Biomedical subjects

D G Chess

Publications and source records attributed to D G Chess.

5 recordsLinked to original sources

PubMed1995

Some basic biomechanical characteristics of medullary pressure generation during reaming of the femur.

We measured femoral intramedullary pressures and applied axial thrust force generated in vitro during reaming with the AO and Zimmer systems. Six pairs of cadaver femora were instrumented with pressure taps midshaft and in the distal diaphysis, a load cell distally to measure force, and a displacement transducer to monitor reamer position. Following initial hand reaming, intramedullary power reaming was conducted utilizing a 9-mm reamer initially, with subsequent increases in steps of 0.5 mm. All femora were maintained at 37 degrees C and albumin was used to maintain a fluid-filled canal. The highest pressures consistently occurred during initial power reaming, with peak pressures ranging from 270 to 1500 mmHg amongst femora with the AO system. No significant differences were found in the peak pressures generated for the two systems (P = 0.10). The pressure measurements at the two locations in the femur were consistently similar, indicating that pressures are continuous throughout this aspect of the femur. The pressures were not correlated with instantaneous applied axial thrust (R2 = 0.191), and this could be attributed chiefly to the additional friction force of cutting. While pressure generation in the medullary canal upon reaming is likely governed by the rate of clearance of canal content, this is a highly variable response produced by characteristics of the femur which are still not fully understood.

Aged↗

PubMed1994

Compression forces generated by the Huene alignment guide alone.

To enhance the fixation of scaphoid fractures by providing precise alignment and compression at the fracture site, the Huene alignment guide has been used in conjunction with bone screws. In an effort to predict the compressive force generated by the Huene guide alone, these forces were measured with a calibrated, strain-gauge, instrumented device. Three orthopedic surgeons each tested the guide 10 times on one cadaver scaphoid bone specimen. The magnitude of the compressive forces generated ranged from 9.0 to 67.0 N (mean 36.0 +/- 15.0 N). Comparisons of the force measurements among the individuals revealed no significant differences. This wide range of measurements could be attributed to the variability of the ratchet mechanism on the device. Because the Huene alignment guide is used to generate transcaphoid compressive forces, these results demonstrate that it does not yield consistent compression.

Bone Screws↗

PubMed1991

An evaluation of three loading configurations for the in vitro testing of femoral strains in total hip arthroplasty.

Despite recent advances in total hip arthroplasty, proximal femoral resorption and osteopenia remain problems. To analyze the proximal strain effects of three different loading conditions, strains produced in intact and postarthroplasty femora have been compared. Ten adult cadaveric femora of similar size, shape, and rigidity were tested. Ten strain-gauge rosettes were positioned on each femur. To simulate the "single leg support" phase of gait, fixtures were developed to load the femora under three different configuration: the VS (vertical shaft) configuration, with a vertically orientated femur having rotational freedom proximally and distally; the ITB (iliotibial band) configuration of a femur with rotational freedom positioned 11 degrees from the vertical, with a strain-gauge adjustable metallic simulation of the lateral muscles of the thigh; and the ABD (abductor) configuration of a femur with rotational freedom positioned 11 degrees from the vertical, with a strain-gauge adjustable metallic simulation of the abductor muscles. Each femur was loaded less than or equal to 600 N through the medial point, located at one sixth of the transcondylar distance. Strain patterns and magnitudes produced by the three loading configurations were quite different in both the intact and postarthroplasty femora. Both the ITB and the ABD configurations resulted in greater proximal medial compression and lateral tension than did the VS configuration. The magnitudes of the proximal strains were significantly greater in the ABD configuration (p less than 0.05). Postarthroplasty femora showed similar proximal results. It is proposed that meaningful strain data for the physiologically loaded femur can be obtained only with simulations that include the forces produced by the iliotibial band. To overcome the indeterminate nature and biological variation in these forces, the studies have to consider a range of forces.

Femur↗

PubMedDate not supplied

Cubitus varus: significant factors.

For better understanding of the etiology of "post-supracondylar fracture cubitus varus," an in vitro anatomic experiment was performed. Elbow models were precisely photographed in 256 combinations of 10 degrees increments of varus angulation, posterior angulation, internal rotation, and/or flexion contracture. Varus angulation was the most important single factor contributing to deformity. Addition of flexion contracture or posterior angulation to a given varus angulation decreased apparent deformity, whereas addition of internal rotation worsened the deformity. Control of varus angulation in the clinical setting, by whatever method, should minimize post-supracondylar fracture cubitus varus.

Fractures, Bone↗

PubMedDate not supplied

Short arm plaster cast for distal pediatric forearm fractures.

Ten years' clinical experience with below-elbow plaster cast treatment of distal one third pediatric forearm fractures was subjected to an independent retrospective radiographic review. In the study population of 761 fractures, no significant displacement occurred while the forearm remained in plaster. The average angulation change was 4.5 degrees (SD +/- 2.2 degrees). In each angulation change > 5 degrees, poor cast molding was evident, as reflected by a high "cast index" (p < 0.01). Although this technique is technically demanding, excellent results are obtained in all distal pediatric forearm fractures if proper cast molding is used.

Casts, Surgical↗