What do lab results tell us about the axillary arch in clinical practice?

The axillary arch (AA) muscle is one of the most frequently studied human anatomical variants. It is believed to be an epigenetic remnant of the panniculus carnosus between muscle fascia and subcutaneous adipose tissue.
Although anatomical descriptions of this anomaly are diffuse, most of the evidence emerged from accidental findings in single case studies. Without medical imaging clinical detection is difficult and during routine clinical palpation the AA may be confused with enlarged lymph nodes or soft tissue masses. Moreover, it has also been shown to frequently occur as a fibrous band.
Due to its position overlying the neurovascular bundle the AA may possibly impinge each of the axillary structures provoking different clinical symptoms, including TOS, shoulder instability, axillary vein thrombosis or upper limb lymphedema. On the other hand, the AA has been linked to enhanced upper limb performance, muscle power and proprioception in athletic subjects.
Most of the clinical trials reported in literature involve symptom-free subjects questioning the applicability of the results for use in daily routine practice. Since contradictory findings regarding the clinical significance of the AA have been reported and given the fact that there are no reports of the anomaly causing neurological compression, its role in the development of symptoms remains unclear.
Summarized, scientific and clinical evidence regarding the management of symptomatic subjects with an AA is lacking. Reports revealing the role of the AA relative to signs and symptoms of patients are warranted.