Magnitude and variability of loading on the osseointegrated implant of transfemoral amputees during walking.

This study directly measured the load acting on the abutment of the osseointegrated implant system of transfemoral amputees during level walking, and studied the variability of the load within and among amputees. Twelve active transfemoral amputees (age: 54 +/- 12 years, mass: 84.3 +/- 16.3 kg, height: 17.8 +/- 0.10 m) fitted with an osseointegrated implant for over 1 year participated in the study. The load applied on the abutment was measured during unimpeded, level walking in a straight line using a commercial six-channel transducer mounted between the abutment and the prosthetic knee. The pattern and the magnitude of the three-dimensional forces and moments were revealed. Results showed a low step-to-step variability of each subject, but a high subject-to-subject variability in local extrema of body-weight normalized forces and moments and impulse data. The high subject-to-subject variability suggests that the mechanical design of the implant system should be customized for each individual, or that a fit-all design should take into consideration the highest values of load within a broad range of amputees. It also suggests specific loading regime in rehabilitation training are necessary for a given subject. Thus the loading magnitude and variability demonstrated should be useful in designing an osseointegrated implant system better able to resist mechanical failure and in refining the rehabilitation protocol.

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 the rehabilitation protocol.

Static load bearing exercises of individuals with transfemoral amputation fitted with an osseointegrated implant: Loading compliance.

BACKGROUND: Load-bearing exercises are performed by transfemoral amputees fitted with an osseointegrated implant to facilitate bone remodelling. OBJECTIVE: This study presents the loading compliance comparing loads prescribed and applied on the three axes of the implant during static load-bearing exercises with a specific emphasis on axial and vectorial comparisons. STUDY DESIGN: Cohort study. METHODS: A total of 11 fully rehabilitated unilateral transfemoral amputees fitted with an osseointegrated implant performed five trials in four loading conditions using a static standing frame. The load prescribed was monitored using a vertical single-axis strain gauge connected to an electronic display. The tri-axial forces applied on the implant were measured directly with an instrumented pylon including a six-channel transducer. The analysis included 'axial' and 'vectorial' comparisons corresponding to the difference between the force applied on the long axis of the implant and the load prescribed as well as the resultant of the three components of the load applied and the load prescribed, respectively. RESULTS: The results demonstrated that axial and vectorial differences were significant in all conditions ( p < 0.05), except for the vectorial difference for the 40 kg condition ( p = 0.182). CONCLUSION: The significant lack of axial compliance led to systematic underloading of the long axis of the implant. Clinical relevance This study contributes to a better understanding of the load applied on an osseointegrated implant during the static load-bearing exercises that could contribute to improve the design of apparatus to monitor loading exercises as well as clinical guidelines for the loading progression during rehabilitation.

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.

Comparison of prosthetic costs and service between osseointegrated and conventional suspended transfemoral prostheses.

BACKGROUND: Nowadays, a transfemoral amputation prosthesis can be fitted to the skeleton using an osseointegrated implant, that is, without a socket. Treated patients have reported improvements in quality of life. OBJECTIVES: To investigate differences in prosthetic costs and service of osseointegrated prostheses compared to socket-suspended prostheses. STUDY DESIGN: Retrospective cost analysis and survey. METHODS: Costs and noted visits during in mean ~10 years were taken from one prosthetic workshop and included 50 patients with unilateral transfemoral amputation (36 socket-suspended prostheses, 20 osseointegrated prostheses, 6 patients used both kinds of prostheses). A survey comprised 71 patients (69% males; mean age = 52.3 year; cause: 66% trauma, 23% tumour, 11% other). RESULTS: Statistically significant fewer workshop visits were shown with osseointegrated prostheses compared to socket-suspended prostheses (cost analysis: 3.1 vs. 7.2 visits/year, survey: 3.4 vs. 9.2 visits/year). The mean total annual cost of new prostheses, services, repairs and adjustments was 14% lower for osseointegrated prostheses than socket-suspended prostheses (€3149 and €3672 respectively, p = 0.632). A subgroup analysis of recent produced prostheses revealed cost of material to account for 92.5% for osseointegrated prostheses and 70% for socket-suspended prostheses. CONCLUSION: Despite significantly fewer visits for prosthetic service the annual mean costs for osseointegrated prostheses were comparable with socket-suspended prostheses. This study suggests it is due to more advanced prosthetic components being used with osseointegrated prostheses. Clinical relevance Patients with osseointegrated transfemoral prostheses require fewer visits for prosthetic service than patients with socket-suspended prostheses. The total prosthetic cost does not seem to differ between the two kinds of prostheses. However, more sophisticated prosthetic knees were more frequently used with osseointegrated prostheses, which could explain the lack of differences.

