Forearm bone-anchored amputation prosthesis: a case study on the osseointegration

Single-Stage Press-Fit Osseointegration of the Radius and Ulna for Rehabilitation After Trans-Forearm Amputation

Background

Upper limb (UL) amputation is disabling. ULs are necessary for many domains of life1, and few effective motor and sensory replacements are accessible2. Approximately 41,000 people in the United States have UL amputation proximal to the fingers3, two-thirds of (all) traumatic amputations are UL4, and 80% of UL amputations are performed for trauma-related etiologies5. Socket prosthesis (SP) abandonment remains high because of the lack of sensation, limited prosthesis control, perceived weight, and difficulty comfortably wearing the SP6. Transcutaneous osseointegration7,8 surgically inserts a bone-anchored implant, passed through a transcutaneous portal to attach a terminal device, improving amputee rehabilitation by reducing perceived weight, conferring osseoperception9, and increasing wear time10. Without the socket, all residual skin and musculature remain available for transcutaneous myoelectrodes. The present article describes single-stage radius and ulna press-fit osseointegration (PFOI) after trans-forearm amputation.

Description

This technique resembles a lower-extremity PFOI11,12. Importantly, at-risk nerves and vessels are different, and implant impaction must be gentler as a result. The surgery is indicated for patients who are dissatisfied with SP rehabilitation or declining alternative rehabilitative options, and who are motivated and enabled to procure, train with, and utilize a forearm prosthesis. An engaged prosthetist is critical. Surgical steps are exposure, bone-end and canal preparation, first implant insertion (in the operative video shown, in the radius), purse-string muscle closure, confirmation that radius-ulna motion remains, performing the prior steps for the other bone (in the video, the ulna), and closure (including potential nerve reconstruction, soft-tissue contouring, and portal creation). Although the patient in the operative video did not require nerve procedures to address pain or to create targets for transcutaneous myoelectrodes, targeted muscle reinnervation or a regenerative peripheral nerve interface procedure could be performed following exposure.

Alternatives

Alternatives include socket modification, bone lengthening and/or soft-tissue contouring13, Krukenberg-type reconstructions14, or accepting the situation. An alternative implant is a screw-type osseointegration implant. Our preference for press-fit implants is based on considerations such as our practice's 12-year history of >1,000 PFOI surgeries; that the screw-type implant requires sufficient cortical thickness for the threads15, which is compromised in some patients; the lower cost per implant; that the procedure is performed in 1 instead of 2 surgical episodes15,16; and the documented suitability of press-fit implants for patients with challenging anatomy or comorbidities17-19.

Rationale

PFOI can be provided for amputees having difficulty with socket wear. PFOI usually provides superior prosthesis stability, which can confer better prosthesis control versus nonoperative and other operative options in patients expressing dissatisfaction for reasons such as those mentioned above, or for poor fit, compromised energy transfer, skin pinching, compression, and abrasions. For patients who want myoelectric control of their prosthesis but who are unable because the optimal myoelectric location is obstructed by the socket, osseointegration may provide access for the electrodes by eliminating the socket.

Expected Outcomes

Only 3 trans-forearm osseointegration20-22 publications totaling 10 limbs could be identified, limiting the ability to determine generalizable outcomes. Osseointegrated prostheses, being skeletally anchored, feel lighter to patients than SPs, which should confer better outcomes. In 1 patient, multiple implant fractures and infection prompted additional surgeries. Periprosthetic bone fractures and non-infectious loosening have not been documented for UL osseointegration.

Important Tips

Osseointegration eliminates the socket, relieving socket-based pain. However, neurogenic pain relief requires specific nerve procedures.Osseointegration provides a prosthesis connection. Nerve- or muscle-based prosthesis control requires separate, potentially integrated planning.Osseointegrated prostheses confer osseoperception (i.e., mechanical force transmission), not "normal" skin-mediated afferent sensation (i.e., light touch, temperature, pain) or native proprioception.Prostheses must be individualized to the patient's elbow flexion and radioulnar rotation. An attentive prosthetist must be ensured preoperatively.Achieving the demonstrated outcomes requires more therapy and retraining than walking with an osseointegrated lower-extremity prosthesis. Patients must expect at least several months of spending multiple hours daily engaging in self-directed rehabilitation.Prosthesis utilization decision aids23 may minimize non-beneficial surgeries.

