➢ Most patients (>90%) will have continued or recurrent symptoms after primary cubital tunnel release. Those patients with severe preoperative findings are at a higher risk of failure.
➢ Failed primary surgery may be due to diagnostic, technical, or biologic factors.
➢ Revision surgical interventions can provide relief, but there is no consensus on what is the optimal technique.
➢ The options for revision surgery include simple neurolysis, neurolysis with subcutaneous transposition, and neurolysis with submuscular transposition. Autogenous (vein) and non-autogenous nerve wraps may be placed around the nerve to prevent cicatrix reformation.
Compression of the ulnar nerve as it courses from the arm past the elbow to the forearm can lead to symptoms such as pain, numbness, dysesthesia, and weakness in the ulnar nerve-innervated muscles1. This syndrome, termed cubital tunnel syndrome, is the second most common upper-extremity compressive neuropathy, following carpal tunnel syndrome2-4. Current surgical management of cubital tunnel syndrome, which focuses on relieving ulnar nerve compression, provides a satisfactory sensory and motor improvement for >90% of patients5-8. However, the patient who has had failed surgical treatment, defined as someone who experiences no improvement in symptoms or recurrent symptoms9, offers a difficult clinical challenge. Patients with severe disease have been shown to be at a higher risk of having poor results7,8. This article will focus on the etiology of recurrent cubital tunnel syndrome and the evaluation and management of patients with this diagnosis.
The reasons for failure of a primary cubital tunnel surgery can be categorized as diagnostic, biologic, or technical. If there is no relief of symptoms after surgery, the surgeon must consider that either the patient had the incorrect diagnosis or the patient had a concomitant diagnosis (diagnostic), an inadequate release (technical), or a dysfunctional nerve from preoperative compression (biologic). Alternatively, if the patient reports that the symptoms resolved for a period of time but then returned, cicatrix may be the cause (biologic). It is essential that the surgeon differentiate between a patient who never had improvement and a patient who had improvement and then developed recurrent symptoms.
It is critical that the surgeon establish the etiology of recurrent ulnar nerve compression following the failed initial surgery. Other sources of nerve compression should be evaluated, both proximally and distally. Therefore, clinicians should entertain other sites of compression including the carpal tunnel (e.g., carpal tunnel syndrome), Guyon canal, or cervical nerve roots (e.g., C8 radiculopathy). If the diagnosis was based on clinical findings alone with no confirmatory electrodiagnostic study, then the diagnosis of cubital tunnel syndrome may be incorrect. However, electrodiagnostic studies are not infallible. One study found that, even in patients with definite clinical symptoms of cubital tunnel syndrome, nerve studies only localized the abnormalities to the ulnar nerve in 86% of patients10.
The differential diagnosis also includes less common causes such as hypothenar hammer syndrome, a Pancoast tumor affecting the proximal brachial plexus fibers, and thoracic outlet syndrome. Other non-compressive nerve causes include Raynaud disease or phenomenon, flexor carpi ulnar tendinitis, medial epicondylitis, or brachial plexus neuritis (Parsonage-Turner syndrome). Another possibility is that the patient has a concomitant diagnosis so that treatment of cubital tunnel syndrome does not resolve all of the symptoms. If the second diagnosis is nerve-related, such as C8 radiculopathy, then the patient may have a double crush syndrome whereby proximal compression of a nerve renders the distal end more susceptible to compression.
Technical causes are related to incomplete decompression of the nerve, iatrogenic creation of a new site of compression, subluxation of the ulnar nerve from an in situ decompression, injury to the medial antebrachial cutaneous nerve, and direct ulnar nerve injury. During transposition, the creation of a new site of compression may occur. Multiple authors have reported that the unresected intermuscular septum was the site of compression found during revision cubital tunnel surgery11-14. These results have led to the teaching that the intermuscular septum should be resected during an anterior transposition. Another source of nerve compression with transposition is when the nerve does not have a straight path and there is kinking. This can occur when the nerve is transposed anterior to the medial epicondyle but then has to travel posteriorly into the flexor carpi ulnaris muscle heads.
