Ulnar Neuropathy Treatment & Management

Nonsurgical therapy may be helpful in many cases of ulnar neuropathy. If conservative therapy fails, surgical treatment is warranted, typically involving one of the following procedures ^{[141, 145, 146, 147, 148, 149, 150]} :

• Decompression in situ

• Decompression with anterior transposition (subcutaneous, intramuscular, or submuscular) 

• Medial epicondylectomy

More specifically, indications for surgery for ulnar nerve entrapment include the following:

• No improvement in presenting symptoms after 6-12 weeks of conservative treatment

• Progressive palsy or paralysis

• Clinical evidence of a long-standing lesion (eg, muscle wasting or clawing of the fourth and fifth digits)

If a fracture of the hook of the hamate is noted in the wrist, cast immobilization or splinting is required for 4-6 weeks. Surgery is indicated if symptoms progress during this time. On the other hand, as swelling subsides, pressure on the nerve may diminish, and symptoms may disappear. Nonsteroidal anti-inflammatory drugs (NSAIDs) are also valuable for reducing swelling in the tunnel.

Depending upon etiology, symptoms, and signs, referral to a neurosurgeon, hand surgeon, pain specialist, internist, physiatrist, rheumatologist, occupational therapist, or alternative medicine specialist may be appropriate.

Follow-up after surgery for ulnar nerve entrapment should occur at 1 month, 3 months, 6 months, and 1 year.

With appropriate decompression performed on time, the result of surgery for ulnar nerve entrapment should return to normal function. If decompression in situ is performed appropriately, a return to normal function is almost immediate. With the transposition of the nerve following decompression, postoperative immobilization, and the rehabilitative process, 3-6 months may pass before the patient regains normal function. ^[151]

The surgical outcome is less specific in chronic palsy (lasting > 3-4 months) associated with pain, muscle weakness, or atrophy. The duration of entrapment and the severity of numbness and muscle weakness influence the prognosis. In these chronic cases, improvement may be limited or absent after decompression and transposition but can halt further progression with proper decompression.

An essential pitfall in treatment is to lead the patient to believe that full recovery can be expected in cases where recovery is uncertain. Of course, few doctors today promise perfection, and physicians often downplay the likelihood of complete recovery so as not to raise expectations. Even so, many physicians, neurologists, and physiatrists do not realize that an operation for ulnar entrapment has much less chance of a highly satisfactory result than an operation for carpal tunnel syndrome. The reason for this is unclear.

Medical and other nonsurgical treatments can significantly help in cases of ulnar neuropathy. Conservative measures are most likely successful when paresthesias are transient and caused by malposition of the elbow or blunt trauma. Vasculitic and metabolic causes can be evaluated and diagnosed to facilitate the treatment of the underlying condition.

The physician can address pain or other sensory symptoms by trying various pain medications, including the following:

• NSAIDs

• Tricyclic (and related) antidepressants

• Anticonvulsants

• Narcotics (generally considered to be a last resort)

Oral vitamin B-6 supplements may be helpful for mild symptoms. Depending on patient response, this treatment should be carried out for 6-12 weeks.

Occupational therapy and work-hardening programs are also beneficial. Therapists may use and design splints to restrict the range of joint motion and cushions to alleviate pressure effects. ^[152] They may also use nerve gliding, sliding, or tensioning exercises to promote the nerve's smoother movement within the cubital tunnel and reduce adhesions and other causes of physical nerve compression. ^[153]

With nonoperative treatment, strengthening the elbow's flexors and extensors both isometrically and isotonically within 0-45° of range of motion is helpful. To avoid ulnar nerve impingement in the cubital tunnel, limit the elbow motion arc to an extended range. ^{[154, 155]} The patient should be advised to decrease repetitive activities that may exacerbate symptoms. In addition, the ulnar nerve should be protected from prolonged elbow flexion during sleep and saved during the day by avoiding direct pressure or trauma.

