The behaviour of the periosteum during callotasis

Periosteal behaviour during callotasis has been studied in animals but not in humans. Markers were inserted into the periosteum of seven patients who underwent callotasis. All of them had tibial callotasis, five patients had bone transport procedure and two had leg lengthening due to congenital disorder. They were followed up radiologically at regular intervals and during the distraction the movement of the periosteal markers was recorded. This enabled observation of the way the periosteum elongates during the procedure and also the calculation of periosteal strain at different stages at the points where the periosteum is fixed to bone. The study indicated that in most cases the periosteum acts as an elastic sleeve surrounding the newly formed tissue during lengthening. The site of attachment between sleeve and cortex became established early during lengthening, and hardly changed position at later stages. There was a wide spread of attachment sites and periosteal strains. Attachment sites were not related to pin or wire entry points, and strains were not predictive of callus shape or healing time.