Devices for Bone Fixation

Abstract

Bone fixation devices made of bioabsorbable polymers have advantages over traditional metallic implants as the latter require a secondary operation to remove the device. However, bone fixation devices are expected to have much higher mechanical strengths than polymers used in soft tissue applications. Poly(l-lactide) (PLLA) is a semicrystalline bioabsorbable polymer that can be drawn to increase its mechanical strength. The present chapter describes the chemistry of PLLA and its applications in bone fixation devices. Degradation of PLLA takes a few years which may be adequate for bone regeneration. An important issue of bioabsorbable fixation devices is the balance between the bioabsorption rate and the mechanical strength maintenance. It is known that PLLA exhibits a piezoelectric effect that can accelerate new bone formation. Currently, PLLA bone fixation devices, including screws, pins, rods, and plates, are clinically available. They are used preferentially in non-load-bearing applications such as in maxillofacial surgery.