Peripheral Nerves and Surgical Approaches to the Hip
Goals: To examine how:
- the main nerves arise from the sacral plexus.
- these nerves pass to their targets.
-“internervous” planes can be exploited in surgical approaches.
Spinal roots from L2 to S4 form the spinal nerves that innervate the hip region and lower limb. Mouse over the roots near the midline to identify the roots. Also, rotate the dissection to 90 deg and mouse over the nerves. Note that the femoral is anterior and the sciatic is posterior. (Add back skin to confirm your orientation.)
When the bones are added, we can see the bony relations of these nerves as they pass to their targets. Rotate the image to gain perspective. The femoral nerve passes anterior to the hip joint. Move the cross-section ("grab", move and release the green/blue plane in the right window) to follow the femoral nerve (yellow) from the pelvis into the thigh. The superior gluteal nerve takes a posterior approach to reach the gluteal region. The obturator nerve arises from lumbar spinal levels. Rotate the image to 110 deg to confirm that the nerve passes through the obturator foramen. The sciatic nerve takes a posterior exit from the pelvis. Rotate the image to 270 deg. to confirm.
Return to 0 deg and mouse over the roots to confirm that the nerve arises from L4 to S2 in this individual. The pudendal nerve arises from S2 to S4. Confirm by mousing over the nerves. Also identify the yellow nerves in the cross sectional image.
The femoral nerve innervates the anterior muscles of the thigh and the hip flexors. Note that they pass anterior to the head of the femur. The superior gluteal nerve innervates the tensor fascia latae and gluteus medius. These muscles reach the anterior aspect of the thigh lateral to the femoral head. You will make your anterior approach to the hip between the femoral and superior gluteal muscle groups. In the axial section, view the seam of fat between the highlighted and non-highlighted muscles anterior to the head of the femur. This approach will minimize damage to nerves.
This posterior view shows the sciatic nerve leaving the pelvis and the superior gluteal nerve entering the gluteus medius muscle. This image shows how a posterior approach to the hip involves an incision in the gluteus maximus and a division and reflection of the obturator internus tendon.