Biomedical subjects

J R Davey

Publications and source records attributed to J R Davey.

22 records · Page 2Linked to original sources

PubMed1987

Stability of ten configurations of the Hoffmann external-fixation frame.

The rigidity, load to yield, and load to failure of ten configurations of the Hoffmann external fixator were investigated using a model of wooden pylons with a simulated fracture that consisted of either a reduced transverse cut or a ten-millimeter gap. The axial compressive, torsional, anterior-posterior bending, and medial-lateral bending characteristics of four forms of the single half-frame (half-pinned), four double half-frame, and two full-frame (transfixion-pinned) configurations were examined. Of the single half-frame configurations, a system with a second stacked connecting-rod proved to be superior; however, the system yielded at a mean axial compressive load of only 199 newtons and failed totally at 355 newtons. The delta frame (two rods connecting or triangulating two half-frames set at an angle of 45 degrees to one another) was as rigid as the quadrilateral full frame in axial compression; however, it exhibited low loads to yield and to failure, with means around 200 and 350 newtons, respectively. The use of only two pins in each pin-cluster did not significantly affect the performance of the delta frame. The two full-frame systems performed poorly in torsion and particularly poorly in anterior-posterior bending. The loads that caused a one-millimeter movement within the fracture gap in axial compression were notably low: for the stacked half-frames the load did not exceed a mean value of 174 newtons; for the double half-frame, 190 newtons; and for the quadrilateral frame, 412 newtons. We concluded that no frame had a good over-all performance with regard to rigidity.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗

PubMed1987

A biomechanical study of wire fixation.

A biomechanical study of wire fixation was performed using 18-gauge stainless steel wire on an Instron universal testing machine. Six groups of wires were tested--an intact piece of wire (control), a wire bent to a right angle five times, a simple knot, a square knot, a loop knot and a twist knot. The tensile load-to-failure value for each wire was recorded. The intact wire broke at a mean load of 67 kg. The wires with the bend, the simple knot and the square knot all broke at similar loads. Those wires with a knot broke at the knot. The loop and the twist knots pulled apart at much lower loads. These results indicate that bending the wire does not weaken it substantially, but kinking may initiate the site of breakage. The square knot is the strongest knot; the loop and twist knots are not recommended if the wire is to be under tension.

Animals↗

PubMed1985

A technique of posterior cervical fusion for instability of the cervical spine.

A technique of posterior cervical spine fusion (the "Dewar procedure") that allows immediate stabilization of the spine requiring only minimal external support is described. The procedure was performed in 16 patients with unstable fractures or fracture-dislocations of the cervical spine. All patients went on to develop solid fusion. Twelve patients incurred neurologic deficit due to their injury, and those with root involvement all recovered following fusion. Patients rendered quadriplegic as a result of their accident did not show any useful neurologic recovery but were able to start rehabilitation earlier and avoid the complications of nonoperative treatment. There were no significant complications related to surgery.

Adolescent↗

PubMedDate not supplied

The tibialis posterior muscle compartment. An unrecognized cause of exertional compartment syndrome.

Exertional compartment syndrome in the deep posterior compartment of the leg is well recognized. This paper reports investigations which were performed to prove that the tibialis posterior muscle is contained in its own osseofascial compartment, separate from the rest of the deep posterior compartment. Radiographs following the injection of radio-opaque dye into the tibialis posterior muscle demonstrated the fluid-impermeable, osseofascial boundaries surrounding this muscle. Compartment syndromes created in cadaver legs reveal that traditional techniques of fasciotomy of the deep posterior compartment are inadequate in decompressing the tibialis posterior muscle. Intracompartmental pressure measurements in athletes with a clinical diagnosis of exertional compartment syndrome proved the existence of isolated exertional compartment syndrome in the tibialis posterior muscle. From these results we may conclude that the tibialis posterior muscle is contained in a separate osseofascial muscle compartment which may be the site of an isolated exertional compartment syndrome and that common techniques of fasciotomy of the deep posterior compartment do not decompress the tibialis posterior muscle.

Adult↗