In vivo hydroxyapatite formation induced by lipids

Proteolipids and complexed acidic phospholipids that cause in vitro hydroxyapatite formation, similarly cause hydroxyapatite deposition in 10-mu pore Millipore chambers when implanted in rabbit muscle pouches. The amount of mineral deposited during a 3-week period, based on the calcium and phosphate contents of the chambers, was directly related to the dry weight of the lipid implanted in the chamber. Chambers containing total lipid extract from rabbit bone from which the complexed acidic phospholipids had been removed, acidic phospholipids from which the the proteolipids had been removed, and empty chambers did not accumulate any detectable mineral during the course of the study. Chambers implanted with synthetic hydroxyapatite served as controls for chemical analyses. The presence of hydroxyapatite in the chambers was established 3 weeks after implantation based on electron microscopic, compositional, and wide-angle X-ray diffraction analyses of the deposits. In the cell-free chambers, lipid-induced hydroxyapatite deposition, but not bone matrix formation occurred. This study demonstrates that proteolipids and complexed acidic phospholipids can cause hydroxyapatite mineral deposition in a physiologic environment. To date, these lipids are the only materials isolated from mineralizing tissues, other than reconstituted collagen, that have been shown capable of causing in vivo mineralization in the absence of cells.     

Chemical changes in hydroxyapatite biomaterial underin vivo andin vitro biological conditions

Summary The introduction of a synthetic calcium phosphate into a biological environment is likely to result in surface-mediated chemical events. On the basis of such an assessment, we studied the chemical changes occurring in the mineral after exposure of a synthetic hydroxyapatite ceramic to bothin vivo (implantation in human) andin vitro (cell culture) conditions. A small amount of the material was phagocytized but the major remaining part behaved as a secondary nucleator as evidenced by the appearance of a newly formed mineral. Morphologically, the newly formed mineral appeared as tiny crystals precipitated and grown from the surface of the initial synthetic crystals. The density of the additional mineral increased from the periphery to the core of each biomaterial aggregate. Chemically, it was identified by IR spectroscopy as a carbonated apatitic mineral. We propose that the adsorption of biomolecules could inhibit precipitation, accounting for the increasing amount of precipitate from the periphery to the core of the aggregates.     

锶羟基磷灰石生物活性骨水泥应用于髋关节置换的研究

目的探讨锶羟基磷灰石（St-HA）生物活性骨水泥应用于髋关节置换的可行性。方法对Sr—HA生物活性骨水泥的力学特性及其在体应用于髋关节置换及髋关节翻修的生物学特性与聚甲基丙烯酸甲酯（PMMA）骨水泥进行比较及评价。结果Sr-HA生物活性骨水泥与PMMA骨水泥抗压缩强度相似，但其断裂韧度却高于PMMA骨水泥；在体研究表明Sr-HA生物活性骨水泥能与骨形成骨性融合，其与骨界面的剪切力明显大于PMMA骨水泥。结论Sr—HA生物活性骨水泥具有替代PMMA骨水泥应用于髋关节置换的潜力。     

In vivo strength enhancement of hydroxyapatite combined with rhBMP-2

Combinations of hydroxyapatite (HAP) and bone morphogenetic protein (BMP) are anticipated to provide potent alternatives to autogenous bone grafts. In this study, porous HAP rods were treated with 1 μg or 5 μg of rhBMP-2 subperiosteally implanted on the cranial bone of rabbits. The HAP rods were then removed 3, 6, or 9 weeks after implantation and subjected to physical strength determinations. Even the control group, without addition of rhBMP-2 to the rods, demonstrated significantly increased three-point bending strength at 9 weeks compared with that before implantation. Groups receiving rhBMP-2-treated rods showed significant increases in strength beginning at 3 weeks. In histological examination, a slight degree of bone formation was seen around the HAP rods in the control group; however, clearly visible bone formation was found penetrating the rod pores of the rhBMP-2 groups. Histological examination also revealed that bone formation was inclined to be greater at the higher dose, 5 μg, of rhBMP-2. Results indicated that rhBMP-2, even in a small dose, increases the strength of porous HAP, which is basically a ceramic and thus has the characteristic disadvantage of being fragile, at a relatively early stage following implantation as the result of bone ingrowth to the pores of HAP. Received: Sept. 22, 1997 / Accepted: Nov. 6, 1997     

