Susan Kapp

Suspension systems for prostheses.

The appropriate suspension system results in a safe and well functioning lower extremity prosthesis. Residual limb length, joint ligament stability, and limb volume determine suspension methods as does activity level, dexterity, success of previous suspension, and cosmetic requirements. The supracondylar suspension cuff, prosthetic sleeves, and gel liners with locking mechanisms generally are indicated for the average to long transtibial amputation level. Short limbs are better fitted with supracondylar and suprapatellar suspension. Waist belts generally are indicated for patients with new amputations or those with vascular compromise. Suction suspension is the most desirable form of transfemoral suspension and is recommended for most standard to long residual limbs. Roll on silicone liners with or without locking pins and the hyperbaric sock offer the patient systems that are easier to don yet still provide unencumbered suspension. The total elastic suspension belt offers excellent auxiliary suspension and can be applied to the prosthesis by the patient. Multiple factors and patient preference should be considered when prescribing suspension systems for lower extremity prostheses.

Effects of joint alignment and type on mechanical properties of thermoplastic articulated ankle-foot orthosis:

Background: Articulated or hinged ankle-foot orthosis (AFO) allow more range of motion. However, quantitative investigation on articulated AFO is still sparse. Objective: The objective of the study was to quantitatively investigate effects of alignment and joint types on mechanical properties of the thermoplastic articulated AFO. Study design: Tamarack dorsiflexion assist flexure joints with three durometers (75, 85 and 95) and free motion joint were tested. The AFO joint was aligned with the center of the motor shaft (surrogate ankle joint), 10 mm superior, inferior, anterior and posterior with respect to the motor shaft center. Methods: The AFO was passively moved from 20° plantar flexion to 15° dorsiflexion at a speed of 10°/s using a motorized device. Mechanical properties including index of hysteresis, passive resistance torque and quasi-static stiffness (at neutral, 5°, 10° and 15° in plantar flexion) were quantified. Results: Significant effects of joint types and joint alignment on the mechanical properties of an articulated thermoplastic AFO were revealed. Specifically, center alignment showed minimum resistance and stiffness while anterior and posterior alignment showed significantly higher resistance and stiffness. The dorsiflexion assist torques at neutral position ranged from 0.69 ± 0.09 to 1.88 ± 0.10 Nm. Conclusions: Anterior and posterior alignment should be avoided as much as possible. Clinical relevance The current study suggested that anterior and posterior alignment be avoided as much as possible in clinical practice due to potential skin irritation and increase in stress around the ankle joint.

Contemporary Students: Learning Styles and Teaching Strategies

Adult learners and career change students are increasingly common in prosthetic and orthotic education. This may be attributed to the relative obscurity of the profession within the allied health arena. Potential students are often introduced to the field through personal experience. The student may know someone in need of services, have obtained services themselves, have had professional or personal contact with a prosthetist-orthotist, or have had other casual circumstances with someone involved in prosthetics or orthotics. (J Prosthet Orthot. 2002;14:71–74.) KEY INDEXING TERMS: Adult learner, prosthetic and orthotic education, web based resources, learning styles, teaching

Development of a Motorized Device for Quantitative Investigation of Articulated AFO Misalignment

The objective of the study is to develop a motorized device to quantitatively investigate the AFO alignment and mechanical properties. The motorized device consists of a servo motor and an inline gear box with a 25:1 gear ratio. A thermoplastic articulated AFO with TamarackTM dorsiflexion assist flexure joint was investigated in the study. The motor shaft was used to mimic the anatomical ankle joint. The joint of the AFO was aligned in such a way that the offset could be systematically manipulated (aligned exactly with the center of motor shaft, 10mm superior, inferior, anterior or posterior with respect to the center of motor shaft). The AFO was passively moved in the range from 30 degrees plantar flexion to 20 degrees dorsiflexion at a prescribed speed of 3 deg/s. 11 complete cycles were run lasting about 400 s. Index of hysteresis was calculated as the ratio of area within the loop to the area below the ascending limb and presented in percentage (%). In addition, passive resistance torque and quasi-static stiffness were quantified at prescribed positions. Based on the preliminary results the perfect alignment will result in the lowest resistance torque, quasi-static stiffness and moderate hysteresis index. However, the alignment of 10 mm inferior showed the largest hysteresis index indicating an excessive energy loss during unloading phase and higher resistance torques during the loading phase. It suggested that alignment excessively below the anatomical joint should be avoided in clinical practice. The alignment of 10 mm superior showed comparable quantities to the perfect alignment and could be recommended in practice if perfect alignment is hard or not possible to implement. In summary, we have demonstrated that the device could be a powerful quantitative tool for practitioners and researchers. It is expected that the information obtained will be valuable to clinicians and provide recommendation on decision-making. In addition, the quantitative results will be useful in simulation and modeling studies.

An experimental apparatus to simulate body-powered prosthetic usage: Development and preliminary evaluation.

Background and aim: Harness fitting in the body-powered prosthesis remains more art than science due to a lack of consistent and quantitative evaluation. The aim of this study was to develop a mechanical, human-body-shaped apparatus to simulate body-powered upper limb prosthetic usage and evaluate its capability of quantitative examination of harness configuration. Technique: The apparatus was built upon a torso of a wooden mannequin and integrated major mechanical joints to simulate terminal device operation. Sensors were used to register cable tension, cable excursion, and grip force simultaneously. Discussion: The apparatus allowed the scapula to move up to 127 mm laterally and the load cell can measure the cable tension up to 445 N. Our preliminary evaluation highlighted the needs and importance of investigating harness configurations in a systematic and controllable manner. Clinical relevance: The apparatus allows objective, systematic, and quantitative evaluation of effects of realistic harness configurations and will provide insightful and working knowledge on harness fitting in upper limb amputees using body-powered prosthesis.