For initial conservative treatment of cubital tunnel syndrome, an elbow pad or night splinting for a 3-month trial is recommended. ^{[156, 157]} If symptoms do not improve with splinting, daytime immobilization for three weeks should be considered. Surgical release may be warranted if the symptoms do not improve with conservative treatment. If the symptoms improve, conservative treatment should be continued for at least six weeks beyond symptom resolution to prevent a recurrence.  ^[158]

For mild cubital tunnel symptoms, a reversed elbow pad that covers the antecubital fossa rather than the olecranon helps remind the patient to maintain the elbow in an extended position and avoid pressure on the nerve. At night, a pillow or folded towel may be placed in the antecubital fossa to keep the elbow in an extended position. Another option is to apply a commercial soft elbow splint, with a thermoplastic insert, for persistent symptoms.

For constant pain and paresthesia, one should consider using a rigid thermoplastic splint positioned at 45° of flexion to decrease pressure on the ulnar nerve. Initially, patients should wear this splint at all times; as symptoms subside, they can wear it only at night.

Patient education and insight are essential. Resting on elbows at work, using elbows to lift the body from the bed, and resting elbows on car windows while driving all are causes of paresthesia that can be corrected without surgical treatment. Patient education, anterior elbow extension splinting (if necessary), and correction of ergonomics at work should correct these transient palsies.

A randomized, controlled study of conservative methods to treat mild and moderate ulnar neuropathy at the elbow indicated that simply giving patients information about how to avoid injuring the ulnar nerve by preventing or reducing movements or positions that compromise the nerve led to significant symptomatic improvement. ^{[98, 159]} It is noteworthy that in this study, adding splinting or nerve-gliding treatments to the program of providing information did not yield a significant further benefit.

Suppose nonsurgical methods fail and the patient has severe or progressive weakness or atrophy. In that case, specific surgical techniques (eg.decompression in situ, decompression with anterior transposition, and medial epicondylectomy) are often beneficial in ulnar neuropathy at the elbow. ^{[160, 161]} Entrapments in the canal of Guyon are also amenable to surgical treatment. ^[1] Surgery is also valuable for correcting or stabilizing traumatic injuries, resectioning masses or cysts, and sectioning fibrous bands.

Appropriate blood work, chest radiography (if indicated), and a careful clinical examination are required (see Presentation and Workup). Next, the surgical preparation of the affected extremity from fingers to neck is indicated. It is followed by the application of a tourniquet, if necessary.

Indications for ulnar nerve decompression in situ at the elbow are as follows:

• Mild ulnar nerve compression

• Documented mild slowing on electromyography (EMG) as the ulnar nerve passes into and through the proximal flexor carpi ulnaris

• Absence of pain around the medial epicondyle

• Nerve that does not sublux with elbow flexion

• Normal osseous anatomy and epicondylar (ulnar) groove at the elbow and findings at surgery that is consistent with compression under the fibrous arcade ^[162]

Indications for ulnar nerve decompression with anterior transposition include the following:

• Unsuitable bed for the nerve secondary to the presence of osteophytes

• Tumor

• Ganglion

• Accessory anconeus epitrochlearis

• Heterotopic bone

• Significant bursal tissue or other mass

• Significant tension on the ulnar nerve as indicated by a positive elbow flexion test result or symptoms aggravated by activities requiring flexion

• Subluxation of the ulnar nerve with elbow flexion

• Deformity at the elbow secondary to a valgus elbow or a tardy ulnar palsy ^{[163, 3]}

• Valgus instability at the elbow

Indications for medial epicondylectomy include the following: ^{[164, 165]}

• Nonunion of an epicondyle fracture with ulnar nerve symptoms (best indication)

• Poor bed for the ulnar nerve in the epicondylar groove

• Ulnar nerve subluxation

Contraindications for the various operative procedures used to decompress the ulnar nerve are as follows:

• Decompression in situ - This procedure should not be used in cases of severe posttraumatic neuropathy with scarring, chronic subluxation, or dislocation of the ulnar nerve from the epicondylar groove and soft-tissue masses in the epicondylar groove

• Decompression with anterior subcutaneous transposition - This procedure does not release the ulnar nerve completely, leaving the distal course from the cubital tunnel as a possible site of compression; thus, it may not be the best choice for transposition in a thin person who lacks significant adipose tissue at the site of transposition, because of the possibility of repeated trauma to the nerve at the elbow ^[19]

