Margrit R. Meier

The Effects of Prosthetic Foot Roll-Over Shape Arc Length on the Gait of Trans-Tibial Prosthesis Users:

The Shape&Roll prosthetic foot was used to examine the effect of roll-over shape arc length on the gait of 14 unilateral trans-tibial prosthesis users. Simple modifications to the prosthetic foot were used to alter the effective forefoot rocker length, leaving factors such as alignment, limb length, and heel and mid-foot characteristics unchanged. Shortening the roll-over shape arc length caused a significant reduction in the maximum external dorsiflexion moment on the prosthetic side at all walking speeds (p < 0.001 for main effect of arc length), due to a reduction in forefoot leverage (moment arm) about the ankle. Roll-over shape arc length significantly affected the initial loading on the sound limb at normal and fast speeds (p = 0.001 for the main effect of arc length), with participants experiencing larger first peaks of vertical ground reaction forces on their sound limbs when using the foot with the shortest effective forefoot rocker arc length. Additionally, the difference between step lengths on the sound and prosthetic limbs was larger with the shortest arc length condition, although this difference was not statistically significant (p = 0.06 for main effect). It appears that prosthesis users may experience a drop-off effect at the end of single limb stance on prosthetic feet with short roll-over shape arc lengths, leading to increased loading and/or a shortened step on the contralateral limb.

Alignment of trans–tibial prostheses based on roll–over shape principles

The authors examined the rollover shape alignment hypothesis, which states that prosthetic feet are aligned by matching their rollover shapes with an “ideal” shape. The “ideal” shape was considered to be the rollover shape of the ablebodied footankle system. An alignment algorithm and computational alignment system were developed to set transtibial alignments based on this hypothesis. Three prosthetic feet with considerably different rollover shapes were either aligned using the alignment system or not aligned (i.e. used previous foots alignment), and then were aligned by a team of prosthetists. No significant differences were found between rollover shapes aligned by the computational alignment system and those based on standard clinical techniques (p = 0.944). Significant differences were found between the “no alignment” shapes and the prosthetist alignment shapes (p = 0.006), and between the “no alignment” shapes and the computational alignment system shapes (p = 0.024). The results of the experiment support the hypothesis that the goal of alignment is to match the prosthetic foots rollover shape, as closely as possible, with an “ideal” shape. The hypothesis is also supported by its ability to explain the results of previous studies. Using an “ideal” rollover shape or surface as a goal for prosthetic alignment could lead to a priori alignment, eliminating the need for alignment hardware in some cases. Being able to build the alignment into a prosthesis without special hardware could be beneficial in lowincome countries and in the fabrication of lightweight prostheses for the elderly.

Temporal symmetries during gait initiation and termination in nondisabled ambulators and in people with unilateral transtibial limb loss

This study investigated the temporal characteristics of gait initiation and gait termination. Ten nondisabled adult volunteers and ten people with unilateral transtibial limb loss performed starting and stopping for slow, normal, and fast walking speeds. We used kinematic and anthropomorphic data to determine the body center of mass (BCOM) position of each subject. The BCOM acceleration was derived by double-differentiating the position data. An averaged BCOM acceleration was calculated by a filtering of the instantaneous acceleration data at a cutoff frequency set by the cadence for elimination of the step-to-step variation. We used this averaged acceleration to calculate the time the volunteers needed to initiate and terminate gait. The results support the hypothesis that both nondisabled ambulators and the subjects with unilateral transtibial limb loss initiate and terminate gait in approximately two steps, regardless of the steady-state walking speed.

Obstacle course: Users' maneuverability and movement efficiency when using Otto Bock C-Leg, Otto Bock 3R60, and CaTech SNS prosthetic knee joints

The performance and movement efficiency of prosthesis users while traversing a multisectional obstacle course (OC) were evaluated using a crossover design with random allocation of three prosthetic knee joints: the SNS (CaTech; Dayton, Ohio) the C-Leg (Otto Bock; Duderstadt, Germany), and the 3R60 (Otto Bock). Twelve users completed the OC twice with each joint, once without and once with a mental loading task (MLT). The performance was objectively assessed using time measurement from digital video recordings, and the Total Heart Beat Index was used to estimate movement efficiency. A 1 mo familiarization period was provided for each knee joint before data collection. It took longer to complete the OC with the 3R60 compared with either the SNS or the C-Leg. No significant time differences were found between the C-Leg and the SNS, but differences between the 3R60 and the SNS (slalom and rock sections) and between the 3R60 and the C-Leg (rock section) were observed. Within the simulated sand section, two participants fell with the C-Leg, one with the 3R60, and none with the SNS. Movement efficiency without MLT was similar between all joints, but with an MLT a significant decrease in movement efficiency was observed with the C-Leg. Previous experience using an SNS had no influence on the results.

