Residual limb volume fluctuations in transfemoral amputees.

This study constitutes the first attempt to systematically quantify residual limb volume fluctuations in transfemoral amputees. The study was carried out on 24 amputees to investigate variations due to prosthesis doffing, physical activity, and testing time. A proper experimental set-up was designed, including a 3D optical scanner to improve precision and acceptability by amputees. The first test session aimed at measuring residual limb volume at 7 time-points, with 10 min intervals, after prosthesis doffing. This allowed for evaluating the time required for volume stabilization after prosthesis removal, for each amputee. In subsequent sessions, 16 residual limb scans in a day for each amputee were captured to evaluate volume fluctuations due to prosthesis removal and physical activity, in two times per day (morning and afternoon). These measurements were repeated in three different days, a week apart from each other, for a total of 48 scans for each amputee. Volume fluctuations over time after prosthesis doffing showed a two-term decay exponential trend (R2 = 0.97), with the highest variation in the initial 10 min and an average stabilization time of 30 min. A statistically significant increase in residual limb volume following both prosthesis removal and physical activity was verified. No differences were observed between measures collected in the morning and in the afternoon.Clinical Trials.gov ID: NCT04709367.

A Framework for Measuring the Time-Varying Shape and Full-Field Deformation of Residual Limbs Using 3-D Digital Image Correlation.

Effective prosthetic socket design following lower limb amputation depends upon the accurate characterization of the shape of the residual limb as well as its volume and shape fluctuations. OBJECTIVE: This study proposes a novel framework for the measurement and analysis of residual limb shape and deformation, using a high-resolution and low-cost system. METHODS: A multi-camera system was designed to capture sets of simultaneous images of the entire residuum surface. The images were analyzed using a specially developed open-source three-dimensional digital image correlation (3D-DIC) toolbox, to obtain the accurate time-varying shapes as well as the full-field deformation and strain maps on the residuum skin surface. Measurements on a transtibial amputee residuum were obtained during knee flexions, muscle contractions, and swelling upon socket removal. RESULTS: It was demonstrated that 3D-DIC can be employed to quantify with high resolution time-varying residuum shapes, deformations, and strains. Additionally, the enclosed volumes and cross-sectional areas were computed and analyzed. CONCLUSION: This novel low-cost framework provides a promising solution for the in vivo evaluation of residuum shapes and strains, as well as has the potential for characterizing the mechanical properties of the underlying soft tissues. SIGNIFICANCE: These data may be used to inform data-driven computational algorithms for the design of prosthetic sockets, as well as of other wearable technologies mechanically interfacing with the skin.

Measurement properties and usability of non-contact scanners for measuring transtibial residual limb volume.

BACKGROUND: Non-contact scanners may have potential for measurement of residual limb volume. Different non-contact scanners have been introduced during the last decades. Reliability and usability (practicality and user friendliness) should be assessed before introducing these systems in clinical practice. OBJECTIVES: The aim of this study was to analyze the measurement properties and usability of four non-contact scanners (TT Design, Omega Scanner, BioSculptor Bioscanner, and Rodin4D Scanner). STUDY DESIGN: Quasi experimental. METHODS: Nine (geometric and residual limb) models were measured on two occasions, each consisting of two sessions, thus in total 4 sessions. In each session, four observers used the four systems for volume measurement. Mean for each model, repeatability coefficients for each system, variance components, and their two-way interactions of measurement conditions were calculated. User satisfaction was evaluated with the Post-Study System Usability Questionnaire. RESULTS: Systematic differences between the systems were found in volume measurements. Most of the variances were explained by the model (97%), while error variance was 3%. Measurement system and the interaction between system and model explained 44% of the error variance. Repeatability coefficient of the systems ranged from 0.101 (Omega Scanner) to 0.131 L (Rodin4D). Differences in Post-Study System Usability Questionnaire scores between the systems were small and not significant. CONCLUSION: The systems were reliable in determining residual limb volume. Measurement systems and the interaction between system and residual limb model explained most of the error variances. The differences in repeatability coefficient and usability between the four CAD/CAM systems were small. Clinical relevance If accurate measurements of residual limb volume are required (in case of research), modern non-contact scanners should be taken in consideration nowadays.

