Fixation strength of a biodegradable screw in anterior cruciate ligament reconstruction

Abstract

We compared the strength of fixation of a biodegradable screw with that of two metal screws in a bone-patellar-tendon-bone (BPTB) graft in the bovine knee. We used 33 fresh BPTB specimens with a circular tibial bone plug of 9 mm in diameter which were anchored in a tibial metaphyseal bone tunnel with either an interference screw (n = 11), an AO cancellous screw (n = 11) or a fibrillated, self-reinforced biodegradable poly-L-lactide screw (n = 11). The mean force to failure (+/- SD) in the three groups was 1358 +/- 348 N, 1081 +/- 331 N and 1211 +/- 362 N, respectively. There was no significant difference in the groups with regard to the linear load or the elastic moduli of the fixation. We conclude that the biodegradable screw is as good as either of the two metal screws in the fixation of a BPTB graft in the bovine knee and can be recommended for ACL reconstruction using this type of graft.

Poly-L-lactic acid — hydroxyapatite (PLLA-HA) bioabsorbable interference screws for tibial graft fixation in anterior cruciate ligament (ACL) reconstruction surgery: MR evaluation of osteointegration and degradation features

“…Such screws are not, however, free of limitations. These are related to surgical technique, excessive hydrolysation of the screw, decreased pH, biocompatibility problems and incomplete osteointegration with resulting loss of torsional strength and graft instability [4][5][6]. This has led to the introduction of screws composed of materials having biomechanical properties that are both more reliable and closer to those of metallic implants, that is, materials that are not only bioabsorbable and biocompatible but also osteoinductive: polymer-ceramic composite materials made up of PLLA and hydroxyapatite (HA) granules.…”

“…Negli ultimi anni le applicazioni cliniche hanno rivolto particolare interesse a viti composte da polimeri di acidi polilattici (PLLA), che sono dotate di resistente fissazione del neo-legamento, paragonabile a quella dei mezzi di sintesi metallici, possibilità di revisione chirurgica, scarsa risposta infiammatoria, bassa incidenza a reazioni avverse, facilità di incorporazione biologica dell'innesto nel tunnel osseo [3]. Tali viti tuttavia non sono scevre da limiti che sono in parte legati alla tecnica operatoria, in parte dovuti alla eccessiva idrolisi che subisce la vite, alla diminuizione del pH e a problemi di biocompatibilità, e in parte dovuti alla non completa integrazione ossea con conseguente perdita della forza torsionale dell'innesto e conseguente instabilità [4][5][6]. Pertanto si è pensato all'introduzione di viti costituite da materiali dotati di caratteristiche biomeccaniche più affidabili e più vicine a quelle dei mezzi di sintesi metallici, ovvero a composti che oltre che dotati di caratteristiche di bioriassorbibilità e biocompatibilità posseggono altresì la peculiarità di essere osteoinducenti; si tratta di composti polimerici-ceramici costituiti da acidi polilattici (PLLA) e granuli di idrossiapatite (HA).…”

Bioresorbable screws reinforced with phosphate glass fibre: Manufacturing and mechanical property characterisation

“…Metallic and bioresorbable screws have similar pull-out failure loads (Beevers, 2003;Seil et al, 1998;Johnson and vanDyk, 1996;Abate et al, 1998;Caborn et al, 1997;Kousa et al, 1995;Hoffmann et al, 1999). This was ascribed to the fact that the screw engages predominantly with cancellous bone and partially with cortical and the mechanical properties of cancellous bone are lower than either metal or the bioresorbable polymer.…”

Principles of Development and Use of Absorbable Internal Fixation

“…59 Similarly, absorbable and metal screws have been shown to be biomechanically equivalent in stabilizing basilar osteotomies of the first metatarsal 59 and fixing bone-patellar tendon-bone anterior cruciate ligament grafts. 32,60,61 Absorbable implants should not simply mimic the designs of their metal counterparts Implant design is inexorably linked to material properties and clinical application. As such, the design of an absorbable implant would be expected to deviate from that of its metal counterpart for a given clinical application.…”