Bioresorbable Stent in Anterior Cruciate Ligament Reconstruction

Abstract

The exact causes of failure of anterior cruciate ligament (ACL) reconstruction are still unknown. A key to successful ACL reconstruction is the prevention of bone tunnel enlargement (BTE). In this study, a new strategy to improve the outcome of ACL reconstruction was analyzed using a bioresorbable polylactide (PLA) stent as a catalyst for the healing process. The study included 24 sheep with 12 months of age. The animals were randomized to the PLA group (n = 16) and control group (n = 8), subjected to the ACL reconstruction with and without the implantation of the PLA tube, respectively. The sheep were sacrificed 6 or 12 weeks post-procedure, and their knee joints were evaluated by X-ray microcomputed tomography with a 50 µm resolution. While the analysis of tibial and femoral tunnel diameters and volumes demonstrated the presence of BTE in both groups, the enlargement was less evident in the PLA group. Also, the microstructural parameters of the bone adjacent to the tunnels tended to be better in the PLA group. This suggested that the implantation of a bioresorbable PLA tube might facilitate osteointegration of the tendon graft after the ACL reconstruction. The beneficial effects of the stent were likely associated with osteogenic and osteoconductive properties of polylactide.2 of 20 to be optimal and complication-free [1][2][3]. The failures of ACL reconstruction might be associated with an inappropriate orientation of bone tunnels, use of improper fixation methods and materials, and inadequate rehabilitation, as well as with mechanical behavior of the bone and biological processes that occur during remodeling, maturation, and incorporation of the graft [4,5]. The healing potential of a newly implanted graft is relatively low [6][7][8] and is primarily determined by conditions within proximity of the bone tunnel and soft tissue of the graft, including the intra-articular environment. Osteointegration of the tendon grafts used for ACL reconstruction is still far from satisfactory, although several strategies have been postulated to improve the process [9][10][11][12][13][14][15][16][17][18][19].Another critical determinant of successful ACL reconstruction is the prevention of bone tunnel enlargement (BTE), a phenomenon of mechanical and biological etiology. The mechanical causes of BTE might be related to the tunnel drilling technique, graft fixation technique, vibrations at the tunnel entry, and movements of the graft referred to as "bungee effect" and "windshield wiper effect" [20][21][22][23][24][25]. The biological mechanisms involved in the BTE include accumulation of intra-articular fluid, which penetrates to the space between the graft and the wall of the bone tunnel. The sites in which the graft is not adjacent closely to the bone tunnel wall, the so-called "dead space", are particularly prone to fluid accumulation. The intra-articular fluid that accumulates after the ACL rupture contains proinflammatory cytokines, which are responsible for local osteolysis [26][27][28][29]. Another biological mechanism ...

Effect of Demineralized Bone Matrix, Bone Marrow Mesenchymal Stromal Cells, and Platelet-Rich Plasma on Bone Tunnel Healing After Anterior Cruciate Ligament Reconstruction: A Comparative Micro-Computed Tomography Study in a Tendon Allograft Sheep Model

“…8 In this study, the bone tunnels were divided into thirds as described previously. 10,48 In our study, there were no significant differences between femoral and tibial tunnels in the control group for trabecular bone analysis or BMD. Nevertheless, some differences were seen when using orthobiologics.…”

“…3 In a rabbit model using suspensory fixation, graft-tunnel motion was greatest at the tunnel apertures with closer apposition of bone to tendon seen at the tunnel exits than at the tunnel aperture. 31 Ficek et al 10 reported the bone tunnel enlargement in sheep using suspensory fixation and Achilles tendon autograft. After 12 weeks, the tunnel tended to be wider at its aperture in the control group, whereas this was not seen in the group using a poly-96L/4D-lactic acid stent.…”

“…After 12 weeks, the tunnel tended to be wider at its aperture in the control group, whereas this was not seen in the group using a poly-96L/4D-lactic acid stent. 10…”

“…After 12 weeks, the tunnel tended to be wider at its aperture in the control group, whereas this was not seen in the group using a poly-96L/4D-lactic acid stent. 10 In humans, MRI shows that tunnel widening occurs in the first 6 to 24 weeks, 44 but despite conflicting reports, a systematic review showed no significant difference in femoral tunnel widening between the aperture and midportion in humans. 5 Possible reasons why widening would be greater at the aperture compared with midportion include biological factors such as synovial fluid influx containing osteolytic cytokines 36 and increased graft tunnel motion.…”

Bone Mesenchymal Stem Cells Contribute to Ligament Regeneration and Graft–Bone Healing after Anterior Cruciate Ligament Reconstruction with Silk–Collagen Scaffold

“…The silk–collagen scaffold was discovered to have good biocompatibility and biomechanical properties [ 12 ]. However, in the early postoperative period, limited ingrowth of the newly regenerated connective tissue in the knee cavity restricted ligament regeneration, and bone tissue in the bone tunnel disrupted graft–bone healing [ 13 , 14 ].…”