Basic Study
Copyright ©The Author(s) 2022. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Orthop. Nov 18, 2022; 13(11): 978-985
Published online Nov 18, 2022. doi: 10.5312/wjo.v13.i11.978
Anatomic relationship of extensor indicis propius and extensor digitorum communis: Implications for tendon transfer
Joanne Zhou, Christopher Frey, Nicole Segovia, Jeffrey Yao
Joanne Zhou, Christopher Frey, Nicole Segovia, Jeffrey Yao, Department of Orthopaedic Surgery, Stanford University Medical Center, Stanford University, Redwood city, CA 94063, United States
Author contributions: Zhou J contributed to study design, dissections, statistical analysis, and writing the manuscript; Frey C contributed to study design, dissections, statistical analysis, and writing the manuscript; Segovia N carried out statistical analyses and assisted with manuscript revisions; Yao J contributed to study design and manuscript revisions.
Institutional review board statement: This study was deemed exempt from Institutional Review Board Approval as only donated cadaveric specimens were used.
Informed consent statement: This study was deemed exempt from informed consent statement as only donated cadaveric specimens were used.
Conflict-of-interest statement: The authors have nothing to disclose.
Data sharing statement: The statistical methods of this study were reviewed by our research support center, and the statistical methods and techniques mentioned are appropriate for the research.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Joanne Zhou, MD, Staff Physician, Department of Orthopaedic Surgery, Stanford University Medical Center, Stanford University, 450 Broadway Street Pavilion A 2nd Fl MC 6120, Redwood City, CA 94603, United States. zhoujy@stanford.edu
Received: June 23, 2022
Peer-review started: June 23, 2022
First decision: August 22, 2022
Revised: September 6, 2022
Accepted: October 19, 2022
Article in press: October 19, 2022
Published online: November 18, 2022
ARTICLE HIGHLIGHTS
Research objectives

We sought to characterize the arrangement and circumference of the extensor indicis proprius (EIP) tendon with respect to the extensor digitorum communis tendon to the index finger (EDCI) at the level of the extensor retinaculum, where tendon harvest is often performed, and share our preferred technique for EIP to extensor pollicis longus (EPL) transfer.

Research methods

Twenty-nine fresh-frozen cadaveric forearms were dissected. Tendon circumference and relationship of the EIP and EDCI at the metacarpophalangeal (MCP) joint and the distal extensor retinaculum were recorded. Distance from the distal extensor retinaculum to the EIP myotendinous junction was measured.

Research results

EIP was ulnar to the EDCI in 96.5% of specimens (28/29) at the distal edge of the extensor retinaculum. In the remaining specimen, EIP was volar to EDCI. Tendon circumference at the distal extensor retinaculum averaged (9.3 mm ± 1.7 mm) for EDCI and 11.1 mm (± 2.7 mm) for EIP (P = 0.0010). The tendon circumference at the index MCP joint averaged 11.0 mm (± 1.7 mm) for EDCI and 10.6 mm (± 2.1 mm) for EIP (P = 0.33). EIP had a greater circumference in 76% (22/29) of specimens at the distal extensor retinaculum whereas EIP had a greater circumference in only 31% (9/29) of specimens at the MCP joint.

Research conclusions

The EIP tendon is frequently ulnar to and greater in circumference than the EDCI at the distal extensor retinaculum, suggesting a minimally invasive approach to tendon transfer using transverse incisions hidden in Langer's lines would be effective and safe.

Research perspectives

This research contributes to the body of knowledge on extensor tendon anatomy and facilitates the smaller incisions and dissection of EIP needed for tendon transfers.

Research motivation

Understanding the variability in anatomic relationships is important when harvesting EIP through a small incision. To our knowledge, no studies have examined the relationship and anatomy of the EIP and EDCI at the level of tendon harvest at the distal extensor retinaculum.

Research background

The EIP is a redundant extrinsic extensor of the index finger, commonly used in tendon transfer for EPL ruptures. Many variations of the course and arrangement of the tendons have been previously described. It is important to understand the arrangement and anatomy of the EIP tendon at the level of tendon harvest.