Fibrous Tissue Invasion Research Articles

Bone augmentation using bioresorbable mesh domes containing bone graft granules

Bone graft granules are valuable tools for ridge area bone grafting owing to their ease of manipulation and interconnected porous structure. Guided bone regeneration (GBR) using barrier membranes is commonly used for alveolar ridge augmentation; however, the surgical procedures are technically complicated. In this study, we fabricated bioresorbable mesh domes (BMDs) using two types of Vicryl mesh (woven and knitted types) containing carbonate apatite granules. BMD samples were prepared in three groups: upper sides made from the woven type (UW) and lower sides made from the woven type (LW) (the UW/LW group), upper sides made from the woven type (UW) and lower sides made from the knitted type (LK) (the UW/LK group), and upper sides made from the knitted type (UK) and lower sides made from the knitted type (LK) (the UK/LK group). The samples were subsequently implanted into rabbit calvaria, and radiomorphometric and histological analyses were conducted. The UK/LK group exhibited enhanced appositional bone formation because the knitted mesh on the skin side prevented the infiltration of a substantial amount of fibrous tissue. This increase in bone formation could be attributed to the interaction between granules and osteoprogenitors that pass through the mesh from the host bone. Conversely, the UW/LW and UW/LK groups presented limited appositional bone formation. Compared with knitted mesh, woven mesh might tend to be absorbed over a short span, allowing fibrous tissue invasion and inhibiting new bone formation. Additionally, BMDs could retain granules in a targeted location and avoid displacement of the granules to unintended locations.Graphical

Pharmacotherapy review and clinical, sub-clinical characteristics in limb-girdle muscular dystrophy

Aims: Review pharmacotherapy in limb-girdle muscular dystrophy and describe clinical, and subclinical characteristics in patients of limb-girdle muscular dystrophy (LGMD). Methods: A meta-analysis with data in PubMed, up to May 2023 on the pharmacotherapy of LGMD combined with a cross-sectional study. Patients were diagnosed with LGMD according to the European Neuromuscular Centre (ENMC) in 1995 at E and Bach Mai Hospitals, from December 2022 to May 2023. Results: 21 studies in pharmacotherapy were conducted, and treatment therapies (glucocorticoid, biological antibody, gene therapy) initially showed safety and some effectiveness in muscular strength. There are some potential gene therapies. The clinical characteristic of collected 15 patients with LGMD was high onset age (20.7±12.5 years), and prolonged diagnosis time (6.3±5.5 years). Most patients showed signs of muscle weakness and muscle atrophy (100 and 86.7%), waddling gait, and Gower’s sign (93.3%). 100% of patients had increased creatine kinase (CK) of 1648.5±2235.8 U/l. Most patients had normal inflammatory indexes. On muscular histopathology, the majority of patients had muscle fiber degeneration, hypertrophy, fibrous tissue invasion, and fat infiltration (86.7%). Conclusions: Treatment therapies in LGMD initially showed safety and some effectiveness in muscular strength; the gene therapies are promising. Clinically, all patients showed signs of muscle weakness in the limb-girdle, most of them showed muscle atrophy, waddling gait, Gowers’ sign, increased CK, negative inflammatory markers, and muscle fiber degeneration on histopathology.

Roles of pore architecture of artificial bone grafts in invasion competition between bone and fibrous tissue and orientation of regenerated bone

 In the reconstruction of bone defects close to soft tissue, preventing the invasion of fibrous tissue into the bone defect is key to successful bone reconstruction. In this study, we clarified the effects of the pore architecture of artificial bone grafts on the penetration of bone and fibrous tissue, and the orientation of regenerated bone. Carbonate apatite grafts with uniaxial pores along the long- (L-graft) or short-axis (S-graft) direction of the graft and biaxial pores along the long- and short-axes (LS-graft) were used. These grafts were implanted in bone defects created by rabbit ulnae amputation. The pores of the L-, S-, and LS-grafts opened into the bone stumps, muscles, and bone stumps and muscles together, respectively. In the L-graft, the graft pores developed bone from the bone stump to the graft center, while preventing excessive invasion of fibrous tissue. In S- and LS-grafts, the graft pores along the short axis allowed the invasion of fibrous tissue into the grafts. Consequently, although the bone grew to the edge regions in these grafts, further bone ingrowth was inhibited by the fibrous tissue. Furthermore, the pore architecture of the grafts affected the orientation of the regenerated bone. The degree of orientation of the bone formed in the L- and S-grafts was 1.6-fold higher than that formed in the LS-grafts. Thus, controlling the pore architecture allowed the growth of bone to predominate over that of fibrous tissue and induced the formation of bone with an ordered orientation

