Variant Abductor Pollicis Longus Muscle: a Case Report

Area of Science:

• Anatomy
• Human Anatomy
• Surgical Anatomy

Background:

• The Abductor pollicis longus (APL) muscle displays variations in its attachments.
• Split insertions of the APL muscle are common in non-human primates like chimpanzees, gorillas, and gibbons.

Purpose of the Study:

• To describe a rare anomalous variation of the Abductor pollicis longus (APL) muscle.
• To investigate the origin, course, and insertion of this anomalous APL muscle.
• To discuss the potential biomechanical and clinical implications of this anatomical variation.

Main Methods:

• Anatomical observation of a cadaveric specimen.
• Detailed description of the anomalous APL muscle's origin, course, and insertion.
• Comparative anatomical considerations with existing literature.

Main Results:

• An anomalous APL muscle originated from the posterior surfaces of the radius and ulna.
• The muscle traversed deep to the extensor retinaculum.
• The tendon of the APL muscle reformed into a muscular belly before attaching to the base of the proximal phalanx, a highly unusual finding.

Conclusions:

• This reported variation of the APL muscle, with an attachment to the proximal phalanx, is a rare anatomical finding.
• Such anomalies can alter thumb abduction mechanics.
• Understanding this variation is clinically significant for reconstructive surgeries of the thumb and for anatomical research.