Hip Surgical Access and Nerve Blocks
(At any time you can rotate the image or add or subtract structures. Clicking the link will always bring you back to a starting point. Remember to use rollovers to see the labels for the various structures. Also, by moving the axial plane to any point in the image on the right, you can see the cross-section on the lower left. Any coloration in the right image will be shown in the cross-sections.)
Bony landmarks for obturator, femoral and lateral femoral cutaneous nerve blocks. Note the inguinal ligament between the anterior, superior iliac spine and the pubic tubercle. Imagine a line parallel and 2.5 cm inferior to this ligament.
- obturator block: 1.5 cm inferior and 1.5 cm lateral to the pubic tubercle
- femoral block: midpoint of inguinal ligament. Note the relationship to the femoral artery and vein.
- lateral femoral cutaneous block: 2.5 cm inferior and 2.5 cm medial to the anterior, superior iliac spine (Note, the nerve was not traced beyond the inguinal ligment, but imagine it following the trajectory of the left nerve.
Surgical approach to the hip: Finding internervous planes between the femoral and gluteal nerves:
- Find the gap between the tensor fascia lata (TFL) and the sartorius by palpation (best spot to feel it is about 3-5 inches BELOW the anterior iliac spine).
- You will now need to extend the cut proximally and detach the iliac origin of the TFL to allow you to open the plane between the muscles. In the image, we remove the TFL. Although the lateral femoral cutaneous nerve is at risk, the femoral nerve and vessels are protected by sartorius.
- You now need to retract the TFL and the sartorius, which brings you to the deep layer of muscles: the rectus femoris (supplied by the femoral nerve) and the gluteus medius (supplied by the superior gluteal nerve). In the image, we remove sartoriius and highlight the rectus and gluteus medius.
- Divide the rectus femoris free from both of its origins. One (direct head) is on the anterior inferior iliac spine; the other (indirect head) is on the superior lip of the acetabulum. The second attachment is intimate with the joint capsule itself and may be hard to release. In the image, we remove the rectus femoris and gluteus medius/minimus to reveal the head of the femur.
- Femoral triangle bordered by Adductus longus, sartorius and inguinal ligament. Note the relationship of the femoral vessels, lymph and nerve. (The main lymphatic vessel -not seen- lies medial to the femoral vein) Note the greater saphenous vein traveling from superficial to deep to join the femoral vein.
- Remove the sartorius to view the course of the femoral vessels.
- Remove the rectus femoris to see the main branches of the femoral artery (note the medial circumflex in the axial section, deep to the deep femoral (deep artery of thigh) artery).
- Divide the adductor longus ~5 cm from its origin and reflect it towards its origin. In the image, we remove the adductor longus. to reveal a branch of the obturator nerve.
Bony landmarks for sciatic nerve block. Draw a line from the posterior superior iliac spine to the greater trochanter. From the midpoint of this line, draw a perpendicular line 5 cm in the inferiomedial direction. If you can, confirm this location by drawing a line from the greater trochanter to the sacral hiatus (just below the last posterior spine of the sacrum). The midpoint of this latter line should indicate the same location.
Surgical approach to the hip
- Remove the gluteus maximus to reveal key underlying structures.
- Internally (medially) rotate the hip to move the insertion of the small external rotators as far away as possible from the sciatic nerve. Detach the muscles (including the piriformis muscle close to their femoral insertion and reflect them back, onto the sciatic nerve. In the image remove the external rotators to reveal the hip joint. (The small external rotators are retained and labeled on the right side.