Customized reconstruction of alveolar cleft by high mechanically stable bioactive ceramic scaffolds fabricated by digital light processing

Due to the personalized large defect and bone absorption of the alveolar cleft, its regeneration is still a great challenge. Conventional autologous bone repair leads to donor site adverse reactions and then bioactive materials with stable mechanical properties, suitable degradation rates, good osteogenic ability are required. In this study, the α-tricalcium phosphate (doping with and without 6% strontium; α-TCP-Sr6, α-TCP) bioceramic scaffolds with high-precision pore structure were developed to repair the alveolar cleft, and the physicochemical properties and bone repair performances were systematically compared with the pure β phase of tricalcium phosphate (β-TCP) bioceramic scaffolds.It was shown that Sr dopant could adjust the bio-dissolution of α-TCP scaffolds, and contributed to excellent mechanical stability. As for the osteogenic capability in the alveolar cleft of rabbits, the α-phase TCP scaffolds both exhibited appreciable new bone ingrowth compared to the β-TCP scaffolds.However, bone malformation and fibrous tissue invasion occurred in the control group (without filling scaffolds). This study suggests that the Sr dopant may adjust the biodegradation and mechanical stability of α-TCP, and such biodegradable Ca-phosphate bioceramics scaffolds prepared by digital light processing (DLP)-based 3D printing technique demonstrate significance in promoting the reconstruction of the alveolar cleft.

Porous PLGA-PEG nerve conduit decorated with oriented electrospun chitosan-RGD nanofibre

Chitosan (CS) is a type of natural polysaccharide, widely used as a biomaterial on account of its great biocompatibility and the multitudes of functional groups on the long chitosan chain, making it easy for property augmentations. Nevertheless, the lack of workability and mechanical capacity limits the applications. Herein, electrospinning was chosen to fabricate oriented chitosan/polyethylene oxide (PEO) nanofibres decorated by integrin-targeting polypeptides (RGD, Arg-Gly-Asp), which is essential for cell adhesion. At the same time, porous PLGA-PEG membranes were taken as a shell of the composite film, which can provide mechanical support for the scaffold. Adequate topological anisotropic information from oriented nanofibres helps the scaffold simulate the natural axon structure, which can induce accelerated regeneration of neurotmesis. Moreover, β-Tricalcium Phosphate (β-TCP) nanoparticles were brought into nanofibers to neutralize the acidic environment produced by the degeneration of PLGA-PEG. Cell viability tests at the in vitro level and dorsal root ganglion (DRG, 1-day sucking SD rat) co-culture detection proved that the scaffold possesses excellent biocompatibility while guiding oriented regeneration of damaged nerves. In this study, a CS-RGD/PEO/β-TCP/PLGA-PEG porous composite scaffold with low cytotoxicity was fabricated. The scaffold can not only lead to the oriented growth of nerves but also has selectivity, which can help nutrient exchange while inhibiting the invasion of fibrous tissue.

Cell Adherence Competition between Osteoblasts and Fibroblasts on Various Materials Influences the Establishment of Osseointegration

Osseointegration is a key factor in determining the success of a prosthetic implant. Titanium and its alloys are widely used as implantable materials because of good adaptation and connection to bone tissues, known as osseointegration. We focused on the invasion of fibrous tissue into the bone tissue–material interface and hypothesized that there might be competition for cell adhesion between osteoblasts and fibroblasts on the material surface. In this study, we established a cell competition model in a co-culture of osteoblasts and fibroblasts under shear stress conditions to elucidate fibroblast-associated failure of osseointegration after implantation. The osteoblasts adhere better on titanium than fibroblasts under shear stress conditions. The alkaline phosphatase–positive cells were increased when osteoblasts were co-cultured with fibroblasts, suggesting that the small population of fibroblasts promotes osteoblast differentiation through the production of extracellular matrices including type I collagen. Cell adhesion competition created a balance of osteoblasts and fibroblasts on the implant material surface in the initial stage of osseointegration resulting in a high osseointegration ratio. These results show that fibroblasts are able to both inhibit osseointegration and help adhesion and differentiation of osteoblasts by producing type I collagen.

