Adductor Canal Block Ultrasound Anatomy in Volunteers
Condition: Adductor Canal Block; Postop Analgesia for Knee
Study type: Observational

Summary: 
      There has been dispute about the location at which the adductor canal block should be
      performed (3-6). Two Common approaches have been used for ultrasound guided adductor canal
      blocks with the 'point of entry' being:

        1. Point A: midway point between the ASIS and base of patella

        2. Point B: Point which is 2-3 cm proximal to the site where the femoral artery becomes the
           popliteal artery as it traverses away from the sartorius muscle towards the femur at the
           adductor hiatus (2)

      We want to determine ultrasound anatomy in healthy volunteers by:

        1. Measuring the distance between Point A and Point B

        2. Studying the ultrasound anatomy at Point A and B - Determine their location with respect
           to the adductor canal and femoral triangle.

      This will allow us to determine which is the best site for performing an adductor canal block
    

Detailed description: 
      It is important to answer the primary question because of the variable length of the adductor
      canal and we would like to determine the optimal position to perform the adductor canal
      block.

      The adductor canal typically contains the saphenous nerve, nerve to vastus medialis muscle
      and on occasion, the obturator nerve (1). The roof of adductor canal is the vasto-adductor
      membrane and its length is reported to range from 5.5 cm to 15 cm with a mean of 7.6 cm2 and
      would suggest the length of the AC is variable. We would like to determine the length of the
      AC with the use of ultrasound. The AC would be determined to begin at the apex of the femoral
      triangle and end just proximal to the adductor hiatus. The length and location of the AC
      would be important to characterize as the volume of local anesthetic used and associated
      quadriceps weakness could be of significance in a shorter AC.

      There has been dispute about the location at which the adductor canal block should be
      performed (3-6). Point A has been disputed to be within the femoral triangle and would
      therefore be a femoral nerve block as suggested by a small body of evidence (4-5).
      Clinically, it is unclear if there is a difference between quadriceps muscle weakness between
      the two approaches although it could be hypothesized placing a block at point A would lead to
      more quadriceps muscle weakness. With information gathered from this study, we plan to
      perform a clinical study by performing the nerve blocks at these two points with different
      volumes of local anesthetic and compare the amount analgesia and motor weakness between the
      two different approaches.

      60 Volunteers (30 male and 30 female) aged between 18 to 75 years with a body mass index of
      18 to 35 kg/m2 will be included in this study. Volunteers with previous surgery or
      deformities of the lower extremity will be excluded from the study

      This is an observational study without a control group. Several reference points will be
      marked by anatomical landmarks and/or ultrasound:

      A. the anterior superior iliac spine (landmark); B. the base of the patella (landmark); C.
      apex of femoral triangle (ultrasound); and D. distal most portion of adductor canal (Point B
      described earlier; ultrasound).

      The primary outcome measure we are looking at is the distance between Point A and Point B.

      We also plan to measure the distance (in centimeters) from:

        1. Base of patella to Point A

        2. Base of patella to Point B

        3. Apex of the femoral triangle
    

Intervention name(s): Ultrasound scanning of the lower limb in volunteers
Intervention type(s): Other
Intervention description(s): Several reference points will be marked by anatomical landmarks and/or ultrasound: the anterior superior iliac spine; base of patella; apex of the femoral triangle A measuring tape will be used to measure the anterior superior iliac spine (landmark); the base of the patella (landmark); apex of femoral triangle (ultrasound); and distal most portion of adductor canal (Point B described earlier; ultrasound). We will then measure the ASIS to: 1) base of patella; 2) apex of femoral triangle; and 3) Point B. We will repeat the same procedure on the opposite leg. Once complete, the volunteer will be allowed to dress and leave. The procedure should take approximately 10-20 minutes for each volunteer. The following things will be recorded for each subject:
Age
Gender
Weight
Height
BMI
Distance of ASIS to base of patella
Distance of Point A to base of patella
Distance of Point B to base of patella
Distance of apex of femoral triangle to base of patella
Observational model: Case-Only
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        We aim to recruit volunteers who principally are healthcare employees at UIHC who mainly
        work in the Main Operating Rooms and Ambulatory Surgical Center Operating Rooms, mainly due
        to ease of access to ultrasonographic equipment. The subjects include anesthesiologists,
        certified registered nurse anesthetists, residents, interns, nurses, volunteers,
        technicians, administrative staff and other members of staff working in these areas.