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Home , Polyneuropathy, Ulnar neuropathy, Ulnar tunnel syndrome

Compressive Ulnar Neuropathies at the : I. Etiology and Diagnosis

Martin A. Posner, MD

Abstract

Ulnar compression at the elbow can occur at any of five sites that begin arcade is the medial intermuscular proximally at the arcade of Struthers and end distally where the nerve exits the septum. The lateral border is flexor carpi ulnaris muscle in the forearm. Compression occurs most commonly formed by deep fibers from the at two sitesÑthe epicondylar groove and the point where the nerve passes medial head of the triceps. between the two heads of the flexor carpi ulnaris muscle (i.e., the true cubital The arcade of Struthers should tunnel). The differential diagnosis of ulnar neuropathies at the elbow includes not be confused with the far less lesions that cause additional proximal or distal nerve compression and systemic commonly encountered ligament of metabolic disorders. A complete history and a thorough Struthers. The ligament of Struthers are essential first steps in establishing a correct diagnosis. Electrodiagnostic is associated with compression of studies may be useful, especially when the site of compression cannot be deter- the . Although the lig- mined by physical examination, when compression may be at multiple levels, ament itself has not been implicated and when there are systemic and metabolic problems. in compression of the , J Am Acad Orthop Surg 1998;6:282-288 compression by the supracondylar process has been reported.2 In the absence of an arcade of Struthers, the medial intermuscular Ulnar nerve compression at the In the middle third of the arm, septum can cause compression as elbow is commonly accepted as the the ulnar nerve pierces the medial the nerve passes over its edge, second most frequently encoun- intermuscular septum and de- which is thicker distally than proxi- tered nerve entrapment in the upper scends along the medial head of mally. This can occur after anterior extremity, exceeded in prevalence the triceps muscle. The first area of dislocation of the nerve or as a only by . potential compression, which is the postoperative complication of The incidence of ulnar nerve com- widest, begins proximally at the ulnar nerve transposition when the pression is probably greater if one arcade of Struthers and ends distal- septum has not been excised. The includes those individuals who ex- ly near the medial epicondyle. The medial head of the triceps muscle perience transient numbness and arcade of Struthers is a musculofas- can also compress the nerve in this when they lean on the cial band, 1.5 to 2.0 cm in width, flexed elbow or when the elbow is which is located an average of 8 cm flexed for a prolonged period. proximal to the medial epicondyle. In an anatomic study of cadaver Dr. Posner is Clinical Professor of Ortho- paedics, New York University School of extremities, it was present in 70% , New York, NY; and Chief of Hand 1 Anatomy and Etiology of specimens. The arcade, which Services, New York University Medical runs oblique and superficial to the Center/Hospital for Joint Diseases Department The boundaries for potential ulnar ulnar nerve, is composed of the of Orthopaedic and Lenox Hill nerve compression begin approxi- deep investing fascia of the arm, Hospital, New York. mately 10 cm proximal to the el- superficial muscle fibers from the Reprint requests: Dr. Posner, 2 East 88th bow and end about 5 cm distal to medial head of the triceps (its most Street, New York, NY 10128. the joint. The ulnar nerve can be obvious component), and the compressed anywhere along this Òinternal brachial ligament,Ó which Copyright 1998 by the American Academy of pathway at one or more of five arises from the coracobrachialis Orthopaedic Surgeons. sites (Fig. 1). tendon. The anterior border of the

282 Journal of the American Academy of Orthopaedic Surgeons Martin A. Posner, MD

Site 5: Exit of ulnar nerve from flexor carpi ulnaris Biceps Compression caused by ¥ Deep flexor-pronator aponeurosis Triceps Brachialis

Arcade of Flexor-pronator Struthers muscle group

Site 1: Intermuscular septum Compression caused by ¥ Arcade of Struthers ¥ Medial intermuscular septum Flexor carpi ulnaris ¥ Hypertrophy of the medial head Aponeurosis of the flexor carpi ulnaris of the triceps ¥ Snapping of the medial head Flexor digitorum profundus of the triceps

Site 2: Area of medial epicondyle Site 3: Epicondylar groove Site 4: Compression caused by Compression caused by Compression caused by ¥ Valgus deformity of the bone ¥ Lesions within the groove ¥ Thickened OsborneÕs ligament ¥ Conditions outside the groove ¥ Subluxation or dislocation of the nerve

