An Anatomical Variation to Consider for a Safe Carpal Tunnel Surgery: Transverse Carpal Muscle

Area of Science:

• Anatomy
• Orthopedic Surgery
• Hand Surgery

Background:

• Carpal tunnel syndrome (CTS) is a common condition often treated surgically.
• Anatomical variations around the carpal tunnel can complicate surgical procedures.
• The transverse carpal muscle (TCM) is a less commonly discussed anatomical structure in this region.

Purpose of the Study:

• To determine the incidence of accessory transverse carpal muscle (TCM) occurrence.
• To assess the potential role of TCM in causing carpal tunnel syndrome (CTS).
• To highlight the importance of recognizing TCM variations during carpal tunnel release surgery.

Main Methods:

• Retrospective review of 62 carpal tunnel release surgeries performed between January 2007 and March 2021.
• Evaluation of the frequency and characteristics of transverse carpal muscle (TCM) occurrence.
• Documentation of patient demographics and hand laterality for identified variations.

Main Results:

• An incidence of 4.8% (3 out of 62 cases) for accessory TCM was observed.
• All identified accessory TCMs were located superficial to the transverse carpal ligament (TCL).
• The variations were exclusively found in left hands, with a 2:1 female-to-male ratio among affected patients.

Conclusions:

• Current evidence is insufficient to establish a causal link between TCM and CTS.
• Cadaveric dissections are recommended to further investigate the origin and nature of these accessory muscles.
• Surgeons should maintain awareness of potential TCM variations, particularly during minimally invasive procedures, to prevent surgical disorientation.