In vivo matrix microdamage in a naturally occurring canine fatigue fracture

Greyhound central tarsal bone (CTB) from animals with (n = 11) and without CTB fatigue fracture (n = 15) was examined histologically for the presence, numerical density, and morphology of in vivo microdamage. Complete fracture of the right CTB is a common occurrence during dog racing, because this is the outside limb when running counterclockwise on a circular or oval track. The CTB consisted of both remodeled cortical bone and inner trabecular bone. Thickening and coalescence of trabeculae were observed, particularly dorsally and medially, causing reduction or elimination of the marrow void spaces. A band of tightly packed transverse osteons was also observed adjacent to the concave proximal joint surface. Typical linear microcracks were most often seen in remodeled cortical and trabecular bone and were often observed adjacent to vascular channels. In contrast, ultra-microcracking, represented by diffuse staining with basic fuchsin, was consistently observed in the plantar process around the attachment site for the plantar ligament complex. Dog status (fractured or intact) and side (left or right) both had a significant effect on microcrack density and microcrack surface density (p < 0.05). Microcrack density and microcrack surface density were increased in the right (fractured) CTB from greyhounds with CTB fracture. There was also a trend for side to have a significant effect on microcrack length, with microcrack lengths being higher in the right CTB of both intact and fractured dogs. These data support the general hypothesis that fatigue fracture occurs because of ongoing cyclic stresses after induction of reparative remodeling. Development of methods for biomechanical testing of small cuboidal bones should allow investigation of relationships between accumulation of loading cycles and bone weakening because of microdamage.     

In vivo histological evaluation of a novel ablative fractional resurfacing device

BACKGROUND AND OBJECTIVES: A novel carbon dioxide (CO(2)) laser device employing ablative fractional resurfacing was tested on human skin in vivo for the first time. STUDY DESIGN/MATERIALS AND METHODS: An investigational 30 W, 10.6 microm CO(2) laser system was focused to a 1/e(2) spot size of 120 microm to generate an array of microscopic treatment zones (MTZ) in human forearm skin. A range of pulse energies between 5 and 40 mJ was tested and lesion dimensions were assessed histologically using hematoxylin and eosin. Wound healing of the MTZ's was assessed immediately-, 2-day, 7-day, 1-month, and 3-month post treatment. The role of heat shock proteins was examined by immunohistochemistry. RESULTS: The investigational CO(2) laser system created a microscopic pattern of ablative and thermal injury in human skin. The epidermis and part of the dermis demonstrated columns of thermal coagulation that surrounded tapering ablative zones lined by a thin eschar layer. Changing the pulse energy from 5 to 30 mJ resulted in a greater than threefold increase in lesion depth and twofold increase in width. Expression of heat shock protein (hsp)72 was detected as early as 2 days post-treatment and diminished significantly by 3 months. In contrast, increased expression of hsp47 was first detected at 7 days and persisted at 3 months post-treatment. CONCLUSION: The thermal effects of a novel investigational ablative CO(2) laser system utilizing fractional resurfacing were characterized in human forearm skin. We confirmed our previous ex vivo findings and show for the first time in-vivo, that a controlled array of microscopic treatment zones of ablation and coagulation could be deposited in human skin by varying treatment pulse energy. Immunohistochemical studies of heat shock proteins revealed a persistent collagen remodeling response lasting at least 3 months. We successfully demonstrated the first in-vivo use of ablative fractional resurfacing (AFR) treatment on human skin.     

In vivo properties of an intramedullary hydroxyapatite plug to improve femoral stem fixation

An intramedullary hydroxyapatite (HA) plug was inserted in each tibia of five rabbits. Histological observation showed the presence of newly formed bone tissue bridging between the inner cortex and the HA plug at 3 months postoperatively. This new bone was in direct contact with the HA plug, and there was no fibrous tissue intervention. Based on these results, the HA plug was used in a hip hemiarthroplasty with bone cement. The radiograph taken 4 years postoperatively showed that the plug-bone interface was indistinct, and some of the plug's edges became rounded by replacement with newly developed bone. The femoral component was stable without subsidence. The HA plug stabilized by bone ingrowth in the femoral canal would certainly be useful to prevent the femoral component from subsiding, in addition to increasing the cement-bone interface pressure at the time of surgery.     

