Experimental studies of DL-polylactic acid biodegradable plates and screws in rabbits: computed tomography and molecular weight loss.

A series of studies were designed to assess the potential of biodegradable DL-polylactic acid (DL-PLA) plates and screws for use in craniofacial surgery. We report on computed tomography (CT) scanning for visualization and postoperative follow-up and the short-term degradation sequelae of a biodegradable plate and screw system in an experimental animal model. Fractures of the nasal bones were created in 20 adult New Zealand white rabbits and rigidly fixed bilaterally with 4-hole plates and screws (n = 12), or left unrepaired for control data (n = 8). CT density, molecular weight, loss of plates and screws, and preliminary bone healing were assessed at 1, 2, 4, and 6 weeks postoperatively. Histologically, no differences in bone healing were noted between control and experimental animals at any time. Three-dimensional CT reconstruction of the skull was possible without artifacts, and no significant differences (p > 0.05) were found in specific CT scan density levels across postoperative intervals. However, significant (p < 0.001) molecular weight loss of the biodegradable plates was observed through 6 weeks postoperatively, reaching approximately 50% of the preoperative molecular weight. Molecular weight loss, however, was not detectable with CT density measurements. Results demonstrated that the use of biodegradable DL-PLA plates and screws had no adverse effect on fracture healing in this model and that CT scanning and three-dimensional reconstruction were possible without artifacts, independent of material degradation and molecular weight loss. These results suggest that this DL-PLA biodegradable system may have the potential for use in craniomandibulofacial surgery when short-term rigid fixation is necessary.