specimens and DEXA. Both types of implants in the OVX + NX groups showed less reactive bone than those in the Sham groups. However, a histomorphological study revealed that the direct contact area between bone and implant was larger with bioactive ceramic A-W.GC than with the bioinert alumina ceramic even under osteopenic conditions while two types of ceramic made no difference on the bone at distance from the implant. The direct contact area with A-W.GC did not show any difference between the Sham and the osteopenic OVX + NX groups. The bioactive ceramic A-W.GC appears to have good osteoconductivity solely on its surface even under osteopenic conditions.

Effects of ions in aqueous media on hydroxyapatite induction by silica gel and its relevance to bioactivity of bioactive glasses and glass-ceramics

Hydroxyapatite induction by a synthesized pure silica hydrogel was examined in various simulated body fluids (SBFs) having different magnesium, calcium, and phosphate ion concentrations as well as pH values. The silica hydrogel generated biologically active apatite on its surface by taking up calcium and phosphorous ionic groups from a surrounding SBF that was prepared to emulate the human plasma in inorganic composition. The induction period for apatite nucleation on the surface of the silica was largely decreased with the addition of a small amount of the calcium or phosphate ions to the SBF and with an increase in pH, but increased with the addition of magnesium ion. Bioactivity of bioactive materials like Bioglass and glass-ceramic A-W was well interpreted in terms of the rate of apatite formation reflected in these results. Moreover, the results provide the basic knowledge for designing new bioactive materials.

Poly(vinyl alcohol) hydrogel as an artificial articular cartilage: evaluation of biocompatibility

We have developed a new poly(vinyl alcohol) hydrogel (PVA-H) of increased physical strength through a new manufacturing process. Its mechanical properties have been found to be preferable as a substitute for articular cartilage. To evaluate its biocompatibility as an artificial articular cartilage, a series of in vivo tests within the intraarticular, as well as the intramuscular, environment were conducted. Tissue reactions of cartilage, bone, synovium, and muscle to PVA-H were studied histologically. In the experimental group, in which PVA-H was implanted, inflammatory reactions of all of these tissues were very slight. In the control group, in which ultra-high molecular weight polyethylene (UHMWPE) was implanted, although tissue reactions of bone and muscle were as slight as in the experimental group, those of cartilage and synovium were somewhat more conspicuous. By way of these findings, the better biocompatibility of PVA-H was documented.

A heat-generating bioactive glass-ceramic for hyperthermia

Glass plates of the chemical composition: CaO (29.0), SiO 2 (31.0), Fe 2O 3 (40.0), B 2O 3 (3.0), P 2O 5 (3.0) in weight ratio were heated to 1050 degrees C at a rate of 5 degrees C/min and then cooled to laboratory temperature. The resulting glass-ceramic containing magnetite and wollastonite crystals showed high-saturation magnetization. The bonding ability of this new glass-ceramic to bone tissue was evaluated using rabbit tibiae, and compared with glass of the same composition. This glass-ceramic formed a Ca, P-rich layer on its surface and bonded tightly with bone within 8 weeks of implantation. However, the glass did not form this Ca, P-rich layer, nor had it bonded with bone at 25 weeks. The bone-heating ability of this glass-ceramic was investigated by applying a max. 300-Oe, 100-kHz magnetic field. The granules of the glass-ceramic filled in the rabbit tibiae heated the whole surrounding bone to more than 42 degrees C and maintained this temperature for 30 min. Bioactive ceramics reinforce the mechanical strength of bone tissue. Furthermore, this heat-generating bioactive glass-ceramic can be used for hyperthermic treatment of bone tumors.

Development of bioactive bone cement and its clinical applications

This paper is a summary of already published papers on the bioactive bone cement (BA cement) which consists of CaO-SiO2-P2O5-MgO-CaF2 (AW glass-ceramic) powder and bisphenol-a-glycidyl methacrylate (Bis-GMA) resin. Two types of BA cement, dough and injection type, were prepared by changing their chemical compositions slightly. They harden in a few minutes exhibiting much lower curing temperature than PMMA cement. They have significantly higher compressive, bending, and tensile strengths than PMMA cement and have a character of bonding directly with bone in 4-8 weeks in vivo. Intercalary prosthetic replacement of the femur and total prosthetic replacement of the hip were performed in dogs using either PMMA cement or BA cement. Mechanical tests demonstrated that fixation strengths of these prostheses with BA cement increased with time and were significantly greater than those with PMMA cement tested at any time. Results of histological examinations showed direct bonding between BA cement and bone, and that the bone trabeculae around BA cement mantle grew with time, while with PMMA cement an intervening soft tissue layer was always observed at the cement-bone interface. BA cement was used in a few aged patients to install a hip prosthesis either in cases of revision or femoral neck fracture. The longest follow-up period of the patient is 4 yrs. The patients have been doing well with no adverse effect of the cement to date.

