A Biomechanical Study of Two Modified Dioabsorbable Interference Screw for Fixation of Soft Tis-sue Grafts in Anterior Cruciate Ligament Reconstruction

Abstract：Objective To evaluate the biomechanical properties of soft-tissue grafts reconstructed anterior cruciate liga-ment(ACL)with two modified bioabsorbable interference screws,Poly-L-lactic acid/ hydroxyapatite/ α-Fe2 O3(PLLA/ HA/ α-Fe2 O3 )screw and Poly-L-lactic acid-polyethylene glycol/ hydroxyapatite( PLLA-PEG/ HA)screw. Methods Porcine tibia and hoof extensor tendons were divided into 3 matched groups with 8 tibia and 8 extensor tendons in each group. PLLA/ HA/ α-Fe2 O3 screws、PLLA-PEG/ HA screws and poly-L-lactic acid and hydroxyapatite(BioRCI-HA,Smith ﹠ Nephew,USA)screws were used for tibial fixation in soft-tissue grafts ACL reconstruction. All specimens were subjected to tensile loading,including load to failure,stiffness and mechanism of failure recorded. Results The mean load to failure were(483. 4 ± 103. 8)N in BioRCI-HA screw group,(456. 0 ± 102. 0)N in PLLA/ HA/ α-Fe2 O3 screw group,(445. 7 ± 90. 1)N in PLLA-PEG/ HA screw group. No statistically significant differences were noted in mean load to failure. The mean stiffness:BioRCI-HA screw (48. 0 ± 6. 7)N/ mm ﹥ PLLA-PEG/ HA screw(40. 7 ± 6. 7)N/ mm and PLLA/ HA/ α-Fe2 O3 screw(41. 2 ± 4. 6)N/ mm. BioRCI-HA screws showed a greater stiffness than PLLA-PEG/ HA screws and PLLA/ HA/ α-Fe2 O3 screws respectively. Mech-anism of failure recorded:no graft failure or fixation failure was observed in either testing. When testing for pull out failure,all grafts were slipped out. Conclusion In this porcine model,PLLA-PEG/ HA screws and PLLA/ HA/ α-Fe2 O3 screws provided comparable biomechanical strength with BioRCI-HA screw.