Resting TcPO2 levels decrease during liner wear in persons with a transtibial amputation.

BACKGROUND: In our clinic, a substantial number of patients present with transtibial residual limb pain of no specific somatic origin. Silicone liner induced tissue compression may reduce blood flow, possibly causing residual limb pain. Thus, as a first step we investigated if the liner itself has an effect on transcutaneous oxygen pressure (TcPO2). METHODS: Persons with unilateral transtibial amputation and residual limb pain of unknown origin were included. Medical history, including residual limb pain, was recorded, and the SF-36 administered. Resting TcPO2 levels were measured in the supine position and without a liner at 0, 10, 20 and 30 minutes using two sensors: one placed in the Transverse plane over the tip of the Tibia End (= TTE), the other placed in the Sagittal plane, distally over the Peroneal Compartment (= SPC). Measurements were repeated with specially prepared liners avoiding additional pressure due to sensor placement. Statistical analyses were performed using SPSS. RESULTS: Twenty persons (9 women, 11 men) with a mean age of 68.65 years (range 47-86 years) participated. The transtibial amputation occurred on average 43 months prior to study entry (range 3-119 months). With liner wear, both sensors measured TcPO2 levels that were significantly lower than those measured without a liner (TTE: p < 0.001; SPC: p = 0.002) after 10, 20 and 30 minutes. No significant differences were found between TcPO2 levels over time between the sensors. There were no significant associations between TcPO2 levels and pain, smoking status, age, duration of daily liner use, mobility level, and revision history. CONCLUSION: Resting TcPO2 levels decreased significantly while wearing a liner alone, without a prosthetic socket. Further studies are required to investigate the effect of liner wear on exercise TcPO2 levels.

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.

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.

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.

Net external energy of the biologic and prosthetic ankle during gait initiation.

The net external energy of the biologic human ankle joint and of some lower limb prosthetic ankle-foot systems was examined during gait initiation. The purpose of the study was to better understand the ankle's behavior during the acceleration phase of walking for use in the design of improved lower limb prostheses and orthoses. Quantitative gait data were collected from 10 able-bodied subjects and 10 persons with unilateral transtibial amputations during gait initiation. The behaviors of the biologic and prosthetic 'ankle' joints were examined by analyzing the relationship between sagittal plane ankle angles and moments. Net external energy at the ankle was estimated by calculating the area under the moment versus angle curves (hysteresis) created during the loading and unloading phases. Results indicate that able-bodied persons utilize energy input from the trailing ankle after the first step is made in gait initiation, most likely to help transition the body into steady-state walking. The passive prosthetic ankle-foot systems tested were unable to put energy into the system during gait initiation.

Roll-over shapes of the able-bodied knee-ankle-foot system during gait initiation, steady-state walking, and gait termination.

A few investigators have described the movement of the center of pressure (COP) of the ground reaction force and the activation patterns of the lower limb muscles during gait initiation and termination. This study examines the effective rocker (roll-over shape) behavior of the knee-ankle-foot (KAF) system during gait initiation, steady-state walking (i.e. constant speed gait), and gait termination. The KAF roll-over shapes were characterized by transforming COP data of 10 able-bodied subjects from a laboratory-based coordinate system into a leg-based coordinate system. The resulting roll-over shapes (effective rockers) were characterized using a circular arc model. The KAF roll-over shapes exhibit an overall "flexed" orientation during the first step of gait initiation and an "extended" orientation during the last step of gait termination. Understanding the behavior of the anatomical KAF system during gait initiation and termination may aid in the design of prosthetic components, i.e. mechanical devices that replace complete anatomical structures. Prostheses that intend to mimic the overall behavior of physiological KAF systems (biomimetic designs) could be manufactured using approaches that are much simpler than attempting to reconstruct the complexity of the lower limb.

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.

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.

The 'shape&roll' prosthetic foot: I. Design and development of appropriate technology for low-income countries.

The Shape&Roll Prosthetic Foot (patent pending) is an artificial foot designed for use in low-income countries, and may also be useful in industrialised nations. Its design is based on the theory that the roll-over shape of a prosthetic foot should mimic that of the non-disabled physiological foot-ankle complex during walking. This article presents the S&R foot including the unique features incorporated into its design. The results of mechanical tests indicate that the roll-over shape of the foot closely mimics the roll-over shape of the non-disabled ankle-foot complex and an expensive 'high-performance' prosthetic foot. The fatigue testing process for the S&R foot is also described. The foot has been shown to be durable according to the International Organization for Standardization (ISO) standards, with more than five samples tested to date. The Shape&Roll Foot is low in cost, simple to fabricate, light in weight, low in profile, and is highly functional for walking in respect of roll-over characteristics.

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.

A simple method for determination of gait events.

Simple and effective methods for determining the timing of gait events are necessary for the proper normalization and statistical analysis of gait data when a variety of gait measurements are available. The approach presented was developed for cases in which overall center of pressure under the body and marker trajectories are being measured over multiple steps. The new method presented uses the relative positioning of the overall center of pressure and an ankle marker in the direction of forward progression for the determination of "heel-contact" and "toe-off" events. The difference between the locations of the overall center of pressure and the ankle in the direction of progression readily delineates the timing of these events. The new method was tested against force records from individual force platforms and was found to detect "heel-contact" events an average of 1 sample (at a sampling frequency of 120Hz, 0.00833s) before the event found using the individual force platforms. "Toe-off" events were found an average of 2 samples (0.0167s) prior to the events found using individual force plates. The method appears new and is attractive because of its simplicity in determining gait events when the appropriate gait measurements are available.