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Introduction: Restoration of thumb opposition when significant thenar soft tissue defects occur remains a considerable surgical challenge. Increasing knowledge about its anatomy and advances in surgical technique have led to the development of several clinical applications of the anconeus muscle (AM) but free functioning muscle transfer (FFMT) of the AM for thenar reconstruction has not been reported due to equivocal anatomy. The purpose of this study is therefore to investigate the viability of the anconeus FFMT through cadaveric specimens.

Material and Methods: The AM, its corresponding thenar eminence (TE), and the supplying neurovasculature in eight white British cadaveric upper extremities were identified and dissected. Measurements were performed using standard callipers and Image J 1.45d for a quantitative description of muscle architecture and the neurovasculature involved in the operative planning of the anconeus FFMT.

Results: The mean measures of the AM (fibre length = 88.0 ± 9.9 mm, area = 1341.9 ± 230.4 mm²) were larger than those of the TE (fibre length = 57.7 ± 9.0 mm, area = 987.7 ± 251.2 mm²). The mean fibre angles were not statistically different (AM = 70.5 ± 11.9⁰, TE = 78.4 ± 12.2⁰; p > 0.05). There was no significant difference between mean measures of the neurovasculature of the AM (artery diameter = 1.9 ± 0.2 mm, nerve diameter = 1.7 ± 0.3 mm) and TE (artery diameter = 2.0 ± 0.5 mm, nerve diameter = 2.1 ± 0.4 mm; p > 0.05). The length (31.3 ± 6.9 mm) and calibre (diameter = 1.9 ± 0.2 mm) of the AM artery (recurrent posterior interosseous artery) and its accompanying venae comitantes (diameter = 1.0 mm) are sufficient for microsurgical anastomosis.

Conclusions: The anatomic rationale of the anconeus FFMT is sound and compared to other FFMTs for the reconstruction of thenar defects, it offers the advantages of a reliable and consistent anatomy for easy harvest, minimal donor site morbidity, and most importantly, the potential to restore a greater degree of opposition and thus function in a one-stage procedure due in part to the unique orientation of the muscle fibres of the AM.