Cost effectiveness of osseointegration

Individuals with limb amputation fitted with conventional socket-suspended prostheses often experience socket-related discomfort leading to a significant decrease in quality of life. Bone-anchored prostheses are increasingly acknowledged as viable alternative method of attachment of artificial limb. In this case, the prosthesis is attached directly to the residual skeleton through a percutaneous fixation. To date, a few osseointegration fixations are commercially available. Several devices are at different stages of development particularly in Europe and the US. [1-15] Clearly, surgical procedures are currently blooming worldwide. Indeed, Australia and Queensland, in particular, have one of the fastest growing populations. Previous studies involving either screw-type implants or press-fit fixations for bone-anchorage have focused on biomechanics aspects as well as the clinical benefits and safety of the procedure. [16-25] In principle, bone-anchored prostheses should eliminate lifetime expenses associated with sockets and, consequently, potentially alleviate the financial burden of amputation for governmental organizations. Sadly, publications focusing on cost-effectiveness are sparse. In fact, only one study published by Haggstrom et al (2012), reported that “despite significantly fewer visits for prosthetic service the annual mean costs for osseointegrated prostheses were comparable with socket-suspended prostheses”.[26] Consequently, governmental organizations such as Queensland Artificial Limb Services (QALS) are facing a number of challenges while adjusting financial assistance schemes that should be fair and equitable to their clients fitted with bone-anchored prostheses. Clearly, more scientific evidence extracted from governmental databases is needed to further consolidate the analyses of financial burden associated with both methods of attachment (i.e., conventional sockets prostheses, bone-anchored prostheses). The purposes of the presentation will be: 1. To outline methodological avenues to assess the cost-effectiveness of bone-anchored prostheses compared to conventional sockets prostheses, 2. To highlight the potential obstacles and limitations in cost-effectiveness analyses of bone-anchored prostheses, 3. To present preliminary results of a cost-comparison analysis focusing on the comparison of the costs expressed in dollars over QALS funding cycles for both methods of attachment.

Osseointegration internationally: Australia is playing a key role?

Individuals with limb amputation fitted with conventional socket-suspended prostheses often experience socket-related discomfort leading to a significant decrease in quality of life. Bone-anchored prostheses are increasingly acknowledged as viable alternative method of attachment of artificial limb. In this case, the prosthesis is attached directly to the residual skeleton through a percutaneous fixation. To date, a few osseointegration fixations are commercially available. Several devices are at different stages of development particularly in Europe and the US.[1-15] Clearly, surgical procedures are currently blooming worldwide. Indeed, Australia and Queensland in particular have one of the fastest growing populations. Previous studies involving either screw-type implants or press-fit fixations for bone-anchorage have focused on fragmented biomechanics aspects as well as the clinical benefits and safety of the procedure. [16-25] However, very few publications have synthetized this information and provided an overview of the current developments in bone-anchored prostheses worldwide, let alone in Australia. The purposes of the presentation will be: 1. To provide an overview of the state-of-art developments in bone-anchored prostheses with as strong emphasis on the design of fixations, treatment, benefits, risks as well as future opportunities and challenges, 2. To present the current international developments of procedures for bone-anchored prostheses in terms of numbers of centers, number of cases and typical case-mix, 3. To highlight the current role Australia is playing as a leader worldwide in terms of growing population, broadest range of case-mix, choices of fixations, development of reimbursement schemes, unique clinical outcome registry for evidence-based practice, cutting-edge research, consumer demand and general public interest.

Osseointegration for limb loss: Can Australia play a key role?

Individuals with limb amputation fitted with conventional socket-suspended prostheses often experience socket related discomfort leading to a significant decrease in quality of life. Most of these concerns can be overcome by surgical techniques enabling bone-anchored prostheses. In this case, the prosthesis is attached directly to the residual skeleton through a percutaneous implant. The aim of this study is to present the current advances in these surgical techniques worldwide with a strong focus on the developments in Australia and Queensland.