The 'Shape&Roll' Prosthetic Foot: Ii. Field Testing in El Salvador

A field test was performed in El Salvador to evaluate the usefulness of the Shape&Roll prosthetic foot, a foot developed for low-income countries, involving 12 participants. Quantitative gait parameters were measured with a Direct Ultrasound Ranging System (DURS). Qualitative information was obtained from questionnaires administered before and after a three-week trial. The results indicate that the Shape&Roll foot widened the speed range of all participants. According to the questionnaires, the Shape&Roll foot eases walking, enabling participants to walk significantly longer distances. The participants rated its roll-over as very natural and smooth, resulting in a self-perceived reduced walking effort. Handling inclined and uneven surfaces was also rated superior to their current Solid Ankle Cushioned Heel (SACH)-like feet.

Systematic review of effects of current transtibial prosthetic socket designs—Part 2: Quantitative outcomes

This review is an attempt to untangle the complexity of transtibial prosthetic socket fit, determine the most important characteristic for a successful fitting, and perhaps find some indication of whether a particular prosthetic socket type might be best for a given situation. Further, it is intended to provide directions for future research. We followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and used medical subject headings and standard key words to search for articles in relevant databases. No restrictions were made on study design or type of outcome measure. From the obtained search results (n = 1,863), 35 articles were included. The relevant data were entered into a predefined data form that incorporated the Downs and Black risk of bias assessment checklist. Results for the qualitative outcomes (n = 19 articles) are synthesized. Total surface bearing sockets lead to greater activity levels and satisfaction in active persons with amputation, those with a traumatic cause of amputation, and younger persons with amputation than patellar tendon bearing sockets. Evidence on vacuum-assisted suction and hydrostatic sockets is inadequate, and further studies are much needed. To improve the scientific basis for prescription, comparison of and correlation between mechanical properties of interface material, socket designs, user characteristics, and outcome measures should be conducted and reported in future studies.

Roll-over shapes of the ankle-foot and knee-ankle-foot systems of able-bodied children

BACKGROUND The roll-over shape is the effective rocker shape that a lower limb system conforms to during a step. The roll-over shape concept has been explored in detail in adults and has been successfully used in the design, evaluation, and alignment of lower limb prostheses and orthoses. No such analysis exists for the pediatric population. Therefore, the purpose of this study was to investigate the ankle-foot and knee-ankle-foot roll-over shapes in able-bodied children, values that could serve as tools for design and evaluation of lower limb pediatric prostheses and orthoses. METHODS This study describes a multi-center retrospective review of existing motion analysis data (n=153 from three centers). Roll-over shapes were calculated by transforming center of pressure data from a laboratory-based coordinate system into two body-based coordinate systems. Roll-over shapes were then characterized using a circular arc model. Best-fit radii of roll-over shapes for children in three age groups (3-7 years, 8-11 years, and 12-17 years) were compared using the Kruskal-Wallis test. FINDINGS No significant changes were found in roll-over shape radii between the three age groups (P=0.54 for ankle-foot roll-over shape radii; P=0.12 for knee-ankle-foot roll-over shape radii). The weighted mean of median radii for ankle-foot and knee-ankle-foot roll-over shapes from the three centers were approximately 22% and 17% of body stature, values similar to those seen in adults. INTERPRETATION Children produce nearly circular knee-ankle-foot roll-over shapes at a young age that are similar to those seen in adults when scaled by body stature.

Development of inexpensive prosthetic feet for high-heeled shoes using simple shoe insole model

The large majority of prosthetic feet are aimed at low-heeled shoes, with a few models allowing a heel height of up to 5 cm. However, a survey by the American Podiatric Medical Association indicates that most women wear heels over 5 cm; thus, current prosthetic feet limit most female prosthesis users in their choice. Some prosthetic foot components are heel-height adjustable; however, their plantar surface shapes do not change to match the insole shapes of the shoes with different heel heights. The aims of the study were therefore (1) to develop a model that allows prediction of insole shape for various heel height shoes in combination with different shoe sizes and (2) to develop and field-test low-cost prototypes of prosthetic feet whose insole shapes were based on the new model. An equation was developed to calculate insole shapes independent of shoe size. Field testing of prototype prosthetic feet fabricated based on the equation was successful and demonstrated the utility of the equation.

Authors' Responsibilities – a Reminder about Authorship and Consent

Reporting of research in a scientific paper should be objective and transparent and thereby clearly convey to the readers the relevant information about the research study conducted. The most basic requirement is that results need to be reported in a clear, truthful and unambiguous manner. But the responsibility of authors goes beyond the reporting of correct results and the detailed description of the methodology used to reach such results: it includes, amongst other issues, the questions of authorship and critically, in research involving human participants, consent.