Because of the importance of hand function in most activities of daily living, the ulnar nerve, which provides the predominant motor innervation to the hand, is perhaps the single most important somatic peripheral nerve in the body. Neuropathy of the ulnar nerve may result in significant disability due to loss of hand function from pain, numbness, and weakness. The most common causes of ulnar nerve neuropathy are entrapment, impingement, stretching, and friction at or around the vicinity of the elbow. Because of the multiplicity of pathological processes that can lead to ulnar neuropathy at the elbow, reviewing its causes and treatment as reported in the medical literature can be confusing and misleading. An example of the diversity of perspectives is the variety of names given throughout the last several decades to describe the phenomenon of ulnar neuropathy at the elbow. This disease process has been referred to as tardy ulnar palsy, traumatic ulnar neuritis, compression neuritis of the ulnar nerve, Feindel-Osborne syndrome, and the cubital tunnel syndrome. Tardy Ulnar palsy refers only to patients who develop a slow , chronic deterioration of ulnar nerve function months to years after trauma to the elbow. The term cubital tunnel syndrome oversimplify the ulnar neuropathy at the elbow, which may be due to a number of factors other than compression within the cubital tunnel, such as recurrent subluxation of the ulnar nerve out of its groove, or entrapment proximal or distal to the cubital tunnel. The term cubital tunnel syndrome in its broadest sense, is a focal neuropathy involving the ulnar nerve in the vicinity of the cubital tunnel.
Anatomic Course of the Ulnar Nerve
The ulnar nerve is the largest nerve derived from the medial cord of the brachial plexus, It carries nerve fibers from the eighth cervical and first thoracic nerves. In the upper arm, it courses medial to the brachial artery until the mid-arm, where it pierces the intermuscular septum and travels towards the dorsal and medial aspect of the elbow along with the medial head of the triceps. After passing behind the medial epicondyle of the humerus in a groove between it and the olecranon (referred to as the cubital tunnel), the ulnar nerve enters the forearm between the two heads of the flexor carpi ulnaris muscle. Across this groove, the nerve passes from the extensor compartment in the arm into the flexor compartment of the forearm. More distally in the forearm, the ulnar nerve joins the ulnar artery and emerges into a superficial location just lateral to the flexor carpi ulnaris before passing across the medial wrist.
Innervation by the Ulnar Nerve
Like the median nerve, the ulnar nerve has no branches in the arm, but provides innervation to the forearm and hand. Unlike the median nerve, the motor fibers of the ulnar nerve predominately innervate the hand rather than the forearm. Although the ulnar nerve gives rise to a number of small articular branches to the elbow joint, it is not until the nerve passes between the two heads of the flexor carpi ulnaris that it begins supplying motor and sensory innervation. As the nerve acquires a superficial location after passing beneath the belly of the flexor carpi ulnaris, where it supplies motor innervation to this and the flexor digitorum profundus muscles, it gives off the palmar cutaneous branch which pierces the fascia just proximal to the wrist and supplies the skin of the hypothenar eminence and medial aspect of the palm. The dorsal cutaneous branch of the ulnar nerve arises 5 cm proximal to the wrist and turns dorsally, where it distributes sensory fibers to the medial one-half of the dorsum of the hand and the fourth and fifth digits.
Another surgically important cutaneous branch of the ulnar nerve is the medial antebrachial cutaneous nerve. Although not anatomically a branch of the ulnar nerve, it branches from the medial cord of the brachial plexus at the site of the origin of ulnar nerve. It pierces the brachial fascia at the lower part of the arm at its medial aspect. The larger anterior branch of this cutaneous nerve distributes sensory fibers to the ventral and medial aspect of the distal arm and proximal forearm, as well as to the cubital fossa. Its smaller ulnar branch passes ventral to the medial epicondyle of the humerus and supplies the skin on the dorsomedial aspect of the forearm. Division of one or both of these branches of the medial antebrachial cutaneous nerve during ulnar nerve decompression or transposition at the elbow can lead to postoperative numbness of the medial forearm or to painful neuroma formation. After passing into the palm, the ulnar nerve divides into a superficial and a deep branch. The superficial branch carries sensory fibers to the palmar aspect of the fifth and medial one-half of the fourth digits. The deep (motor) branch passes deep into the palm through the muscles of the hypothenar eminence which it innervates. The hypothenar compartment contains three muscles: the abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi. Continuing its arch across the palm, it supplies innervation to the third and fourth lumbricals, all the interosseous muscles, and more laterally, the adductor pollicis.
