Anchorage Of Implants Research Articles

Compressive Osseointegration of Tibial Implants in Primary Cancer Reconstruction

Compressive osseointegration technology, which provides immediate, mechanically compliant endoprosthetic fixation, has been adapted for massive proximal tibial reconstructions in an attempt to avoid aseptic failure encountered with conventional stems. A retrospective review of 16 patients with resected tumors was undertaken to determine whether compressive osseointegration can provide durable anchorage of tibial implants. Medical records, radiographs, and clinical examinations were reviewed to assess surgical, local disease control, and prosthetic outcomes. The average age was 18 years (range, 12–42 years). Diagnoses included osteosarcoma (12), Ewing sarcoma (two), chondrosarcoma (one), and undifferentiated sarcoma (one). Minimum followup was 2 years (mean, 4.5 years; range, 2–10.3 years); no patient was lost to followup. There were no local recurrences. Four patients developed metastatic disease; one patient died of his primary tumor, and another died from a chemotherapy-related malignancy. Complications included one early deep infection that ultimately resulted in prosthetic loosening and the need for an above-knee amputation. There were two late deep infections; prosthetic retention was achieved with débridement and antibiotics. One patient developed aseptic loosening and underwent revision; the other 15 implants provided stable osseointegration at last followup. Compressive osseointegration technology can thus achieve acceptable short-term endoprosthetic fixation results and may reduce the risk of aseptic loosening reported with conventional tibial stems.Level of Evidence: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Influence of osteoporosis on fracture fixation - a systematic literature review

The goal of our systematic literature search was to prove whether the experimentally shown influence of osteoporosis on fracture fixation could be confirmed in clinical studies. Despite significant effects in several studies, this is not supported by pooled data due to lack of accurate osteoporosis assessment and complication definitions. The fact that osteoporosis causes fractures is well-known; the assumption that it aggravates their orthopaedic treatment has not been proven. The goal of our systematic literature search was to find out whether the experimentally proven influence of osteoporosis on fracture fixation could be confirmed in clinical studies. A systematic electronic database search was performed identifying articles that evaluated complications after fracture fixation among patients suspected of having osteoporosis as measured by BMD or surrogates including Singh index or risk factors. To determine complications risks (relative risk within 95% confidence interval) data were pooled across studies, weighted by sample size and stratified by treatment type. Ten studies out of 77 randomized controlled trials (51 hip, 23 distal radius and three proximal humerus studies) and three systematic reviews finally met eligibility criteria. Despite significant differences of the relative complication risk between osteoporotic and non-osteoporotic patients in several studies, this could not be proven in the pooled data. In contrast to biomechanical evidence that local osteoporosis affects anchorage of implants, this could not be reproduced in clinical studies, due to the lack of accurate osteoporosis assessment, missing complication definitions and heterogeneous inclusion criteria in these studies. Prospective studies are required that address specifically the correlation between local bone status and the risk of fixation failure.

Poster 158: The Extra-Alveolar Provisional Implant System

Poster 158: The Extra-Alveolar Provisional Implant System

Oxidized nickel–titanium foams for bone reconstructions: chemical and mechanical characterization

This work examines NiTi foams that have been treated using a new oxidation treatment for obtaining Ni-free surfaces that could allow the ingrowth of living tissue, thereby increasing the mechanical anchorage of implants. A significant increase in the real surface area of these materials can decrease corrosion resistance and favour the release of Ni. This chemical degradation can induce allergic reactions or toxicity in the surrounding tissues. This study determines the porosity, surface characteristics, phase transformation, mechanical properties, corrosion behaviour and Ni release into the simulated body fluid medium of foams treated by a new surface oxidation treatment that produces Ni-free surfaces. These foams have pores in an appropriate range of sizes and interconnectivity, and thus their morphology is similar to that of bone. Their mechanical properties are biomechanically compatible with bone. The titanium oxide on the surface significantly improves corrosion resistance and decreases nickel ion release, while barely affecting transformation temperatures.

