2015 ISAKOS Biennial Congress ePoster #1334

The Accessory Medial Portal for ACL Reconstruction: A Safe Zone to Avoid Complications

Jeffrey Alwine, DO, Cos Cob, CT UNITED STATES
Stephanie C. Petterson, MPT, PhD, Old Greenwich, CT UNITED STATES
Kevin D. Plancher, MD, MPH, New York, NY UNITED STATES
Orthopaedic Foundation, Stamford, CT, USA

FDA Status Not Applicable

Summary: Increased knee flexion to 110° avoids risk to the IBSN and all neurovascular structures when creating an AMP for anterior cruciate ligament reconstruction.

Abstract:

Background

The accessory medial portal (AMP) is gaining popularity for anatomical anterior cruciate ligament reconstruction (ACLR). This portal, routinely created at 60° flexion, places neurovascular structures at risk (e.g. infrapatellar branch of the saphenous nerve (IBSN), descending genicular artery). The purpose of this study was to identify a safe zone for AMP placement in ACLR to avoid neurovascular complications. We hypothesized there would be less risk to neurovascular structures by increasing knee flexion angle.

Methods

Twenty fresh-frozen, cadaveric, match-paired knees were used for dissection. A 30° arthroscope was used to make central medial (CMP), intermediate medial (IMP), and AMP portals at 60°, 90°, and 110°. Zones were defined by reference points made by the IMP, AMP, and medial border of the patellar tendon. Distance was measured from portal to IBSN branches using calipers accurate to 0.01mm. Violation of any neurovascular structures was recorded. ANOVA and chi-square were used for data analysis (p<0.05).

Results

The AMP 60° was the closest portal to the superior IBSN (5.63±5mm). The AMP was significantly further from the superior IBSN at 110° (8.56±5mm) compared to 60° (p=0.012). The superior IBSN was most frequently pierced when the AMP was made at 60°(28%), but never pierced at 90° or 110° (p=0.002). The triangular safe zone at 110° was 11.34mm distal to the inferior pole, 22.36mm medial from the patellar tendon, with a 25.23mm hypotenuse connecting these points. The descending genicular artery was not found within the safe zone.

Conclusion

Increased knee flexion to 110° avoids risk to the IBSN and all neurovascular structures when creating an AMP for ACLR. The IBSN and vascular structures are at risk with traditional AMP placement at 60°. The superior IBSN moves inferiorly with knee flexion, away from the zone of surgery. A safe zone at 110°, easily identified with common landmarks, decreases the risk of any neurovascular injury, improving the safety of the AMP for ACLR. Surgeons who stray outside the AMP safe zone risk complications of the descending genicular artery.