Histological demonstration of healing in experimental aneurysms.

INTRODUCTION: Recanalisation of aneurysms after interventional therapy is still an unsolved problem. The aim of this study is to demonstrate the angiographic and histological evidence of healing after endovascular embolisation of experimental aneurysms. METHODS: We evaluated the healing reaction in experimental aneurysms treated with HydroCoils and platinum coils. After microsurgical construction of aneurysms in 24 rabbits, embolisation was performed. Four animals were sacrificed immediately after embolisation and 5 after 1 month, 3 months and 6 months, respectively, the remaining served as control group. Serial plastic-embedded ground sections of the parent arteries-aneurysm complexes were evaluated by light microscopy. RESULTS: Thrombus organisation in the aneurysms resulted in fibrovascular tissue formation between bare platinum and HydroCoils from the walls of the aneurysms towards the centre of the sac over time. In the clefts between HydroCoils only thin strands of granulation tissue were observed. From one month on, there was a neointimal layer covering the coil mass at the aneurysm orifice. CONCLUSION: Progressive occlusion by the expanding hydrogel polymers on the coils seemed to result in a durable healing reaction in the aneurismal sac in a short-term follow-up period.

Retrieval analyses of highly cross-linked polyethylene acetabular liners four and five years after implantation.

Two Durasul highly crosslinked polyethylene liners were exchanged during revision surgery four and five years after implantation, respectively. The retrieved liners were evaluated macroscopically and surface analysis was performed using optical and electron microscopy. A sample of each liner was used to determine the oxidation of the material by Fourier transform infrared spectroscopy. Samples of the capsule were examined histologically. The annual wear rate was found to be 0.010 and 0.015 mm/year, respectively. Surface analysis showed very little loss of material caused by wear. Histological evaluation revealed a continuous neosynovial lining with single multinucleated foreign-body giant cells. Our findings showed no unexpected patterns of wear on the articulating surfaces up to five years after implantation and no obvious failure of material.

Auditory ossicle abnormalities and hearing loss in the toothless (osteopetrotic) mutation in the rat and their improvement after treatment with colony-stimulating factor-1.

Osteopetrosis describes a group of skeletal metabolic diseases of heterogeneous etiology and varied severity that produces a generalized accumulation of skeletal mass, the result of reduced bone resorption. Inherited in a variety of species including humans, the most severe forms are lethal. Among common features are progressive blindness and deafness of controversial etiologies for which there are no universally effective treatments. We have studied the auditory responsiveness and auditory ossicle quantitative histomorphology and temporal bone vasculature in the toothless (tl) rat, a lethal osteopetrotic mutation with few osteoclasts, very low bone turnover, and limited angiogenesis in the axial skeleton. Compared with normal littermates, 3-week-old mutants showed significantly reduced auditory responsiveness, a hearing loss due to abnormalities in both form and tissue composition of the stapes, and little capillary sprouting in the vascular bed of the temporal bone. Treatment of mutants with colony-stimulating factor 1 (CSF-1), known to greatly reduce sclerosis in the axial skeleton, significantly improved hearing, stapedial form and tissue composition, and angiogenesis in the temporal bone. In normal rats, the stapes consisted of 89.3% bone, 9.1% mineralized cartilage, and 0.8% porosity. In osteopetrotic rats, the stapes consisted of 48.3% bone, 35.9% mineralized cartilage, and 15.9% porosity, while after CSF-1 treatment, the bone content increased to 55.2%, cartilage was decreased to 21.7%, and porosity increased to 23.0%, respectively. This is the first demonstration of an auditory abnormality in an osteopetrotic animal mutation and shows that the hearing loss in tl rats can be significantly improved following treatment with CSF-1.

Breast irradiation following silicone gel implants.

Little information is found in the literature regarding breast irradiation in patients with reconstructed or augmented breasts. From November 1970 to October 1984, we treated ten patients with silicone gel prostheses with external radiation for recurrent disease, or as primary therapy. All patients were treated with megavoltage equipment. Technique and doses varied with the clinical situation, but generally, patients received 5000 rad in five weeks to the breast or mound with opposed tangential fields. The majority of patients had excellent cosmetic results with minimal late skin changes and no fibrosis or contracture. We conclude that, with proper surgical and radiotherapeutic techniques, good cosmetic results can be obtained in these patients, without compromising their therapy.