X-ray absorption fine structure of V(2)O(5) and Li(x)V(2)O(5)

Vanadium K-edge XAFS measurements of five compounds were carried out. The compounds studied were crystalline V(2)O(5) and four types of Li(x)V(2)O(5) with different insertion levels x, which show different EMFs (2.0-3.4 V). The EXAFS data analysis shows no remarkable difference in the V-O distances in the five compounds, showing that the structure of the VO(5) square pyramids changes only slightly as lithium atoms are intercalated into the V(2)O(5). In the XANES spectra, three peaks are observed for crystalline V(2)O(5) and Li(x)V(2)O(5) (3.4 V). When the EMF is decreased, the intensity difference between the first and second peaks disappears and the third peak shifts to lower energy. The XANES data were analysed using full multiple-scattering calculations. In the calculated spectra the intensity of the first peak increases as the V(2)O(5) intercalates lithium atoms.

Nerve regeneration over a 20-mm gap through a nerve conduit containing blood vessels in rats: the influence of interstump distance on nerve regeneration

BACKGROUND

The present study was conducted in rats to investigate whether a tube with additional intrachamber vascularization could permit axons to extend over a distance greater than 10 mm, which appears to be the maximum axon regeneration distance for rat sciatic nerve axons through a normal empty tube.

METHODS

A sural vessel-containing tube (VCT) was designed and interposed between transected sciatic nerve stumps in the thigh, leaving a 20-mm interneural gap.

RESULTS

Twelve weeks after tubulation, six out of nine rats showed successful nerve regeneration and re-innervation of the soleus muscle using the VCT. At 24 weeks, intrachamber nerve regeneration and re-innervation of the soleus and pedal adductor muscles were electrophysiologically and histologically confirmed in all rats. However, no neural tissue was observed within any ligated sural vessel-containing tube (LVCT) or empty unmodified tube (ET) with a 20-mm interneural gap. When nerves regenerated in the VCT with a 20-mm gap were compared with those regenerated in a VCT with a 10-mm gap 12 and 24 weeks after surgery, the results produced by the VCT with a 20-mm gap were inferior to those after use of the VCT with a 10-mm gap, except for motor nerve conduction velocity at 24 weeks.

CONCLUSIONS

The value recovered to almost identical levels (about 50-60% normal) in both groups.

Nerve regeneration over a 25 mm gap in rat sciatic nerves using tubes containing blood vessels: the possibility of clinical application

This study was undertaken to investigate the effect of including vessels in a tube used to promote nerve regeneration across a gap. A tube containing sural vessels was designed in a rat model and interposed between the proximal and distal stumps of a divided sciatic nerve, leaving a 25 mm gap. At 12 weeks, a few myelinated axons were seen at the most distal parts of regenerated nerves in 6 out of 10 rats, none of which evoked action potentials in the tibialis anterior muscle, but by 24 weeks all the rats had developed neural tissue in the tubes, which evoked action potentials in the muscle. The vessels within the tube enhanced nerve regeneration and its distance up 25 mm. This type of vessel-containing tube would be useful for the repair of divided human peripheral nerves with long gaps, almost equivalent to or slightly longer than the maximum length over which nerve fibres can regenerate through a unvascularised unmodified tube.

Prosthetic replacement of the hip in dogs using bioactive bone cement

Total hip arthroplasties were performed in dogs using bioactive bone cement consisting of silane treated CaO-MgO-SiO2-P2O5-CaF2 glass powder as the filling particles and bisphenol-a-glycidyl methacrylate based resin as the organic matrix, and the outcomes were compared with the results of polymethylmethacrylate bone cement. The mechanical properties of the bioactive bone cement were stronger than the mechanical properties of polymethylmethacrylate bone cement. The bonding strength of the bioactive bone cement to bone in dogs' femora increased with time, reaching 4.7 MPa at 6 months, whereas that of polymethylmethacrylate bone cement did not increase, remaining at 1.0 MPa. Results of histologic examination showed direct bonding between the bioactive bone cement and bone, and the bony trabeculae around the cement mantle grew with time. However, in polymethylmethacrylate bone cement, an intervening soft tissue layer was evident at the bone cement interface. Direct bonding of the bioactive bone cement at the interface through an apatite layer of 30 microm in thickness was shown through observation with the scanning electron microscopy. Using this bioactive bone cement in clinical settings may help alleviate serious problems associated with cemented total hip arthroplasty, such as aseptic loosening of the implant and mechanical failure of the bone cement.