Fig. 1 The five sites for potential ulnar nerve compression and the causes of compression at each site. (Adapted with permission from Amadio PC: Anatomical basis for a technique of ulnar nerve transposition. Surg Radiol Anat 1986;8:155-161.)

area. The muscle head can be ranon groove. This is a fibro- trophic bone, soft-tissue tumors, hypertrophied, as is commonly osseous groove, which is bounded ganglia, osteochondromas, synovitis seen in bodybuilders, or it can snap anteriorly by the medial epicondyle secondary to rheumatoid arthritis, over the medial epicondyle, caus- and laterally by the olecranon and infections (e.g., tuberculosis), and ing a friction . the ulnohumeral ligament; medially, hemorrhage due to trauma or bleed- The second site of potential com- the groove is covered by a fibro- ing disorders, such as hemophilia. pression is the distal end of the aponeurotic band. In its passage Nerve compression secondary to , at or just proximal to the through the groove, the ulnar nerve conditions outside the groove is medial epicondyle. Compression is accompanied by an anastomotic common among individuals who in this area develops as a conse- arterial system composed of the lean on the flexed elbow for pro- quence of a valgus deformity of the superior and inferior ulnar collateral longed periods of time, such as bone secondary to an old epiphy- arteries from above and the posterior truck drivers who rest their seal injury to the lateral condyle or ulnar recurrent artery from below. on the lower edge of the window a malunited supracondylar frac- Compression at this site can be frame while driving and patients ture. secondary caused by a wide variety of lesions confined to bed. External compres- to a humeral fracture was first and conditions, which can be sion can also occur during surgery described by Mouchet in 1914; soon grouped in three categories: lesions due to improper positioning of the thereafter it became known on the within the groove, conditions out- arm. Many patients in whom symp- European continent as the Òmal- side the groove, and conditions that toms develop after surgery are adie de Mouchet.Ó Two years later, predispose the nerve to displace found to have had preoperative Hunt introduced the term Òtardy from the groove. Lesions within the subclinical nerve compressions that ulnar palsyÓ in the United States. groove include fracture fragments were simply aggravated, but not The third area of potential com- and arthritic spurs arising from the caused, by the operation.3 Another pression is the epicondylar or olec- epicondyle or the olecranon, hyper- condition outside the groove that

