Residual Limb Research Articles

The gait1415+2 OpenSim musculoskeletal model of transfemoral amputees with a generic bone-anchored prosthesis

This short communication presents the gait1415+2 musculoskeletal model, that has been developed in OpenSim to describe the lower-extremity of a human subject with transfemoral amputation wearing a generic lower-limb bone-anchored prosthesis. The model has fourteen degrees of freedom, governed by fifteen musculotendon units (placed at the contralateral and residual limbs) and two generic actuators (one placed at the knee joint and one at the ankle joint of the prosthetic leg). Even though the model is a simplified abstraction, it is capable of generating a human-like walking gait and, specifically, it is capable of reproducing both the kinematics and the dynamics of a person with transfemoral amputation wearing a bone-anchored prosthesis during normal level-ground walking. The model is released as support material to this short communication with the final goal of providing the scientific community with a tool for performing forward and inverse dynamics simulations, and for developing computationally-demanding control schemes based on artificial intelligence methods for lower-limb prostheses.

The LIBRA NeuroLimb: Hybrid Real-Time Control and Mechatronic Design for Affordable Prosthetics in Developing Regions.

Globally, 2.5% of upper limb amputations are transhumeral, and both mechanical and electronic prosthetics are being developed for individuals with this condition. Mechanics often require compensatory movements that can lead to awkward gestures. Electronic types are mainly controlled by superficial electromyography (sEMG). However, in proximal amputations, the residual limb is utilized less frequently in daily activities. Muscle shortening increases with time and results in weakened sEMG readings. Therefore, sEMG-controlled models exhibit a low success rate in executing gestures. The LIBRA NeuroLimb prosthesis is introduced to address this problem. It features three active and four passive degrees of freedom (DOF), offers up to 8 h of operation, and employs a hybrid control system that combines sEMG and electroencephalography (EEG) signal classification. The sEMG and EEG classification models achieve up to 99% and 76% accuracy, respectively, enabling precise real-time control. The prosthesis can perform a grip within as little as 0.3 s, exerting up to 21.26 N of pinch force. Training and validation sessions were conducted with two volunteers. Assessed with the "AM-ULA" test, scores of 222 and 144 demonstrated the prosthesis's potential to improve the user's ability to perform daily activities. Future work will prioritize enhancing the mechanical strength, increasing active DOF, and refining real-world usability.

Distal weight bearing in transtibial prosthesis users wearing pin suspension.

Low-level distal weight bearing in transtibial prosthesis users may help maintain perfusion and improve both proprioception and residual limb tissue health. The primary objectives of this research were to develop a sensor to continuously measure distal weight bearing, evaluate how prosthesis design variables affected weight bearing levels, and assess fluctuations in distal weight bearing during at-home and community use. In-lab testing on a small group of participants wearing adjustable sockets demonstrated that if distal contact was present, when socket size was increased distal weight bearing increased and when socket size was reduced distal weight bearing decreased. During take-home use, participants accepted the distal weight bearing level set by the research team. It ranged between 1.1% and 6.4% BW for all days tested. The coefficient of variation (standard deviation/mean) ranged from 25% to 43% and was expected due in part to differences in walking style, speed, terrain, direction of ambulation, and bout duration. Two participants commented that they preferred presence of distal weight bearing to non-presence. Next steps in this research are to develop clinical practices to determine target distal weight bearing levels and ranges, and to simplify the design of the sensor and weight bearing adjustment mechanism for clinical use.

The application of biomimetic limbs in postoperative rehabilitation of amputees

Due to the inability to provide recovery opportunities, amputation is generally considered a failure of treatment. Traditional prostheses cannot interact with the surrounding environment, and the contact surface between the prosthesis and the residual limb is prone to wear and tear, causing pain to patients. Therefore, prostheses are generally regarded by patients as tools rather than a part of the body. In recent years, with the continuous development of artificial intelligence, materials science, and biomedical engineering technology, bionic limb technology has received widespread attention and application. Currently, bone integration and electromyography interface technology are widely applied in bionic limbs, allowing for more realistic and diverse options for prostheses for patients. Material innovation and machine learning technology can improve the mechanical performance, perceptual feedback effects, and autonomous learning ability of bionic limbs, but further research and exploration are still needed. This review paper aims to summarize and evaluate the current development status, application areas, and future research directions of bionic limb technology.