A Framework of Temporal-Spatial Descriptors-Based Feature Extraction for Improved Myoelectric Pattern Recognition.

The extraction of the accurate and efficient descriptors of muscular activity plays an important role in tackling the challenging problem of myoelectric control of powered prostheses. In this paper, we present a new feature extraction framework that aims to give an enhanced representation of muscular activities through increasing the amount of information that can be extracted from individual and combined electromyogram (EMG) channels. We propose to use time-domain descriptors (TDDs) in estimating the EMG signal power spectrum characteristics; a step that preserves the computational power required for the construction of spectral features. Subsequently, TDD is used in a process that involves: 1) representing the temporal evolution of the EMG signals by progressively tracking the correlation between the TDD extracted from each analysis time window and a nonlinearly mapped version of it across the same EMG channel and 2) representing the spatial coherence between the different EMG channels, which is achieved by calculating the correlation between the TDD extracted from the differences of all possible combinations of pairs of channels and their nonlinearly mapped versions. The proposed temporal-spatial descriptors (TSDs) are validated on multiple sparse and high-density (HD) EMG data sets collected from a number of intact-limbed and amputees performing a large number of hand and finger movements. Classification results showed significant reductions in the achieved error rates in comparison to other methods, with the improvement of at least 8% on average across all subjects. Additionally, the proposed TSDs achieved significantly well in problems with HD-EMG with average classification errors of <5% across all subjects using windows lengths of 50 ms only.

Rescate articular con colgajo anterolateral del muslo / Joint rescue with anterolateral thigh flap

La preservación del nivel de amputación tanto de la extremidad superior como de la inferior, puede mejorar la función residual y el proceso de rehabilitación protésica de la misma. Ambas van a estar condicionadas por la longitud restante de la extremidad, la presencia o no de articulaciones operativas y la calidad de la cobertura del muñón. Presentamos 2 casos de amputaciones. El primero es un caso agudo de amputación traumática de extremidad superior a la altura del tercio proximal de antebrazo, que asocia avulsión cutánea circular desde el tercio medio del brazo y con articulación de codo conservada. El segundo, es la secuela de una amputación infracondílea de extremidad inferior por osteosarcoma que presenta fístulas cutáneas con drenaje supurativo por osteomielitis en el muñón tibial. En ambos pacientes realizamos cobertura con colgajo anterolateral de muslo anastomosado a la arteria radial en el caso de la extremidad superior, y a la arteria genicular descendente en la extremidad inferior. En los dos casos el postoperatorio transcurrió sin complicaciones, logrando preservar las articulaciones del codo y de la rodilla respectivamente, así como la posterior rehabilitación protésica. Consideramos que el colgajo anterolateral del muslo permite aportar tejido de buena calidad como cobertura del muñón de amputación. Dadas las características del tejido aportado y su volumen, es idóneo tanto para cobertura de defectos agudos como de déficits de almohadillado en casos crónicos (AU)

Sometimes, the severity of the trauma or the existence of a cancer force to amputate a limb. The prosthetic rehabilitation process and residual function will be influenced by the remaining length of the limb, the presence or absence of functional joints and the quality of the coverage of the stump. Two cases of amputations are shown. The former is an acute traumatic upper limb amputation at the level of the proximal third of forearm with skin avulsion from the middle third of the arm and the elbow joint preserved. The second case is the sequelae of an amputation below the knee due to lower extremity osteosarcoma, which was referred with suppurative draining cutaneous fistulas as a consequence of an osteomyelitis of the femur in the stump. In both patients the stumps were covered with anterolateral thigh flap anastomosed over the radial artery in the case of the upper extremity, and over the descending genicular artery in the lower extremity. In both cases the postoperative course was uneventful, preserving the elbow and knee respectively and allowing the subsequent prosthetic rehabilitation. We consider that anterolateral thigh flap is a suitable option for the treatment of the amputation stump. Given the characteristics of the tissue and volume provided by this flap, it is appropriate for coverage of acute defects and for padding deficits in chronic cases (AU)

Reduction of residual limb volume in people with transtibial amputation.

