DETERMINING THE SAFETY AND ACCESSIBILITY OF DIRECT POSTERIOR PORTALS INTO THE KNEE WITH RESPECT TO THE NEUROVASCULAR STRUCTURES: A CADAVERIC STUDY

Abstract

The posterior compartments of the knee are currently accessed arthroscopically through anterior, posteromedial or posterolateral portals. A direct posterior portal to access the posterior compartments has been overlooked due to a perceived high-risk of injury to the popliteal neurovascular structures. Therefore, this study aimed to investigate the safety and accessibility of a direct posterior portal into the knee.This cross-sectional study comprised a sample of 95 formalin-embalmed cadaveric knees and 9 fresh-frozen knees. Cannulas were inserted into the knees, 16mm from the vertical plane between the medial epicondyle of the femur and medial condyle of the tibia and 8 and 14mm (females and males respectively) from the vertical plane connecting the lateral femoral epicondyle and lateral tibial condyle. Landmarks were identified in full extension and cannula insertion was completed with the formalin-embalmed knees in full extension and the fresh-frozen in 90-degree flexion. Posterior aspects of the knees were dissected from superficial to deep, to assess potential damage caused by cannula insertion. Incidence of neurovascular damage was 9.6% (n=10); 0.96% medial cannula and 8.7% lateral cannula. The medial cannula damaged one small saphenous vein (SSV) in a male specimen. The lateral cannula damaged one SSV, 7 common fibular nerves (CFN) and both CFN and lateral cutaneous sural nerve in one specimen. All incidences of damage occurred in formalin-embalmed knees. The posterior horns of the menisci were accessible in all specimens.A medial-lying direct posterior portal into the knee is safe in 99% of occurrences. The lateral-lying direct posterior portal is of high risk to the CFN.