A Review of Compressive Ulnar Neuropathy at the Elbow

Motor nerve conduction studies 

A patient with a suspected compression of the ulnar nerve at the elbow will have a stimulating cathode applied to 4 different points along the course of the ulnar nerve. The 4 standard points of stimulation are at the wrist, distal to the elbow, proximal to the elbow, and in the axilla.35, 36, 37, 38 The CMAP is recorded from one of the muscles innervated by the ulnar nerve; thus, the recordings will only assess the axons innervating that specific muscle. Obtaining a recording, most commonly, from the hypothenar muscles can test for ulnar motor nerve conduction. However, a recording electrode placed on the hypothenar muscles will not detect selective damage to the axons innervating either the flexor carpi ulnaris or first dorsal interosseous.34, 37, 38 Therefore, a recording electrode should be placed over the first dorsal interosseous and the flexor carpi ulnaris muscles because they can be differentially affected.39 The conduction velocity of the ulnar nerve is measured by comparing the differences in the distance and latency between sites of stimulation.34 Chronic compression of the ulnar nerve at the cubital tunnel will produce a localized narrowing of the axons distal to the cubital tunnel causing a slowing of conduction. Generally, this slowing of conduction is localized to the elbow, but in longstanding ulnar neuropathies, it may extend distally.37, 38

During this procedure, it has been advocated that the elbow be kept in a “moderately flexed” position, specifically, 70° to 90° from the horizontal.35 Moderate flexion provides the greatest correlation between surface skin measurement and true nerve length. In elbow extension, the skin distance is falsely short compared with true nerve length, causing spurious and artifactual conduction slowing. In addition, the length of an ulnar nerve segment used is important in the ability of a nerve conduction study to localize the site of compression. A 10- to 12-cm distance between stimulation above and below the elbow is used. Very-short-length segments are subject to a considerable amount of error in calculating conduction velocity because of inaccuracies in measuring latency and distance.40 Studying long-length nerve segments may mask focal slowing by including lengths of a normally conducting nerve. Ulnar nerve compression can be located at the elbow by using 2 criteria: (1) an absolute motor NCV from above the elbow to below the elbow of less than 50 m/s or (2) slowing of greater than 10 m/s in the above-the-elbow to below-the-elbow segment compared with the below-the-elbow to wrist segment41 (Fig 4).

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Fig 4. Representation of the ulnar nerve stimulated using electrodiagnostics at the elbow (E), below the elbow (BE), above the elbow (AE), and at the wrist (W).

In general, focal compressive entrapment neuropathies, such as cubital tunnel syndrome, can damage Schwann cells and cause focal demyelination. Demyelination can contribute to a significant reduction in the conduction velocity of an affected nerve. If the Schwann cells are damaged severely enough, as can occur with chronic compression of the ulnar nerve, action potentials may not propagate past the damaged region, resulting in a condition known as a “conduction block.” Conduction block at the elbow may be associated with focal slowing, due to marked axonal stenosis distal to the elbow, which can contribute to a slowing in the ulnar NCV.41 Slowing of NCV is directly proportional to the duration and severity of the compression.

Quantification of the area and the amplitude of the CMAP are important; they are proportional to the number of muscle fibers activated and provide an estimate of the amount of functioning present in the tested nerve and muscle.41, 42 On proximal stimulation of a compressed ulnar nerve at the elbow, there is a gradual reduction in the amplitude of the evoked response potential by 30% or more because of dispersion and increased duration of the response. However, the area of the evoked response stays relatively constant. The amplitude of the CMAP decreases as the synchrony of discharge of the contributing motor units decreases. If all axons conduct at the same velocity, the amplitude remains unchanged, but because they differ, slower conducting axons activate the muscle progressively later with more proximal stimulation. Because of this effect, the CMAP becomes longer and lower. If there is any reduction in the area of the CMAP at proximal sites of stimulation, it will be much less than the reduction in the amplitude, which results from the cancellation of negative components (ie, overlapping of positive components). A drop in amplitude of more than 20% across the elbow or an abrupt drop in conduction velocity likely represents a conduction block and possibly temporal dispersion indicative of focal demyelination.27, 41, 42, 43

In assessing amplitude reduction, the examiner must make sure that a “Martin-Gruber anastomosis” is not present. In this normal variation, some of the motor fibers destined for ulnar hand muscles travel with the median nerve at the elbow, cross over to the ulnar nerve in the forearm, and come into the hand via the ulnar nerve through the Guyon canal.44 Such crossover will lead to a larger ulnar muscle action potential from the wrist than from the elbow and might, therefore, produce a false amplitude reduction, better known as a “pseudoconduction block.”

