Extensor Pollicis et Indicis Accessorius: A Case Report and Description

Authors' Affiliations

Priyanka Avasarala, Edward Via College of Osteopathic Medicine, Blacksburg, VA. S. Grant Carter, Edward Via College of Osteopathic Medicine, Blacksburg, VA. Lilleen Rochelle Franck, Edward Via College of Osteopathic Medicine, Blacksburg, VA. Sara Karami, Edward Via College of Osteopathic Medicine, Blacksburg, VA. Amber Miller, Edward Via College of Osteopathic Medicine, Blacksburg, VA. Chaandini Pandeti, Edward Via College of Osteopathic Medicine, Blacksburg, VA. Breanna Wakeling, Edward Via College of Osteopathic Medicine, Blacksburg, VA.

Location

D.P. Culp Center Ballroom

Start Date

4-5-2024 9:00 AM

End Date

4-5-2024 11:30 AM

Poster Number

100

Name of Project's Faculty Sponsor

Jonathan Millard

Faculty Sponsor's Department

Biomedical Sciences

Classification of First Author

Clinical Doctoral Student

Competition Type

Competitive

Type

Poster Presentation

Presentation Category

Health

Abstract or Artist's Statement

INTRODUCTION: Embryological development of the forearm extensors can be divided into three parts: radial, superficial, and deep. The deep component is known by the literature to include many variations, most of which involve the extensors of digits 2-5. The first digit, also a part of the deep compartment, has markedly less documented variation. Here we present an exceedingly rare accessory tendon derived from the posterior forearm musculature. METHODS: An accessory extensor indicis tendinous attachment to the extensor pollicis longus tendon was identified during a routine dissection of the hand in an 88-year-old female formalin-fixed whole-body donor. Further dissection revealed a unique muscle belly sharing an origin with the extensor indicis muscle. The accessory muscle’s tendon bifurcated, with one short substantial tendon inserting into the extensor pollicis longus tendon and a second tendon becoming confluent with the radial side of the extensor expansion of the second digit. The tendon inserting into the extensor pollicis longus tendon was 3.62 mm wide. Though varying in dimensions along their course, at one point immediately proximal to the metacarpophalangeal joint, the accessory tendon was wider than the proper extensor indicis tendon (3.81 mm vs. 3.79 mm, respectively). RESULTS/CONCLUSIONS: Redundancy in extensor tendons of the forearm musculature is not uncommon; however, involvement of the pollical extensor is relatively infrequent, with prevalence reports less than 1%. The accessory muscle belly’s size suggests it would have significant biomechanical influence on digits 1 and 2, likely offering unusually strong antagonistic resistance to thumb flexion, abduction, and opposition. Finally, the aberrant tendinous connection to the extensor pollicis longus tendon coursed conspicuously over the substance of the first dorsal interosseous muscle. This anomaly may interfere with decompression approaches to chronic first dorsal interosseous compartment syndrome or the outcomes of tendon transfer procedures. Knowledge of this variable anatomy may inform procedure planning and enhance clinical outcomes.

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Apr 5th, 9:00 AM Apr 5th, 11:30 AM

Extensor Pollicis et Indicis Accessorius: A Case Report and Description

D.P. Culp Center Ballroom

INTRODUCTION: Embryological development of the forearm extensors can be divided into three parts: radial, superficial, and deep. The deep component is known by the literature to include many variations, most of which involve the extensors of digits 2-5. The first digit, also a part of the deep compartment, has markedly less documented variation. Here we present an exceedingly rare accessory tendon derived from the posterior forearm musculature. METHODS: An accessory extensor indicis tendinous attachment to the extensor pollicis longus tendon was identified during a routine dissection of the hand in an 88-year-old female formalin-fixed whole-body donor. Further dissection revealed a unique muscle belly sharing an origin with the extensor indicis muscle. The accessory muscle’s tendon bifurcated, with one short substantial tendon inserting into the extensor pollicis longus tendon and a second tendon becoming confluent with the radial side of the extensor expansion of the second digit. The tendon inserting into the extensor pollicis longus tendon was 3.62 mm wide. Though varying in dimensions along their course, at one point immediately proximal to the metacarpophalangeal joint, the accessory tendon was wider than the proper extensor indicis tendon (3.81 mm vs. 3.79 mm, respectively). RESULTS/CONCLUSIONS: Redundancy in extensor tendons of the forearm musculature is not uncommon; however, involvement of the pollical extensor is relatively infrequent, with prevalence reports less than 1%. The accessory muscle belly’s size suggests it would have significant biomechanical influence on digits 1 and 2, likely offering unusually strong antagonistic resistance to thumb flexion, abduction, and opposition. Finally, the aberrant tendinous connection to the extensor pollicis longus tendon coursed conspicuously over the substance of the first dorsal interosseous muscle. This anomaly may interfere with decompression approaches to chronic first dorsal interosseous compartment syndrome or the outcomes of tendon transfer procedures. Knowledge of this variable anatomy may inform procedure planning and enhance clinical outcomes.