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Posterior interosseous nerve (PIN) syndrome is a specific type of radial nerve entrapment neuropathy.
The posterior
interosseous nerve (PIN) is a branch of the radial nerve that primarily
provides motor innervation to the extensor muscles of the forearm.
PINS is characterized by weakness or paralysis of these muscles, leading to difficulty in extending the fingers and thumb, while wrist extension remains intact due to the preservation of the extensor carpi radialis longus and brevis muscles [Dang & Rodner, 2009; Wegiel et al, 2023; Baumer et al, 2016].
Posterior interosseous nerve syndrome (PINS) is characterized by motor deficits without sensory loss.
The primary symptom is weakness or paralysis of the extensor muscles of
the forearm, leading to difficulty in extending the fingers and thumb.
Wrist extension is usually preserved, but there may be radial deviation
due to the intact function of the extensor carpi radialis longus and
brevis muscles.
Patients may also report pain in the forearm, particularly around the elbow, which can precede the onset of motor symptoms [Kim et al, 2021; Sigamoney et al, 2017; Akane et al, 2016].
Initial treatment includes rest, activity modification, and splinting to reduce nerve irritation.
Medications: Nonsteroidal anti-inflammatory drugs (NSAIDs) and corticosteroids can help reduce inflammation and pain. Neuropathic pain may be managed with medications such as pregabalin, carbamazepine, or duloxetine [Chrestian, 2020; Kim et al, 2021].
Occupational Therapy: This can help patients adapt to functional limitations and improve their ability to perform activities of daily living (ADLs) [Chrestian, 2020; Kim et al, 2021].
Injections: Several types of injections are available for treating radial neuritis and posterior interosseous nerve syndrome (PINS), each with distinct mechanisms of action and potential benefits:
Corticosteroid Injections: These are commonly used to reduce inflammation and pain. Corticosteroids inhibit inflammatory cytokines and reduce nerve swelling, which can alleviate compression and improve symptoms. They are often used in combination with local anesthetics for immediate pain relief [Buntragulpoontawee et al, 2020; Norbury & Nazarian, 2019].
Hydrodissection: Normal saline or local anesthetics can mechanically separate the nerve from surrounding tissues, reducing compression. This technique is often combined with other injectates like corticosteroids, prolotherapy or biologic injections to enhance therapeutic effects [Buntragulpoontawee et al, 2020; Norbury & Nazarian, 2019].
Prolotherapy Perineural Injection Therapy with 5% Dextrose (D5W): Perineural injection with D5W is an emerging therapy for entrapment neuropathies. Dextrose is thought to reduce neurogenic inflammation and promote tissue healing. Studies have shown that D5W injections can provide significant pain relief and functional improvement in peripheral nerve entrapments. Ultrasound-guided perineural injection with dextrose (5% dextrose) has been reported to improve sensory and motor functions in cases of radial nerve palsy [Buntragulpoontawee et al, 2020; Chen et al, 2018; Azizi et al, 2025].
Platelet-Rich Plasma (PRP): PRP injections involve using a concentration of the patient's own platelets to promote healing. PRP contains growth factors that can enhance tissue repair and reduce inflammation. It has shown favorable outcomes in treating entrapment neuropathies, including improved pain and function [Buntragulpoontawee et al, 2020].