The controlled design of electrospun PCL/silk/quercetin fibrous tubular scaffold using a modified wound coil collector and L-shaped ground design for neural repair

Asymmetrically porous and aligned fibrous tubular conduit with selective permeability as a biomimetic neural scaffold was manufactured using polycaprolactone (PCL), silk, and quercetin by a modified electrospinning method. The outer surface of the randomly oriented fibrous scaffold had microscale pores that could prevent fibrous tissue invasion (FTI), but could permeate neurotrophic factors, nutrients, and oxygen. The inner surface of the aligned fibrous scaffold can be favorable for neurite outgrowth, because of their superior neural cell attachment, migration, and directional growth. In vitro and in vivo studies have demonstrated the therapeutic effect of Quercetin, a ubiquitous flavonoid widely distributed in plants, on neuropathy, by modulating the expression of NRF-2-dependent antioxidant responsive elements. In this study, the controlled inner and outer surface geometry of the 0.5, 1.0, and 2.0wt% quercetin-containing electrospun PCL/silk fibrous tubular scaffold fabricated via a modified wound coil collector and L-shaped ground design (WCC-LG) was characterized by FE-SEM, TEM, FFT, FT-IR, and XRD. In addition, two types of neural cell lines, PC12 and S42, were used to evaluate the cell proliferation rate of the different amount of quercetin-loaded PCL/silk tubular scaffolds.

Induced-Membrane Technique in the Management of Posttraumatic Bone Defects.

Critical-size bone defects are defined as bone defects where spontaneous regeneration is not expected without treatment1. The characteristics of bone defects (etiology, location, size, presence of infection, and soft-tissue conditions) vary greatly and, to be effective, the treatment method should address this variability. The induced-membrane technique, or Masquelet technique, is a method for treating critical-size bone defects2,3 of various sizes and anatomic locations. It has been used to treat infected and noninfected bone defects and may be performed with a variety of fixation methods2,3. The induced-membrane technique is a 2-stage procedure. The first stage consists of debridement followed by insertion of a polymethylmethacrylate (PMMA) spacer in the bone defect. The presence of the PMMA leads to a foreign-body reaction with the development of a thick pseudosynovial membrane that is extremely vascularized and rich in growth factors. The filling of the bone defect with the cement spacer prevents fibrous tissue invasion and allows the development of an optimal vascularized gap for bone-grafting. After 6 to 8 weeks, the membrane around the spacer is carefully opened for the removal of the spacer, which is then replaced by bone graft2,3, which can be expanded with allograft or biomaterials. Alternatives include vascularized or nonvascularized autologous bone graft, allograft, bone transport methods, titanium cages, megaprostheses, shortening, and amputation. Posttraumatic bone defects frequently are associated with soft-tissue injury and infection that impair the local vascularization and the healing potential. The highly vascularized induced membrane may play a role in restoring the local regenerative capacity. Numerous studies have demonstrated its successful use in the treatment of posttraumatic bone defects in the hand, forearm, humerus, femur, tibia, and foot. The induced-membrane technique is especially advantageous in the treatment of infected bone defects because the presence of the spacer helps in the treatment of the infection by reducing dead space, acting as a local antibiotic carrier, and promoting some degree of bone stability3-5.

Dual growth factor-immobilized asymmetrically porous membrane for bone-to-tendon interface regeneration on rat patellar tendon avulsion model.