Mechanical properties of nickel–titanium foams for reconstructive orthopaedics

Porous NiTi materials were obtained in order to allow the ingrowth of living tissue, thus increasing the mechanical anchorage of implants. This promotes long-term fixation without the need for bone grafting. This study focuses mainly on the determination of mechanical properties: compression, bending and compressive fatigue. The foams obtained had an appropriate range of pore sizes and interconnectivity, which enabled a morphology similar to that of bone to be achieved. Their mechanical properties proved to be highly compatible with those of bone (an elastic modulus similar to that of cancellous bone), and the compressive fatigue limit was 7.5 MPa at 10 7 cycles with samples exhibiting significant plastic deformation. SEM examination showed cracking at strut junctions 45° to the axis of the applied load. The results indicate that the material provides structural support while bone ingrowth is taking place.

Effects of surface morphology on human osteosarcoma cell response

It is known that surface roughness enhances the anchorage of implants to bone and opens up the possibilities of the incorporation and release of antibiotics around titanium implants. In this study, titanium oxide was formed by the micro-arc oxidation (MAO) method. Commercially available pure titanium disks with diameter of 10 mm and 2 mm in thickness were used as substrates. MAO of the specimen was carried out in an aqueous electrolyte by applying a pulsed DC wave to the specimen. The surface characteristics of the MAO implants, including surface morphology and surface roughness, were analyzed by SEM and surface profilometer, respectively. The purpose of this study is to evaluate the effect produced by MAO of the titanium surface on cell cultures by cell proliferation assay, cell morphology and alkaline phosphatase activity. The results showed the formation of an oxide layer with micropores and roughness by MAO. No significant difference in the proliferation and spreading morphology of machined, blasted and MAO surfaces was observed. However, the ALP activity of osteoblast cells on MAO surface was higher than on machined and blasted surfaces in 4 day and 7 day cultures, respectively. From this study, it was concluded that the MAO-treated titanium exhibited an effect on early osteoblast differentiation.

Retrieved Implants from Irradiated Sites in Humans: A Histologic/Histomorphometric Investigation of Oral and Craniofacial Implants

The aim of this report was to quantitatively and qualitatively evaluate the tissue response to bone-anchored implants retrieved from irradiated sites in patients. The material consists of 23 consecutively received Brånemark implants (Nobel Biocare AB, Göteborg, Sweden) placed in pre- or postoperatively irradiated sites. Twenty-two of the 23 implants were suitable for histologic evaluation of undecalcified sections in the light microscope. The oral implants with shorter time in situ demonstrated sparse bone to implant contact with mainly dense connective tissue in the interface. However, for implants with longer time in situ, high amounts of bone-implant contact and bone fill of threads were noted. The mean values of bone-implant contact and bone area within the thread were calculated to 40% (16-94) and 70% (13-96), respectively. The craniofacial implants, with the exception of two implants lined with a capsular formation, demonstrated mature and newly formed bone at the bone-implant interface. The mean value for bone-metal contact was calculated to 45 and 53% for two specimens. The mean value for bone area within the thread ranged from 65 to 88% for three specimens. CONCLUSION; The possibility to achieve bone anchorage of implants in irradiated tissue was supported by the findings in this study. However, due to limited material, conclusions with regard to radiation dose and bone tissue response to implants cannot be stated.

Maxillary sinus floor grafting with β‐tricalcium phosphate in humans: density and microarchitecture of the newly formed bone

Graft insertion can effectively enhance the regeneration of debilitated bone. The effects of an alloplastic bone-replacing material, beta-tricalcium phosphate (Cerasorb), and of autogenous bone graft were compared. In 17 edentulous patients, the maxillary sinus floor was extremely atrophied to such an extent that implant placement was impossible. The Schneiderian membrane was surgically elevated bilaterally by insertion of Cerasorb (experimental side) and autogenous bone graft (control side). After surgery, the recovery was followed clinically and radiologically. After 6 months, 68 bone cylinders were excised from the grafted areas and implants were inserted into their places. The bone samples were embedded into resin, and the osteointegration of the grafts was studied histologically. Trabecular bone volume (TBV) and trabecular bone pattern factor (TBPf) were quantified by histomorphometry. Cerasorb proved to be an effective bone-replacing material with osteoconductivity; it was capable of gradual disintegration, thereby providing space for the regenerating bone. The new bone density was not significantly different on the experimental and control sides (32.4+/-10.9% and 34.7+/-11.9%, respectively). However, the graft biodegradation was significantly slower on the experimental side than the control side. The TBPf value was lower on the control side than on the experimental side (-0.53+/-1.7 and -0.11+/-1.4 mm(-1), respectively), but this difference was not significant. Six months after insertion of the grafts, the bone of the augmented sinus floor was strong and suitable for anchorage of dental implants, irrespective of whether autogenous bone or Cerasorb particles had been applied.