Dynamic input to determine hip joint moments, power and work on the prosthetic limb of transfemoral amputees: ground reactions vs knee reactions

Study Design: Comparative analysis Background: Calculations of lower limbs kinetics are limited by floor-mounted force-plates. Objectives: Comparison of hip joint moments, power and mechanical work on the prosthetic limb of a transfemoral amputee calculated by inverse dynamics using either the ground reactions (force-plates) or knee reactions (transducer). Methods: Kinematics, ground reactions and knee reactions were collected using a motion analysis system, two force-plates and a multi-axial transducer mounted below the socket, respectively. Results: The inverse dynamics using ground reactions under-estimated the peaks of hip energy generation and absorption occurring at 63 % and 76 % of the gait cycle (GC) by 28 % and 54 %, respectively. This method over-estimated a phase of negative work at the hip (from 37 %GC to 56 %GC) by 24%. It under-estimated the phases of positive (from 57 %GC to 72 %GC) and negative (from 73 %GC to 98 %GC) work at the hip by 11 % and 58%, respectively. Conclusions: A transducer mounted within the prosthesis has the capacity to provide more realistic kinetics of the prosthetic limb because it enables assessment of multiple consecutive steps and a wide range of activities without issues of foot placement on force-plates. CLINICAL RELEVANCE The hip is the only joint that an amputee controls directly to set in motion the prosthesis. Hip joint kinetics are associated with joint degeneration, low back pain, risks of fall, etc. Therefore, realistic assessment of hip kinetics over multiple gait cycles and a wide range of activities is essential.

Review of direct measurement of inner prosthesis loading in transfemoral amputation: Potential benefits for evidence-based practice

The understanding of the load applied on the residuum through the prosthesis of individuals with transfemoral amputation (TFA) is essential to address a number of concerns that could strongly reduce their quality of life (e.g., residuum skin lesion, prosthesis fitting, alignment). This inner prosthesis loading could be estimated using a typical gait laboratory relying on inverse dynamics equations. Alternative, technological advances proposed over the last decade enabled direct measurement of this kinetic information in a broad variety of situations that could potentially be more relevant in clinical settings. The purposes of this presentation are (A) to review the literature about recent developments in measure and analyses of inner prosthesis loading of TFA, and (B) to extract information that could potentially contribute to a better evidence-based practice.

Bone-anchored prosthesis: Evidence that “gains” overcome the “pain”

Most of socket related discomforts leading to a significant decrease in quality of life of individuals with limb amputation can be overcome by surgical techniques enabling bone-anchored prostheses. To date, the OPRA two-stage procedure (i.e., S1, S2) is the most acknowledged treatment. However, surgical implantations of osseointegrated fixations are developing at an unprecedented pace worldwide.[1-18] Clearly, this option is becoming accessible to a wide range of individuals with limb amputations. The team led by Dr Rickard Branemark has published a number of landmark articles each focusing on a particular aspect (e.g., health related quality of life, functional outcomes, bone remodelling, infection rate). [1-3, 19-32] However, evidences presented in this prospective study are remarkable. Functional outcome, health-related quality of life and complications were considered concurrently for a large population (i.e., 51 participants) over an extended period of time (i.e., up to year follow up). Therefore, the “gain” and “pain” of the whole procedure were truly contrasted for the first time. The results confirmed that OPRA surgical and rehabilitation procedures improved significantly prosthetic use, mobility, global situation and fewer problems. Furthermore, the authors reported 47 episodes of infections for 63% (32) participants between post-op S1 and two years follow up. A total of 87% (41) were superficial infections recorded for 28 participants between post-op S2 and two years follow up, while 13% (6) were deep infections occurring for 4 participants during post-op S1 and S2. As expected, post-op S2 phase was the most prone to both infections. More importantly, the vast majority of infections were effectively treated with oral antibiotics. Clearly, this study provided definitive evidence that the benefits of OPRA fixation overcome complications. This article is also establishing reporting standards and benchmark data for future studies focusing on bone-anchored prostheses.

