Testing the Reliability of Optical Coherence Tomography to Measure Epidermal Thickness and Distinguish Volar and Nonvolar Skin.

In persons with limb loss, prosthetic devices cause skin breakdown, largely because residual limb skin (nonvolar) is not intended to bear weight such as palmoplantar (volar) skin. Before evaluation of treatment efficacy to improve skin resiliency, efforts are needed to establish normative data and assess outcome metric reliability. The purpose of this study was to use optical coherence tomography to (i) characterize volar and nonvolar skin epidermal thickness and (ii) examine the reliability of optical coherence tomography. Four orientations of optical coherence tomography images were collected on 33 volunteers (6 with limb loss) at 2 time points, and the epidermis was traced to quantify thickness by 3 evaluators. Epidermal thickness was greater (P < .01) for volar skin (palm) (265.1 ± 50.9 µm, n = 33) than for both nonvolar locations: posterior thigh (89.8 ± 18.1 µm, n = 27) or residual limb (93.4 ± 27.4 µm, n = 6). The inter-rater intraclass correlation coefficient was high for volar skin (0.887-0.956) but low for nonvolar skin (thigh: 0.292-0.391, residual limb: 0.211-0.580). Correlation improved when comparing only 2 evaluators who used the same display technique (palm: 0.827-0.940, thigh: 0.633-0.877, residual limb: 0.213-0.952). Despite poor inter-rater agreement for nonvolar skin, perhaps due to challenges in identifying the dermal-epidermal junction, this study helps to support the utility of optical coherence tomography to distinguish volar from nonvolar skin.

The development of rating scales to evaluate experiential prosthetic foot preference for people with lower limb amputation.

BACKGROUND: Selection of a foot is an important aspect of prosthetic prescription and vital to maximizing mobility and functional goals after lower limb amputation. Development of a standardized approach to soliciting user experiential preferences is needed to improve evaluation and comparison of prosthetic feet. OBJECTIVE: To develop rating scales to assess prosthetic foot preference and to evaluate use of these scales in people with transtibial amputation after trialing different prosthetic feet. DESIGN: Participant-blinded, repeated measures crossover trial. SETTING: Veterans Affairs and Department of Defense Medical Centers, laboratory setting. PARTICIPANTS: Seventy-two male prosthesis users with unilateral transtibial amputation started, and 68 participants completed this study. INTERVENTIONS: Participants trialed three mobility-level appropriate commercial prosthetic feet briefly in the laboratory. MAIN OUTCOME MEASURES: "Activity-specific" rating scales were developed to assess participants' ability with a given prosthetic foot to perform typical mobility activities (eg, walking at different speeds, on inclines, and stairs) and "global" scales to rate overall perceived energy required to walk, satisfaction, and willingness to regularly use the prosthetic foot. Foot preference was determined by comparing the rating scale scores, after laboratory testing. RESULTS: The greatest within-participant differences in scores among feet were observed in the "incline" activity, where 57% ± 6% of participants reported 2+ point differences. There was a significant association (p < .05) between all "activity-specific" rating scores (except standing) and each "global" rating score. CONCLUSIONS: The standardized rating scales developed in this study could be used to assess prosthetic foot preference in both the research and clinical settings to guide prosthetic foot prescription for people with lower limb amputation capable of a range of mobility levels.

Relationship between phantom limb pain, function, and psychosocial health in individuals with lower-limb loss.

