ANATOMIC STUDY OF THE SAPHENOUS NERVE AT KNEE JOINT AND ITS CLINICAL CORRELATION TO THE PATTERN OF NERVE INJURY AFTER ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION USING HAMSTRING TENDON GRAFT

Abstract

Introduction: Reports on nerve injury after arthroscopic ACL reconstruction using hamstring tendon autograft had mainly focused on injury to the infrapatellar branch of the saphenous nerve (IPBSN), with few reports on injury of the sartorial branch of the saphenous nerve (SBSN).

Aim of the work: was to define the level of anatomical termination of the saphenous nerve in relation to knee joint level and the relation of its sartorial branch to the surrounding tendons so that it could be avoided during hamstring tendon harvesting.

Materials and Methods: This anatomical study included cadaveric dissection of the medial aspect of the knee joint of 25 preserved knees. The saphenous nerve was dissected proximal to the knee joint and followed distally till it was divided into its two terminal branches.

Results: In 68 %, the saphenous nerve gave its two terminal branches at a mean distance of 8 cm above the knee joint line. In 32 %, the level of termination of the saphenous nerve was below the knee joint line by a mean distance of 3 cm.

In 92 % the saphenous nerve or the SBSN was passing posterior to the sartorius tendon by a mean distance of 19.8 mm. In 68 % the saphenous nerve or the SBSN continued distally anterior to the gracilis tendon, while in 16 % the SBSN continued distally posterior to the gracilis tendon. In 20 % the distance between the saphenous nerve or the SBSN and gracilis tendon was 5 mm or less. In 12 % the saphenous nerve or the SBSN was lying directly anterior to the gracilis and in 4 %, the SBSN was lying directly behind the gracilis tendon at the knee joint line.

In all the knees the saphenous nerve or the SBSN was passing distally anterior to the semitendinosus tendon at a mean distance of 23.1 mm.

Conclusion: The saphenous nerve or its terminal branch the SBSN, is at a close anatomical relation with the gracilis tendon. This might predispose the nerve to be damaged during passage of the tendon stripper over the tendon.

Clinical correlation: The saphenous nerve or its terminal branch the SBSN, are at a risk of injury during arthroscopic ACL reconstruction using hamstring tendon autograft. The nerve Injury of the saphenous nerve or its terminal branch (SBSN) might be an intrinsic problem associated with the technique itself.