INTERCALARY REPLACEMENT OF CANINE FEMORA USING A NEW BIOACTIVE BONE CEMENT

We have developed a bioactive bone cement (BA cement) consisting of Bis-GMA resin and bioactive glass powder. It has high compressive and tensile strengths, a low curing temperature and its bioactivity allows it to bond directly with bone.

We operated on the 18 femora of nine mongrel dogs for intercalary replacement of part of the bone by a metal prosthesis using either PMMA cement or BA cement for fixation. Three dogs were killed at each of 4, 12 and 26 weeks after surgery for the evaluation of fixation strength by a push-out test and for histological examination by Giemsa surface staining and SEM.

Fixation strengths with PMMA cement at 4, 12 and 26 weeks after surgery were 46.8 ± 18.9, 50.0 ± 24.7, and 58.2 ± 28.9 kgf (mean ±SD), respectively. Those with BA cement were 56.8 ± 26.1, 67.2 ± 19.2, and 72.8 ± 22.2 kgf, respectively. Fibrous tissue intervened between bone and PMMA cement but BA cement had bonded directly to bone at 12 and 26 weeks. This suggests that BA cement will be useful in providing long-lasting fixation of implants to bone under weight-bearing conditions.

Intercalary replacement of canine femora using a new bioactive bone cement

We have developed a bioactive bone cement (BA cement) consisting of Bis-GMA resin and bioactive glass powder. It has high compressive and tensile strengths, a low curing temperature and its bioactivity allows it to bond directly with bone. We operated on the 18 femora of nine mongrel dogs for intercalary replacement of part of the bone by a metal prosthesis using either PMMA cement or BA cement for fixation. Three dogs were killed at each of 4, 12 and 26 weeks after surgery for the evaluation of fixation strength by a push-out test and for histological examination by Giemsa surface staining and SEM. Fixation strengths with PMMA cement at 4, 12 and 26 weeks after surgery were 46.8 +/- 18.9, 50.0 +/- 24.7, and 58.2 +/- 28.9 kgf (mean +/-sD), respectively. Those with BA cement were 56.8 +/- 26.1, 67.2 +/- 19.2, and 72.8 +/- 22.2 kgf, respectively. Fibrous tissue intervened between bone and PMMA cement but BA cement had bonded directly to bone at 12 and 26 weeks. This suggests that BA cement will be useful in providing long-lasting fixation of implants to bone under weight-bearing conditions.

Transmission electron microscopy observations at the interface of bone and four types of calcium phosphate ceramics with different calcium/phosphorus molar ratios

Four kinds of calcium phosphate ceramics, beta-calcium pyrophosphate (Ca2P2O7), beta-tricalcium phosphate (Ca3(PO4)2), hydroxyapatite (Ca10(PO4)6(OH)2) and tetracalcium phosphate (Ca4(PO4)2O), were prepared. The calcium/phosphorus molar ratios were 1, 1.5, 1.66 and 2, respectively. Particles (150-300 microns) of these ceramics were packed into holes (diameter 2.5 mm) made in the tibial metaphysis of mature male rats. At 2 weeks, 4 weeks, 8 weeks and 6 months after the operation, undecalcified specimens were prepared. Transmission electron microscopy showed that the bone-bonding behaviour of calcium phosphate ceramics at the interface with bone did not vary with the calcium/phosphate molar ratio. Amorphous substances or needle-like microcrystals were observed on the surface of the ceramics at 2 weeks after implantation. The ceramics showed direct continuity with small crystallites of bone tissue at 4 weeks, 8 weeks and 6 months after implantation. The ceramics appeared to be getting smaller with time. Collagen fibres were not observed at the bone/ceramic interface. Neither chemical bonding nor mechanical bonding by interlocking between bone and ceramics was described by morphological observation using transmission electron microscopy.

Bone-bonding behavior under load-bearing conditions of an alumina ceramic implant incorporating beads coated with glass-ceramic containing apatite and wollastonite

