Shape sensing as an educational aid for student prosthetists.

An automatic method of measuring the shape of plaster replicas of residual limbs has been developed. This instrument enables the full three-dimensional shape to be digitized and stored on computer. The shape modifications produced by student prosthetists are examined by requesting the computer to draw sections of the unmodified replica with corresponding sections following modification superimposed. This paper reports experiences with the use of this instrument as a teaching aid for student prosthetists.

An experimental evaluation of spinal flexibility with respect to scoliosis surgery.

Lateral flexibility of the spinal column was investigated by mechanical analysis and by experiments on fresh cadavers. The work was undertaken with the aim of improving the surgical treatment of scoliosis by quantifying the effects of ribs and transverse processes on lateral spinal flexibility. To this end, flexibilities before and after removal of the bony elements in cadavers' spines were compared. A portable instrument was built to apply loads to the spines. Generally, the spines were tested in the following sequence of conditions: intact, resected ribs on one side, resected ribs and transverse processes on the same side. The results from nine cadavers indicate that only rib resection on the tension side of the induced curve (scoliotic concavity) significantly increased spinal flexibility. It is concluded that the surgical correction of scoliotic curves with instrumentation and fusion is maximized with rib osteotomy or resection.

Forces in the metacarpophalangeal joint due to elevated fluid pressure--analysis, measurements and relevance to ulnar drift.

The mechanics of the metacarpophalangeal joint are analyzed, with a view to understanding why the finger moves in the direction of ulnar drift when the intra-articular pressure in the joint is increased. The first step is the in situ measurement of stiffness of the various tissues surrounding the joint, and the data show that (a) the two collateral ligaments are the major component and (b) the ulnar ligament is the stiffer. This latter result, combined with finding the centre of pressure at the base of the phalanx, reveals how increased intra-articular pressure produces ulnar deviation. Flexion, the other component of ulnar drift, is produced because of the volar side attachment of the ligaments. The mechanics are evaluated quantitatively by the measurement of forces at the finger tip for various pressures; the data agree reasonably well with predictions using the measured joint properties in a simplified mechanical model of the joint.