gms | German Medical Science

Objective: Neuological deficits from lumbar plexus nerve injuries commonly occur in patients undergoing lateral approaches. However, it is not yet clear what types of injury occur, where anatomically they are located, or what mechanism causes them. We aimed to study (a) the topographic anatomy of lumbar plexus nerves and their injuries in human cadavers after lateral transpsoas approaches to the lumbar spine, (b) the structural morphology of those injuries, (c) the topographic anatomy of the lumbar plexus throughout the mediolateral approach corridor.

Methods: Fifteen adult fresh frozen cadaveric torsos (26 sides) underwent lateral approaches (L1-L5) by experienced lateral spine surgeons. The cadavers were subsequently opened and the entire plexus dissected and examined for nerve injuries. The topographic anatomy of the lumbar plexus and its branches, their injuries and the morphology of these injuries were documented.

Results: Fifteen injuries were found with complete or partial nerve transections (Sunderland IV and V). Injuries were found throughout the mediolateral approach corridor. At L1/2, the iliohypogastric, ilioinguinal and subcostal nerves were injured within the psoas major muscle, the retroperitoneal space, or the outer abdominal muscles and subcutaneous tissues. Genitofemoral nerve injuries were found in the retroperitoneal space. Nerve root injuries occurred within the retroperitoneal space and psoas muscle. Femoral nerve injuries were only found within the psoas major muscle. No obturator nerve injuries occurred.

The authores introduced a novel anatomical description of medio lateral zones which facilitates understanding where plexus nerves can be encoutered during lateral approaches.

Conclusion: Lateral approaches can lead to structural nerve damage caused by crush injuries. Knowledge of the complex plexus anatomy, specifically its mediolateral course, is critical in order to avoid approach related injuries.