Flexor Pollicis Longus Palsy Following Both-Bone Forearm Fracture Fixation: A Case-Based and Cadaveric Evaluation

Area of Science:

• Orthopedic Surgery
• Neuroscience
• Anatomy

Background:

• Flexor pollicis longus (FPL) palsy is an uncommon complication following both-bone forearm fractures (BBFF).
• Understanding the etiology and anatomical risks associated with FPL palsy is crucial for patient management.

Purpose of the Study:

• To investigate the incidence and characteristics of FPL palsy in patients with acute BBFF.
• To evaluate the anatomical relationship of the anterior interosseous nerve (AIN) branches to the radius via cadaveric dissection.

Main Methods:

• Retrospective review of 29 patients with acute BBFF treated surgically (2005-2023).
• Analysis of injury and surgical factors in patients with documented FPL palsy.
• Cadaveric dissection of 10 forearms to map AIN branching patterns relative to the lateral epicondyle.

Main Results:

• Five patients (17%) presented with FPL palsy, either pre-operatively (n=2) or post-operatively (n=3).
• All affected patients had midshaft radial fractures; all palsies resolved spontaneously within an average of 33 days.
• Cadaveric dissections showed the FPL motor branch originates consistently distal to the radial head, with minimum distances from the lateral epicondyle established.

Conclusions:

• FPL palsy following BBFF can occur at injury or post-surgery, predominantly with midshaft radial fractures, likely representing neurapraxia.
• Cadaveric data suggest the FPL motor branch is vulnerable to injury from fracture fragments or surgical manipulation in the mid-to-proximal radius.