Amputee's Residual Limb Research Articles

Heterotopic Ossification Is Associated with Painful Neuromas in Transtibial Amputees Undergoing Surgical Treatment of Symptomatic Neuromas

Background: A relationship between nerve and osseous regeneration has been described. During the surgical treatment of symptomatic neuroma in transtibial amputees, we have noticed that heterotopic ossification (HO) depicted on preoperative radiographs appears to be associated with the location of symptomatic neuromas in both the peroneal and tibial nerve distributions. Methods: Data were collected for transtibial amputees who underwent surgical management of symptomatic neuroma and were prospectively enrolled from 2018 through 2023. Preoperative radiographs were assessed for the presence of HO located at the distal fibula and tibia. The presence of a peroneal and/or tibial neuroma was based on findings contained within the operative reports. Pain levels were measured on a numeric rating scale (0-10). Results: Sixty-five limbs of 62 amputees were include. Peroneal neuroma and presence of fibular HO (P=0.001), and tibial neuroma and presence of tibial HO (P=0.038) demonstrated an association. The odds of having a symptomatic peroneal neuroma with fibular HO present are greater than the odds of a symptomatic peroneal neuroma when fibular HO is absent (OR 9.3; 95%CI [1.9-45.6], P=0.006). Pre-operative pain scores were significantly higher for all patients with HO (P<0.001), those with fibular HO (P<0.001), and those with tibial HO (P<0.001), compared to patients without HO. Conclusions: In patients with symptomatic neuromas, preoperative pain was worse when HO was present in the transtibial amputee's residual limb. Further research on the neuroma-HO-complex in symptomatic amputees is required. Level of Evidence: Therapeutic Level IV

Numerical simulation and experimental testing for static failure prediction in additively manufactured below-knee prosthetic sockets.

The socket of a transtibial prosthesis is a structural part customized to a patient's amputated residual lower limb. The free-form geometry of the socket can be suitable for additive manufacturing (AM) to save time and cost. However, the mechanical fracture of additively manufactured lower limb prostheses is not yet fully understood. A novel experimental method and numerical approach by finite element method (FEM) to test the strength and fracture behavior of a lower limb prosthetic socket of acrylonitrile butadiene styrene (ABS), reverse-engineered using computer-aided design (CAD) from the actual amputee's residual limb and manufactured using fused filament fabrication (FFF) are proposed in the present work. The mechanical behavior, von Mises stress distribution, and the damage status of layered AM sockets of different thicknesses were simulated by FEM using Hashin's transversely isotropic mechanical damage model, initially developed for composite materials. The experimental work showed that the fracture failure initiated at the corner of the lobe in the 4 mm thickness socket at a failure load of 918.5 N. The FEM results predicted this failure load to be 896.6 N, with only a 2.45% error as compared to the experiment. The failure loads predicted by FEM in the sockets with thicknesses of 3, 5, and 6 mm were 618.1, 1008.6, and 1105.2 N, respectively. The present work provides a dependable method for testing a below-knee prosthetic socket against static failure and arriving at a factor-of-safety (FoS) based socket thickness selection for any amputee.

A Tactile Sensing System Based on the Triboelectric Nanogenerator for Prosthetic Application

The distribution of interfacial stress between the amputee's residual limb and the prosthetic socket is thought to be directly related to comfort. Prosthetic sockets are custom-made and the current technology is very mature, whether, by manual molding or 3D scanning, the prosthesis can be made to fit the patient's residual limb, but when the patient actually wears the prosthesis, the wearer may still experience discomfort due to long wear time and foreign body friction. Therefore, researchers have been interested in quantifying these interfacial stresses in order to assess the extent of any potential damage to the residual limb and to reduce the cost of prosthetic fabrication by avoiding repetitive changes to the prosthesis. However, the existing pressure sensors are not only expensive but also have compatibility problems with the residual limb and are prone to instability under the influence of the external environment, which greatly affects the actual force readings in the area. Here, we developed a tactile sensor by triboelectric nanogenerator(TENG), which collects force energy by triboelectric effect, and its wide material selection, easy fabrication, and self-driving properties are receiving more and more attention. In our research, we propose to develop a multi-point array tactile sensor based on two materials: polydimethylsiloxane (PDMS) and polycaprolactone (PCL). The surface of PDMS has a droplet microstructure, and PCL is made into a nanofiber film by electrospinning to increase the specific surface area of the material in contact to improve the output characteristics of the device and achieve a larger detection range and sensitivity. In addition to the excellent durability at 10,000 cycles, the characteristics of the device also show good stability at different humidity and temperature. Finally, we integrated this multi-point array sensor with a multi-channel measurement system, attached it to the contact interface of a 3D-printed residual limb and prosthetic model, and collected real-time correspondence signals from the compressed side to demonstrate the feasibility of this application. We believe that this novel design offers a new approach to improve the comfort of prosthetic wear for amputees and has considerable potential.

