MR imaging of the postsurgical cubital tunnel: an imaging review of the cubital tunnel, cubital tunnel syndrome, and associated surgical techniques

The relationship between diffusion tensor imaging and the clinical classification of cubital tunnel syndrome

The purpose of the study was to investigate the relationship between diffusion tensor imaging (DTI) and the clinical classification of cubital tunnel syndrome (CuTS). Ten patients with CuTS (7 men and 3 women; mean age: 52.7 years) and 5 patients without ulnar neuropathy (2 men and 3 women; mean age: 38.0 years) were enrolled in this retrospective study. Fifteen patients were clinically classified into three groups: "Normal", "1 and 2A", and "2B and 3" by an orthopedic surgeon using the modified McGowan stages. DTI was acquired using a 3.0-T MRI. Fractional anisotropy (FA) of the ulnar nerve was measured in slices covering 20 mm proximal to 20 mm distal to ulnar sulcus. Median FA values in each group were compared by Kruskal-Wallis and Steel-Dwass test (P < 0.05). Five patients with CuTS were classified as "1 and 2A" and five patients as "2B and 3". The FA values, proximal 12 mm to the ulnar sulcus were 0.486 ± 0.117, 0.425 ± 0.166 and 0.298 ± 0.0386 in the "Normal", "1 and 2A" and "2B and 3" groups, respectively. The FA values of patients classified as "Normal" were significantly higher than those classified as "2B and 3" (P = 0.0326 in Steel-Dwass test). FA proximal to the ulnar sulcus might be associated to the modified McGowan stages for the clinical classification of CuTS.

Ultrasound of the Ulnar Nerve: A Pictorial Review: Part 2: Pathological Ultrasound Findings

This is the second part of a two-part article in which we focus on the ultrasound (US) appearance of the pathological ulnar nerve (UN) and its main branches. Findings in a wide range of our pathological cases are presented with high-resolution US images obtained with the latest-generation US machines and transducers.

Cubital tunnel syndrome: anatomy, pathology, and imaging

Cubital tunnel syndrome (CuTS) is the second most common peripheral neuropathy in the upper limb. It occurs due to ulnar nerve compression within the fibro-osseous cubital tunnel at the elbow joint. Although CuTS is typically diagnosed clinically and with electrodiagnostic studies, the importance of imaging in evaluating the condition is growing. Knowing the typical imaging findings of ulnar nerve entrapment is necessary for precise diagnosis and proper treatment. In this article, we focus on the clinical features, workup and complex imaging of the "anatomic" cubital tunnel and relevant pathological entities.

The role of imaging in focal neuropathies

Electrodiagnostic testing (EDX) has been the diagnostic tool of choice in peripheral nerve disease for many years, but in recent years, peripheral nerve imaging has been used ever more frequently in daily clinical practice. Nerve ultrasound and magnetic resonance (MR) neurography are able to visualize nerve structures reliably. These techniques can aid in localizing nerve pathology and can reveal significant anatomical abnormalities underlying nerve pathology that may have been otherwise undetected by EDX. As such, nerve ultrasound and MR neurography can significantly improve diagnostic accuracy and can have a significant effect on treatment strategy. In this chapter, the basic principles and recent developments of these techniques will be discussed, as well as their potential application in several types of peripheral nerve disease, such as carpal tunnel syndrome (CTS), ulnar neuropathy at the elbow (UNE), radial neuropathy, brachial and lumbosacral plexopathy, neuralgic amyotrophy (NA), fibular, tibial, sciatic, femoral neuropathy, meralgia paresthetica, peripheral nerve trauma, tumors, and inflammatory neuropathies.

Ulnar neuropathy at the elbow: associations of pre-operative DTI parameters with clinical outcomes after cubital tunnel decompression

OBJECTIVES

To evaluate whether DTI parameters of the ulnar nerve at the elbow are associated with clinical outcomes in patients receiving cubital tunnel decompression (CTD) surgery for ulnar neuropathy.

METHODS

This retrospective study included 21 patients with cubital tunnel syndrome who received CTD surgery between January 2019 and November 2020. All patients underwent pre-operative elbow MRI, including DTI. Region-of-interest analysis was performed on the ulnar nerve at three levels around the elbow: above (level 1), cubital tunnel (level 2), and below (level 3). Fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) were calculated on three sections at each level. Clinical data on symptom improvement in respect to pain and tingling sensation after CTD were recorded. Logistic regression analysis was used to compare DTI parameters of the nerve at three levels and the entire nerve course between patients with and without symptom improvement after CTD.

