A force-line visualization system

An evaluation of patient perceptions to the value of the gait laboratory as part of the rehabilitation of primary lower limb amputees

The value of gait analysis for research and product development/evaluation in prosthetics is well understood. However, in the rehabilitation of amputees, the application of gait analysis beyond observation in the clinical setting is not routinely practiced, largely due to the cost and time taken to complete a fully instrumented data collection and analysis. To address the time issue, a weekly clinical gait service for primary amputees, based around a reduced data set from video and video vector technology, has been developed. In this clinic primary amputees are seen twice in the Gait Laboratory during their rehabilitation period, with the clinic time for each patient being no more than 15 minutes, which covers both data collection and review. A questionnaire was developed to evaluate the patients' perceptions of the clinic. The questionnaire was completed anonymously by 48 primary amputees over a 6-month period. The results from the questionnaire demonstrate that the clinic was perceived positively by the patients, and suggested areas of future development, e.g. the education of junior staff, and the need to include the patient's physiotherapist in the data collection and review process.

A new biomechanical method for determination of static prosthetic alignment

A new static alignment method for trans-tibial prostheses is suggested using the individual load line as a reference. Standing posture and static alignment of 18 experienced trans-tibial prosthetic users with good walking ability were determined and compared with 20 healthy persons. The individual load line was defined by means of the new Otto Bock alignment system "L.A.S.A.R. Posture". The sagittal standing posture of trans-tibial amputees and non-amputees differs. Normally only a prosthesis worn by the trans-tibial amputee and dynamically aligned over an extended period of time satisfies biomechanical rules of alignment. In contrast, prostheses aligned during one session in the traditional subjective manner seem to lack any recognizable biomechanical systematics. Initial results suggest the knee centre should be 10 to 30mm behind the load line, depending on patient's weight. This knee position is independent on the type of prosthetic foot.

Influence of prosthesis alignment on the standing balance of below-knee amputees

The effect of alignment of the prosthesis on the standing balance of below knee amputees was investigated in this work. Alignment variations consisted of varus and valgus tilt and plantar- and dorsiflexions. The foot-ground reaction forces measured in the anteroposterior, mediolateral, and vertical directions as well as global parameters describing the total sway activity, asymmetry, and weight-bearing imbalance were used to compare the various alignment positions studied. The results indicate the presence of a common standing pattern in below-knee amputees, where activity of the foot-ground reaction forces in the anteroposterior direction is significantly higher in the contralateral limb compared with the amputated limb. It was also found that the varus and valgus alignments were the least stable of all alignments.

Partial immobilization of the ankle and talar joints complex and its effect on the ground--foot force characteristics

A combined qualitative–quantitative approach towards the analysis of the ground reaction forces is suggested so as to detect deficiencies and predict hazards in human locomotion. The population studied is a group of patients who have undergone partial or full arthrodesis of the ankle–subtalar joint complex. The various ways in which the effects of ankle fusion are reflected on the force characteristics are discussed. The non-uniformity of reflection suggests an elaborate compensatory mechanism which is also being considered. As a conclusion it is suggested that surgical corrections such as immobilization of joints may be hazardous to the skeletal elements unless adequate compensatory walking habits are developed. The reduced flexibility of the system has to be compensated either by involving other joints, such as the knee, in the force attenuation process or by provision of flexible footware.

Simulation of human gait with the aid of a simple mechanical model

A simple mechanical model was used in this study to simulate the stance phase of human locomotion. The model consists of a concentrated mass supported by two elastic and viscous straight legs. The model is provided with a set of initial conditions at the instant of "heel strike" and then continues to move due to its inertia and the action of gravity. The simulation results were compared with the corresponding experimental data and have shown agreeable similarity. The model was also used to study the effect of some body features on the resulting walking pattern and to explain the generation of the ground reaction force characteristics.