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CLINICAL & ANATOMICAL ASPECTS OF ULNAR NERVE COMPRESSION AT THE ELBOW: CUBITAL TUNNEL SYNDROME8 October at 19:26 from atlas
'CUBITAL TUNNEL SYNDROME: FEINDEL-OSBORNE SYNDROME'
26 October 2017.
The ulnar nerve is the major nerve about the elbow most susceptible to injury due to compression, traction and repeated irritation.The superficial location of the nerve at the medial elbow contributes to its propensity for damage, along with the wide range of elbow ROM and stresses during throwing.
Other contributors include ganglia, lipoma, ostechondroma, osteophytes, olecranon bursitis, medial epicondylitis, rheumatoid arthritis synovial proliferation, racket sports and occupational causes.
Compression of the ulnar nerve at the elbow (Feindel-Osborne or Cubital Tunnel Syndrome) is SECOND only to carpal tunnel syndrome ( compressive median thenar neuropathy at the wrist)as a source of upper limb entrapment neuropathy.
In 1878 , panas first described what we now regard as tardy ulnar palsy.he presented 3 cases in which either trauma or OA gradually damaged the ulnar nerve.Joh Murphy published the first case in the American literature in 1914.Walter Brickner reported a case in 1924.The first description of ulnar nerve entrapment it the 2 heads of FCU , together with surgical description , was given by Buzzard and sergeant in 1922.The next published description was by Osborne in 1957.In 1958, Feindel and Stratford reported 3 more cases and coined the term' Cubital Tunnel Syndrome'.We can identify at least 5 definite sites of ulnar entrapment above Guyon's canal and Posner has published much of the clinic-pathologic-anatomical work in this area( Charles Guardia III and Stephen Berman at Dartmouth and University of Florida, respectively).
The ulnar nerve is the terminal branch of the medial cord of the brachial plexus and contains fibres from C8, T1 , and occasionally C7.it enters the arm with the axillary artery and passes posterior and medial to the brachial artery, travelling between the brachial artery and vein.at the level of the insertion of the coracobrachialis muscle in the mid third of the arm , the ulnar nerve pierces the medial intermuscular septum (MIMS). This is the first site of potential compression ( James R Verheyden and Andrew K Palmer, Cascades and New York University)-hence the importance of NCS!),to enter the posterior compartment of the arm.here, the ulnar nerve lies on the anterior aspect of the medial head of the triceps, where it is joined by the superior ulnar collateral artery. The medial inter muscular septum extends from the coracobrachialis muscle proximally, where it is thin and friable to the medial humeral epicondyle, where it becomes a thick and distinct septum.
The next site of potential compression is the Arcade of Struthers, found in 70% of individuals, 8 cm proximal to the medial EC, and extends from the MIMS to the medial haed of the triceps.The Arcade of Struthers is formed by the attachments of the internal brachial ligament, a fascial extension of the coracobrachialis tendon, the fascia and superficial fibres of the medial head of triceps, and the MIMS.
The next potential site of compression is as the nerve passes through the cubital tunnel.The deep forearm investing fascia of the FCU, also known as the cubital tunnel retinaculum (CTR), form the rof of the cubital tunnel. The CTR is a 4 mm wide (Compared wit the transvers carpal ligament of the carpal tunnel which is 25 m in axial width) fibrous band that passes from the medial EC to the tip of the olecranon. Its fibres are orientated perpendicularly to the fibres of the FCU aponeurosis, which blends with its distal margin.The elbow capsule and the posterior and transverse portions of the MCL form the floor of the cubital tunnel. The medial EC and olecranon form the walls.
O'Driscoll ( James R. Veryhaden ) believes that the roof of the cubital tunnel , or Osborne Ligament , is a remnant of the anconeus epitrochlearis muscle.He classified 4 types of retinaculum : (i)absent, (ii)thin that becomes tight with full flexion without compressing the nerve,(iii)thick that compresses the nerve between 90 degrees and full flexion, and, (iv)an accessory anconeus epitrochlearis muscle.It was present in 84% of 25 cadavers.
Upon entering the cubital tunnel the ulnar nerve givers off an articular branch to the elbow.It then passes between the humeral and ulnar heads of the FCU and FDP muscles, the next site of potential compression.
About 5 cm distal to the medial EC, it pierces the flexor pronator aponeurosis, and this is another site of potential compression, with compression beneath the red muscle belly of the FCU.
The Ligament of Spinner is an additional aponeurosis between the FDS of the ring finger and the humeral head of the FCU.Thsi attaches directly to the medial EC and medial aspect of the coronoid process of the ulna.it was found in 4 of 20 specimens in one study, and it is important to recognise and to release with anterior transposition of the ulnar nerve IN ORDER TO PREVENT KINKING, if one does practise transposition.