Acronyms and Abbreviations

UL = upper limbSP = socket prosthesisPFOI = press-fit osseointegrationperi-pros fx = periprosthetic fractureMRI = magnetic resonance imagingCT = computed tomography.

Use of computer tomography imaging for analyzing bone remodeling around a percutaneous osseointegrated implant

Osseointegration (OI) is being used for the direct skeletal attachment of prosthetic limbs using an intramedullary stem that extends percutaneously from the subject's residual limb. For this technology to be successful, bone ingrowth and remodeling around the implant must occur. Physicians need an effective way to assess bone remodeling to make informed treatment and rehabilitation decisions. Previous studies utilizing two-dimensional imaging X-ray as a tool to monitor bone-remodeling around OI devices have limitations. This study describes methodology that was developed utilizing computed tomography (CT) imaging as a tool for analyzing bone remodeling around a percutaneous OI implant. Six transfemoral amputees implanted with a percutaneous osseointegrated prosthesis (POP) had CT scans taken of their residual femur at 6 and 52 weeks postoperatively. Three-dimensional femoral models were processed using custom MATLAB script to collect cortical and medullary morphology measurements. Morphology data from 6- and 52-week scans were compared to quantify bone remodeling around the POP implant. Fifty-two weeks after implantation of the POP device, increases in cortical bone area and thickness were observed around the porous-coated stem. Minimal changes were observed in the medullary canal parameters within the periprosthetic regions. This study successfully utilized CT imaging and three-dimensional modeling techniques to analyze longitudinal data of bone remodeling around a transfemoral percutaneous implant. These methods have the potential to be used as a clinical tool for evaluating orthopedic implants in vivo. Data collected suggests that the POP device achieved the desired bone remodeling around the porous-coated region of the implanted stem.

Multimodal Analysis of the Tissue Response to a Bone-Anchored Hearing Implant: Presentation of a Two-Year Case Report of a Patient With Recurrent Pain, Inflammation, and Infection, Including a Systematic Literature Review

Osseointegration is a well-established concept used in applications including the percutaneous Bone-Anchored Hearing System (BAHS) and auricular rehabilitation. To date, few retrieved implants have been described. A systematic review including cases where percutaneous bone-anchored implants inserted in the temporal bone were retrieved and analyzed was performed. We also present the case of a patient who received a BAHS for mixed hearing loss. After the initial surgery, several episodes of soft tissue inflammation accompanied by pain were observed, leading to elective abutment removal 14 months post-surgery. Two years post-implantation, the implant was removed due to pain and subjected to a multiscale and multimodal analysis: microbial DNA using molecular fingerprinting, gene expression using quantitative real-time polymerase chain reaction (qPCR), X-ray microcomputed tomography (micro-CT), histology, histomorphometry, backscattered scanning electron microscopy (BSE-SEM), Raman spectroscopy, and fluorescence in situ hybridization (FISH). Evidence of osseointegration was provided via micro-CT, histology, BSE-SEM, and Raman spectroscopy. Polymicrobial colonization in the periabutment area and on the implant, including that with Staphylococcus aureus and Staphylococcus epidermidis, was determined using a molecular analysis via a 16S-23S rDNA interspace [IS]-region-based profiling method (IS-Pro). The histology suggested bacterial colonization in the skin and in the peri-implant bone. FISH confirmed the localization of S. aureus and coagulase-negative staphylococci in the skin. Ten articles (54 implants, 47 patients) met the inclusion criteria for the literature search. The analyzed samples were either BAHS (35 implants) or bone-anchored aural epitheses (19 implants) in situ between 2 weeks and 8 years. The main reasons for elective removal were nonuse/changes in treatment, pain, or skin reactions. Most samples were evaluated using histology, demonstrating osseointegration, but with the absence of bone under the implants’ proximal flange. Taken together, the literature and this case report show clear evidence of osseointegration, despite prominent complications. Nevertheless, despite implant osseointegration, chronic pain related to the BAHS may be associated with a chronic bacterial infection and raised inflammatory response in the absence of macroscopic signs of infection. It is suggested that a multimodal analysis of peri-implant health provides possibilities for device improvements and to guide diagnostic and therapeutic strategies to alleviate the impact of complications.