• Decompression with anterior intramuscular transposition - This is the most controversial of the procedures because of the claim of severe postoperative scarring

• Decompression with anterior submuscular transposition - This procedure is contraindicated in the presence of scarring of the joint capsule or irregularity of the elbow joint due to malunited fracture, severe arthritis, or previous excisional arthroplasty

• Medial epicondylectomy - This procedure is not used when double-crush syndrome with entrapment at the distal end of the cubital tunnel or soft-tissue masses in the epicondylar groove is suspected

A Cochrane review examined two meta-analyses of five randomized, controlled clinical surgery trials for idiopathic ulnar neuropathy at the elbow, ^[98] four of which compared simple decompression with decompression plus transposition. ^{[166, 167, 168, 169]} These studies found no significant difference between simple decompression of the nerve and decompression with either submuscular or subcutaneous transposition.

The inability to detect a significant difference between simple decompression and transposition decompression is applied to clinical outcomes and neurophysiologic outcomes (ie, nerve conduction studies and EMG). ^[98] However, one difference between the two surgical approaches was that decompression with transposition produced more superficial and deep wound infections.

Two additional meta-analyses, using somewhat different methods, were also unable to find any significant differences between the outcomes of simple decompression and those of decompression plus transposition. ^{[141, 170]} However, one of these studies detected a trend in favor of decompression plus transposition, and the authors raised the possibility that a more highly powered study might be able to detect a difference. ^[141]

The previous Cochrane review also examined one study that compared medial epicondylectomy with decompression plus anterior transposition. It concluded that it could not find significant differences concerning clinical or neurophysiologic outcomes. ^[98] However, patient satisfaction was higher in patients treated with epicondylectomy. ^[93]

A more recent study of 480 patients reported in 2014 showed that both approaches effectively improved clinical outcomes for ulnar nerve compression at the cubital tunnel. ^[171] However, the decompression (neurolysis) alone showed greater effectiveness in relieving pain at the elbow.

Decompression in situ is essentially a localized decompression of the nerve. It is accomplished by incising the Osborne ligament and opening the tunnel beneath the two heads of the flexor carpi ulnaris by incising the fascia holding them together. It is easy to perform, and the complication rate is low. In contrast to other methods, ulnar nerve decompression in situ avoids damage to the vascular supply of the nerve. It is less traumatic to the patient than other decompression procedures, and it is equally successful. ^{[172, 146, 173]}

The main advantage of decompression in situ is the ability to release the ulnar nerve in compression areas with minimal blood supply disturbance. In addition, this procedure avoids subluxation of the ulnar nerve, which may lead to a recurrence of symptoms secondary to repeated contusion of the nerve as it snaps over the medial epicondyle.

The disadvantages of simple decompression would be the potentially higher recurrence rate and the risk of continued subluxation of the ulnar nerve over the medial epicondyle if that were present preoperatively.

An incision about 6-10 cm in length is made along the course of the ulnar nerve, midway between the medial epicondyle and the tip of the olecranon. This posterior incision is recommended to avoid damage to the medial brachial and medial antebrachial cutaneous nerves,171, which must be identified and protected if encountered.

Tourniquet control is employed to facilitate visualization of the nerve. The ulnar nerve is identified proximally. The medial intermuscular septum is released; in some cases, it may be advisable to excise part of the thickened distal medial intermuscular septum to prevent kinking.

The cubital tunnel retinaculum is sharply divided in a proximal-to-distal direction. The ulnar nerve is exposed as it passes between the two heads of the flexor carpi ulnaris. The fascia over the flexor carpi ulnaris is incised, and the nerve is exposed as it passes through the muscle. The deep flexor-pronator aponeurosis is released. Neurolysis is not necessary.

The elbow is taken through its range of motion (ROM), and the ulnar nerve is examined for subluxation; if subluxation is noted, medial epicondylectomy or decompression with anterior transposition should be considered. The tourniquet is dropped, and hemostasis is obtained. Subcutaneous and skin layers are closed. A simple soft compressive dressing is applied. Postoperatively, no or only minimal immobilization is needed, and early active extremity use is encouraged.

