Abstract
Purpose
The purpose of this study was to assess radiologically the absorption of a poly L-lactide bioabsorbable interference screw used in anterior ligament reconstruction.
Methods
A case series of ten sequential patients undergoing anterior ligament reconstruction with a four-strand hamstrings technique were assessed with MRI scans at one, two, four, seven and ten years postoperatively. The scans were reported by an independent radiologist, with respect to resorption of the screw and post resorption changes in the bone. Fixation of the graft in ACL surgery is varied from metal interference screw, resorbable screws made of PLLA, and staple fixation. The advantage of resorbable screws allow imaging of the knee postoperatively, and the perceive benefit of screw resorption and replacement with host bone.
Results
No resorption had occurred after 4 years in any of the patients. By seven years screw absorption was complete in seven patients and progressive in three. Five patients displayed new bone formation within the tibial tunnel. Of the five patients with no demonstrable new bone formation, a fluid collection was present within the tibial tunnel. In one of these patients, MRI revealed formation of a ganglion beyond the limit of the tunnel. We will present the final data after ten years.
Conclusions
This study has shown that the bioabsorbable screws take longer to resorb than initial in vitro data. It is unclear as to whether any ganglion formation is related to the resorption, or the presence of the hamstring graft in the tunnel. The theoretical advantages of bio-absorbable screws must be weighed against these findings.
