Loading characteristics data applied on osseointegrated implant by transfemoral bone-anchored prostheses fitted with basic components during daily activities

Load applied on osseointegrated implant by transfemoral bone-anchored prostheses fitted with state-of-the-art prosthetic components

BACKGROUND

This study presented the load profile applied on transfemoral osseointegrated implants by bone-anchored prostheses fitted with state-of-the-art ÖSSUR microprocessor-controlled Rheo Knee XC and energy-storing-and-returning Pro-Flex XC or LP feet during five standardized daily activities.

METHODS

This cross-sectional cohort study included 13 participants fitted with a press-fit transfemoral osseointegrated implant. Loading data were directly measured with the tri-axial transducer of an iPecsLab (RTC Electronics, USA) fitted between the implant and knee unit. The loading profile was characterized by spatio-temporal gaits variables, magnitude of loading boundaries as well as onset and magnitude of loading extrema during walking, ascending and descending ramp and stairs.

FINDINGS

A total of 2127 steps was analysed. The cadence ranged between 36 ± 7 and 47 ± 6 strides/min. The absolute maximum force and moments applied across all activities was 1322 N, 388 N and 133 N as well as 22 Nm, 52 Nm and 88 Nm on and around the long, anteroposterior and mediolateral axes of the implant, respectively.

INTERPRETATION

This study provided new benchmark loading data applied by transfemoral bone-anchored prostheses fitted with selected ÖSSUR state-of-the-art components. Outcomes suggested that such prostheses can generate relevant loads at the interface with the osseointegrated implant to restore ambulation effectively. This study is a worthwhile contribution toward a systematic recording, analysis, and reporting of ecological prosthetic loading profiles as well as closing the evidence gaps between prescription and biomechanical benefits of state-of-the-art components. Hopefully, this will contribute to improve outcomes for growing number of individuals with limb loss opting for bionic solutions.

A Preliminary Cost-Utility Analysis of the Prosthetic Care Innovations: Case of the Keep Walking Implant

Several obstacles must be overcome before preliminary cost-utility analyses (CUA) of prosthetic care innovations can be routinely performed. The basic framework of preliminary CUAs and hands- on recommendations suggested previously might contribute to wider adoption. However, a practical application for an emerging intervention is needed to showcase the capacity of this proposed preliminary CUA framework. This study presented the outcomes of preliminary CUA of the distal weight bearing Keep Walking Implant (KWI), an emerging prosthetic care innovation that may reduce socket fittings for individuals with transfemoral amputation. The preliminary CUAs compared the provision of prosthetic care without (usual intervention) and with the KWI (new intervention) using a 15-step iterative process focused on feasibility, constructs, analysis, and interpretations of outcomes from an Australia government prosthetic care perspective over a six-year time horizon. Baseline and incremental costs were extracted from schedules of allowable expenses. Baseline utilities were extracted from a study and converted into quality-adjusted life-year (QALY). Incremental utilities were calculated based on sensible gains of QALY from baselines. The provision of the prosthetic care with the KWI could generate an indicative incremental cost-utility ratio (ICUR) of -$36,890 per QALY, which was $76,890 per QALY below willingness-to-pay threshold, provided that the KWI reduces costs by $17,910 while increasing utility by 0.485 QALY compared to usual interventions. This preliminary CUA provided administrators of healthcare organizations in Australia and elsewhere with prerequisite evidence justifying further access to market and clinical introduction of the KWI. Altogether, this work suggests that the basic framework of the preliminary CUA of a prosthetic care innovation proposed previously is feasible and informative when a series of assumptions are carefully considered. This study further confirms that preliminary CUAs prosthetic care interventions might be a relevant alternative to full CUA for other medical treatments.

Loading Effect of Prosthetic Feet's Anthropomorphicity on Transtibial Osseointegrated Implant

INTRODUCTION

Osseointegrated implants for direct skeletal attachment of transtibial prosthesis carry risks that are yet to be fully resolved, such as early loosening, mechanical failure of percutaneous and medullar parts of implant, periprosthetic issues, and infections. Underloading could lead to early loosening and infection. Overloading might compromise the bone-implant interface. Therefore, Goldilocks loading regimen applied by transtibial bone-anchored prostheses is critical for safe and efficient development of osseointegration around the implant during rehabilitation and beyond. We hypothesized that Goldilocks loading could be achieved when ambulating with a so-called anthropomorphic prosthetic ankle showing moment-angle relationship similar to a sound ankle.

MATERIALS AND METHODS

Quantitative characteristics of the moment-angle curve of the sound ankle during dorsiflexion phase of a free-pace walking were extracted for 4 able-bodied participants (experiment 1). A slope of the moment-angle curve (stiffness) was calculated twice: for the first half and for the second half of the moment-angle curve. The difference of stiffnesses (those at the second half minus at the first half) was called the index of anthropomorphicity (IA). By definition, positive IA is associated with concave shape of the moment-angle curve, and the negative IA is associated with convex shape. In experiment 2, the same recordings and calculations were performed for 3 participants fitted with transtibial osseointegrated fixation during walking with their usual feet and the Free-Flow Foot (Ohio Willow Wood). The Free-Flow Foot was selected for its anthropomorphicity demonstrated in the previous studies with amputees using traditional socket attachment.

RESULTS

The IA was 5.88 ± 0.93 for the able-bodied participants, indicating that the stiffness during the first part of the dorsiflexion phase was substantially fewer than during the second parts, as the calf muscles resisted to angulation in ankle substantially less than during the second part of dorsiflexion phase. For amputees fitted with Free-Flow Foot, IA was 2.68 ± 1.09 and -2.97 ± 2.37 for the same amputees fitted with their usual feet.

CONCLUSIONS

Indexes of anthropomorphicity, while of different magnitude, were positive in control able-bodied group and in the amputee group wearing Free-Flow Foot, which was qualitatively associated with concave shape of their moment-angle curves. The 3 usual feet worn by the participants were classified as nonanthropomorphic as their individual moment-angle curves were convex and the corresponding IAs were negative. Furthermore, this study showed that a foot with anthropomorphic characteristics tends to decrease maximal loads at the bone-implant interface as compared to the nonanthropomorphic feet and possibly may minimize the risks to compromise the integrity of this interface.

Kinetics of Lower Limb Prosthesis: Automated Detection of Vertical Loading Rate

Vertical loading rate could be associated with residuum and whole body injuries affecting individuals fitted with transtibial prostheses. The objective of this study was to outline one out of five automated methods of extraction of vertical loading rate that stacked up the best against manual detection, which is considered the gold standard during pseudo-prosthetic gait. The load applied on the long axis of the leg of three males was recorded using a transducer fitted between a prosthetic foot and physiotherapy boot while walking on a treadmill for circa 30 min. The automated method of extraction of vertical loading rate, combining the lowest absolute average and range of 95% CI difference compared to the manual method, was deemed the most accurate and precise. The average slope of the loading rate detected manually over 150 strides was 5.56 ± 1.33 kN/s, while the other slopes ranged from 4.43 ± 0.98 kN/s to 6.52 ± 1.64 kN/s depending on the automated detection method. An original method proposed here, relying on progressive loading gradient-based automated extraction, produced the closest results (6%) to manual selection. This work contributes to continuous efforts made by providers of prosthetic and rehabilitation care to generate evidence informing reflective clinical decision-making.