Safety of OPRA procedure for individuals with upper limb amputation

Surgical implantations of osseointegrated fixations for bone-anchored prosthesis are developing at an unprecedented pace worldwide while initial skepticism in the orthopedic community is slowly fading away. Clearly, this option is becoming accessible to a wide range of individuals with limb loss. [1-18] The team led by Dr Rickard Branemark has previously published a number of landmark articles focusing on the benefits and safety of the OPRA fixation mainly for individual with lower limb loss, particularly those with transfemoral amputation. [1-3, 19-32] However, similar information is lacking for those with upper limb amputation. This team is once again taking a leading role by sharing a retrospective study focusing on the implant survival, adverse events, implant stability, and bone remodelling for 18 individuals with transhumeral amputation over a 5-year post-operative period. Therefore, a comprehensive analysis of the safety of the procedure is accessible for the first time. In essence, the results showed an implant survival rate of 83% and 80% at 2 and 5 year follow ups, respectively. The most frequent adverse events were superficial skin infections that occurred for 28% (5) participants while the least frequent was deep bone infection that happened only once. More importantly, 38% of complications due to infections were effectively managed with nonoperative treatments (e.g., revision of skin penetration site, local cleaning, antibiotics, restriction of soft tissue mobility). Implant stability and bone remodelling were satisfactory. Clearly, this study provided better understanding of the safety of the OPRA surgical and rehabilitation procedure for individuals with upper limb amputation while establishing standards and benchmark data for future studies. However, strong evidences of the benefits are yet to be demonstrated. However, increase in health related quality of life and functional outcomes (e.g., range of movement) are likely. Altogether, the team of authors are providing further evidence that bone-anchored attachment is definitely a promising alternative to socket prostheses.

The cost and time effectiveness of osseointegration compared to the traditional socket prosthesis

Individuals with limb amputation fitted with conventional socket-suspended prostheses often experience socket related discomfort leading to a significant decrease in quality of life.[1-14] Most of these concerns can be overcome with osseointegration, a direct skeletal fixation method where the prosthetic componentry are directly attached to the fixation, resulting in the redundancy of the traditional socket system. There are two stages of osseointegration; Stage one, a titanium implant is inserted into the marrow space of residual limb bone and Stage two, a titanium extension is attached to the fixture. This surgical procedure is currently blooming worldwide, particularly within Queensland. Whilst providing improvements in quality of life, this new method also has potential to minimise the cost required for an amputee to ambulate during daily living. Thus, the aim of this project was to compare the differences in mean cost of services, cost of componentry and labour hours when using osseointegration compared to traditional socket-based prostheses. Data were extracted from Queensland Artificial Limb Services (QALS) database to determine cost of services, type of services and labour hours required to maintain a prosthetic limb. Five trans-femoral amputee male participants (age 46.4±10.1 yrs; height 175.4±16.3 cm; mass 83.8±14.0 kg; time since second stage 22.0± 8.1 mths) met inclusion criteria which was patient had to be more than 12 months post stage two osseointegration procedure. The socket and osseointegration prosthesis variables examined were the mean hours of labour, mean cost of services and mean cost of prosthetic componentry. Statistical analyses were conducted using an ANOVA. The results identified that there were only significant differences in the number of labour hours (p = 0.005) and cost of services (p = 0.021) when comparing the socket and osseointegration prosthetic type. These results identified that the cost of componentry were comparable between the two methods.