Simple decompression consists of release of the roof (arcuate ligament of Osborne) of the cubital tunnel with or without the aponeurosis of the flexor carpi ulnar heads. The nerve is not transposed and is left in situ, but releasing the containing fascia may lead to ulnar nerve instability where the nerve subluxates anterior to the medial epicondyle with elbow flexion. This has been reported to occur in 2.4% to 17% of cases15-17. Antoniadis and Richter found in five of ten failures that ulnar nerve subluxation after decompression without transposition was a persistent source of nerve irritation18. Additionally, Vogel et al. found ulnar nerve instability in eight of eighteen patients14.
Fortunately, direct ulnar nerve injury is rare, but medial antebrachial cutaneous nerve injury was found by Mackinnon and Novak in seventy-three of 100 revision cubital tunnel releases19. However, some would argue that this is not a failure of cubital tunnel surgery but rather a complication. Some patients could interpret their symptoms from the medial antebrachial cutaneous nerve neuroma as similar to their preoperative ulnar nerve symptoms.
Biologic reasons such as perineural fibrosis have been shown to be a frequent finding in revision cases11-13,20-22. In the series by Gabel and Amadio, there was a mean of 2.2 levels of compression, which were all described as fibrosis12. Rogers et al. reviewed the cases of fourteen patients who had failed ulnar nerve release and found dense scarring of the nerve to the medial epicondylectomy site in seven patients, scarring in the cubital tunnel in the one patient who had in situ decompression, and, lastly, thick scarring within the flexor pronator mass in the one patient with an intramuscular transposition13.
Another biologic cause for failure of primary cubital tunnel surgery is severe preoperative ulnar nerve damage from long-standing compression. After undergoing surgery, the patient may experience little to no improvement in symptoms, which makes the surgery a failure from the patient’s standpoint. The peripheral nerve surgeon cannot ameliorate the preoperative status of the nerve, but he or she can diagnose the severe compression, can counsel the patient, and can manage expectations. This is where an objective study, such as the nerve conduction study and electromyography (EMG), is valuable to confirm severe compressive neuropathy. The patient can be advised that some symptom improvement will likely occur and can continue beyond two years after surgery; however, it is likely that some residual symptoms will remain23. The principal goal of surgery in chronic severe compression is to prevent worsening of motor dysfunction and sensory symptoms, with the secondary goal of symptom improvement. It is clear that patients with worse compressive neuropathy preoperatively fare worse than patients with milder compression. Dellon found that <50% of patients with long-standing symptoms and severe deficits experienced substantial sensory improvement7.
The patient who comes for an initial visit after failure of a primary cubital tunnel surgery deserves time to fully understand his or her symptoms and the history of his or her illness. The critical part of the history is understanding what symptoms the patient experienced before surgery and what he or she is experiencing now. Has there been no change in the symptoms, or was there an initial improvement followed by recurrence of the symptoms? If there was no change in the symptoms, the possibilities include an incorrect diagnosis, an incomplete release (technical factor), or permanent nerve damage due to severe compression (biologic cause). A period of improvement followed by recurrent or worsening symptoms would suggest that a complete decompression was performed initially, but cicatrix formation led to nerve compression (biologic cause).
The examination of the symptomatic patient who has had surgical treatment for cubital tunnel syndrome starts with the standard examination for ulnar nerve neuropathy at the elbow. This includes inspection (for clawing, intrinsic muscle atrophy, hypothenar muscle atrophy), motor function (finger abduction, finger crossing, Froment test), and sensory function (moving or static two-point discrimination, Semmes-Weinstein monofilament)24. Provocative maneuvers include the elbow flexion test (reproduction of numbness or tingling after ninety seconds of elbow flexion with the wrist extended and the forearm supinated) and the Tinel test25,26. If the patient reports that the Tinel test at the ulnar nerve is less intense or is located more distally than it was preoperatively, it may suggest recovery is in progress. Additionally, a peri-incisional Tinel test may indicate a medial antebrachial cutaneous neuroma. The ulnar nerve should be evaluated for subluxation, especially if the first surgery was an in situ decompression. When evaluating the patient who has had ulnar nerve release, the length of the scar should be noted. If the incision is small and a transposition was performed, is it possible that all five potential sites of compression were not released? Lastly, tenderness of the scar may indicate scar sensitivity.
