Review Question - QID 219587

Injury to the genitofemoral nerve, which lies at the midaxis of the L3-L4 disc space, is a known complication of a transpsoas approach. It commonly causes numbness in the skin of the medial thigh (Answer 2).

A variety of approaches are available for utilization during spinal surgery. The transpsoas (or extreme-lateral) approach has recently gained favor due to its minimally invasive nature, and the large size of the implants that can be introduced. Proponents of this technique also report lower postoperative pain for patients, shorter hospital stays and quicker return to normal activities. The downside of this, and other minimally invasive approaches, is that prolonged retraction is often required to navigate the smaller surgical fields. The genitofemoral nerve, which provides sensation to the skin in the groin and medial thigh, receives its innervation from L1-L2 and courses along the psoas muscle. The transpsoas approach risks both direct and indirect injury to this nerve, and patients with genitofemoral nerve injury often complain of medial thigh numbness or report a sensation of liquid trickling down his/her thigh.

Grunert et al. investigated injury to the lumbar plexus following lateral fusion procedures. Their study utilized 15 fresh-frozen adult cadavers. The authors noted that the utilization of retroperitoneal approaches (e.g., transpsoas) places the genitofemoral nerve at risk of injury, as it runs along the mid-axis of the lumbar spine from L2 to L5.

Mandelli et al. investigated nerve distortion following extreme-lateral interbody fusion procedures. Their study utilized nine fresh frozen cadavers. The authors found that the genitofemoral nerve could be both displaced and stretched by retractor blades.

Moller et al. investigated morbidity related to minimally invasive lateral interbody fusion procedures through a transpsoas approach. Their study included 53 patients with follow-up from 6 months to 3.5 years. Overall, 25% of patients reported postoperative thigh numbness, and 23% reported anterior thigh pain, with 69% and 75%, respectively, having improvement within 6 months. The authors conclude that genitofemoral nerve injury was most likely secondary to psoas muscle inflammation and/or stretch injury, and that major lumbar plexus injury is rare.

Figure A is a labeled diagram of neural anatomy around the lumbar spine. A is the ilioinguinal nerve, B is the iliohypogastric nerve, C is the genitofemoral nerve, D is the femoral nerve and E is the lateral femoral cutaneous nerve.

Incorrect Answers:
Answer 1: this would be consistent with injury to the ilioinguinal nerve.
Answer 3: this would be consistent with injury to the iliohypogastric nerve.
Answer 4: this would be consistent with injury to the superior hypogastric plexus.
Answer 5: this would be consistent with injury to the S1 nerve root.