A triboelectric nanogenerator-based tactile sensor array system for monitoring pressure distribution inside prosthetic limb

In the prosthetic field, quantifying interfacial pressure distribution between the amputee's residual limb and the socket’s internal environment is imperative for developing new technologies. However, the commercially available pressure sensors have several disadvantages, namely external power supply requirements, low stability, high cost, and complexities related to integrating the sensor system into prosthetic devices. Herein, we propose a self-powered triboelectric nanogenerator (TENG) based flexible tactile sensor array system to monitor prosthetic socket internal pressure distribution in real-time. The proposed sensor consists of biocompatible polydimethylsiloxane (PDMS) polymer and polycaprolactone (PCL) nanofiber membranes as triboelectric materials. The biodegradable PCL nanofiber membrane, fabricated via a scalable and cost-effective electrospinning process, possesses a high surface area-to-volume ratio, facilitating enhanced charge generation during triboelectrification. The as-fabricated TENG-based tactile sensor is highly stable up to 10,000 cycles. Furthermore, the voltage of the tactile sensor is independent of different temperature and humidity values, demonstrating the stability of the sensor under various environmental conditions. Finally, we successfully integrated the tactile sensor array within a prosthetic device to monitor real-time pressure distribution inside the prosthetic socket during gait simulation. We believe that the proposed novel design provides a new dimension for the rapid development of self-powered, low-cost, and highly stable pressure monitoring systems with considerable potential for commercialization.

Automated and Controlled System for Analysis of Residual Limbs Thermograms of Transtibial Amputees

This work describes the development of a controlled cabin for capturing and analyzing thermal images. The motivation of such a device is to aid in the thermal image acquisition process within a confined space. The thermograms generated provide helpful information for analyzing the residual human limb in subjects with transtibial amputation. Such a study proposes a non-intrusive method to study the thermal activity on the amputee residual limb and seek a correlation to the quality of the socket. The proposed cabin ensures the repeatability of the thermograms acquisition process and provides an isolated workspace, thus improving the quality of the samples. The methodology consists of the design of the mechanical elements and parts of the system on computer-aided design software, the electronic instrumentation, a graphic user interface, and the control algorithm based on a barrier Lyapunov function to solve the trajectory tracking for the camera movements, and numerical simulations to illustrate the functionality and the manufacture of a prototype. The results obtained by implementing the control design on the automated cabin reveal that the thermal image acquisition process is completed following the desired trajectory with a mean squared tracking error of 0.0052. In addition, an example of the thermal images of two subjects and the results processing this class of pictures using the designed interface is shown.

A Bioimpedance Analysis Platform for Amputee Residual Limb Assessment.

The objective of this research was to develop a bioimpedance platform for monitoring fluid volume in residual limbs of people with trans-tibial limb loss using prostheses. A customized multifrequency current stimulus profile was sent to thin flat electrodes positioned on the thigh and distal residual limb. The applied current signal and sensed voltage signals from four pairs of electrodes located on the anterior and posterior surfaces were demodulated into resistive and reactive components. An established electrical model (Cole) and segmental limb geometry model were used to convert results to extracellular and intracellular fluid volumes. Bench tests and testing on amputee participants were conducted to optimize the stimulus profile and electrode design and layout. The proximal current injection electrode needed to be at least 25cm from the proximal voltage sensing electrode. A thin layer of hydrogel needed to be present during testing to ensure good electrical coupling. Using a burst duration of 2.0ms, intermission interval of 100μs, and sampling delay of 10μs at each of 24 frequencies except 5kHz, which required a 200-μs sampling delay, the system achieved a sampling rate of 19.7Hz. The designed bioimpedance platform allowed system settings and electrode layouts and positions to be optimized for amputee limb fluid volume measurement. The system will be useful toward identifying and ranking prosthetic design features and participant characteristics that impact residual limb fluid volume.

How do walking, standing, and resting influence transtibial amputee residual limb fluid volume?

The purpose of this research was to determine how fluid volume changes in the residual limbs of people with transtibial amputation were affected by activity during test sessions with equal durations of resting, standing, and walking. Residual limb extracellular fluid volume was measured using biompedance analysis in 24 participants. Results showed that all subjects lost fluid volume during standing with equal weight-bearing, averaging a loss rate of -0.4%/min and a mean loss over the 25 min test session of 2.6% (standard deviation [SD] 1.1). Sixteen subjects gained limb fluid volume during walking (mean gain of 1.0% [SD 2.5]), and fifteen gained fluid volume during rest (mean gain of 1.0% [SD 2.2]). Walking explained only 39.3% of the total session fluid volume change. There was a strong correlation between walk and rest fluid volume changes (-0.81). Subjects with peripheral arterial disease experienced relatively high fluid volume gains during sitting but minimal changes or losses during sit-to-stand and stand-to-sit transitioning. Healthy female subjects experienced high fluid volume changes during transitioning from sit-to-stand and stand-to-sit. The differences in fluid volume response among subjects suggest that volume accommodation technologies should be matched to the activity-dependent fluid transport characteristics of the individual prosthesis user.

