Anatomy & Sites of Compression of Cubital Tunnel



- Discussion:
    - cubital tunnel extends from medial epicondyle to olecranon;
    - it serves as the major contraint for the ulnar nerve as it passes behind the elbow;
    - w/ flexion the cubital tunnel becomes taunt, and with extension the cubital tunnel becomes lax;
    - aponeurotic roof of the cubital tunnel becomes maximally taut during flexion because the 2 points of
           attachment (the medial epicondyle and the olecranon) are farthest apart during this position;
    - it has been suggested that individuals w/ ulnar subluxation may have a deficient cubital tunnel;
    - the floor the cubital tunnel includes the MCL, the joint capsule, and olecranon;

- Sites of Compression:
    - Arcade of Struthers
          - located 8 cm above elbow;
          - in most cases of transposition, division of the ligament of Struthers is not necessary, but should be considered;
    - Medial head of Triceps
    - Medial Intermuscular Septum:
          - becomes thick distally and flares as it inserts onto the medial epicondyle;
          - distal segment of medial intermuscular septum is excised, just above the medial epicondyle;
          - some authors recommend excision of the distal 5-6 cm of the intermuscular septum inorder to avoid iatrogenic
                   compresssion with transposition;
          - references:
                 The relationship of the ulnar nerve to the medial intermuscular septum in the arm and its clinical significance.
    - Medial Epicondyle: nerve may be irritated by medial epicondyle osteophytes;
    - Cubital tunnel (FCU Aponeurosis)
          - roof of cubital tunnel is formed by aponeurosic attachment of 2 heads of FCU, which spans in arcade like manner from medial 
                epicondyle of humerus to the olecranon process of the ulna (also known as Osborne's ligament);
                - cubital tunnel begins where the ulnar nerve passes beneath Osborne's ligament;
          - aponeurosis of origin of the flexor carpi ulnaris;
                - aponeurosis is drawn taut over nerve w/ elbow flexion;
                - point of constriction is 1.5-3.5 cm distal to epicondyle;
          - floor is formed by MCL of elbow, which extends in fanlike fashion from medial border of olecrnaon process
                to base of  epicondyle;
          - in majority of cases sharp proximal margin of musculoaponeurotic arcade is constricting agent in pts w/
                cubital tunnel syndrome;
          - at level of medial epicondyle before nerve enters cubital tunnel, it gives off the articular branches to the elbow joint;
          - ulnar nerve reaches groove behind medial epicondyle accompanied by ulnar collateral artery;
                 - anterior band of medial collateral ligament is anterior to ulnar nerve, which does not cross it;
          - branches to FCU & medial half of FDP are given off distal to entry of nerve into cubital tunnel, yet these 2 muscles are usually 
                 spared in cubital tunnel syndrome;
    - Anconeus epitrochlearis
         - anomalous muscle which arises from medial border of olecranon & adjacent triceps & inserts into the medial epicondyle;
         - may be found in about of 10% patients undergoing cubital tunnel release;
         - it crosses ulnar nerve posterior to the cubital tunnel, and may cause ulnar neuritis;
    - Arcuate Ligament: (Aponeurosis of FCU)
         - connects the ulnar and humeral heads of the FCU;
         - often requires division into the proximal 1/3 of forearm;
    - Deep Flexor-Pronator Aponeurosis:
         - distal to cubital tunnel (> 4 cm beyond the epicondyle);
         - palpation of the distal course of the nerve can ensure that there is no fascial constriction;
         - ref:
               - Entrapment of the ulnar nerve by the deep flexor pronator aponeurosis.



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Saturday, March 4, 2017 8:04 am