In the forearm, the ulnar nerve extends motor branches to the FCU and the DDP of digits 4 & 5, up to 4 branches may be found, ranging from 4cm above to 10 cm below the medial EC.
The anconeus epitrochlearis, an aberrant muscle may be found in 3-28% of cadavers and in 9 % at surgery for cubital tunnel syndrome.This muscle arises from the medial humeral condyle and inserts on the olecranon, crossing superficially to the ulnar nerve, where it may be a surprising finding causing ulnar nerve compression.
The arcade of Struthers MUST be differentiated from the ligament of Struthers, which is found in 1 5 of the population and extends from a suprcondylar spur and can be found on nhe antero-medial aspect of the humerus, 5 cm proximal to the medial, and can be seen on radiographs.The ligament of Struthers may occasionally cause neurovascular compression, generally involving the median nerve or the brachial artery; however the ulnar nerve can also be compressed.
Posterior branches of the medial ante brachial cutaneous nerves cross the ulnar nerve anywhere from 6 cm proximal to 4 cm distal to the medial Ec, and are often divided during the surgical incision for Cubital Tunnel, or Fiendl-osborne Syndrome.
3 blood vessels supply the ulnar nerve: (i) superior ulnar collateral artery, (ii) inferior ulnarv collateral artery , and (iii) posterior ulnar recurrent artery.Typically , the inferior ulnar collateral artery (and often the posterior ulnar recurrent artery) is SACRIFICED during anterior transposition, and with the risk to the muscle branches referred to above lead to this operative option as not very favoured, particularly with this author.At the level of the medial EC, the inferior ulnar collateral artery is the sole blood supply to the ulnar nerve.There was NO anastamosis between the superior ulnar artery and the posterior ulnar recurrent arteries in 20 of 22 arms- instead communication occurred through proximal and distal extensions of the inferior ulnar collateral artery.
Acute ulnar neuropathy is 3-8 times more common in men than women. Contreras et al revealed that the medial aspect of the elbow has 2-19 times more fat content in women than men.In men the coronoid tubercle is approximately 1.5 x larger. He suggests that the coronoid process may be a potential site for ulnar nerve compression in men, and the fat in women protects the nerve.
The MOST COMMON sites for ulnar compression at the elbow are :
(i) medial intermuscular septum
(ii)the Arcade of Struthers
(v)deep flexor-pronator aponeurosis.
The 2 MOST common sites are the retrocondylar groove and the true cubital tunnel where the ulnar nerve passes between the 2 heads of the FCU.
(i)A THOROUGH UNDERSTANDING & KNOWLEDGE OF ANATOMY IS MANDATORY FOR SURGEONS DEALING WITH UPPER LIMB ULNAR ENTRAPMENT NEUROPATHY, AS WELL AS THE ANATOMOCAL / VASCULAR/ INNERVATIONAL CONSEQUENCES OF TRANSPOSITION.
(ii) NEUROPHYSIOLOGY IS OBVIOUSLY MANDATORY IN CONFIRMING THE CONDITION(DDx KLUMPKE OR CERVICAL RADICULOPATHY) AND DETERMING THE SITE OF COMPRESSION .
(iii)THE NEUROLOGIST MAY ADVISE THE APPROPRIATE LEVEL, AND MRI IS ESTABLISHING ITSELF A SUPPORTIVE EVOLVING IMAGING ROLE, BUT THE SURGEON MUST KNOW THE SURGICAL ANATOMY INTIMATELY BEFORE EMBARKING ON A SEEMINGLY SIMPLE PROCEDURE.
Patients and IMEs are advised to follow the advice of their treating medical practitioner / indemnity insurer at all times.The opinions stated herein are those of the author.
Dr Michael Coroneos is a senior Brisbane neurosurgeon with six surgical Fellowships and was honoured to be elevated to Master CIME status by the American Board of Independent Medical Examiners (by 3 examinations and training 2012 to 2017) in May 2017.
Qualifications and Memberships : MCIME FRACS FACS(USA) FRCS(Glasg) FRCS(IRE) FRCS(ENG) FRCS(EDIN)SN MB BS(1st Cl Honours, 1980, UQ) MNSA MNSQ MAPS MASE
Senior Clinical RACS OSCE Examiner/ Mortality Assessor RACS (QASM)/ Honorary Clinical Adjunct Assistant Professor and Examiner / Senior Neurosurgeon/ Master CIME/ Member RACS Academy Surgical Educators.
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