A 3.5-mm-Diameter Anterior Cruciate Ligament Tibial Retrograde Socket Drilling Pin Is More Accurate Than a 2.4-mm-Diameter Pin  James H. Lubowitz, M.D., John Konicek, B.S.  Arthroscopy  Volume 27, Issue 5, Pages 666-671 (May 2011) DOI: 10.1016/j.arthro.2010.11.011 Copyright © 2011 Arthroscopy Association of North America Terms and Conditions

Figure 1 Left tibia viewed anterior-posterior. The bioengineer electronically measures and records the perimeter of the ACL tibial footprint by measuring the location of circumferential points using a MicroScribe 3-dimensional digitizer; marked points on the medial tibial plateau provide a fixed-coordinate reference system for 3 sets of digitizer measurements. These data are used to calculate the anatomic center (C) of the footprint. Arthroscopy 2011 27, 666-671DOI: (10.1016/j.arthro.2010.11.011) Copyright © 2011 Arthroscopy Association of North America Terms and Conditions

Figure 2 ACL C-ring guide (left), tibial marking hook (projecting from guide on left to upper right), and 2.4-mm-diameter drill-tipped guide pin within 2.4-mm-diameter guide pin sleeve (projecting from bottom center to upper right). Arthroscopy 2011 27, 666-671DOI: (10.1016/j.arthro.2010.11.011) Copyright © 2011 Arthroscopy Association of North America Terms and Conditions

Figure 3 ACL Flipcutter guide (blue, center), tibial marking hook (silver, within guide and projecting from upper center to right), and Flipcutter (blue base and silver pin with black laser marks, projecting from bottom left to upper right; 3.5-mm-diameter guide pin sleeve not shown). Arthroscopy 2011 27, 666-671DOI: (10.1016/j.arthro.2010.11.011) Copyright © 2011 Arthroscopy Association of North America Terms and Conditions

Figure 4 Left tibia, superior view, with digital projection of ACL tibial footprint in blue. Digital calculation of the anatomic center of the footprint (C) was performed. The distance from C to the surgeon's guess of the footprint center (G) is precision. The distance from G to the guide pin tibial articular exit point (P) is pin accuracy. (Reprinted with permission.2) Arthroscopy 2011 27, 666-671DOI: (10.1016/j.arthro.2010.11.011) Copyright © 2011 Arthroscopy Association of North America Terms and Conditions

Figure 5 Pin accuracy is represented as drill pin distance from the surgeon's guess in millimeters, where guess represents the surgeon's marked prediction of the true anatomic center of the ACL tibial footprint. Black diamonds represent the standard 2.4-mm drill-tipped guide pin. Pink squares represent the 3.5-mm retrograde socket drilling pin. The 3.5-mm pin is significantly more accurate. Arthroscopy 2011 27, 666-671DOI: (10.1016/j.arthro.2010.11.011) Copyright © 2011 Arthroscopy Association of North America Terms and Conditions

Figure 6 Drill pin distance from footprint center (C-P, in millimeters) results from combined effects of imprecision (distance of true anatomic center of ACL tibial footprint from surgeon guess, C-G) and inaccuracy (distance of surgeon guess from actual guide pin position, G-P). Black diamonds represent standard 2.4-mm drill-tipped guide pin subgroup. Pink squares represent 3.5-mm retrograde socket drilling pin subgroup. Illustrated are all 12 samples, representing 2 subgroups. There are no significant differences between subgroups. Arthroscopy 2011 27, 666-671DOI: (10.1016/j.arthro.2010.11.011) Copyright © 2011 Arthroscopy Association of North America Terms and Conditions