Vol 6, No 5, September/October 1998 283 Ulnar Neuropathies: Etiology and Diagnosis can cause ulnar nerve compression ment of the elbow. Its roof is a nerve and, more important, com- is the presence of an anomalous fibrous band that is a continuation promise its intraneural circulation. anconeus epitrochlearis muscle that of the fibroaponeurotic covering of Animal studies have demonstrat- arises from the medial border of the the epicondylar groove. The fi- ed the vascular effects of pressure. olecranon and inserts into the medi- brous band has been referred to as At a pressure of 20 to 30 mm Hg, al epicondyle. In humans, the mus- OsborneÕs ligament, the triangular there is impairment in flow in the cle is probably atavistic and is ligament, the arcuate ligament, and epineurial venules and slowing of replaced by a band passing in the the humeroulnar arch. In 1958, intracellular axonal support. How- same direction as the muscle, called Feindel and Stratford named this ever, capillary flow in the endo- the epitrochleoanconeus ligament.4 area the Òcubital tunnel.Ó Although neurium and arteriolar flow in the The third category of neuropathy the term Òcubital tunnel syndromeÓ epineurium and perineurium re- develops as a consequence of the is often used to describe compres- main unchanged. As pressure nerve shifting out of the epicondylar sion of the ulnar nerve anywhere in increases, its effects become more groove with elbow flexion and the elbow, it more accurately refers profound. At 60 to 80 mm Hg, cir- returning to its normal position with to a neuropathy at this specific culation ceases in the venules, arte- elbow extension. The nerve can anatomic location. rioles, and capillaries, and the nerve either subluxate onto the tip of the The nerve is vulnerable to com- becomes ischemic. If pressure is epicondyle or dislocate anterior to pression within the cubital tunnel relieved within 2 hours, intraneural the epicondyle. Either situation can during elbow flexion, because the circulation is rapidly restored, occur as a consequence of congenital tunnel normally narrows as Os- although the nerve remains edema- laxity of the fibroaponeurotic cover- borneÕs ligament stretches and tous for hours due to increased per- ing over the epicondylar groove or a becomes taut, and the medial collat- meability of the epineurial vessels. traumatic tear in the covering. It can eral ligament relaxes and bulges Prolonged compression, which also result from congenital hypopla- medially (Fig. 2). OsborneÕs liga- mimics many clinical situations, sia of the trochlea or posttraumatic ment stretches 5 mm for every 45 leads to permanent nerve damage. deformity of the medial epicondyle. degrees of elbow flexion; from full The fifth site of potential com- Subluxation or dislocation of the extension to full flexion, it elongates pression is where the ulnar nerve ulnar nerve, both pathologic condi- 40%.7 The cross-sectional contour of leaves the flexor carpi ulnaris. tions, should not be confused with the tunnel changes from an oval in Normally, the nerve enters the asymptomatic hypermobility of the elbow extension to a flattened muscle at the cubital tunnel, re- nerve, which is usually bilateral and ellipse in elbow flexion.8 Pressure mains intramuscular for a distance is found in approximately 20% of within the tunnel increases 7-fold of approximately 5 cm, and then the population.5 However, hyper- with elbow flexion and more than penetrates a fascial layer to lie be- mobile are predisposed to 20-fold when contraction of the flex- tween the flexor digitorum superfi- become inflamed by constant fric- or carpi ulnaris muscle is added.9 cialis and flexor digitorum profun- tion over the medial epicondyle. These increases in pressure cause dus muscles. The nerve can be They are also at risk to be com- mechanical deformation of the constricted by this fascia, which pressed, when the elbow is flexed, by external forces such as tight casts or splints applied for conditions Medial epicondyle unrelated to the ulnar nerve. A OsborneÕs ligament hypermobile nerve can also be inad- Ulnar nerve becomes taut vertently injured by an injection OsborneÕs ligament administered to treat medial epi- 6 Medial collateral condylitis. Medial collateral ligament relaxes ligament The fourth site of potential com- and bulges pression is where the nerve passes medially through a tunnel between the Olecranon humeral and ulnar heads of the flexor carpi ulnaris muscle. This Elbow Extension Elbow Flexion site and the epicondylar groove are Fig. 2 Anatomy of the cubital tunnel in elbow extension and flexion. (Adapted with per- the most common sites for ulnar mission from Adelaar RS, Foster WC, McDowell C: The treatment of the cubital tunnel nerve compression. The floor of the syndrome. J Hand Surg [Am] 1984;9:90-95.) tunnel is the medial collateral liga-

