Biodegradable semirigid plate and miniscrew fixation compared with rigid titanium fixation in experimental calvarial osteotomy

Object. To determine the biocompatibility and suitability of resorbable pla tes and miniscrews, consolidation of symmetrical, bilateral frontal bone cr aniotomies that had been closed using various methods was studied in 20 gro wing lambs. Methods. Bone fixation with a flexible, punched polylactide plate and four slowly degradable, self-reinforced polylevolactide (SR-PLLA) or rapidly deg radable, self-reinforced polyglycolide (SR-PGA) miniscrews (10 animals in e ach group) was compared intraindividually with rigid fixation by using a ti tanium miniplate and four miniscrews. Plain x-ray films, magnetic resonance images, histological studies, and histomorphometric studies were obtained at 4 to 104 weeks. Conclusions. No dislocation. instability, clinical foreign body reactions, infections, or loss of fixation were observed. Bone consolidation of the 2. 35-mm-wide craniotomy lines was incomplete; connective tissue-filled defect s through the bone were observed in 13 of 28 lines at 26 to 52 weeks. Stati stical analyses based on histomorphometric studies showed no difference in consolidation with SR-PLLA miniscrew and titanium plate/screw fixation or b etween the two resorbable fixation methods. Fixation with rapidly degradabl e SR-PGA miniscrews resulted in less effective consolidation than on the co ntralateral titanium-treated side (p < 0.05), but the bone segment was thic ker (p < 0.005). The SR-PGA miniscrews had disappeared by 6 weeks, the poly actide plate by 104 weeks, and the SR-PLLA miniscrews had been mostly resor bed at 104 weeks. Passive translocation of the titanium plates and screws i nto the bone tissue was seen at 52 and 104 weeks. In rapidly growing lamb f rontal bone, comparable consolidation results, without complications, can b e achieved with semirigid resorbable fixation compared with rigid metallic fixation.