**2.4 Neurologic anatomy**

There are two important plexus: lumbar plexus and sacral plexus.

*The Lumbar plexus* consists of the first three lumbar anterior rami and a portion of the anterior ramus of the fourth lumbar nerve. There are also short collateral rami, which include the hypogastric, ilioinguinal, genitofemoral, and lateral femoral cutaneous nerve. Femoral and obturator nerves are the terminal rami of lumbar plexus.

*The obturator nerve* receives contributions from the L2, L3, and L4 trunks. It continues into the pelvis underneath the iliopectineal line, reaches the obturator orifice. It exits the pelvis together with the obturator vessels.

*The femoral nerve* receives contributions from the L2, L3, and L4 trunks [19–21].

**9**

**Figure 6.**

*The greater sciatic notch is divided by the piriformis.*

*Surgical Anatomy of Acetabulum and Biomechanics DOI: http://dx.doi.org/10.5772/intechopen.92330*

of sciatic nerve [21, 22] (**Figure 6**).

**3. Radiographic evaluation**

*The Sacral Plexus* is formed by the coalescence of the lumbosacral trunk (L5 anterior ramus with L4 anastomotic ramus) and the anterior rami of the first four sacral roots. The plexus ultimately becomes the sciatic nerve (posterior tibial and peroneal nerve). The posterior branches relevant to orthopedic surgery are the superior gluteal nerve, branches to the external rotators and inferior gluteal nerve. The sciatic nerve exits the greater sciatic notch. In 85% of the cases, it courses in front of the piriformis. The other variants include penetration and splitting around the muscle. After exiting through greater sciatic notch, it courses behind the obturator internus, under the gluteal sling to enter the thigh. The sciatic nerve is a vital structure that is encountered during posterior approaches to the acetabulum. Due to proximity of sciatic nerve and its branches to the posterior part of acetabulum, fractures and dislocations in this area have very high incidence of sciatic nerve injury. Most common to be involved is the peroneal division

The classification and subsequent treatment of acetabular fractures are based on imaging studies that have been derived from a thorough understanding of the

**Figure 5.** *Corona mortis artery.*

*Surgical Anatomy of Acetabulum and Biomechanics DOI: http://dx.doi.org/10.5772/intechopen.92330*

*Essentials in Hip and Ankle*

**2.4 Neurologic anatomy**

lumbar plexus.

[19–21].

mortis is the anomalous connection between epigastric and obturator vessels. It can cause fatal bleeding if not identified and ligated during surgery [17, 18] (**Figure 5**).

*The Lumbar plexus* consists of the first three lumbar anterior rami and a portion of the anterior ramus of the fourth lumbar nerve. There are also short collateral rami, which include the hypogastric, ilioinguinal, genitofemoral, and lateral femoral cutaneous nerve. Femoral and obturator nerves are the terminal rami of

*The obturator nerve* receives contributions from the L2, L3, and L4 trunks. It continues into the pelvis underneath the iliopectineal line, reaches the obturator

*The femoral nerve* receives contributions from the L2, L3, and L4 trunks

There are two important plexus: lumbar plexus and sacral plexus.

orifice. It exits the pelvis together with the obturator vessels.

**8**

**Figure 5.**

*Corona mortis artery.*

*The Sacral Plexus* is formed by the coalescence of the lumbosacral trunk (L5 anterior ramus with L4 anastomotic ramus) and the anterior rami of the first four sacral roots. The plexus ultimately becomes the sciatic nerve (posterior tibial and peroneal nerve). The posterior branches relevant to orthopedic surgery are the superior gluteal nerve, branches to the external rotators and inferior gluteal nerve. The sciatic nerve exits the greater sciatic notch. In 85% of the cases, it courses in front of the piriformis. The other variants include penetration and splitting around the muscle. After exiting through greater sciatic notch, it courses behind the obturator internus, under the gluteal sling to enter the thigh. The sciatic nerve is a vital structure that is encountered during posterior approaches to the acetabulum. Due to proximity of sciatic nerve and its branches to the posterior part of acetabulum, fractures and dislocations in this area have very high incidence of sciatic nerve injury. Most common to be involved is the peroneal division of sciatic nerve [21, 22] (**Figure 6**).