Hip joint and muscle loading for persons with bilateral transfemoral/through-knee amputations: biomechanical differences between full-length articulated and foreshortened non-articulated prostheses

BackgroundCurrently, there is little available in-depth analysis of the biomechanical effect of different prostheses on the musculoskeletal system function and residual limb internal loading for persons with bilateral transfemoral/through-knee amputations (BTF). Commercially available prostheses for BTF include full-length articulated prostheses (microprocessor-controlled prosthetic knees with dynamic response prosthetic feet) and foreshortened non-articulated stubby prostheses. This study aims to assess and compare the BTF musculoskeletal function and loading during gait with these two types of prostheses.MethodsGait data were collected from four male traumatic military BTF and four able-bodied (AB) matched controls using a 10-camera motion capture system with two force plates. BTF completed level-ground walking trials with full-length articulated and foreshortened non-articulated stubby prostheses. Inverse kinematics, inverse dynamics and musculoskeletal modelling simulations were conducted.ResultsFull-length articulated prostheses introduced larger stride length (by 0.5 m) and walking speed (by 0.3 m/s) than stubbies. BTF with articulated prostheses showed larger peak hip extension angles (by 10.1°), flexion moment (by 1.0 Nm/kg) and second peak hip contact force (by 3.8 bodyweight) than stubbies. There was no difference in the hip joint loading profile between BTF with stubbies and AB for one gait cycle. Full-length articulated prostheses introduced higher hip flexor muscle force impulse than stubbies.ConclusionsCompared to stubbies, BTF with full-length articulated prostheses can achieve similar activity levels to persons without limb loss, but this may introduce detrimental muscle and hip joint loading, which may lead to reduced muscular endurance and joint degeneration. This study provides beneficial guidance in making informed decisions for prosthesis choice.

Antibacterial evaluation of different prosthetic liner textiles coated by CuO nanoparticles

Prosthetic liners are mainly used as an interface between residual limbs and prosthetic sockets to minimize physical and biological damage to soft tissue. However, the closed and moist conditions within liners and the amputee's skin provide a suitable environment for bacterial growth to cause infections. This study aimed to coat a comprehensive variant material with copper oxide nanoparticles (CuO NPs) and compare their surface analysis and antibacterial properties. These materials were covered with CuO NPs solution at a concentration of 70 μg mL−1 to achieve this purpose. After drying, their surface characteristics were analyzed by measuring zeta potential, contact angle, surface roughness, and fiber arrangement. Cu-released concentration from the coatings into the acetate buffer solution by inductively coupled plasma mass spectrometry indicated that lycra and nylon quickly released Cu ions to concentrations up to ∼0.2 μg mL−1 after 24 h, causing low metabolic activity of human bone–marrow mesenchymal stem cells (bMSC) in the indirect assay. Antibacterial activity of the coated specimens was evaluated by infecting their surfaces with the Gram-positive bacteria Staphylococcus epidermidis, reporting a significant ∼40 % reduction of metabolic activity for x-dry after 24 h; in addition, the number of viable bacterial colonies adhered to the surface of this material was reduced by ∼23 times in comparison with non-treated x-dry that were visually confirmed by scanning electron microscope. In conclusion, CuO NPs x-dry shows optimistic results to pursue further experiments due to its slow speed of Cu release and prolonged antibacterial activity, as well as its compatibility with human cells.

Combining Surgical Innovations in Amputation Surgery-Robotic Harvest of the Rectus Abdominis Muscle, Transplantation and Targeted Muscle Reinnervation Improves Myocontrol Capability and Pain in a Transradial Amputee.