Sensory and mixed conduction studies 

Sensory and mixed ulnar nerve conduction across the elbow may increase the yield of identifying focal slowing in patients with ulnar nerve entrapment at the elbow. Sensory conduction studies can be done either orthodromically and/or antidromically because the conduction velocity of the axons is the same in both directions. Stimulating the dorsal ulnar cutaneous nerve just below the ulnar styloid while recording an orthodromic SNAP can be done at one of the following sites: in the dorsal web between the fourth and fifth digits, the wrist, below the elbow, and above the elbow.45 On the other hand, an antidromic SNAP can be recorded over the fifth digit while stimulation can be applied over a mixed nerve at the following locations: the wrist, below the elbow, and above the elbow.45 The easiest and most reliable distal SNAP recordings for the ulnar nerve are obtained by orthodromic stimulation of its axons. Similarly, a mixed nerve potential can be recorded below and above the elbow by stimulating the mixed nerve at the wrist.45

There are several parameters in sensory conduction studies that can be useful in identifying the location of the compression of the ulnar nerve at the elbow. The nerve action potential is used to measure the amplitude, area, latency, conduction velocity, area, and amplitude, but are more difficult to measure because of configuration changes and small size. The amplitude and area of the SNAP provide information about the number of functioning axons and their respective sizes. Criteria for an abnormally low ulnar SNAP amplitude include an amplitude that is either less than 10 mV or less than 50% of the amplitude of the asymptomatic limb.45, 46 Low ulnar SNAP values seen in entrapment neuropathies, such as cubital tunnel syndrome, can be attributed to temporal dispersion, conduction block, severe axonal stenosis, and significant loss of large myelinated axons by focal demyelination.34, 37, 46 Conduction block, which is associated with entrapment neuropathies, is caused by processes that may also cause a loss of large myelinated axonal fibers and severe axonal stenosis seen in cubital tunnel syndrome resulting in a low SNAP amplitude in conjunction with a prolonged distal latency. A slowing of the SNAP across the elbow is another hallmark of ulnar nerve entrapment at the elbow. The reduced conduction velocity is because of a significant loss of large, myelinated, rapidly conducting fibers that also produce most of the SNAP amplitude.46

Inching technique 

An inching technique can be used to identify the exact location of the pathological compression of the ulnar nerve, which is imperative in determining the treatment protocol that should be used. Inching is performed by marking off 1-cm increments from 4 cm below the elbow to 6 cm above the elbow. The ulnar nerve is then stimulated using a submaximal current (10% to 25% supramaximal) while recording the activity of the abductor digiti minimi.45 An abrupt increase in latency of more than 0.4 to 0.5 msec and/or drop in amplitude of CMAP implies focal slowing. The inching technique has the potential to locate the site of entrapment of the ulnar nerve at any one of the following locations: (1) proximal leading edge of the arcade of Struthers; (2) distal length of the medial intermuscular septum; (3) entire arcade of Struthers, transversely attaching the deep fascia of the distal triceps and its tendon of insertion to the medial intermuscular septum; (4) Osborne ligament, forming the roof of the bony retrocondylar groove; (5) fascial origin of the flexor digitorum superficialis of the ring finger; and (6) confluence of the 2 heads of the flexor carpi ulnaris.

Needle EMG 

Needle electrode examination can be used in concert with nerve conduction studies to establish the severity and location of the compression of the ulnar nerve. The needle examination should check the following muscles for abnormalities: first dorsal interosseus, hypothenar muscles, abductor pollicis brevis, flexor digitorum profundus (digits 4 or 5), and flexor carpi ulnaris. If ulnar nerve–innervated muscles are abnormal, the examination should be extended to include non–ulnar nerve (C8 nerve root/medial cord/lower trunk)–innervated muscles to exclude a brachial plexopathy as well as the cervical paraspinal musculature to exclude radiculopathy. A compressed ulnar nerve characterized by a conduction block may show reduced motor unit potential recruitment. Where the axonal interruption occurs, positive sharp waves and fibrillations can be observed. The presence of abnormalities in the flexor carpi ulnaris or in the flexor digitorum profundus indicates a compression at or proximal to the elbow. On occasion, the flexor carpi ulnaris receives its innervation above the elbow. Thus, denervation of the flexor carpi ulnaris may be caused by a more proximal compression such as at the arcade of Struthers and/or medial intermuscular septum. In some cases, the flexor carpi ulnaris may be spared even when the ulnar division of the flexor digitorum profundus (digits 4 and 5) is abnormal. If significant axonal loss has occurred, with subsequent reinnervation taking place, polyphasic motor unit potentials with moment-to-moment variation in shape will be observed.47 In fact, increases in motor units action potential duration and amplitude indicate that reinnervation has already taken place.39, 47

Stage 1: Reduction of overload, pain, and inflammation 

Reduction of pain and inflammation is imperative before other significant range-of-motion or strengthening procedures are used. With respect to acute symptoms attributable to nerve injury, rest is essential. Rest decreases the inflammatory response around the nerve, as well as any eventual swelling, and may lead to resolution of symptoms. This can be accomplished with the help of a splint. In the acute inflammatory phase, a resting splint is used initially to rest the inflamed tissues to allow healing to begin. The splint's purpose is to position the ulnar nerve in the position of least pressure, to help promote healing. The key to splint design is to immobilize only the joints directly involved with the inflamed tissue, thereby preventing weakness and stiffness of nearby joints and allowing the greatest function.