The ultrastructural relationship between osteocytes and dental implants following osseointegration

Background Osteocytes, the most abundant cells in bone, havemultiple functions, including acting as mechanosensors and regulating mineralization. It is clear that osteocytes influence bone remodeling by controlling the differentiation and activity of osteoblasts and osteoclasts. Determining the relationship between titanium implants and osteocytes may therefore benefit our understanding of the process of osseointegration. Purpose The aim of this study was to visualize the ultrastructural relationship between osteocytes and the titanium implant surface following osseointegration in vivo. Materials and Methods Titanium implants were placed in the maxillary molar regions of eight female Sprague Dawley rats, 3 months old. The animals were sacrificed 8 weeks after implantation, and undecalcified tissue sections were prepared. Resin-cast samples were subsequently acid-etched with 37% phosphoric acid prior to examination using scanning electron microscopy. Results Compared with mature bone, where the osteocytes were arranged in an ordered fashion, the osteocytes appeared less organized in the newly formed bone around the titanium implant. Further, a layer of mineralization with few organic components was observed on the implant surface. This study shows for the first time that osteocytes and their dendrites are directly connected with the implant surface. Conclusions: This study shows the direct anchorage of osteocytes via dendritic processes to a titanium implant surface in vivo. This suggests an important regulatory role for osteocytes and their lacunar-canalicular network in maintaining long-term osseointegration.

Clinoenstatite coatings have high bonding strength, bioactive ion release, and osteoimmunomodulatory effects that enhance in vivo osseointegration

A number of coating materials have been developed over past two decades seeking to improve the osseointegration of orthopedic metal implants. Despite the many candidate materials trialed, their low rate of translation into clinical applications suggests there is room for improving the current strategies for their development. We therefore propose that the ideal coating material(s) should possess the following three properties: (i) high bonding strength, (ii) release of functional ions, and (iii) favourable osteoimmunomodulatory effects. To test this proposal, we developed clinoenstatite (CLT, MgSiO3), which as a coating material has high bonding strength, cytocompability and immunomodulatory effects that are favourable for in vivo osteogenesis. The bonding strength of CLT coatings was 50.1 ± 3.2 MPa, more than twice that of hydroxyapatite (HA) coatings, at 23.5 ± 3.5 MPa. CLT coatings released Mg and Si ions, and compared to HA coatings, induced an immunomodulation more conducive for osseointegration, demonstrated by downregurelation of pro-inflammatory cytokines, enhancement of osteogenesis, and inhibition of osteoclastogenesis. In vivo studies demonstrated that CLT coatings improved osseointegration with host bone, as shown by the enhanced biomechanical strength and increased de novo bone formation, when compared with HA coatings. These results support the notion that coating materials with the proposed properties can induce an in vivo environment better suited for osseointegration. These properties could, therefore, be fundamental when developing high-performance coating materials.

The effects of osteoporosis on osseointegration in the rat maxilla

The study investigated the effects of oestrogen deficiency on dental implant in a rat model. An osteoporosis rat model was successfully established for dental implant research and it was noted that bone cells functioned differently in osteoporotic condition during the healing of dental implant. The study further demonstrated that implant surface roughness could stimulate bone formation, therefore, improve the bone healing in osteoporotic condition.

Transcutaneous bone-anchoring prosthesis with hip replacement: A novel treatment for amputees

Background Over the last two decades, Transcutaneous Bone-Anchored Prosthesis (TCBAP) has proven to be an effective alternative for prosthetic attachment for above knee amputees, particularly for individuals suffering from socket interface related complications. [1-17] Amputees with a very short femoral residuum (<15 cm) are at a considerable higher risk for these complications as well as high risk of implant failure, if they underwent a typical TCBAP due to the relatively small bony-implant contact leading to a need of a novel technique. Aim A. To describe the surgical procedure combining THR with TCBAP for the first time; and B. To present preliminary data on potential risks and benefits with assessment of clinical and functional outcomes at follow up Method We used a TCBAP connected to the stem of a Total Hip Replacement (THR) prosthesis enabling the femoral residuum and the hip joint to act as weight sharing structures by transferring the load directly to the pelvis. We performed a tri-polar THR connected to a custom made TCBAP at the first stage followed by creating a skin implant interface as a second stage. We retrospectively reviewed three cases of transfemoral amputations presenting with extremely short femoral residuum. Patients were assessed clinically and functionally including standard measures of health-related quality of life, amputee mobility predictor tool, ambulation tests and actual activity level. Progress was monitored for 6-24 months. Results Clinical outcomes including adverse events show no major complications. Functional outcomes improved for all participants as early as 6 months follow up. All cases were wheelchair bound preoperatively (K0 – AMPRO) improved to walking with One stick (K3 – AMPRO) at 3 months follow up. Discussion & Conclusion THR and TCBAP were combined for the first time in this proof-of-concept case series. The preliminary outcomes indicated that this procedure is potentially a safe and effective alternative despite the theoretical increase in risk of ascending infection through the skin-implant interface to the external environment for this patient group. We suggest larger comparative series to further validate these results.

