Abstract
The interference screw fixation method is used to secure a graft in the tibial tunnel during anterior cruciate ligament reconstruction surgery. However, several complications have been reported, such as biodegradable screw breakage, inflammatory or foreign body reaction, tunnel enlargement, and delayed graft healing. Using additive manufacturing (AM) technology, we developed a titanium alloy (Ti6Al4V) interference screw with chemically calcium phosphate surface modification technology to improve bone integration in the tibial tunnel. After chemical and heat treatment, the titanium screw formed a dense apatite layer on the metal surface in simulated body fluid. Twenty-seven New Zealand white rabbits were randomly divided into control and additive manufactured (AMD) screw groups. The long digital extensor tendon was detached and translated into a tibial plateau tunnel (diameter: 2.0 mm) and transfixed with an interference screw while the paw was in dorsiflexion. Biomechanical analyses, histological analyses, and an imaging study were performed at 1, 3, and 6 months. The biomechanical test showed that the ultimate pull-out load failure was significantly higher in the AMD screw group in all tested periods. Micro-computed tomography analyses revealed early woven bone formation in the AMD screw group at 1 and 3 months. In conclusion, AMD screws with bioactive surface modification improved bone ingrowth and enhanced biomechanical performance in a rabbit model.
Highlights
Anterior cruciate ligament (ACL) tears are a common sports injury, and ACL reconstruction (ACLR) is the most performed procedure to restore knee stability to enable a return to sports [1]
A rough surface and porous structure have been reported to improve bone healing and reduce micromotion after screw implantation [19,27]. Such results are compatible with our study, where the total bone volume fraction was significantly higher at the 1- and 3-month follow-ups, which is crucial for graft healing after ACLR surgery
These results reflect the porous structure on the additive manufactured (AMD) screw and the surface modification that occurred with calcium phosphate (CaP) apatite
Summary
Anterior cruciate ligament (ACL) tears are a common sports injury, and ACL reconstruction (ACLR) is the most performed procedure to restore knee stability to enable a return to sports [1]. Clinical outcomes have been equivalent after the use of bioabsorbable screws and metal interference screws for tibial graft fixation [4]; higher rates of effusion, screw breakage, and incomplete tunnel healing have been reported for bioabsorbable screws compared with titanium alloy (Ti) interference screws [5]. The rate of clinical sequelae from bioabsorbable tibial interference screws was high, with symptoms in approximately 1 of 10 ACLRs in adolescents [6]. In this rabbit study, we selected Depuy Synthes Ti cortical screws as the control groups for tibial intratunnel healing and compared them with experimental screws of the same diameter and similar morphology. We evaluated the effects of Ti interference screws on tibial bone–tendon graft incorporation
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