A vessel subtype beneficial for osteogenesis enhanced by strontium-doped sodium titanate nanorods by modulating macrophage polarization

Early vascularization plays an important role in bone healing, especially in interfacial bone formation.

Osseointegration and current interpretations of the bone-implant interface

Complex physical and chemical interactions take place in the interface between the implant surface and bone. Various descriptions of the ultrastructural arrangement to various implant design features, ranging from solid and macroporous geometries to surface modifications on the micron-, submicron-, and nano- levels, have been put forward. Here, the current knowledge regarding structural organisation of the bone-implant interface is reviewed with a focus on solid devices, mainly metal (or alloy) intended for permanent anchorage in bone. Certain biomaterials that undergo surface and bulk degradation are also considered. The bone-implant interface is a heterogeneous zone consisting of mineralised, partially mineralised, and unmineralised areas. Within the meso-micro-nano-continuum, mineralised collagen fibrils form the structural basis of the bone-implant interface, in addition to accumulation of non-collagenous macromolecules such as osteopontin, bone sialoprotein, and osteocalcin. In the published literature, as many as eight distinct arrangements of the bone-implant interface ultrastructure have been described. The interpretation is influenced by the in vivo model and species-specific characteristics, healing time point(s), physico-chemical properties of the implant surface, implant geometry, sample preparation route(s) and associated artefacts, analytical technique(s) and their limitations, and non-compromised vs compromised local tissue conditions. The understanding of the ultrastructure of the interface under experimental conditions is rapidly evolving due to the introduction of novel techniques for sample preparation and analysis. Nevertheless, the current understanding of the interface zone in humans in relation to clinical implant performance is still hampered by the shortcomings of clinical methods for resolving the finer details of the bone-implant interface. STATEMENT OF SIGNIFICANCE: Being a hierarchical material by design, the overall strength of bone is governed by composition and structure. Understanding the structure of the bone-implant interface is essential in the development of novel bone repair materials and strategies, and their long-term success. Here, the current knowledge regarding the eventual structural organisation of the bone-implant interface is reviewed, with a focus on solid devices intended for permanent anchorage in bone, and certain biomaterials that undergo surface and bulk degradation. The bone-implant interface is a heterogeneous zone consisting of mineralised, partially mineralised, and unmineralised areas. Within the meso-micro-nano-continuum, mineralised collagen fibrils form the structural basis of the bone-implant interface, in addition to accumulation of non-collagenous macromolecules such as osteopontin, bone sialoprotein, and osteocalcin.

Peromelia - congenital transverse deficiency of the upper limb: a literature review and current prosthetic treatment

Peromelia or congenital transverse deficiency describes a truncation of the upper limb below various limb levels. Recommendations regarding treatment vary and are mainly based on expert opinions. This paper summarizes the current literature regarding the aetiology, pathogenesis and specifically treatment algorithms for children with peromelia. We performed a non-systematic review of the current literature from MEDLINE/PubMed to obtain comprehensive up-to-date information about peromelia, focusing on current recommendations for the treatment of peromelia (e.g. prosthetic fitting, external stump lengthening). The current literature lacks clear evidence as to whether prosthetic treatment is superior to prosthetic non-usage. However, based on the available studies, children with transradial or transhumeral peromelia should preferably be fitted with passive/cosmetic prostheses at the age between six and 24 months, followed by active/myoelectric devices at the age of 2.5 to four years. It remains controversial whether early myoelectric prosthetic fitting can reduce prosthesis rejection times; however, cognitive readiness and the ability to absolve a guided training programme are seen as important prerequisites for myoelectric fitting. Children with very short stumps may benefit from stump lengthening using external fixators and prosthetic modification. The treatment of children with peromelia generally requires a guided, multidisciplinary team approach. A training programme is essential to optimize individuals' performance in the execution of activities of daily living and decrease rejection risks whenever a myoelectric device is prescribed. Myoelectric fitting should preferably be commenced at no later than four years of age. However, long-term reports on the benefits of prosthetic treatment are still pending.