Errors in the knee joint forces and moments during gait depending on the foot and knee prosthetic components

Background Previously studies showed that inverse dynamics based on motion analysis and force-plate is inaccurate compared to direct measurements for individuals with transfemoral amputation (TFA). Indeed, direct measurements can appropriately take into account the absorption at the prosthetic foot and the resistance at the prosthetic knee. [1-3] However, these studies involved only a passive prosthetic knee. Aim The objective of the present study was to investigate if different types of prosthetic feet and knees can exhibit different levels of error in the knee joint forces and moments. Method Three trials of walking at self-selected speed were analysed for 9 TFAs (7 males and 2 females, 47±9 years old, 1.76±0.1 m 79±17 kg) with a motion analysis system (Qualisys, Goteborg, Sweden), force plates (Kitsler, Winterthur, Switzerland) and a multi-axial transducer (JR3, Woodland, USA) mounted above the prosthetic knee [1-17]. TFAs were all fitted with an osseointegrated implant system. The prostheses included different type of foot (N=5) and knee (N=3) components. The root mean square errors (RMSE) between direct measurements and the knee joint forces and moments estimated by inverse dynamics were computed for stance and swing phases of gait and expressed as a percentage of the measured amplitudes. A one-way Kruskal-Wallis ANOVA was performed (Statgraphics, Levallois-Perret, France) to analyse the effects of the prosthetic components on the RMSEs. Cross-effects and post-hoc tests were not analysed in this study. Results A significant effect (*) was found for the type of prosthetic foot on anterior-posterior force during swing (p=0.016), lateral-medial force during stance (p=0.009), adduction-abduction moment during stance (p=0.038), internal-external rotation moment during stance (p=0.014) and during swing (p=0.006), and flexion-extension moment during stance (p = 0.035). A significant effect (#) was found for the type of prosthetic knee on anterior-posterior force during swing (p=0.018) and adduction-abduction moment during stance (p=0.035). Discussion & Conclusion The RMSEs were larger during swing than during stance. It is because the errors on accelerations (as derived from motion analysis) become substantial with respect to the external loads. Thus, inverse dynamics during swing should be analysed with caution because the mean RMSEs are close to 50%. Conversely, there were fewer effects of the prosthetic components on RMSE during swing than during stance and, accordingly, fewer effects due to knees than feet. Thus, inverse dynamics during stance should be used with caution for comparison of different prosthetic components.