Night splints are an excellent method of minimizing elbow flexion during sleep.51, 52 Night splinting is important because many individuals may inadvertently flex their elbows while sleeping. Splinting will minimize elbow flexion during sleep and sleeping prone with the arm curled around the pillow. Such splinting is important even if the patient is not experiencing any paresthesias at night.51 There is some discrepancy as to the angle of flexion during splinting. Nevertheless, it appears that splinting at night should occur with the elbow fixed between 30° and 45°.18, 51, 52 Additional methods of protecting the elbow at night include positioning a pillow between the patient's trunk and affected extremity, reversing an elbow pad to cover the antecubital fossa, or using a towel wrapped in a figure-of-eight around the elbow to restrict elbow flexion.51, 52

Only in severe cases of cubital tunnel syndrome is daytime splinting advised. The patient is usually fitted with a thermosensitive molded plastic splint that will ensure elbow immobilization during the day. Idler recommends applying the splint over the anterior aspect of the arm, positioning the elbow at 40° to 60°, and assuring that the straps do not cross the ulnar nerve at the cubital tunnel.52 The problem with daytime splinting is that it hinders the patient from freely doing various occupational and recreational activities. Consequently, because it is so inconvenient, if no improvement is evident within the first 3 to 4 weeks of this type of treatment, other options should be considered.

To protect the ulnar nerve from external pressures and frequent flexion posturing, there are several potentially effective solutions. The patient can be given an elbow pad that can be worn over the posterior medial aspect of the elbow to protect the ulnar nerve from direct pressure or trauma during the day.51 In the work environment, placing a pillow beneath the elbow at the desk will reduce external pressure on the nerve. The patient should avoiding resting the elbows on hard surfaces. When sitting, arms are not to be crossed, but rather the forearm of the symptomatic arm should rest supinated on the thigh.53 If extensive reading is done, a bookstand should be used, as well as adjusting the angle and height of the keyboard so that the elbows do not rest directly on the desk or chair.48 Furthermore, for patients whose occupation involves spending long hours on the telephone (eg, secretaries, receptionists, operators), the telephone should be held by the unaffected extremity or a headset can be used as an effective alternative.

Some health professionals suggest the use of nonsteroidal anti-inflammatory drugs, whereas others feel that these drugs has no clinical efficacy in treating this condition.17, 53, 54 In addition, use of steroidal injections for patients with cubital tunnel syndrome has been administered in the past; however, prolonged corticosteroid use has various negative side effects.52, 55 In a recent study conducted by Hong et al,55 splinting alone was compared with applying a local steroid injection in addition to splinting. The results showed that the addition of a steroid injection did not provide further benefit in the treatment of cubital tunnel syndrome. The splint application alone proved adequate in the improvement of symptoms and ulnar nerve conduction across the elbow. Furthermore, injection of a corticosteroid solution locally could possibly result in an intraneural injection or even a subcutaneous atrophy with fatty tissue necrosis.17

Treatment modalities for the reduction of pain and inflammation includes ice, ultrasound, and pulsed signal therapy, which are further discussed below. The region of modality application is generally directed over the most affected areas subjectively reported by the patient, as well as any area of palpable tenderness found during initial examination.

In the early part of immobilization, when pain and inflammation are at their greatest, icing or ice massage is recommended to the elbow area. During this period, which can be from 10 days to 6 weeks depending on the severity, patients are instructed to remove their splints twice daily to perform gentle passive range of motion exercises to the immobilized elbow joint to prevent stiffness and loss of range of motion.51 Although mobilization is recommended at this early stage of treatment, myofascial work should not be performed if inflammation is still present. The purpose of treatment during this first stage of treatment is to decrease some of the inflammation present. Myofascial work, particularly aggressive techniques, can hinder effective treatment of this condition. For this reason, myofascial work should be implemented in the third stage of treatment (see stage 3).

Ultrasound has shown effectiveness in chronic overuse syndromes, such as lateral epicondylitis, owing to its nonthermal effects, which include both cavitation and microstreaming.56, 57 Consequently, ultrasound may be beneficial in treating various other chronic overuse syndromes, such as cubital tunnel syndrome. Furthermore, it has been suggested that ultrasound can affect nerve conduction in normal nervous tissue and healing in damaged nerves.56, 58 A continuous beam of ultrasound can increase the sensory and motor conduction rate of a nerve, provided that the treatment took place under a low intensity and appropriate frequency.44, 58, 59, 60

Before administering ultrasound therapy, there are a number of factors that must be taken into consideration for the treatment to be effective. These factors include frequency, intensity, pulse regimen, duration, length, and frequency of treatment.61 In an experiment conducted by Hong et al, it was shown that an intensity of 0.5 W/cm2 and a frequency of 1.0 MHz increased the recovery rate of a compressed nerve in contrast to a dose of 1.0 W/cm2 of intensity with the same frequency, which slowed down the nerve's recovery rate.62 It has been suggested that if the intensity dose is too high, ultrasound can have damaging and proinflammatory effects.57 In addition, an appropriate coupling medium (eg, water, mineral oil, gel) is required to avoid any reflection of the ultrasonic energy at the air-tissue interface. When working with the elbow, if the elbow cannot be comfortably immersed in water, usually a water balloon can be used instead as the coupling medium. It is important to fill the balloon with degassed water (no air bubbles) followed by a thorough coating of the balloon with a gel coupling medium and firmly applying the balloon against the skin ensuring no air pockets are present.