INTRODUCTION: The adverse influence of chronic pain on function and psychological health in the general population is well understood. However, the relationship between phantom limb pain (PLP) after limb loss with function and psychological health is less clear. The study purpose was to assess the influences of PLP presence and intensity on function and psychosocial health in individuals with lower-limb loss (LLL). METHODS: One hundred two individuals with major LLL completed a study-specific questionnaire on the presence and intensity of their PLP. The Patient-Reported Outcomes Measurement Information System -29 questionnaire was also administered. RESULTS: Of 102 participants, 64% reported PLP, with a mean intensity of 4.8 ± 2.3 out of 10. Individuals with vs. without PLP demonstrated significantly greater sleep disturbances ( p = 0.03), whereas the differences in function, fatigue, pain interference, depressive symptoms, anxiety, or ability to participate in social roles and activities were not statistically different between groups ( p > 0.05). Of note, mean scores for many of the Patient-Reported Outcomes Measurement Information System-29 short forms among the current sample were similar to the mean of the general population, minimizing the potential clinical impact of PLP on these domains. CONCLUSIONS: Our findings indicate a lack of meaningful associations between PLP presence or intensity with function, and psychosocial health among individuals with LLL. These findings conflict with previous research suggesting an adverse relationship between PLP, function, and psychosocial health after limb loss.

The relationship between residual limb health, motion within the socket, and prosthetic suspension.

Residual limb health is critical for continued prosthesis use; however, many prosthesis users experience skin-related breakdown. The interface between the residual limb and the prosthetic socket sets the local mechanical environment and plays a role in skin stresses. Motion of the residual limb in the socket adds additional mechanical strain on the limb. This article explores the relationship between motion of the limb in the socket and residual limb health. We evaluated current methods for assessing residual limb health and motion of the residual limb in the socket and compared these evaluations across different prosthetic suspension systems. While few direct studies comparing residual limb health and motion exist, it has been shown that elevated vacuum suspension systems result in both improved residual limb health compared to passive suction and pin-lock systems and decreased motion compared to passive suction, pin-lock, knee sleeve, and anatomical suspension systems. While motion and health have not been directly linked, elevated vacuum suspension may demonstrate a relationship that reduced motion of the residual limb in the socket improves residual limb health. Further evaluation in this area is necessary to more completely and directly understand the relationship between residual limb motion and residual limb health.

Exoskeletal solutions to enable mobility with a lower leg fracture in austere environments.

The treatment and evacuation of people with lower limb fractures in austere environments presents unique challenges that assistive exoskeletal devices could address. In these dangerous situations, independent mobility for the injured can preserve their vital capabilities so that they can safely evacuate and minimize the need for additional personnel to help. This expert view article discusses how different exoskeleton archetypes could provide independent mobility while satisfying the requisite needs for portability, maintainability, durability, and adaptability to be available and useful within austere environments. The authors also discuss areas of development that would enable exoskeletons to operate more effectively in these scenarios as well as preserve the health of the injured limb so that definitive treatment after evacuation will produce better outcomes.

Altering the tuning parameter settings of a commercial powered prosthetic foot to increase power during push-off may not reduce collisional work in the intact limb during gait.

BACKGROUND: Increased knee osteoarthritis risk in patients with unilateral lower extremity limb loss is attributed to increased intact limb loading. Modulating powered ankle prosthesis push-off power may be an effective way to modulate intact limb loading. We examined how changes in the parameter settings of a commercial prosthetic ankle affect power delivery during push-off and the resulting collisional work experienced by the intact limb in persons with unilateral lower extremity limb loss. METHODS: Five subjects with unilateral transtibial amputation were fitted with a commercially available powered ankle prosthesis (Ottobock Empower). Subjects walked on a treadmill in seven conditions, where ankle power delivery settings were adjusted using methods accessible to clinicians. Kinetics and kinematics data were collected. RESULTS: Standard adjustment of parameter settings within the prosthetic foot did not alter timing of peak prosthesis power or intact limb collisional work but did have a significant effect on the magnitude of positive prosthesis ankle work. Increased prosthesis work did not decrease intact limb collisional work as predicted. CONCLUSIONS: Altering the parameter settings on a commercial powered ankle prosthesis affected the magnitude, but not the timing, of power delivered. Increased prosthesis push-off power did not decrease intact limb loading.

Recent Progress in Animal Studies of the Skin- and Bone-integrated Pylon With Deep Porosity for Bone-Anchored Limb Prosthetics With and Without Neural Interface.