Evolution in design of integral leg prosthesis leads to improved outcomes

Developments of surgical attachments for bone-anchored prostheses are slowly but surely winning over the initial disbelief in the orthopedic community. Clearly, this option is becoming accessible to a wide range of individuals with limb loss. Seminal studies have demonstrated that the pioneering procedure relying on screw-type fixation engenders major clinical benefits and acceptable safety. The surgical procedure for press-fit implants, such as the Integral-Leg-Prosthesis (ILP) has been described Dr Aschoff and his team. Some clinical benefits of press-fit implants have been also established. Here, his team is once again taking a leading role by sharing the progression over 15 years of the rate of deep infections for 69 individuals with transfemoral amputation fitted with three successive refined versions of the ILP. By definition, a double-blind randomized clinical trial to test the effect of different fixation’s design is difficult. Alternatively, Juhnke and colleagues are reporting the outcomes of action-research study for a cohort of participants. The first and foremost important outcome of this study is the confirmation that the current design of the IPL and rehabilitation program are altogether leading to an acceptable rate of deep infection and other adverse events (e.g., structural failure of implant, periprosthetic factures). This study is also providing a strong insight onto the effect of major phases in redesign of an implant on the risk of infection. This is an important reminder that the development of a successful osseointegrated implant is unlikely to be immediate but the results of a learning curve made of empirical and sequential changes led by a reflective clinical practice. Clearly, this study provided better understanding of the safety of the ILP surgical and rehabilitation procedure while establishing standards and benchmark data for future studies focusing on design and infection of press-fit implants. Complementary observations of relationship between infection and cofounders such as loading of the prosthesis and prosthetic components used would be beneficial.Further definitive evidences of the clinical benefits with the latest design would be valuable, although an increase in health related quality of life and functional outcomes are likely to be confirmed. Altogether, the authors are providing compelling evidence that bone-anchored attachments particularly those relying on press-fit implants are an established alternative to socket prostheses.

The development of a component to improve the loading safety of bone-anchored prostheses

Use of socket prostheses Currently, for individuals with limb loss, the conventional method of attaching a prosthetic limb relies on a socket that fits over the residual limb. However, there are a number of issues concerning the use of a socket (e.g., blisters, irritation, and discomfort) that result in dissatisfaction with socket prostheses, and these lead ultimately a significant decrease in quality of life. Bone-anchored prosthesis Alternatively, the concept of attaching artificial limbs directly to the skeletal system has been developed (bone anchored prostheses), as it alleviates many of the issues surrounding the conventional socket interface.Bone anchored prostheses rely on two critical components: the implant, and the percutaneous abutment or adapter, which forms the connection for the external prosthetic system (Figure 1). To date, an implant that screws into the long bone of the residual limb has been the most common intervention. However, more recently, press-fit implants have been introduced and their use is increasing. Several other devices are currently at various stages of development, particularly in Europe and the United States. Benefits of bone-anchored prostheses Several key studies have demonstrated that bone-anchored prostheses have major clinical benefits when compared to socket prostheses (e.g., quality of life, prosthetic use, body image, hip range of motion, sitting comfort, ease of donning and doffing, osseoperception (proprioception), walking ability) and acceptable safety, in terms of implant stability and infection. Additionally, this method of attachment allows amputees to participate in a wide range of daily activities for a substantially longer duration. Overall, the system has demonstrated a significant enhancement to quality of life. Challenges of direct skeletal attachment However, due to the direct skeletal attachment, serious injury and damage can occur through excessive loading events such as during a fall (e.g., component damage, peri-prosthetic fracture, hip dislocation, and femoral head fracture). These incidents are costly (e.g., replacement of components) and could require further surgical interventions. Currently, these risks are limiting the acceptance of bone-anchored technology and the substantial improvement to quality of life that this treatment offers. An in-depth investigation into these risks highlighted a clear need to re-design and improve the componentry in the system (Figure 2), to improve the overall safety during excessive loading events. Aim and purposes The ultimate aim of this doctoral research is to improve the loading safety of bone-anchored prostheses, to reduce the incidence of injury and damage through the design of load restricting components, enabling individuals fitted with the system to partake in everyday activities, with increased security and self-assurance. The safety component will be designed to release or ‘fail’ external to the limb, in a way that protects the internal bone-implant interface, thus removing the need for restorative surgery and potential damage to the bone. This requires detailed knowledge of the loads typically experienced by the limb and an understanding of potential overload situations that might occur. Hence, a comprehensive review of the loading literature surrounding bone anchored prostheses will be conducted as part of this project, with the potential for additional experimental studies of the loads during normal activities to fill in gaps in the literature. This information will be pivotal in determining the specifications for the properties of the safety component, and the bone-implant system. The project will follow the Stanford Biodesign process for the development of the safety component.