Alumina ceramic with a porous surface coated with glass-ceramic containing apatite and wollastonite (AW-GC) was implanted in a state of press-fit under load-bearing conditions in the femoral condylus of the mongrel dog and compared with a non-glass-ceramic-coated alumina ceramic. A trapezoid alumina ceramic implant (7 x 10 x 5 mm) with a lateral recess (0.9 mm deep) coated with alumina ceramic beads (mean diameter, 750 microns) in a single layer was prepared. The alumina ceramic beads were bonded to the alumina ceramic substratum using an identical alumina binder. The thickness of coating was 10-50 microns (mean, 30 microns). The surface of the beads and the substratum of the alumina implant were coated with AW-GC. A pull-out test and histologic examination were performed at 4, 8, and 24 weeks after implantation. The interfacial shear load was significantly increased from 8 to 24 weeks in both groups. The shear load of the glass-ceramic-coated implant was significantly greater than that of the noncoated implant at every stage. The interface shear load of the noncoated implant was 12.13 +/- 2.76 kg at 4 weeks, 13.92 +/- 4.18 kg at 8 weeks, and 24.17 +/- 5.17 kg at 24 weeks after implantation. The interface shear load of the glass-ceramic-coated implant was 17.96 +/- 2.81 kg at 4 weeks, 24.92 +/- 9.87 kg at 8 weeks, and 34.83 +/- 4.12 kg at 24 weeks after implantation. Histologic examination showed more ingrown bone tissue in the glass-ceramic-coated implants. It is suggested that AW-GC stimulated the bone ingrowth.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between axonal regeneration and vascularity in tubulation--an experimental study in rats

This study investigated the effect of vascularity in a nerve conduit on peripheral nerve regeneration. The effect of three different types of tube (empty, blood vessel-containing and ligated vessel-containing) was compared using a rat sciatic nerve preparation with a 10-mm gap. Nerve regeneration through the vessel-containing tube was more efficient than in the other tubes 6 and 12 weeks after tubulation surgery, but there were no statistically significant differences among the three types of tube after 24 weeks. Electrophysiological, histological and microangiographic studies showed that vessels which were preinserted in the nerve conduit accelerated axonal regeneration through rapid capillary formation in the tube.

Tissue reaction of bioabsorbable ultra high strength poly (L-lactide) rod. A long-term study in rabbits

Bioabsorbable ultra high strength poly (L-lactide) rods, which were developed for internal fixation of fractures, were fabricated using a drawing technique. These rods were implanted in the subcutaneous tissue and in the medullary cavity of rabbits to investigate tissue reactions to poly (L-lactide) and to study their degradation process. After 18 months, histiocytes were found, and their phagocytic activity continued for as long as 42 months, with maximum activity observed between 24 and 36 months after implantation. At 62 months after intramedullary implantation, the materials had been absorbed almost completely and were replaced by bone marrow cells, with only a small amount of residual tissue reaction. At 69 months after subcutaneous implantation, the materials had been absorbed completely without any scar formation. During degradation, no foreign body giant cells were found and osteolytic expansion caused by liquid degradable materials was not seen.

Anterior decompression and fusion for ossification of posterior longitudinal ligament in the thoracic spine

Twelve cases are reviewed of ossification of posterior longitudinal ligament (OPLL) in the thoracic spine for which anterior decompression and fusion were performed. A transthoracic approach was used in 10 patients, and median sternotomy and a transsternal approach were used in one each. The clinical symptoms and the Japanese Orthopaedic Association (JOA) score improved in 10 patients, whereas they were unchanged in two patients who underwent a revision operation for a previous laminectomy. An anterior procedure that results in adequate decompression of the spinal cord and good spinal stability is recommended for anterior lesions, such as OPLL, which compress the anterior spinal cord at each level of the thoracic spine.

m-calpain in rat growth plate chondrocyte cultures: its involvement in the matrix mineralization process

m-Calpain, a Ca(2+)-dependent neutral cysteine proteinase (EC 3.4.22.17), has been demonstrated to be present in the lower hypertrophic zone of the rat growth plate. Using the pelleted culture system as an in vitro model of rat epiphyseal chondrocyte differentiation, we studied m-calpain contents and activities in pelleted cultures during chondrocyte differentiation and the role of m-calpain in the mineralization process. m-Calpain was demonstrated immunohistochemically in epiphyseal chondrocytes, and immunoreactive m-calpain content in cells increased with terminal differentiation into hypertrophic cells. Immunoblotting also showed the association of the increase in m-calpain in cell pellets and in cell culture medium with development of the culture. Ca(2+)-dependent caseinolytic activities of m-calpain extracted from cell pellets and from the medium increased with chondrocyte differentiation, coincident with the increase in enzyme content. The inhibition of m-calpain by the addition of calpastatin, a specific inhibitor of calpain, caused suppression of matrix mineralization in pelleted cultures; the addition of E-64c, a specific inhibitor of cysteine proteinases, during the mineralization stage also caused a significant inhibition of the matrix mineralization. The addition of E-64c resulted in altered composition of proteoglycan monomers and aggregates in cell pellets and in suppression of mineral growth. These findings support an important role of cysteine proteinases, especially m-calpain, in the regulation of the cartilage mineralization process through proteoglycan degradation.

