Clinical biocompatibility and degradation of polylevolactide screws in the ankle

The clinical biocompatibility and degradation behavior of absorbable fracture fixation devices are still incompletely known in humans. Fifty-one patients with displaced fracture of the ankle treated by open reduction and internal fixation with absorbable screws made of polylevolactide were seen in followup for at least 3 years. The mean duration of followup time was 52 months. The tissue tolerance and degradation of the devices were studied clinically and radiographically using computed tomographic scans. In addition, biopsy specimens for histologic examination were taken in 5 patients. The screws were clinically effective: An accurate position of the fragments was maintained until union in 50 patients. A mild transient subcutaneous late foreign body reaction occurred in 1 patient 22 months after fixation of the fracture. Despite radiographic evidence of an advancing degradation of the implants, biopsy specimens taken 45 months after the original operation still showed consistent areas of polylactide in the tissues. In 3 patients, a disturbing palpable subcutaneous screw head had to be removed. The incidence of foreign body reactions to polylevolactide screws in the ankle seems to be low, but the duration of the degradation process of the polymer in human tissues is considerably longer than has been anticipated.