Functional anconeus free flap for thenar reconstruction: A cadaveric study

Background: Restoration of thumb opposition when significant thenar soft tissue defects occur remains a considerable surgical challenge. While several clinical applications of the anconeus muscle have been developed, free functioning muscle transfer (FFMT) of the anconeus for thenar reconstruction has not been reported previously. This study therefore sought to describe anatomical features of the anconeus that would determine its suitability for use as a FFMT. Methods: The anconeus, its corresponding abductor pollicis brevis (APB), and the supplying neurovasculature in eight white British cadaveric upper extremities were identified and dissected. Measurements were performed using standard calipers and ImageJ 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 anconeus were larger than those of the APB (anconeus/APB fiber length=88.0±9.9/57.7±9.0 mm, area=1,341.9±230.4/987.7±251.2 mm2). There was no significant difference between mean fiber angles (anconeus/APB=70.5±11.9°/78.4±12.2°; p>0.05) and neurovasculature (anconeus/APB: artery diameter=1.9±0.2/2.0±0.5 mm, nerve diameter=1.7±0.3/2.1±0.4 mm; p>0.05). The length (31.3±6.9 mm) and caliber (diameter=1.9±0.2 mm) of the vascular pedicle of the anconeus (recurrent posterior interosseous artery) and its venae comitans (diameter=1.0 mm) are sufficient for microsurgical anastomosis. Conclusions: The anatomic rationale of the anconeus FFMT for thenar reconstruction is sound and, compared to other FFMTs, may provide several advantages: reliable and matching anatomy, minimal donor site morbidity, and the potential to restore a greater degree of opposition and thus function in a one-stage procedure.