A 3.5-mm-diameter anterior cruciate ligament tibial retrograde socket drilling pin is more accurate than a 2.4-mm-diameter pin

Purpose: The purpose of this study was to evaluate the accuracy of a 3.5-mm-diameter anterior cruciate ligament (ACL) tibial retrograde socket drilling pin versus a standard, 2.4-mm drill-tipped guide pin. A secondary purpose was to evaluate surgeon precision in identifying the true (anatomic) center of the ACL tibial footprint using arthroscopic visualization.

Methods: Six matched pairs of cadaveric knees were disarticulated, leaving a well-defined footprint of the ACL on the tibial plateau. The tibial footprint was digitally recorded by a bioengineer, and the true center of the footprint was calculated. Next, using arthroscopic visualization, a surgeon identified and marked his estimation of the true center of the ACL tibial footprint. This mark was then digitally recorded by the bioengineer and compared with the calculated center, allowing quantification of surgeon anatomic precision. Finally, under arthroscopic visualization, the surgeon was given 1 attempt to aim and drill the guide pin to his mark. Pin position was digitally recorded; the distance of the drill pin from the mark quantified drill pin placement accuracy.

Results: Mean accuracy for the 3.5-mm retrograde socket drilling pin was 1.06 ± 0.75 mm versus 3.03 ± 1.00 mm for the 2.4-mm pin. The difference was significant (P < .005). Surgeon anatomic precision was 2.7 ± 1.4 mm.

Conclusions: Our results show that a 3.5-mm-diameter ACL tibial retrograde socket drilling pin is significantly more accurate than a 2.4-mm-diameter pin. The 3.5-mm pin accuracy is within the range of surgeon precision; the 2.4-mm pin accuracy is not.

Clinical relevance: Pin accuracy and surgeon precision are clinically relevant measures because anatomic tunnel placement is a determinant of ACL reconstruction outcome.