The early postoperative phase after transtibial amputation is characterized by rapid residual limb volume reduction. Accurate measurement of residual limb volume is important for the timing of fitting a prosthesis. The aim of this study is to analyze the reduction of residual limb volume in people with transtibial amputation and to correlate residual limb volume with residual limb circumference. In a longitudinal cohort study of 21 people who had a transtibial amputation, residual limb volume was measured using a laser scanner and circumference was measured using a tape measure 1 wk postamputation and every 3 wk thereafter until 24 wk postamputation. A linear mixed model analysis was performed with weeks postamputation transformed according to the natural logarithm as predictor. Residual limb volume decreased significantly over time, with a large variation between patients. Residual limb volume does not correlate well with circumference. On average, residual limb volume decreased 200.5 mL (9.7% of the initial volume) per natural logarithm of the weeks postamputation. The decrease in residual limb volume following a transtibial amputation is substantial in the early postamputation phase, followed by a leveling off. It was not possible to determine a specific moment when the residual limb volume had stabilized.

Factors related to high-level mobility in male servicemembers with traumatic lower-limb loss.

The purpose of this study was to examine the possible relationship between factors modifiable by rehabilitation interventions (rehabilitation factors), other factors related to lower-limb loss (other factors), and high-level mobility as measured by the Comprehensive High-Level Activity Mobility Predictor (CHAMP) in servicemembers (SMs) with traumatic lower-limb loss. One-hundred eighteen male SMs with either unilateral transtibial amputation (TTA), unilateral transfemoral amputation (TFA), or bilateral lower-limb amputation (BLLA) participated. Stepwise regression analysis was used to develop separate regression models of factors predicting CHAMP score. Regression models containing both rehabilitation factors and other factors explained 81% (TTA), 36% (TFA), and 91% (BLLA) of the variance in CHAMP score. Rehabilitation factors such as lower-limb strength and dynamic balance were found to be significantly related to CHAMP score and can be enhanced with the appropriate intervention. Further, the findings support the importance of salvaging the knee joint and its effect on high-level mobility capabilities. Lastly, the J-shaped energy storage and return feet were found to improve high-level mobility for SMs with TTA. These results could help guide rehabilitation and aid in developing appropriate interventions to assist in maximizing high-level mobility capabilities for SMs with traumatic lower-limb loss.

Influence of prior activity on residual limb volume and shape measured using plaster casting: results from individuals with transtibial limb loss.

The purpose of this research was to determine whether prior activity affected the shape of a plaster cast taken of a transtibial residual limb. Plaster casts were taken twice on one day in 24 participants with transtibial limb loss, with 5 s between doffing and casting in one trial (PDI-5s) and 20 min in the other trial (PDI-20m). The ordering of the trials was randomized. The mean +/- standard deviation radial difference between PDI-20m and PDI-5s was 0.34 +/- 0.21 mm when PDI-5s was conducted first and -0.02 +/- 0.20 mm when PDI-20m was conducted first. Ordering of the trials had a statistically significant influence on the mean radial difference between the two shapes (p = 0.008). The result shows that prior activity influenced the residual limb cast shape. Practitioners should be mindful of prior activity and doffing history when casting an individual's limb for socket design and prosthetic fitting.

How does adding and removing liquid from socket bladders affect residual-limb fluid volume?

Adding and removing liquid from socket bladders is a means for people with limb loss to accommodate residual-limb volume change. We fit 19 people with transtibial amputation using their regular prosthetic socket with fluid bladders on the inside socket surface to undergo cycles of bladder liquid addition and removal. In each cycle, subjects sat, stood, and walked for 90 s with bladder liquid added, and then sat, stood, and walked for 90 s again with the bladder liquid removed. The amount of bladder liquid added was increased in each cycle. We used bioimpedance analysis to measure residual-limb fluid volume. Results showed that the preferred bladder liquid volume was 16.8 +/- 8.4 mL (mean +/- standard deviation), corresponding with 1.7% +/- 0.8% of the average socket volume between the bioimpedance voltage-sensing electrodes. Residual-limb fluid volume driven out of the residual limb when bladder liquid was added was typically not recovered upon subsequent bladder liquid removal. Of the 19 subjects, 15 experienced a gradual residual-limb fluid volume loss over the test session. Care should be taken when implementing adjustable socket technologies in people with limb loss. Reducing socket volume may accentuate residual-limb fluid volume loss.

