Summary
An absorbable, biocompatible 4.5 mm screw, with a matrix of polyright-left-isomeric lactic acid of equal amounts of isomers and fibres of poly-left-isomeric lactic acid comprising a self-reinforced structure, was tested for fixation of a trochanteric osteotomy on six laboratory Beagles. The proximal femurs were harvested two months later and embedded in methylmethacrylate for histological, microradiographic, and fluorescence evaluation. Five specimens showed bony union and one trochanter was ununited. The coarse thread configuration and poor torque strength of the screw required exaggerated tapping of the screw hole resulting in a loose fit for the implant. An improved screw could be clinically appealing and a secondary removal operation would then be omitted.
To test a totally absorbable polylactic acid screw with good initial in vitro strength values a trochanteric osteotomy was fixed with this implant in six laboratory Beagles. Radiographic, microradiographic, fluorescence and histological evaluations indicated healing in five dogs at two months. Nonunion in one dog was attributed to diastasis between the fragments. The strength and strength retention of the screw were considered adequate, but the poor torsional strength made implantation of the screw tedious.
Key words
Absorbable screw - Polylactic acid - Trochanteric osteotomy
