Outcome of percutaneous osseointegrated prostheses for patients with unilateral transfemoral amputation at two-year follow-up

OBJECTIVE

To report outcomes regarding general and specific physical health-related quality of life of treatment with percutaneous osseointegrated prostheses.

DESIGN

Prospective 2-year case-control study.

SETTING

University hospital.

PARTICIPANTS

Individuals (N=39; mean age, 44 ± 12.4 y) with unilateral transfemoral amputation as a result of trauma (n=23), tumor (n=11), or other cause (n=5). At baseline, 33 of the 39 participants used socket-suspended prostheses.

INTERVENTION

Osseointegrated prosthesis.

MAIN OUTCOME MEASURES

Questionnaire for Persons with Transfemoral Amputation (Q-TFA), Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) physical functioning (PF) and physical component summary (PCS), SF-6D, and Physiological Cost Index (PCI).

RESULTS

At 2 years postimplantation, 6 of 7 Q-TFA scores improved (P<.0001) compared with baseline (prosthetic use, mobility, problem, global, capability, walking habits). The walking aid subscore did not improve (P=.327). Of the 39 participants, increased prosthesis use was reported by 26, same amount of use by 11, and less use by 2. Improvement was reported in 16 of the 30 separate problem items (P<.05). Unchanged items included problems regarding phantom limb pain and pain from the back, shoulders, and contralateral limb. The PF, PCS, and SF-6D improved a mean of 24.1 ± 21.4 (P<.0001), 8.5 ± 9.7 (P<.0001), and .039 ± .11 (P=.007) points, respectively. Walking energy cost decreased (mean PCI at baseline, .749; mean PCI at follow-up, .61; P<.0001).

CONCLUSIONS

Two years after intervention, patients with a unilateral TFA treated with an OPRA implant showed important improvements in prosthetic function and physical quality of life. However, walking aids used and the presence of phantom limb pain and pain in other extremities were unchanged. This information is valuable when considering whether percutaneous osseointegrated prostheses are a relevant treatment option.

Static load bearing exercises of individuals with transfemoral amputation fitted with an osseointegrated implant: reliability of kinetic data

This study aimed at presenting the intra-tester reliability of the static load bearing exercises (LBEs) performed by individuals with transfemoral amputation (TFA) fitted with an osseointegrated implant to stimulate the bone remodeling process. There is a need for a better understanding of the implementation of these exercises particularly the reliability. The intra-tester reliability is discussed with a particular emphasis on inter-load prescribed, inter-axis and inter-component reliabilities as well as the effect of body weight normalization. Eleven unilateral TFAs fitted with an OPRA implant performed five trials in four loading conditions. The forces and moments on the three axes of the implant were measured directly with an instrumented pylon including a six-channel transducer. Reliability of loading variables was assessed using intraclass correlation coefficients (ICCs) and percentage standard error of measurement values ( %SEMs ). The ICCs of all variables were above 0.9 and the %SEM values ranged between 0 and 87%. This study showed a high between-participants' variance highlighting the lack of loading consistency typical of symptomatic population as well as a high reliability between the loading sessions indicating a plausible correct repetition of the LBE by the participants. However, these outcomes must be understood within the framework of the proposed experimental protocol.

Bacteria-material surface interactions: methodological development for the assessment of implant surface induced antibacterial effects

The choice of material for implanted prostheses is of great importance concerning bacterial colonization and biofilm formation. Consequently, methods to investigate bacterial behavior are needed in order to develop new infection resistant surfaces. In this study, different methodological setups were used to evaluate the antimicrobial effect of photocatalytic titanium oxide and silver surfaces. Biofilm formation and eradication under static and dynamic culture conditions were studied with the use of the following analytical techniques: viable colony-forming unit (CFU) counting, imprinting, fluorescence, and bioluminescence. The present study demonstrates that different methods are needed in order to evaluate the prophylactic and treatment effects on planktonic and biofilm bacteria and to assess the antimicrobial effect of different surface treatments/coatings. Choosing the right antibacterial testing model for the specific application is also of great importance. Both in situ approaches and indirect methods provide valuable complementary information.

