Ligaments of the Lumbar Spine

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The lumbar mamillo-accessory ligaments. Transverse process (tp), superior articular process (sap), mamillary process (mp), accessory process (sp), mamillo-accessory ligament (mal).

Dorsal aspect of the third lumbar vertebra showing a probed MAF on the left. mamillary process (MP), accessory process (AP), mamillo-accessory foramen (MAF), mamillo-accessory ligament (MAL).

There is a notch between the mamillary process and accessory process on each side of every lumbar vertebra. This notch is converted into a foramen by the mamillo-accessory ligament, through which the medial branch of the dorsal ramus passes through to supply the facet joint and multifidus. The ligament at any segment is related to the nerve of the next caudal segment (e.g. the L5 ligament is related to the L4 medial branch).

It is not a true ligament because it connects two points on the same bone. Its structure resembles a tendon more than a ligament and it has been interpreted as being a tendon of the semispinalis musculature in the lumbar spine. It is about 1-2mm thick.

The ligament can be ossified which converts the notch into a bony foramen, which is a normal phenomenon in a minority of people.

The structure has no biomechanical significance.

Further Reading

Media:bogduk1981 MAL.pdf