Safe zone for the descending genicular artery in the midvastus approach to the knee

Minimally invasive total knee arthroplasty is performed using a modified version of the standard total knee arthroplasty without complete knee exposure. Traditional medial parapatellar arthrotomy has been criticized because it may disturb patellar blood flow and the extensor mechanism. Devascularization of the patella leading to osteonecrosis places the patella at risk for fracture. Alternative vastus-orientated approaches have the potential to preserve the descending genicular artery. Although this arterial supply to the patella potentially can be compromised throughout surgery, it is particularly vulnerable during deep dissection and arthrotomy. Knowledge of the anatomic course of the descending genicular artery would likely be helpful in its preservation. We investigated the course of the descending genicular artery and its entry angle to peripatellar network to determine the distance between the artery and superomedial patella during medial parapatellar arthrotomy and proximal capsular release. We dissected the descending genicular artery in 15 cadaveric knees. The average entry angle was 32.6 degrees, and the average distance between the descending genicular artery and superomedial pole of the patella during parapatellar arthrotomy was 13.5 mm. The safest distance for splitting the vastus medialis during median parapatellar arthrotomy was 15 mm from the superior pole of the patella because of the course of the descending genicular artery.