Static Load Bearing During Early Rehabilitation Of Transfemoral Amputees Using Osseointegrated Fixation

Many transfemoral amputees wearing conventional socket prostheses experience pain related to the socket-residuum interface and difficulties with socket retention or fit due to a short residuum. In consideration of these problems a direct skeletal fixation method has been developed whereby a titanium implant is screwed into the medullary canal of the residual femur. Prosthetic components are directly attached to the fixation, once osseointegrated, removing the need for a prosthetic socket. The rehabilitation program to return to ambulation involves incremental static loading of the fixation until full weight bearing is achieved. The rate of loading, which is intended to be isolated to the long axis of the fixation, is determined by the quality of the residual skeleton and a qualitative assessment of the pain experienced by the amputee on loading. Rotational loading of the implant is to be avoided at this stage. The amputee uses a domestic weigh-scale to provide feedback of the load applied. This study aims to measure the true load applied to the fixation and compare this with the clinically prescribed axial load

Osseointegrated Titanium Implants for Limb Prostheses Attachments: Infectious Complications

Femoral amputation is a devastating event. Percutaneous, bone anchored prosthetic systems reduce problems associated with socket suspended prostheses, but the design is inherently vulnerable to infection. The aims of this thesis were to determine the risk of implant-associated infection, bacterial biofilm properties and the functional impact using this implant treatment regime. Definition of implant related osteomyelitis was based on clinical signs, radiography and positive tissue cultures. In 3-year prospective study 39 patients were evaluated twice for infectious frequency, clinical presentation, and its relation to bacterial flora at the skin-implant interface (Paper 1). The frequency of implant infection was 5% at inclusion and 18% at follow-up. The most common bacteria in superficial, and deep cultures were Staphylococcus aureus and coagulase-negative staphylococci. Despite frequent colonization by potentially virulent bacteria, limited disability, and only one implant removal was found. Phenotypical and genotypical biofilm formation was determined in 13 (7 staphylococcal, 6 enterococcal) osteomyelitis strains (Paper II). Antimicrobial resistance was tested with a novel combination of the Calgary biofilm MBEC device, and a custom-made susceptibility MIC plate. The majority of the strains produced biofilm with increased antimicrobial resistance, compared to their planktonic counterparts. Slime producing strains tolerated higher antimicrobial concentrations compared to non-producers. All staphylococcal strains carried ica genes. The long-term risk of implant-associated infection, and its relation to patient and method specific factors was determined in a 20-year retrospective analysis of the first 96 femoral implant patients (102 implants) (Paper III). A 10-year cumulative risk of 20% for developing osteomyelitis (16 patients), and a 10-year cumulative risk of 9 % for implant extraction due to osteomyelitis (10 patients) was found. Antibiotic treatment (median 3.5 months) and selective minor debridement, with retained implants, cured 7 out of 18 patients at the 24- month follow-up (Paper IV). Six patients were cured after implant extraction, and 5 had chronic low-grade infections with stable implants, but variable use of the external prosthetic leg. The most common pathogens were S. aureus and E. faecalis. C-reactive protein serum levels were significantly higher in patients with osteomyelitis caused by S. aureus than other pathogens. It is concluded that the finding of an increased risk of osteomyelitis with time using this implant system calls for; i) careful patient selection and information of long term risks, ii) further studies on infection control, iii) consideration of biofilm in treatment, and iv) improved diagnostics, and antibiotic delivery

Design of a stepwise safety protocol for lower limb prosthetic risk management in a clinical investigation

In research on lower limb prostheses, safety during testing and training is paramount. Lower limb prosthesis users risk unintentional loss of balance that can result in injury, fear of falling, and overall decreased confidence in their prosthetic leg. Here, we present a protocol for managing the risks during evaluation of active prosthetic legs with modifiable control systems. We propose graded safety levels, each of which must be achieved before advancing to the next one, from laboratory bench testing to independent ambulation in real-world environments

Transfemoral amputation, Quality of Life and Prosthetic Function. Studies focusing on individuals with amputation due to reasons other than peripheral vascular disease, with socket or osseointegrated prostheses.