Pulsed signal therapy is a noninvasive medical technology that involves directing a series of magnetic pulses through injured tissue and has been used to treat osteoarthritis, meniscus degeneration, injuries to the anterior cruciate ligament, neck whiplash syndrome, Achilles tendon injuries, and soft tissue injuries such as carpal tunnel syndrome. According to experimental data by Lin et al,63 pulsed electromagnetic fields can enhance blood flow at the area of injury. Because cubital tunnel syndrome does encompass a decrease in the neural microcirculation, theoretically, an increase in blood flow to the area may increase stimulation of the healing process. Patients who have not responded well to other conservative forms of therapy may consider pulsed signal therapy as an alternate choice.

Clinical signs that indicate the ineffectiveness of therapeutic modalities are (1) continued pain at rest or with light activity, (2) inability to tolerate light stretching/range-of-motion exercise, and (3) continued inability to perform submaximal exercises to increase strength.56, 62 If the above signs are present after a 2- to 3-week period of initial modality application, the clinician should consider reevaluating the patient and/or modifying the treatment plan.

Stage 2: Promotion of total arm strength and normal joint arthrokinematics 

Weaning from the supportive splints begins when immobilization has accomplished the goals of reducing inflammation and pain proximal and distal to the medial epicondyle. The patient removes the splints initially for submaximal exercise sessions. Gradually, the splint is removed for light daily activities in addition to exercise sessions, then progressing to night wear, and finally to splint wear as needed to prevent pain with strenuous activity.

Integration of range of motion and general upper extremity flexibility is gradually performed during the initial stage of rehabilitation. Aggressive end-range passive stretching and mobilization are not indicated at this time.64 Maintenance of pain-free elbow, forearm, wrist, and finger motion is the goal in this stage. In addition, stretching the shoulder musculature is applied to prevent loss of range of motion in the proximal structures, especially during this period of either modified activity or rest. Mobilization and passive stretching are also performed to normalize length tension relationships of the flexor/pronator musculature and promote the reattainment of elbow extension (ie, the position of osseous congruency and stability).64, 65, 66, 67

Aggressive stretching is not advocated during this period of the rehabilitation program. If the injured elbow exhibits a significant range of motion limitation compared with the uninjured elbow, joint distraction and mobilization to enhance ulnohumeral extension are recommended during this stage. Placing the elbow in a greater amount of extension with subsequent distraction application will be limited by tension in the anterior capsule and anterior ligamentous structures, resistance of the flexor muscles, and the tip of the olecranon entering the olecranon fossa but will enhance elbow extension range of motion.66, 67, 68

A technique for posterior gliding of the ulna on the humerus may also be used to increase extension range of motion.66 The edge of the treatment plinth or rubber edge can be used as a fulcrum for the distal aspect of the humerus as the clinician glides the ulna in a posterior direction relative to the humerus. The amount of elbow extension range of motion used during mobilization dictates the amount of stress imparted to the anterior capsular structures. The 30° angulated alignment of the distal humerus and sigmoid notch is an important anatomical relationship for the clinician to understand to ensure proper direction of force application during mobilization.66 Medial and lateral gliding of the ulna relative to the humerus is reported as the mobilization of choice to increase overall joint play necessary for full elbow extension range of motion.65 This technique should be used with caution in the throwing athlete and only performed in the presence of significant joint hypomobility because of possible stresses imparted to the ulnar collateral ligament complex. A true medial and lateral gliding motion of the ulna on the humerus with the forearm supinated is performed with either a varus or valgus movement. Stabilization of the distal humerus is performed by grasping both humeral epicondyles with the olecranon supported in the palm of the clinician's stabilizing hand.66 Varying degrees of elbow extension and flexion are recommended, with application of this mobilization technique near the current limits of elbow extension.

However, in most cases of overuse injury, only active assisted and passive stretching of the elbow, forearm, and wrist using intensities well tolerated by the patient are necessary to return to normal bilaterally symmetrical motion to the injured extremity.66 Active assisted and passive stretching, using several repetitions and hold duration of 15 to 30 seconds, are indicated to produce a plastic deformation of the muscle tendon unit.69 A supine patient position is recommended to enhance the clinician's ability to perform combined patterns of elbow, forearm, wrist, and finger movements relative to the glenohumeral joint and trunk.

Submaximal strengthening exercises are introduced as signs and symptoms allow. A firm handshake can be used as a criterion for determining whether a patient is ready for early exercise in the treatment program.64 The initial goal of rehabilitation, with respect to the muscle tendon unit, is the promotion of muscular endurance and improved resistance to repetitive stress.65 To accomplish this goal, extremely low or no resistance is used with high repetition formats of 20 to 40 per set.65 Such high repetitions have 2 important effects; first, it promotes local muscular endurance, and second, it provides a vascular response to the exercising tissues. Total arm strength exercises are used for the scapulothoracic and scapulohumeral musculature, with resistance applied in a manner that does not either produce undue valgus stress or attenuate the ulnar nerve. Isokinetic exercises are used later in this second rehabilitation stage.