Appearance of calpain correlates with arthritis and cartilage destruction in collagen induced arthritic knee joints of mice

OBJECTIVES

To determine the relevance of calpain in murine collagen induced arthritis (CIA) and to correlate the presence of m-calpain with the appearance of arthritis and cartilage destruction.

METHODS

The immunohistochemical appearance and localisation of m-calpain at different stages of arthritis were analysed and compared with the histological changes occurring during type II CIA. The arthritic knee joint lavage was also examined for m-calpain by immunoelectrophoretic blotting.

RESULTS

Immunohistochemical staining demonstrated a clear positive correlation between the appearance of m-calpain and both a histological grade of arthritis and an acute phase of cartilage destruction. Further development of the disease showed continual presence of m-calpain but with reduced intensity. Intra-articular inflammatory cells (mainly polymorphonuclear leucocytes, synovial lining cells, and sublining fibroblasts) were found to be the most positively stained, but extracellular localisation of m-calpain on the surface of cartilage and synovium, and in the articular cartilage matrix and chondrocyte lacunae, was also observed. In the knee joint lavage obtained at the most intensive stage of acute arthritis, m-calpain was detectable by immunoelectrophoretic blotting.

CONCLUSIONS

The findings suggest that m-calpain may act at an early phase of CIA as a matrix proteinase and take part in the destruction of articular cartilage or activate other destructive enzymes.

Biodegradable plate fixation of rabbit femoral shaft osteotomies. A comparative study

Femoral shaft transverse osteotomies in 58 rabbits were fixed with ultrahigh strength poly-L-lactic acid plates made by a drawing technique. Similar osteotomies in another 35 rabbits were fixed using stainless steel plates. The union rate, the mechanical strength of the united bones, bone mineral content and density in the area beneath the plate using dual energy x-ray absorptiometry, and the cortical thickness beneath and opposite the plate using a digitizer was compared between the poly-L-lactic acid and stainless steel groups after postoperative periods of 8, 25, and 40 weeks. The poly-L-lactic acid and stainless steel groups showed union rates of 67% (39 of 58) and 80% (28 of 35) without displacement, respectively. In the poly-L-lactic acid group, plate failure occurred in 14% (8 of 58). The mechanical strength of the specimen was restored to a level equal to that on the untreated side by 25 weeks, and cortical thickness and bone mineral content and density were maintained almost normal for 40 weeks in the poly-L-lactic acid group. The stainless steel group showed significantly lower mechanical strength and led to osteopenia because of stress shielding after 25 weeks.

Two-stage reconstruction for the hypoplastic thumb

A 2-year-old boy with grade 3 hypoplastic thumb (Blauth's classification) underwent reconstruction in two stages. Stage 1 was an abductor digiti quinti musculocutaneous flap, first web space widening, and insertion of a silicone rod to prepare for a flexor pollicis longus transfer. Stage 2 (6 months later) was a vascularized second toe proximal interphalangeal joint transfer for carpometacarpal joint replacement, plus tendon transfers for thumb flexion, extension, and adduction. Three years following the procedures, the thumb had an open physis by x-ray film and was functioning well. Pollicization is the traditional procedure for this degree of thumb hypoplasia, but the two-stage reconstruction is an alternative for patients in cultures where the presence of five fingers is important.

Bioactive bone cement: the effect of amounts of glass powder and histologic changes with time

A study was conducted to examine the influence of the amount of glass powder added to a bioactive bone cement of our formula on its mechanical and biologic properties. Serial changes in the cement with time were also examined. The bioactive bone cement consisted of CaO-SiO2-P2O5-CaF2 glass powder and bisphenol-a-glycidyl methacrylate resin. Glass powder was added to the cement in 30, 50, 70, and 80% weight ratios. The compressive strengths of the resulting cements (171-239 MPa) were more than double that of polymethylmethacrylate cement (68 MPa). Histologic examination of rat tibiae bearing artificial defects packed with each bioactive cement showed direct bone contact 4 weeks after surgery. The cement with a higher percentage of glass powder showed better direct formation of bone around its periphery with a thicker reactive layer. Under scanning electron microscopic observation, the reactive layer showed increased levels of calcium and phosphorus. Examination of histologic changes up to 26 weeks showed progressive bone formation around the cement and no sign of biodegradation.

Diagnostic value of Tc-99m (V) DMSA for chondrogenic tumors with positive Tc-99m HMDP uptake on bone scintigraphy

Technetium-99m (V) DMSA scintigraphy was performed in 17 patients with 37 chondrogenic tumors (13 osteochondromas, 14 enchondromas, and 10 chondrosarcomas) that had previously shown uptake of Tc-99m HMDP. Technetium-99m (V) DMSA showed high uptake by all chrondrosarcomas, but low or no uptake always indicated benign chondrogenic tumors. Technetium-99m (V) DMSA scintigraphy may be superior to Tc-99m HMDP scintigraphy for distinguishing benign and malignant chondrogenic tumors, and could also be useful for diagnosing the malignant transformation of chondrogenic tumors.