Transfemoral amputations: the effect of residual limb length and orientation on gait analysis outcome measures.

BACKGROUND: The level of function achieved following a transfemoral amputation is believed to be affected by surgical attachment of the remaining musculature, resulting orientation of the femur, residual limb length, and eventual prosthetic fit. METHODS: Twenty-six subjects underwent gait analysis testing in the current preferred prosthesis more than twenty-four months postamputation. The femoral length and orientation angles of each subject were measured from standing postoperative radiographic scanograms. The subjects were separated into groups for analysis on the basis of the femoral shaft angles and the residual limb length ratios. Gait analysis was performed to collect kinematic and temporospatial parameters. RESULTS: A good correlation was observed between residual femoral length and trunk with regard to forward lean (r = -0.683) and lateral flexion (r = -0.628). A good correlation was also observed between residual femoral length and pelvic motion with regard to pelvic tilt (r = -0.691) and obliquity (r = -0.398). A moderate correlation was observed with speed (r = 0.550), indicating that subjects with shorter residual limbs experienced a greater excursion in the torso and pelvis, while walking at a slower self-selected pace. A significant correlation (r = 0.721, p < 0.001) was observed between the femoral shaft abduction angle and the residual femoral length; the shorter the residual limb, the more abducted it was. CONCLUSIONS: The length of the residual femur substantially influences temporospatial and kinematic gait outcomes following transfemoral amputation, and appears to be more important than femoral orientation with regard to these parameters.

Fitting very short finger stumps with silicone prosthesis: a nonsurgical method.

BACKGROUND AND AIM: The fitting of short finger stumps with silicone prosthesis is a challenge because of the suboptimal finger-prosthesis contact due to length and distal tapering of digital stumps. The purpose of this report was to describe and evaluate the Micropore(™)-polyvinyl chloride tube technique for fitting short finger stumps. TECHNIQUE: For a total of 10 patients, short finger stumps were fitted using the technique. A short length of polyvinyl chloride tube, trimmed and contoured to fit, was secured on the distal stump tip with Micropore tape. The prosthesis was worn over the polyvinyl chloride tube extension. Three different fitting methods were evaluated: fitting with and without the Micropore-polyvinyl chloride tube technique, and with the use of skin adhesive on the stump. DISCUSSION: All patients achieved a very secure prosthetic fit with the Micropore-polyvinyl chloride tube technique. No incidences of prosthesis slippage were reported at the longest follow-up of 30 months. The Micropore-polyvinyl chloride tube technique is an effective method for fitting short finger stumps.

Wound epithelium function in axolotl limb regeneration.

Axolotls (Ambystoma mexicanum) have the ability to regenerate amputated limbs. The amputation surface is promptly covered by wound epithelium (WE), which is significant for the initiation of limb regeneration. In the present study, we investigated the formation of functional WE by analyzing the migration of WE after amputation. In the center of the amputation surface, epithelial cells migrated from surrounding epidermis to form WE. Therefore, WE around the center of the amputation surface was composed of the cells with dorsal, ventral, anterior and posterior identities, and we tentatively called this WE with radial positional identities, "central WE". When regeneration was complete, central WE became the epidermis around the bifurcation between the first and second digits. In addition, when the artificial rotation of epidermis was performed before amputation, all examined limbs regenerated normally, and central WE formed the epidermis at the bifurcation between first and second digits, similarly to that in normal regeneration. On the basis of our observations, the most important factor for the initiation of regeneration is considered to be the discontinuity of positional identity existing in WE. It is possible that the location of bifurcation between first and second digits is specified by the positional discontinuity in WE.