Biomechanical Characterisation of Bone-anchored Implant Systems for Amputation Limb Prostheses: A Systematic Review

Bone-anchored limb prostheses allow for the direct transfer of external loads from the prosthesis to the skeleton, eliminating the need for a socket and the associated problems of poor fit, discomfort, and limited range of movement. A percutaneous implant system for direct skeletal attachment of an external limb must provide a long-term, mechanically stable interface to the bone, along with an infection barrier to the external environment. In addition, the mechanical integrity of the implant system and bone must be preserved despite constant stresses induced by the limb prosthesis. Three different percutaneous implant systems for direct skeletal attachment of external limb prostheses are currently clinically available and a few others are under investigation in human subjects. These systems employ different strategies and have undergone design changes with a view to fulfilling the aforementioned requirements. This review summarises such strategies and design changes, providing an overview of the biomechanical characteristics of current percutaneous implant systems for direct skeletal attachment of amputation limb prostheses.

Effect of load on the bone around bone-anchored amputation prostheses

Osseointegrated transfemoral amputation prostheses have proven successful as an alternative method to the conventional socket-type prostheses. The method improves prosthetic use and thus increases the demands imposed on the bone-implant system. The hypothesis of the present study was that the loads applied to the bone-anchored implant system of amputees would result in locations of high stress and strain transfer to the bone tissue and thus contribute to complications such as unfavourable bone remodeling and/or elevated inflammatory response and/or compromised sealing function at the tissue-abutment interface. In the study, site-specific loading measurements were made on amputees and used as input data in finite element analyses to predict the stress and strain distribution in the bone tissue. Furthermore, a tissue sample retrieved from a patient undergoing implant revision was characterized in order to evaluate the long-term tissue response around the abutment. Within the limit of the evaluated bone properties in the present experiments, it is concluded that the loads applied to the implant system may compromise the sealing function between the bone and the abutment, contributing to resorption of the bone in direct contact with the abutment at the most distal end. This was supported by observations in the retrieved clinical sample of bone resorption and the formation of a soft tissue lining along the abutment interface. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1113-1122, 2017.

Direct communication between osteocytes and acid-etched titanium implants with a sub-micron topography

The osteocyte network, through the numerous dendritic processes of osteocytes, is responsible for sensing mechanical loading and orchestrates adaptive bone remodelling by communicating with both the osteoclasts and the osteoblasts. The osteocyte network in the vicinity of implant surfaces provides insight into the bone healing process around metallic implants. Here, we investigate whether osteocytes are able to make an intimate contact with topologically modified, but micrometre smooth (S a < 0.5 µm) implant surfaces, and if sub-micron topography alters the composition of the interfacial tissue. Screw shaped, commercially pure (cp-Ti) titanium implants with (i) machined (S a = ~0.2 µm), and (ii) two-step acid-etched (HF/HNO3 and H2SO4/HCl; S a = ~0.5 µm) surfaces were inserted in Sprague Dawley rat tibia and followed for 28 days. Both surfaces showed similar bone area, while the bone-implant contact was 73 % higher for the acid-etched surface. By resin cast etching, osteocytes were observed to maintain a direct intimate contact with the acid-etched surface. Although well mineralised, the interfacial tissue showed lower Ca/P and apatite-to-collagen ratios at the acid-etched surface, while mineral crystallinity and the carbonate-to-phosphate ratios were comparable for both implant surfaces. The interfacial tissue composition may therefore vary with changes in implant surface topography, independently of the amount of bone formed. Implant surfaces that influence bone to have higher amounts of organic matrix without affecting the crystallinity or the carbonate content of the mineral phase presumably result in a more resilient interfacial tissue, better able to resist crack development during functional loading than densely mineralised bone.