Experience with bioceramic implants in orthopaedic surgery.

In the period from 1974 to March 1980 bioceramic endoprostheses were implanted in 155 patients. 94 patients were suffering from degenerative hip diseases and 61 had been operated for malignant bone tumours. The majority of the total endoprostheses consisted of a ceramic socket and a metal shaft prosthesis with ceramic head attached to it. Bioceramic double-cup prostheses were implanted in 19 patients without using bone cement. Following resection of malignant bone tumours, the proximal humerus and the proximal femur were replaced by special bioceramic endoprostheses. The post-operation period after implantation has reached 70 months in the case of tumour endoprostheses (average 22 months) and up to 49 months in the case of hip joint endoprostheses (average 24 months). The analysis deals exclusively with complications specific to the ceramic material. These complications are: breakage of the ceramic head (8 X), loosening of the ceramic cup (13 X) and pseudarthrosis of the cone connection in tumour endoprostheses (9 X). Abrasion particles were found in all cases which we were able to follow up histologically.

Braided polypropylene augmentation device in reconstructive surgery of the anterior cruciate ligament: long-term clinical performance of 594 patients and short-term arthroscopic results, failure analysis by scanning electron microscopy, and synovial histomorphology.

Long-term clinical results and short-term arthroscopic and microscopic findings from two augmented reconstruction procedures for the ruptured anterior cruciate ligament are reported. The braided polypropylene ligament augmentation device (Kennedy model) was used with temporary double-end fixation in 279 patients to augment the attachment of the anterior cruciate ligament after acute proximal rupture and in 315 patients to augment a bone-tendon-bone autograft, mainly after chronic instability. Check arthroscopy was performed and the metal fixation hardware was removed after a mean of 11 months. Of the 569 patients evaluated, 101 partial or total breakages of the ligament augmentation device were found. Together with nine breakages detected late in the follow-up period, 110 (19.3%) failures were found. Most of these failures were accompanied by effusion that was immediately alleviated when the failed device was removed. No generalized synovitis was visible. Scanning electron microscopic analysis of 24 retrieved failed ligament augmentation devices showed fatigue to be the principal failure mode, together with local abrasion at the fracture. Synovial biopsies were taken during arthroscopy in 84 patients with and without ligament augmentation device-failure who had given informed consent, and histological evaluation revealed that in 21 patients, chronic but no acute synovial inflammation was found, and wear particles could be identified in foreign body cells in 17. Statistically, the presence of chronic synovitis was predicted neither by wear particles and foreign body cells nor by abrasion or fatigue failure of the ligament augmentation device. Irrespective of the failures, for which ligament augmentation device removal is recommended, in the final Orthopaedische Arbeitsgemeinschaft Knie evaluation (after a mean of 6.2 years), excellent and good clinical results were found in 83.6% of all 594 patients.

2D-finite element analyses and histomorphology of lag screws with and without a biconcave washer.

For osteosynthesis and for bone transplant fixation in particular, a lag screw with a biconcave washer, the so called "Anchor Screw" (AS) has been introduced in maxillo-facial surgery. Using 2D-finite element analysis (FEA), the v. Mises and the circumferential stresses induced in underlying bone by this AS are analysed and compared to those under a conventional lag screw. The stress distributions below the biconcave washer of the AS were correlated with histomorphological bone reactions after AS osteosynthesis in two tumor patients, retrieved 12 weeks and 19 months after tumor surgery, respectively. Depending on the thickness of cortical bone, the v. Mises stress concentrations below the biconcave washer were lower than under the head of the conventional lag screw (CLS), but with a higher stress maximum concentrated around the rim of the washer. The circumferential stresses were only half as high around the AS, and thus the deformation of bone was reduced. As predicted by FEA, histology showed microcrack formation, but then after minimal resorption, remodelling of bone below the biconcave washer. Stable osteosynthesis could be demonstrated by bony union already after 12 weeks, and, while bone remodelling continued in the healed osteotomy, it had decreased around the screws after 19 months. It can be concluded from the biomechanical principles and the histomorphological findings that the AS appears superior to the CLS.

