Anatomic relationship of extensor indicis propius and extensor digitorum communis: Implications for tendon transfer

Area of Science:

• Anatomy
• Orthopedic Surgery
• Hand Surgery

Background:

• The extensor indicis proprius (EIP) tendon is a common graft source for tendon transfers, particularly for extensor pollicis longus (EPL) reconstruction.
• Anatomical variations of the EIP tendon, such as splitting and arrangement differences, are well-documented.

Purpose of the Study:

• To precisely define the anatomy of the EIP tendon at the distal extensor retinaculum, a key site for tendon harvesting.
• To present a preferred surgical technique for transferring the EIP tendon to reconstruct the EPL tendon.

Main Methods:

• Dissection of 29 fresh-frozen cadaveric forearms without prior hand or forearm injury or surgery.
• Measurement of EIP and EDCI tendon circumference at the metacarpophalangeal (MCP) joint and distal extensor retinaculum.
• Recording the spatial relationship between EIP and EDCI tendons and measuring the distance from the retinaculum to the EIP myotendinous junction.

Main Results:

• The EIP tendon was located ulnar to the EDCI in 96.5% of specimens at the distal extensor retinaculum.
• Average tendon circumference was larger for EIP (11.1 mm) than EDCI (9.3 mm) at the distal extensor retinaculum (P=0.0010).
• EIP had a greater circumference than EDCI in 76% of specimens at the distal extensor retinaculum, but only 31% at the MCP joint.

Conclusions:

• The EIP tendon's frequent ulnar position and larger circumference relative to the EDCI at the distal extensor retinaculum are significant anatomical findings.
• These anatomical characteristics should be considered during tendon transfer procedures involving the EIP tendon, especially for EPL reconstruction.