Biomedical subjects

J Gurtowski

Publications and source records attributed to J Gurtowski.

5 recordsLinked to original sources

PubMed1989

Cortical pelvic strains with varying size hemiarthroplasty in vitro.

Four human pelves were dissected of soft tissues and instrumented with rosette strain gages. The pelves were left intact (not separated at the pubic symphysis or sacroiliac joints) although each of the eight hemipelves was tested separately. The pelves were loaded to simulate single leg stance with use of a wire mesh cemented to the wing of the ilium, representing the abductor muscles. Loading was carried out with the intact hip joint and 1 mm undersized, correct sized, and 1 mm oversized hemiarthroplasty. The correct sized component produced a strain pattern closet to normal. The oversized component was associated with an increase in strain at the medial acetabular dome.

Acetabulum↗

PubMed1989

Normal pelvic strain pattern in vitro.

Four cadaver pelves were dissected of soft tissue and each of the eight hemipelves instrumented with ten rosette strain gauges. Static loading was conducted to simulate single leg stance, and applied through the intact hip joint. The medial portion of the pelvis was under tension directed vertically and the lateral ilium was in compression. This strain pattern is consistent with bending applied to the ilium from the action of the abductor and joint reaction forces.

Biomechanical Phenomena↗

PubMed1985

The vertical wheeler: a device for ambulation in cerebral palsy.

The vertical wheeler is a new mobility aid that was specifically designed to help improve the quality of life for the handicapped child by providing mobility while standing. Results of a clinical trial in a population of patients with cerebral palsy are presented. Criteria were selected to allow evaluation of the rehabilitative effect of the device on the population. Results showed that the children in this cerebral palsy group all benefited from ambulation with the wheeler. Patients with spastic quadriparesis seemed to gain the most immediate benefit. The device contributed to improved mobility, posture, and self-image. The wheeler was safe and fun for the children. It has the potential for improving the psychologic and medical status of the child with severe locomotion impairment.

Cerebral Palsy↗

PubMed1983

Performance characteristics of total hip femoral components as a function of prosthesis modulus.

A study of total hip femoral components was performed to demonstrate the effects of changes in prosthesis modulus upon strain levels and subsidence data measured in vitro. Femoral components of identical geometry but fabricated from dissimilar alloys were implanted sequentially in the same femoral specimens so that their relative performance could be compared. It was found that the components fabricated from titanium alloy produced higher levels of calcar strain than the cobalt-chromium components when collar/calcar contact was preserved. However, when collar/calcar contact was removed, cobalt-chromium stems showed a greater propensity for subsidence into the medullary cavity. The increased rate of subsidence of the stiffer stems produced concomitantly greater circumferential strain levels in the proximal cortical shell. It is concluded that the increased tensile hoop strain caused by subsidence of the cobalt-chromium stems will be particularly deleterious to the integrity of the cement mantle.

Biomechanical Phenomena↗

PubMedDate not supplied

The load carrying and fatigue properties of the stem-cement interface with smooth and porous coated femoral components.

Porous coated surfaces for fixation of total hip replacement are a current trend in clinical orthopedics. Such devices are designed to be fixed by ingrowth of bony tissue, although in the absence of FDA approval for biologic fixation, fixation with PMMA cement is recommended by the implant manufacturers. In order to characterize the mechanical properties of the micro-interlocked stem-cement interface, we tested both porous coated and smooth femoral components in cement mantles of consistent overall geometry. Under conditions of increasing load the smooth stems demonstrated stepwise irreversible subsidence into the mantle. Axial and circumferential strains measured in the cement containment vessels with the smooth stems showed that stepwise increases in tensile hoop strain occurred concomitantly with the stepwise incidents of stem subsidence. When subjected to the same loading conditions, the porous coated stems did not undergo stepwise incidents of subsidence, and hoop strain generation was reduced. In addition, a twofold increase in the failure load of the stem-cement interface was measured with the porous coated stems. Fatigue loading for 10(7) loading cycles did not result in gross failure of either the micro-interlocked or smooth interfaces. However, the data showed that during fatigue loading, stepwise subsidence of the smooth stems again occurred. The final subsidence magnitude of the smooth stem-cement interface at 10(7) loading cycles was six times greater than the value associated with the porous coated stem. Thus the porous coating of femoral stems was shown to dramatically improve the load carrying capability and fatigue characteristics of the stem-cement interface.

Biomechanical Phenomena↗