The Hawthorne effect, a subcategory of reactivity, causes human behavior to change when under observation. Such an effect may apply to gait variation of persons with prosthetics or orthotics devices. This study investigated whether the presence of observers directly affects the gait pattern of users of lower limb prostheses. Within-subject intervention study. Primary outcome measures were gait parameters of initial double support time and upper body lateral tilt angle, which were collected with a mobile sensor attached to the subjects’ back. To make subjects feel unwatched, a certain amount of deception was necessary, and two different conditions were created and statistically compared against each other: one in which the subjects were initially unaware of the attention of observers and another one in which the same subjects were aware of a group of observers. Data from two subjects using trans-femoral prosthesis are reported. Findings included a change in step initial double support percentage by up to 14.2% (p = 0.019). Considerable changes were also noted in secondary outcome measures including speed, stride length, and stride symmetry. A reactivity effect of observation exists in prosthetics gait analysis. More comprehensive studies may be motivated by these preliminary findings. Results of this study suggest that users of lower limb prostheses walk differently when their gait is being assessed (e.g. in the prosthetist’s office) than in situations without observers. This may in part explain the clinical experience that modifications of prosthetic fit or alignment provide only short-term betterment.

It has long been reported that a range of prosthesis alignments is acceptable in trans-tibial prosthetics. This range was shown to be smaller when walking on uneven surfaces. It has also been argued that findings on gait with prostheses that were obtained under laboratory conditions are limited in their applicability to real-life environments. This study investigated the hypothesis that efforts to compensate for suboptimal alignments by active users of trans-tibial prostheses become less effective when levels of physical exertion increase. A 2 × 2 repeated-measures analysis of variance was conducted to compare the effects of physical exertion and subtle alignment perturbations on gait with trans-tibial prostheses. The gait of eight subjects with trans-tibial amputation was analyzed when walking with two different prosthesis alignments and two different physical exertion levels. The main and interaction effects were statistically evaluated. Bilateral step length symmetry and measures of step variability within the same leg were found to be affected by the intervention. There was no significant effect on index variables that combined kinematic or kinetic measures. Findings showed that persons with trans-tibial prostheses responded heterogeneously to the interventions. For most variables, the research hypothesis could not be confirmed. Findings support the practice of allotting several sessions to the alignment of trans-tibial prostheses, as users’ gait responds differently to perturbations when external factors (e.g. exertion) change. Furthermore, the found inhomogeneity in the population of persons with trans-tibial amputation supports the use of technical gait assessment methods in clinical practice.

A variety of prescribed accommodation periods have been used in published prosthesis intervention studies that have examined biomechanical outcomes. Few investigators included repeated measurements in their study design, leaving questions as to how measured outcomes change as amputees acclimate to a new prosthesis. This paper is the product of our investigation as to whether measured gait variables were affected by the duration of accommodation period, and to assess the relationship between measured outcomes and the subjective perception of the participants. A sample of transtibial amputees were recruited for this study. Gait data was collected by wearable sensor repeatedly, starting immediately after fitting the interventional foot and extending over a subsequent four days. Participants indicated their perceived accommodation quality on a visual analog scale (VAS). A total of twelve commonly used spatiotemporal gait parameters were analyzed. Friedman tests were used to determine overall differences across time points in both early (one hour) and late (day two through five) accommodation phases, for each gait variable. Statistically significant changes across the early phase were found for variables gait speed χ²(2)=8.000, p=0.018, cadence χ²(2)=7.185, p=0.028, and double support time on the sound side χ²(2)=8.615, p=0.013. Across days two through five, no gait variable significantly changed. VAS scores correlated strongly with step count (r=1.000, p<0.001) and cadence (r=0.857, p=0.014). Longer accommodation periods resulted in less deviations of gait variables for the clinical assessment in the process of prosthetic rehabilitation. Trying out prosthetic interventions for less than one hour has yielded unreliable outcomes.

Introduction: The quality of lower-limb prosthetic alignment cannot easily be measured directly but may be described by its effects on gait comfort and efficiency. It is known that gait stability and step variability are correlated, as are gait stability and prosthetic alignment. This study investigated the hypothesis that prosthetic alignment and step variability are correlated. This would have the implication that step variability can be measured to assess the quality of prosthetic alignment (and possibly other relevant factors such as prosthetic fit and componentry selection). Materials and Methods: Twelve experienced users of transtibial prostheses were subjected to a protocol that introduced malalignments of their prosthetic ankle plantarflexion angle in a randomized crossover design. Perceived alignment quality was recorded via a visual analog scale. Step-by-step variability in horizontal ground reaction forces and axial ankle torsion moment was measured using a prosthesis-integrated load cell and was statistically compared with the degree of misalignment by bivariate correlation analysis. Results: Findings suggest that variance in axial torsion moment and step duration may be correlated to alignment quality. Conclusions: Subjective patient feedback is the recommendable criterion for alignment assessment in active and experienced users of prostheses. Further research is recommended before step variance may help assess prosthetic alignment quality in patients with less experience in prosthetic use.

Background: In people living with limb loss, addressing the resulting functional deficit with prostheses increases the risk for secondary conditions such as pressure sores, impaired blood perfusion, and injuries from accidental falls. Any of those occurrences can render the prosthesis temporarily useless, making it challenging for users to engage in many activities of daily life, including work, exercise, and social participation. Many of the described issues originate at the interface between residual limb and prosthetic socket, where the objectives of sufficient weight distribution and suspension are conflicting with the necessity to facilitate heat exchange and limit contact pressure and friction.Recently, prosthesis liners that contain phase-change material have become commercially available, holding the promise that the micro climate at the interface between the residual limb skin and the prosthetic socket can be regulated to reduce the users’ tendency to sweat. Preliminary studies on these liners indicate that the socket temperatures inside the socket stayed lower and rose slower than in conventional liners. However, the clinical relevance of those findings remains unclear.The purpose of this study is to investigate whether longer (6+ months) periods of use of phase-change material based temperature-control liners have clinically meaningful effects.Methods: The protocol is a double-blind longitudinal cross-over research design. A sample of trans-tibial prosthesis users are wearing their regular gel or silicone liners for six months and phase-change material liners for another six months in a randomized sequence. Their prostheses is equipped with activity monitors to detect days when they could not wear their prosthesis. In six-week intervals, individuals’ activity, physical performance, and overall prosthesis assessment is recorded using standardized methods.Discussion: Expected results will inform prescription and reimbursement practice of phase-change material-based prosthesis liners and will help improve and economize prosthetic fitting for people with limb loss. The design and duration of the protocol, including randomization, blinding, and within-subject comparison, will generate scientific evidence of a comparably high level. Inclusion of a comparably large sample and different climates, e.g. across all four seasons, will make findings applicable to a large number of prosthesis users.Trial registration: Clinicaltrials.gov,NCT03428815. Registered on 12 February 2018.