Re: Wright H, Fahmy M, Bourke G. An accessory muscle as the possible cause of ulnar nerve compression proximal to the cubital canal: a case report. J Hand Surg Eur. 2021, 46: 1114–5

Abstract

I read this article with interest. The authors described a case of an accessory muscle as a possible cause of ulnar nerve compression proximal to the cubital canal. However, I would like to make my modest comments about the reported accessory muscle. The authors correctly point out that this muscle does not have the anatomical features of the anconeus epitrochlearis muscle and was more proximal in location. However, I think that when the authors accept a variant muscle as a possible cause of nerve compression, they need to be clearer and should make a proposal about the possible name of the muscular variation or explain to which muscle it belongs. As pointed out by Georgiev et al. (2017), the lack of knowledge of the variant muscle discovered at surgical intervention could be (1) scarcely presented clinical reports, (2) rarity of the reported structure and (3) limited approach during decompression surgery. I would like to add another cause: a limited knowledge about anatomical variations. According to me, when accepting a variant muscle, three important things should be born in mind: (1) location, (2) insertions and (3) function. In the article of Wright et al. (2021) the approach is not limited and gives wide visualization of the muscular variant and the authors could clearly determine it. In my opinion, it could be speculated that the possible cause of ulnar nerve compression in the reported case is accessory slip from the triceps brachii muscle. Accessory slip from triceps brachii, although rare, is clearly described in the work of Swamy et al. (2013). Moreover, a clinical case of ulnar nerve compression by additional slips of the triceps brachii has also been described by Kim et al. (2016). In conclusion, I think that when considering variant muscle entrapment neuropathy, the authors should make a proposal about the muscle to which it belongs, rather than only report an accessory muscle. Anatomy is a very old science, and precise knowledge of different anatomical variations is mandatory for experienced surgeons.