Background and Objectives This case series assesses the in vivo spread of contrast within the adductor canal in subjects who recently underwent a total knee arthroplasty. A previous analysis of profound leg weakness with a continuous adductor canal revealed contrast spread from the adductor canal to the femoral triangle with as little as 2 mL of volume.

Methods We enrolled 10 American Society of Anesthesiologists class II–III subjects. Maximum voluntary isometric contraction was measured to assess quadriceps strength before and after surgery. Contrast was then injected continuously via electronic pump into the adductor canal, and fluoroscopy was used to capture images after 1-mL increments. For analysis, the femur was divided into 8 equidistant sectors between the lesser trochanter and medial epicondyle.

Results Contrast did not reach the level of the lesser trochanter or the medial epicondyle of the femur in any subject. The greatest spread after 5 mL of contrast was 4 sectors. Sixty percent of subjects had contrast spread within either the same sector as the catheter tip or 1 sector distally. No subjects demonstrated additional proximal spread of contrast after 4 mL.

Conclusions This study reveals that in vivo continuous infusions within the adductor canal spread in both a cephalad and caudad direction in limited fashion. Although a previous report described proximal spread of injectate to the level of the common femoral nerve, this event is infrequent.