Regarding “Radiologic and Clinical Outcomes After Hamstring Anterior Cruciate Ligament Reconstruction Using an Adjustable‐Loop Cortical Suspension Device With Retensioning and Knot Tying” (2020)

This clinical study by Choi et al.1Choi N.H. Park T.H. Oh W.K. Victoroff B.N. Radiologic and clinical outcomes after hamstring anterior cruciate ligament reconstruction using an adjustable-loop cortical suspension device with retensioning and knot tying.Arthroscopy. 2019; 35: 2629-2633Abstract Full Text Full Text PDF PubMed Scopus (6) Google Scholar reported on the effects of retensioning and knot tying on the radiologic and clinical outcomes of anterior cruciate ligament (ACL) reconstruction with femoral adjustable-loop device (ALD) cortical button and tibial screw fixation. Magnetic resonance imaging (MRI) on the immediate postoperative day and subsequently at 6-months after surgery was used to measure differences in the tunnel-graft gap to correlate the gap difference with knee stability and functional outcomes. There are flaws in the methodology of this study that certainly could have affected the ultimate conclusions. First and foremost, proper technique for use of the TightRope ALD per manufacturer (Arthrex Inc., Naples, FL) and previous publications was not followed.2Karkosch R.F. Ettinger M. Bachmaier S. Wijdicks C.A. Smith T. Adjustable-length loop cortical button versus interference screw fixation in quadriceps tendon anterior cruciate ligament reconstruction – A biomechanical in vitro study.Clin Biomech (Bristol, Avon). 2018; 60: 60-65Abstract Full Text Full Text PDF Scopus (13) Google Scholar, 3Monaco E.B.S. Fabbri M. Lanzetti R.M. Wijdicks C.A. Ferretti A. Intraoperative Workflow for All-Inside Anterior Cruciate Ligament Reconstruction: An In Vitro Biomechanical Evaluation of Preconditioning and Knot Tying.Arthroscopy. 2018; 34: 538-545Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar, 4Noonan B.C. Bachmaier S. Wijdicks C.A. Bedi A. Intraoperative Preconditioning of Fixed and Adjustable Loop Suspensory Anterior Cruciate Ligament Reconstruction With Tibial Screw FixationdAn In Vitro Biomechanical Evaluation Using a Porcine Model.Arthroscopy. 2018; 34: 2668-2674Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar The authors stated that complete femoral graft insertion until tunnel docking was performed first, followed by graft retensioning and knot tying of the tensioning sutures to prevent loosening of the adjustable loop. After cyclic loading of the graft, the tibial screw was finally placed with the knee in 20° angle flexion. The correct technique is initial fixation with the femoral TightRope shortening strands to a depth shorter than the total length of the drilled socket leaving some distal gap in the femoral socket followed by tibial graft fixation and then intraoperative cycling of the knee and retensioning of the femoral shortening strands. This technical protocol is critical as tensioning on the femoral side without counter-tension of a fixed tibia may coil the sutures on the femoral side ALD and thus introduce avoidable slack into the reconstructed construct. This may be the case for patient number 6, whom presented 12mm of immediate post-operative tunnel-graft gap. Improper use of the technique will negate the major advantage of the TightRope ALD which has the ability to retension the graft after cycling the knee intraoperatively and decrease displacement. This is proven in a recent biomechanical study by Noonan et al. which showed that the surgical placement of an interference screw under simulated single-hand ACLR graft tensioning could impart time-zero laxity and loss of graft tension.4Noonan B.C. Bachmaier S. Wijdicks C.A. Bedi A. Intraoperative Preconditioning of Fixed and Adjustable Loop Suspensory Anterior Cruciate Ligament Reconstruction With Tibial Screw FixationdAn In Vitro Biomechanical Evaluation Using a Porcine Model.Arthroscopy. 2018; 34: 2668-2674Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar The operating characteristics of an ALD allowed for restoration of screw-induced graft slackening and optimizing tension with significantly reduced ACLR construct elongation, compared to non-preconditioned and fixed loop device (FLD) control groups.4Noonan B.C. Bachmaier S. Wijdicks C.A. Bedi A. Intraoperative Preconditioning of Fixed and Adjustable Loop Suspensory Anterior Cruciate Ligament Reconstruction With Tibial Screw FixationdAn In Vitro Biomechanical Evaluation Using a Porcine Model.Arthroscopy. 2018; 34: 2668-2674Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar The tensioning sequence in the publication by Choi et al. was not able to resolve time-zero screw induced laxity or graft slackening due to settling effects caused by the graft preparation and implantation. Furthermore, the authors incorrectly explain the use and advantages of a femoral ALD in the discussion when they state, “The most important advantage of the ALD compared with the fixed-loop device is that the adjustable loop can pull the graft completely to the top of the femoral tunnel.” While the ALD may help to maximize graft seating into the femoral socket, the ability of re-tensioning the graft construct after tibial fixation to eliminate creep as outlined above is clearly the major advantage over fixed loop devices. Avoidance of graft elongation is critical for a successful ACL reconstruction due to the fact that knee laxity also depends on the graft length over time5Blythe A. Tasker T. Zioupos P. ACL graft constructs: In-vitro fatigue testing highlights the occurrence of irrecoverable lengthening and the need for adequate (pre) conditioning to avert the recurrence of knee instability.Technology and Health Care. 2006; 14: 335-347Crossref PubMed Google Scholar and will not self-correct during the