A COMPUTERISED MODEL TO STUDY BONE STRESSES IN A SCARF OSTEOTOMY

Abstract

Scarf osteotomy is widely used as a surgical treatment for hallux valgus. It is a versatile osteotomy, allowing shortening, depression or medial displacement of the capital fragment but it remains uncertain how stresses within the bone subsequently vary. The aim of this study was to design a computerised model to explore the effect on bone stress of changing the position of bony cuts for a scarf osteotomy.

A computerised image was constructed using finite element analysis. This utilises a mathematical technique to form element equations which represent the effect of applied force to the object appropriate to each finite element. Maximum bone stresses were then measured using different osteotomy variables. The osteotomy variables studied were the length of the longditudinal cut, apex of the distal cut to articular cartilage, resection level of the longditudinal cut and combinations of these variables. A saw bone model was used to test the findings of the study.

The results of this study show that lowering the longditudinal resection level and shortening via the distal cut beyond 6 mm will decrease bone stress. Additionally, raising the longditudinal resection level and shortening via the proximal cut caused an increase in bone stress. A saw bone model confirmed the findings of the study.

In conclusion, our experience is that finite element analysis is a very useful model in studying the bony stresses for a scarf osteotomy and assists in optimising the direction and angle of bony cuts used.