RESULTS

After CTD, 16 patients showed improvement in symptoms, but five did not. ROC analysis of DTI parameters showed that AUCs of FA, AD, and MD were higher at level 1 than at levels 2 and 3, with FA showing the highest AUC (level 1: FA, 0.7104 [95% CI, 0.5206-0.9002] vs AD, 0.6521 [95% CI, 0.4900-0.8142] vs MD, 0.6153 [95% CI, 0.4187-0.8119]).

CONCLUSION

In patients who underwent CTD surgery for ulnar neuropathy at the elbow, the DTI parameters of FA, AD, and MD above the cubital tunnel level were associated with clinical outcomes, with FA showing the strongest associations.

KEY POINTS

• After CTD surgery for ulnar neuropathy at the elbow, persistent symptoms may be observed, depending on symptom severity. • DTI parameters of the ulnar nerve at the elbow showed differences in their capacity for discriminating between patients with and without symptom improvement following CTD surgery, with this capacity depending on the nerve level at the elbow. • FA, AD, and MD measured above the cubital tunnel on pre-operative DTI may be associated with surgical outcomes, with FA showing the strongest association (AUC at level 1, 0.7104 [95% CI, 0.5206-0.9002]).

Dynamic analysis of the ulnar nerve and cubital tunnel morphology using ultrasonography: a cadaveric study

BACKGROUND

The causes of ulnar neuropathy at the elbow are unclear. The authors hypothesized that the humeral trochlea protrudes into the cubital tunnel during elbow flexion and causes a dynamic morphologic change of the ulnar nerve in the cubital tunnel.

METHODS

An ultrasonic probe was fixed to the ulnar shafts of 10 fresh cadavers with an external fixator, and dynamic morphology of the cubital tunnel and ulnar nerve was observed. The distance from the Osborne band to the trochlea (OTD), distance from ulnar nerve center to the trochlea (UTD), and the short- and long-axis diameters of the nerve at 30°, 60°, 90°, and 120° of elbow flexion were recorded. We compared the OTD, UTD, and the flattening of the ulnar nerve at the different angles of flexion using single-factor analysis of variance. Correlation between the ulnar nerve flattering, OTD, and UTD was examined using Spearman correlation coefficient. A P value less than .05 was used to denote statistical significance.

RESULTS

Flattening of the ulnar nerve progressed with increasing elbow flexion and was significantly different between 0° and 60°, 90°, and 120° (P = .03 at 60°, P < .01 at 90° and 120°). OTD decreased with elbow flexion, and there was a significant difference at all elbow flexion angles (all P < .01). UTD decreased significantly from 0° flexion to 90° flexion (P = .03). Flattening of the nerve was significantly correlated with the OTD (r = 0.66, P < .01).

CONCLUSIONS

A positive correlation was found between the protrusion of the humeral trochlea into the cubital tunnel during elbow flexion and ulnar nerve flattening using cadaveric elbow and ultrasonography.

How to Report: Elbow MRI

The elbow is the least common of the main joints examined with magnetic resonance imaging (MRI), thus radiologists may be less familiar with writing these reports. This article addresses the main pathologies encountered in and around the elbow, emphasizing the specific features that need reporting and providing examples of terminology to use when describing these abnormalities.

Imaging the Postoperative Elbow

Evaluation of postoperative images of any joint can be a daunting task, and the elbow is no exception. Patients may be imaged with a complication of the repair, or the postoperative changes may be incidentally observed as the patient is imaged for other reasons. We divide the postoperative elbow into soft tissue procedures (covering ligament and tendon repairs, as well as compartmental release and nerve transposition), joint-related procedures (osteochondral lesion treatment, ostectomy, and joint replacement), and bone procedures (fracture fixation). We summarize the procedures and their indications, show normal imaging appearances, and finally cover common complications.

Possible points of compression of the ulnar nerve: Tricks and traps that await clinicians from an anatomical point of view

The ulnar nerve can be subject to numerous types of compression. The most common are cubital tunnel and ulnar tunnel syndromes, but there are many others with more uncommon etiologies. The existence of additional communicating branches, median nerve involvement, various types of injuries, and unusual anatomical variations can be a challenge for both diagnosis and treatment. This review presents a comprehensive depiction of ulnar nerve entrapment syndromes with particular reference to their anatomical background, risk factors, and clinical evaluation. Even common disorders can result from atypical morphological changes. It is important to be familiar with them as it is a key ability in daily medical practice.