Insufficient repair of the bone-to-tendon interface (BTI) with structural/compositional gradients has been a significant challenge in orthopedics. In this study, dual growth factor (platelet-derived growth factor-BB [PDGF-BB] and bone morphogenetic protein-2 [BMP-2])-immobilized polycaprolactone (PCL)/Pluronic F127 asymmetrically porous membrane was fabricated to estimate its feasibility as a potential strategy for effective regeneration of BTI injury. The growth factors immobilized (via heparin-intermediated interactions) on the membrane were continuously released for up to ∼80% of the initial loading amount after 5 weeks without a significant initial burst. From the in vivo animal study using a rat patellar tendon avulsion model, it was observed that the PDGF-BB/BMP-2-immobilized membrane accelerates the regeneration of the BTI injury, probably because of the continuous release of both growth factors (biological stimuli) and their complementary effect to create a multiphasic structure (bone, fibrocartilage, and tendon) like a native structure, as well as the role of the asymmetrically porous membrane as a physical barrier (nanopore side; prevention of fibrous tissue invasion into the defect site) and scaffold (micropore side; guidance for tissue regeneration). © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 115-125, 2018.

Hydroxyapatite/β-tricalcium phosphate composite for guiding bone tissue growth into a titanium tube in 8 mm dog tibia cavity defects

We developed a fixation method and evaluate bone regrowth in the cavities of a ϕ4 mm× 8 mm titanium (Ti) tube through porous hydroxyapatite (HAP)/β-tricalcium phosphate (β-TCP) composite filling (group A), chitosan/calcium phosphate composite filling (group B), and HAP particle modification (group C). After 2 and 5 months of implantation in dog tibia defects, new bone formation in the three groups was studied by histology and histomorphometry. Group A displayed the most bone regenerated area in both 2 and 5 months post-operation. The chitosan/calcium phosphate composite in group B mostly degraded 2 months after implantation, leading to fibrous tissue invasion after 5 months. By contrast, less bone formation was observed in group C. These results indicated that filling the cavities of metal prostheses with a porous HAP/β-TCP composite can be used for stable long-term fixation in clinical settings.

Peroneal Nerve Regeneration Using a Unique Bilayer Polyurethane-collagen Guide Conduit

Unique double layer polyurethane (PU)-collagen nerve guide conduits with desirable biocompatibility and mechanical properties were fabricated using a newly developed double-nozzle low-temperature deposition manufacturing (DLDM) technique. The inner collagen layer of the conduit had oriented nano-size filaments with micro-pores (pore size 20—100μm) that permitted nutrient infiltration, while the outer PU layer had micro-pores (pore size 15—20 μm) preventing fibrous tissue invasion. In vivo animal tests (n = 6) on bridging a 10 mm long peroneal nerve defect was conducted using rats. Single layer pure PU conduit (n = 6) was used as the positive control and the same size defect with no implantation (n = 2) as the negative control. Through walk track analysis as well as electrophysiological and histological evaluations of the regenerated nerves, the double layer PU-collagen conduit demonstrated better nerve repair than the controls. This new PU-collagen has the potential for significant clinical applications in peripheral nerve repair.

Unusual recurrent orbital tumour

Abstract Purpose: We present a case of an unusual CD34+ recurrent orbital tumour. Methods: A 62‐year‐old male presented with progressive left proptosis and preserved visual acuity. CT scans showed a circumscribed mass at the inferomedial orbit. After incisional biopsy, the patient preferred conservative treatment and the lesion was debulked. Further debulking was necessary in other two occasions. With radiological signs of bone invasion, left orbital exenteration was agreed in the fourth relapse. Results: The lid skin sparing exenteration revealed a tumour mass (45 x 29 x 27 mm) in the inferomedial orbit. There was no evidence of invasion of either the globe or the optic nerve. In all occasions, the tumour consisted of spindle cells alternating vague storiform areas with patternless areas. The tumour was very cellular, showed low mitotic count and no necrosis or ulceration. There was focal invasion of fibrous tissue, extra‐ocular muscle, fat and bony fragments. The tumour was diffusely and consistently positive for CD34, S100 and vimentin. EMA and CD99 were focally positive. Several other markers were negative. This slow growing lesion with low grade histological appearance and EM suggestive of Schwannian processes was diagnosed as a CD34 positive Schwannoma on the first debulking. In the next two recurrences, experts agreed with a diagnosis of a DFSP based on the diffuse positivity for CD34. In the exenteration specimen, due to the exceptional location of the presumable DFSP, this diagnosis was disputed and after EM and further reviews the case was concluded as variant of low grade MPNST. Conclusions: The consistent positivity for CD34 in our case has lead to diagnostic disagreement. Only after the fourth recurrence the final diagnosis of a CD34 positive low grade PNST could be made.