In vivo behaviour of low-temperature calcium-deficient hydroxyapatite: comparison with deproteinised bovine bone

This study aims to evaluate in detail the biological osteoconductive properties of the low-temperature synthetic porous calcium-deficient hydroxyapatite and to compare it with the biological apatite. Bone reactions to granules of similar sizes of the low-temperature hydroxyapatite and commercially available non-sintered deproteinized bovine bone were compared. Two different temperatures were used to fabricate two batches of newly developed porous hydroxyapatite with different carbonate groups content and specific surface area. The histological analysis of specimens with histomorphometry was performed at different time after in vivo implantation. Based on histological analysis, the level of bone formation in the spaces between the implanted granules and through the interconnected pores of all implanted materials within a cortical region (bone area ingrowth 72–85 %) was several-fold higher than within a cancellous bone site (bone area ingrowth 16–28 %) at three and six months after implantation. Within the cancellous bone site, bone coverage of the implanted material at six months was significantly higher in hydroxyapatite material fabricated using low-temperature synthesis and subsequent processing at 150°C than in hydroxyapatite scaffold developed using low-temperature synthesis with subsequent processing at 700°C or deproteinized bovine bone. According to our study, the bioactive properties of the low-temperature calcium-deficient hydroxyapatite are comparable with the biological apatite. The favourable influence of a high specific surface area of a low-temperature calcium-deficient hydroxyapatite on in vivo bone formation was emphasized.     

Solitary fibrous tumor of the meninges in the posterior cranial fossa: magnetic resonance imaging and histological correlation--case report

A 58-year-old female presented with a rare case of intracranial solitary fibrous tumor (SFT) manifesting as progressive ataxic gait and hearing loss on the left persisting for 6 months with recent symptoms of increased intracranial pressure. Computed tomography demonstrated a large isodense irregular-shaped mass in the left posterior cranial fossa. T2-weighted magnetic resonance imaging showed two components appearing as very low intensity and high intensity. Extreme-lateral suboccipital craniotomy was performed. Gross total resection was achieved except for some dural attachment in the jugular foramen. All symptoms and signs subsided after surgery. Histological, immunohistochemical, and electron microscopic examinations led to a diagnosis of SFT. The strongly hypointense areas on the T2-weighted images were hypocellular region characterized by disorganized spindle cells and thick bands of collagen. The hyperintense areas on the T2-weighted images were hypercellular region mimicking hemangiopericytoma. Strong immunoreactivity for CD34 was also helpful in the diagnosis. Electron microscopy revealed absence of pinocytic vesicles and dense laminae which are characteristic of hemangiopericytoma. The magnetic resonance imaging appearance of SFT seems to be pathognomonic.     

In vivo evaluation of coralline hydroxyapatite and direct current electrical stimulation in lumbar spinal fusion.

STUDY DESIGN: An animal model of posterolateral intertransverse process lumbar spinal fusion using autologous bone, coralline hydroxyapatite, and/or direct current electrical stimulation. OBJECTIVES: To evaluate the effect of an osteoconductive bone graft substitute and direct-current electrical stimulation on the rate of pseudarthrosis in a rabbit spinal fusion model. SUMMARY OF BACKGROUND DATA: Conventional techniques for the surgical treatment of degenerative conditions in the lumbar spine have a substantial failure rate and associated morbidity. Bone graft substitutes and electrical stimulation are alternative techniques to enhance fusion rates and limit the morbidity associated with posterolateral intertransverse process fusion using autologous iliac crest bone graft. METHODS: Fifty-three adult female New Zealand White rabbits underwent single-level lumbar posterolateral intertransverse process fusion. Animals were assigned to one of four groups using either autologous bone (Group I), coralline hydroxyapatite with autologous bone marrow aspirate (Group II), coralline hydroxyapatite with a 40-microA implantable direct current electrical stimulator and bone marrow aspirate (Group III), or coralline hydroxyapatite with a 100-microA implantable direct current electrical stimulator and bone marrow aspirate (Group IV). Animals were killed at 8 weeks, and fused motion segments were subjected to manual palpation, mechanical testing, and radiographic and histologic analysis to assess the fusion mass. RESULTS: Successful fusion was achieved in 57% (8/14) of animals in Group I, 25% (3/12) in Group II, 50% (6/12) in Group III, and 87% (13/15) in Group IV. Mean stiffness and ultimate load to failure were significantly higher in Group IV than in all other groups (P < 0.05). Histologic analysis demonstrated a qualitative increase in fusion mass in Group IV versus all other groups. CONCLUSIONS: Direct-current electrical stimulation increased fusion rates in a dose-dependent manner in a rabbit spinal fusion model. Coralline hydroxyapatite is an osteoconductive bone graft substitute, and thus requires an osteoinductive stimulus to ensure reliable fusion rates. Furthermore, coralline hydroxyapatite and direct current electrical stimulation can be used together to increase fusion rates in a rabbit spinal fusion model while avoiding the morbidity associated with harvesting iliac crest bone.     