Progression to resistive exercise from the initial stage of isometrics and manual resistance is recommended during the second stage. The modes of resistive exercise followed in the rehabilitation of overuse injuries, as outlined by Davies,70 are multiple-angle isometrics, manual-resistance isotonics, isotonics (concentric and eccentric emphasis), and finally isokinetics. A low-resistance, high-repetition format is used to increase not only strength but local muscular endurance as well. Strengthening exercises for the proximal aspect of the upper extremity kinetic chain are added during this stage. Rotator cuff strengthening exercises are used to promote proximal muscular balance and strength.

Additional exercises using low resistance levels and multiple repetitions are used during this stage of rehabilitation. Surgical tubing is used for concentric and eccentric muscular strengthening of the elbow flexors and elbow extensors. Exercises involving the upper extremity where the distal member of the extremity is fixed during exercise (known as a “closed-chain” state) are also used during this stage. The extremity is placed so that the elbow is in a comfortably extended position over a large, inflatable ball, with the extremity bearing progressive amounts of weight into the ball. As with any closed-chain exercise, this position causes co-contraction of the musculature surrounding multiple joints via multiple joint axes.66, 71 Clockwise and counterclockwise circles of various sizes are performed by the patient, as well as crosslike patterns and diagonals.

The use of plyometric exercises is recommended in the later stages of total arm strength phase of rehabilitation.72, 73 These exercises are characterized by an eccentric contraction of a muscle followed immediately by a concentric contraction of the same muscle group. The concept or principle behind the plyometric exercise is that stretching of the series elastic components of the muscle and activation of the stretch reflex from the eccentric muscular contraction during the lengthening phase of the exercise enhances the subsequent concentric or shortening response of the muscle.72

Stage 3: Interval return to full activity 

Evaluation of the patient for a return to full activity includes specific assessment of upper extremity range of motion and strength. A full pain-free range of motion in the elbow, forearm, and wrist is required before the patient can be considered an optimal candidate for return to full activity. Assessment of strength using isokinetics, if available, or manual muscle testing is also recommended in the comprehensive evaluation. Appropriate levels of strength compared bilaterally, as well as normal balance of the unilateral muscle ratios, are expected before a functional return is recommended. A handgrip dynamometer is also used as a gross strength measure for bilateral comparison. Generally, a greater emphasis is placed on isokinetic test results as opposed to either handgrip dynamometers or manual assessment because of the dynamic nature of the isokinetic test and degree of objectivity.71 Competitive athletes should rehabilitate the previously injured elbow at a high-speed contractile activity before returning to competition.

Manual soft tissue techniques such as active-release technique, nerve gliding, Nimmo technique, and scar modification can be helpful if performed by a therapist trained in these specific techniques. Constant repetitive motions can result in the formation of fibrous adhesions among muscles, fascia, and peripheral nerves.74 Consequently, such techniques were developed to treat and resolve repetitive strain injuries.75 These methods of treatment consist of applying both manual pressure and tension directly over an adhesion site. Although these soft tissue techniques can prove to be painful at times, application of heavy pressure promotes the healing process to a greater degree than light or moderate pressure.76 However, it is important to respect the patient's pain threshold. Excessive pain will cause the patient to become tense, contract the muscle further, leading to an ineffective treatment.75 Furthermore, such soft tissue techniques should not be used directly over neurovascular structures because of the constant deep pressure applied, which may result in bruising.74, 75, 76 Thus, this method of treatment might not be appropriate for some of the entrapment sites; however, it may prove effective for other entrapment sites of the nerve at the elbow such as its exit point between the 2 heads of flexor carpi ulnaris or other musculotendinous causes of entrapment.

Stage 4: Maintenance 

The goals in the maintenance phase are to continue to increase the strength, power, and endurance of the upper extremity musculature by initiating an interval training program (phase 1) specific to the individual's sport or activity, while subsequently continuing to emphasize strengthening of the elbow and wrist.77 The type of interval return program designed is specific to the activity the individual is involved in. Consequently, the program will vary from one activity, or sport, to the next.

An interval throwing program is designed to gradually return motion, strength, and confidence in the throwing arm of a baseball player after injury or surgery by slowly progressing through graduated throwing distances. Furthermore, the interval throwing program is designed so that each level is achieved without pain or complication before the next level is started. This sets up a progression where a goal must be achieved before advancement. Because of this design, the interval throwing program may be used for different levels of skill and abilities, from those in high school to those in professional levels. The critical factor although is throwing mechanics. Regardless of the level of competition of the athlete, proper throwing mechanics through the program must be followed at all times.66

Simultaneously, the athlete should be supplementing the interval throwing program with both stretching and strengthening routines. Throwing involves all muscles in the body; thus, all muscle groups should be stretched before throwing. This should be done in a systematic fashion beginning with the legs and including the trunk, back, neck, and arms.

Continuation of conservative treatment should take place even after symptoms have subsided. There is some speculation as to how long conservative treatment should be adhered to ranging from a minimum of 90 days to up to 1 year.25, 78 Nevertheless, if there is a continual ulnar nerve instability, distal neural symptoms, and/or pain that limits performance despite a comprehensive nonoperative rehabilitation program, the patient is most likely a candidate for surgical intervention.