Anatomy of the Cubital Tunnel
As the ulnar nerve passes through the groove behind the medial epicondyle of the humerus and past the articulation of the elbow, it lies beneath a fibrous arcade formed by dense fascial strands. This aponeurosis transversely bridges the groove from the attachment of one head of the carpi flexor ulnaris arising on the medial epicondyle of the humerus to the attachment of the other head arising from the medial aspect of the olecranon. This tunnel is referred to as the "cubital tunnel". The most proximal edge of this fibrous arcade, known as Osborne's band, is frequently thickened and often is a site of compression of the underlying nerve.!! ,30 Besides the ulnar nerve, the only contents of the cubital tunnel are the ulnohumeral ligaments encompassing the elbow joint (in particular the ulnar (or medial collateral ligament) and a small amount of fibrofatty tissue. The cubital tunnel can be anatomically divided into three parts: (1) the entrance of the tunnel just behind the medial epicondyle, (2) the area beneath the fascial aponeurosis joining the two heads of the flexor carpi ulnaris, and (3) and the muscle bellies of the flexor carpi ulnaris themselves.
Anatomic and Physiologic Factors Related to Ulnar Neuropathy at the Elbow
Cubital tunnel syndrome may be caused by a number of pathologic processes. Not all of the pathologic processes are compressive lesions or entrapment-type processes. Neuritis related to friction may often play a significant role in the development of cubital tunnel syndrome. This may be especially true of those individuals with chronic and recurrent dislocation of the nerve from the ulnar groove. Compression of the ulnar nerve within the cubital tunnel is most often due to constriction of the nerve by the overlying aponeurosis. Less common compressive agents include inflammation, rheumatoid synovitis, lipomas and other tumors, bone fragments, osteophytes from the ulnohumeral articulation, and a rare anomaly known as the persistent epitrochleoanconeus muscle. Entrapment outside the confines of the cubital tunnel is not unknown. Such areas as the medial intermuscular septum, arcade of Struthers, medial head of the triceps, and the groove between the two muscle bellies of the flexor carpi ulnaris have been implicated as sites of compression. Another common etiology is repetitive trauma to or pressure on the nerve, such as habitual leaning on a desk with the elbows while working. Activities such as shovelling, swinging an axe or pick, and sleeping with the arms flexed at the elbows, lend themselves to the development of ulnar neuropathy. The neuropathy is likely due to alterations in the volume of the cubital tunnel with flexion and extension. In extension, the tunnel is at its greatest volume, due to laxity in the overlying aponeurosis and the underlying ulnar collateral ligament. With flexion, the two points of attachment of the aponeurosis on the epicondyle and olecranon diverge, causing the fascial roof to become taut. Likewise, the ulnar collateral ligament along the floor of the tunnel comes under tension. Reduction in volume of the cubital tunnel results in compression and focal ischemia of the nerve. Elbow flexion and repetitive stretching of the ulnar nerve around the medial epicondyle may also play a role in nerve damage in some patients. Chronic compressive processes such as those observed with malunited elbow fractures and cubitus valgus are the likely agents in tardy ulnar palsy. In contrast, single acute events have resulted in ulnar neuropathy at the elbow: a sharp blow to the elbow, injection of steroids into the elbow for bursitis or medial epicondylitis, and lying supine for a period of time on a hard surface with the elbows unprotected (as may occur in operating room settings or in a drunken stupor). Ten to 30% of cases are idiopathic and the etiology of the neuropathy cannot be explained. Like the median nerve in carpal tunnel syndrome, the ulnar nerve is made more susceptible to compressive lesions by metabolic processes that lead to demyelination, endoneurial/perineurial edema, and nerve ischemia such as occurs in diabetes mellitus, alcoholism and malnutrition, vitamin deficiency, or paraneoplastic syndromes.
Clinical Diagnosis Symptoms and Findings
Numbness and tingling of the ulnar aspect of the hand, weakness and clumsiness, and noticeable thenar and first dorsal interossei atrophy are the most common complaints of patients with cubital tunnel syndrome. Unlike carpal tunnel syndrome, pain is less often a major component of the symptom complex. When pain does occur, it is described as an aching sensation in the medial elbow and forearm associated with dysesthetic tingling in the hand. Lancinating pain is less common and should alert the physician to other possible diagnoses, such as cervical radiculopathy. The patient may describe an abrupt worsening of the condition after a period of exertion or forceful and repetitive flexion-extension actions of the elbow. Patients who sleep with their hands beneath their head, causing prolonged "hyperflexion" at the elbow, may notice their symptoms are more pronounced upon awakening. In a study of 100 patients with "tardy ulnarnerve paralysis", Gay and Love documented intrinsic hand muscle atrophy and weakness in 96%. In fact, onset of visually apparent atrophy frequently predated subjective weakness and sensory changes. Hypoesthesia in the sensory distribution of the ulnar nerve in the hand was observed in 75 % of patients. One-half were noted to have palpable enlargement or swelling of the ulnar nerve behind the elbow. Few had nerve tenderness. Atrophic changes in the hand may be quite pronounced. The hypothenar eminence is often flattened, especially along the medial border of the hand. More impressive, however, is the depression between the thumb and index