The determination of safe zones for arthroscopic portal placement into the posterior knee by mapping the courses of neurovascular structures in relation to bony landmarks

Abstract

Minimally invasive surgery in the posterior knee is high-risk for iatrogenic injury to popliteal neurovasculature structures. This study aimed to use reliable landmarks to define safe zones for arthroscopic portal placement into the posterior knee. Methods:Distances were measured between bony landmarks and neurovascular structures within the popliteal fossa using 45 formalin-embalmed cadavers: small saphenous vein (SSV), medial (MCSN) and lateral (LCSN) cutaneous sural nerves, tibial nerve (TN), common fibular nerve (CFN), popliteal vein (PV) and artery (PA). The structures were measured in relation to medial (MEF) and lateral (LEF) femoral epicondyle, medial (MCT) and lateral (LCT) tibial condyle and the midpoint between the landmarks.

A Posteromedial Portal Allows Access to the Posteromedial Knee, While a Posterolateral Portal Risks Common Fibular Nerve Injury: A Cadaveric Analysis

“…However, the fresh-frozen cohort saw no incidence of damage and reported significantly larger distances between the medial-lying cannula and the neurovascular structures ( P < .001). The results from the study align with the results from Greenwood et al., 12 which suggested a 99% success rate of safe insertion if the cannula was placed no greater than 20 mm from the medial bony landmarks.…”

“…The formalin-embalmed cadaveric knees were used to confirm the accuracy of the Greenwood et al. 12 safe zones. Cannula insertion was performed in the prone position and with the knees fully extended.…”

“…This approach was used to replicate the methodology described by Greenwood et al. 12 Once these safe zones were confirmed as accurate, the safe zones were then tested in a sample of 9 fresh-frozen knees. Portal placement was performed in 90 degrees of flexion to mimic a clinical setting and provide more clinically translatable results more closely.…”

“…The portal positions were based on published safe zones by Greenwood et al. 12 For the direct medial-lying posterior portal, a 6-mm diameter twist-in cannula Arthrex Twist-In (AR-6535TD) (Arthrex) was placed 16 mm lateral to point A ( Figure 2 ). For the direct lateral portal, the cannula was placed 14 mm medial to point B in males and 8 mm medial to point B in females ( Fig 2 ).…”

“… 11 Recently, Greenwood et al. 12 have reported anatomic safe zones for direct posterior portal placement into the knee.…”