The value of MRI in silicone granuloma of the breast.

MRI can be a valuable technique in patients with silicone-granulomas to screen for cancers which are not visible on mammography and/or sonography.

Adverse tissue reactions to wear particles from Co-alloy articulations, increased by alumina-blasting particle contamination from cementless Ti-based total hip implants. A report of seven revisions with early failure.

We revised seven alumina-blasted cementless hip prostheses (Ti-alloy stems, cp Ti threaded sockets) with low- or high-carbon Co-alloy bearings at a mean of 20.1 months after implantation because of pain and loosening. Histological examination of the retrieved periprosthetic tissues from two cases in which the implant was stable and three in which the socket was loose showed macrophages with basophilic granules containing metal and alumina wear particles and lymph-cell infiltrates. In one of the two cases of stem loosening the thickened neocapsule also contained definite lymphatic follicles and gross lymphocyte/plasma-cell infiltrates. Spectrometric determination of the concentration of elements in periprosthetic tissues from six cases was compared with that of joint capsules from five control patients undergoing primary hip surgery. In the revisions the mean concentration of implant-relevant elements was 693.85 microg/g dry tissue. In addition to Cr (15.2%), Co (4.3%), and Ti (10.3%), Al was predominant (68.1%) and all concentrations were significantly higher (p < 0.001) than those in the control tissues. The annual rates of linear wear were calculated for six implants. The mean value was 11.1 microm (heads 6.25 microm, inserts 4.82 microm). SEM/EDXA showed numerous fine scratches and deep furrows containing alumina particles in loosened sockets, and stems showed contamination with adhering or impacted alumina particles of between 2 and 50 microm in size.

Long-term results of uncemented alumina acetabular implants.

We report the clinical and tribological performance of 67 ceramic acetabular prostheses implanted between 1976 and 1979 without bone cement. They articulated with ceramic femoral heads mounted on mental femoral stems. After a mean elapsed period of 144 months, 59 sockets were radiographically stable but two showed early signs and six showed late signs of loosening. Four of the loose sockets have been revised. Histological analysis of the retrieved tissue showed a fibrous membrane around all the implants, with fibrocartilage in some. There was no bone ingrowth, and the fibrous membrane was up to 6 mm thick and infiltrated with lymphocytes, plasma cells, and macrophages. Intra- and extracellular birefringent wear particles were seen. Tribological analysis showed total wear rates in two retrieved alumina-on-alumina joints of 2.6 microns per year in a stable implant and 68 microns in a loose implant. Survival analysis showed a revision rate of 12.4% at 136 months.

Effects of drill cooling and bone structure on IMZ implant fixation.

Alternating use of the original method of internal drill cooling with manual external cooling, one IMZ implant was placed in the diaphysis (compact bone) and metaphysis (spongy bone) of the left distal tibia in each of six sheep. After polyfluorochrome sequential labeling, two animals survived for 4, 8, and 16 weeks without functional loading of the implants. The drill holes and bone-implant reactions were evaluated in undecalcified ground sections and microradiographs, using computer-aided histomorphometry. At least 30% of all drill holes were incongruent, but up to 25% of the implant surfaces had primary bone contacts. Four weeks after implantation, distinct differences in the bone reactions could be determined between the experimental conditions. After both cooling methods, osteoclastic resorption had extended up to 0.5 mm into peri-implant compact bone and up to 0.18 mm into spongy bone. Based on the percentage of newly formed bone-to-implant contacts, external cooling proved superior at all superficial drill hole levels in compact bone and in all spongy bone beds, while internal cooling was only better at the deeper drill hole levels in compact bone. After 8 and 16 weeks, peri-implant bone remodeling led to further increased new bone-implant contacts, irrespective of incongruent drill holes or cooling methods. At all time periods, abraded titanium particles were observed within interfacial foreign body cells.(ABSTRACT TRUNCATED AT 250 WORDS)

The dermis-prelaminated scapula flap for reconstructions of the hard palate and the alveolar ridge: a clinical and histologic evaluation.

