From the Guidelines
The extensor pollicis brevis tendon appears to be either chronically torn or congenitally absent based on the imaging findings, and as such, no immediate intervention is required if the patient is asymptomatic, as most patients maintain adequate thumb function through compensatory mechanisms 1. This tendon normally extends the thumb at the metacarpophalangeal joint and contributes to thumb abduction. When this tendon is missing, patients may experience weakness in thumb extension, particularly at the metacarpophalangeal joint, though many patients remain asymptomatic due to compensation by other thumb extensors, particularly the extensor pollicis longus.
Key Considerations
- The distinction between congenital absence versus chronic tear is important for treatment planning but may be difficult to determine without clinical history of injury 1.
- Functional assessment of thumb extension and opposition should be performed to determine if intervention is necessary.
- For symptomatic patients, treatment options include physical therapy focusing on strengthening the remaining thumb extensors, splinting to provide support during activities, or in severe cases, surgical tendon transfer using the extensor indicis proprius.
- Ultrasound (US) may be useful in diagnosing abnormalities of the flexor and extensor tendons and tendon sheaths, including De Quervain disease, which affects the abductor pollicis longus and extensor pollicis brevis tendon compartment 1.
- MRI is ideal for evaluating tendon injuries and helping with surgical planning, particularly for flexor tendon injuries and injuries to the pulley system 1.
From the Research
Extensor Pollicis Brevis Tendon Absence
- The absence of the extensor pollicis brevis tendon can be congenital or due to chronic tear, as seen in cases of congenital clasped thumb deformity 2.
- Studies have reported variations in the anatomy of the extensor pollicis brevis tendon, including its absence or congenital hypoplasia 3, 4.
- The absence of the extensor pollicis brevis tendon can lead to difficulty in using the thumb, as reported in a case study of a 24-year-old man who presented with difficulty using his left thumb due to unilateral absence of the tendon 3.
Diagnosis and Treatment
- Ultrasound imaging can be used to assess the anatomy and excursion of the extensor pollicis brevis tendon, and can be useful in diagnosing its absence or variation 4, 5.
- Treatment for congenital clasped thumb deformity due to absence of the extensor pollicis brevis tendon may involve tendon transfer and reconstruction of the contracture in the first web space with z-plasty, as seen in a case report of a 4-year-old girl 2.
- Tendon transfer can also be recommended for patients with absence of the extensor pollicis brevis tendon, but may not always be accepted by the patient 3.
Anatomy and Variations
- The anatomy of the extensor pollicis brevis tendon can vary widely, with only 25% of tendons inserting in the conventional way into the base of the proximal phalanx 6.
- There may be ethnicity-related variations in the anatomy of the extensor pollicis brevis tendon, and further study into these variations may be indicated 4.
- The excursion of the extensor pollicis brevis tendon can be influenced by wrist position, with greatest excursion occurring in the neutral wrist position and least in flexion 5.