In vivo osteogenic capability of cultured allogeneic bone in porous hydroxyapatite: immunosuppressive and osteogenic potential of FK506 in vivo.

Fischer or ACI rat marrow cells were obtained from femoral shafts and were cultured to confluence in Eagle's minimal essential medium (EMEM) supplemented with 15% fetal bovine serum. After trypsinization, the cells were subcultured on porous hydroxyapatite (HA; Interpore 500) blocks in the presence of beta-glycerophosphate and 10 nM dexamethasone (Dex). After 2 weeks of subculture, a mineralized bone matrix with osteogenic cells developed on the HA pore surfaces. ACI or Fischer cultured bone tissue/HA constructs were implanted subcutaneously into the backs of Fischer rats and the immunosuppressant FK506 was given to the rats for 4 weeks. Implants were harvested 4 weeks and 8 weeks after insertion. At 4 weeks, the ACI constructs (allografts) showed high levels of osteogenic parameters (alkaline phosphatase [ALP] activity and osteocalcin content) and bone formation was observed together with active osteoblasts without obvious accumulation of inflammatory cells. At 8 weeks, active osteoblasts and progressive bone formation were still observed, while osteogenic parameters remained high and osteocalcin messenger RNA (mRNA) was detected. Without FK506 administration, the allografts showed neither bone formation nor osteocalcin mRNA and there were only trace levels of the osteogenic parameters. In the case of Fischer constructs (isografts), extensive bone formation was detected and all the osteogenic parameters were higher with FK506 than without FK506 at both 4 weeks and 8 weeks. These results indicate that cultured bone tissue/HA constructs possess a high osteogenic potential, even as allografts, and that FK506 not only has an immunosuppressive action, but also promotes bone formation.     

载银羟基磷灰石抗菌涂层螺钉体内抗菌及成骨性能的实验研究

目的采用银(Ag)作为抗菌剂制备羟基磷灰石(hydroxyapatite,HA)/Ag抗菌涂层,初步探讨其体内抗菌及成骨性能。方法采用真空等离子体喷涂技术在不锈钢外固定螺钉表面制备HA及HA/Ag抗菌涂层(Ag质量百分比为3%)。取成年雄性比格犬18只,体重15～20 kg,制备犬右后肢胫骨骨折模型。根据植入螺钉不同分为两组,分别于胫骨截骨平面远端植入HA/Ag涂层螺钉2枚(实验组,n=18),近端植入HA涂层螺钉2枚(对照组,n=18)。以金黄色葡萄球菌沾染螺钉伤口,通过伤口分级、X线片观察及硬组织切片染色观察钉道感染及涂层螺钉-骨界面情况。结果对照组伤口随时间延长感染程度加重(χ2=13.492,P=0.001),实验组无明显变化(χ2=0.208,P=0.901);术后1、2、3周实验组伤口分级情况均优于对照组,差异均有统计学意义(P<0.05)。术后3周激光扫描共聚焦显微镜观察示,两组涂层螺钉表面均有细菌黏附,对照组以绿色活细菌为主,实验组以红色死细菌为主。术后6周硬组织切片扫描电镜观察,对照组涂层螺钉与骨组织之间形成一明显透明带,实验组涂层螺钉与骨组织之间无明显间隙。对照组和实验组骨结合率分别为76.23%±15.54%和93.42%±5.53%,比较差异有统计学意义(t=8.843,P=0.000)。扫描电镜观察示实验组涂层与骨组织间结合紧密,对照组涂层与骨组织间存有明显空隙。结论 HA/Ag涂层螺钉具有良好的抗菌及成骨性能,能起到预防外固定支架螺钉钉道感染和松动的作用。     

Vestibular schwannoma and tuberculoma occurring In collision in the posterior fossa: A case report

IntroductionThough acoustic schwannoma is the most common primary tumour in the cerebello-pontine angle, its occurrence with tuberculoma has never been reported.Presentation of caseA case of a vestibular schwannoma and tuberculoma occurring as collision tumors in the posterior fossa in a 46 years old female is reported. She presented with chronic raised intracranial pressure manifesting as headache, occasional diplopia, speech disturbance, and unsteady gait. Magnetic resonance imaging of the brain demonstrated a vestibular schwannoma and tuberculoma in the right cerebello-pontine angle. The lesions were resected through retro sigmoid route. The caudal mass was vestibular schwannoma while the rostral and medial portion was tuberculoma.DiscussionThe occurrence of a vestibular schwannoma and tuberculoma in collision has hitherto never been reported. The pathogenesis, surgical challenges and management of such a rare entity is discussed and the relevant literature is briefly reviewed.ConclusionThe association of vestibular schwannoma and tuberculoma is rare. Surgical excision of lesions occurring in collision can be formidable. They require careful planning and strategy.     