Osseointegration on metallic implant surfaces: effects of microgeometry and growth factor treatment.

Orthopedic implants often loosen due to the invasion of fibrous tissue. The aim of this study was to devise a novel implant surface that would speed healing adjacent to the surface, and create a stable interface for bone integration, by using a chemoattractant for bone precursor cells, and by controlling tissue migration at implant surfaces via specific surface microgeometry design. Experimental surfaces were tested in a canine implantable chamber that simulates the intramedullary bone response around total joint implants. Titanium and alloy surfaces were prepared with specific microgeometries, designed to optimize tissue attachment and control fibrous encapsulation. TGF beta, a mitogen and chemoattractant (Hunziker EB, Rosenberg LC. J Bone Joint Surg Am 1996;78:721-733) for osteoprogenitor cells, was used to recruit progenitor cells to the implant surface and to enhance their proliferation. Calcium sulfate hemihydrate (CS) was the delivery vehicle for TGF beta; CS resorbs rapidly and appears to be osteoconductive. Animals were sacrificed at 6 and 12 weeks postoperatively. Results indicated that TGFbeta can be reliably released in an active form from a calcium sulfate carrier in vivo. The growth factor had a significant effect on bone ingrowth into implant channels at an early time period, although this effect was not seen with higher doses at later periods. Adjustment of dosage should render TGF beta more potent at later time periods. Calcium sulfate treatment without TGF beta resulted in a significant increase in bone ingrowth throughout the 12-week time period studied. Bone response to the microgrooved surfaces was dramatic, causing greater ingrowth in 9 of the 12 experimental conditions. Microgrooves also enhanced the mechanical strength of CS-coated specimens. The grooved surface was able to control the direction of ingrowth. This surface treatment may result in a clinically valuable implant design to induce rapid ingrowth and a strong bone-implant interface, contributing to implant longevity.

Expanded polytetrafluoroethylene membrane for the prevention of peridural fibrosis after spinal surgery: an experimental study.

One of the most common complications of lumbar spine surgery is peridural fibrosis, a fibroblastic invasion of the nerve roots and the peridural sac exposed at operation. Peridural fibrosis may produce symptoms similar to those the patient experienced preoperatively and, if another spinal operation is necessary, may increase the risk of injury at reexposure. In a controlled study in dogs, we assessed the use of expanded polytetrafluoroethylene (ePTFE) as a barrier to postoperative invasion of fibrous tissue into the laminectomy defect. In 14 dogs, a two-level laminectomy was done, at L4-L5 and L6-L7. In 12 dogs, an ePTFE membrane was placed directly over the dorsal surface of the laminectomy defect at L4-L5 and within the defect (over the surface of the dura) at L6-L7. No material was implanted in two dogs (controls). Tissue for histologic studies was obtained from the controls and from ten dogs with the membrane 12 weeks postoperatively. Two dogs with the membrane underwent reoperation. The study found that there was no peridural fibrosis in seven of the ten specimens in which the ePTFE membrane had been placed directly on the dorsal surface of the laminectomy defect, some peridural fibrosis in all specimens in which the membrane had been placed within the defect, and extensive fibrosis in controls. The ePTFE membrane created an excellent plane of dissection for reoperation. No foreign-body reactions to the membrane or membrane-related infections occurred. We conclude that the ePTFE spinal membrane, when properly implanted, is an effective barrier to postsurgical fibrous invasion of the vertebral canal. Clinical studies of use of this material in spinal surgery are warranted.