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.

Vibrotactile evaluation: osseointegrated versus socket-suspended transfemoral prostheses.

This study investigated detection thresholds of vibrometric stimuli in patients with transfemoral amputation supplied with osseointegrated (OI) and socket-suspended prostheses. It included 17 patients tested preoperatively with socket-suspended prostheses and after 2 yr with OI prostheses and a control group (n = 17) using socket-suspended prostheses, evaluated once. Assessments on the prosthetic and intact feet were conducted at six frequencies (8, 16, 32, 64, 125, and 250 Hz). Furthermore, measurements were conducted to investigate how vibrometric signals are transmitted through a test prosthesis. The results showed that the OI group had improved ability to detect vibrations through the prosthesis at 125 Hz (p = 0.01) at follow-up compared with the preoperative measurement. Compared with the control group, the OI group at follow-up had better ability to detect high frequency vibrations through the prosthesis (125 Hz, p = 0.02; 250 Hz, p = 0.03). The vibrometric signal transmitted through the test prosthesis was reduced at 8, 125, and 250 Hz but was amplified at 16, 32, and 64 Hz. Differences between the OI and the control groups were found in the highest frequencies in which the test prosthesis showed reduction of the vibrometric signal. The study provides insight into the mechanisms of vibration transmission between the exterior and bone-anchored as well as socket-suspended amputation prostheses.

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.

Load-relief of walking AIDS on osseointegrated fixation: instrument for evidence-based practice.

Clinicians are currently in demand of tools enabling individual assessment during their daily practice of load-relief of walking aids. The first aim of this article is to describe a portable kinetic system that could be used to measure directly the true load applied on the residuum during assisted walking. The second aim is to present the information that can be derived from the raw loading data. The third aim is to provide an example for a participant. One active transfemoral amputee fitted with an osseointegrated fixation was asked to walk in straight level line with no aid, one stick, one and two elbow crutches on a 20 m walkway. The load-relief was measured using a six-channel transducer and recorded using a data logger. The overall loading was decreased by 2% using one stick, 5% using one crutch and by 10% using two crutches. This study presents a method that can be used by clinicians facing the challenge of prescribing and assessing walking aids to restore the locomotion of lower limb amputees in the framework of an evidence-based practice.

Monitoring of the load regime applied on the osseointegrated fixation of a trans-femoral amputee: a tool for evidence-based practice.

This study aimed to provide a description of the continuous recording of the true load regime experienced during daily living by the abutment of a trans-femoral amputee fitted with an osseointegrated fixation. The specific objectives: (i) To present an apparatus and a procedure allowing recording of the load regime, and (ii) an example of the raw data and six performance indicators of the usage of the prosthesis obtained with this method. A subject was monitored for a period of 5 hours as he went about his daily activities. The load regime was directly measured and recorded using a commercial transducer and data logger. The overall load profile presented alternative periods of variable length of inactivity (64%) and activity (36%), respectively. The maximum load applied on the mediolateral, anteroposterior and the long axes represented 21%, 21% and 120% of the body weight, respectively. The anteroposterior, mediolateral and long components of the impulse were 395 kN.s, 359 kN.s and 2,323 kN.s, respectively. The amputee generated a total of 2312 gait cycles of the prosthetic leg, giving an approximate overall cadence of 8 stride/min. Preliminary outcomes indicated that the proposed method was an improvement on the current techniques as it provided the true loading and actual usage of the prosthesis during daily living. This study is a stepping stone in the development of future affordable, on-board and user-friendly load recording systems that can be used in evidence-based practice.