CORR Insights®: What Factors Are Associated With Revision Cubital Tunnel Release Within 3 Years?

Where Are We Now?

Surgical release of cubital tunnel syndrome can be one of the most rewarding procedures, with many grateful patients reporting rapid improvement in sleep patterns and diurnal discomfort. For patients with severe symptoms, this relief may proceed to a more gradual improvement in sensory or motor dysfunction, which, depending on the degree of severity, may occur over weeks, months, or even years [1, 10]. Unfortunately, a subset of patients are not satisfied and consider the intervention to be a failure. Identifying patients who are more likely to experience this result in order to suggest that they avoid surgery altogether or at least modify the surgical approach would be useful.

Yet even if these patients could be identified, we simply do not know which treatment modifications will improve their outcomes. The pathophysiology behind entrapment neuropathy involves disruption of myelin sheath integrity, interference with axoplasmic transport, and some element of nerve tissue ischemia. Episodic ulnar nerve dysfunction is related to dynamic stress, either because of traction-related ischemia or elbow flexion–induced narrowing of the cubital tunnel. With repetitive ischemic episodes, reperfusion injury induces nerve tissue edema, further increasing vulnerability to nerve compression [3, 4, 8, 12]. Left unchecked, this process progresses to axonal loss, denervation atrophy, and interstitial nerve fibrosis manifesting as muscle weakness, abnormal hand posturing, loss of pinch and dexterity, and profound sensory loss. These later changes may not be reversible, leading to incomplete functional recovery. However, contrary to widely held belief, many patients in this category do achieve substantial improvement, albeit sometimes after a prolonged convalescence [1, 10].

If surgery is pursued, all agree that nerve decompression is essential. However, which anatomic structures must be released and whether the nerve ought to be repositioned remain sources of ongoing debate. Advocates of transposition cite the benefits of tension relief and relocation into a healthy tissue bed [6]. The relative efficacy of subcutaneous, intramuscular, and submuscular techniques is controversial, with submuscular potentially offering more “protection,” but also a greater potential for perineural scarring [11]—a concern potentially borne out by the findings reported by Schloemann et al. [9] in this issue of Clinical Orthopaedics and Related Research®. In situ release is simpler and quicker, preserving the natural blood supply to the nerve [5], and with endoscopic-assisted techniques or with firm retraction, an extensive release can be performed through a small incision. Iatrogenic medial antebrachial cutaneous nerve injury is less likely with a small incision, but the potential for postoperative hematoma formation increases (because of unrecognized bleeding) [2].

As many as 13% of patients consider their surgery to be a “failure” [11], but it depends on how failure is defined. Subsequent efforts to address complications or alleviate ongoing symptoms should focus on the etiology. Immediate worsening of ulnar nerve function suggests iatrogenic ulnar nerve injury or impingement, while focal incisional pain accompanying medial elbow or forearm paresthesias would indicate medial antebrachial cutaneous nerve laceration. For patients reporting temporary relief but recurrence of symptoms, incomplete release, perineural cicatrix formation, or iatrogenic nerve kinking should be considered. New or persistent nerve instability can cause painful neuritis as well. Prolonged, severe entrapment-induced neuropathy may not resolve despite a technically successful surgery, though unrelieved symptoms may also be caused by a missed alternative diagnosis, inadequate decompression, or iatrogenic impingement (from inadvertent kinking of a newly transposed nerve).

Clearly, not all patients should be treated with revision surgery. Medial antebrachial cutaneous injuries may respond to medical management, and if symptoms persist despite a technically well-done ulnar nerve decompression (for example, severe cubital tunnel syndrome–induced nerve damage), redoing the release is unlikely to yield much benefit. Some iatrogenic ulnar nerve injuries will improve with time, and symptoms related to cervical radiculopathy, thoracic outlet syndrome, myofascial pain syndrome, or ulnar tunnel syndrome will not improve with revision cubital tunnel release. In general, revision procedures are less predictable than the index procedure.

As highlighted in this month’s CORR®, Schloemann et al. [9] found that factors affecting the likelihood of undergoing revision cubital tunnel surgery seem to extend beyond the success or failure of the index procedure and must also reflect the patient’s eagerness for further treatment, the surgeon’s perception that something may have gone wrong with the index procedure, or the surgeon’s reluctance to perform additional procedures. For example, patients with workers compensation (secondary gain) and patients who underwent submuscular transposition (a more complex and therefore riskier procedure) were more likely to receive revision surgery, while patients with comorbidities (higher potential for medical complications) were less likely to [9].

Where Do We Need To Go?

Obviously, for a revision surgery to occur, there must be a willing surgeon, patient, and payer. This, however, does not necessarily mean that the revision surgery is a good idea or medically necessary—the determinants of both require identifying the cause of surgical failure, the intraoperative findings, and the result of the secondary effort, which are all essential questions to improve future treatment algorithms. Most correctable etiologies for patients with persistent symptoms after cubital tunnel release are related to technical issues (such as iatrogenic impingement or kinking, or incomplete release), nerve hypermobility, or excessive postoperative scarring. How do we identify which patients are at risk for these complications, which procedures are more prone to these complications, and what practical steps can be taken to limit their frequency?

How Do We Get There?

Looking at every possible treatment scenario with “well done randomized studies” is not practical. Randomly assigning surgical approaches to all patients with cubital tunnel syndrome does not account for differences in patient and disease characteristics, individual patient goals and risk-benefit tolerances, and differences in surgeon skill and experience. An in situ decompression, predictable in most patients, may not result in symptomatic relief when a hypermobile ulnar nerve is not further addressed. A well-done subcutaneous nerve transposition through a broad exposure will have a different prognosis than a poorly performed transposition through a “too-small” incision. A patient prone to excessive scarring may fail an otherwise reliable submuscular transposition.

Identifying risk factors in advance of surgery and studying “fluid decision-making” in the operating room are difficult. Data mining from existing databases is unlikely to identify definitive solutions to these complex questions, even if this approach does add limited insight and direct future study. This does not mean databases should be dismissed, however; instead, one should be prospectively developed and focused on the critical issues related to this procedure. This will not be easy, but the feasibility has been demonstrated by industry-sponsored efforts. One multicenter registry has enrolled 1630 nerve repairs [7]. To be successful, data acquisition must be regimented, meaningful, and efficient, and must involve many centers and surgeons to capture enough patients and the full spectrum of pathologies and treatment variables. These large rolling databases will require a coordinated effort, resources, and time, but may ultimately be the only way to compel meaningful progress.