Effects of short anterior lumbar interbody fusion on biomechanics of neighboring unfused segments.

Study Design: Segmental mobility and intradiscal pressure were measured and the data compared in six cadaveric lumbar spine specimens before and after in vitro simulated single level L4-5 and double level L4-5-S1 anterior interbody fusions.

Objective: The experimental objective was to study the biomechanical effects of single level L4-5 and double level L4-5-S1 anterior interbody fusions on the neighboring unfused segments.

Summary Of Background Data: The relationship between the local rigidity created by fusion mass and accelerated degeneration reported at the neighboring unfused intervertebral discs is not clear.

Posture effect on seating interface biomechanics: comparison between two seating cushions.

Objective: This study aimed at investigating the effects of sitting posture on ischial pressure and pelvic orientation for two types of cushions.

Design: Two types of seating devices, Roho and Polyurethane (PU) Foam cushions, six predefined postures, and two subject groups, Normal and Paraplegic, were tested. Ischial pressure and pelvic orientation were monitored.

Evaluation of an active seating system for pressure relief.

In the first part of this study, the inflation-pressure and interface-pressure profiles of an active cushion system, the Talley active air bellows cushion, were examined continuously for one complete working cycle using the dynamic pressure monitor. The relationship between the inflation pressure and the interface pressure was explored. A well-defined relationship was found in the areas directly over the air bellows.

A biphasic poroelastic analysis of the flow dependent subcutaneous tissue pressure and compaction due to epidermal loadings: issues in pressure sore.

A layer of skin and subcutaneous tissue on a bony substratum was modeled as a homogeneous layer of biphasic poroelastic material with uniform thickness. The epidermal surface and the bony interface were taken to be impervious. The soft tissue on the bony interface was assumed either fully adhered or completely free to slide on the bone.

Biomechanical assessment of below-knee residual limb tissue.

In vivo indentation properties of the residual limb tissues of a group of senior subjects with below-knee (BK) amputation were measured and compared with those of nondisabled young adults. It was found that differences attributable to site variations, states of muscular activity, and the differences between the nondisabled young group and the group consisting of the seniors with amputation were all noted to be highly significant statistically. However, paired comparison between the residual limb and the sound contralateral limb of the senior group showed no significant difference.

Functional evaluation by gait analysis of various ankle-foot assemblies used by below-knee amputees.

Twelve different prosthetic feet were tested by 10 male subjects with right below-knee amputations. Level walking with each prosthetic foot was investigated using a pair of force plates. Five parameters were selected to compare the functional characteristics of the feet: 1) step length, 2) walking velocity on the sound side in relation to the prosthetic side, 3) depth of valley in the pattern of the vertical component of the floor reaction force, 4) efficiency of the deceleration and acceleration by the prosthetic foot, and 5) irregular patterns in the wave form of the fore and aft components of the floor reaction force.

Biomechanics and the wheelchair.

Wheelchair biomechanics involves the study of how a wheelchair user imparts power to the wheels to achieve mobility. Because a wheelchair can coast, power input need not be continuous, but each power strike can be followed by a period of recovery, with the stroking frequency depending on user preferences and the coasting characteristics of the wheelchair. The latter is described in terms of rolling resistance, wind resistance and the slope of the surface.

An alternative design of extension prosthesis.

Some patients with a congenitally shortened lower limb can be fitted with a total contact socket of one piece construction, dispensing with the need for removable panels or split socket construction. This gives advantages in weight, strength and cosmesis. The technique is described and compared with those conventionally used.