Other abnormalities must be ruled out. A positive Tinel test at the supraclavicular and infraclavicular levels may indicate a brachial plexus problem. A positive Tinel test along the median nerve may indicate carpal tunnel syndrome. Other provocative maneuvers for carpal tunnel syndrome (Phalen test, reverse Phalen test, Durkan test27,28) can be checked. A Tinel test at the Guyon canal can indicate compression at this site, although it is much less common than at the elbow. Intact sensation of the dorsal ulnar hand (via the dorsal ulnar cutaneous branch) may help to distinguish compression at the Guyon canal rather than at the elbow. Tenderness at the medial epicondyle may indicate medial epicondylitis and tenderness along the flexor carpi ulnaris may indicate flexor carpi ulnaris tendinitis, rather than cubital tunnel syndrome29. Cervical nerve root impingement can be tested by a Spurling maneuver or l’Hermitte sign. Thoracic outlet compression must be checked with the Adson, Wright, and Roos tests30.
Repeating the nerve conduction study or EMG testing may be helpful to compare with preoperative values, although the results will only be helpful if they show improvement or worsening. Unchanged electrodiagnostic studies add less value because, even with successful surgery with symptom improvement, the studies often show no improvement. Thus, a completely released ulnar nerve cannot be distinguished from an incompletely released nerve because both may have an unchanged nerve conduction study or EMG. If the nerve conduction study or EMG shows improvement, the surgeon has support to continue to monitor the patient, with the caveat that an incompletely released nerve may show improvement on a nerve study. If the nerve conduction study or EMG shows worsening, then reexploration is indicated, especially when perineural fibrosis or an ulnar nerve injury is suspected. If cervical root compression or Guyon canal compression is suspected, magnetic resonance imaging (MRI) of those sites may be ordered.
Observation and Conservative Treatment
One of the most difficult decisions to make is when to advise the patient that he or she needs a revision cubital tunnel surgery. If the initial surgery was done by the treating physician and the treating physician is certain that a complete release was performed, observation for three to six months is reasonable, especially if the preoperative nerve study showed severe compression (biologic cause). If the patient reports no change in symptoms but a new nerve study shows improvement, then there is support to monitor the patient with the understanding that an incomplete release could theoretically yield an improved nerve conduction study or EMG. If the initial surgery was not performed by the treating physician, then a complete release may not be ensured, which may impel the surgeon to recommend surgery, especially if the patient experienced no change in symptoms (incomplete release as the technical cause). Often, physicians wait unnecessarily with the hope that the condition improves; it is important to have legitimate reasons for observation.
Conservative management with night splinting and nerve-gliding exercises should not further exacerbate any problems; however, to our knowledge, no studies have evaluated the rate of success of conservative treatment following failed surgical intervention. After undergoing surgical treatment, conservative therapy will most likely not have a long-lasting benefit. However, these treatments can be employed during observation.
Similar to the situation for primary cubital tunnel surgery, the options for revision cubital tunnel surgery are varied with no definitively proven superior technique. Many authors have chosen submuscular transposition as their treatment of choice when managing patients for whom cubital tunnel surgery failed12-14,20,31. The other options for revision cubital tunnel syndrome include simple neurolysis22, subcutaneous transposition12,21, and intramuscular transposition32,33.