finger on the dorsal aspect of the hand, indicative of atrophy of the first dorsal interosseous muscle. The three muscles of the hypothenar eminence abduct, adduct, flex, and rotate the fifth digit. The most easily tested is the abductor digiti minimi. Weakness of this muscle will manifest itself by difficulty with fanning (abduction) of the fingers. This is easier to detect when the weakness is unilateral, which allows comparison to the other hand. Weakness of adduction of the little finger is referred to as Wartenberg's sign, perhaps the most subtle and sensitive motor finding in cubital tunnel syndrome. Because most of the muscles innervated by the ulnar nerve are involved in flexion of the digits, grip strength can be an important indicator of ulnar nerve function. The ulnarinnervated adductor pollicis adducts the thumb. This muscle is tested by having the patient grip a piece of paper between his or her thumb and forefinger. Weakness of the adductor pollicis muscle will allow the paper to be easily pulled from the patient's grasp. Some patients will compensate for this weakness by flexing the interphalangeal joint of the thumb using the flexor pollicis longus, a muscle innervated by the anterior interosseous branch of the median nerve. This is referred to as Froment's sign, a finding typically associated with ulnar neuropathy. Weakness of the flexor carpi ulnaris and flexor digitorum profundus muscles (innervated by the ulnar nerve just distal to the elbow) is rarely reported as a clinical finding in cubital tunnel syndrome. Many erroneously attribute this to the belief that the nerves innervating these muscles originate proximal to the elbow. Campbell et al dissected these nerves in 30 cadaveric arms and found only 3 arising at or proximal to the cubital tunnel. They concluded that sparing of the flexor carpi ulnaris is unrelated to the level of origin of its innervating branch, but rather is related to the internal neural topography and to the severity and level of the compression. Others have confirmed why these muscles are spared loss of innervation: the fibers that innervate them lie in the deep aspect of the nerve and are spared the compressive effects of the more superficially-lying fibers to the hand. Weakness, however, is likely more common than reported. Due to the difficulty of detecting subtle motor changes in these muscles, weakness is often not tested for or is overlooked. Although they were unable to accurately assess function of the flexor carpi ulnar is muscle, Craven and Green detected weakness in the flexor digitorum profundus in 66% of their patients undergoing treatment for ulnar neuropathy. In addition, Campbell et al found severe electromyographic abnormalities in the flexor carpi ulnaris in almost half of their cases of ulnar neuropathy. Percussing the area over the ulnar groove may produce tingling and numbness in the medial forearm and hand. This phenomenon is equivalent to the Tinel's sign found in patients with carpal tunnel syndrome. In the author's experience, a positive "Tinel's" of the ulnar nerve is a non-specific finding of dubious pathologic significance and is frequently observed in individuals without any other evidence of ulnar neuropathy. Occasionally, maximal flexion of the elbow for 1-2 minutes may produce symptom exacerbation. The elbow flexion test, the usefulness of which has not been proven, is perhaps analogous to Phalen's wrist flexion test for median nerve entrapment. The importance of careful examination of the elbow cannot be overstated. Cubitus valgus, medial epicondylitis, rheumatoid synovitis, and masses such as tumors or bone fragments may be discovered. Many of these findings may necessitate a course of treatment different than that indicated for idiopathic cubital tunnel syndrome. This is especially true if ulnar nerve subluxation out of its groove and over the medial epicondyle is palpated.
Ancillary Diagnostic Tests
All patients with suspected cubital tunnel syndrome should have as part of their evaluation an electromyogram (EMG) with nerve conduction velocities (NCV), and x-rays of the elbows and cervical spine. The EMG should be used to confirm the diagnosis and to assess the severity of cubital tunnel syndrome. It is also useful to evaluate for (1) a concomitant neuropathy of metabolic or nutritional origin, such as diabetic polyneuropathy and (2) secondary sites of entrapment, such as C8 nerve root impingement (the so-called "double-crush syndrome"). Results of electrodiagnostic tests should never be used as a primary diagnostic tool to indicate need for surgery. Perhaps the most specific and reliable electrodiagnostic indicator of ulnar neuropathy at the elbow is slowed conduction velocity across the elbow. Although normal values have not been firmly established, the conduction velocity (NCV) of the ulnar nerve generally ranges from 47-65 m/sec with an average velocity of 55 m/sec. A reduction in velocity of less than 25% is probably insignificant. Greater than a 33% reduction in velocity certainly indicates a neuropathic process at the elbow. Other EMG findings indicative of cubital tunnel syndrome include diminished numbers of motor units action potentials, fibrillations and positive waves, and, in more advanced cases, polyphasic reinnervation potentials. Another sensitive indicator of altered conduction is loss of evoked sensory potentials. The position of the elbow must be standardized during the performance of electrodiagnostic studies. Variations in NCV readings may occur from flexion to extension, even in normal individuals. X-ray of the elbow provides useful information regarding etiology that assists in management decisions. Arthritic spurs, bony tumors, fractures, or cubitus valgus may be detected. A slightly oblique anteroposterior view, referred to as the cubital tunnel view, is most helpful.