Simple decompression 

Simple decompression of the ulnar nerve employs the use of a longitudinal incision approximately 6 to 8 cm long just anterior to the medial epicondyle.7, 79, 80 The medial epicondyle is exposed, allowing identification of the ulnar nerve proximally. The nerve is released proximally as it passes through the medial intermuscular septum. A portion of the medial intermuscular septum is released from its attachment to the medial epicondyle to prevent kinking or compression of the ulnar nerve in elbow flexion.80 The cubital tunnel retinaculum and flexor carpi ulnaris aponeurosis is divided, which allows for simple decompression “release” of the ulnar nerve at the elbow. There is commonly a second constricting fascial band deep within the substance of the flexor carpi ulnaris, 1 to 2 cm distal to the proximal fibrous arcade that must be released. Next, the portion of the ulnar nerve under the medial epicondyle is frequently compressed and must be released by dissecting it free from the overlying aponeurosis7 (Fig 5).

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Fig 5. Simple decompression. Reprinted with permission from Kleinman.104

Postoperative subluxation of the ulnar nerve over the medial epicondyle with full passive elbow flexion has been reported as a statistically significant cause of failure of simple decompression of the ulnar nerve. The ligamentous band between the epicondyle and the olecranon should not be released. If this ligament is cut, the ulnar nerve should not be released from its posterior attachments to avoid subsequent subluxation.80, 81 If the ulnar nerve continues to be compressed or subluxated over the medial epicondyle during passive elbow flexion, the remainder of the cubital tunnel is released and a medial epicondylectomy is performed. There have been some surgical modifications made to cubital tunnel decompression procedures, such as the use of endoscopic assistance, which allows the surgeon to visualize the ulnar nerve in relation to its potential sites of compression.80

Simple cubital tunnel decompression has numerous associated advantages. The relative simplicity, safety, and predictability of the procedure allows postoperative rehabilitation to begin immediately, inevitably resulting in an average “return-to-work interval” of 20 workdays.80 This is less than one third that reported for anterior transposition, and it does not disturb the vascularity of the ulnar nerve as much as anterior transposition.79 Finally, in situ decompression avoids subluxation of the ulnar nerve as is frequently seen after simple release.

Disadvantages associated with simple decompression include the predisposition of the ulnar nerve to recurrent dislocation after extensive release and a high recurrence rate when the surgeon cannot locate the site of compression.80 In addition, this method does not deal with nerve compression resulting from lesions underlying the ulnar nerve such as ganglion, severe cubitus valgus, bone fragment, or osteophyte. Recently, it has been reported by Gelberman et al6 that simple release of the aponeurotic roof of the cubital tunnel does not modify the increase of intraneural pressure induced by elbow flexion. Simple decompression is best suited for the following patients: ones that exhibit mild symptoms due to a mild compression of the ulnar nerve; patients with preoperative evidence of subluxation of the ulnar nerve; and patients with abnormal electrodiagnostic studies defined by the inching technique, but with normal or only mildly abnormal nerve conduction velocities across the 10-cm elbow segment.5, 81

Anterior transposition 

Anterior transposition surgical procedures can be grouped into 3 classes, depending on the location of the transposed ulnar nerve: subcutaneous anterior transposition,9 submuscular anterior transposition,82 and intramuscular anterior transposition.10, 83 All transpositions remove the ulnar nerve from the compressive effects of the ulnar groove and cubital tunnel retinaculum, and by placing it anterior to the axis of motion of the elbow, they decrease tension and pressure on the nerve during flexion.

Disadvantages of anterior transposition of the ulnar nerve include the risk of denervating the flexor carpi ulnaris muscle and disruption of the nerve vasculature during dissection.84, 85 Potential complications that may arise when moving the ulnar nerve away from its natural bed include symptoms produced with elbow extension, subluxation back to the original position, fascial slings causing new sites of entrapments, kinking of the ulnar nerve proximally and distally, scarring in the muscle channel, injury to the flexor carpi ulnaris motor branches, perineural fibrosis from transfer to a relatively hypovascular bed, perineural fibrosis from intraneural injury, devascularization of the ulnar nerve, and elbow contracture from immobilization.84, 85, 86 The worst of all complications is the failed submuscular transposition, in which there is often an extraordinary degree of fibrosis with resultant severe and permanent neurological defect.84 Immobilization, together with transposition, may result in new compression sites. In addition, elbow contracture may occur following elbow immobilization. Patients with longstanding cubital tunnel syndrome, pronounced symptoms, posttraumatic conditions of the elbow, a subluxating ulnar nerve, scarring around the nerve, space occupying lesions, or those with no obvious site of compression at the time of the surgery are better served by procedures that transpose the ulnar nerve.