284 Journal of the American Academy of Orthopaedic Surgeons Martin A. Posner, MD has been referred to as the Òflexor cervical disk disease or arthritis. results have been reported in 10% pronator aponeurosis.Ó10 Axial compression of the spine may of normal individuals.12 Scarring anywhere along the reproduce radicular pain. When Numbness in the ulnar nerve course of the nerve can restrict its compression in the brachial plexus distribution of the hand is a com- excursion and result in a traction is suspected, the presence of tender- mon finding, which can vary in injury. Normal excursion of the ness or a Tinel sign with percussion severity depending on the degree nerve with elbow motion is as high in the supraclavicular and infra- and duration of nerve compression. as 10 mm proximal to the medial clavicular areas should be checked. The sensory deficits usually in- epicondyle and 6 mm distal to the Compression can also be due to clude both sides of the little finger epicondyle.11 The nerve itself . There and the ulnar half of the ring fin- stretches as much as 4.7 mm with are a number of provocative tests ger, although normal variations in elbow flexion, and additional for this condition, which are aimed the sensory distribution of the stretching occurs with abduction primarily at obliterating the radial ulnar nerve may extend the numb- and external rotation of the shoul- pulse. These tests include AdsonÕs ness to the middle finger or restrict der and extension of the wrist. maneuver, WrightÕs maneuver, and it to the little finger. A sensory RoosÕs test (also referred to as the deficit over the dorsoulnar aspect overhead exercise test). There is of the hand and the dorsum of the Diagnosis also the costoclavicular maneuver, little finger aids in differentiating a which involves scapular retraction neuropathy at the elbow from one Clinical Findings into a military brace posture. All at the wrist. When nerve compres- A complete history, including these tests are frequently positive sion is at the wrist in the canal of assessment of work or leisure-time in normal individuals; they are Guyon (), activities that aggravate the condi- therefore nonspecific in the patient dorsal sensibility remains intact tion, and a physical examination whose complaints are predomi- because that area is innervated by are essential first steps in arriving nantly neurogenic. For a positive the dorsal sensory branch of the at a correct diagnosis. Symptoms test to be considered relevant, it ulnar nerve, which leaves the main can vary from mild numbness and should reproduce the patientÕs body of the nerve at a more proxi- paresthesias in the ring and little symptoms and not simply obliter- mal level. Generally, it is 5 to 6 cm fingers to severe pain on the medial ate the radial pulse. proximal to the ulnar styloid, but aspect of the elbow and dysesthe- The elbow is then inspected for occasionally it is at the level of the sias radiating distally into the hand deformity, and the normal carrying ulnar head. Simultaneous com- and sometimes proximally to the angle and active ranges of joint pressive ulnar neuropathies at the shoulder and neck. The occurrence motion are measured. The ulnar elbow and wrist are common; in of mild paresthesias as an isolated nerve is palpated along its course that instance, the Tinel sign will be symptom is not necessarily cause for any enlargement or mass and in positive at both locations. for concern, as it commonly occurs the epicondylar groove during Sensibility can be tested in sev- in individuals who keep their el- elbow flexion for any subluxation eral ways. Because the initial bows flexed for prolonged periods or dislocation. Local tenderness changes in nerve compression af- of time during the day or at night anywhere along the course of the fect threshold, testing for vibratory while sleeping. Patients with early nerve aids in identifying sites of perception and light touch with the stages of nerve compression may compression. A provocative test use of Semmes-Weinstein monofil- not complain of any actual weak- analogous to PhalenÕs test for carpal aments is more important than ness, although they may be aware tunnel syndrome is the elbow flex- measuring static and moving two- of some deterioration in hand func- ion test, which involves maintain- point discrimination, which reflect tion. They may report difficulty in ing the elbow in full flexion with innervation density. Innervation carrying out certain tasks, such as the wrist in full extension for 1 density is compromised only after opening bottles and jars, or may minute (up to 3 minutes is consid- there is axonal degeneration, which simply state that their hands fa- ered by some to be a more ap- is more likely to occur with chronic tigue quickly with repetitive activi- propriate duration). The test is con- nerve compression of at least sever- ties. sidered positive if paresthesias or al yearsÕ duration. The physical examination should numbness occurs in the ulnar nerve Muscle weakness generally oc- always start at the neck. Any limi- distribution. As with PhalenÕs test, curs later than numbness, although tation of motion, particularly when the elbow flexion test is more sensi- occasionally inability to adduct the accompanied by pain, may indicate tive than specific, and false-positive little finger (positive Wartenberg