Many pathologic processes of the spinal cord can resemble cubital tunnel syndrome, all of which may present with a predominance of motor signs and symptoms. When patients complain of "numb and clumsy hands," consideration must be given to intrinsic cord lesions such as intramedullary tumors, syringomyelia, amyotrophic lateral sclerosis, and extrinsic cord lesions such as cervical spondylotic myelopathy. Other causes of hand dysfunction and pain include (1) cervical radiculopathy from osteophytes or herniated disc, (2) Pancoast tumors and other lesions of the lower and medial brachial plexus, and (3) other sites of ulnar nerve compression, such as at Guyon's canal. In addition, various systemic polyneuropathies, such as those observed in nutritional deficiencies or diabetes mellitus, may alone or in combination with cubital tunnel syndrome produce weakness, atrophy, pain, and numbness in the distal upper extremity. Occasionally, the effects of age will produce intrinsic hand atrophy and dysfunction.
A major difficulty in evaluating and comparing results of therapy for cubital tunnel syndrome is the lack of a widely accepted and uniform grading system for preoperatively categorizing patients by severity of symptoms and postoperatively grading their outcome. Perhaps the most often used scheme is that proposed by McGowan in 1950. This grading system categorizes ulnar neuropathy based on degrees of muscle weakness. Grade I patients have "minimal lesions, with no detectable motor weakness of the hand." Intermediate lesions are designated Grade II. Grade III includes patients with "severe lesions, with paralysis of one or more of the ulnar intrinsic muscles." Unfortunately, the grades are poorly defined and neglect important features of the syndrome such as pain and numbness. Dellon devised a detailed and well-defined staging system based on sensory and motor changes as well as other physical findings, such as Tinel's sign and the elbow flexion test. His three-tiered system grades severity of preoperative symptoms into mild, moderate, and severe. Although an excellent system for categorizing and comparing patients according to degree of preoperative deficits, its use for postoperative classification of outcome is complex and unwieldy. Another method of comparison is using a system of scoring by points, described by Gabel and Amadio. Points are given based on the severity of three factors: motor function, sensation, and pain (Table 1). No points are given for the most severe symptoms; an increasing number of points are given for less severe symptoms. Postoperative outcome can also be graded into excellent, good, fair, and poor based on this scoring system (Table 2). Regardless of what grading scheme is eventually used, a standard and uniform system should be adopted for the assessment of treatment results.
Historically, cubital tunnel syndrome was thought to be a malady remediable only by surgical treatment. Gay and Love stated "the course of tardy paralysis of the ulnar nerve is characterized by unrelenting progression, and no known conservative form of treatment has been found to be of any permanent benefit." Reports are now emerging that suggest nonoperative means of treatment in selected cases may provide symptomatic relief. Having the patient avoid activities and positions which produce (1) friction from repetitive elbow movements or (2) stretching and compression of the nerve from excessive elbow flexion may be all that is required in many patients with early symptoms. A loose-fitting towel may be wrapped around the affected elbow at night to prevent folding of the arms under the body or head during sleep. In some cases, an elbow splint placed in slight flexion (approximately 30° of flexion) worn only at night may prove to be of benefit. Dimond and Lister suggested in a nonrandomized retrospective study that long-arm splinting of the elbow compares favorably to surgical intervention. Unfortunately, data regarding the results of conservative therapy remain too limited to be meaningful.
Surgical Options and Results
Unlike the limited amount of data on nonoperative therapy, a voluminous amount of information exists regarding surgical options, techniques, and results. Dellon reviewed the literature from 1898-1988 and found more than 50 reports of series totalling more than 2,000 patients treated for cubital tunnel syndrome. Unfortunately, due to the lack of controlled, randomized, or otherwise adequately constructed scientific studies, the data are inconclusive. Statistically significant comparison of surgical techniques and their results remains virtually impossible. The surgeon has available a number of operations devised to relieve the ulnar nerve of the effects of compression or friction in and around the vicinity of the cubital tunnel. Each procedure has proponents heralding the superiority of their preferred technique. To decide on the appropriateness of each procedure, the surgeon must rely only on speculation and his or her personal bias, which is usually a manifestation of the surgeon's training colored by recent experiences, especially those that involve complications or failures. At least five distinct surgical procedures are advocated for the relief of symptomatic cubital tunnel syndrome. They can be grouped into the categories of: (1) decompressive procedures and (2) transposition procedures. Decompressive procedures address the compressive process without surgically mobilizing the nerve from its location in the ulnar groove. The principal decompressive procedures are simple decompression and medial epicondylectomy. The transposition procedures mobilize the nerve and move it anteriorly into a purportedly more protected location. They can be further divided by the position in which the ulnar nerve is placed subcutaneous, intramuscular, or submuscular. The advantages and disadvantages of each procedure are summarized in Table 3.
