A lumbar vertebra with the presence of the mamillo-accessory ligament (MAL) bridging between the mammillary and accessory processes.
Note that this is a posterolateral view and thus the MAL appears horizontal, which may be misleading. The MAL, in fact, runs on an vertical oblique axis.
Case Discussion
The mamillo-accessory ligament (MAL) is a fibrous band of connective tissue that forms a bridge between the mammillary and the accessory processes of lumbar vertebrae. Due to the connection the MAL provides between two features of the same bone, it is often considered a "fake" ligament. Although there is no definitive evidence that the MAL has a biomechanical role, its architecture is often used to create an osseofibrous tunnel known as the mamillo-accessory foramen, that the medial branch of the dorsal rami (MBDR) can pass deep to. This tunnel is thought to maintain the trajectory of the MBDR in close proximity to the associated vertebra. This relationship may provide easy anatomical access to the MBDR for denervation procedures such as those done in radiofrequency ablation. However, the MAL can also become ossified in some lumbar regions, rendering MBDR denervation more anatomically challenging and less efficient.
It has also been hypothesized that the MAL may contribute to some cases of low back pain due to entrapment of the MBDR under the MAL.
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