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  • Updated 08.09.2021
  • Released 03.21.2002
  • Expires For CME 08.09.2024

Lumbosacral plexus injuries



Neurologic signs of lumbosacral plexus injuries consist of motor deficit with flaccid paralysis associated with sensory deficits to all types of stimulation in the territory of the damaged nerve roots: a lower motor neuron paralysis. Nonstructural causes include radiation therapy, diabetes, vasculitis, and perivasculitis. Traumatic causes are mainly due to fractures of the pelvic ring or acetabulum and hip joint replacements. In this article, the authors provide a systemic review of lumbosacral plexus injuries from the published literature. They have included background information about the historical notes, clinical manifestations, etiology, epidemiology, pathogenesis and pathophysiology, prevention, differential diagnosis, diagnostic work-up, prognosis and complications, and management. In this update, the authors added discussion of the preventive measures that can be considered during spine surgery to lower the risk of lumbar plexus injury.

Key points

• Symptoms of lumbosacral plexus injury include varying degrees of lower extremity weakness, sensation changes, pain, and diminished reflexes.

• Most lumbosacral plexopathies due to trauma are from very violent injuries, such as automobile-pedestrian accidents, high-speed car accidents, or falls from heights, and are often associated with damage to internal organs, blood vessels, and bony structures, especially the pelvic ring.

• CT for evaluation of bony injuries, MRI, and EMG/NCS are important diagnostic tools.

• Because most traumatic plexopathies improve spontaneously, at least to some extent, they usually are treated conservatively, but when surgical repair is attempted, it tends to yield better results.

Historical note and terminology

Involvement of the lumbosacral plexus appears in history in its congenital form, most often described as myelomeningocele. Hippocrates and Arabic physicians described this condition with its devastating clinical problems. Aristotle proposed infanticide to resolve this social problem. Even with modern technological advances, lumbosacral plexus injury is not easy to describe. Books on the subject of trauma make only a brief mention of this entity (22).

The lumbosacral plexus comprises 2 distinct portions: the lumbar plexus and the sacral plexus, each innervating a different part of the lower limb. The lumbar plexus connects with the sacral plexus via the lumbosacral cord. The lumbar plexus is formed by the ventral primary rami of L1-3 with contributions from the ventral rami of L4 and T12, which separates into anterior and posterior divisions. The lumbosacral plexus sends muscular branches to the quadratus lumburom (T12, L1-4), psoas minor (L1), psoas major (L2-3[4]), and iliacus (L2-3). The anterior rami (L2-4) form the obturator nerve that innervates the adductor muscles of the thigh and the skin of the medial thigh. The posterior rami (L2-4) form the femoral nerve, which innervates the quadriceps femoris muscle, the anterior thigh, and the medial side of the leg via medial and intermediate cutaneous nerves of the thigh and saphenous nerves, respectively. The predominantly sensory iliohypogastric (L1), ilioinguinal (L1), genitofemoral (L1-2), and lateral cutaneous nerve of the thigh (L2-3) also arise from lumbar plexus. The caudally located sacral plexus is formed by the lumbosacral cord (L4-5) and the ventral rami of S1-3 and part of S4. The main branch is the sciatic nerve (L4-5, S1-3), and its 3 main branches (the peroneal, tibial, and sural nerves) supply the hamstring muscles, all the muscles below the knee, and all the skin below the knee except the area supplied by the saphenous nerve. The superior gluteal nerve (L4-5, S1; innervates the gluteus medius and minimus), inferior gluteal nerve (L5, S1-2; innervates gluteus maximus), and the nerve to piriformis (S1-2) directly arise from the sacral plexus. The posterior femoral cutaneous (S1-3) and pudendal (S2-4) nerves also arise from sacral plexus.

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