INTRODUCTION: The three major unresolved problems in bone-anchored limb prosthetics are stable, infection-free integration of skin with a percutaneous bone implant, robust skeletal fixation between the implant and host bone, and a secure interface of sensory nerves and muscles with a prosthesis for the intuitive bidirectional prosthetic control. Here we review results of our completed work and report on recent progress. MATERIALS AND METHODS: Eight female adult cats received skin- and bone-integrated pylon (SBIP) and eight male adult cats received SBIP-peripheral neural interface (PNI) pylon into the right distal tibia. The latter pylons provided PNI for connection between a powered sensing transtibial prosthesis and electrodes in residual soleus muscle and on residual distal tibial nerve. If signs of infection were absent 28-70 days after implantation, cats started wearing a passive prosthesis. We recorded and analyzed full-body mechanics of level and slope locomotion in five cats with passive prostheses and in one cat with a powered sensing prosthesis. We also performed histological analyses of tissue integration with the implants in nine cats.Four pigs received SBIPs into the left hindlimb and two pigs-into the left forelimb. We recorded vertical ground reaction forces before amputation and following osseointegration. We also conducted pullout postmortem tests on the implanted pylons. One pig received in dorsum the modified SBIPs with and without silver coating. RESULTS: Six cats from the SBIP groups had implant for 70 days. One cat developed infection and did not receive prosthesis. Five cats had pylon for 148 to 183 days, showed substantial loading of the prosthesis during locomotion (40.4% below presurgery control), and demonstrated deep ingrowth of skin and bone tissue into SBIP (over 60%). Seven of eight cats from the SBIP-PNI group demonstrated poor pylon integration without clinical signs of infection. One cat had prosthesis for 824 days (27 months). The use of the bidirectionally controlled prosthesis by this animal during level walking demonstrated increased vertical loading to nearly normal values, although the propulsion force was significantly reduced.From the study on pigs, it was found that symmetry in loading between the intact and prosthetic limbs during locomotion was 80 ± 5.5%. Skin-implant interface was infection-free, but developed a stoma, probably because of the high mobility of the skin and soft tissues in the pig's thigh. Dorsal implantation resulted in the infection-free deep ingrowth of skin into the SBIP implants. CONCLUSIONS: Cats with SBIP (n = 5) and SBIP-PNI (n = 1) pylons developed a sound interface with the residuum skin and bone and demonstrated substantial loading of prosthetic limb during locomotion. One animal with SBIP developed infection and seven cats with SBIP-PNI demonstrated poor bone integration without signs of infection. Future studies of the SBIP-PNI should focus on reliability of integration with the residuum. Ongoing study with pigs requires decreasing the extra mobility of skin and soft tissues until the skin seal is developed within the SBIP implant.

Increasing prosthetic foot energy return affects whole-body mechanics during walking on level ground and slopes.

Prosthetic feet are designed to store energy during early stance and then release a portion of that energy during late stance. The usefulness of providing more energy return depends on whether or not that energy transfers up the lower limb to aid in whole body propulsion. This research examined how increasing prosthetic foot energy return affected walking mechanics across various slopes. Five people with a uni-lateral transtibial amputation walked on an instrumented treadmill at 1.1 m/s for three conditions (level ground, +7.5°, -7.5°) while wearing a prosthetic foot with a novel linkage system and a traditional energy storage and return foot. The novel foot demonstrated greater range of motion (p = 0.0012), and returned more energy (p = 0.023) compared to the traditional foot. The increased energy correlated with an increase in center of mass (CoM) energy change during propulsion from the prosthetic limb (p = 0.012), and the increased prosthetic limb propulsion correlated to a decrease in CoM energy change (i.e., collision) on the sound limb (p < 0.001). These data indicate that this novel foot was able to return more energy than a traditional prosthetic foot and that this additional energy was used to increase whole body propulsion.

Standardizing Methodology for Research with Uneven Terrains Focused on Dynamic Balance During Gait.