H�ftendoprothetik

The replacement of a hip joint after osteoarthritis or fracture is today a standard surgical procedure and performed worldwide in about 750,000 cases. Since it is possible to achieve durable anchorage of implants in bone and to effectively treat loss of function and pain of the hip joint, this operation belongs to the most successful in our times.Therefore, a differentiated technology has developed that encompasses modern implant materials, biomechanical knowledge, and surgical techniques. Current standards in this procedure are demonstrated.

New implant designs for fracture fixation in osteoporotic bone

Screws are one of the limiting factors for fixation of implants, particularly in poor bone quality. A class of new implants with an implant-bone-interface optimized regarding load transition by increasing the peripheral area might improve the anchorage of implants in osteoporotic bone. However, the shape of these implants requires new technologies for insertion. The goal of the work presented here was to analyze the relevant parameters regarding implant geometry and to demonstrate the effect of new procedures for their insertion. The investigation was divided into three parts: 1) implant design optimisation, 2) efficiency of cortical bone ablation, and 3) implant insertion technology. Finite element analysis (FEA) was performed to investigate the influence of the number of lobes, the radius of the outer curvature and additional milling to remove any sharp changes of section around the lobe. Opening of the cortical bone with an Er:YAG laser was studied using calf cortex from 2 to 7 mm thickness. The effect of a) pulse energy and pulse duration, b) cortical thickness, c) wet or dry boundary conditions on volume and geometry of ablated bone, time required to penetrate the cortical bone and local bone tissue damage was quantified. Pneumatic and ultrasound based insertion were compared in the third experiment. The cortical bone was prepared in the following ways: a) no opening, b) predrilling of three holes (1 mm diameter each) and c) exact pre-cutting of the whole contour. Increasing the radius of the outer curvature from 2 to 5 mm reduces the peak stresses during loading in all planes in the implant as well as in the adjacent cortical bone by about 30-40%. An increase in the number of lobes from two to three decreases the mean peak stress by about 46% (alpha < 0.001) and the range between the minimal and maximal peak stresses for different loading directions by about 83%. Penetration of cortical bone with an Er:YAG laser was possible up to a cortical thickness of 6 mm with fewer than 100 pulses. The ablation rate per pulse increased more with increasing duration than with increasing energy. Signs of bone damage such as melting were only visible when high pulse energies and durations were used. Insertion of the prototype was possible with all devices, but only when the whole contour was cut out of the cortical bone. However, the use of the ultrasound vibrator led to heating up of the tissue fluid and subsequently to water evaporation and tissue damage. Insertion of the prototype was possible with both pneumatic vibrators, but only when the whole contour was cut out of the cortical bone. New implant designs may lead to reduced stress peaks in the surrounding bone and might be inserted with the help of new insertion technologies, namely laser cutting of cortical bone and pneumatic vibration. Further studies are required to optimize these technologies prior to clinical use.

Titanium implants and BMP-7 in bone: an experimental model in the rabbit.

This study evaluates the effect of rhBMP-7/OP-1 on the osseointegration of commercially pure titanium implants in an experimental implant model in rabbits. Threaded titanium implants with two transverse parallel canals were inserted in the femur and tibia of rabbits. The canals were filled with, 10 microg of BMP-7/collagen carrier, pure collagen carrier or were left empty as a control. The stiffness of the implant fixation was evaluated by Resonance Frequency Analysis (RFA) at baseline and four weeks postoperatively. Percentage of bone ingrowth in the canals was measured on microradiographs. Histomorphometry along the threaded part of the implants was performed on 15 microm thin sections. The results from the RFA demonstrated a higher mean value for the BMP-7 treated implants in the tibia than the carrier treated implants but not compared to the control implants. The control implants in the tibia demonstrated more bone ingrowth in the upper canal than to the carrier or the BMP-7 treated implants. Apart from these differences there were no significant effects of BMP. In this study BMP-7 did not contribute to any substantially improved bone anchorage of titanium implants.

