Ossification of the mamillo-accessory ligament: a review of the literature and clinical considerations.

Anat Cell Biol. 2019 Jun;52(2):115-119. doi: 10.5115/acb.2019.52.2.115. Epub 2019 Jun 30.

Dupont G, Yilmaz E, Iwanaga J, Oskouian RJ, Tubbs RS.

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Abstract

Ossification of the mamillo-accessory ligament (MAL) is a misunderstood phenomenon; however, many have posited that it can result in nerve entrapment of the medial branch of the dorsal ramus causing zygapophyseal joint related low back pain. The MAL has been studied anatomically by few, yet the data indicate possible associations between ossification of this ligament and spondylosis. It has been proposed that mechanical stress upon the lumbar spine may also lead to progressive ossification of the MAL into a bony foramen.

KEYWORDS:

Anatomy; Low back pain; Lumbar; Mamillo-accessory ligament; Medial branch block; Ossification

Fig. 1

Posterior view of the lumbar spine focused on L2 vertebra. Note on the left side of the figure, the normal positions of the mamillary (orange arrow) and accessory (white arrow) tubercles. On the right side of the figure, an ossified mamillo-accessory ligament is seen (yellow arrow) resulting in a bony foramen (i.e., the mamillo-accessory foramen) for the potential transit of the medial branch of the dorsal ramus.

Fig. 2

Schematic drawing of the dorsal rami (yellow) of the lumbar region and their relationships to the vertebrae. Note the spinal nerve (blue) as it leaves the intervertebral foramen and the medial (mb), lateral (lb), and intermediate (ib) branches of the dorsal rami. Also note the medial branches, which are susceptible to compression by an ossified mamillo-accessory ligament traveling to the facet joints (FJ). The space for the mamillo-accessory foramen is designated by the dashed circle (maf ) with the enclosed medial branch of the dorsal ramus.