This research tested a reproducible uneven walkway designed to destabilize human gait. Ten participants walked 30 times over even and uneven (7.3 × .08 m, sequentially-placed wooden blocks in a rotating pattern, 1-cm thick rubber mat) walkways. A full-body marker set and 8-camera motion capture system recorded limb kinematics. MatLab 2013b was used to calculate measures of gait stability: angular momentum, margin of stability, step width variability, CoM height, toe clearance, lateral arm swing. The minimum number of strides necessary to minimize intraparticipant variability was calculated via the interquartile range/median ratio (IMR) at 25% and 10% thresholds for each measure. A paired t test tested for significance between terrains (P < .05). The uneven walkway significantly destabilized gait as seen by increases in: coronal and sagittal plane angular momentum, step width variability, and toe clearance. We found no significant difference with the margin of stability between the 2 terrains possibly due to compensatory strategies (eg, lateral arm swing, trunk sway, step width). Recording a minimum of 10 strides per subject will keep each variable between the 25% and 10% IMR thresholds. In conclusion, the uneven walkway design significantly destabilizes human gait and at least 10 strides should be collected per subject.

Modeling the effect of a prosthetic limb on 4-km pursuit performance.

The individual pursuit is a 4-km cycling time trial performed on a velodrome. Parathletes with transtibial amputation (TTA) have lost physiological systems, but this may be offset by the reduced aerodynamic drag of the prosthesis. This research was performed to understand the effect of a unilateral TTA on Olympic 4-km pursuit performance. A forward-integration model of pursuit performance explored the interplay between power loss and aerodynamic gains in parathletes with TTA. The model is calibrated to a 4-km pursuit time of 4:10.5 (baseline), then adjusted to account for a TTA. Conditions simulated were based on typical pedal asymmetry in TTA (AMP), if foot stiffness were decreased (FLEX), if pedaling asymmetries were minimized (ASYM), if the prosthesis were aerodynamically optimized (AERO), if the prosthesis had a cosmetic cover (CC), and if all variables were optimized (OPT). A random Monte Carlo analysis was performed to understand model precision. Four-kilometer pursuit performances predicted by the model were 4:10.5, 4:20.4, 4:27.7, 4:09.2, 4:19.4, 4:27.9, and 4:08.2 for the baseline, AMP, FLEX, ASYM, AERO, CC, and OPT models, respectively. Model precision was ±3.7 s. While the modeled time decreased for ASYM and OPT modeled conditions, the time reduction fell within model precision and therefore was not significant. Practical application of these results suggests that parathletes with a TTA could improve performance by minimizing pedaling asymmetry and/or optimizing aerodynamic design, but, at best, they will have performance similar to that of intact cyclists. In conclusion, parathletes with TTA do not have a net advantage in the individual pursuit.

Lower limb muscle activity during forefoot and rearfoot strike running techniques.

PURPOSE/BACKGROUND: Distance running offers a method to improve fitness but also has a risk of lower limb overuse injuries. Foot strike technique has been suggested as a method to alter loading of the lower limb and possibly minimize injury risk. However, there is a dearth of information regarding neuromuscular response to variations in running techniques. The purpose of this investigation was to compare the EMG activity that occurs during FFS running and RFS running, focusing on the biceps femoris, semitendenosis, rectus femoris, vastus medialis oblique, tibialis anterior (TA), medial head of gastrocnemeus (MGas), lateral head of gastrocnemius (LGas), and soleus. METHODS: healthy adults (6 male, 8 female; age, 24.2 ± 0.8 years, height 170.1 ± 7.8 cm; mass 69.8 ±10.9 kg; Body Mass Index 24.1 ± 3.0 kg·m2) participated in the study. All participants performed a RFS and FFS running trial at 8.85 kph. A 3D motion capture system was used to collect kinematic data and electromyography was used to define muscle activity. Two-tailed paired t-tests were used to examine differences in outcomes between RFS and FFS conditions. RESULTS: The ankle was significantly more plantarflexed during FFS running (p = .0001) but there were no significant differences in knee and hip angles (p = .618 & .200, respectively). There was significantly less activity in tibialis anterior (TA) (p < .0001) and greater activity in the MGas (p= .020) during FFS running. The LGas and soleus did not change activity (p = .437 & .490, respectively). CONCLUSIONS: FFS running demonstrated lower muscular activity in the TA and increased activation in the MGas. CLINICAL RELEVANCE: FFS and RFS running have the potential to off-load injury prone tissues by changing between techniques. However, future studies will be necessary to establish more direct mechanistic connections between running technique and injury.

