Extensor Carpi Ulnaris

Original Editor - Rania Nasr Top Contributors - Rania Nasr, Kim Jackson, Nikhil Benhur Abburi, Wanda van Niekerk, Aya Alhindi and Alicia Fernandes

Description

The extensor carpi ulnaris muscle is one of the extensor muscles of the forearm located in the superficial layer of the posterior compartment of the forearm.  It shares this compartment with the brachioradialis, the extensor carpi radialis longus, the extensor carpi radialis brevis, the extensor digitorum, and the extensor digiti minimi. All of these muscles share a common origin on the lateral epicondyle via the common extensor tendon.  As all of these muscles near their distal insertion sites, they are secured by the extensor retinaculum.

Origin

The extensor carpi ulnaris muscle originates from the lateral epicondyle of the distal humerus and the posterior aspect of the ulna.

Insertion

It inserts onto the dorsal base of the fifth metacarpal after passing through the sixth compartment of the extensor retinaculum.

Nerve

The posterior interosseous nerve, which is a motor branch of the radial nerve.The radial nerve arises from the brachial plexus by way of the posterior cord which has contributions from the spinal nerve roots of C5 to T1.

Artery

• The ulnar artery, which branches off of the brachial artery near the antecubital fossa and supplies the medial aspect of the forearm.
• The posterior interosseous artery, a posterior branch of the radial artery, that runs between the superficial and deep extensor muscle groups and supplies them both.

Lymphatics

• The lymphatic drainage of the upper limb consists of both superficial and deep lymphatic vessels.
• The deltopectoral lymph nodes are another potential drainage site.

Function

The extensor carpi ulnaris (ECU) plays a pivotal role in wrist and forearm function, contributing to both extension and adduction of the hand at the wrist, while also providing essential medial stability.

• Extension and Adduction

• Medial Stability- Apart from its role in movement, the ECU significantly contributes to the medial stability of the wrist, aiding in the prevention of excessive lateral deviation

• Fiber Origin: The ECU is characterized by its unique fiber origin, deriving from both the distal humerus as part of the common extensor tendon and the proximal ulna

  This comprehensive understanding of the ECU's function, encompassing its involvement in wrist movement and stability, is vital for physiotherapists in formulating effective rehabilitation strategies for patients with wrist and forearm injuries.

Clinical Relevance

The extensor carpi ulnaris (ECU) holds considerable clinical relevance in the context of wrist and forearm function, susceptibility to injuries, and the manifestation of related conditions.

Contribution to Wrist Function:

The ECU is a key contributor to the extension and adduction of the wrist, playing a crucial role in various activities involving these movements

Common Injuries in Athletes:

Athletes engaged in activities requiring forceful wrist movements are particularly prone to ECU injuries. These injuries may result from repetitive stress on the tendon during activities such as gripping, throwing, or racket sports

Tenosynovitis:

Repetitive flexion and extension of the wrist can lead to tenosynovitis, characterized by inflammation of the tendon and its sheath. This condition arises due to the constant irritation of the ECU tendon, impacting its smooth movement within the sheath

Tendinopathy:

   Overuse of the ECU may result in tendinopathy, marked by thickening and painful stiffness of the tendon. Importantly, this condition may occur with minimal structural damage, highlighting the significance of early intervention and management

Structural Damage and Partial Tear:

   Prolonged and excessive stress on the ECU tendon can lead to structural damage, potentially culminating in a partial tear. This underscores the importance of addressing overuse and providing appropriate rehabilitation to prevent further complications.

   Understanding the clinical implications of ECU injuries enables physiotherapists to tailor interventions for optimal patient outcomes, emphasizing the importance of early diagnosis and targeted rehabilitation.

Assessment

Ask the patient to pronate their forearms and extend their fingers. Place your hand along the hand's medial border to resist movement. The extended wrist is adducted against resistance. The muscle can be seen and felt in the proximal part of the forearm, and its tendon can be palpated proximal to the head of the ulna if it is working properly.

Clinical Significance

• An accurate clinical history and assessment is essential for diagnosis of ECU tendon disorders. The timing of onset of symptoms discriminates between acute and chronic causes.
• Mechanical symptoms at the moment of onset are also common descriptors in this condition. Patients will use words such as ‘snap’, ‘pop’ or ‘tear’ in an acute sheath disruption. In some cases, episodes of tendon subluxation are excruciatingly painful.
• In others the subluxation may be entirely asymptomatic and may be easily reproduced by the patient. Palpation along the length of the ECU tendon (starting distally at its insertion into the base of the fifth metacarpal to ensure palpation of the correct structure) will reveal tenderness accurately localised to that structure.
• Pain on resisted active extension with ulnar deviation is pathognomonic of an ECU condition. Weakness is frequently associated with pain. Painless weakness is likely to represent a complete rupture of the ECU tendon.
• In equivocal or difficult cases, ultrasound (US) or MRI are the imaging modalities of choice to supplement the clinical diagnosis of ECU tendinopathy and instability. Conventional X-rays are not routinely required.

Treatment

Treatment Strategies for ECU Tendinosis and Tendinopathy aim to address ECU tendinosis and tendinopathy at various stages, providing a comprehensive approach to manage symptoms and promote recovery

Acute Tendinosis

Acute tendinosis of the ECU typically responds well to non-operative measures:

• Rest: Allowing the affected wrist to rest to promote healing.
• Activity Modification: Adjusting activities to reduce strain on the ECU tendon.
• Splintage: Immobilization in a short-arm plaster cast, positioned at 30° wrist extension and ulnar deviation, for approximately three weeks

Rehabilitation for Early Reactive Phase

For the early reactive phase of tendinopathy:

• Load Management: Gradual reintroduction of load through controlled exercises.
•  Isometric Exercises:Engaging in exercises that involve muscle contraction without joint movement, helping to manage pain over 5–10 days.
• Pharmacological Support:Consideration of ibuprofen as an adjunct for its anti-inflammatory properties during this phase

Chronic Tendinopathy:

In cases of chronic tendinopathy without a sudden increase in pain:

Load Management: Ongoing management to control and distribute load.

Eccentric Work: Incorporation of eccentric exercises to address tendon strength and resilience.

Isometrics and Strength Exercises: Further rehabilitation focusing on improving strength and function.

Injection of Steroids:If symptoms persist despite non-operative measures, consideration may be given to an injection of steroids into the fibro-osseous sheath. This intervention aims to alleviate inflammation and pain, especially when other conservative methods have not provided relief