Vol 6, No 5, September/October 1998 285 Ulnar Neuropathies: Etiology and Diagnosis sign) is an early presenting sign. the interphalangeal joint of the Weakness affects the intrinsic mus- thumb) and a positive JeanneÕs sign cles in the hand more commonly Motor to FCU (hyperextension of the metacarpo- Motor to FCU than the extrinsic muscles in the and FDP phalangeal joint of the thumb). forearm, which can be readily When extrinsic weakness occurs, explained by SunderlandÕs study of it always involves the flexor digito- intraneural topography.13 The rum profundus to the little finger. motor fascicles to the intrinsic mus- The flexor digitorum profundus to Motor to cles, as well as the sensory fasci- intrinsic the ring finger may also be weak, cles, are situated more medial or muscles but usually not to the same degree superficial in the ulnar nerve at the because its muscle fibers are fre- elbow than the motor fascicles to Sensory to hand quently dually innervated by both the extrinsic muscles, and are the ulnar nerve and the anterior therefore more vulnerable to com- Fig. 3 The intraneural topography of the interosseous branch of the median pression (Fig. 3). ulnar nerve in the epicondylar groove. nerve. Weakness of the flexor carpi Comparing the strength of the Both sensory fascicles and motor fascicles ulnaris muscle is rarely encountered. to the intrinsic muscles are situated medial- ulnar nerveÐinnervated first dorsal ly or superficially in the nerve. The motor interosseous muscle with that of the fascicles to the extrinsic muscles, except for Imaging Studies median nerveÐinnervated abductor a small fascicle to the flexor carpi ulnaris Radiographic examination of the (FCU), are situated laterally or deeper in pollicis brevis muscle is important. the nerve and are therefore less vulnerable elbow is always necessary. In However, anomalous intrinsic mus- to compression. FDP = flexor digitorum addition to routine anteroposterior, cle innervation is common, occur- profundus. oblique, and lateral views, a view ring in approximately 20% of the profiling the epicondylar groove is population.14 The most common useful in patients with arthritic and anomalous neural pathway is the traumatic conditions in the elbow. Martin-Gruber communication in are abduction of the index finger Osteophytes or bone fragments the proximal forearm, which carries by the extensor indicis proprius, from the medial trochlear lip are motor fibers from the median nerve adduction of the thumb by the often seen in these patients. to the ulnar nerve. A similar but far extensor pollicis longus, and ab- The role of magnetic resonance less common connection between duction and adduction of the fin- imaging is limited. Although this the two nerves exists in the distal gers by the extrinsic digital exten- modality is capable of visualizing forearm. In the hand, there is the sors and flexors, respectively. swelling or enlargement of the ulnar Riche-Cannnieu connection be- Trick movements are always weak nerve in the epicondylar groove as tween the motor branch of the movements, which can be detected well as space-occupying lesions, ulnar nerve and the recurrent by careful observation and by pal- its value is primarily academic. motor branch of the median nerve. pating the muscle being tested. A Magnetic resonance imaging is not These anomalous neural communi- useful test for ulnar nerve function essential for either diagnosing a cations in the forearm and hand that is difficult to duplicate by any neuropathy or determining appro- explain how the intrinsic muscles trick movement is the Òcrossed fin- priate treatment. Perhaps in the can be completely innervated by gersÓ test. This test is based on the future, with continuing technical just one nerve, resulting in the so- ability to cross oneÕs middle finger advancements, it will become more called ulnar hand or median hand. over the index finger, the supersti- useful for detecting early nerve More commonly, one or more tious Ògood luckÓ gesture learned damage. intrinsic muscles have dual inner- in early childhood.15 vations. When intrinsic weakness is Electrodiagnostic Studies In addition to these anomalous severe and associated with muscle Electrodiagnostic studies are muscle innervations, the examining wasting, it is indicative of chronic never a substitute for a complete must also be aware of the nerve compression of many monthsÕ history and thorough physical various Òtrick movementsÓ where- or yearsÕ duration. Muscle weak- examination. Although these stud- by intact muscles mimic move- ness in these cases is commonly ies are usually obtained when ments normally provided by weak- associated with clawing of the ring nerve compression is suspected, ened muscles. Common examples and little fingers and weakness of they are not essential when the of trick movements for the ulnar thumb pinch, characterized by a diagnosis is obvious on clinical nerveÐinnervated intrinsic muscles positive FromentÕs sign (flexion of examination. Electrodiagnostic