Symmetrical kinematics does not imply symmetrical kinetics in people with transtibial amputation using cycling model.

People with amputation move asymmetrically with regard to kinematics (joint angles) and kinetics (joint forces and moments). Clinicians have traditionally sought to minimize kinematic asymmetries, assuming kinetic asymmetries would also be minimized. A cycling model evaluated locomotor asymmetries. Eight individuals with unilateral transtibial amputation pedaled with 172 mm-length crank arms on both sides (control condition) and with the crank arm length shortened to 162 mm on the amputated side (CRANK condition). Pedaling kinetics and limb kinematics were recorded. Joint kinetics, joint angles (mean and range of motion [ROM]), and pedaling asymmetries were calculated from force pedals and with a motion capture system. A one-way analysis of variance with tukey post hoc compared kinetics and kinematics across limbs. Statistical significance was set to p

Pedaling asymmetries in cyclists with unilateral transtibial amputation: effect of prosthetic foot stiffness.

Cyclists with unilateral transtibial amputation (CTA) provide a unique model to study integration of the neuromuscular and bicycle systems while having the option to modify this integration via the properties of the prosthesis. This study included eight CTA and nine intact cyclists. The cyclists pedaled on a stationary bicycle with instrumented force pedals. The CTA group pedaled with a stiff or flexible prosthetic foot during a simulated time trial and a low difficulty condition. During the time trial condition, pedaling with the flexible foot resulted in force and work asymmetries of 11.4% and 30.5%, the stiff foot displayed 11.1% and 21.7%, and the intact group displayed 4.3% and 4.2%, respectively. Similar trends were shown in the low difficulty condition. These data suggest foot stiffness has an effect on cycling symmetry in amputees.

The biomechanics of cycling with a transtibial amputation: Recommendations for prosthetic design and direction for future research.

People with amputations may find cycling advantageous for exercise, transportation and rehabilitation. The reciprocal nature of stationary cycling also makes it a viable model for research in motor control because the body is supported by the saddle allowing the researcher to focus on the cyclic movement of the legs without the confounding variable of balance. The purpose of this article is to provide an overview of the cycling task in intact cyclists and relate this information to understanding the challenges faced by cyclists with transtibial amputations (CTA). Ongoing research into the biomechanics of CTAs will be summarized to expose the differences between intact and CTA cycling mechanics, asymmetries between limbs of CTAs as well as neuromuscular adaptation following amputation. The article will include recommendations for prosthetic design and modification of the bicycle to improve cycling performance for CTA at all experience levels.

Recovery nutrition: timing and composition after endurance exercise.

Consumption of macronutrients, particularly carbohydrate (CHO) and possibly a small amount of protein, in the early recovery phase after endurance exercise can enhance muscle glycogen resynthesis rates. A target of at least 1.2 g x kg body weight(-1) x h(-1) CHO (over several hours) is suggested. This rate of CHO intake could be sustained with liquid, gel, or solid food rich in CHO for maximizing muscle glycogen. Whether the coingestion of protein with CHO compared with isocaloric CHO results in meaningful differences in glycogen replenishment that translate into subsequent performance enhancement is equivocal. Advantages of added protein with CHO in reducing true muscle damage from endurance exercise remain to be verified. There are, however, no apparent contraindications for using milk or specialty CHO/protein/amino acid products either. Future investigations that examine signaling mechanisms within muscle should be conducted in parallel with translational evidence in humans.