Investigation of cell reactions to microstructured implant surfaces

Surface topography is one of the key parameters influencing cellular reactions towards artificial materials. Surfaces with defined microstructures may be useful for enhancement of the stable anchorage of transcutaneous implants in connective tissue or for prevention of epithelial downgrowth and subsequent exfoliation. Cell reactions of keratinocytes and fibroblasts were investigated on microstructured titanium experimental surfaces with alternating grooves and ridges in the range between 1–20 μm width and 0.4–2.0 μm depth. While fibroblasts displayed oriented cell growth on the structured surfaces, human keratinocytes failed to show orientation or enhanced number of focal contacts on structures in the 2–10 μm width range. In that respect, an influence of surface structure on initial cell adhesion could not be proven. The influence of a “bioactive” fibronectin (Fn) coating on adhesion and spreading of fibroblasts was tested on smooth and structured titanium model implant surfaces. Cell spreading was enhanced significantly by the fibronectin coating. Under mechanical shear stress conditions which simulated stresses during insertion of dental implants, the stimulating effects of Fn were lost on smooth surfaces due to abrasion of the coating, while complete abrasion was prevented by microstructured surfaces. The combination of microstructures with “bioactive” coatings may be used to trigger specific cell responses in areas of the implant surface with different functionality. Adhesion and growth of different cell types on microstructured surfaces was investigated by a modified technique at the electron microscopy (EM) level. The approach allows the detection of adhesion molecules in the different membrane domains by immunocytochemical gold labelling techniques. Preliminary results with this new technique suggest that vinculin is localized in the grooves rather than on the ridges in our model system.

Ti 4+ to Ti 3+ Conversion of TiO 2 Uppermost Layer by Low-Temperature Vacuum Annealing: Interest for Titanium Biomedical Applications

Because of the Ti 3+ defects responsibility for dissociative adsorption of water onto TiO 2 surfaces and due to the hydroxyls influence on the biological behavior of titanium, controlling the Ti 3+ surface defects density by means of low-temperature vacuum annealing is proposed to improve the bone/implant interactions. Experiments have been carried out on Ti-6Al-4V alloys exhibiting a porous surface generated primarily by chemical treatment. XPS investigations have shown that low-temperature vacuum annealing can create a controlled number of Ti 3+ defects (up to 21% Ti 3+/Ti 4+ at 573 K). High Ti 3+ defect concentration is linked to surface porosity. Such surfaces, exhibiting high hydrophilicity and microporosity, would confer to titanium biomaterials a great ability to interact with surrounding proteins and cells and hence would favor the bone anchorage of as-treated implants.

Minimally invasive ventral release and endoscopic ventral instrumentation in scoliosis

We report on three years of experience with a new method of a simultaneous endoscopically assisted anterior release in the prone position, combined with transpedicular posterior scoliosis correction and fixation. In 60 cases this simultaneous approach yielded substantial advantages. True derotation of the apex--even in the thoracic spine--is achieved. Because of resection of apical discs, the hypokyphosis can be corrected easily. Apical derotation, restoration of the kypotic profile and more effective correction of lateral translation add up to true three-dimensional correction of scoliosis. The disadvantages of insufficient anterior anchorage of fixation implants are avoided, since correction and fixation are achieved posteriorly. An additional advantage of this combined approach and the use of pedicular screws is the fact that in idiopathic scoliosis fusion that is no longer than from end- to end-vertebrae is sufficient. Thus, in most King II curves the thoracolumbar junction does not need to be fused.

Wound healing around bone-anchored percutaneous devices in experimental diabetes mellitus.

