The sciatic nerve is the largest nerve in the body, coursing from the lower spine to the legs. It is the main highway for conveying motor and sensory information to and from each of the lower limbs. Due to its large size and expanse throughout the lower limbs, it is easily damaged. Any transection of the nerve, either partial or complete, usually results in profound functional loss.
Sciatic Nerve Path
Each sciatic nerve exits the spinal column and passes through the pelvic region. The sciatic nerve then courses through the buttocks area and down the back of the legs. Each nerve then branches into two divisions behind the knee. Each of these branches continues down the legs, and subdivides further in the lower legs.
Sciatic Nerve Function
Each sciatic nerve carries sensory information from the feet and legs to the spinal cord. This information eventually travels to the brain. Therefore, sensations such as pain and touch in the lower limbs, as well as information about position of the lower limbs, are all transmitted by this nerve. When movements are commanded by the brain, each motor signal travels down the spinal cord and into the sciatic nerve. The motor signals are then carried to individual muscles to initiate movement.
Mechanisms of Injury
Complete transection of the sciatic nerve is rare. It can occur with erosion against surgically installed metal hardware as well as with compound fracture of the femur. Incomplete transection is more common, and the largest contributors are penetration injuries such as might occur with a knife or bullet, and complications of bone fractures. Sometimes, during surgery, particularly during total hip replacement, the sciatic nerve can be inadvertently partially transected. Once part or all of the sciatic nerve is transected, there will be partial or complete loss of sensation and motor activity in the legs or feet.
Surgical Treatment
Complete or partial transection of the sciatic nerve is serious and must be surgically corrected immediately to prevent permanent functional loss. The surgeon will identify individual bundles of transected nerve fibers which make up the sciatic nerve. The surgeon will then rejoin the bundles by bringing their nerve sheaths together and suturing them so that there are no gaps in the fiber bundles. Sometimes a nerve graft can be used to help bridge any gaps in the nerve. Also, special conduits can be applied to guide the regenerating nerve in order to speed the healing process.
Regeneration and Rehabilitation
Most peripheral nerves like the sciatic nerve have the ability to regenerate after injury. Their regenerative success depends on several factors including the person's age, the lesion's distance from the spinal cord, the nature of the trauma and the presence of any preexisting illnesses. Rehabilitation of the lower limbs after sciatic nerve injuries helps the patient to recover function more completely. This is because certain rehabilitative techniques help the nervous system to reorganize and achieve certain functions. Specific strength and movement training can provide a return of function over time, where the rehabilitation process lasts from several weeks to two years.
References
- Sciatic Nerve: Everything about Sciatica: Sciatic Nerve Anatomy
- Medscape Today: Pathophysiology of Peripheral Nerve Injury
- Baylor Univ. Medical Center Proceedings: Considerations in nerve repair
- Ortho-Preferred: Nerve Repair
- "Clinical Neurosurgery"; Nerve Surgery: A Review and Insights about its Future; W. Sulaiman and D. Kline; 2006