Selective recovery of fascicular activity in peripheral nerves

The peripheral nerves of an amputee's residual limb still carry the information required to provide the robust, natural control signals needed to command a dexterous prosthetic limb. However, these signals are mixed in the volume conductor of the body and extracting them is an unmet challenge. A beamforming algorithm was used to leverage the spatial separation of the fascicular sources, recovering mixed pseudo-spontaneous signals with normalized mean squared error of 0.14 ± 0.10 (n = 12) in an animal model. The method was also applied to a human femoral nerve model using computer simulations and recovered all five fascicular-group signals simultaneously with R2 = 0.7 ± 0.2 at a signal-to-noise ratio of 0 dB. This technique accurately separated peripheral neural signals, potentially providing the voluntary, natural and robust command signals needed for advanced prosthetic limbs.

Elevated Vacuum Suspension Influence on Lower Limb Amputee's Residual Limb Volume at Different Vacuum Pressure Settings

In Brief Lower limb amputees continue to contend with residual limb volume fluctuations. The stabilization of residual limb volume has the ability to increase comfort, reduce tissue breakdown, and improve daily function. Clinical evidence on elevated vacuum suspension has demonstrated the potential to maintain residual limb volume; however, the effect of different vacuum pressure settings has not been quantified. The purpose of this research is to gain outcome knowledge regarding elevated vacuum suspension and to investigate the effects of different vacuum pressure settings on lower limb amputee's residual limb volume. This single subject study focused on a K2 transtibial amputee new to elevated vacuum suspension with a history of residual limb volume fluctuations. The patient was fitted with a 0-ply total surface bearing socket that used the LimbLogic® VS. The percent change in volume was measured using the OMEGA® Tracer® volume feature at three treatment levels: absence of elevated vacuum (suction), vacuum (negative pressure) at 10 in Hg, and vacuum (negative pressure) at 15 in Hg. The results indicated a significantly less volume fluctuation with vacuum (0.8%) compared with suction (4.9%). Vacuum settings at 10 and 15 in Hg generated similar absolute percent changes in volume; however, 15 in Hg demonstrated a decreasing rate of change potentially suggesting a physiological alteration in the residual limb. During the duration of the study (3.5 months), an improvement was seen in volume retention with the length of vacuum suspension usage. In addition, the progressive healing of a distal wound was observed. As lower limb amputees continue to contend with residual limb volume fluctuations, it is important to understand the benefits the elevated vacuum can provide. Future research is necessary to investigate any physiological changes to the residual limb because of vacuum pressure settings. Vacuum suspension significantly improved volume retention compared with suction. Volume retention improved with the length of vacuum suspension usage, along with progressive healing of a distal wound. The authors believe future research is needed to investigate any physiological changes to the residual limb because of vacuum pressure settings and to fully understand the mechanisms associated with the ability to retain residual limb volume with elevated vacuum suspension.

Does transverse plane mechanical compliance affect amputee gait and in-socket forces?

Transverse plane rotation in an amputee's residual-limb appears to be less than in non-amputees [1,2]. However, it remains unclear firstly, to what extent this is driven by the properties of the prosthesis, and secondly, whether this has detrimental effects on the residual-limb. In trans-tibial prostheses, the socket and foot are commonly connected via a rigid adapter, which restricts the residual-limb's transverse rotation while inside the socket and can increase the forces exerted onto the residual-limb. This can subsequently trigger tissue damage. Instead of a rigid connection, an adapter with a compliant element can be fitted to prostheses to allow some transverse rotation. This novel study quantified in-socket forces and amputated side kinetics and kinematics to investigate the mechanisms by which the adapter reduces in-socket forces. Gait tests were conducted with ten unilateral trans-tibial amputees who walked on a prosthesis that had an adapter with (A) and without (B) a compliant element. Comparing (A) with (B) showed that, at early stance, whilst the socket rotated internally due to adapter compliance, the pelvis was therefore likely to internally rotate and move forward more relative to the prosthesis. This forward motion is associated with greater elevation of the centre of mass, which can be compensated for by increasing and delaying the peak in knee flexion during stance. Peak knee flexion magnitude was not significantly increased with the adapter (approximately 0.6 °, p = 0.976). However, peak knee flexion was significantly delayed with the adapter (approximately 3.28% of stance, p=0.010). Knee flexion is a common shock absorption mechanism, which significantly reduced the peak vertical ground reaction force (approximately 0.2N/kg, p=0.050) and delayed it, although not significantly (approximately 1.41% of stance, p=0.141), thus overall reducing the vertical loading rate. Reduced in-socket forces supported these findings. In conclusion, adapter compliance has therefore beneficial effects on residual-limb forces.