Residual limb volume change: systematic review of measurement and management.

Management of residual limb volume affects decisions regarding timing of fit of the first prosthesis, when a new prosthetic socket is needed, design of a prosthetic socket, and prescription of accommodation strategies for daily volume fluctuations. This systematic review assesses what is known about measurement and management of residual limb volume change in persons with lower-limb amputation. Publications that met inclusion criteria were grouped into three categories: group I: descriptions of residual limb volume measurement techniques; group II: studies investigating the effect of residual limb volume change on clinical care in people with lower-limb amputation; and group III: studies of residual limb volume management techniques or descriptions of techniques for accommodating or controlling residual limb volume. We found that many techniques for the measurement of residual limb volume have been described but clinical use is limited largely because current techniques lack adequate resolution and in-socket measurement capability. Overall, limited evidence exists regarding the management of residual limb volume, and the evidence available focuses primarily on adults with transtibial amputation in the early postoperative phase. While we can draw some insights from the available research about residual limb volume measurement and management, further research is required.

Regulation of proximal-distal intercalation during limb regeneration in the axolotl (Ambystoma mexicanum).

Intercalation is the process whereby cells located at the boundary of a wound interact to stimulate proliferation and the restoration of the structures between the boundaries that were lost during wounding. Thus, intercalation is widely considered to be the mechanism of regeneration. When a salamander limb is amputated, the entire cascade of regeneration events is activated, and the missing limb segments and their boundaries (joints) as well as the structures within each segment are regenerated. Therefore, in an amputated limb it is not possible to distinguish between intersegmental regeneration (formation of new segments/joints) and intrasegmental regeneration (formation of structures within a given segment), and it is not possible to study the differential regulation of these two processes. We have used two models for regeneration that allow us to study these two processes independently, and report that inter- and intrasegmental regeneration are different processes regulated by different signaling pathways. New limb segments/joints can be regenerated from cells that dedifferentiate to form blastema cells in response to signaling that is mediated in part by fibroblast growth factor.

Sagittal plane position of the functional joint centre of prosthetic foot/ankle mechanisms.

BACKGROUND: The use of motion analysis techniques in amputee rehabilitation often utilizes kinematic data from the prosthetic limb. A problem with methods currently used is that the joint positions of the prosthetic ankle are assumed to be in the same position as that of an intact ankle. The aim of this study was to identify both traditional anatomical joint centres as well as functional joint centres in a selection of commonly used prosthetic feet. These coordinates were then compared across feet and compared to the contralateral intact ankle joint. METHODS: Six prosthetic feet were fit to a unilateral trans-tibial amputee on two separate occasions. The subject's intact limb was used as a control. Three-dimensional kinematics were collected to determine the sagittal position of the functional joint centre for the feet investigated. FINDINGS: None of the prosthetic feet had a functional joint centre that was within the 95% CI for that of an intact ankle (both x- and y-coordinate position), nor any of the other prosthetic feet investigated. The repeatability of the method was found to be adequate, with 95% CI of the difference (test-retest) of the prosthetic feet similar to that for the intact ankle and within clinically accepted levels of variability. INTERPRETATION: The motion of the prosthetic feet tested is clearly different from that of an intact ankle. Kinematic methods that assume ankle constraints based on an intact ankle are subject to systematic error as this does not reflect the real motion of the prosthetic foot.

Developing a quantitative measurement system for assessing heterotopic ossification and monitoring the bioelectric metrics from electrically induced osseointegration in the residual limb of service members.

