Struthers Ligament: Understanding Pain, Symptoms, Diagnosis, and Treatment

What is the pain of the Struthers ligament?

The pain associated with the Ligament of Struthers is not a direct pain from the ligament itself, but rather a set of symptoms resulting from the compression of the median nerve and/or the brachial artery as they pass beneath this fibrous band in the upper arm.

Understanding the Ligament of Struthers

The Ligament of Struthers is an anomalous fibrous band found in approximately 1-2% of the population. It represents an embryological remnant, typically extending from a bony projection known as the supracondylar process (a small spur on the medial aspect of the humerus, just above the elbow) down to the medial epicondyle of the humerus.

While a normal anatomical variation, its clinical significance arises when it becomes a source of compression for neurovascular structures. The median nerve and the brachial artery normally pass through the arm. In individuals with a Ligament of Struthers, these vital structures may pass underneath this ligament.

Pathophysiology: How Pain Arises

The presence of the Ligament of Struthers alone is often asymptomatic. Pain and other symptoms arise when the space beneath the ligament becomes constricted, leading to the entrapment or compression of the median nerve and/or, less commonly, the brachial artery.

This compression can be exacerbated by:

• Repetitive elbow flexion and extension: Activities involving repeated bending and straightening of the elbow can increase tension on the ligament, narrowing the sub-ligamentous space.
• Muscle hypertrophy: Enlargement of surrounding muscles, particularly the pronator teres, can contribute to the compressive forces.
• Direct trauma: Injury to the area can cause swelling or scarring, increasing pressure.

The median nerve is particularly vulnerable as it supplies sensation to parts of the hand and controls several forearm muscles involved in pronation and wrist/finger flexion. Compression here is distinct from more common entrapments like carpal tunnel syndrome, as it occurs much higher up in the arm.

Symptoms of Struthers Ligament Pain

Symptoms associated with Struthers ligament compression primarily involve the median nerve, though vascular symptoms can occur.

Neurological Symptoms (Median Nerve Compression):

• Pain: Often described as aching, burning, or throbbing pain along the medial aspect of the distal humerus and forearm, radiating towards the wrist and hand.
• Numbness and Tingling (Paresthesia): Typically felt in the median nerve distribution – the thumb, index finger, middle finger, and the radial half of the ring finger.
• Weakness: Difficulty with forearm pronation (turning the palm down), wrist flexion, and thumb opposition, often due to impaired function of muscles supplied by the median nerve (e.g., pronator teres, flexor pollicis longus, flexor digitorum profundus to digits 2 & 3).
• Exacerbation: Symptoms often worsen with activity, especially those involving repetitive elbow movements or sustained pronation.

Vascular Symptoms (Brachial Artery Compression - Less Common):

• Coldness or pallor: In the hand and fingers due to reduced blood flow.
• Claudication: Pain or cramping in the forearm with activity that resolves with rest.
• Diminished pulses: A weaker pulse in the radial or ulnar artery compared to the unaffected arm.

It is crucial to differentiate Struthers ligament syndrome from other conditions causing similar symptoms, such as carpal tunnel syndrome, pronator teres syndrome (which occurs more distally), cervical radiculopathy (nerve compression in the neck), or thoracic outlet syndrome.

Diagnosis

Diagnosing Struthers ligament syndrome requires a thorough clinical evaluation and often relies on a process of elimination due to its rarity.

Clinical Examination:

• Patient History: Detailed questioning about the onset, nature, location, and aggravating/alleviating factors of symptoms.
• Physical Examination:
  • Palpation: Tenderness may be elicited over the supracondylar process and the course of the ligament.
  • Provocative Tests: Specific maneuvers that reproduce symptoms, such as resisted elbow flexion with forearm pronation, or direct pressure over the ligament.
  • Sensory and Motor Testing: Assessment of median nerve distribution for sensory deficits and muscle weakness.
  • Vascular Assessment: Pulse checks and comparison with the unaffected limb.

Diagnostic Imaging:

• X-rays: Can identify the supracondylar process, which is often present but not always indicative of symptoms.
• MRI (Magnetic Resonance Imaging): Can help visualize the fibrous band and assess for median nerve edema or compression. It also helps rule out other pathologies.
• Ultrasound: Can be used to dynamically assess the median nerve and brachial artery as they pass under the ligament, especially during provocative maneuvers.

Neurophysiological Studies:

• Nerve Conduction Studies (NCS) and Electromyography (EMG): These are critical for confirming median nerve entrapment and localizing the site of compression. They measure the speed and strength of electrical signals in nerves and muscles.

Management and Treatment

Treatment for Struthers ligament syndrome typically begins with conservative approaches, with surgery reserved for cases that fail to respond.

Conservative Management:

• Rest and Activity Modification: Avoiding activities that exacerbate symptoms.
• Physical Therapy:
  • Nerve Glides/Mobilization: Gentle exercises to encourage nerve movement and reduce adhesion.
  • Stretching: Addressing any muscle tightness in the forearm and arm.
  • Strengthening: Improving strength in unaffected muscles to support function.
  • Manual Therapy: Soft tissue mobilization around the area.
• Pharmacological Intervention:
  • NSAIDs (Nonsteroidal Anti-inflammatory Drugs): To reduce pain and inflammation.
  • Corticosteroid Injections: Injections around the ligament can provide temporary relief and can also be diagnostic, confirming the source of symptoms.

Surgical Intervention:

• Indication: Surgery is considered when conservative measures fail to provide adequate relief, or in cases of progressive neurological deficit (e.g., worsening weakness, muscle atrophy).
• Procedure: The surgical procedure involves a decompression of the median nerve and brachial artery by releasing or excising the Ligament of Struthers and, if present, the supracondylar process. This is typically a straightforward procedure aimed at alleviating the compression.

Prognosis and Recovery

The prognosis for individuals with Struthers ligament syndrome is generally good, especially with timely and appropriate management.

• Conservative Treatment: Many patients experience significant improvement with non-surgical interventions, particularly if symptoms are mild and identified early.
• Surgical Treatment: Surgical decompression often leads to excellent outcomes, with resolution of pain, numbness, and restoration of motor function. Recovery typically involves a period of physical therapy to regain strength and mobility.
• Factors Influencing Recovery: The duration and severity of nerve compression prior to intervention can influence the extent of recovery. Long-standing or severe compression may result in slower or incomplete neurological recovery.

Understanding the unique anatomy and potential for compression by the Ligament of Struthers is key for both accurate diagnosis and effective management of this less common, yet impactful, peripheral nerve entrapment.