As reviewed earlier, perineural fibrosis is a common finding during revision surgery11-13,20-22. An unresected intermuscular septum, which is an easily correctable technical error, may also be a cause of failure11-13,20-22. The senior author (P.T.) believes that the important aspect of revision cubital tunnel surgery has less to do with where the nerve is placed and more to do with how to prevent cicatrix. The nerve could be placed in any location, but if the patient’s body is programmed to form the same perineural cicatrix that led to the recurrent symptoms, the revision procedure is doomed to failure. For primary cubital tunnel surgery, to minimize soft-tissue trauma, scarring, and treatment failure, the senior author favors an in situ release of the fascia 1 cm proximal to the medial epicondyle, posterior to the medial epicondyle, the roof of cubital tunnel, and the flexor carpi ulnaris aponeurosis, through a 4.5-cm skin incision. The senior author believes that the medial epicondyle and the cubital tunnel are the most common sites of compression in cubital tunnel syndrome and that the ulnar nerve is not concurrently compressed at five sites. In the original article describing the five sites of compression, Amadio found that the cubital tunnel was the most common site of compression followed by the region of the medial epicondyle34. If there is subluxation of the nerve, the senior author will either perform a subcutaneous transposition or create a blocking flap. The subcutaneous transposition is performed as described by Eaton et al. with a fascial sling from the flexor or pronator fascia through a 14-cm incision (8 cm proximal to the medial epicondyle, where the arcade of Struthers is approximately located, and 6 cm distal to the medial epicondyle, where the two heads of the flexor carpi ulnaris are approximately located)35. For the second option, to forgo a transposition but prevent subluxation, the fascia posterior to the medial epicondyle and the arcuate ligament of Osborne is incised posteriorly when exposing the ulnar nerve so that the fascia remains attached to the medial epicondyle. The fascia is then sutured. The ligament is then sutured to the subcutaneous adipose tissue of the posterior skin flap to create a blocking flap to prevent anterior subluxation.
To provide a cicatrix barrier and to allow nerve gliding, there have been various proposals to wrap the nerve. Campbell et al. described a technique using silicone elastomer bands36, and Puckett et al. recommended using an artificial acellular human skin-derived tissue matrix37. A more accepted technique developed by Sotereanos and colleagues involves wrapping the ulnar nerve with autogenous saphenous vein38-42. These clinical studies have support from animal experiment results43,44. Non-autogenous wraps made from collagen, polyglycolic acid, caprolactone, or porcine extracellular matrix may become more popular because of ease of use and lack of donor-site morbidity. Clinical studies focusing specifically on compressive neuropathies using non-autogenous wrap are scarce37,45,46. Some animal studies may support their use. One study found that transected and immediately repaired rat sciatic nerves had a similar degree of extraneural scar reduction when wrapped in autogenous vein or collagen conduit when compared with those that had no wrapping44. However, Kokkalis et al. found smooth gliding in intact, uninjured rabbit sciatic nerves wrapped with a porcine extracellular matrix, but the results of subjective evaluation, histologic comparison, and EMG testing were no different from those of unwrapped nerves47. Recently, Papatheodorou et al. reported the use of porcine extracellular nerve wrap in recurrent cubital tunnel syndrome in twelve patients and found significant improvements in pain, satisfaction, and grip and pinch strength (p < 0.001)46. The mean static two-point discrimination improved from 10.4 to 7.6 mm46. The authors also performed a minimal medial epicondylectomy when not previously performed46.
For a summary of outcomes from previous studies evaluating revision cubital tunnel surgery, see Table I12-14,21,22,40,46,48,49. Overall, the literature is limited in quantity and quality of studies. From one perspective, this can be viewed positively, because it may indicate that primary cubital tunnel release yields excellent outcomes in the majority of cases. Large studies that randomize surgical techniques in managing failed cubital tunnel release are best evaluated with a multi-institutional approach. Recommendations for any one particular technique are limited secondary to low-quality or insufficient evidence (Table II)50.