Out of concern over possible resultant subluxation and new compression, some believe that the nerve should not be decompressed proximally. ^[174] The risk of these adverse outcomes can be significantly reduced by limiting the decompression distal to a line drawn from the medial epicondyle to the tip of the olecranon. Proximal decompression is recommended when compression is secondary to a hypertrophied medial head of the triceps or a snapping of the medial head of the triceps with elbow flexion.

Decompression with anterior transposition is usually the operation of choice for ulnar nerve compression at the elbow. Its main advantage is that it moves the ulnar nerve from an unsuitable bed to one that is less scarred. The nerve is lengthened a few centimeters with transposition, decreasing the tension placed on the nerve with elbow flexion. ^[38]

The primary disadvantage of an anterior transposition is that it is more technically demanding than a simple ulnar nerve decompression. In addition, the risk of complications is increased when the nerve is moved from its natural bed, and there is a potential for the devascularization of the ulnar nerve. 

There are three types of anterior transposition, as follows:

• Subcutaneous

• Intramuscular

• Submuscular

Each type has its advocates, and specific indications, advantages, and disadvantages differ from one type to the next.

Subcutaneous transposition

Subcutaneous transposition is the most commonly used method of transposition. It may be the procedure of choice in athletes who throw and do not have muscular atrophy. However, these athletes may lose forearm strength from a submuscular transposition, and a simple decompression may not relieve symptoms adequately.

The main advantage of a subcutaneous transposition is that it is easy to perform. Therefore, it is a suitable procedure when subluxation and nerve traction contribute to the patient’s symptoms. ^[175] The primary disadvantage is that the nerve may be hypersensitive after surgery because of its new superficial location. In addition, the potential exists for disruption of the ulnar nerve blood supply with the transposition.

A longitudinal incision approximately 15 cm in length is made throughout the ulnar nerve. Once the nerve is visualized from about 8 cm proximal to the medial epicondyle to 6 cm distal to the epicondyle, the distal portion of the medial intermuscular septum, the fibroaponeurotic roof of the epicondylar, groove, the Osborne ligament, and the flexor carpi ulnaris fascia are incised, freeing the nerve. About 3-4 cm of the medial intermuscular septum proximal to the medial epicondyle is excised to prevent postoperative kinking of the nerve.

Distally, the additional common aponeurosis between the flexor digitorum superficialis to the ring finger and the humeral head of the flexor carpi ulnaris is sought and, if present, excised to prevent kinking. Motor branches to the flexor carpi ulnaris and flexor digitorum profundus are identified, protected, and preserved. The first motor branch to the flexor carpi ulnaris from the ulnar nerve proper is dissected out if necessary to prevent kinking.

The nerve is transposed into the subcutaneous plane. A search is made for any remaining sites of constriction or tethering. Several modifications are used to maintain the ulnar nerve in the transposed position. One is to hold the nerve to the muscle fascia with a few sutures through the epineurium. However, the more popular approach is to use some form of a sling. ^{[176, 177]}

A commonly used technique involves the creation of a fasciodermal sling. First, a 1- to 1.5-cm square flap of antebrachial fascia based on the apex of the medial epicondyle is raised and reflected medially. Next, the nerve is transposed anterior to this flap, and the apex is sutured to the dermal tissue approximately 1 cm anterior to the medial epicondyle.

Another technique is to use a subcutaneous-to-fascial sling. About 2 cm of the subcutaneous fascia of the anterior skin flap is sutured to the flexor-pronator fascia, just anterior to the epicondyle, to keep the nerve in the transposed position.

A third technique is creating a fascial sling using the medial intermuscular septum. The intermuscular septum is divided 3-4 cm proximal to its insertion on the medial epicondyle, with the distal attachment kept intact. The nerve is transposed. The septum is then used as either a myofascial or a fasciodermal sling to prevent posterior subluxation of the nerve. Care must be taken to avoid kinking of the nerve at the sling. Finally, a simple soft compressive dressing is applied, and early active ROM is instituted.

Postoperatively, the elbow must be immobilized at 45° of flexion for two weeks. Then, active mobilization with muscle stretching and strengthening is carried out for 2-3 months.

