Musculotendinous variations around the medial epicondyle can contribute to subluxation of the ulnar nerve at the elbow. This article reviews the presenting symptoms, operative findings, and results of surgery for subluxation of the ulnar nerve at the elbow. A retrospective evaluation was performed of 200 elbows managed operatively for medial elbow pathology over a 17-year period between 1990 and 2007. The patient charts were reviewed for chief complaint, radiographic studies, operative reports, and postoperative examination data. Seventeen patients (18 elbows) were treated for a subluxating ulnar nerve. Three patients were women and 14 were men, with a mean age of 27.6 years. Medial elbow pain was the chief complaint in all 17 patients. Seventeen elbows also demonstrated paresthesias in an ulnar nerve distribution. All patients were treated with anterior transposition of the ulnar nerve, and 11 patients (61%) were found to have a muscular anomaly.
At a mean follow-up of 17 months, the mean visual analog scale for pain improved from 6.0 to 2.0. There was no functional impairment reported for any patient at final follow-up. Of the 200 elbows surgically treated for medial elbow pathology, 17 patients (8.5%) demonstrated a subluxating ulnar nerve. These patients tend to be young and present with a primary complaint of medial elbow pain. In addition, a subluxating ulnar nerve is often associated with muscular anomalies, which must be addressed concurrently.
A traumatic symptomatic ulnar nerve subluxation remains a poorly understood clinical entity. While reports have documented certain aspects of disease presentation and treatment,1-4 as well as a variety of anatomic factors associated with subluxation of the ulnar nerve,5-9 no reports document the clinical presentation, anatomic features, and results of management of this condition. This article retrospectively reviews the experience at a large upper extremity referral center and reports the clinical features, intraoperative findings, management, and outcomes for subluxating ulnar nerve syndrome.
Materials and Methods
Following approval from our Institutional Review Board, we performed a retrospective chart review of 200 elbows surgically treated for ulnar nerve pathology over a 17-year period between 1990 and 2007. Patients were identified by searching the perioperative database for current procedural terminology codes related to nerve dysfunction of the medial elbow such as ulnar nerve exploration, decompression, subcutaneous transposition, and neuroplasty. Inclusion criteria were documented preoperative medial elbow pain, an operative diagnosis or finding of subluxating ulnar nerve, and complete follow-up data. Subluxation of the ulnar nerve was defined as movement of the ulnar nerve out of the postcondylar groove onto or across the tip of the medial humeral condyle when the elbow is flexed, returning to its normal location when the elbow is extended.3 Patients younger than 18 years, patients with other coexisting pathology, and patients having previous surgery on their ulnar nerve were included. Asymptomatic patients and those with open traumatic injuries were excluded. Data were collected from the medical records including age, sex, race, causal factors, affected side, radiographs, and clinical examination findings.
Seventeen patients (18 elbows) treated by 4 surgeons (M.J.R., R.D.G., D.S.R.) met the inclusion criteria (Table 1). Mean patient age was 27.6 years (range, 12-55 years). Three patients were women and 14 patients were men. Eleven of the affected elbows were on the right and 7 were on the left. Four patients (24%) were of Asian ethnicity. Ten of 17 (59%) patients were involved in weight lifting as a primary sport. The 3 women were all college-level athletes, 2 of whom were rowers. The mean time of preoperative symptoms was 12.2 months (range, 2-36 months). The dominant arm was affected in 5 patients (29%).
Complete clinical examination of the affected elbow was performed, including evaluation for medial epicondylitis, ulnar nerve compression at the elbow, and medial collateral ligament pathology. All elbows were palpated to detect the presence of a subluxating ulnar nerve. Nerve conduction studies were reviewed in all patients to assess for compression of the ulnar nerve. Radiographs were performed on 15 elbows. If the clinical examination was inconclusive, magnetic resonance imaging (MRI) was performed to assess for other etiologies.
All patients with a history of symptoms consistent with ulnar neuropathy were treated initially with a trial of nighttime extension splints and recommendations to avoid direct pressure to the medial elbow. All patients suspected of having medial epicondylitis were treated with activity modification and a rehabilitation program including stretching and gradual strengthening. Other modalities were included according to the surgeons preferences. Only patients who failed conservative therapy were considered for surgical intervention. Statistical analysis of pain scores was performed with the paired Student t test. There was no external source of funding for this study.
The procedure was performed in the supine position under tourniquet control. In each patient, the ulnar nerve was exposed at the elbow via a standard longitudinal posteromedial incision. Intraoperative examination with the elbow was performed in full flexion and extension to assess for the presence of a subluxating ulnar nerve. The nerve was then decompressed over its length from the arcade of Struthers to the first motor branch to the flexor carpi ulnaris. Anatomic variations were noted. The ulnar nerve pierces the medial intermuscular septum approximately 8 cm above the medial epicondyle and lies posterior to this structure in the distal brachium. The thick fibrous band of the medial intermuscular septum was routinely excised from the medial epicondyle proximally to the level of the arcade of Struthers. The nerve was then transposed anteriorly in all patients, and it was confirmed that there was no compression of the nerve at the site of the excised septum. The nerve was placed deep to a fascial sling fashioned from a Z-type piece of the flexor-pronator fascia.10,11 The fascia was then sutured over the nerve without compression.