Influence of disodium (1-hydroxythylidene) diphosphonate on bone ingrowth into porous, titanium fiber-mesh implants

The influence of disodium (1-hydroxythylidene) diphosphonate on the bonding between bone and porous, titanium fiber-mesh implants was studied. Rectangular, porous, titanium fiber-mesh implant (15 x 10 x 2.4 mm) were implanted into the tibial bone of mature male rabbits. The rabbits were divided into six groups. Disodium diphosphonate was administered daily by subcutaneous injection to groups 1-5. Groups 1-4 received doses of 5.0, 2.5, 1.0, and 0.1 mg per kilogram of body weight per day for 8 weeks, respectively. Group 5 received a dose of 5 mg per kilogram of body weight per day for 4 weeks. Group 6 (control group) was given saline injections. At 8 weeks after implantation, the rabbits were killed. The tibiae containing the implants were dissected out and subjected to detachment tests. The failure load, when an implant became detached from the bone or when the bone itself broke, was measured. The interface of the bone and implant was investigated by Giemsa surface staining and contact microradiography. Giemsa surface staining and contact microradiography showed that porous implant bonding to bone tissue was inhibited by a high dose of disodium diphosphonate in groups 1, 2, and 5. Soft tissue was observed at the interface. In groups 3, 4, and 6, bone tissue ingrowth was observed at the interface between the porous implant and bone tissue. Growth of bone into the porous fiber-mesh implant of a cementless prosthesis is possible if a low dose of diphosphonate below 1.0 mg per kilogram of body weight is given subcutaneously.

Scanning electron microscopy-electron probe microanalysis study of the interface between apatite and wollastonite-containing glass-ceramic and rabbit tibia under load-bearing conditions after long-term implantation

Glass-ceramic implants containing oxy- and fluoroapatite [Ca10(PO4)6(O, F2)] and beta-wollastonite (CaSiO3) were studied under load-bearing conditions in a segmental replacement model in the tibia of the rabbit. A 16-mm segment of the middle of the tibial shaft was resected at a point distal to the junction of the tibia and the fibula. The defect was replaced by a 15 mm-long hollow, cylindrical implant that was fixed by intramedullary nailing using Kirschner wire. The implants were 9 mm in diameter and 15 mm long bearing a central hole 3.05 mm in dianeter. The rabbits used were killed 6 months, 1 year, 18 months, and 2 years after implantation. The interface between the bone and the glass-ceramic was investigated by scanning electron microscopy-electron-probe microanalysis (SEM-EPMA). None of the glass-ceramic implants broke, and the glass-ceramic had bonded directly to the bone tissue without any intervening soft tissue. A calcium-phosphorus layer (Ca-P layer) was observed at the glass-ceramic/bone interface. This layer was 30-100 microns thick at 6 months after implantation, 60-110 microns thick at 1 year after implantation, 80-200 microns thick at 18 months, and 120-350 microns thick at 2 years. At the lateral surface of the glass-ceramic uncovered by the bone, the calcium-phosphorus layer was 50-80 microns thick at 6 months after implantation, 250-450 microns thick at 1 year, 300 approximately 400 microns thick at 18 months, and 300 microns thick at 2 years. The thickness of the calcium-phosphorus layer increased moderately after long-term implantation. However, it was difficult to estimate the rate of increase in the thickness of calcium-phosphorus layer.

Autogenous callo-osseous grafts for the repair of osteochondral defects

We describe a new method of biological repair of osteochondral defects. In rabbit knees an osteochondral defect was reconstructed with a callo-osseous graft made of a superficial sheet of medullary fracture callus attached to a base of cancellous bone. This was taken from the iliac bone of the same animal which had been osteotomised ten days earlier. The reparative tissues were evaluated for 24 weeks by quantitative histology, biochemical analysis of the uronic acid content, and immunohistochemical staining of collagen constituents. The callo-osseous graft provided significantly faster and better repair of the articular surface than an untreated defect or a callo-osseous graft in which the cells had been devitalised by irradiation before transplantation. Our findings indicate that the callo-osseous graft contributes to the repair process by providing both favourable extracellular matrices and pluripotential mesenchymal cells. Our study tested the hypothesis that early medullary callus generates hyaline cartilage instead of bone after transfer to an articular surface.

