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Cubital tunnel boundaries with diagram

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cubital tunnel syndrome anatomy boundaries walls diagram

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Cubital Tunnel - Boundaries and Anatomy

The cubital tunnel (ulnar tunnel) is a fibro-osseous space on the posteromedial aspect of the elbow through which the ulnar nerve passes from the arm into the forearm.

Boundaries

WallStructure
FloorPosterior band of the ulnar collateral ligament + posteromedial elbow joint capsule + groove between the medial epicondyle and olecranon
Medial wallMedial epicondyle of the humerus
Lateral wallOlecranon process of the ulna
RoofCubital tunnel retinaculum (arcuate ligament of Osborne) - a band of fascia running between the humeral and ulnar heads of the flexor carpi ulnaris (FCU)
The tunnel is oval in cross-section at rest. During elbow flexion, it flattens to an elliptical shape, increasing intratunnel pressure on the ulnar nerve.

Diagrams

Cross-sectional boundaries showing the retinaculum, medial epicondyle, olecranon, and ulnar nerve:
Cubital tunnel borders and contents
Sites of ulnar nerve compression around the elbow (proximal to distal):
Ulnar nerve compression sites at elbow
Cubital tunnel syndrome - relationship of FCU heads and tunnel:
Cubital tunnel syndrome anatomy

Proximal-to-Distal Compression Sites Along the Ulnar Nerve at the Elbow

The "cubital tunnel" in the broad clinical sense encompasses several potential compression points:
  1. Arcade of Struthers - ~8 cm proximal to the medial epicondyle; an intermuscular fascial arcade where the nerve transitions from the anterior to posterior compartment
  2. Medial intermuscular septum - also in the distal arm
  3. Retroepicondylar groove - the ulnar groove between the medial epicondyle and olecranon (the true cubital tunnel, covered by the cubital tunnel retinaculum)
  4. Osborne's ligament / Osborne's band (Arcade of Osborne) - the aponeurotic arch between the two heads of FCU, forming the distal exit of the tunnel; this is the most common site of compression

Contents

  • Ulnar nerve (primary structure)
  • Occasionally small branches of the medial antebrachial cutaneous nerve

Clinical Note

The Sabiston Textbook of Surgery notes that the cubital tunnel retinaculum bridges the medial epicondyle to the olecranon and stabilizes the ulnar nerve during elbow motion. With elbow flexion, the tunnel volume decreases by up to 55%, explaining why flexed-elbow postures (sleeping, phone use) worsen symptoms. - Schwartz's Principles of Surgery, 11th Ed.

List all the possible sites of compress for ulnar nerve

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all sites of ulnar nerve compression entrapment anatomy proximal distal

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