It is important to note that, to our knowledge, there have been no studies on intramuscular transposition for revision cubital tunnel surgery.
If the cause of failure is inadequate release, revision surgery should focus on releasing this site of compression. Often, it is not so simple and the failure of the primary surgery is due to scar formation. There is no clearly superior method to manage this problem, but we advocate an approach with straightforward goals: remove any offending sites of external compression on the nerve, place the nerve in a stable position, and consider a barrier to protect the nerve from cicatrix. The senior author does not necessarily think that submuscular transposition is the answer because it is exceedingly traumatic, which may lead to recurrent scarring. He also does not agree with placing the ulnar nerve in (intramuscular) or under (submuscular) a contractile structure, that is, the flexor-pronator mass, in the primary or revision setting.
Surgeons undertaking revision cubital tunnel surgery should be familiar with the five potential sites of compression encountered in primary surgery: the arcade of Struthers, the medial intermuscular septum, the medial epicondyle, the cubital tunnel with the arcuate ligament of Osborne as its roof, and the aponeurosis of the flexor carpi ulnaris34. Also, Siemionow et al. identified the presence of fascial bands with varying length overlying the ulnar nerve that may need to be addressed during surgery51. At a minimum, the nerve needs to be explored proximal and distal to the previous surgical sites. This will allow the nerve to be found in pristine tissue planes and then to be followed and neurolysed into the fibrotic area. It is important to review the previous operative procedure to know what was done, what structures were disturbed, and where the nerve was placed. It is also critical to understand that what is expected during revision surgery may be different from what is found, despite appropriate review of the operative report, because other surgeons may differ in their surgical technique and/or how they describe or dictate the report. The bottom line is not to assume anything. The senior author has two preferred techniques for failed cubital tunnel release due to cicatrix. The first is a subcutaneous transposition, with the reasoning that this is the least traumatic transposition. The second is a modification of the technique by Danoff et al.52 where the anterior subcutaneous adipose tissue is divided into superficial and deep layers and the nerve is placed between these two layers and closed like a book with bioabsorbable suture. A wrap may also be placed around the nerve with both options. There is animal support that vascularized adipose tissue may improve nerve regeneration53.
Revision Cubital Tunnel Release Complications
Revision nerve surgery can be a high-risk procedure. The greatest concern is that the surgical site has such dense scar that the nerve cannot be dissected free. The worst complication is that the ulnar nerve is injured during this dissection. If the scar cannot be dissected from the nerve, one option is to leave a cuff of tissue around the nerve and continue the neurolysis. Another complication is injury to the medial antebrachial cutaneous nerve. The subcutaneous layer can also be scarred, which makes cutaneous nerve identification challenging. In general, most try to avoid injury to the medial antebrachial cutaneous nerve, but, compared with an ulnar nerve injury, it is a less morbid complication.
Cubital tunnel syndrome can be treated by any of the four popular techniques: in situ decompression, endoscopic decompression, decompression with medial epicondylectomy, and decompression with anterior transposition (subcutaneous, intramuscular, or submuscular). All four have been shown to have relatively equivalent outcomes, and approximately 90% or more of patients can expect success. For those with failure, the surgeon must determine the cause. Those with inadequate release, ulnar nerve or medial antebrachial cutaneous nerve injury, or perineural fibrosis should be offered revision surgery. Most of the studies involve neurolysis with submuscular transposition, but based on the poor level of evidence, only a weak recommendation can be made for it. In terms of wrapping the nerve, autogenous vein wrap has been most studied, but again, based on the poor level of evidence, a weak recommendation can be made for its use. Further research comparing outcomes for revision surgery can lend insight into which technique may provide better outcomes in the future so that stronger evidence-based recommendations can be made.
Source of Funding: There was no external source of funding.
Investigation performed at the Division of Hand, Upper Extremity, and Microvascular Surgery, Department of Orthopaedic Surgery, Allegheny General Hospital, Allegheny Health Network, Pittsburgh, Pennsylvania
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
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