Risk factors and outcomes in 385 cases of ulnar nerve submuscular transposition

Submuscular transposition (SMT) for treatment of ulnar nerve entrapment is commonly performed, however published comparisons of surgical techniques exclude a high proportion of the at-risk population encountered in real world practice. To examine the influence of risk factors on the clinical outcome following SMT we performed a retrospective review of all patients who underwent SMT, including patient self-reported outcome and Louisiana State University Medical Centre ulnar nerve grading scale. A total of 403 ulnar nerves were operated, with follow-up data available for 385 cases (359 patients). Risk factors (including smoking, diabetes, previous elbow trauma/pathology, subluxation, workers' compensation) were reported in 266 of 385 surgeries (69.09%). SMT was the primary procedure in 339 nerves (88.05%), revision procedure in 46 nerves (11.95%). At last follow up 91.05% reported symptomatic improvement. Nerve grade improvement in 71.09% of primary and 67.39% revision surgery (p = 0.605). No significant difference in improvement was identified between demographic and risk categories, except for patient reported improvement in those without peripheral neuropathy (90.59% vs 73.33%, p = 0.027), and those not improved were on average older than those improved (62.94 vs. 55.68 years, p = 0.012). Superficial infection occurred in 2.6% and there were no deep infections. Application of published exclusion criteria would have resulted in exclusion of ½-⅔ of our cohort. SMT in patients with a history of elbow trauma, diabetes, workers compensation, smoking history, nerve subluxation or revision surgery have similar outcomes compared to those without these factors, whilst improved results were observed in younger patients and those without peripheral neuropathy.

MRI of the ulnar nerve pre- and post-transposition: imaging features and rater agreement

OBJECTIVE

Determine the rater agreement of MRI features of the ulnar nerve pre- and post-transposition and association with recurrent symptoms.

MATERIALS AND METHODS

This IRB-approved retrospective cohort analysis examined 23 subjects who underwent elbow MRI pre- and post-ulnar nerve transposition from 1999 to 2018, 10 of whom developed recurrent symptoms. Pre- and post-transposition MRIs were evaluated by two blinded radiologists for ulnar nerve cross-sectional area, signal intensity, fascicular architecture, caliber change, and perineural scar. Inter-rater agreement was estimated using intraclass correlation coefficients (ICCs) for continuous variables and Gwet's agreement coefficient (AC) for categorical variables. Binary logistic regression modeling probed associations between imaging markers and symptom recurrence.

RESULTS

The ulnar nerve, post-operatively, demonstrated statistically significant increases in size (p < 0.001), signal intensity (p = 0.021), and abrupt caliber change (p = 0.024). None of the imaging features, except for higher signal intensity of the nerve pre-transposition as demonstrated by one rater, were predictive of symptom recurrence. Inter-rater agreement for cross-sectional area measurements of the ulnar nerve at the cubital tunnel was excellent (ICCs of 0.91 and 0.83). Substantial-to-excellent inter-rater agreement was observed pre-operatively for nerve signal intensity, caliber change, and fascicular architecture. Post-operatively, agreement on nerve signal intensity and perineural scar was excellent (ACs of 0.90 and 0.88), but only slight for caliber change (0.15).

CONCLUSION

Inter-rater agreement for qualitative and quantitative assessment of the ulnar nerve was generally robust. Post-transposition, the ulnar nerve was generally larger and more T2-hyperintense, but MRI features were not predictive of recurrent ulnar neuropathy, except for perhaps the signal intensity of the nerve pre-transposition.

Vascular compromise in a torsed transposed ulnar nerve case in support of intravenous contrast administration

Nerve torsion is a recognized etiology in brachial and peripheral neuropathy. Vascular compromise of peripheral nerves is uncommon given their unique vascular supply. Preoperative imaging diagnosis of nerve torsion and vascular compromise can be made in some cases, which impacts treatment. We present a previously unreported case of long segment torsion and vascular compromise of the ulnar nerve following anterior subcutaneous transposition with a description of the imaging findings based on the unique structure of the nerve and the presence of a blood nerve barrier (BNB) and a discussion of the potential vulnerability of a transposed and torsed nerve.

Magnetic resonance imaging of the elbow

Elbow pain can cause disability, especially in athletes, and is a common clinical complaint for both the general practitioner and the orthopaedic surgeon. Magnetic resonance imaging (MRI) is an excellent tool for the evaluation of joint pathology due to its high sensitivity as a result of high contrast resolution for soft tissues. This article aims to describe the normal imaging anatomy and biomechanics of the elbow, the most commonly used MRI protocols and techniques, and common MRI findings related to tendinopathy, ligamentous and osteochondral injuries, and instability of the elbow.