Treatment of phantom limb pain (PLP) based on augmented reality and gaming controlled by myoelectric pattern recognition: a case study of a chronic PLP patient

A variety of treatments have been historically used to alleviate phantom limb pain (PLP) with varying efficacy. Recently, virtual reality (VR) has been employed as a more sophisticated mirror therapy. Despite the advantages of VR over a conventional mirror, this approach has retained the use of the contralateral limb and is therefore restricted to unilateral amputees. Moreover, this strategy disregards the actual effort made by the patient to produce phantom motions. In this work, we investigate a treatment in which the virtual limb responds directly to myoelectric activity at the stump, while the illusion of a restored limb is enhanced through augmented reality (AR). Further, phantom motions are facilitated and encouraged through gaming. The proposed set of technologies was administered to a chronic PLP patient who has shown resistance to a variety of treatments (including mirror therapy) for 48 years. Individual and simultaneous phantom movements were predicted using myoelectric pattern recognition and were then used as input for VR and AR environments, as well as for a racing game. The sustained level of pain reported by the patient was gradually reduced to complete pain-free periods. The phantom posture initially reported as a strongly closed fist was gradually relaxed, interestingly resembling the neutral posture displayed by the virtual limb. The patient acquired the ability to freely move his phantom limb, and a telescopic effect was observed where the position of the phantom hand was restored to the anatomically correct distance. More importantly, the effect of the interventions was positively and noticeably perceived by the patient and his relatives. Despite the limitation of a single case study, the successful results of the proposed system in a patient for whom other medical and non-medical treatments have been ineffective justifies and motivates further investigation in a wider study.

A novel osseointegrated percutaneous prosthetic system for the treatment of patients with transfemoral amputation

Patients with transfemoral amputation (TFA) often experience problems related to the use of socket-suspended prostheses. The clinical development of osseointegrated percutaneous prostheses for patients with a TFA started in 1990, based on the long-term successful results of osseointegrated dental implants.

Between1999 and 2007, 51 patients with 55 TFAs were consecutively enrolled in a prospective, single-centre non-randomised study and followed for two years. The indication for amputation was trauma in 33 patients (65%) and tumour in 12 (24%). A two-stage surgical procedure was used to introduce a percutaneous implant to which an external amputation prosthesis was attached. The assessment of outcome included the use of two self-report questionnaires, the Questionnaire for Persons with a Transfemoral Amputation (Q-TFA) and the Short-Form (SF)-36.

The cumulative survival at two years’ follow-up was 92%. The Q-TFA showed improved prosthetic use, mobility, global situation and fewer problems (all p < 0.001). The physical function SF-36 scores were also improved (p < 0.001). Superficial infection was the most frequent complication, occurring 41 times in 28 patients (rate of infection 54.9%). Most were treated effectively with oral antibiotics. The implant was removed in four patients because of loosening (three aseptic, one infection).

Osseointegrated percutaneous implants constitute a novel form of treatment for patients with TFA. The high cumulative survival rate at two years (92%) combined with enhanced prosthetic use and mobility, fewer problems and improved quality of life, supports the ‘revolutionary change’ that patients with TFA have reported following treatment with osseointegrated percutaneous prostheses.

Cite this article: Bone Joint J 2014;96-B:106–13.

Load applied on bone-anchored transfemoral prosthesis: characterization of a prosthesis-a pilot study

The objectives of this study were to (1) record the inner-prosthesis loading during activities of daily living (ADLs), (2) present a set of variables comparing loading data, and (3) provide an example of characterization of two prostheses. The load was measured at 200 Hz using a multi-axial transducer mounted between the residuum and the knee of an individual with unilateral transfemoral amputation fitted with a bone-anchored prosthesis. The load was measured while using two different prosthetic knees, mechanical (PRO1) and micro processor-controlled (PRO2), during six ADLs. The characterization of the prostheses was achieved using a set of variables split into four categories, including temporal characteristics, maximum loading, loading slopes, and impulse. Approximately 360 gait cycles were analyzed for each prosthesis. PRO1 showed a cadence improved by 19% and 7%, a maximum force on the long axis reduced by 11% and 19%, and an impulse reduced by 32% and 15% during descent of incline and stairs compared with PRO2, respectively. This work confirmed that the proposed apparatus and characterization can reveal how changes of prosthetic components are translated into inner-prosthetic loading.