Topical capsaicin as an adjuvant analgesic for the treatment of traumatic amputee neurogenic residual limb pain

The treatment of amputee residual limb pain can at times be a challenge for the physician. Occasionally, traditional analgesic medication regimens cannot be used or are ineffective in relieving the pain. Topical capsaicin cream has been a beneficial adjuvant medication in the treatment of some painful conditions. The authors present three patients with traumatic upper limb amputations where topical capsaicin cream was of benefit in the treatment of neurogenic residual limb pain. The hope is that these cases will increase awareness of the potential use of capsaicin cream as an adjuvant analgesic in patients with residual limb pain. Common causes of residual limb pain and the pharmacology of capsaicin cream are discussed.

Effects of Design Variants in Lower-Limb Prostheses on Gait Synergy

A lower-limb prosthesis is the mechanical device with which an amputee's residual limb interacts with the walking surface. The pressure and shear forces that affect the residuum due to prosthesis use are the sources of pain, residual-limb skin problems and gait deviations. Direct approaches to reducing these problems include improving fit, alignment technique and socket design as well as increasing cushioning with socket liners. A summary of typical malalignments and their consequences is presented. The malalignments are considered sources of excessive moments applied to the residuum, which simplifies the analysis of a patient's gait. A better design of prosthetic joints could improve prosthetic gait. This article addresses the key mechanical parameter of prosthetic joints, namely the dependence of resistance/angle of deflection. A mathematical model has been developed that links stresses on the residuum in transtibial amputees with the moment of resistance in the prosthetic ankle at the critical gait phases. Analysis of the model yields a substantial decrease in stresses on the residuum during the most demanding, load-bearing phase of stance if the moment of resistance in the ankle is similar to that seen in the biological ankle joint. Gait study shows use of the experimental rolling-joint prosthetic foot more closely simulates normal gait synergy than the SACH foot.

Effects of Design Variants in Lower-Limb Prostheses on Gait Synergy.

A lower-limb prosthesis is the mechanical device with which an amputee's residual limb interacts with the walking surface. The pressure and shear forces that affect the residuum due to prosthesis use are the sources of pain, residual-limb skin problems and gait deviations. Direct approaches to reducing these problems include improving fit, alignment technique and socket design as well as increasing cushioning with socket liners. A summary of typical malalignments and their consequences is presented. The malalignments are considered sources of excessive moments applied to the residuum, which simplifies the analysis of a patient's gait. A better design of prosthetic joints could improve prosthetic gait. This article addresses the key mechanical parameter of prosthetic joints, namely the dependence "moment of resistance/angle of deflection." A mathematical model has been developed that links stresses on the residuum in transtibial amputees with the moment of resistance in the prosthetic ankle at the critical gait phases. Analysis of the model yields a substantial decrease in stresses on the residuum during the most demanding, load-bearing phase of stance if the moment of resistance in the ankle is similar to that seen in the biological ankle joint. Gait study shows use of the experimental rolling-joint prosthetic foot more closely simulates normal gait synergy than the SACH foot.

Measurement of stresses in three orthogonal directions at the residual limb-prosthetic socket interface

Transducers were developed to measure stresses in three orthogonal directions applied on a below-knee amputee residual limb within a prosthetic socket during walking. Strain-gage measurement techniques were used for all three orthogonal directions. Instrumentation error for four transducers averaged less than 4.2% full-scale output (FSO) for the normal direction and less than 0.9% FSO for shear directions. Measurements from amputee subjects collected during walking trials are presented. >

Natural Course of the Amputee's Residual Limb as Followed by Sequential Ultrasound Examinations

The authors studied 13 amputees (7 below knee, 6 above knee) with sequential ultrasound examinations at weeks 1, 2, 3, and 6 status post amputation to define the natural evolution of stump healing in below- and above-knee amputations. This would permit diagnosis of abnormal conditions such as abscess. In their series, they found striking differences between below- and above-knee amputations. In below-knee amputations the development of fluid collections was rare (2/6) and, when present, small (less than 3 cm) and transient (resolving within two to three weeks). In above-knee amputations, all stumps first developed subcutaneous edema followed by fluid collections (less than 5 cm) all of which resolved within six weeks. They found that ultrasound examinations are a useful technique to define abnormal fluid collections in the amputee's residual limb.