Subcutaneous transposition 

Subcutaneous transposition of the ulnar nerve was first described by Curtis87 in 1998 as releasing the ulnar nerve from all potential sites of entrapment and moving it anterior to the motion axis of the elbow, thereby relieving tension. Anterior subcutaneous transposition of the ulnar nerve consists of a longitudinal incision made posterior to the medial epicondyle extending several centimeters proximal and distal to the condyle.77 The ulnar nerve generally is identified where it enters the cubital tunnel and is dissected from the cubital tunnel and from between the humeral and ulnar heads of the flexor carpi ulnaris. This is accomplished by splitting the flexor carpi ulnaris aponeurosis, which allows the freeing of the ulnar nerve from the epicondyle. The mobilized ulnar nerve is transposed superficially to the flexor pronator muscle.54, 88 Maintaining the ulnar nerve in the anteriorly transposed position is essential in this surgical procedure. In fact, some surgeons advocate using a fasciodermal sling to maintain the transposed anterior position of the ulnar nerve preventing it from falling back posteriorly.9 The most common approach in creating a fascial sling is to suture the subcutaneous layer directly to the flexor-pronator fascia, medially to the transposed nerve, using 2 or 3 absorbable sutures9 (Fig 6).

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Fig 6. Subcutaneous anterior transposition. Reprinted with permission from Kleinman.104

Failures in subcutaneous transposition have most commonly resulted from incomplete immobilization, therefore, it is imperative that the elbow be held in a slightly flexed position for approximately 14 to 21 days to allow for healing to take place.7 However, immediate mobilization of the ulnar nerve has been shown to significantly reduce the period in which the patient returns to work, thus, periodically, it would be beneficial to put the elbow through a pain-free range of motion.89 Subcutaneous transposition of the ulnar nerve with fasciodermal slings has shown to lead to a higher degree of patient satisfaction and relief of symptoms.

Subcutaneous transposition avoids detaching the flexor pronator muscle from its origin, thus placing it at a distinct surgical advantage over submuscular transposition for the throwing athlete.16 Risks specific to subcutaneous transposition include devascularization of the ulnar nerve, potential creation of other areas of impingement by altering the course of the ulnar nerve, possible subluxation of the ulnar nerve behind the medial epicondyle causing a recurrence of symptoms, the surgical incision may damage the posterior branch of the medial antebrachial cutaneous nerve leading to further distressful or painful paresthesias.90

Submuscular transposition 

Submuscular transposition was first described in 1942 by Learmonth91 and involves an incision centered over the cubital tunnel between the medial epicondyle and the olecranon process. The ulnar nerve is identified proximal to the cubital tunnel, and is traced proximally to the arcade of Struthers. Distally, the nerve is dissected between the 2 heads of the flexor carpi ulnaris muscle. It is very important to preserve the perineural vascular network to minimize devascularization of the nerve when it is transposed to its new position.92 Distal to the cubital tunnel, motor branches supply the flexor carpi ulnaris and flexor digitorum profundus muscles and must be preserved. If these come under undue tension during anterior transposition, intraneural dissection is used to facilitate anterior transposition. The medial intermuscular septum should be excised to prevent subsequent kinking of the ulnar nerve in its new position. In the proximal extent of the incision, the ulnar nerve pierces the medial intermuscular septum.92 The fascial band must be identified and released to prevent subsequent compression of the nerve. Approximately 1 cm distal to the medial epicondyle, the flexor-pronator origin is divided and the ulnar nerve is then transposed anteriorly to rest adjacent and parallel to the median nerve. When the ulnar nerve is transposed anteriorly, the flexor pronator muscle is dissected from the medial epicondyle, allowing the nerve to be placed beneath the flexor pronator muscle. The flexor-pronator muscle origin is then repaired. Postoperatively, the elbow is held in a flexed and pronated position for 3 weeks, allowing the flexor pronator muscle to heal completely.81 However, Siegel92 encourages early range of motion of the elbow and forearm within a few days of the surgery. Strengthening of the forearm muscles should begin approximately 6 weeks after surgery (Fig 7).

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Fig 7. Submuscular anterior transposition. Reprinted with permission from Kleinman.104

The advantages of submuscular transposition include removal of all potential entrapment structures and ability to place the ulnar nerve in a well-vascularized intermuscular bed, to prevent the ulnar nerve from undergoing kinking at the point where the nerve enters the flexor carpi ulnaris, to prevent the ulnar nerve from drifting, and to protect from external compression.92, 93, 94 The disadvantages of this procedure are medial epicondylitis, a longer recovery time because of healing of the flexor pronator origin, and possible nerve entrapment by a reattached muscle mass.84, 95 Flexion contracture is a rare complication following cubital tunnel surgery but when it does occur, it usually follows submuscular transposition.95, 96

Intramuscular transposition 

In intramuscular transposition, the ulnar nerve is placed in a tunnel inside the flexor-pronator muscle and was first described by Adson84 in 1918. This surgical procedure consists of transposing the ulnar nerve anteriorly and forming an intramuscular bed using a 5- to 10-mm-deep incision along the flexor-pronator muscle just distal to the medial epicondyle in line with the transposed ulnar nerve.97 The ulnar nerve is identified proximally, posterior to the medial intermuscular septum, and distally, through the fascia overlying the 2 heads of the flexor carpi ulnaris. The ulnar nerve is followed distally beneath the flexor carpi ulnaris to ensure its free mobility. Failure to release the fibrous deep flexor-pronator aponeurosis between the ring finger superficialis muscle belly and the flexor carpi ulnaris may result in ulnar nerve compression in its transposed position.93, 94 The proximal border of the pronator teres fascia and medial intermuscular septum from the middle of the humerus to the elbow are excised so that the ulnar nerve can be transposed anteriorly. After the ulnar nerve has been transposed inside the flexor pronator muscle, the fascia is closed avoiding any constriction or epineural adherence. This closure is easiest with the elbow held in a slightly flexed position and the forearm pronated at 45°.96