Intramuscular transposition

Intramuscular transposition is the least popular decompression method. It yields the lowest rate of excellent results and is associated with the most recurrences with severe ulnar nerve compression.

The main advantage of an intramuscular transposition is that it buries the nerve deeply while providing a tunnel through which the nerve can pass. It also allows the nerve to be surrounded by vascularized muscle tissue. The primary disadvantage is that it is a complicated procedure involving substantial soft-tissue dissection. In addition, the risk of perineural scarring increases, and the procedure may expose the nerve to repeated muscular contractions.

A longitudinal incision 15-20 cm in length is made throughout the ulnar nerve, and the nerve is decompressed similarly for subcutaneous transposition. The proximal border of the pronator teres and the medial intermuscular septum is excised from the mid humerus to the elbow. The nerve is then temporarily transposed, and the position of the nerve on the flexor-pronator mass is noted.

The ulnar nerve is replaced in the epicondylar groove, and a 5 mm deep trough is made in line with the nerve in its transposed position on the flexor-pronator mass. The fibrous septum separating the flexor-pronator muscles is excised to provide a soft vascularized muscle bed. The nerve is transposed. The flexor-pronator fascia is closed over the nerve, the forearm fully pronated, and the elbow flexed 90°. Finally, a simple soft compressive dressing is applied.

Postoperative management involves three weeks of immobilization at 90° of elbow flexion with the forearm in full pronation. This is followed by gradual active ROM exercises, stretching, and muscle strengthening.

Submuscular transposition

A submuscular transposition offers the best results, with the fewest recurrences with severe ulnar nerve compression. ^[178] It is the best salvage procedure when previous surgery has failed because it places the nerve in an unscarred bed. It also works well for very thin patients, in whom a subcutaneous transposition may result in an area of hypersensitivity over the transposed nerve. Finally, many consider an anterior submuscular transposition the procedure of choice for symptomatic athletes who throw.

The disadvantage of a submuscular transposition is that it is a technically demanding procedure. In addition, because of the extensive dissection involved, the postoperative recovery is more complex, and there is a 5-10% risk of elbow flexion contracture. Patients may also develop extensive scar formation from the procedure, and revision is complex if the patient has a recurrence.

In a submuscular transposition, the origin of the flexor-pronator muscle group must be released. This can be accomplished in several ways, and the most crucial part of any of these releases is to reattach the muscle origin securely. Once the nerve has been transposed to its new bed deep to the flexor-pronator muscle group and on the brachialis, the flexor carpi ulnaris fascia is closed, as is the roof of the epicondylar groove.

A longitudinal incision 15-20 cm in length is made throughout the ulnar nerve, and the nerve is decompressed similarly for subcutaneous transposition. The anterior skin flap is raised until the bicipital aponeurosis is visualized. The overlying fascia is incised, with care taken to identify and protect the median nerve. Because of the extensive venous system in this area, meticulous hemostasis is important. ^[179]

With the nerves protected, the margins of the flexor-pronator mass are delineated. A plane is developed with blunt dissection between the flexor-pronator mass, the flexor digitorum superficialis, and the ulnar collateral ligament. A hemostat is passed in this plane, with care taken to protect the nerves. The flexor-pronator mass is incised in a Z-cut fashion 1-2 cm distal to the medial epicondyle and then reflected distally. The ulnar collateral ligament must be protected.

The tourniquet is then released, and hemostasis is obtained. The ulnar nerve is transposed adjacent and parallel to the median nerve. The lengthened flexor-pronator mass is reattached with nonabsorbable sutures with the elbow flexed and the arm pronated.

Postoperatively, the elbow is immobilized in a post-mold or cast at 45° of flexion, with slight pronation and the wrist in a neutral position, for 3-4 weeks. Then, active ROM exercises, stretching, and strengthening are carried out for 3-4 months.

Surgical outcomes

In a retrospective study by Charles et al., 49 patients who underwent ulnar nerve transposition were followed to assess clinical sensory and motor recovery in cubital tunnel syndrome and to determine whether such factors influence recovery as preoperative McGowan stage, age, and symptom duration. ^[145] Submuscular transposition was used in 25 patients, and subcutaneous transposition was applied in 24 patients.

