Introduction and Aims: To determine differences in metal memory, at physiological temperatures, between 6mm stainless steel and titanium rods as a function of construct failure in scoliosis surgery.

Method: Different length Ti and SST rods were contoured at room temperature with a radius of curvature of 30cm and incubated at 37±2°C. Rods were photographed biweekly over graph paper with a digital camera. The images were processed using Jandel Sigma Scan. A best-fit regression polynomial was used to calculate the average curvature. After 36 weeks, the curvature of each rod was normalised against the initial curvature and plotted against time, with a linear regression performed to assess changes in curvature, expressed as percent of change per year.

Results: Changes in both SST rods and pre-bent Ti rod were within measurement error (0.52% increase for long SST, 0.26% decrease for short SST). In contrast, both manually bent Ti rods changed markedly (decreases of 6.76% and 5.2% for long and short Ti rods respectively).

Conclusion: Continuous physiologic heat conduction may contribute to a loss of curvature in Ti rods due to memory properties. The ideal implant should retain the intended contour. Ti rods, subjected to physiologic heat, lost correction. The use of custom contoured Ti rods for the surgical correction of spinal deformities should be questioned.

Three palmar wrist ligaments from fresh human cadavers were dissected from the proximal to the distal insertions and stained to identify the mechanoreceptors. Golgi organs, Pacinian corpuscles, Ruffini endings and free nerve endings were present in all three ligaments. In the radial collateral and radiolunate ligaments they were found in increased density towards the proximal and distal insertions. A more uniform distribution was found in the radioscaphocapitate ligament which has attachments to three bones.

The palmar wrist ligaments may have a significant sensory role in maintaining the stability of the wrist and in controlling its movement. Although technically difficult, the surgical repair of traumatic wrist defects should attempt to preserve the innervation of the ligaments, shown to be mainly near bony attachments. This may allow improvement in postoperative outcomes by preserving some proprioception. In some painful post-traumatic or degenerative conditions, however, denervation may be advantageous.