Targeted muscle reinnervation and advanced prosthetic arms

Targeted muscle reinnervation (TMR) is a surgical procedure used to improve the control of upper limb prostheses. Residual nerves from the amputated limb are transferred to reinnervate new muscle targets that have otherwise lost their function. These reinnervated muscles then serve as biological amplifiers of the amputated nerve motor signals, allowing for more intuitive control of advanced prosthetic arms. Here the authors provide a review of surgical techniques for TMR in patients with either transhumeral or shoulder disarticulation amputations. They also discuss how TMR may act synergistically with recent advances in prosthetic arm technologies to improve prosthesis controllability. Discussion of TMR and prosthesis control is presented in the context of a 41-year-old man with a left-side shoulder disarticulation and a right-side transhumeral amputation. This patient underwent bilateral TMR surgery and was fit with advanced pattern-recognition myoelectric prostheses.

Resolving the CaP-bone interface: a review of discoveries with light and electron microscopy

It has long been known that the interfacial relationship between synthetic materials and tissue is influential in the success of implant materials. Instability at the implant interface has been shown, in some cases, to lead to complete implant failure. Bioceramics, and in particular calcium phosphates, form a large fraction of the implantable devices on the market today due to the biocompatibility they exhibit in contact with bone and tooth-like tissues. The characterization of such bioceramic-tissue interfaces has played a crucial role in understanding the behavior of bioceramics in vivo. In this review, we shed light on the preparation methods, technological approaches and key advances in resolving the interface between calcium phosphate bioceramics and bone, and share a future outlook on this field.

An overview of recent advances in designing orthopedic and craniofacial implants

Great deal of research is still going on in the field of orthopedic and craniofacial implant development to resolve various issues being faced by the industry today. Despite several disadvantages of the metallic implants, they continue to be used, primarily because of their superior mechanical properties. In order to minimize the harmful effects of the metallic implants and its by-products, several modifications are being made to these materials, for instance nickel-free stainless steel, cobalt-chromium and titanium alloys are being introduced to eliminate the toxic effects of nickel being released from the alloys, introduce metallic implants with lower modulus, reduce the cost of these alloys by replacing rare elements with less expensive elements etc. New alloys like tantalum, niobium, zirconium, and magnesium are receiving attention given their satisfying mechanical and biological properties. Non-oxide ceramics like silicon nitride and silicon carbide are being currently developed as a promising implant material possessing a combination of properties such as good wear and corrosion resistance, increased ductility, good fracture and creep resistance, and relatively high hardness in comparison to alumina. Polymer/magnesium composites are being developed to improve mechanical properties as well as retain polymer's property of degradation. Recent advances in orthobiologics are proving interesting as well. This paper thus deals with the latest improvements being made to the existing implant materials and includes new materials being introduced in the field of biomaterials.

Where bone meets implant: the characterization of nano-osseointegration

The recent application of electron tomography to the study of biomaterial interfaces with bone has brought about an awareness of nano-osseointegration and, to a further extent, demanded increasingly advanced characterization methodologies. In this study, nanoscale osseointegration has been studied via laser-modified titanium implants. The micro- and nano-structured implants were placed in the proximal tibia of New Zealand white rabbits for six months. High-resolution transmission electron microscopy (HRTEM), analytical microscopy, including energy dispersive X-ray spectroscopy (EDXS) and energy-filtered TEM (EFTEM), as well as electron tomography studies were used to investigate the degree of nano-osseointegration in two- and three-dimensions. HRTEM indicated the laser-modified surface encouraged the formation of crystalline hydroxyapatite in the immediate vicinity of the implant. Analytical studies suggested the presence of a functionally graded interface at the implant surface, characterized by the gradual intermixing of bone with oxide layer. Yet, the most compelling of techniques, which enabled straightforward visualization of nano-osseointegration, proved to be segmentation of electron tomographic reconstructions, where thresholding techniques identified bone penetrating into the nanoscale roughened surface features of laser-modified titanium. Combining high-resolution, analytical and three-dimensional electron microscopy techniques has proven to encourage identification and understanding of nano-osseointegration.

