THE INFRAPATELLAR BRANCH OF THE SAPHENOUS NERVE - AN ANATOMIC STUDY

Objectives: To describe the course of the infrapatellar branch of saph enous nerve (IPBSN) and define a risk zone in which the nerve would pr obably be located. Design and Materials: The course of the IPBSN was s tudied in twenty-eight cadaver specimens (fifteen male and thirteen fe male) chosen haphazardly. Setting and Main Outcome Measurements: The a dductor tubercle and the junction between the inferior pole of the pat ella and the medial (point A) and lateral (point B) borders of the pat ellar tendon were taken as reference points. The level of the joint li ne as well as the point of crossing of the IPBSN at the joint line wer e measured in relation to point A. Results: The IPBSN was located at 7 .7 +/- 16.8 mm posterior to the adductor tubercle at the level of poin t A; at 0.8 +/- 20.5 mm anterior to the adductor tubercle at the level of joint line; and at 12.1 +/- 18.8 mm anterior to the adductor tuber cle at 30 degrees from point A. The IPBSN crossed to the lateral borde r of the patellar tendon in 10 of the 28 specimens (36%). The vertical distance between point B and the nerve was 37.8 +/- 23.5 mm, Three zo nes are defined in relation to point A: a safe zone, a gray zone, and a risk zone. The limits of the safe zone could be represented by a cur ved line that crosses the following points: 31.0 mm medial to point A and at the same level; 17.2 mm from point A at the joint line; 13.2 mm infromedial to point A at an angle of 30 degrees; 9.6 mm at an angle of 60 degrees; and 5.8 mm inferior to point A. Conclusion: Avoiding th e risk zone in which the nerve would probably be located and performin g a blind puncture or an arthrotomy within the safety zone may decreas e the incidence of IPBSN injury.