The objective of this investigation was to study the influence of impaired wound healing on the tissue response to bone-anchored percutaneous devices. For this reason, diabetes mellitus was induced in rabbits with alloxan. Untreated rabbits were used as controls. Skin-penetrating titanium implants were inserted in the tibial bone of diabetic and healthy animals. The enossal part of half of the implants was provided with a thin magnetron-sputtered calcium-phosphate coating. The soft-tissue and bone response was evaluated clinically, histologically, and histomorphometrically. We did not observe more infectious complications in diabetic animals. Furthermore, histological analysis revealed no differences in soft-tissue response between diabetic and healthy animals. A close bone-implant contact was observed for all implants. Nevertheless, the density of cortical bone around the implants was clearly lower in diabetic animals compared with control animals. In control rabbits, but not diabetic animals, coated implants showed more downgrowth of bone into the marrow cavity than uncoated ones. In general, diabetes mellitus was shown to have no adverse effect on the clinical performance of the percutaneous devices. We think that this is due to the good fixation of the implants in diabetic as well as control animals. Therefore, we conclude that the presence of impaired healing in chronic health disorders like diabetes is no contra-indication for the anchorage of percutaneous implants in cortical bone.

Influence of mono- and bicortical anchorage on the integration of titanium implants: A study in the rabbit tibia

The study aimed to evaluate the removal torque and bone tissue response to titanium implants supported by one or two cortical layers. A total of 72 screw titanium implants, either 10 or 16 mm in length and 3.75 mm in diameter, were inserted in right and left tibiae of 18 adult New Zealand rabbits. The implants engaged either one or two cortical layers, and the animals were allowed a healing period of 6 or 12 weeks. The degree of integration was assessed by measuring the removal torque with a torque gauge manometer. Histomorphometric calculations were also performed in 10-μm-thick ground sections. All implants were clinically stable at the end of the experiment. The removal torque was two times higher for the bicortical implants after 6 weeks, and three times higher after 12 weeks, than for the monocortical ones. The 16-mm implants also showed a statistically higher amount of bone contact and bone area after 6 and 12 weeks, respectively, than the short ones. The results support bicortical anchorage of implants also in the clinical situation.

The bottle brush: A new concept for uncemented anchorage of bone implants: Berggren A. Scand J Plast Reconst Hand Surg 29:221, 1995

The bottle brush: A new concept for uncemented anchorage of bone implants: Berggren A. Scand J Plast Reconst Hand Surg 29:221, 1995

The bottle brush: a new concept for uncemented anchorage of bone implants. Preliminary mechanical and biomechanical studies: M. Berggren, A. Berggren, L. T. Östrup. Scand J Plast Reconstr Hand Surg 1995; 29: 221–226

The bottle brush: a new concept for uncemented anchorage of bone implants. Preliminary mechanical and biomechanical studies: M. Berggren, A. Berggren, L. T. Östrup. Scand J Plast Reconstr Hand Surg 1995; 29: 221–226

Anchorage of TiO2-blasted, HA-coated, and machined implants: an experimental study with rabbits.

The purpose of this study was to evaluate the histometrical and biomechanical anchorage of TiO2-blasted implants and TiO2-blasted implants coated with hydroxyapatite. The control implants were machined. Twenty-six rabbits had a total of 156 implants placed in the proximal part of the tibia. Each rabbit had a machined, a TiO2-blasted, and a TiO2-blasted, HA-coated implant placed in each tibia. After a healing period of 3 and 12 weeks, respectively, the implants placed in the right tibia were used for removal torque test, and the implants placed in the left tibia were used for histomorphometrical measurements. Preoperatively, implants from the same batches were examined topographically with a TopScan 3D system. The TiO2-blasted implants demonstrated significantly higher removal torque values than the machined implants, and they also had a significantly more irregular surface. Furthermore, significantly higher bone-to-implant contact length fractions were measured adjacent to the TiO2-blasted implants in contrast to the machined implants. The advantages of a TiO2-blasted surface were more pronounced after 3 weeks than after 12 weeks. The results demonstrated that it was possible to influence the anchorage of implants by altering the surface structure morphology. The new method with TiO2 blasting on the titanium surface improves the anchorage of implants but is not yet practicable for HA coating.

The "bottle brush": a new concept for uncemented anchorage of bone implants. Preliminary mechanical and biomechanical studies.

We present a new concept for bone of implants, the "bottle brush". It may be suitable for joint prostheses, dental or percutaneous implants, or other devices fixed into bone. Mechanical pullout studies in artificial brass cavities of different sizes and shapes and implantation studies in 20 rabbits, have been successfully carried out. Further experimental and clinical studies are in progress.