The Forgotten Lumbocostal Ligament: Anatomical Study with Application to Thoracolumbar Surgery.

INTRODUCTION: Most ligaments of the human body have been well studied. However, the lumbocostal ligament has received little attention in the extant medical literature and, to our knowledge, has not undergone anatomical study. Therefore, the present study was performed to better characterize this structure's anatomy and relationships.

METHODS: In the prone position, 10 adult cadavers underwent dissection of their lumbocostal ligaments. All specimens were unembalmed and had no history of surgery to the spine. The lumbocostal ligament was dissected and measurements made using calipers and a ruler. This ligament's attachments were determined as well as its relationships to surrounding fasciae, muscle, and nerves.

RESULTS: A lumbocostal ligament was identified on all sides. The ligament was posterior to the quadratus lumborum muscle on all sides. The mean length of the ligament was 3 cm. The overall shape of the ligaments ranged from short bands to large rhomboidal sheets. Inferiorly, the lumbocostal ligament blended with the middle layer of the thoracolumbar fascia on all sides. The ligament attached to the transverse processes of L1 on 25% of sides and onto the transverse processes of L1 and L2 on 75% of sides. The ligament became taut with rib elevation and was lax with rib depression.

CONCLUSIONS: The lumbocostal ligament is a constant structure of the thoracolumbar junction. Appreciation of this ligament can help localize the transverse processes of L1 and L2 and adjacent nerves, such as the regional dorsal rami as they exit near its attachment onto the lumbar transverse processes.