Functional Outcomes of Anatomic Anterior Cruciate Ligament Reconstruction: Accessory Medial Portal versus Transtibial

Abstract

Objectives:Transtibial (TT) and accessory medial portal (AM) techniques are two of the most widely used methods for drilling the femoral tunnel in anterior cruciate ligament (ACL) reconstructions, both with the common goal of placing the graft centrally or anatomically in the ACL footprint. While previous studies have looked at drilling through a standard anteromedial portal, no study has investigated clinical outcomes, femoral tunnel length, and radiographic evaluation after drilling from either an AM portal or TT technique. The purpose of this paper is to compare these results for a single surgeon performing “anatomic” ACL reconstruction. In addition to the femoral tunnel lengths, radiographic tunnel obliquity and femoral starting points were compared between the two methods.Methods:Over a three-year period all patients who underwent anatomic ACL reconstruction by a single surgeon were evaluated for eligibility. During surgery, the center of the anatomic femoral footprint (just posterior to the bifurcate ridge) was marked with an awl viewed through the medial portal and the tibial tunnel was drilled first. If the exact mark could be reached through a transtibial approach using a freehand pin (no guide), then it was utilized; otherwise, an accessory medial portal was created and used for femoral drilling (with the knee placed in hyperflexion). Seventy-five patients met inclusion criteria for evaluation of tunnel length and radiographic analysis (tunnel obliquity, clockface starting point). The mean age of the patient population was 29.8 (+/- 10.3). Functional outcomes (IKDC scores) were evaluated at a minimum of 24 month follow-up (Avg = 26 months; range:24-32 months).Results:In the study group of 75 patients (TT group, 47; AM group, 28) there were no significant differences between AM (74.8 +/- 13.6) and TT (75 +/- 12.9) with regard to postoperative IKDC score (p = 0.95). There was a significant difference (p < 0.001) between femoral tunnel lengths, with AM tunnels averaging 34.5mm (+/- 3.3) and TT tunnels averaging 42.13 mm (+/- 6.3). There was a significant difference in femoral tunnel obliquity (AM 39.5 +/- 6.45 degrees, TT 27.2 +/- 7.7 degrees, p<0.001) and femoral starting point (AM 9:59 o’clock +/- 20 mins, TT 10:12 o’clock +/- 18 mins, p<0.001) on AP radiograph.Conclusion:This study demonstrates no significant difference in functional outcomes for ACL reconstruction between AM and TT techniques when the femoral starting point is independently judged as anatomic between techniques. Nearly 40% of the time the anatomic femoral footprint could not be reached from a TT portal and thus conversion to AM was necessary. AM tunnel lengths of less than 30mm were rare in this study.