Adding robotic surgery to bionic reconstruction might open a new dimension. The objective was to evaluate if a robotically harvested rectus abdominis (RA) transplant is a feasible procedure to improve soft-tissue coverage at the residual limb (RL) and serve as a recipient for up to three nerves due to its unique architecture and to allow the generation of additional signals for advanced myoelectric prosthesis control. A transradial amputee with insufficient soft-tissue coverage and painful neuromas underwent the interventions and was observed for 18 months. RA muscle was harvested using robotic-assisted surgery and transplanted to the RL, followed by end-to-end neurroraphy to the recipient nerves of the three muscle segments to reanimate radial, median, and ulnar nerve function. The transplanted muscle healed with partial necrosis of the skin mesh graft. Twelve months later, reliable, and spatially well-defined Hoffmann-Tinel signs were detectable at three segments of the RA muscle flap. No donor-site morbidities were present, and EMG activity could be detected in all three muscle segments. The linear discriminant analysis (LDA) classifier could reliably distinguish three classes within 1% error tolerance using only the three electrodes on the muscle transplant and up to five classes outside the muscle transplant. The combination of these surgical procedure advances with emerging (myo-)control technologies can easily be extended to different amputation levels to reduce RL complications and augment control sites with a limited surface area, thus facilitating the usability of advanced myoelectric prostheses.

Development of a hand prosthesis with a heating system to prevent residual limb pain for upper limb amputee

Development of a hand prosthesis with a heating system to prevent residual limb pain for upper limb amputee

Soft robotics-inspired sensing system for detecting downward movement and pistoning in prosthetic sockets: A proof-of-concept study.

Vertical displacement of the residual limb within transtibial prosthetic socket, often known as "pistoning" or downward movement, may lead to skin breakdowns and ulcers. Downward movement is particularly difficult to self-manage for diabetic individuals living with amputation because of diminished sensation in the residual limb from peripheral neuropathy. Therefore, a customizable sensor at the distal end that can alert the users when high-risk downward movement and pistoning occurs is urgently needed. Presented herein for the first time is a lightweight, inexpensive sensing system inspired by soft robotics that can detect the occurrence and severity of downward movement at the distal end. The sensing system consists of a multilayered torus-shaped balloon, allowing easy integration with pin-lock socket systems. The design allows sensing of vertical displacement without imparting high reaction forces back onto the distal end. A benchtop compression tester was used to characterize system performance. Systematic and parametric benchtop tests were conducted to examine the sensor's physical characteristics. Long-term (24-h) stability of the sensor was also recorded. Compared with water, air was determined to be a better medium with a higher linear full-scale span (FSS) because of its compressible nature. Repeatable 0.5-mm vertical displacements yielded a linear (>0.99 R2) FSS of 4.5 mm and a sensitivity of 0.8 kPa/mm. The sensing system is highly precise, with as low as 1% FSS total error band and average hysteresis of 2.84% of FSS. Over 24 h, a 4% FSS drift was observed. Sensing system characteristics, coupled with low-cost, customizable fabrication, indicates promising performance for daily use to notify and alert transtibial prosthetic users of downward movement and/or pistoning.

Ten-year phantom limb pain with only four sessions of Fu's subcutaneous needling: A case report and systematic review

Phantom limb pain (PLP) is a distressing consequence commonly encountered by individuals who have undergone amputations. The efficacy of treatment options for PLP is limited. In this study, we present a case of a 64-year-old male who suffered from PLP for a duration of 10 years following an above-the-knee amputation. Despite unsuccessful attempts with painkillers and neurotrophic drugs over the course of a decade, the patient sought relief through Fu's Subcutaneous Needling (FSN), an innovative acupuncture therapy that specifically targets the subcutaneous tissue for pain management. Remarkably, the patient experienced a significant reduction in PLP and subsequently decreased his reliance on medication, as well as experiencing improved sleep after undergoing one session of FSN per day for four consecutive days. A follow-up conducted three years later demonstrated positive treatment outcomes. FSN demonstrated a significant influence on PLP, resulting in reduced analgesic requirements and enhanced quality of life. Therefore, FSN may be recommended as an additional treatment option for PLP. In order to gain a comprehensive understanding of the effects of acupuncture on PLP, a systematic review of relevant literature was conducted in PubMed, Embase, Cochrane Library and Web of Science in recent 20 years (from January 1, 2003 to October 16, 2023), using different combinations of the following terms: (phantom acrodynia), (residual limb pain), (phantom limb pain), (acupuncture), (electroacupuncture), (auriculoacupuncture), and (needling). 9 articles with 18 cases including one randomized controlled trial (n = 8) were obtained. This review provided additional evidence supporting the efficacy and safety of needling therapies for PLP. This systematic review offers additional evidence supporting the effectiveness and safety of needling therapies for PLP. However, there were no precedent reports using FSN treatment for PLP. Hence, this case may provide some implications for clinicians in practice.