Design features of implants for direct skeletal attachment of limb prostheses

In direct skeletal attachment (DSA) of limb prostheses, a construct is implanted into an amputee's residuum bone and protrudes out of the residuum's skin. This technology represents an alternative to traditional suspension of prostheses via various socket systems, with clear indications when the sockets cannot be properly fitted. Contemporary DSA was invented in the 1990s, and several implant systems have been introduced since then. The current review is intended to compare the design features of implants for DSA whose use in humans or in animal studies has been reported in the literature.

Bone-titanium oxide interface in humans revealed by transmission electron microscopy and electron tomography

Osseointegration, the direct contact between an implant surface and bone tissue, plays a critical role in interfacial stability and implant success. Analysis of interfacial zones at the micro- and nano-levels is essential to determine the extent of osseointegration. In this paper, a series of state-of-the-art microscopy techniques are used on laser-modified implants retrieved from humans. Partially laser-modified implants were retrieved after two and a half months' healing and processed for light and electron microscopy. Light microscopy showed osseointegration, with bone tissue growing both towards and away from the implant surface. Transmission electron microscopy revealed an intimate contact between mineralized bone and the laser-modified surface, including bone growth into the nano-structured oxide. This novel observation was verified by three-dimensional Z-contrast electron tomography, enabling visualization of an apatite layer, with different crystal direction compared with the apatite in the bone tissue, encompassing the nano-structured oxide. In conclusion, the present study demonstrates the nano-scale osseointegration and bonding between apatite and surface-textured titanium oxide. These observations provide novel data in human specimens on the ultrastructure of the titanium-bone interface.

Biomechanical, histological and ultrastructural analyses of laser micro- and nano-structured titanium implant after 6 months in rabbit

Short-term, experimental studies of partly laser-modified implants with nano-scale surface topographical features have recently shown a considerable increase in the biomechanical anchorage to bone. The aim of this study is to evaluate the biomechanical and bone-bonding ability of partly laser-modified implants compared with machined implants after a healing period of 6 months in a rabbit model. The results showed a 170% increase in removal torque. Histology and scanning electron microscopy demonstrated osseointegration for both implant types, but also revealed a different fracture pattern at the interface and in the bone. Transmission electron microscopy and chemical analysis showed coalescence between mineralized tissue and the nano-structured surface of the laser modified implant. Taken together, the results indicate that nano-structured surfaces promote in vivo long-term bone bonding and interface strength.

Preparation of superhydrophilic microrough titanium implant surfaces by alkali treatment

A new strategy to render intrinsically hydrophobic microrough titanium implant surfaces superhydrophilic is reported, which is based on a rapid treatment with diluted aqueous sodium hydroxide solutions. The physicochemical characterization and protein interaction of the resulting superhydrophilic implant surfaces are presented. The superhydrophilicity of alkali treated microrough titanium substrates was mainly attributed to deprotonation and ion exchange processes in combination with a strong enhancement of wettability due to the roughness of the used substrates. Albeit these minor and mostly reversible chemical changes qualitative and quantitative differences between the protein adsorption on untreated and alkali treated microrough titanium substrates were detected. These differences in protein adsorption might account for the enhanced osseointegrative potential of superhydrophilic alkali treated microrough implant surfaces. The presented alkali treatment protocol represents a new clinically applicable route to superhydrophilic microrough titanium substrates by rendering the implant surface superhydrophilic "in situ of implantation".

