Comparable Tibial Tunnel Widening despite Compound Differences of Bioabsorbable Interference Screws in Anterior Cruciate Ligament Reconstruction: a Retrospective Study

Purpose. To evaluate the effect of 13-tricalcium phosphate (BCP) concentration in bioabsorbable interference screws on tibial tunnel widening after hamstring anterior cruciate ligament reconstruction. Methods. A total of 37 patients with a mean follow-up of 4.6 years were included for analysis. Bioabsorbable interference screws containing 60% BCP and 40% poly-L,D-lactic acid (PLDLA) (60BCP group) or bioabsorbable interference screws contain-ing 30% BCP and 70% PLDLA (30BCP group) were used for tibial graft fixation. A 16-slice multislice computertomography scanner with post-process multislab reconstructions was used for tibial tunnel evaluation. The tibial tunnel diameter was measured at the midpoint of the tunnel. Tunnel widening was defined as an increase of more than 2 mm compared to the intraoperative drill diameter. Results. Patient demographics were not statistically different between both groups. The number of patients that showed tibial tunnel widening was high but did not differ statistically significant between the 60BCP and 30BCP group: 76% (n = 17) versus 75% (n = 20) for 60BCP and 30BCP group, respectively. The average increase in tibi-al tunnel diameter did not differ statistically significant between the groups; the tibial tunnel diameter increased with an average of 3.36 mm (SD 1.86) and 2.94 mm (SD 1.63) for the 60BCP and 30BCP group, respectively. Conclusions. A high incidence of tibial tunnel widening was observed when bioab-sorbable interference screws containing different concentrations of 13-tricalcium phos-phate were used to fixate the hamstring graft in anterior cruciate ligament recon-struction. Increasing the concentration 13-tricalcium phosphate did not result in less tunnel widening.