Pain, Balance-Confidence, Functional Mobility, and Reach Are Associated With Risk of Recurrent Falls Among Adults With Lower-Limb Amputation

ObjectiveThe study evaluated whether pain intensity and extent, balance-confidence, functional mobility, and balance (eg, functional reach) are potential risk factors for recurrent falls among adults with a lower-limb amputation. DesignCross-sectional study. SettingResearch laboratory. ParticipantsEighty-three adults with unilateral lower-limb amputation that occurred >1 year prior (26 transfemoral- and 57 transtibial-level amputation; 44.6% women; 51.8% traumatic cause of amputation; N=83). InterventionNot applicable. Main Outcome MeasuresParticipants reported on the number of falls in the past year, as well as pain intensity in the low back, residual, and sound limbs. Balance-confidence (per the Activities-Specific Balance-Confidence Scale [ABC]), functional mobility (per the Prosthetic Limb Users Survey of Mobility ([PLUS-M]), and balance (per the Functional Reach and modified Four Square Step Tests) were obtained. ResultsAfter considering non-modifiable covariates, greater extent of pain, less balance-confidence, worse self-reported mobility, and reduced prosthetic-side reach were factors associated with recurrent fall risk. Adults reporting pain in the low back and both lower-limbs had 6.5 times the odds of reporting recurrent falls as compared with peers without pain. A 1-point increase in ABC score or PLUS-M T score, or 1-cm increase in prosthetic-side reaching distance, was associated with a 7.3%, 9.4%, and 7.1% decrease in odds of reporting recurrent falls in the past year, respectively. ConclusionsOf the 83 adults, 36% reported recurrent falls in the past year. Presence of pain in the low back and both lower-limbs, less balance-confidence, worse PLUS-M score, and less prosthetic-side reaching distance were identified as modifiable factors associated with an increased odd of recurrent falls.

Realizing Upper Extremity Bionic Limbs: Leveraging Neuroprosthetic Control Strategies.

Innovations in prosthetic devices and neuroprosthetic control strategies have opened new frontiers for the treatment and rehabilitation of individuals undergoing amputation. Commercial prosthetic devices are now available with sophisticated electrical and mechanical components that can closely replicate the functions of the human musculoskeletal system. However, to truly recognize the potential of such prosthetic devices and develop the next generation of bionic limbs, a highly reliable prosthetic device control strategy is required. In the past few years, refined surgical techniques have enabled neuroprosthetic control strategies to record efferent motor and stimulate afferent sensory action potentials from a residual limb with extraordinary specificity, signal quality, and long-term stability. As a result, such control strategies are now capable of facilitating intuitive, real-time, and naturalistic prosthetic experiences for patients with amputations. This article summarizes the current state of upper extremity neuroprosthetic devices and discusses the leading control strategies that are critical to the ongoing advancement of prosthetic development and implementation.

Targeted Muscle Reinnervation and Regenerative Peripheral Nerve Interfaces for Prophylactic Pain Control in Neurofibromatosis Type 1 Amputees.

Neurofibromatosis type 1 (NF1) is an inherited multisystem disorder that affects one in 2500 to one in 5000 people. Neurofibromas are the second-most common benign peripheral nerve sheath tumors arising from Schwann cells and are associated with neurofibromatosis. Chronic pain and opioid use is elevated in patients with NF1 when neurofibromas are associated with sensory nerves. Surgical excision is the primary treatment of neurofibromas when they become large, malignant, or painful, but they are associated with high rates of recurrence. Targeted muscle reinnervation and regenerative peripheral nerve interfaces are two prophylactic surgical techniques that are used to prevent neuroma-associated residual limb and phantom pain in amputees. Both techniques stimulate physiologic regeneration of the nerve via trophic stimulus from denervated muscle. This case report describes two patients with NF1 who underwent targeted muscle reinnervation and/or regenerative peripheral nerve interfaces at the time of amputation. Despite the abnormality of the peripheral nerves involved, both patients had excellent postoperative outcomes with minimal pain. This experience advocates for the use of prophylactic nerve management techniques in neurofibromatosis patients despite baseline nerve pathology.