Background: Individuals who have undergone a transfemoral amputation (TFA) due to causes other than peripheral vascular disease (PVD) constitute a sub-group of all amputees. This group is usually of young age at the amputation. Conventionally, prosthetic suspension is achieved with a socket. Using the osseointegration method, prostheses can be attached directly to the bone (OI prostheses) without a socket. Aim: The overall aim was to investigate the health-related quality of life (HRQL) and prosthetic function in persons with a unilateral TFA, due to causes other than PVD, with socket prostheses and OI prostheses. Material, methods and results: General HRQL was assessed using the SF-36. For condition-specific HRQL, a new self-report questionnaire was constructed: the Questionnaire for Individuals with a Transfemoral Amputation (Q-TFA). It provides results for four scores (prosthetic use, prosthetic mobility, problems and global health) and adequate levels of validity and reliability were demonstrated (Paper II). Physical assessments included measurement of the energy cost using the Physiological Cost Index and hip range of motion (ROM). The HRQL and prosthetic function are described for 97 persons (62% male, 38% female, mean age 48 years, mean time since amputation 22 years, cause: 55% trauma, 35% tumour, 10% other) (Paper I). The energy cost was investigated for 41 individuals with socket prostheses (Paper III), while hip ROM was investigated for 43 persons with socket prostheses and 20 with OI prostheses (Paper IV). Finally, prospective results at the two-year follow-up for the first 18 consecutive patients treated with an OI prosthesis within a clinical investigation are reported (Paper V). For the study group (Paper I), the general HRQL was reduced compared with healthy norms. Daily use of the socket prosthesis was reported by 82%. A large number of subjective complaints reducing the HRQL were reported. The most common were heat/perspiration (72%) and sores/skin irritation (62%) with the socket. Further, 48% reported phantom limb pain, 47% back pain and 44% uncomfortable sitting with the prosthesis. The energy cost was increased by 77% compared with controls. The hip ROM was reduced with the socket prosthesis, while individuals with an OI prosthesis had no restriction in hip ROM. Prospective results for the treatment with OI prostheses revealed that 17/18 used the prosthesis and reported an increase in general physical HRQL and more prosthetic use, better prosthetic mobility, fewer problems and better global health at the two-year follow-up compared with the preoperative situation. Conclusions: For persons with an established TFA, for reasons other than PVD, the general HRQL is lower than that of healthy norms and a considerable number of specific problems are perceived. The Q-TFA is a valid and reliable tool for assessments of this population. Treatment with OI prostheses represents a promising development in the rehabilitation of individuals with TFA who report improved general and condition-specific HRQL at the two-year follow-up

Kinetics of Transfemoral Amputees with Osseointegrated Fixation Performing Common Activities of Daily Living

Background: Direct anchorage of a lower-limb prosthesis to the bone through an implanted fixation (osseointegration) has been suggested as an excellent alternative for amputees experiencing complications from use of a conventional socket-type prosthesis. However, an attempt needs to be made to optimize the mechanical design of the fixation and refine the rehabilitation program. Understanding the load applied on the fixation is a crucial step towards this goal. Methods: The load applied on the osseointegrated fixation of nine transfemoral amputees was measured using a load transducer, when the amputees performed activities which included straight-line level walking, ascending and descending stairs and a ramp as well as walking around a circle. Force and moment patterns along each gait cycle, magnitudes and time of occurrence of the local extrema of the load, as well as impulses were analysed. Findings: Managing a ramp and stairs, and walking around a circle did not produce a significant increase (P>0.05) in load compared to straight-line level walking. The patterns of the moment about the medio-lateral axis were different among the six activities which may reflect the different strategies used in controlling the prosthetic knee joint. Interpretations: This study increases the understanding of biomechanics of bone-anchored osseointegrated prostheses. The loading data provided will be useful in designing the osseointegrated fixation to increase the fatigue life and to refine rehabilitation protocol

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

The objectives of this study were (A) to record the inner prosthesis loading during activities of daily living (ADL), (B) to present a set of variables comparing loading data, and (C) to provide an example of characterisation 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 prostheses including a mechanically (PRO1) and a microprocessor controlled (PRO2) knee during six ADL. The characterisation of prosthesis 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 analysed for each prosthesis. PRO1 showed a cadence improved by 19% and 7%, a maximum force on the long axis reduced by 11% and 19%, as well as an impulse reduced by 32% and 15% during descent of incline and stairs compared to PRO2, respectively. This work confirmed that the proposed apparatus and characterisation can reveal how changes of prosthetic components are translated into inner loading