BioPatRec: A modular research platform for the control of artificial limbs based on pattern recognition algorithms

Background

Processing and pattern recognition of myoelectric signals have been at the core of prosthetic control research in the last decade. Although most studies agree on reporting the accuracy of predicting predefined movements, there is a significant amount of study-dependent variables that make high-resolution inter-study comparison practically impossible. As an effort to provide a common research platform for the development and evaluation of algorithms in prosthetic control, we introduce BioPatRec as open source software. BioPatRec allows a seamless implementation of a variety of algorithms in the fields of (1) Signal processing; (2) Feature selection and extraction; (3) Pattern recognition; and, (4) Real-time control. Furthermore, since the platform is highly modular and customizable, researchers from different fields can seamlessly benchmark their algorithms by applying them in prosthetic control, without necessarily knowing how to obtain and process bioelectric signals, or how to produce and evaluate physically meaningful outputs.

Results

BioPatRec is demonstrated in this study by the implementation of a relatively new pattern recognition algorithm, namely Regulatory Feedback Networks (RFN). RFN produced comparable results to those of more sophisticated classifiers such as Linear Discriminant Analysis and Multi-Layer Perceptron. BioPatRec is released with these 3 fundamentally different classifiers, as well as all the necessary routines for the myoelectric control of a virtual hand; from data acquisition to real-time evaluations. All the required instructions for use and development are provided in the online project hosting platform, which includes issue tracking and an extensive “wiki”. This transparent implementation aims to facilitate collaboration and speed up utilization. Moreover, BioPatRec provides a publicly available repository of myoelectric signals that allow algorithms benchmarking on common data sets. This is particularly useful for researchers lacking of data acquisition hardware, or with limited access to patients.

Conclusions

BioPatRec has been made openly and freely available with the hope to accelerate, through the community contributions, the development of better algorithms that can potentially improve the patient’s quality of life. It is currently used in 3 different continents and by researchers of different disciplines, thus proving to be a useful tool for development and collaboration.

On the viability of implantable electrodes for the natural control of artificial limbs: review and discussion

The control of robotic prostheses based on pattern recognition algorithms is a widely studied subject that has shown promising results in acute experiments. The long-term implementation of this technology, however, has not yet been achieved due to practical issues that can be mainly attributed to the use of surface electrodes and their highly environmental dependency. This paper describes several implantable electrodes and discusses them as a solution for the natural control of artificial limbs. In this context "natural" is defined as producing control over limb movement analogous to that of an intact physiological system. This includes coordinated and simultaneous movements of different degrees of freedom. It also implies that the input signals must come from nerves or muscles that were originally meant to produce the intended movement and that feedback is perceived as originating in the missing limb without requiring burdensome levels of concentration. After scrutinizing different electrode designs and their clinical implementation, we concluded that the epimysial and cuff electrodes are currently promising candidates to achieving a long-term stable and natural control of robotic prosthetics, provided that communication from the electrodes to the outside of the body is guaranteed.

Stable fixation of an osseointegated implant system for above-the-knee amputees: titel RSA and radiographic evaluation of migration and bone remodeling in 55 cases

BACKGROUND AND PURPOSE

Rehabilitation of patients with transfemoral amputations is particularly difficult due to problems in using standard socket prostheses. We wanted to assess long-term fixation of the osseointegrated implant system (OPRA) using radiostereometric analysis (RSA) and periprosthetic bone remodeling.

METHODS

51 patients with transfemoral amputations (55 implants) were enrolled in an RSA study. RSA and plain radiographs were scheduled at 6 months and at 1, 2, 5, 7, and 10 years after surgery. RSA films were analyzed using UmRSA software. Plain radiographs were graded for bone resorption, cancellization, cortical thinning, and trabecular streaming or buttressing in specifically defined zones around the implant.

RESULTS

At 5 years, the median (SE) migration of the implant was -0.02 (0.06) mm distally. The rotational movement was 0.42 (0.32) degrees around the longitudinal axis. There was no statistically significant difference in median rotation or migration at any follow-up time. Cancellization of the cortex (plain radiographic grading) appeared in at least 1 zone in over half of the patients at 2 years. However, the prevalence of cancellization had decreased by the 5-year follow-up.