Postoperatively, patients were started immediately with active range of motion (ROM) as tolerated without restrictions to avoid scarring and stiffness. Subjective outcome assessment included the visual analog scale (VAS) for pain and any patient reports of ulnar nerve symptoms. Pain scale data were analyzed for statistical significance with a paired Student t test. Objective outcome assessment included measurements of elbow ROM and presence of a palpable subluxating ulnar nerve. Follow-up occurred at 2 weeks, 6 weeks, 3 months, 6 months, 1 year, and thereafter at the treating surgeons discretion.
Medial elbow pain was the major preoperative report in all patients. None of the patients had pain with stress testing of the flexor pronator origin. The ulnar nerve of 10 of 18 elbows (56%) could be felt to subluxate in clinic (all 18 were noted to subluxate intraoperatively) (Table 2). Seventeen of 18 elbows (94%) had symptoms of paresthesias in the ulnar nerve distribution. None of the patients had evidence of ulnar nerve injury on peripheral nerve conduction studies. Three of these patients had a Tinels sign over the ulnar nerve at the elbow (Table 2). All patients demonstrated tenderness to palpation over the medial elbow with elbow flexion.
For suspected medial collateral ligament pathology, the moving valgus stress test was performed. Unlike in medial collateral ligament pathology, the moving valgus stress test reproduced medial elbow pain only at maximum flexion when the nerve was observed to subluxate over the epicondyle. Two patients had a positive elbow flexion test with paresthesias into the ring and small finger when the elbow was held in full flexion and the wrist in extension. Eight (42%) of the affected elbows were associated with weakness (<3/5) of the intrinsics preoperatively based on manual muscle testing.
Radiographs were obtained for 15 elbows. Four (27%) elbows demonstrated abnormalities on radiographs, with mild degenerative changes in 2 patients and abnormal anatomic alignment in 2 (1 valgus, 1 varus). Seven static MRIs were performed, none of which identified a subluxated ulnar nerve. One dynamic MRI was performed, which identified a subluxated ulnar nerve (Figure 1).
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|Figure 1: Ulnar nerve in the anatomic position with the elbow in elbow extension (A). Subluxated ulnar nerve with the elbow in flexion (B). |
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|Figure 2: Ulnar nerve in the anatomic position with the elbow in extension (A). Subluxated ulnar nerve with the elbow in flexion (B). |
All elbows demonstrated dynamic subluxation of the ulnar nerve over the medial epicondyle (Figure 2). In 11 elbows (61%), a muscle anomaly was identified at the time of surgery (Table 3). In addition to ulnar nerve subcutaneous transposition, all muscular anomalies were corrected at the time of surgery (Table 4). Three elbows demonstrated an anconeus epitrochlearis muscle, which was resected in all cases (Figure 3). The other 8 elbows had anomalies of the medial triceps, which were addressed surgically (Figure 4). Five elbows had a large medial head of the triceps, which displaced over the medial epicondyle with elbow flexion, pushing the ulnar nerve from posterior to anterior out of the groove. Two elbows had an anomalous insertion of the medial triceps tendon onto the medial portion of the olecranon, and 1 elbow demonstrated an accessory tendon that inserted medially as well. In all cases, the medial triceps anomaly was corrected with excision (n=1) or lateral transposition (n=7) to the posterior or lateral aspect of the triceps. Other structures released are listed in Table 5. Six elbows had a snapping triceps.
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| ||Figure 3: Anconeous epitrochlearis (black arrow) before (A) and after resection (B). Figure 4: Elbow showing an abnormal medial head of the triceps. |
No operative complications were observed. Follow-up averaged 17 months (range, 6 weeks to 48 months). The average VAS for pain significantly improved from 6.0 preoperatively to 2.0 at final follow-up (P<.05). Six of 18 elbows (33%) had persistent pain at last follow-up, but all were rated as <3, and none were described as a functional limitation. None had a palpable subluxating ulnar nerve at follow-up. All patients achieved a full ROM of at least 30° to 130°. Average extension was 4° (range, 0°-20°), and average flexion was 145° (range, 130°-150°). None required further operative intervention to our knowledge.
Childress3 first reported on subluxation of the ulnar nerve at the elbow in 1956. He first diagnosed the condition in himself and subsequently examined 1000 other patients. He found that 16.2% of patients demonstrated ulnar nerve subluxation. Of those with ulnar nerve subluxation, 21% had symptoms of ulnar neuritis. Childress3 concluded that ulnar nerve subluxation is likely due to loose anchorage of the nerve in the cubital tunnel. Symptoms of ulnar neuropathy were thought to be due to friction neuritis or an increased likelihood of direct trauma as a result of the more superficial position of the subluxated nerve. Childress3 concluded that submuscular transposition was curative for cases with ulnar neuritis.
