Paper # 192: Therapeutic Advantage in Selective Ligament Augmentation for Partial Tears of Anterior Cruciate Ligament

Background: The selected anterior cruciate ligament (ACL) augmentation procedure, either anteromedial (AM) or posterolateral (PL), has been introduced as a treatment of choice for the repair of partial ACL ruptures which is based on the double bundle anatomy of the ACL. The preserved mechanoreceptor and vascularity in the remnant ACL is thought to provide neurological and biological benefits. Although enhanced knee joint proprioception in ACL augmented patients has been previously reported, there are no studies that assess the biological healing advantages of the graft after the ACL augmentation procedure. Hypothesis: Selected ACL augmentation for partial tears can promote the healing process of the grafted tendon and provide better biomechanical properties compared to ACL reconstruction of a complete tear. Study Design: Controlled Laboratory Study Methods: Two different ACL injury models were established in normal rats; 1) ACL augmentation of a partial tear model and 2) an ACL reconstruction of a complete tear model. To biologically assess the models, cell infiltration and angiogenesis in the grafted tendons were analyzed using hematoxylin/eosin staining and immunostaining using isolectin B4 respectively. Additionally, rat-specific type III collagen were evaluated by immunohistochemical staining to determine the extent of healing, while anti-rat neurofilament antigen was assessed to examine proprioceptive recovery. Biological assessments of the augmented and reconstructed grafts were conducted at week 2 postoperatively and biomechanical testing was performed at week 8 postoperatively. Results: A significantly greater number of infiltrating cells were observed in the augmented graft than in the reconstructed graft as was an increase in angiogenesis. There was also an increased amount of rat-specific type III collagen and anti-rat neurofilament antigen expressed in the augmented graft compared to the reconstructed graft. Biomechanical testing showed that failure load was significantly higher in the augmentation group compared with the reconstruction group. Conclusions: Selected ACL augmentation for partial tears could have biological benefits to promote the grafted tendon resulting in a better biomechanical healing when compared to complete ACL reconstruction. Paper # 193: 3-D CT Analysis of Tunnel Widening in ACL Reconstruction Using Allograft Tendons versus Hamstring Autografts STEVEN CLAES, MD, BELGIUM CEDRIC ROBBRECHT, MEDICAL STUDENT, BELGIUM PETER MAHIEU, MD, BELGIUM PETER VERDONK, MD, PHD, BELGIUM · University Hospitals Gent, Gent, BELGIUM Summary: Tunnel widening after ACL reconstruction is significantly increased with the use of allografts compared to autografts. Abstract: Objective: Tunnel widening has been described after ACL reconstruction and is explained by mechanical and biological phenomena. The aim of this study was to examine the feasibility of Computed Tomography 3D reconstructions to study tunnel widening after ACL surgery. Secondly, the goal was to examine differences in tunnel widening between allovs. autografts and between RCI vs. BioRCI among autografts. Material and Methods: Thirty-five patients underwent ACL reconstruction performed by a single surgeon (PV). A deep-frozen tibialis posterior tendon allograft was used in 10 patients, while in 25 patients both autologous semitendinosus and gracilis tendons were implanted. All grafts were fixed by a suspensory device on the femoral cortex (Endobutton, Smith&Nephew) and with a screw (BioRCI for allografts, RCI (n 12) or BioRCI (n 13) for autografts, Smith&Nephew) and staple on the tibia. The subjects were evaluated at a minimal follow-up of 1 year using a CT-based 3D reconstruction of both femoral and tibial tunnels. Tunnel widening was measured using a best-fit cylinder model by a least square criterium using the MIMICS software program (MIMICS v.13, Materialise, Belgium). Results: On the femoral side, tunnels were enlarged by 53% in the allograft group versus 35% for the autograft group. On the tibial side, tunnels were enlarged 48% in e199 ABSTRACTS Objective: Tunnel widening has been described after ACL reconstruction and is explained by mechanical and biological phenomena. The aim of this study was to examine the feasibility of Computed Tomography 3D reconstructions to study tunnel widening after ACL surgery. Secondly, the goal was to examine differences in tunnel widening between allovs. autografts and between RCI vs. BioRCI among autografts. Material and Methods: Thirty-five patients underwent ACL reconstruction performed by a single surgeon (PV). A deep-frozen tibialis posterior tendon allograft was used in 10 patients, while in 25 patients both autologous semitendinosus and gracilis tendons were implanted. All grafts were fixed by a suspensory device on the femoral cortex (Endobutton, Smith&Nephew) and with a screw (BioRCI for allografts, RCI (n 12) or BioRCI (n 13) for autografts, Smith&Nephew) and staple on the tibia. The subjects were evaluated at a minimal follow-up of 1 year using a CT-based 3D reconstruction of both femoral and tibial tunnels. Tunnel widening was measured using a best-fit cylinder model by a least square criterium using the MIMICS software program (MIMICS v.13, Materialise, Belgium). Results: On the femoral side, tunnels were enlarged by 53% in the allograft group versus 35% for the autograft group. On the tibial side, tunnels were enlarged 48% in e199 ABSTRACTS