Ideal reconstructions of complex defects in the midface require the restitution not only of bone and soft tissue, but also of a thin and durable lining of the oral cavity. So far, split-thickness skin grafts, intestinal grafts, and in vitro cultured mucosal grafts have been used for the reconstruction of the oral lining. The use of skin as a substitute for oral mucosa is controversial because contraction, hair growth, maceration, and dysplastic changes can occur. This clinical and histologic study was performed to evaluate the suitability of dermis as a substitute for oral lining. Twelve complex defects of the midface were reconstructed with dermis-prelaminated scapula flaps. A bony flap from the lateral border of the scapula was prepared, and osseointegrated implants were placed. The bone flap was then prelaminated with dermis and covered with a Gore-Tex membrane to prevent adhesions. The composite flap was transferred to the midface 2 to 3 months later. The oral lining of the flap was evaluated clinically and histologically at 2, 4, and 6 weeks and at 3 to 41 months after the reconstruction. In all patients, the reconstructed bone was covered with a thin and lubricated surface without hair growth. None of the patients showed any signs of maceration. Histologically, these findings corresponded to a keratinized stratified squamous epithelium with highly developed connective-tissue papillae. These features closely resemble those of the normal mucosa of the hard palate and the gingiva. Thus, dermis prelamination is an effective method for reconstructing the mucosa of the alveolar ridge and the hard palate.

[Investigation of bone growth into porous metal implants (author's transl)]. / Untersuchungen über das Einwachsen von Konchengewebe in poröse Metallimplantate.

Stainless-steel cylinders of different pore size were implanted into the tibia, and small tubes, 500 micrometers diameter, of the same material into the iliac crests of 19 rabbits. It was found that after three weeks ingrowing bone tissue anchored the cylinders if the pore size was adequate. The same applied to the tubes. A stable implantation was the prerequisite for the ingrowth of fibre-bone trabeculae. Additionally, the use of fibrinogen adhesive system seems to be advantageous for this anchorage. These results were established by mechanical tensile tests and morphological examinations.

The caudal mandibular reconstruction plate: a radiographic and histologic study of an autopsy specimen.

During autopsy, a reconstructed partial mandibular resection was recovered and subjected to histological examination. The mandible had been reconstructed 12 weeks earlier with a caudal plate and autologous cancellous bone from the iliac crest. Undecalcified microsections showed that the plate was firmly anchored by screws on both sides and on one side there was bony union. However, most of the free transplant bone had undergone 'unreplaced resorption.' Nevertheless, this method offers advantages over the conventional method of seating the plate on the buccal aspect and has interesting potential for further development.

Mandibular lengthening with an implanted motor-driven device: preliminary study in sheep.

Distraction osteogenesis with external or intraoral devices is an established method for lengthening human mandibles. In this preliminary study in three sheep a newly designed, fully implantable electromechanical device for mandibular lengthening was used. After osteotomy, the device was screw fixed to the mandible, and the power and control unit was inserted subcutaneously in the neck region. After a healing period of five days, the device was activated magnetically, allowing calibrated distraction steps of 0.04 mm/h, resulting in a total of 1.0 mm/day. Over a period of 14 days, a maximum mandibular lengthening of 13.6 mm could be achieved without transmucosal activation. Depending on stability of the screw fixation, membranous and/or cartilaginous bone formation was observed in the callus by radiological and histological evaluation. Further experimental research is ongoing to prove the clinical usefulness of this device.

Revascularized composite grafts with inserted implants for reconstructing the maxilla--improved flap design and flap prefabrication.