INFLUENCE OF FEMUR LENGTH ON ASYMMETRY OF PROSTHETIC GAIT BIOMECHANICS IN TRANSFEMORAL AMPUTATION

This study compares the prosthetic gait asymmetry in transfemoral amputees with varied femoral lengths to able-bodied participants in terms of temporal-spatial parameters and joint kinematics. Sixteen young and active transfemoral amputees with short and long residual limbs were divided into two groups and subjected to three-dimensional quantitative motion analysis through high definition optoelectronic cameras and force platform. The prosthetic gait of amputees was compared with those of 15 participants with normal gait to analyze the asymmetry. There was a significant difference in temporal-spatial gait parameters between the amputee groups in terms of intact limb stride length and swing time ([Formula: see text]). The gait of amputees with long femoral lengths was with comparatively higher mean step length (0.31 versus 0.35[Formula: see text]m), velocity (0.48 versus 0.44[Formula: see text]m/s), and cadence (73.58 versus 66.62 steps/min) compared to short residual limbs, however these results are nonsignificant ([Formula: see text]). Amputees and able-bodied participants differed significantly for all measured parameters ([Formula: see text]). The amputees with short residual limbs had more variation in sagittal plane hip flexion at initial contact than long amputees and able-bodied subjects. Amputees with longer residual limbs demonstrated peak swing prosthetic hip flexion closer to able-bodied individuals. The frontal pelvic obliquity and sagittal pelvic tilt revealed more variance among amputees with shorter residual limbs than longer ones. This study will aid in identifying the underlying mechanism of gait asymmetry in transfemoral amputees in relation to residual femoral length and hence will pave a path for improving the knee and foot prosthetic components.

Mechanism of Action of Temporary Peripheral Nerve Stimulation.

Peripheral nerve stimulation (PNS) refers to the technique of utilizing electrical stimulation of peripheral nerves to inhibit the transmission of pain signals. PNS is used to treat chronic intractable pain and post-surgical or post-traumatic pain alongside a variety of other pain conditions, including headaches, facial pain, pelvic and urogenital pain, chest wall pain, residual limb or phantom limb pain, and back pain. More recently, PNS has been used temporarily for periods of time less than 60days to treat acute post-surgical pain. Peripheral nerve stimulation is believed to be effective due to its effects on both central and peripheral pathways. Centrally, it is proposed that the electrical pulses of PNS inhibit alpha-delta and C fibers, which decreases pain signaling in the higher centers of the central nervous system. Peripherally, gate theory is applied as it is theorized that PNS downregulates inflammatory mediators, endorphins, and neurotransmitters associated with pain signaling to decrease the transmission of efferent nociception and reduce pain sensations.

Subtrochanteric Shortening Osteotomy Provides Superior Function to Trochanter Slide Osteotomy in THA for Patients With Unilateral Crowe Type IV Dysplasia at a Minimum of 3 Years.