Expanded polytetrafluoroethylene membrane for the prevention of peridural fibrosis after spinal surgery: a clinical study

Peridural fibrosis developing after laminectomy may cause pain that can necessitate reoperation. Many materials have been used as a barrier to invasion of fibrous tissue into the vertebral canal, but the ideal material has not been found. Various studies in animals have achieved favourable results with an expanded polytetrafluoroethylene (ePTFE) membrane. In a prospective, randomized study, we compared postoperative results in 33 patients who had an ePTFE membrane implanted to cover the defect caused by laminectomy during lumbar spine decompression with the results in 33 patients in whom no material was implanted. At operation, an ePTFE membrane was placed after the decompression procedure to cover the laminectomy defect completely. Systematic clinical and MRI follow-up evaluations of patients with and without the membrane were conducted 3, 6, 12, and 24 months postoperatively. The effect of ePTFE membrane implantation over laminectomy sites on postoperative peridural fibrosis, pain and neurological claudication was assessed. The ePTFE-membrane group had a significantly lower rate of epidural fibrosis on MRI (P<0.0001) and of clinical manifestations of radiculalgia (P = 0.002) compared with the no-material group. Epidural fibrosis that occurred in the ePTFE group was generally less extensive than that in the no-material group. There was no significant difference in the rate of postoperative claudication in the two groups. Significantly more seromas occurred in the ePTFE group (P = 0.0002). There were no infections or other complications in either group. The results showed that placement of an ePTFE spinal membrane over the laminectomy defect produced by lumbar spine surgery provided a physical barrier to invasion of fibrous tissue into the vertebral canal, and patients with the membrane had less postoperative radicular pain.

Late enlargement of radiofrequency lesions in infant lambs. Implications for ablation procedures in small children.

Despite the current clinical use of radiofrequency (RF) catheter ablation in infants, the acute and late effects of RF lesion production in immature myocardium remain unknown. This study was specifically designed to investigate the pathology of RF lesions in developing sheep myocardium. In study 1, RF lesions were made on the epicardial left ventricular surface of the beating heart in 15 sheep, 5 approximately 4 weeks of age (11.0 +/- 1.0 kg) and 10 approximately 8 weeks of age (23.8 +/- 3.4 kg), to assess the effects of RF application duration (10 to 90 seconds) and electrode tip temperature (45 degrees to 90 degrees C) on lesion size in immature myocardium. Lesion width and depth increased asymptotically with RF duration, to 7.0 +/- 0.7 and 4.8 +/- 1.0 mm at 90 seconds, respectively. The time to reach one-half lesion size was 6.5 seconds for width and 12.0 seconds for depth. Lesion width increased nearly linearly with tip temperature above 50 degrees C, but depth followed a sigmoid relation, with no increase above 80 degrees C. In study 2, RF lesions were made in all four cardiac chambers under fluoroscopic guidance in 19 infant sheep (10.9 +/- 1.4 kg). Lesion sizes and histological characteristics were assessed acutely (acute, n = 5), at 1.07 +/- 0.02 months (1 month, n = 5), and at 8.5 +/- 0.5 months (late, n = 9). Atrial and ventricular lesions but not atrioventricular groove lesions apparently increased in size during the follow-up period. Atrial lesions width increased from 5.3 +/- 0.5 to 8.7 +/- 0.7 mm at 1 month (164%) but did not increase further at late follow-up, while ventricular lesion width increased from 5.9 +/- 0.8 to 10.1 +/- 0.7 mm (171%) at late follow-up but was not significantly changed at 1 month. Histological evaluation revealed replacement of normal myocytes with fibrous and elastic tissue at 1 month and late follow-up in all locations but also demonstrated a poorly delineated border with multiple extensions of fibrous and elastic tissue into surrounding normal myocardium in late ventricular lesions. RF lesion formation in immature sheep myocardium is similar to that in adult myocardium acutely but is associated with late lesion enlargement and fibrous tissue invasion of normal myocardium. These findings may have implications for clinical RF ablation procedures in infants.