Noticeable improvement was reported in 20 of the 25 patients in the submuscular group and 17 of the 24 patients in the subcutaneous group. ^[145] Both groups showed significant improvement in sensory and motor function, with 17 patients in each group recovering sensory function and 19 in each group recovering motor function. Patients with symptoms lasting longer than six months had a poor prognosis, regardless of the surgical technique used.

Jaddue et al. compared operative technique (incision length and operating time), postoperative care (postoperative pain and complications), and outcome between subcutaneous and submuscular surgical procedures for anterior transposition of the ulnar nerve after decompression in moderate cubital tunnel syndrome. ^[180] Subcutaneous transposition was associated with a shorter incision, reduced operating time, less postoperative pain, fewer postoperative complications, and better outcomes.

Medial epicondylectomy is another technique for releasing pressure on the ulnar nerve at the elbow. Removal of the epicondyle removes a compressive area. The excision of the proper amount of bone is critical to the procedure's success. If too much bone is excised, damage to the medial collateral ligament of the elbow with valgus instability may occur; if too little is removed, the procedure fails because the compressive area remains. 

The main advantage of medial epicondylectomy is that it provides a more thorough decompression of the ulnar nerve than a simple release. This results in a mini transposition of the ulnar nerve. Compared with decompression plus anterior transposition, medial epicondylectomy better preserves the blood supply to the nerve causes minor injury to the nerve and preserves the small proximal nerve branches that might be sacrificed with an anterior transposition. ^[181]

The primary disadvantage is that it allows more significant migration of the ulnar nerve with elbow flexion. As a result, there is a potential for elbow instability if the collateral ligaments are damaged. In addition, bone pain and nerve vulnerability at the epicondylectomy site may occur. As a result, medial epicondylectomy is more likely to result in elbow stiffness or an elbow flexion contracture than simple decompression. In addition, it is often a poor choice for athletes who throw because of the significant stresses placed on the medial aspect of the elbow joint.

A longitudinal incision 10-15 cm in length is made throughout the ulnar nerve, centered 1 cm anterior to the tip of the medial epicondyle. ^[182] The posterior branches of the medial brachial and antebrachial cutaneous nerves are identified and protected, and the nerve is decompressed as previously described.

A longitudinal incision is made over the medial epicondyle, which is then exposed through subperiosteal dissection. The flexor-pronator origin is detached from the epicondyle and reflected distally. With care taken to protect the nerve, the medial epicondyle, or a portion of it, is removed with an osteotome. Avoiding entering the elbow joint or cutting the ulnar collateral ligament is essential. Sharp edges of bone are smoothed with a rongeur or rasp.

The periosteum is then closed to prevent the tethering of the nerve to the raw bone surface. Next, the flexor-pronator origin is reattached with the elbow in extension to help prevent the development of a flexion contracture. Next, the ulnar nerve is allowed to slide anteriorly. ^[183] Finally, a simple soft compressive dressing is applied.

No postoperative immobilization is necessary, and active ROM exercises are started as soon as the patient can tolerate them. Within 1-2 months, regular activities should be resumed.

Surgical outcomes

Seradge found flexion contractures after medial epicondylectomy in 5% of patients who started rehabilitation at an average of postoperative day 3 and in 52% of patients who started rehabilitation at an average of postoperative day 14. ^{[90, 91]} Patients in the early mobilization group returned to work twice as early as those in the late mobilization group. In addition, they experienced no adverse effects on their grip strength or other hand functions.

Weirich studied 36 patients who underwent subcutaneous transposition and found no differences in pain relief, weakness, patient satisfaction, grip strength, lateral pinch, or two-point discrimination between patients who were started on immediate active ROM exercises and those who began rehabilitation with an average of 14 days after postoperatively. ^[184] Patients in the immediate-mobilization group returned to work and performed activities of daily living earlier (median, one month) than those in the delayed-mobilization group (median, 2.75 months).