Toe-to-finger transfer combined with wrap-around flap: a new technique for four-finger amputation

A surgical technique for reconstruction of four-finger amputation, toe-to-finger transfer combined with wrap-around flap procedure, is described. Opposable ulnar fingers, reconstructed using the second and third toe, provide sufficient grip function. The long finger, reconstructed with the wrap-around flap using the lateral aspect of the great toe, provides pinch function. Improving the hand function is worthwhile despite morbidity from losing two toes.

Apatite coated on organic polymers by biomimetic process: improvement in its adhesion to substrate by glow-discharge treatment

A dense, uniform, and highly biologically active bone-like apatite layer can be formed in arbitrary thickness on any kind and shape of solid substrate surface by the following biomimetic method at ordinary temperature and pressure: First, a substrate is set in contact with particles of bioactive CaO-SiO2-based glass soaked in a simulated body fluid (SBF) with inorganic ion concentrations nearly equal to those of human blood plasma so that a number of apatite nuclei are formed on the substrate. Second, the substrate is soaked in another solution with ion concentrations 1.5 times those of SBF (1.5SBF) so that the apatite nuclei grow in situ. In the present study, organic polymer substrates were treated with glow-discharge in O2 gas atmosphere, then subjected to the above-mentioned biomimetic process. The induction periods for the apatite nucleation on all the examined organic polymers were reduced from 24 to 6 h, with glow-discharge treatment. The adhesive strengths of the formed apatite layer to the substrates increased from about 4 to 10 MPa for poly(ethylene terephthalate) and poly-ether sulfone, and from 1 approximately 2 to 6 approximately 7 MPa even for poly(methyl methacrylate), polyamide 6 and polyethylene. It is supposed that highly polar groups such as carbonyl, ester, hydroxyl, and carboxyl ones formed by glow-discharge treatment increased the affinity of a silicate ion with the substrates to decrease the induction period, and also increased the affinity of the apatite with the substrate to increase the adhesive strength.(ABSTRACT TRUNCATED AT 250 WORDS)

Autogenous callo-osseous grafts for the repair of osteochondral defects

We describe a new method of biological repair of osteochondral defects. In rabbit knees an osteochondral defect was reconstructed with a callo-osseous graft made of a superficial sheet of medullary fracture callus attached to a base of cancellous bone. This was taken from the iliac bone of the same animal which had been osteotomised ten days earlier. The reparative tissues were evaluated for 24 weeks by quantitative histology, biochemical analysis of the uronic acid content, and immunohistochemical staining of collagen constituents. The callo-osseous graft provided significantly faster and better repair of the articular surface than an untreated defect or a callo-osseous graft in which the cells had been devitalised by irradiation before transplantation. Our findings indicate that the callo-osseous graft contributes to the repair process by providing both favourable extracellular matrices and pluripotential mesenchymal cells. Our study tested the hypothesis that early medullary callus generates hyaline cartilage instead of bone after transfer to an articular surface.

Proteoglycan degradation in hemarthrosis. Intraarticular, autologous blood injection in rat knees

We determined the degradation of articular cartilage proteoglycans in a single episode of experimental hemarthrosis in rat knees. The right knee joints of rats were injected once with autologous whole blood. Both knee joints were examined histologically. Biochemical studies of cartilage proteoglycans extracted from the knees were also conducted. Histological examination revealed an accumulation of mononuclear cells in intraarticular fibrin clots and subsynovial layers 8 hours after the injection of blood. Accordingly, initiation of proteoglycan degradation occurred 8 hours after injection of blood, lasting from 1 day of limited degradation to 3 days; recovery then occurred within 7 days. The proteoglycan degradation could be inhibited by 1 mM phenylmethylsulfonyl fluoride, a general serine proteinase inhibitor, 0.1 M 6-aminohexanoic acid, a specific inhibitor of plasminogen activators, 10 mM EDTA, and 10(-6) to 10(-8) M dexamethasone, indicating that the accumulation of mononuclear cells in intraarticular fibrin clots and subsynovial layers may play an important role in cartilage damage.