Tendon Insertions Onto Allografts Pretreated With Heat and/or Bone Surface Demineralization

Tendon insertions onto allogeneic bone grafts were studied histologically and biomechanically in 132 rats. Before grafting, allogeneic bone was treated at different temperatures or partially demineralized or both. Mesenchymal cell and fibrous tissue invasion were easily recognized in non-heat-treated allograft groups and in groups with allografts incubated at 70 degrees; invasion was not observed in autoclaved (130 degrees) allograft groups. New bone formations were found between the tendon and the surface-demineralized allografts in the non-heat-treated and 70 degrees-treated bone groups but not in the autoclaved group. Allografts pretreated with heat demonstrated graft-insertion tensile strengths lower than in non-heat-treated and 70 degrees-treated allografts. Surface-demineralization enhanced graft-insertion tensile strengths in the non-heat-treated and 70 degrees-treated groups, whereas the tensile strength of attachments in noninductive, autoclaved allografts was not enhanced.

Replacement of the rabbit medial meniscus with a polyester-carbon fibre bioprosthesis

Eighteen New Zealand white rabbits underwent prosthetic replacement of the meniscus which was attached to the intercondylar area of the tibia through a predrilled hole and around the internal surface of the capsule by sutures, in one knee, and meniscectomy alone in the contralateral knee. The animals were killed 3 and 6 month after implantation. Fragmentation of carbon fibres was noted in six knee joints. Histological sections demonstrated more progressive articular cartilage degeneration of the tibial surface which had the meniscus removed alone ( P = 0.05). The implant was incorporated into the capsule with minimal invasion of fibrous tissue into the interstices of the prosthesis. Scanning electron microscopy revealed the extent of articular cartilage fibrillation which was more evident in the area where the meniscus covered the tibia.

Structural Changes in Thoracolumbar Disks Following Lateral Fenestration A Study of the Radiographic, Histologic, and Histochemical Changes in the Chondrodystrophoid Dog

Lateral fenestrations of intervertebral disks T12–13 through L2–3 were performed on 16 1‐year‐old chondrodystrophoid dogs. The disks of five dogs were fenestrated by removing the core of disk material with a 20 gauge spinal needle, six were fenestrated in the same manner with a 14 gauge spinal needle, and five were fenestrated with a 14 gauge spinal needle and a tartar scraper. Forty‐two of 48 disks had radiographic evidence of narrowing following surgery. Microscopic examination of the disks indicated that the nucleus pulposus was nonreactive tissue and that fenestration did not incite an inflammatory response that resulted in dissolution of the nucleus pulposus. Results of histochemical analyses of the fenestrated disks were not different from those of control disks. The only effects observed during a 24 week period following fenestration were disruption of the annulus fibrosus and nucleus pulposus by the fenestration device, removal of varying amounts of the nucleus pulposus, and vascular and fibrous tissue invasion of the lateral annulus fibrosus. These findings suggest that the effectiveness of fenestration is governed by the amount of nucleus pulposus removed.

Induction of Intestinal Carcinoma in the Rat by X-Irradiation of the Small Intestine

The exteriorized ileum and jejunum of maie Holtzman rats were x irradiated with doses from 1000 to 2500 r. The superior mesenteric artery and vein were clamped during radiation exposure in about haif of the irradiated animals. Thirty-day survival and appearance of intestinal tumors in the 12 months post-irradiation were noted. Per cent survival at 30 days was increased by the blood restriction procedure in all cases where there was some mortality due to irradiation alone. Over 50% of the irradiated animals that survived exposure doses above 1400 r because of the clamping procedure developed intestinal tumors. Radiation alone induced the neoplasm in only the 1400-r group. Tumors appeared as early as 55 days and as late as 225 days postirradiation. Animals without surgery or irradiation and those subjected to the intestinal vessel clamping procedure alone did not develop tumors. The neoplasm has features of adenocarcinoma including invasion of submucosal and muscle layers of the gut, but the possibility that the apparent invasion of fibrous tissue by epithelium is due to trapping of epithelium still exists in some animals. Glandular epithelium in the diaphragm of one rat with an intestinal tumor and apparent neoplastic glands in the gut mesentery ofmore » another was found. There is little, if any, doubt that these represent metastases. It was not possible to transplant the tumor into normal animals. (auth)« less