In vivo 31P NMR spectroscopic changes during liver regeneration

Liver regeneration following partial hepatectomy involves rapid cell division 24 to 72 hr postresection. This cell division would necessarily involve changes in intracellular energy stores and cell membrane phospholipid precursors. In tumor models 31P nuclear magnetic resonance (NMR) has been shown to identify intracellular substrate changes associated with cell growth. The ability to monitor early changes in adenosine triphosphate (ATP), inorganic orthophosphate (Pi), phosphomonoesters (PME), or phosphodiesters (PDE) after liver resection could indicate the intracellular changes necessary for hepatocellular regeneration. In vivo 31P NMR scans of the liver were performed in both normal rats and in rats at 24, 48, 72, and 120 hr after 70% hepatectomy. At 48 hr, total ATP fell to 18.9% (P less than 0.05) and both Pi/beta-ATP and PME/beta-ATP were significantly elevated (P less than 0.01) from controls. These changes correlate with the known mitotic peak in the rat following hepatectomy. We conclude that in vivo 31P NMR is a potentially valuable tool for studying hepatic regeneration. The data also suggest that hepatocellular regeneration may be critically dependent on cellular ATP stores.     

Age-related histological changes in rat mandibular condyle

The effect of aging on rat mandibular condyle was histologically assessed using 1-, 4-, 9-, and 16-month-old male Fischer rats (Eight rats of each group). The medial and anterior portions of the condyle protruded with age. The hypertrophic cell layer of the condylar cartilage occurring up to 4 months was no longer observable at 9 months, after which calcification of the cartilage layer with a tidemark was featured. The chondrocytes in the calcified cartilage layer were reduced in size and intensely stained by toluidine blue. A mineralizing front was formed parallel to, and migrated toward, the condyle surface. At 9 months, osteon-like osteogenesis occurred around blood vessels on the border between the calcified cartilage and the subchondral bone. Condyles of 16-month-old rats exhibited osteosclerotic changes. The calcified cartilage of the middle portion of the condyle formed a remarkably thick layer. The increased volume of the trabecular bone appears to lead to enhanced osteosclerotic changes of the condyle. The aging-related protrusion of the anterior and medial portions of the condyle could be the result of a combination of mechanical forces, e.g., occlusion and mastication. Further, our study revealed that the turnover from cartilage to bone occurring in rat condyle through the process of aging involved an osteon-like bone formation around the blood vessels on the border between the calcified cartilage layer and the bone. This process differs from the endochondral ossification process observed in younger rats.     

In vivo study of age-related changes in the optical properties of the skin

The optical properties of the skin (absorption coefficient, scattering coefficient, refractive index) may serve to characterize the skin and are important for correct light dosimetry in many optical diagnostic procedures and laser treatments especially photodynamic therapy and laser therapy. We determined in vivo the optical properties of tissues near the wrist, elbow and knee in subjects of different ages using diffuse reflectance spectroscopy, having in view the establishment of laser system types for the laser treatment of posttraumatic lesions in subjects of different ages. Diffuse reflection of light from biological tissue is due to the variation in refractive index of tissular and cellular components and the surrounding medium and depends on the wavelength of the incident optical radiation. The diffuse reflectance spectrum of the tissues tested showed two maxima localized at λ_M1 ≈ 610 nm and λ_M2 ≈ 675 nm. Laser systems which emit radiation at these wavelengths are not efficient for the treatment of joints, regardless of the subject’s age. The deep tissues have a strong absorption in the range 630–700 nm, which indicates that for treating posttraumatic lesions we can use laser systems such as the He–Ne laser, the GaAlAs laser, and the InGaAlAs laser. Using Kramers-Kronig analysis of the diffuse reflectance spectra, the optical parameters n(ω) and k(ω) were determined. The age-dependent changes in these optical parameters of tissue must be taken into consideration and the use of laser treatments or optical diagnosis methods must be based on a knowledge of these properties and of the optical radiation parameters.