A direct saphenous nerve block in TKA: A surgeon friendly technique! Cadaveric study

Effective management of postoperative pain in total knee arthroplasty (TKA) poses a significant challenge for surgeons. Achieving rapid recovery without pain and promoting early ambulation in immediate and early postoperative periods are essential for patient satisfaction. There are many pain management protocols including nerve blocks. Nerve blocks procedures were done using USG and anaesthetist dependent. This cadaveric study aimed to define the VMO (Vastus medialis obliquus) triangle to target the 'safe zone' of the saphenous nerve during TKA: A surgeon's friendly technique.

12 formalin-fixed embalmed cadaveric lower limbs were dissected to explore anatomy, trajectory, the relation of saphenous nerve and measured the distances from the nearby palpable bony landmarks.

The average distance to target the saphenous nerve i.e target point from midpoint of superior pole of the patella was 10.6cm, the average angle to target the saphenous nerve is the angle between the line joining the medial epicondyle to the midpoint of the superior pole of the patella is found to be 64.2°. The average distance from midpoint of superior pole patella to medial epicondyle is found to be 8.1cm. Therefore, triangle so formed using these three points (1. Medial epicondyle, 2. The midpoint of superior pole of the patella, 3. Target point of the saphenous nerve) is called a VMO triangle.

The saphenous nerve course, relations, and the distances from intraoperative bony landmarks for the VMO triangle during TKA which is a reproducible triangle so may be useful for arthroplasty surgeons to achieve successful saphenous nerve block and to avoid related complications during total knee arthroplasty (TKA).