Direct Measurement Of 3D Force And Moment On Lower-Limb Osseointegrated Fixation

Implant loosening and mechanical failure are two major concerns for trans-femoral amputees using osseointegrated fixation. Understanding the true load applied on osseointegrated fixation is one important step in solving the two problems. Conventionally, the load magnitude can be calculated based on the motion of the prosthesis and the ground reaction forces measured by a force plate using inverse dynamics. However, this approach allowed only one or two walking steps to be measured and errors are compounded when involving more than one joint. In this study, we directly measured load acting on the abutment of an osseointegrated prosthesis with a load transducer for twelve trans-femoral amputees. Three-dimensional force and moment patterns at the abutment along a gait cycle were displayed. Step-to-step variability of each subject in various kinetic and temporal parameters as well as subject-to-subject variability in temporal parameters were found low. High subject-to-subject variability in force and moment data was demonstrated

Osseointegrated titanium implants for limb prostheses attachments: infectious complications.

BackgroundThe 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/purposesWe 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 methodsWe 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.ResultsThe 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.ConclusionsDespite 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 evidenceLevel IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence

Osteomyelitis Risk in Patients With Transfemoral Amputations Treated With Osseointegration Prostheses.

BackgroundPercutaneous anchoring of femoral amputation prostheses using osseointegrating titanium implants has been in use for more than 25 years. The method offers considerable advantages in daily life compared with conventional socket prostheses, however long-term success might be jeopardized by implant-associated infection, especially osteomyelitis, but the long-term risk of this complication is unknown.Questions/purposes(1) To quantify the risk of osteomyelitis, (2) to characterize the clinical effect of osteomyelitis (including risk of implant extraction and impairments to function), and (3) to determine whether common patient factors (age, sex, body weight, diabetes, and implant component replacements) are associated with osteomyelitis in patients with transfemoral amputations treated with osseointegrated titanium implants.MethodsWe retrospectively analyzed our first 96 patients receiving femoral implants (102 implants; mean implant time, 95 months) treated at our center between 1990 and 2010 for osteomyelitis. Six patients were lost to followup. The reason for amputation was tumor, trauma, or ischemia in 97 limbs and infection in five. All patients were referred from other orthopaedic centers owing to difficulty with use or to be fitted with socket prostheses. If found ineligible for this implant procedure no other treatment was offered at our center. Osteomyelitis was diagnosed by medical chart review of clinical signs, tissue culture results, and plain radiographic findings. Proportion of daily prosthetic use when osteomyelitis was diagnosed was semiquantitatively graded as 1 to 3. Survivorship free from implant- associated osteomyelitis and extraction attributable to osteomyelitis respectively was calculated using the Kaplan-Meier estimator. Indication for extraction was infection not responsive to conservative treatment with or without minor débridement or loosening of implant.ResultsImplant-associated osteomyelitis was diagnosed in 16 patients corresponding to a 10-year cumulative risk of 20% (95% CI 0.12-0.33). Ten implants were extracted owing to osteomyelitis, with a 10-year cumulative risk of 9% (95% CI 0.04-0.20). Prosthetic use was temporarily impaired in four of the six patients with infection who did not undergo implant extraction. With the numbers available, we did not identify any association between age, BMI, or diabetes with osteomyelitis; however, this study was underpowered on this endpoint.ConclusionThe increased risk of infection with time calls for numerous measures. First, patients should be made aware of the long-term risks, and the surgical team should have a heightened suspicion in patients with method-specific presentation of possible infection. Second, several research questions have been raised. Will the surgical procedure, rehabilitation, and general care standardization since the start of the program result in lower infection rates? Will improved diagnostics and early treatment resolve infection and prevent subsequent extraction? Although not supported in this study, it is important to know if most infections arise as continuous bacterial invasion from the skin and implant interface and if so, how this can be prevented?Level of evidenceLevel IV, therapeutic study