Bone-bonding behavior of titanium alloy evaluated mechanically with detaching failure load

Although titanium (Ti) and Ti alloy are generally classified as bioinert materials in terms of their bonding to bone tissue, it is still unclear whether they bond chemically to bone. In this study, we examined the bone-bonding ability of Ti alloy (Ti-6Al-4V) using smooth-surfaced plates under non-load-bearing conditions. The bone-bonding behavior was evaluated mechanically by means of the detaching test reflecting tensile force. After implantation of the plates into the tibiae of rabbits for 4, 8, 16, and 25 weeks, detaching tests were performed. The failure load of the Ti alloy plates was close to 0 kg at 4 and 8 weeks, but gradually increased with time, reaching 0.334 kg at 16 weeks and 2.852 kg at 25 weeks on average. Histologic examination by Giemsa surface staining and SEM showed no differences between specimens at 8, 16, and 25 weeks, when Ti alloy plate made direct content with bone without any fibrous tissue. By SEM-EPMA, no clear calcium-phosphorus (Ca-P)-rich layer at the interface between the Ti alloy and bone tissue was evident, although a thin bone tissue was observed on the detached Ti alloy plate. The present results indicate that from both mechanical and histologic viewpoints, Ti alloy bonds directly to bone under static conditions after some time, probably more than 8 weeks. The possibility of chemical bone-bonding of Ti alloy was suggested.

Growth of severed flexor tendons in chickens

To examine tendon growth in both the distal and proximal portions of severed tendons, we investigated the growth of severed flexor tendons within the fibro-osseous tunnel in young chickens. When the tendon was severed at the proximal site in the sole, dynamic tension applied by the muscle was lost. Growth in the distal tendon was retarded considerably, although passive tension initially was maintained through the residual vincula and later by adhesion to the chiasma of adjacent flexors. When the tendon was severed at the insertion, passive tension from the extensors was lost. Proximal tendon growth continued if active tension was maintained through the residual vincula. If not, the tendon was markedly shortened and degenerated. Maintaining normal tension may be the most important factor in longitudinal tendon growth.

Drug release from a novel self-setting bioactive glass bone cement containing cephalexin and its physicochemical properties

A novel device containing cephalexin as a model drug using a self-setting bioactive cement based on CaO-SiO2-P2O5 glass was investigated. The device consisted of 95 wt/wt% glass powders and 5 wt/wt% cephalexin powder hardened within 5 min after mixing with a phosphate buffer. After setting, in vitro drug release from homogeneous or heterogeneous drug-loaded cement pellets in a simulated body fluid (SBF) at pH 7.25 and 37 degrees C continued for over 4 weeks. The hardened cement gradually formed low-crystallinity hydroxyapatite with high bioactivity in hard bone tissue and reduced in volume by about 5% during dissolution testing in SBF. Consequently, 30% of the loaded drug was squeezed from the cement system at the initial stage of the drug release, and the remainder released more slowly. Because the heterogeneous system consisting of the cement and drug-loaded pellet avoided the drug-squeezing effect, it showed a longer drug release term than the homogeneous drug-loaded cement. The heterogeneous system using the hardened cement after soaking in SBF at 37 degrees C for 10 days showed very slow drug release at the initial stage because it completely avoided the drug-squeezing effect, and the release was a zero-order pattern.

The effects of intraoperative radiotherapy on bone-healing ability in relation to different doses and postradiotherapy intervals

PURPOSE

Alterations in bone-healing ability after intraoperative radiotherapy were investigated in relation to different doses and postradiotherapy intervals in an experimental model.

METHODS AND MATERIALS

Bilateral osteotomy of the fibulae of 56 rabbits was carried out either immediately, 13 weeks or 39 weeks after unilateral intraoperative radiotherapy with 10-MV X ray using one of three doses, 25, 50, or 100 Gy. The healing of the fibulae was evaluated radiographically and histologically 13 weeks after the osteotomy.

RESULTS

Bone-healing ability was irreversibly reduced in all irradiated fibulae and these damages occurred in a dose-dependent manner. The severity of the damage also tended to increase with the time interval between irradiation and osteotomy. This interval-related aggravation was characterized by augmented bone loss at the osteotomy ends and atrophy of the neighboring areas.

CONCLUSION

These results serve as useful information concerning the surgical intervention of irradiated bone during and after intraoperative radiotherapy, and also after conventional radiotherapy.

Bioabsorbable osteosynthetic implants of ultra high strength poly-L-lactide. A clinical study

We have developed reasonably strong but bioabsorbable osteosynthetic screws, pins and nails made of ultra high strength poly-L-lactide (PLLA) and evaluated their use in 143 patients. The PLLA implants have the highest strength among those reported to date. They lose about 10% of their initial strength within 8 weeks, about 40% within 4 weeks and nearly 100% within 20 weeks in vivo. The patients were aged from 9 to 78 years, and the follow up was from 2 to 6 years. The implants were used for fixation of bone grafts in 84 patients, peri- and intra-articular fractures in 49, after osteotomy in 8, and in 2 others. Bony union was not achieved in only one case. In the early stages of the study, breakage of screws occurred in 12 cases (8%), mostly because of an inappropriate size of tap; these problems have not occurred after improvement of the tapping system. There were no cases with abnormal blood tests, infection or foreign body reaction.