Surgical decompression or transposition of the ulnar nerve usually performed under general anaesthesia. Some surgeons prefer a regional block (axillary or supraclavicular) placed by the anaesthesiologist immediately prior to the procedure. The affected arm is placed outstretched, with the humerus abducted and externally rotated and the elbow slightly flexed. Several folded surgical towels beneath the elbow help maintain this position. A tourniquet is not necessary and, in fact, may be harmful. The argument against the use of a tourniquet during any type of peripheral nerve surgery is convincing. With increasing extraneural pressure, segmental intraneural blood flow is diminished. At 80 mm Hg, complete intraneural ischemia occurs. Soon, epineural and endoneural edema develops, which further aggravates the compression and ischemia of the nerve, Distal to the tourniquet, the already chronically ischemic nerve at the entrapment site is further deprived of blood flow due to regional loss of blood flow. Venous congestion within the nerve can further complicate endoneural edema and ischemia. Furthermore, hemostasis is best acquired if the small arterioles and veins are electrocoagulated and divided as they are encountered. Simply closing the wound, wrapping the extremity tightly, then releasing the tourniquet places the wound at risk for hematoma formation, Ultimately, the entire procedure is placed at risk for failure. Near bloodless surgery can be easily accomplished without use of a tourniquet if adequate attention to detailed hemostasis is given. Visualization is improved by using headlamp illumination and loupe magnification.
The most common operative techniques are described here and their advantages and disadvantages are discussed.
Simple decompression, also known as cubital tunnel release, is the simplest of the five procedures. Other techniques are more extensive variations of this basic operation. Osborne was among the first to advocate the procedure more than three decades ago. In recent years, an increasing number of surgeons appear to be turning from the use of the transposition procedures for "typical" cubital tunnel syndrome to this simpler, safer, and perhaps equally efficacious mode of therapy. The patient is positioned in the standard fashion described above. A 6-7 cm linear incision is made parallel to the ulnar nerve and centered between the medial epicondyle and the prominence of the olecranon. Dissection is carried down to the underlying fascia. The ulnar nerve is approached as it courses under the medial epicondyle just proximal to the point where it passes under Osborne's band, the thickened aponeurotic edge of the roof of the cubital tunnel. The rare, anomalous epitrochleoanconeus muscle may be observed in the place of the aponeurotic roof stretching over the cubital tunnel. Tracing the nerve distally, the aponeurosis is sharply divided, thereby "releasing" the nerve from the confines of the cubital tunnel. Division of the tissues over the nerve is continued distally as the nerve passes into the muscular cleft between the two heads of the flexor carpi ulnaris. If a point of constriction along the nerve is observed after decompression, the epineurium at the constricted site may be longitudinally incised and opened for 1-2 cm -i.e. an epineurotomy. Internal neurolysis plays little role in the initial surgical procedure. The nerve itself is not removed from its bed; hence, the "extrinsic circulation" of the nerve is not adversely altered and division of the small articular branches of the ulnar nerve is not necessary. The wound is then closed and the elbow placed in a soft, bulky dressing. The patient is instructed to gently flex and extend the elbow for its full range of motion for the first 2 weeks but not to use it for strenuous or exertional activities. Use of a nocturnal splint is recommended for patients who tend to flex their elbows at night.
This procedure, first described by King and Morgan in 1950, has not gained wide acceptance despite several favourable reports. Based on the premise that the offending agent in ulnar neuropathy at the elbow is the median epicondyle, proponents advocate the logic of removing the epicondyle as one would remove any offending mass to relieve tension on the nerve and allow it to find its own optimal position. In this sense, the operation can also be considered a transposition procedure. The technique for medial epicondylectomy approximates the technique for simple decompression, with the exception of the centering of the short linear incision over the medial epicondyle and the removal of the medial epicondyle. The periosteum over the epicondyle is incised in a longitudinal or curvilinear fashion and retracted off the bone along with the origin of the flexor-pronator muscle group. The flexor-pronator muscle group includes the pronator teres, flexor carpi radialis, medial head of the flexor carpi ulnaris, flexor digitorum superficialis, and the palmaris longus, all of which share a common tendinous origin on the anterior aspect of the medial epicondyle. Using rongeurs or an osteotome, the epicondyle is then completely removed. Incomplete amputation of the tip of the epicondyle may leave a sharp edge at the condylar base which may abrade and damage the ulnar nerve. Care should also be taken not to disrupt the ulnar collateral ligament at the base of the epicondyle; injury to this ligament may lead to elbow instability. The periosteum and tendinous origin of the flexor-pronator muscle group are repaired over the waxed bony defect as the elbow is held in extension. Before closure, the elbow is placed through a full range of motion. The nerve should slide freely to and fro over the resected condylar mass and the reattached muscle mass. The wound is then closed in a routine manner. Postoperative care is provided in the same manner as in the simple decompression.