INTERPRETATION

The RSA analysis for the OPRA system indicated stable fixation of the implant. The periprosthetic bone remodeling showed similarities with changes seen around uncemented hip stems. The OPRA system is a new and promising approach for addressing the challenges faced by patients with transfemoral amputations.

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.

Osseointegration amputation prostheses on the upper limbs: methods, prosthetics and rehabilitation

BACKGROUND

The osseointegration programme for upper extremity amputation started in Sweden in 1990, when a titanium fixture was first implanted into a thumb. This method has since been used for transhumeral and below-elbow amputation. The treatment involves two surgical procedures. During the first a titanium fixture is surgically attached to the skeleton, and a second procedure six months later involves a skin penetrating abutment to which the prosthesis is attached.

OBJECTIVES

To describe the osseointegration procedure for surgery, prosthetics and rehabilitation.

METHODS

Patients with short stumps and previous problems with prosthetic fitting were selected. From 1990 to April 2010, 37 upper limb cases were treated and fitted with prosthesis: 10 thumbs, 1 partial hand, 10 transradial and 16 transhumeral amputations. Of these, 7 patients are currently not prosthetic users.

RESULTS

Patients indicated that function and quality of life had improved since osseointegration.

CONCLUSION

Osseointegration is an important platform for present and future prosthetic technology. The prosthetic situation is improved due to the stable fixation, freedom of motion and functionality.

CLINICAL RELEVANCE

The two-stage osseointegration procedure has the potential to change the rehabilitation strategy for selected upper limb amputees. The method eliminates the need for a socket and the prosthesis will always fit. The stable prosthetic fixation and increased freedom of motion generates improved function. Specially designed components and rehabilitation procedures have been developed.

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.

Osseointegrated titanium implants for limb prostheses attachments: infectious complications

BACKGROUND

The concept of osseointegration involves direct contact between titanium implant and bone. This transcutaneous prosthetic system for amputees is intended to assure stable long-term fixation. Most metal transcutaneous implants have failed, primarily owing to infection.

QUESTIONS/PURPOSES

We determined the frequency and describe the presentation of infectious complications with this novel method. We also evaluated the bacterial flora at the skin-penetration area and its relation to the development of local and implant-related infection.

PATIENTS AND METHODS

We prospectively followed 39 patients with arm and leg amputations fitted with transcutaneous osseointegrated titanium implants a mean of 56 months earlier (range, 132-133 months). There were 33 femoral, one tibial, four ulnar, four radial, and three humeral implants. Patients were selected during a 6-month period in 2005 and identically reevaluated after 3 years. Implant infection was defined as definite, probable, or possible based on clinical, radiologic, and microbiologic evidence.

RESULTS

The frequency of implant infection was 5% at inclusion and 18% at followup. One patient with infection recovered owing to antibiotic treatment and another patient had the implant removed. Most implant infections had low infectious activity, and in five of the seven patients with infections, prosthetic use was not affected. The most common bacteria in superficial and deep cultures were Staphylococcus aureus and coagulase-negative staphylococci.

CONCLUSIONS

Despite frequent colonization around the skin-implant interface by potentially virulent bacteria such as Staphylococcus aureus and bacteria associated with biomedical device infections such as coagulase-negative staphylococci, this titanium implant system for bone-anchored prostheses caused few infections leading to disability or implant removal.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Biomechanical, histological, and ultrastructural analyses of laser micro- and nano-structured titanium alloy implants: a study in rabbit

The aim of this study was to evaluate the biomechanical properties and ultrastructure of the bone response of partly laser-modified Ti6Al4V implants compared with turned, machined implants after 8 weeks in rabbit. The surface analyses performed with interference microscopy and electron microscopy showed increased surface topography with micro- and nano-sized surface features as well as increased oxide thickness of the modified surface. The biomechanical testing demonstrated a 270% increase in torque value for the surface modified implants compared with the control implants. Histological evaluation of ground sections of specimens subjected to biomechanical testing revealed ongoing bone formation and remodeling. A histological feature exclusively observed at the laser-modified surface was the presence of fracture in the mineralized bone rather than at the interface between the bone and implant. Transmission electron microscopy (TEM) was performed on Focused Ion Beam (FIB) prepared samples of the intact bone-implant interface, demonstrating a direct contact between nanocrystalline hydroxyapatite and the oxide of the laser-modified implant surface. In conclusion, laser-modified titanium alloy implants have significantly stronger bone anchorage compared with machined implants and show no adverse tissue reactions.

