Abstract
Shape memory phenomenon whereby the metal changes its characteristics depending on the ambient temperature it is exposed to is well described in the metallurgical literature. In cold conditions (0–5° C) the alloy becomes plastically deformable and its shape can be changed at will, but would rapidly regain its original shape and strength at higher temperatures. This study assesses the effectiveness of shape memory staples as a method of internal fixation in foot and ankle surgery.
All patients who underwent foot and ankle surgery in which Memory® staples were used for fixation were included in the study. The patients were evaluated with regard to period of immobilisation in cast, period of restricted weight bearing and time to radiological joint fusion or union of osteotomy.
Memory® staples had been used in a total of 40 procedures; 13 procedures (6 MTPJ fusions, 7 Akin osteotomies) were done in the forefoot while the rest were carried out in the mid or hind foot. Bone grafting was used only in one hind foot arthrodesis. A strong arthrodesis or union was achieved in all the patients. The average time to fusion was 7.2 weeks (range 6–12) with an average period of immobilisation of 4.3 weeks (range 0–12). The average time to full weight bearing was 5.2 weeks (range 0–6). Breakage of the staple was noticed in one patient but the joint went on to unite satisfactorily. Staple back out or displacement was not noticed in any of the cases.
The early experience with the use Memory® staples in foot and ankle surgery is encouraging; we did not encounter any technical problems and there is a suggestion that these implants may reduce the time to fusion/ healing thereby reducing the recovery time following foot and ankle surgery.
Correspondence should be addressed to the Honorary Secretary, BOFSS, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