Subcutaneous transposition is the oldest and most commonly performed of the anterior transposition procedures. It has been widely applied since the turn of the previous century. A 12-15 cm curvilinear incision arching anteriorly over the medial epicondyle is utilized. As compared to the smaller linear incision, the curvilinear incision lessens the possibility of adhesions and scarring of the incision to the underlying nerve and provides better exposure with which to deal with proximal and distal compressive areas. As in the simple decompression, the aponeurotic roof of the cubital tunnel is sharply divided and the ulnar nerve is "released". Division of the tissues over the nerve is continued distally as the nerve passes into the muscular cleft between the two heads of the flexor carpi ulnaris. Taking care not to injure the motor branches to the flexor carpi ulnaris, the dissection is continued into the proximal forearm until it is certain no further sites of distal compression exist. Similarly, the ulnar nerve is followed proximally along the medial head of the triceps for 7-8 cm to the often sharp edge of the intermuscular septum, which is also divided. The arcade of Struthers, an inconstant fascial band extending from the medial head of the triceps to the intermuscular septum, is likewise divided. Once the ulnar nerve is adequately decompressed from beneath the flexor carpi ulnaris to the medial intermuscular septum, the nerve is elevated, encircled with a vessel loop, and dissected from its bed within the ulnar groove. The small articular branches from the nerve are divided, as are any small vessels passing into the epineurium from the surrounding soft tissues. As much epineurium and perineural fatty tissue as possible should be left around the nerve to limit post-operative adhesions and to preserve perineural vasculature. Mobilization of the ulnar nerve continues proximally and distally for at least 12 cm. The nerve is moved anterior to the epicondyle and the flexor-pronator muscle group arising from it. Occasionally, the length of immobilization necessary to prevent stretching or acute angulation of the nerve over the anterior aspect of the extended elbow is 16 cm, a length which precariously places the ulnar nerve at risk for ischemia. Adequate decompression of overlying fascial bands or planes must be carried out at the proximal and distal extents of the nerve exposure prior to transposition. Sacrifice of the muscular branch to the flexor carpi ulnaris should be avoided. Should the muscular branch cause distal tethering during anterior transposition, intrafascicular dissection for 2-3 cm may be necessary to free it from the nerve proper. A fascial sling is created over the ulnar nerve to prevent it from slipping back into the ulnar groove; care must be taken not to recreate a new site of ulnar nerve compression or entrapment. The nerve is carefully examined along its entire exposure with the elbow both in flexion and extension to be sure the nerve does not slip back into the ulnar groove and that there are no additional sites of entrapment or kinking. The wound is then closed in a routine fashion. The elbow is usually placed in a plaster long-arm splint postoperatively.
This procedure protects the ulnar nerve in a vascularized muscle bed. However, it is looked upon less favorably because of the development of circumferential scarring and adhesions, or cicatrix, making the nerve more vulnerable to traction forces. The operation is carried out in the manner of the subcutaneous transposition. Instead of creating a fascial sling over the nerve, however, an intramuscular trough is created by incising the flexorpronator muscle mass. The ulnar nerve is placed into the muscular bed and over sewn.
Also known as the Learmonth procedure, submuscular transposition was developed to overcome some of the deficiencies of the subcutaneous and intramuscular techniques. The literature is replete with descriptions of this technique and its numerous modifications. As with the intramuscular transposition, the transposed nerve is more protected and is less angulated over the flexor-pronator mass as compared to the subcutaneous technique. Unlike the intramuscular transposition, the ulnar nerve is free to slide to and fro with elbow movement and is less prone to scarring and adhesions with the sub muscular technique. Once the ulnar nerve has been adequately mobilized from the medial intermuscular septum to its course deep to the flexor carpi ulnaris, but prior to its transposition anterior to the epicondyle, the origin of flexor-pronator muscle mass is detached from the medial epicondyle. Levy and Apfelberg described detaching the tip of the epicondyle along with the tendinous origin and reattaching it with wire suture after transposing the ulnar nerve beneath the muscle mass. The flexor-pronator muscle mass is elevated using a periosteal elevator; caution must be exercised to avoid injury to the nearby median nerve and brachial artery bifurcation. The ulnar nerve is transposed anteriorly and placed beneath the muscle mass to lie upon the brachialis fascia a centimetre or so medial to the median nerve. A gentle anterior curve of the nerve should occur with this technique, a decided advantage over the subcutaneous transposition. The elbow is flexed and the forearm pronated to assist in reattaching the flexorpronator mass. Dellon describes elongation of the muscle mass through a Z-plasty and muscle slide technique so that no additional tension is placed on the ulnar nerve. 2-0 gauge nonabsorbable suture is used, being careful not to catch the transposed nerve in the suture line. The wound is closed and the elbow is placed in a long-arm splint in a flexed and pronated position.
Most other techniques are, in one form or another, modifications of the five listed above. One particularly novel technique deserves further comment. Some surgeons have long used Silastic as an adjunct to peripheral nerve repair. Campbell et al reported the use of a Silastic envelope placed around the ulnar nerve in patients undergoing reoperation for painful dysesthesia and progressive neurologic deficit following failed subcutaneous transposition procedures. Their rationale is that the Silastic will prevent rescarring and entrapment of the nerve and preserve its free, unrestricted movement across the elbow. Once the nerve is separated and elevated from its scarred postoperative bed, a piece of Silastic measuring 15 cm long and 3 cm wide is folded around the nerve and sutured. Campbell does not advocate the use of this technique as a primary procedure as he believes the presumed risks of rejection due to infection associated with the implantation of a foreign body outweigh the relatively low risk of entrapment in scar tissue. Benoit et al described the use of a 6 cm long Silastic sheath sutured around the ulnar nerve after simple decompression as a primary procedure.