Load on osseointegrated fixation of a transfemoral amputee during a fall: loading, descent, impact and recovery analysis

Falling represents a health risk for lower limb amputees fitted with an osseointegrated fixation mainly because of the potential damage to the fixation. The purpose of this study was to characterize a real forward fall that occurred inadvertently to a transfemoral amputee fitted with an osseointegrated fixation while attending a gait measurement session to assess the load applied on the residuum. The objective was to analyze the load applied on the fixation with an emphasis on the sequence of events, the pattern and the magnitude of the forces and moments. The load was measured directly at 200 Hz using a six-channel transducer. Complementary video footage was also studied. The fall was divided into four phases: Loading (240 ms), descent (620 ms), impact (365 ms) and recovery (2495 ms). The main impact forces and moments occurred 870 ms and 915 ms after the heel contact, and corresponded to 133% BW and 17 % BWm, or 1.2 and 11.2 times the maximum forces and moments applied during the previous steps of the participant, respectively. This study provided key information to engineers and clinicians facing the challenge to design equipment, and rehabilitation and exercise programs to restore safely the locomotion of lower limb amputees.

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.

[A new method for prosthetisation of vascular patients with lower limb amputation: initial experiences with osseointegration technique]

INTRODUCTION/AIMS

Prostheses use for lower limb amputees is difficult, while the socket is hard, the prosthesis is heavy. Drawbacks of conventional prosthesis are mainly associated with the socket, therefore osseointegration technique is a promising solution, since it doesn't require a socket. Our aim was to introduce this technique in Hungary and extend indication for vascular patients.

METHODS

The method includes two operative and one rehabilitation phases: during first operation a titanium screw is fixed into the femoral bone marrow cavity, this connects to an abutment, which also penetrates the skin, making a direct connection between the femur and the prosthesis during the second intervention. During rehabilitation the patient makes loading exercises and learns to walk with new prosthesis.

RESULTS

This method was launched in Hungary in 2005. Two female amputees were operated on initially, their second surgery was performed in 2006 (when titanium screw was applied in the male patients, as well). Incorporation of titanium screw was exquisite, and rehabilitation was successful. One of our male patients died eight months after his first operation due to myocardial infarction.

CONCLUSION

Based on our experiences, the osseointegration technique facilitates rehabilitation of vascular patients for prostheses use. Adequate follow-up and stable vascular diseases are not contraindications, although further clinical trials are needed to determine its indication.

Physiological cost index (PCI) and walking performance in individuals with transfemoral prostheses compared to healthy controls

PURPOSE

Uncomplicated methods for evaluation of prosthetic walking performance for individuals with lower limb amputations are valuable. The Physiological Cost Index (PCI), the comfortable walking speed (CWS) and self-reported walking distances are three examples of such measures. The aim was to obtain values for these measures for individuals walking with transfemoral prostheses and to compare the results with healthy controls.

METHOD

Individuals with an established transfemoral amputation for reasons other than vascular disease (TFA-group, n = 41, 30 male/11 female, mean age 49, SD 11.5) were compared to age-and gender matched healthy controls (Healthy group, n = 22). PCI was assessed walking in CWS for 5 min and self-reported distances accomplished outdoors was assessed with the Walking Habit Score (0 - 100).

RESULTS

Mean PCI was 0.55 (SD 0.19) in the TFA-group and 0.31 (SD 0.09) in the Healthy group (p < 0.001). The CWS was 62 (SD 12.6) and 90 (SD 12.8) m/min and the Walking Habit Score 48 (SD 19) and 74 (SD 16) score-points respectively (p < 0.001).

CONCLUSIONS

By using uncomplicated and inexpensive methods, this study shows that walking with transfemoral prostheses is done with considerably increased energy cost, slower CWS and that limited walking distances outdoors are performed compared to healthy controls.

