Comparison of Acorn and Fluted Reamers on Tibial Tunnel Outer Aperture Dimensions in ACL Reconstruction

The aim of this study was to determine if the type of reamer used in tibial tunnel creation during anterior cruciate ligament (ACL) reconstruction influences the dimensions of the tunnel's outer aperture. Tibial tunnels were created in tibial saw bones by reaming over a guidewire using an 8 mm acorn or fluted reamer in an antegrade manner. Reaming was aimed either in line with the guidewire, or with 10-degree inferior/superior deviation in relation to the wire. The shape and size of the outer aperture of the tibial tunnel were compared between the two reamers. When using the acorn reamer, a 10-degree deviation in relation to the guidewire resulted in minimal change in outer aperture length (mean 13.6 vs. 15.6 mm, p = 0.11) and width (11.6 vs. 11.1 mm, p = 0.51). However, when using the fluted reamer, although the aperture width showed no substantial change with reamer/guidewire deviation (11.4 vs. 11.2 mm, p = 0.71), the mean length almost doubled (14.7 vs. 28.1 mm, p = 0.002). The use of a fluted reamer when reaming the tibial tunnel creates a distal aperture which is inconsistently sized, larger, and of oblong shape compared with an acorn-shaped reamer. This should be taken in consideration when using a fluted reamer for creating the tibial tunnel in ACL reconstruction.