Extended cubital tunnel release with partial osteotomy of the medial epicondyle
Brian K. Willis proposed a technique, that uses the many advantages of simple decompression, yet addresses its shortcomings by more extensively exploring and decompressing the nerve. Though perhaps an overly long title, the author refers to this technique as "extended cubital tunnel release with partial osteotomy of the medial epicondyle". This hybrid of the simple decompression and medial epicondylectomy uses the excellent exposure of the transposition procedures without accruing their disadvantages. As in the transposition techniques, the classic 12-15 cm curvilinear incision arches anteriorly over the medial epicondyle. Care is taken not to inadvertently divide branches of the medial antebrachial cutaneous nerve. The roof of the cubital tunnel is incised and the section of the ulnar nerve from just proximal to the medial intermuscular septum to its location deep to the flexor carpi ulnaris is explored and decompressed. An epineurotomy is performed at any observed site of nerve constriction if needed. At this point, any similarity to the transposition procedures is abandoned. Because the nerve is not dissected free from its relatively vascular and fatty-cushioned bed, risks for nerve ischemia and injury to the distal muscular branches are avoided and the potential for cicatrix formation is diminished. The periosteum over the tip of the medial epicondyle is incised parallel to the ulnar nerve for 2-3 cm. There is no risk for postoperative flexor weakness as the flexor-pronator origin is not detached. Using a small periosteal elevator, the periosteum is removed off the posterior aspect of the epicondyle down to the floor of the ulnar groove and reflected over the nerve. The ulnar collateral ligament is not disturbed. A malleable ribbon retractor and the periosteum is used to cover and protect the nerve as the posterior aspect of the epicondyle is drilled down. This partial osteotomy of the medial epicondyle is performed with an air-powered microdrill with a burr bit. High-speed drills are not advised due to the risk of severe injury to the nerve if the drill bit deflects off the bone. The periosteum is reapproximated over the bony defect which is waxed only if significant bone bleeding occurs . Before skin closure the elbow is passively flexed and extended, closely observing the anatomic relations and movements of the ulnar nerve and the medial epicondyle. If flexion causes the nerve to easily slip anteriorly over the medial epicondyle, consideration is given to extending the surgery to include a transposition procedure. Only after hemostasis is assured, the wound closed using absorbable sutures in the subcutaneous and subcuticular layers and adhesive strips on the skin. The patient is discharged from the hospital on the first postoperative day. Postoperatively, the elbow is immobilized for 1 week in a well-padded long-arm splint long enough to also support the wrist. The patient is encouraged to use and exercise the hand as often as possible. After 1 week, the splint is removed during the day but replaced at night for an additional 2-3 weeks. Gentle range of motion exercises of the shoulder, elbow, and hand are prescribed. The patient is allowed to resume full activities 3-6 weeks after surgery. Advantages of the extended decompression with partial osteotomy are similar to those of the simple decompression. It is simple to perform, entails little manipulation of the nerve, and patients have shorter postoperative recovery periods. Unlike the simple decompression, the nerve is more fully explored and compression at other sites are more likely to be discovered and appropriately treated. Like the medial epicondylectomy, this technique relieves to some degree the tension on the ulnar nerve in elbow flexion by enlarging the ulnar groove. Unlike the medial epicondylectomy, the ulnar nerve retains the protective effect of the epicondyle and the ulnar groove. The attachment of the flexor-pronator group to the epicondyle does not require division. Friction neuritis from recurrent dislocation of the nerve is not a potential cause of postoperative failure as it is with the medial epicondylectomy technique. Advantages over the transposition procedures are the relative simplicity of the procedure, minimal manipulation of the ulnar nerve itself, and shorter recovery time. Disadvantages are (1) the potential for callus formation and subsequent nerve entrapment at the site of the partial osteotomy, and (2) risk to the ulnar nerve and ulnar collateral ligament from the proximate use of an air-powered drill.