Poor prosthetic fit is often the result of heterotopic ossification (HO), a frequent problem following blast injuries for returning service members. Osseointegration technology offers an advantage for individuals with significant HO and poor socket tolerance by using direct skeletal attachment of a prosthesis to the distal residual limb, but remains limited due to prolonged post-operative rehabilitation regimens. Therefore, electrical stimulation has been proposed as a catalyst for expediting skeletal attachment and the bioelectric effects of HO were evaluated using finite element analysis in 11 servicemen with transfemoral amputations. Retrospective computed tomography (CT) scans provided accurate reconstructions, and volume conductor models demonstrated the variability in residual limb anatomy and necessity for patient-specific modeling to characterize electrical field variance if patients were to undergo a theoretical osseointegration of a prosthesis. In this investigation, the volume of HO was statistically significant when selecting the optimal potential difference for enhanced skeletal fixation, since higher HO volumes required increased voltages at the periprosthetic bone (p = 0.024, r = 0.670). Results from Spearman's rho correlations also indicated that the age of the subject and volume of HO were statistically significant and inversely proportional, in which younger service members had a higher frequency of HO (p = 0.041, r = -0.622). This study demonstrates that the volume of HO and age may affect the voltage threshold necessary to improve current osseointegration procedures.

Inter- and intra-observer reproducibility and validity of an indirect volume measurement in transtibial amputees.

The objective of the study was to assess the measurement properties of an indirect volumetric measurement using segmental circumferential measurements fitted into a formula of a truncated cone (Sitzia's method) in long-term transtibial amputees. Twenty-eight participants with a transtibial amputation >1 year participated in the study. Two observers measured stump volume twice, two weeks apart, using both Sitzia's method and the water displacement volumetric method (criterion standard test). The mean differences and upper and lower limits of agreement between the water displacement volumetric method and Sitzia's method, between the first and second assessment, and between both assessors were calculated. Intra-class correlation coefficients (ICCs) were derived from random-effects two-way analysis of variance. Inter-observer agreements of both methods were high and ranged from 86-96%. Intra-observer agreement ranged between 57% and 71%. In both methods the inter- and intra-observer differences were not significant. ICCs ranged from 0.88-0.99 and were better for inter-observer compared to intra-observer reproducibility. Lower stump volumes were observed in Sitzia's method compared to water displacement volumetric method, with high ICC's (0.92-0.95) between both methods. Although Sitzia's method systematically underestimates stump volume, it is a reliable and feasible alternative to the criterion standard test. To determine its validity to detect (longitudinal) differences in stump volume, follow-up research is needed in participants with recent amputations.

Variation in measurements of transtibial stump model volume: a comparison of five methods.

OBJECTIVE: To determine the right moment for fitting the first prosthesis, it is necessary to know when the volume of the stump has stabilized. The aim of this study is to analyze variation in measurements of transtibial stump model volumes using the water immersion method, the Design TT system, the Omega Tracer system, circumferential measurements, and anthropometric measurements. DESIGN: Nine stump models were measured on two occasions, each consisting of two sessions. In each session, two observers measured the model using each of the five methods. The grand mean volume for each method was calculated. Variance components and their two-way interactions were calculated of the measurement conditions. Repeatability coefficients were calculated for each method. RESULTS: The grand means of the five methods show systematic differences in volume measurements. Error variance was small (6.4%) relative to the total variance. Method and interaction between stump model and method contributed 82.6% to the error variance. Repeatability coefficients of the methods ranged from 45 ml for the Omega Tracer system to 155 ml for the anthropometric measurements. CONCLUSIONS: Error variation in measurement results can be attributed for 82.6% to measurement method and interaction between stump model and method. The Omega Tracer system had the smallest repeatability coefficient, indicating that it is the most reliable method.

A means to accommodate residual limb movement during optical scanning: a technical note.

A technique is described for correcting for subject movement while imaging the residual limb of a person with a transtibial amputation. Small reflective markers were placed on the residual limb, and then their motions tracked during scanning using two stationary cameras. The marker position measurements were used to generate appropriate translational and rotational transformation matrices so that limb motion could be corrected for during the 1.5-s scan interval. Evaluation tests showed good performance for moderate (2-4 mm) to high (5-8 mm) motion cases. The difference in mean absolute cross-sectional area between the test scan and a stationary reference scan was reduced by approximately one half when motion correction was used compared with when motion correction was not used. The algorithm broke down for exaggerated motion ( >or= 9 mm) cases, particularly in areas outside the region encompassed by the markers. The developed method is useful in prosthetics research where high resolution shape measurement is needed, for example in cases where residual limb shape or volume change is of interest.