remodeling phase. Therefore, the ability to precycle and retension an ACLR graft may be critical for optimizing the mechanical stabilization and clinical outcomes. The reasons for ACL graft lengthening during dynamic loading are multifactorial, including insufficient graft preconditioning with possible negative correlation with the Lysholm score. Another technical concern with the authors’ use of the TightRope ALD in this study relates to their statement, “Arthroscopic visualization confirmed that the mark on the graft was flush with the outlet of the femoral tunnel, indicating full insertion of the graft into the femoral tunnel.” This is in fact not sufficient, nor an appropriate indicator, to confirm maximal seating of graft material and shortening of the ALD. The mark is, rather, a guide throughout the process and not an absolute indicator. It is critical that the shortening strands of the ALD are shortened equally and assessed after final fixation to be symmetric. The graft may be at the marked depth, although eccentric shortening of one ALD limb may leave the potential for lengthening in the system with tibial fixation and contribute to the observation of “incomplete seating” that was observed in this study. This is reflective of the technique used rather than a shortcoming of the fixation device. In contrast to computed tomography, MRI promises not only structural information on the tunnels, but also allows evaluation of the ACL graft itself. A major drawback is the limited assessment of osseous structures in MRI as it is often difficult to reliably identify soft and hard tissue structures during the remodeling phase,6Webster K.E. Chiu J.J. Feller J.A. Impact of measurement error in the analysis of bone tunnel enlargement after anterior cruciate ligament reconstruction.Am J Sports Med. 2005; 33: 1680-1687Crossref PubMed Scopus (40) Google Scholar thus the interpretation of absolute measurements using MRI could be misleading. The noted differences in the femoral tunnel-graft gap may also originate from the biological maturation and consolidation process of the graft with bony changes in the vicinity of the graft-tunnel interface.7Lu H. Chen C. Xie S. Tang Y. Qu J. Tendon Healing in Bone Tunnel after Human Anterior Cruciate Ligament Reconstruction: A Systematic Review of Histological Results.J Knee Surg. 2019; 32: 454-462Crossref Scopus (22) Google Scholar Plus, the three-dimensional PD SPACE sequences and technique utilized to measure tunnel-graft gap are not validated. Even one or two millimeters of error in measurement can suggest significant (>20%) differences in graft seating, and no intra- or inter-rater reliability data for this technique is provided. A single reviewer could introduce bias without inter- and intra-reviewer validation and standardization. An example of this variation is present in the error range of the mean tunnel-graft gap (2.8mm) was larger than the mean measurement itself (2.1mm) on the immediate postoperative day. Furthermore, there is no control group comparing a fixed loop device on the femur, this would provide a benchmark to observed gap measurements among devices. One of the conclusions of this study is based on an invalidated premise as 3-mm is selected as a significant tunnel-graft gap based on KT measurements of clinical significance for ACL stability, but the correlation between mm of translation on a Lachman test is certainly not equivalent nor reflective of mm’s of graft seating in a tunnel, and not previously documented in the literature. There is currently no known algorithm that correlates axial graft displacement in the tunnel to anterior-posterior knee translation. Additionally, a significant gap distal to the graft may acceptable and allow for no measurable laxity in the presence of graft healing. No difference is noted in laxity assessment with tunnel-graft gap, but a correlation with Lysholm score is noted. It is critical to note that the finding is associational, and by no means causational. The reason for reduced functional outcomes scores are certainly multifactorial, and there are a host of other technical and patient-specific factors that would affect this outcome score. In closing, a nice summary of pertinent literature is present in a recent systematic review comparing biomechanical and clinical outcomes between ALDs and FLDs in the femoral fixation component of ACLR, showing no clinically significant difference in functional, radiologic and complication outcomes, as well as improved biomechanical properties with retensioning of ALDs after tibial fixation, as per manufacturer recommendations.8Onggo J.R. Nambiar M. Pai V. Fixed- Versus Adjustable-Loop Devices for Femoral Fixation in Anterior Cruciate Ligament Reconstruction: A Systematic Review.Arthroscopy. 2019; 35: 2484-2498Abstract Full Text Full Text PDF Scopus (16) Google Scholar Download .pdf (2.46 MB) Help with pdf files ICMJE author disclosure forms Author Reply to “Regarding ‘Radiologic and Clinical Outcomes After Hamstring Anterior Cruciate Ligament Reconstruction Using an Adjustable-Loop Cortical Suspension Device With Retensioning and Knot Tying’”ArthroscopyVol. 36Issue 4PreviewWe would like to thank the authors, Smith and Bedi,1 for expressing interest and concern regarding our recently published article, “Radiologic and Clinical Outcomes After Hamstring Anterior Cruciate Ligament Reconstruction Using an Adjustable-Loop Cortical Suspension Device With Retensioning and Knot Tying.”2 Smith and Bedi pointed out several important issues. First, they said “proper technique for use of the TightRope ALD per manufacturer (Arthrex Inc., Naples, FL) and previous publications was not followed.” However, we followed the protocol described in the surgical brochure provided by the manufacturer. Full-Text PDF