Reply to: Comments on Alentorn-Geli et al.: Anteromedial portal (AMP) versus transtibial (TT) drilling techniques in ACL reconstruction: a blinded cross-sectional study at two- to five-year follow-up

Abstract

Dear Editor, We read with great interest the comments on our article entitled “Anteromedial portal (AMP) versus transtibial (TT) drilling techniques in ACL reconstruction: a blinded crosssectional study at twoto five-year follow-up” [1] by Sunil Gurpur Kini. In his first concern, Dr. Kini states that the TT group in our study may have more knee laxity because of a too vertical tibial starting point considering that we drilled at 20° in the coronal plane. Studies referenced by Dr. Kini to support his first concern reported a tibial tunnel orientation of 60–70° in the coronal plane, but these angles were considered from the horizontal line, whereas the 20° in our study was considered from the vertical line [4, 5, 7]. Other authors perform the tibial tunnel with a mean angulation of 60.6°, ranging up to 74.2° [9]. Thus, we can not assume our tibial tunnel significantly differs from the existing literature. Dr. Kini highlighted the excellent cadaveric study by Bedi et al. [3] comparing the AMP and TT drilling. The TT drilling was performed with oblique positioning of the tibial guide at 60° in the coronal plane, reaching a mean femoral angulation of 54.81° ± 7.17°, corresponding approximately to 10:45 in a clock position. The TT group in our study had the femoral tunnel in the 11 (or 13) o’clock position, which we believe is comparable with the interesting study by Bedi et al. Although both TT and AMP drilling may produce a femoral tunnel close to ACL footprints, the tibial starting point to achieve this position in the TT drilling must be more medial and could be too close to the tibial joint line. This may result in a short tibial tunnel and enlarged tibial tunnel aperture, which may in turn compromise the graft fixation and incorporation [6]. In addition, a too medialised tibial tunnel starting point during the TT technique may result in an increased risk of injury to the MCL, and may produce a more lateral and posterior tibial tunnel intraarticular entry point resulting in a less effective reconstruction from a biomechanical point of view [8]. In his other concern, Dr. Kini discusses the risk of a short femoral tunnel and the increased risk of posterior wall blow out with the AMP technique. In our experience with the AMP technique, the posterior wall blow out is extremely rare. Using the Acufex Endoscopic femoral drill guide (Smith and Nephew®), a security distance can be systematically left in the posterior wall of the femoral condyle, thus preventing its rupture. The posterior wall Eduard Alentorn-Geli and Gonzalo Samitier contributed equally to this work. E. Alentorn-Geli : P. Alvarez :R. Cugat Artroscopia Garcia-Cugat, Hospital Quiron, Barcelona, Spain