Titanium oral implants: surface characteristics, interface biology and clinical outcome

Bone-anchored titanium implants have revolutionized oral healthcare. Surface properties of oral titanium implants play decisive roles for molecular interactions, cellular response and bone regeneration. Nevertheless, the role of specific surface properties, such as chemical and phase composition and nanoscale features, for the biological in vivo performance remains to be established. Partly, this is due to limited transfer of state-of-the-art preparation techniques to complex three-dimensional geometries, analytical tools and access to minute, intact interfacial layers. As judged by the available results of a few randomized clinical trials, there is no evidence that any particular type of oral implant has superior long-term success. Important insights into the recruitment of mesenchymal stem cells, cell-cell communication at the interface and high-resolution imaging of the interface between the surface oxide and the biological host are prerequisites for the understanding of the mechanisms of osseointegration. Strategies for development of the next generation of material surface modifications for compromised tissue are likely to include time and functionally programmed properties, pharmacological modulation and incorporation of cellular components.

Morphological studies on machined implants of commercially pure titanium and titanium alloy (Ti6Al4V) in the rabbit

The aim of this study was to evaluate the bone response to commercially pure titanium grade I and titanium alloy grade V (90% Ti, 6% Al, and 4% V, depicted Ti6Al4V) after 8 weeks in rabbit tibia. Interference microscopy and scanning electron microscopy were used for surface analyses. Transmission electron microscopy (TEM) was used for evaluation of surface crystallinity and chemistry after preparation of ultrathin sections using focused ion beam (FIB) microscopy. Three different embedding resins commonly used for histological preparation were evaluated with respect to adaptation to a turned implant surface. Epoxy Agar 100 resin and acrylic Technovit 7200 resin showed low separation while acrylic LR White resin showed large separation at the interface. The retrieved specimens were embedded in acrylic Technovit 7200 resin after fixation and dehydration. The histological evaluation revealed osseointegration for both c.p. titanium grade I and Ti6Al4V alloy, but no quantitative differences in bone contact and bone area were detected. Because a separation of implant and tissue occurred in the interface between implant and bone embedded in acrylic Technovit 7200 resin, additional factors related to implant surface properties and technical procedures are likely to influence the possibilities to prepare ultrathin sections by FIB.

On the way to total integration of prosthetic pylon with residuum

Two decades after introducing threaded titanium dental implants, Dr. Per-Ingvar Brånemark used a similar technique in the 1980s to pioneer the direct skeletal attachment (DSA) of limb prostheses. He and his colleagues used convincing clinical experience to overcome the skepticism of their peers, affording a new dimension of prosthetic rehabilitation to almost 100 individuals with amputation. As a result, more research has been initiated worldwide to move DSA to a level of greater safety, longevity, and reliability. This review highlights the trends and milestones in current DSA development. It also identifies ideas from previous studies in various fields that may be useful in future DSA development.

An appraisal of ultramicrotomy, FIBSEM and cryogenic FIBSEM techniques for the sectioning of biological cells on titanium substrates for TEM investigation

Ultramicrotomy, focused ion beam scanning electron microscopy (FIBSEM) and cryogenic FIBSEM (cryo-FIBSEM) techniques, as developed for the controlled cross-sectioning of mesenchymal stem cells (MSCs) and human osteoblasts (HObs) on titanium (Ti) substrates for transmission electron microscopy (TEM) investigation, are compared. Conventional ultramicrotomy has been used to section cells on Ti-foil substrates embedded in resin, but significant problems with cell detachment using this technique restricted its general applicability. Conventional FIBSEM 'lift-out' procedures were found to be effective for the preparation of uniform sections of fixed and dehydrated cell/Ti specimens, but the control of cell staining remains an issue. Cryo-FIBSEM procedures used with an 'H-bar' sample geometry enabled the sectioning of fixed and hydrated cell/Ti specimens, but issues remain over ion beam-induced artefacts and control of frost on the sample foils.