Several case reports document ulnar nerve subluxation as a result of various etiologies including laxity of the flexor carpi ulnaris retinaculum, congenital hypoplasia of the medial epicondyle, muscular anomalies, and posttraumatic changes.1-4,12,13 Other authors have investigated the muscular variations around the medial epicondyle and their relationship to ulnar neuropathy at the elbow.14-23 Dellon14 studied 64 cadavers and found that ulnar nerve subluxation was present in 28% of the specimens. Similarly, 28% of the specimens demonstrated the presence of a large medial head of the triceps extending into the floor of the cubital tunnel. Seventy-seven percent of these specimens also demonstrated subluxation of the ulnar nerve.
Variations in the triceps musculature has been associated with other medial elbow pathology.24-36 These variations are relatively common and can result in medial elbow pain, ulnar neuropathy, or symptomatic snapping. Spinner et al31,36 have reported on the concurrent conditions of dislocation of the medial triceps and the ulnar nerve at the elbow. In their series, 70% of symptomatic patients presented with medial elbow pain with or without ulnar nerve symptoms. Fifty-nine percent of symptomatic patients presented with ulnar neuropathy. In our study, ulnar nerve subluxation was associated with a snapping medial triceps in 6 patients (33%), thus clinical suspicion must be maintained for both entities or treatment failures may occur. Other authors have similarly documented incomplete resolution of symptoms by failure to address the anatomic anomaly.37-41
In our study, of the 11 elbows that demonstrated muscular anomalies, 2 revealed an anconeus epitrochlearis muscle. The anconeus epitrochlearis is also known as the subanconeus muscle, anconeus internus, or anconeus epitrochleo-olecranonis. It originates on the medial epicondyle and inserts on the olecranon. It is commonly thought to be an atavistic muscle located at the proximal portion of the cubital tunnel. Its presence has been associated with ulnar nerve compression at the elbow.15,19,20,22,23 While previous authors have not reported ulnar nerve subluxation in the presence of an anconeus epitrochlearis, both in our study demonstrated subluxation. We observed that the muscle belly fills the cubital tunnel proximally, effectively pushing the nerve out of the groove. There is a trend toward higher incidence in short, muscular men, often weight lifters. An abnormal muscular insertion in the setting of muscular hypertrophy may put these patients at risk for ulnar nerve subluxation at the elbow.
Eight of our 11 noted muscular anomalies involved the triceps muscle or tendon. In all cases, the medial triceps anomaly was corrected with excision or lateral transposition of the offending structure. Other authors have demonstrated that failure to recognize and address subluxation of the ulnar nerve and/or the medial triceps can result in persistent elbow pain and ulnar nerve symptoms.31
Of the 6 elbows without muscular anomalies, 2 patients had anatomic malalignment resulting from previous trauma. These patients underwent corrective osteotomy in addition to ulnar nerve transposition, which ultimately resulted in relief of symptoms.
In addition to clinical examination, imaging studies can be helpful in making the diagnosis. Both ultrasound and MRI techniques have reported value in the diagnosis of ulnar nerve subluxation.42-44 Because ulnar nerve subluxation is a dynamic event occurring with elbow flexion, it is often necessary to obtain the MRI sequences in both elbow extension and flexion to demonstrate the pathology. If the clinical examination is not conclusive, we favor the use of MRI to also assess for possible anatomic or structural anomalies.
Our study has limitations common to a retrospective chart review. Not all patients with subluxating ulnar nerves may have been identified due to coding aberrations. Variations in documentation, clinical examination, diagnostic approach, and surgical procedure all limit the internal consistency of the study. Additionally, elbow pain may have been caused by other etiologies that coexisted with an asymptomatic subluxating ulnar nerve such as snapping triceps, medial epicondylitis, or osteoarthritis. However, for snapping triceps, an ulnar nerve transposition is still usually performed. Treatment of the coexisting pathology may have resulted in relief of pain. No validated outcome measure was consistently used, thus outcomes were limited to pain relief, ROM, operative complications, and further procedures. Despite these limitations, we feel these data provide new and important information on the treatment of subluxating ulnar nerve syndrome, and further investigation is warranted.
Ulnar nerve subluxation, when symptomatic, presents most commonly as medial elbow pain and paresthesias in the ulnar nerve distribution. This occurs in a relatively young patient population and is frequently associated with muscular anomalies about the medial elbow. The diagnosis is made primarily by clinical examination, but adjunctive imaging studies can be helpful if the clinical examination is equivocal. Nerve conduction studies were not found to be helpful. Successful surgical management is achieved by anterior subcutaneous transposition of the ulnar nerve with stabilization under a fascial sling and correction of anatomical variants.
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Drs Richard, Messmer, Wray, Garrigues, Goldner, and Ruch are from the Department of Orthopedic Surgery, Duke University Medical Center, Durham, North Carolina.
Drs Richard, Messmer, Wray, Garrigues, Goldner, and Ruch have no relevant financial relationships to disclose.
Correspondence should be addressed to: Walter H. Wray III, MD, Division of Orthopedic Surgery, Duke University Medical Center, 200 Trent Dr, Box 3956, Durham, NC 27710 (firstname.lastname@example.org).