One hundred patients treated with osseointegrated transfemoral amputation prostheses--rehabilitation perspective

Treatment with osseointegrated transfemoral prostheses has been shown to improve quality of life. The treatment has been performed in Sweden since 1990 and consists of two surgical procedures followed by rehabilitation. During the first years, the rehabilitation process was not standardized. In 1999, a treatment protocol called OPRA (Osseointegrated Prostheses for the Rehabilitation of Amputees) was established. This article describes the current rehabilitation protocol and illustrates the overall results. The OPRA rehabilitation protocol is graded to stimulate the process of osseointegration and prepare the patient for unrestricted prosthetic use. It includes initial training with a short training prosthesis followed by gradually increased prosthetic activity. Between May 1990 and June 2008, we treated 100 patients with 106 implants (6 bilaterally; 61% males, 39% females; mean age 43 years; mean time since amputation 11.5 years.) The majority had amputations due to trauma (67%) or tumor (21%) (other = 12%). Currently, 68 patients are using their prostheses (follow-up: 3 months- 17.5 years) and 32 are not (4 are deceased, 7 are before second surgery, 6 are in initial training, 4 are not using prosthesis, and 11 had the implant removed). The majority of treatment failures occurred in patients before we established the OPRA protocol. The implementation of graded rehabilitation is considered to be of utmost importance for improved results.

FE stress analysis of the interface between the bone and an osseointegrated implant for amputees--implications to refine the rehabilitation program

BACKGROUND

The direct anchorage of lower-limb prosthesis to the bone has been shown to be an excellent alternative for amputees experiencing complications in using a conventional prosthetic socket. During rehabilitation phase, amputees are asked to apply static loading on the abutment perpendicular to a weigh scale to prepare the bone to tolerate the forces likely to be developed during walking. The weigh scale measures only the vertical force. A different loading protocol can affect the bone-implant interface stresses and the outcome of the rehabilitation.

METHODS

This study developed a Finite Element model to study the stresses in the bone adjacent to the implant. Three loading conditions were applied based on the experimentally measured load: (1) vertical force applied along the long axis of the limb, corresponding to the load clinically prescribed in the weight bearing exercise; (2) loads applied on the three axes, corresponding to the "true" load measured simultaneously by a tri-axial load transducer during the same exercise; and (3) loads experienced during independent walking.

FINDINGS

The model revealed that the weigh scale might in fact be applying much higher and less uniform stresses on the bone than expected. During walking, high stress occurred at various locations of the implanted region, which was different from the patterns of stress distribution during weight bearing exercises.

INTERPRETATIONS

The difference in stress among three loading conditions implies that tri-axial load should be monitored during the weight bearing exercises and carefully prescribed.

Characterization of the surface properties of commercially available dental implants using scanning electron microscopy, focused ion beam, and high-resolution transmission electron microscopy

BACKGROUND

Since osseointegration of the respective implant is claimed by all manufacturing companies, it is obvious that not just one specific surface profile including the chemistry controls bone apposition.

PURPOSE

The purpose was to identify and separate out a particular set of surface features of the implant surfaces that can contribute as factors in the osseointegration process.

MATERIAL AND METHODS

The surface properties of several commercially available dental implants were extensively studied using profilometry, scanning electron microscopy, and transmission electron microscopy. Ultrathin sections prepared with focused ion beam microscopy (FIB) provided microstructural and chemical data which have not previously been communicated. The implants were the Nobel Biocare TiUnite (Nobel Biocare AB, Göteborg, Sweden), Nobel Biocare Steri-Oss HA-coated (Nobel Biocare AB, Yorba Linda, CA, USA), Astra-Tech OsseoSpeed (Astra Tech AB, Mölndal, Sweden), Straumann SLA (Straumann AG, Waldenburg, Switzerland), and the Brånemark Integration Original Fixture implant (Brånemark Integration, Göteborg, Sweden).

RESULTS

It was found that their surface properties had differences. The surfaces were covered with crystalline TiO(2) (both anatase and rutile), amorphous titanium oxide, phosphorus doped amorphous titanium oxide, fluorine, titanium hydride, and hydroxyapatite, respectively.

CONCLUSION

This indicates that the provision of osseointegration is not exclusively linked to a particular set of surface features if the implant surface character is a major factor in that process. The studied methodology provides an effective tool to also analyze the interface between implant and surrounding bone. This would be a natural next step in understanding the ultrastructure of the interface between bone and implants.