Endoscopy of nonjoint cavities is widely performed, and endoscopic carpal tunnel release is popular, though still debated, method of releasing the median nerve at the wrist. ^[39] With this experience in mind, some authors have attempted endoscopic cubital tunnel release. This technique allows local decompression while offering the ability to decompress the nerve at all potential compression sites. The possible advantages of this technique include limited invasiveness, reduced complication rates, and quicker rehabilitation. ^{[185, 186]}

Tsu-Min Tsai et al., after performing an endoscopic cubital tunnel release on 85 elbows in 76 patients and monitoring them for an average of 32 months, found that 42% had excellent results and 45% had good, 11% had fair results, and 2% had poor results. ^[187] These results are comparable to those achieved with the other decompressive techniques, for which the overall rate of good-to-excellent results is 85-90%. 

The most severe complications of surgical decompression of the ulnar nerve are the following: ^[188]

• Failure to decompress the nerve adequately, causing a new area of entrapment with the decompression

• Injury to the nerve during decompression or transposition

• Neuromata of the medial antebrachial cutaneous nerve

• Failure to recognize a double-crush syndrome

• Infection, failure to heal, thrombophlebitis, atelectasis, and failure of the operation due to an unknown cause 

Creating a new compressive site at the time of surgery can occur with any of the decompressive methods. ^{[189, 190]} Injury to the posterior branches of the medial antebrachial cutaneous nerves at dissection is common. This nerve laceration results in loss of sensibility in an area of skin posterior and distal to the incision. Some patients develop a resultant dysesthesia in the nerve distribution; others develop an amputation neuroma.

Recurrent ulnar nerve subluxation and elbow instability can result from damage to the elbow collateral ligaments. ^[191] A postoperative flexion contracture can occur, most commonly following a submuscular transposition; it is seen after 5-10% of submuscular transpositions. Medial epicondylitis can occur from the detachment of the flexor-pronator mass or as a result of a medial epicondylectomy. In addition, the symptoms may recur after an incomplete anterior transposition. Infection can occur with any surgical procedure.

After decompression with anterior transposition, complications can include recurrent ulnar nerve subluxation. Incomplete release of fascial slings may result in new areas of compression. In one series of subcutaneous transpositions, 90% of the failures were secondary to the insufficient release of the medial intermuscular septum. An ineffective sling may not maintain the position of the transposed nerve and prevent resubluxation.

In addition, scarring may occur in the new muscular channel for the nerve. Perineural fibrosis may result from an intraneural injury or a nerve transfer to a hypovascular bed. Damage to the flexor carpi ulnaris motor branches during nerve mobilization may result in weakness. Ligating the posterior ulnar recurrent artery during nerve mobilization may result in nerve devascularization. A postoperative elbow flexion contracture may occur.

After medial epicondylectomy, medial instability may occur. To prevent this complication, the flexor-pronator origin is carefully detached to preserve the fibers of the medial collateral ligament. According to O’Driscoll et al., excision of more than 20% (1-4 mm) of the width of the medial epicondyle in the coronal plane violates the important anterior band of the ligament. ^[13]

Removing the optimal amount of medial epicondyle without creating instability also improves results. For example, Heithoff and Millender found in their series that a complete osteotomy resulted in 81% good and excellent results. ^[88] A partial osteotomy yielded a 67% rate of good or excellent results, and a minimal osteotomy yielded a 50% rate of good or excellent results.

Tenderness at the operative site can occur after medial epicondylectomy, sometimes resulting in prolonged and persistent discomfort during bone healing. In addition, loss of the protection afforded by the medial epicondyle may render the ulnar nerve more susceptible to trauma. Therefore, to prevent the nerve from adhering to the osteotomy site postoperatively, it is important to preserve and close the periosteum at the end of the procedure.

Detachment of the flexor-pronator origin can result in weakness. Patients may develop an elbow flexion contracture often attributed to reattachment of the flexor-pronator muscle origin. In contrast, the elbow is flexed or to delayed or inadequate postoperative mobilization.

Finally, postoperative ulnar neuropathies frequently give rise to lawsuits. Although such neuropathies appear to be most common after cardiac procedures, a Mayo Clinic study cited a rate of 0.5% even after noncardiac procedures. ^[192] Often, the neuropathy does not appear immediately after the operation, suggesting that nerve trauma may occur in the postoperative period. Careful attention to protecting the ulnar nerve both during and after the procedure may reduce the injury rate and the number of ensuing legal claims.