Results of Surgery
Numerous and obvious difficulties are encountered when evaluating and comparing the results of different authors. A major difficulty is the lack of well-designed, controlled or randomized studies. The few studies which attempt to compare results are neither truly randomized nor prospective, do not have comparable control groups, and rarely use statistical analyses. None has been able to clearly demonstrate, in terms of outcome, an advantage of one surgical technique over another. Retrospectively comparing results of patients undergoing a particular operation is also difficult. Some series report a mixture of procedures. For example, in McGowan's report of 42 cases of anterior transposition, 25 underwent placement subcutaneously, 17 intramuscularly, and 4 submuscularly. This makes the interpretation of the outcome data tenuous. Other series may report results of one particular technique, but include in their patient population patients undergoing "re-do" operations. Lack of a widely accepted classification system for grading preoperative severity of symptoms and postoperative outcome also hampers attempts at retrospective review of large numbers of series. These series differ significantly with regard to the severity of symptoms of their respective patient populations, and with regard to the duration of symptoms. Definitions of excellent, good, fair, and poor results also vary widely. In one study, only 22 % of patients undergoing surgery by a variety of techniques had good results, while 54 % had fair results (defined as "little to no improvement, but not worsened"). Most surgeons would not consider "no improvement" as a fair result, but rather would classify it as a poor result or failure. Another study defined satisfactory outcome as "normal use of the hand and the patient's satisfaction with the results." Future studies would do well to use a well-defined standardized grading system such as that suggested by Dellon or by Gabel and Amadio. Personal biases are overtly present in a number of reports. Advocates of the lesser procedures profusely extol a number of disadvantages of transposition procedures, but fail to substantiate with clinical data an increased morbidity with these procedures. Conversely, the proponents of anterior transposition champion their procedures as having better results, although this contention has little scientific validity. Although simple decompression is one of the more widely used techniques in recent years, very little data regarding the outcome can be found in the literature. Advocates of the procedure claim equal efficacy to the transposition procedures, with much less risk and morbidity. Wilson and Krout reported good or excellent outcomes in 13 of 16 patients (81 %) undergoing simple decompression. Thomsen reported 32 decompressive procedures followed from 7 months to 5 years postoperatively; 16 resulted in complete alleviation of symptoms, while 12 resulted in improvement and 4 in no improvement. None experienced complications or deterioration. Results of medial epicondylectomy are more variable. Some surgeons reported good to excellent results in 45 % to 85 % of their patients. Complete resolution of symptoms and neurologic deficits occurred less frequently than in many series reporting outcome of transposition procedures. The best results were obtained in patients with early or mild symptoms. Poor outcomes, defined as those with no improvement or worsening, occurred in 0% to 32% of cases. Eversmann suggests the best indications for medial epicondylectomy may be recurrent subluxation of the nerve, cubitus valgus deformity, or an irritating nonunited medial epicondyle fracture with callus formation. Advocates of the anterior transposition, particularly those who use the subcutaneous technique, argue that this operation has been shown to most consistently relieve symptoms and has withstood the test of time. Transposition procedures clearly have certain advantages over the lesser procedures, but they also entail certain risks and disadvantages (Table 3). Most reports, unfortunately, combine the results of the different techniques of transposition. Perhaps the best results have been achieved by Leffert using the Learmonth (submuscular transposition) technique. More than half of his patients, including those undergoing "re-do" procedures, experienced complete resolution of all pain and neurologic deficits. Complications were "minimal" and no patients were worsened as a result of the operation. Likewise, Levy and Apfelberg performed three subcutaneous transpositions and seven submuscular transpositions to achieve a 60 % rate of excellent results, defined as complete resolution of symptoms. In most series, the results of the anterior transposition are similar to those obtained by simple decompression and medial epicondylectomy. The incidence of post-transposition failure or complications is not clear, Surgeons having poor results with this technique generally do not report their experiences. Some authors imply a high failure rate in their prior experiences with transpositions, leading them to adopt lesser procedures as the initial treatment of choice. In fact, the series reporting reoperation for failure of surgical therapy predominately consist of failed transposition operations. Although the literature suggests a slightly greater chance of symptom resolution after transposition procedures, especially in patients with more advanced disease, it also suggests a greater likelihood of postoperative worsening as compared to the lesser procedures. Perhaps the best indications for anterior transposition are failure of simple decompression to alleviate symptoms, recurrent subluxation of the ulnar nerve, persistent or progressive valgus deformity, and persistently positive elbow flexion test with severe neuritic signs with prolonged flexion of the elbow. The data regarding results of decompression or transposition followed by the ensheathing of the ulnar nerve in Silastic are sparse. There appears to be no added advantage to this procedure. I used the subcutaneous transposition technique for initial surgical treatment of cubital tunnel syndrome. However, the last 5 years an extended cubital tunnel release with partial osteotomy of the medial epicondyle became the procedure of choice. Based on the grading scale of Gabel and Amadio, no complications have occurred.
The course of the ulnar nerve from the extensor compartment of the arm across the elbow joint into the flexor compartment of the forearm lends itself to injury from a wide range of compressive, tractional, and frictional forces in the vicinity of the elbow. Subsequent damage to the nerve produces a neuropathic process known as the cubital tunnel syndrome. Characteristic symptoms are weakness and atrophy of the intrinsic muscles of the hand, and numbness and painful dysesthesias of the medial aspect of the hand. A number of surgical techniques have been designed to relieve entrapment of the ulnar nerve as it passes around the medial epicondyle of the elbow. They either remove the compressing agent or remove the nerve from its bed. Each procedure has its proponents. The efficacy and morbidity of any of the five basic techniques have not been shown to be significantly better or worse than any other.