Performing THA in patients with high-riding developmental dysplasia of the hip (DDH) is associated with serious complications and technical challenges. Various methods of shortening osteotomy are available to facilitate femoral head reduction during THA in patients with high-riding hips; subtrochanteric shortening osteotomy and trochanteric slide osteotomy plus proximal shortening are the most common techniques. However, which approach is superior remains a topic of controversy. (1) Is there any difference in clinical outcomes (defined as the Harris Hip Score [HHS] and residual limb length discrepancy) at a minimum of 3 years between subtrochanteric shortening osteotomy and trochanteric slide osteotomy in patients with Crowe Type IV DDH who underwent THA? (2) Is there any difference in the risk or type of complications between the two approaches? We performed a retrospective, comparative study of two groups (subtrochanteric shortening osteotomy versus trochanteric slide osteotomy) matched for sex and preoperative HHS at a minimum of 3 years of follow-up. Between 2010 and 2018, we performed 67 THAs in patients with unilateral Crowe Type IV DDH. During that time, we generally used a trochanteric slide osteotomy for THA in all patients with Crowe Type IV hips and performed subtrochanteric shortening osteotomy when a conical stem was not available. A total of 42% (28) had THA with subtrochanteric shortening osteotomy, and 58% (39) had THA with trochanteric slide osteotomy. Of those, 89% (25) and 74% (29), respectively, were accounted for with complete datasets for possible matching at a minimum of 3 years of follow-up. Patients were matched for gender and preoperative HSS (within 10 points), leaving 22 patients in each group (79% of the subtrochanteric shortening osteotomy group and 56% of the trochanteric slide osteotomy group) for evaluation and analysis. Age (42 versus 46 years), gender (female: 73% versus 73%), preoperative HSS (40 versus 40), and preoperative leg length discrepancy (5.9 versus 5.3 cm) were comparable between the two groups (p > 0.05). The trochanteric slide osteotomy group exclusively received Cone Wagner (Zimmer) implants (100%), while Corail (DePuy Synthes) implants (77%) were the most commonly used in the subtrochanteric shortening osteotomy group. HHS at a minimum of 3 years as well as the presence or absence of a limp and Trendelenburg sign, functional leg length discrepancy, nonunion, nerve palsy, and other surgical complications were recorded and compared between the groups based on data drawn from a longitudinally maintained institutional database. At a mean follow-up of 73 months, improvement in HHS was greater in the subtrochanteric shortening osteotomy group than in the trochanteric slide osteotomy group (48 ± 4 points versus 36 ± 11 points, mean difference 12 points [95% CI 7 to 17 points]; p < 0.001). Although the preoperative leg length discrepancy was similar between the groups, there was a greater postoperative improvement in the subtrochanteric shortening osteotomy group (44 ± 8 mm and 38 ± 8 mm in the subtrochanteric shortening osteotomy and trochanteric slide osteotomy groups, respectively; p = 0.02). The risk of nonunion was higher with a trochanteric slide osteotomy than with a subtrochanteric shortening osteotomy (23% [5 of 22] versus 0% [0 of 22]; p = 0.048). Other complications, including intraoperative periprosthetic fractures, nerve palsy, heterotopic ossification, revision surgery, and dislocation, did not differ between the groups. In patients with Crowe Type IV hips undergoing THA, surgeons might consider subtrochanteric shortening osteotomy rather than trochanteric slide osteotomy to minimize the risk of nonunion and achieve superior hip function. Better correction of leg length discrepancy may also be possible with subtrochanteric shortening osteotomy. The long-term survivorship of hips after these two techniques, as well as the influence of the specific anatomy of the proximal femur on the choice of technique, remain to be explored in future studies. Level III, therapeutic study.

Imperceptive and reusable dermal surface EMG for lower extremity neuro-prosthetic control and clinical assessment

Surface electromyography (sEMG) sensors play a critical role in diagnosing muscle conditions and enabling prosthetic device control, especially for lower extremity robotic legs. However, challenges arise when utilizing such sensors on residual limbs within a silicon liner worn by amputees, where dynamic pressure, narrow space, and perspiration can negatively affect sensor performance. Existing commercial sEMG sensors and newly developed sensors are unsuitable due to size and thickness, or susceptible to damage in this environment. In this paper, our sEMG sensors are tailored for amputees wearing sockets, prioritizing breathability, durability, and reliable recording performance. By employing porous PDMS and Silbione substrates, our design achieves exceptional permeability and adhesive properties. The serpentine electrode pattern and design are optimized to improve stretchability, durability, and effective contact area, resulting in a higher signal-to-noise ratio (SNR) than conventional electrodes. Notably, our proposed sensors wirelessly enable to control of a robotic leg for amputees, demonstrating its practical feasibility and expecting to drive forward neuro-prosthetic control in the clinical research field near future.

Intuitive movement-based prosthesis control enables arm amputees to reach naturally in virtual reality.

Impressive progress is being made in bionic limbs design and control. Yet, controlling the numerous joints of a prosthetic arm necessary to place the hand at a correct position and orientation to grasp objects remains challenging. Here, we designed an intuitive, movement-based prosthesis control that leverages natural arm coordination to predict distal joints missing in people with transhumeral limb loss based on proximal residual limb motion and knowledge of the movement goal. This control was validated on 29 participants, including seven with above-elbow limb loss, who picked and placed bottles in a wide range of locations in virtual reality, with median success rates over 99% and movement times identical to those of natural movements. This control also enabled 15 participants, including three with limb differences, to reach and grasp real objects with a robotic arm operated according to the same principle. Remarkably, this was achieved without any prior training, indicating that this control is intuitive and instantaneously usable. It could be used for phantom limb pain management in virtual reality, or to augment the reaching capabilities of invasive neural interfaces usually more focused on hand and grasp control.