286 Journal of the American Academy of Orthopaedic Surgeons Martin A. Posner, MD studies can sometimes be mislead- present, short-nerve-segment stimu- ulnar nerve at the elbow, anti- ing, and they have a false-negative lation (the ÒinchingÓ technique) can dromic responses are easier to elicit, rate similar to that in patients with be used to localize the lesion.17 This and are recorded by a ring elec- carpal tunnel syndrome. False- technique involves stimulating the trode placed around the little fin- negative studies occur when non- nerve at 2-cm intervals across the ger. Sensory conduction of the dor- compressed nerve fibers are tested elbow. When the points of maxi- sal cutaneous nerve of the hand can rather than the compressed fibers mum conduction delay and drop in also be carried out to distinguish that are causing sensory symptoms amplitude are at or just proximal to compression at the elbow from or muscle weakness. Electrodiag- the medial epicondyle, compression compression at the wrist. nostic studies are important when is probably in the epicondylar Electromyographic studies dem- clinical symptoms and findings are groove; when they are 2 cm distal to onstrate the presence of axonal equivocal, when the site of nerve the epicondyle, compression is prob- degeneration in muscles. Because compression is uncertain or is ably at the cubital tunnel. these changes occur with chronic thought to be at multiple levels, or A Martin-Gruber communica- neuropathies, electromyography is when a or motor tion in the forearm can also lead to not as useful as conduction studies neuron disease is suspected. confusing results, as the hypo- for the diagnosis of early compres- Electrodiagnostic studies include thenar and first dorsal interosseous sions. When abnormalities are motor and sensory conduction muscles are dually innervated by noted, they are initially seen in the velocity measurements and elec- fibers from both nerves. Conse- first dorsal interosseous muscle, tromyography. Motor conduction quently, the CMAP amplitude for followed in frequency by the mus- is measured over a 10- to 12-cm these intrinsic muscles will normal- cles in the hypothenar eminence. segment of the ulnar nerve where it ly be greater when the ulnar nerve crosses the elbow. The skill and is stimulated at the wrist rather experience of the physician per- than at the elbow, because at the Differential Diagnosis forming the test are important wrist the ulnar nerve also contains because anatomic variations can be fibers from the median nerve. The The differential diagnosis includes encountered. The test should al- amplitude at the elbow will nor- any lesion that affects the origins of ways be carried out with the elbow mally be decreased, which may be the ulnar nerve in the cervical spine flexed, because conduction times misinterpreted as a conduction (C8-T1 nerve roots) and/or the are as much as 7 to 9 m/sec slower block. When ulnar nerve compres- brachial plexus (medial cord). The when the test is performed with the sion is present, weakness of the most common spinal lesions are elbow in full extension.16 The rea- ulnar intrinsic muscles may be those due to cervical disk disease, son for this is that the true length of masked by the innervation they followed by spinal tumors and the ulnar nerve is frequently under- receive from the median nerve. syringomyelia. In the brachial estimated with the elbow in exten- Awareness of a Martin-Gruber plexus, the medial cord can be com- sion because the nerve is lax in that communication is also important pressed by thoracic outlet syndrome position. Slowing of motor conduc- when planning surgery, as the or a Pancoast tumor. Electromy- tion is absolute when it is less than point of connection is located 3 to ography of median nerveÐ and 50 m/sec. Slowing can be relative 10 cm distal to the medial epi- ulnar nerveÐinnervated intrinsic when it is more than 10 m/sec condyle.18 When the connection is muscles (C8-T1) is helpful in differ- slower across the elbow than it is close to the epicondyle, there is a entiating lesions in the spine and farther distally in the forearm (from potential risk of damage during brachial plexus from distal com- below the elbow to the wrist) or far- ulnar nerve transposition. pressive neuropathies. While ulnar ther proximally in the upper arm Sensory conduction studies are nerveÐinnervated intrinsic muscles (from the axilla to above the elbow). similar to motor studies in that the may be abnormal with an ulnar The age of the patient must be con- nerve is stimulated and a distant neuropathy, the median nerveÐ sidered when evaluating conduc- is recorded. How- innervated abductor pollicis brevis tion velocities because they can be ever, unlike motor fibers, sensory should be normal. as much as 10 m/sec slower than fibers can be stimulated in two Not infrequently, the ulnar nerve average in the elderly. directions: in the physiologic direc- is compressed at more than one site. When nerve conduction is slowed, tion of conduction (from distal to In 1973, Upton and McComas noted it is often accompanied by a drop in proximal [orthodromic]) and in the that many patients with peripheral amplitude of compound muscle opposite direction (from proximal compressive neuropathies had con- action potentials (CMAPs). When to distal [antidromic]). For the comitant nerve damage at the cervi-

Vol 6, No 5, September/October 1998 287 Ulnar Neuropathies: Etiology and Diagnosis cal roots.19 They observed that classified as minimal, with symp- severe disability. Considering the when neural function was compro- toms of paresthesias and numbness anatomic course of the ulnar nerve mised at one level, the of that but no weakness. Grade II lesions through confined spaces and poste- nerve were more susceptible to are intermediate, with wasting of rior to the axis of elbow flexion, damage at another level, probably the interosseous muscles. Grade III Lundborg21 concluded that the because of impaired axoplasmic lesions are severe, with complete ulnar nerve was Òasking for trou- flow. They aptly termed this condi- intrinsic muscle paralysis. Al- ble.Ó Normally, the nerve is sub- tion Òdouble crush.Ó Occasionally, though both grade II and III lesions jected to stretch and compression the nerve can be compressed at are characterized by numbness, the forces that are moderated by its three sites (Òtriple crushÓ). difference between the two grades ability to glide in its anatomic path The differential diagnosis of is based solely on the degree of around the elbow. When normal ulnar neuropathies should also muscle weakness. McGowanÕs sys- excursion is restricted, irritation include systemic and metabolic dis- tem is, therefore, essentially a pre- ensues. This results in a cycle of orders, such as mellitus, operative rating of intrinsic muscle perineural scarring, further loss of hypothyroidism, , ma- function. excursion, and progressive nerve lignant , and vitamin Currently, there is no consensus damage. Not uncommonly, a com- deficiencies. However, the pres- on any scoring system. Available pressive neuropathy at the elbow is ence of any of these problems does systems either rate subjective symp- associated with additional com- not exclude the possibility of a con- toms, which are difficult to quanti- pression proximally in the neck or comitant compressive neuropathy. tate, or fail to compare preoperative brachial plexus and/or distally in and postoperative conditions. the canal of Guyon. Multiple sites of compression can usually be Classification Systems identified from the history and Summary physical examination. While elec- Classification of ulnar nerve func- trodiagnostic studies may be help- tion was introduced in 1950 by Compressive neuropathy of the ful, their results must be correlated McGowan, who proposed a three- ulnar nerve at the elbow is a com- with the clinical picture for proper grade system.20 Grade I lesions are mon problem and can result in interpretation.