After surgery, the arm is kept in a long dressing, with the elbow fixed at 90° and forearm in midpronation for 3 weeks. Active range of motion begins at 3 weeks, whereas passive range of motion, if needed, is begun at 6 weeks, along with strengthening programs. Most patients with jobs that require manual labor are able to return to work at 8 weeks and resume full activity without restrictions by 10 weeks.10 Reported surgical failure in the intramuscular transposition has been attributed to either adhesion formation between the ulnar nerve and other fibrous anatomical structures around the elbow (remote from the intramuscular site) or to dense scarring10, 94, 96 (Fig 8).

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Fig 8. Intramuscular anterior transposition. Reprinted with permission from Kleinman.104

Medial epicondylectomy 

This surgical technique was first described in 1950 by King and Morgan.98 Medial epicondylectomy removes the major mechanical compressive factor in the cubital tunnel and allows anterior transposition of the ulnar nerve with considerably less dissection of the nerve than is required in the standard anterior transposition.8 An incision 12 to 15 cm long is made centered over the medial humeral epicondyle. The superficial surface of the ulnar nerve is exposed by incising the fascia and dividing the arcuate ligament. The origins of the flexor carpi ulnaris are identified and the arcade is incised at the cubital tunnel. The entire medial epicondyle is then exposed after the flexor pronator origin is detached from the epicondyle and is reflected distally. The medial intermuscular septum is excised for a few centimeters proximally.99 The epicondyle is then removed by aligning a 2.5-cm osteotome along the medial margin of the trochlea, which provides a useful natural guide. After removal of the epicondyle, the margins are smoothed with a rongeur and the raw cancellous surface is covered with bone wax. Removing the medial epicondyle excises the major bony block causing compression of the ulnar nerve, allowing it to migrate anteriorly without the necessity for its increased dissection and mobilization required for anterior transposition. The flexor pronator origin is reattached with the elbow in extension by closing the soft tissue envelope that previously enclosed the epicondyle, allowing the nerve to slide anteriorly in a superficial position. If any tension remains in the ulnar nerve after moving the elbow through a range of motion, the aponeurosis of the flexor carpi ulnaris must be divided further distally. A subcuticular closure is done and a soft compressive dressing is applied. No splint is required and early active motion is encouraged 14, 100 (Fig 9).

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Fig 9. Medial epicondylectomy. Reprinted with permission from Kleinman.104

The major advantage of medial epicondylectomy is that it requires less dissection and mobilization. Therefore, there is a better preservation of blood supply to the ulnar nerve when compared with anterior transposition. Medial epicondylectomy has numerous other advantages associated with it such as complete release or removal of constricting structures (including the arcade of Struthers, roof of the cubital tunnel, fascia overlying the heads of the flexor carpi ulnaris, and the medial epicondyle), more thorough decompression than simple in situ release, support of early postoperative elbow mobilization, which leads to a faster recovery, and preservation of small proximal nerve branches that might be sacrificed in anterior transposition procedures.99

Numerous potential problems that have been reported in using medial epicondylectomy in treating compression of the ulnar nerve at the elbow include tenderness at the osteotomy site, weakness in pronation and flexion seen in the postoperative period, and medial instability of the elbow caused by operative injury to the medial collateral ligament and medial epicondylitis.8, 101 This procedure should not be considered for athletes who engage in throwing motions, such as baseball, because it allows greater anterior migration of the ulnar nerve with elbow flexion, which could be detrimental to the integrity of the nerve.

Postoperative rehabilitation 

The patient is immobilized in a posterior splint or hinged elbow brace to allow the soft tissues to heal and to provide limited motion of the elbow in a safe and neutral range of motion. During the first postoperative week, the patient's brace is set from −30° of extension to 100° of elbow flexion. Selective distal range of motion is performed into forearm pronation and wrist flexion, with guarded wrist extension and forearm supination to protect the flexor-pronator origin. Gentle isometric exercises with extremely light resistance levels are applied to prevent disuse atrophy. Foam balls or putty squeezing are also used.

During week 2, range of motion is progressed to −15° of elbow extension and 120° of elbow flexion. Gentle manual resistance and distal strengthening patterns, using little or no weight, are applied as tolerated. During week 3, the immobilizer is opened to allow full range of motion with continued use of light isotonic strengthening using patterns identical to those presented for nonoperative rehabilitation of ulnar neuropathy. Range of motion of the glenohumeral joint continues throughout the rehabilitation to prevent contractures from disuse. During week 6, isotonic shoulder and scapular strengthening exercises are introduced, with resistance being applied proximal to the elbow to prevent excessive stress across the elbow.

Isokinetic wrist and forearm exercise is initiated at 10 weeks with progression to interval sport/activity return programs by week 12. An isokinetic evaluation is performed at this time to formally assess strength of the wrist and forearm musculature. A shoulder isokinetic evaluation is also performed to assess more proximally the relative strength and balance of strength before performing interval sport/activity return programs.