Intuitive movement-based prosthesis control enables arm amputees to reach naturally in virtual reality

Impressive progress is being made in bionic limbs design and control. Yet, controlling the numerous joints of a prosthetic arm necessary to place the hand at a correct position and orientation to grasp objects remains challenging. Here, we designed an intuitive, movement-based prosthesis control that leverages natural arm coordination to predict distal joints missing in people with transhumeral limb loss based on proximal residual limb motion and knowledge of the movement goal. This control was validated on 29 participants, including seven with above-elbow limb loss, who picked and placed bottles in a wide range of locations in virtual reality, with median success rates over 99% and movement times identical to those of natural movements. This control also enabled 15 participants, including three with limb differences, to reach and grasp real objects with a robotic arm operated according to the same principle. Remarkably, this was achieved without any prior training, indicating that this control is intuitive and instantaneously usable. It could be used for phantom limb pain management in virtual reality, or to augment the reaching capabilities of invasive neural interfaces usually more focused on hand and grasp control.

Motion Analysis of a Frontal Plane Adaptable Prosthetic Foot.

ABSTRACT Introduction An objective of designing a prosthetic foot is to achieve the natural adaptability of the foot and ankle on various surfaces and different forms of gait. Frontal plane position of the foot relative to the shank changes with many functional aspects of gait, such as turning, stairs, and walking on uneven ground. Prosthetic foot designs have variable frontal plane adaptability. An investigation foot with a linkage with ±10° of frontal plane motion was developed to improve frontal plane response under various conditions. The purpose of this study was to compare the kinematics of locked and unlocked conditions of a frontal plane adaptable prosthetic foot and the person’s usual foot while walking forward on a level surface, on an unstable rock surface, and sidestep, using a crossover design. These different conditions result in changes in frontal plane motion in the anatomical foot and ankle, and the current study evaluates whether there are similar trends in prosthetic feet. Materials and Methods People were included if they had a unilateral below-knee amputation, intact residual limb skin, were over 16 years old, and were able to walk more than 400 m on level ground without using a walking aid and without an increase in pain. The control group was people without amputations who completed the procedures once. Participants with amputations completed forward walking on level ground, on an unstable rock surface, and sidestep with their usual foot. Then after 2 weeks of accommodation, participants repeated these tests with the investigational foot unlocked and locked. Motion analysis data were collected with a 12-camera optically based system. Primary outcomes were sagittal and frontal plane motions of the foot relative to the shank. In addition, step length, step width, and stride velocity were obtained from the kinematic measures. Paired t-tests were used for statistical inference for individual participant comparisons. Unpaired t-tests were used for comparisons between the controls and people with amputations. Results Twenty-one people with amputations and 10 controls completed the tests. Participants with amputation had 16 different usual feet. There was a wide variation in usual foot motion during forward walking, whereas investigational foot conditions showed less variability. During level walking, control subjects had more frontal plane motion than any of the foot conditions, and the unlocked had more frontal plane motion than the usual foot and locked condition. Walking across an unstable rock surface showed similar trends, with control participants having more sagittal and frontal plane ankle motion compared with any prosthetic foot condition. Also, the unlocked had statistically greater frontal plane motion than the usual foot or locked condition. Sidestep results were also consistent with other gait tests. The control participants’ sagittal plane ankle range of motion was significantly more than the prosthetic sagittal plane motion for all foot conditions, whether the prosthetic side was leading or trailing. There was significantly more frontal plane motion with the unlocked than the usual foot and locked condition when the prosthetic foot was trailing or leading. Discussion and Conclusions Wide variation in usual foot range of motions in the frontal and sagittal planes confirmed the need for additional controls when considering the effect of the linkage alone. The unlocked had increased frontal plane ranges of motion compared with the locked and the majority of usual foot for all gait conditions, including level walking. This finding demonstrated that people with amputations were functionally using the additional range of motion provided by the linkage. However, control subjects used more range of motion in both the sagittal and frontal planes for the unstable rock surface and sidestepping. Increased frontal plane range of motion did not translate into improved stride length and velocity, step width, or center of mass deviations. Clinical Relevance The person-specific functional activities should be considered when choosing a prosthetic foot. A prosthesis with frontal plane motion may be applicable for a person who moves in a sidestep pattern or on uneven ground.