We present a new technique including prefabrication of a revascularized composite scapular flap that will fit a maxillary defect exactly. The method is based on careful preoperative planning using three-dimensional reconstructions of data obtained from computed tomograms and stereolithographic models. A pedicled scapular flap with a split skin graft envelope that has endosteal implants already inserted is prepared and covered by a polytetrafluoroethylene (PTFE, Goretex) membrane. After 3-4 months these prefabricated grafts are harvested, inserted into the maxillary defects, and reanastomosed to the facial vessels. Two to three weeks later, after mucosal healing, a prosthesis can be fitted on the endosteal implants. Histological evaluation of the flap shows vital bone reactions and attachment of the split skin graft.

Prosthesis-bone interface.

In this overview, which is based on selected books and reviews, the microscopic appearances of prosthesis-bone interfaces resulting from clinically relevant implantation techniques are highlighted. The following techniques are distinguished to insert and attach prostheses in the recipient bone: impaction into bone, primary mechanical interlocking, cement fixation, bone ongrowth and secondary mechanical interlocking with bioinert materials, and enhanced bone ongrowth and bone bonding to bioactive materials. The resulting typical histomorphologies of orthopedic and dental prostheses-bone interfaces are described and illustrated from the author's studies employing light, fluorescence, and backscattered electron microscopy, and corresponding microradiographs of undecalcified ground sections of bone and implants. Special emphasis is given to the mineralization-demineralization kinetics of the interfacial bone matrix interacting with specific surface reactions of some implant materials. Consequently, the distinction between bioinert and bioactive prosthetic materials is critically analyzed.

The electrochemical behavior of metallic implant materials as an indicator of their biocompatibility.

This study introduces a simple in vitro arrangement to measure current densities of implant metals. The in vivo condition of a metallic implant lying in tissues exhibiting different redox potentials is simulated in so-called straddle tests by applying a constant potential difference of 250 mV in saline containing the stable, fast-reacting redox system K4Fe(CN)6/K3Fe(CN)6. From a variety of corrosion-resistant implant metals and alloys, gold showed the highest current densities, followed by the stainless steel, the cobalt-based alloy, and the TiAIV-alloy. The pure metals titanium, niobium, and tantalum showed the lowest values. This can be explained by the stable oxide layer on these base metals, preventing an exchange of electrons and thus any redox reaction. This rating of metallic implant materials based on in vitro measurements of current densities is in good accordance with their biocompatibility rating reported from in vivo experiences. It seems that simple and cheap electrochemical tests allow an even more precise differentiation of the suitability of metallic materials for implant purposes than most of the conventional implantation tests, considering that biocompatibility is not only determined by corrosion products, but also by exchange currents and reaction products of redox processes involving tissue compounds.

Detection of aluminum oxide and polyethylene wear particles from joint endoprostheses using cathodoluminescence and x-ray analysis in SEM.

A highly sensitive method to localize aluminum oxide or polyethylene wear particles in biological tissues is presented. Using the scanning electron microscope (SEM) with a special cathodoluminescence detector system, small amounts of these foreign materials can be visualized in simple frozen sections by their bright luminescence, even at low magnifications (200X). At higher magnifications, a differentiation of free as well as phagocytized aluminum oxide and polyethylene particles can be made due to their different behavior in light emission. In addition, aluminum oxide such as other metals can be identified by x-ray microprobe analysis. This combination of SEM with microprobe analysis and with the highly sensitive cathodoluminescence mode enables to detect and identify wear products from all the materials, commonly used in manufacturing artificial joint replacements.

[Biocompatibility of wood in bone tissue (author's transl)]. / Verträglichkeitsuntersuchungen von Holz im Knochengewebe.

Alcohol-extracted and sterilised cylinders of ash- and birchwood were implanted into the tibia of rabbits. The selection criteria of these two wood species were thoroughly described. 28 implants were evaluated after 3, 5, 14 and 32 weeks using undecalcified microtome sections and ground sections employing polychromatic sequential-labelling and microradiography. In spite of a foreign-body-tissue reaction new bone is formed around the implants and within the pores of the wood as well. Both wood species therefore seem to be suitable implant materials, which were anchoraged by the bone itself. A tensile strength and elastic properties comparable to bone and simple handling would be the advantages of this material.