Sulcus ulnaris syndrome (SUS) or cubital tunnel syndrome (CUTS)

Sulcus ulnaris syndrome: What’s that?

The sulcus ulnaris syndrome (also referred to as the cubital tunnel syndrome) is a compression syndrome in the elbow region which causes damage to the ulnar nerve due to increased pressure.

This is frequently associated with sensitivity disorders (e.g. a feeling of numbness), primarily on the lower arm and the hand (little finger and ring finger).

Sulcus ulnaris syndrome causes

The ulnar nerve runs through a bony channel in the elbow region (lat. sulcus), referred to as the cubital tunnel, which should protect the nerve against compression damage in case of movement in the elbow joint. This sulcus is restricted by ligament and muscle structures.

The following factors can change these anatomical structures and consequently damage the ulnar nerve:

• Overstress or repetitive movement
• Long-lasting flexion position (as when sleeping, for example)
• Ongoing pressure load on the elbow
• Injuries/traumas e.g. broken bone
• Luxation in the elbow joint
• General degenerative ligament and muscle structure wear and tear

Some people are born with a more closely formed cubital tunnel. In turn, this increases the risk of nerve damage.

Furthermore, dysplasia on bony prominences may also exert pressure on the ulnar nerve.

Sulcus ulnaris syndrome symptoms

Nerve compression or damage initially causes sensory disorders such as numbness, tingling (formication) and pain in the ulnar nerve treatment region. These are mostly on the lower arm (on the side of the little finger) and the fingers (primarily in the vicinity of the little finger and the ring finger. Therefore, the outset is often acute and symptoms worsen in case of strong flexion in the elbow joint.

The symptomatic status can radiate up to the upper arm/shoulder.

Consequentially, the later course may result in hand asthenia/muscle weakness. Persons affected by this can then no longer move the wrist and fingers or only with great difficulty. This impaired nerve function can, for example, be confirmed via nerve conduction velocity (NCV) measurement.

The so-called claw hand is a symptom of the late stage. It describes a flexion position of the little finger and ring finger due to hypertrophy (shrinkage) of the muscle affected.

Occurrence on both sides is possible and is observed in some 20 % of cases.

Sulcus ulnaris syndrome diagnosis

In addition to general case history (systematic questioning regarding the health status), the physician can examine the inside of the ulnar groove palpably. Here, it is possible to recognise any anatomical peculiarities in the surrounding tissue structures or a dislocation (springing out) of the ulnar nerve.

Furthermore, specific clinical tests for confirmation of the diagnosis exist:

• Tinel’s sign: Tapping the ulnar groove triggers a tingling/numbness sensation in the area of the little finger and ring finger.
• Froment’s sign: Due to the reduced muscle activity or paralysis of the thumb (thumb retractor), compensatory movement follows (flexion) of the thumb end phalanx when trying to touch the index finger with the thumb or hold a leaf between the thumb and index finger.

Moreover, imaging processes such as MRI or ultrasound help to recognise morphological changes to the tissue.

Sulcus ulnaris syndrome therapy

Conservative therapy (without an operation) is often applied via immobilisation of the elbow joint with approx. 30° flexion with a padded brace such as the BORT KubiFX elbow brace or the BORT KubiTal® elbow pad support. If necessary, the wrist is also immobilised. This immobilisation is intended to reduce the pressure load on the ulnar nerve, thus relieving the symptoms.

If conservative therapy achieves no improvement or the symptoms are very pronounced, the treating physician can suggest operational therapy, which takes place open or endoscopically. The objective of both modes of operational therapy is targeted pressure relief of the ulnar nerve in the cubital tunnel.

Prevention of the sulcus ulnaris syndrome

In everyday life, the risk of becoming ill with sulcus ulnaris syndrome can be reduced using the following measures:

• Avoidance of pressure on the elbows → Avoid longer pressure loads on hard surfaces
• Compensate longer elbow joint flexion positions by changing the arm position
• Reduction of repeated burdening arm movement such as during sports activities or when working (e.g. crafts)

In case of hereditary narrowing of the cubital tunnel, the ulnar nerve may naturally have less space, thus increasing the compression risk. Preventive measures may alleviate the symptoms, but not hinder them.

Sources:

AWMF online, Portal der wissenschaftlichen Medizin [Scientific medicine portal] (2025, January 26). Leitlinie Diagnostik und Therapie des Kubitaltunnelsyndroms, Registernummer 005-009 [Guidelines for the diagnosis and treatment of cubital tunnel syndrome, registration number 005-009].