References

1. Spinner M, Kaplan EB: The relation- sion lesions of the ulnar nerve. J Bone and other tests of ulnar nerve motor ship of the ulnar nerve to the medial Joint Surg Br 1968;50:792-803. function. J Hand Surg [Am] 1980;5: intermuscular septum in the arm and 8. Apfelberg DB, Larson SJ: Dynamic 560-565. its clinical significance. Hand 1976;8: anatomy of the ulnar nerve at the el- 16. Kincaid JC: AAEE minimonograph 239-242. bow. Plast Reconstr Surg 1973;51:79-81. #31: The electrodiagnosis of ulnar neu- 2. Fragiadakis EG, Lamb DW: An 9. Werner CO, Ohlin P, Elmqvist D: ropathy at the elbow. Muscle Nerve unusual cause of ulnar nerve compres- Pressures recorded in ulnar neuropa- 1988;11:1005-1015. sion. Hand 1970;2:14-16. thy. Acta Orthop Scand 1985;56:404-406. 17. Miller RG: The cubital tunnel syn- 3. Alvine FG, Schurrer ME: Postopera- 10. Amadio PC, Beckenbaugh RD: En- drome: Diagnosis and precise localiza- tive ulnar-nerve palsy: Are there pre- trapment of the ulnar nerve by the tion. Ann Neurol 1979;6:56-59. disposing factors? J Bone Joint Surg deep flexor-pronator aponeurosis. J 18. Uchida Y, Sugioka Y: Electrodiagnosis Am 1987;69:255-259. Hand Surg [Am] 1986;11:83-87. of Martin-Gruber connection and its 4. Masear VR, Hill JJ Jr, Cohen SM: Ulnar 11. Wilgis EF, Murphy R: The significance clinical importance in peripheral nerve compression neuropathy secondary to of longitudinal excursion in peripheral surgery. J Hand Surg [Am] 1992;17:54-59. the anconeus epitrochlearis muscle. J nerves. Hand Clin 1986;2:761-766. 19. Upton AR, McComas AJ: The double Hand Surg [Am] 1988;13:720-724. 12. Rayan GM, Jensen C, Duke J: Elbow crush in nerve entrapment syndromes. 5. Childress HM: Recurrent ulnar-nerve flexion test in the normal population. Lancet 1973;2:359-362. dislocation at the elbow. Clin Orthop J Hand Surg [Am] 1992;17:86-89. 20. McGowan AJ: The results of transpo- 1975;108:168-173. 13. Sunderland S: Nerves and Nerve In- sition of the ulnar nerve for traumatic 6. Idler RS: General principles of patient juries, 2nd ed. New York: Churchill ulnar neuritis. J Bone Joint Surg Br evaluation and nonoperative manage- Livingstone, 1978, pp 780-795. 1950;32:293-301. ment of cubital syndrome. Hand Clin 14. Rowntree T: Anomalous innervation 21. Lundborg G: Surgical treatment for 1996;12:397-403. of the hand muscles. J Bone Joint Surg at the elbow 7. Vanderpool DW, Chalmers J, Lamb Br 1949;31:505-510. [editorial]. J Hand Surg [Br] 1992;17: DW, Whiston TB: Peripheral compres- 15. Earle AS, Vlastou C: Crossed fingers 245-247.

288 Journal of the American Academy of Orthopaedic Surgeons