Dynamic analysis of the ulnar nerve in the cubital tunnel using ultrasonography

Ultrasonographic features of ulnar nerve instability around the elbow in fresh cadavers

Ultrasound (US) is commonly used to evaluate ulnar nerve instability (UNI) and snapping of the medial head of the triceps brachii muscle (ST). We aimed to determine the diagnostic accuracy of US in evaluating UNI, through cadaveric dissection, and to evaluate the US features and relationships of UNI and ST according to elbow flexion. Dynamic US was performed with elbow extension, 90° flexion, and full flexion positions on 18 elbows from 9 fresh cadavers. UNI was classified into N (normal), S (subluxation), and D (dislocation) types. On US exams, the following findings and parameters were evaluated: the presence of UNI and ST; the horizontal distance from the apex of the medial epicondyle (ME) to the margins of the UN and medial head of the triceps brachii muscle (ME_UN and ME_TB, respectively); cross-sectional area and flattening ratio (FR) of UN. After US, all cadavers were dissected to expose the UN and TB, and elbow flexion and extension were simulated to confirm UNI and ST. The gross anatomic findings of UNI and ST were consistent with the US findings. In extension and 90° flexion positions, all cases were type N. In full flexion position, types N and S occurred in 10 (56%) and 8 (44%) elbows, respectively. FR and ME_UN in 90° flexion position, FR, ME_UN, and ME_TB in full flexion position differed significantly between types S and N. Positive correlations were found between ME_UN and ME_TB in 90° flexion and full flexion positions. Dynamic US accurately assessed UNI and ST. UNI was positively correlated to medial TB movement.

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.

Risk factors of asymptomatic reduction of motor conduction velocity of the ulnar nerve across the elbow

INTRODUCTION

The aim of the study was to check the risk factors for subjects with motor conduction velocity (MCV) reduction of the ulnar nerve across the elbow without symptoms/signs of ulnar neuropathy at the elbow (UNE) using a database of a previous multicenter case-control study on UNE patients.

METHODS

From the previous database, we extracted all asymptomatic UNE (A-UNE) and matched for age and sex with a control and UNE groups with a ratio of 1:2. Anthropometric factors were measured and all participants filled in a questionnaire on demographic, lifestyle factors, and medical history. One-sample proportion test and univariate and multivariate logistic regression analyses were performed.

RESULTS

We enrolled 64 A-UNE, 124 UNE, and 124 controls (mean age 53 years). There were more males with A-UNE than females (74.2%). The predominantly or exclusively concerned side of A-UNE was the right. Logistic regression showed that A-UNE was associated with diabetes (OR = 2.99, 95% CI = 1.21-7.39) and width of cubital groove (CGW) (OR = 0.89, 95%  CI = 0.81-0.97).

DISCUSSION

Risk factors for A-UNE are different from UNE. The prevalence of right side in A-UNE was not due to particular elbow postures. Diabetes is a risk factor, probably because MCV reduction of the ulnar nerve across the elbow was an early manifestation of asymptomatic polyneuropathy in diabetes. A-UNE is associated with narrow CGW as already demonstrated in UNE, even if the OR was higher in UNE than in A-UNE. Only future longitudinal studies will be able to check whether the A-UNE subjects develop symptoms and signs of true mononeuropathy with time.

High-resolution ultrasound demonstrates in vivo effects of wrist movement on the median nerve along the forearm

INTRODUCTION/AIMS

High-resolution ultrasound (HRUS) is the imaging method of choice to visualize peripheral nerve size, structure, and biomechanical performance. The purpose of this study was to show and quantify the effects of active and passive wrist alignment on median nerve (MN) cross-sectional area (CSA) along the forearm in a healthy population.

METHODS

Sixteen healthy volunteers underwent HRUS of their dominant forearm (n = 16, 10 males, 6 females, 18-55 y of age). Median nerve's CSA was assessed at four defined areas on the forearm in relation to active and passive wrist alignment.

RESULTS

Changes in wrist alignment were significantly associated with MN CSA (P < .001), regardless if the wrist was moved actively or passively. MN CSA was lowest during passive extension of the wrist joint and highest during passive flexion of the wrist joint (range: 4.5-23.2 mm² ).

DISCUSSION

The elasticity of nerve tissue, the loose connective tissue between the fascicles, and the paraneurium allow peripheral nerves to adapt to longitudinal strain. HRUS enables the demonstration of significant median nerve CSA changes along the forearm during active and passive wrist movement in healthy volunteers.

Management of Recalcitrant Cubital Tunnel Syndrome

Cubital tunnel syndrome is a common upper extremity compressive neuropathy. Recalcitrant cubital tunnel syndrome poses diagnostic and treatment challenges. Potential etiologies of persistent or recurrent symptoms after surgical treatment include an inaccurate preoperative diagnosis, incomplete nerve decompression, iatrogenic injury, postsurgical perineural adhesions, irreversible nerve pathology, or conditions associated with secondary nerve compression. Confirmation of recalcitrant ulnar nerve pathology relies on a thorough history to consider symptoms and chronology, careful examination to quantify nerve function and to assess for focal nerve provocation, and objective testing to highlight a possible nerve lesion such as ultrasonography and electrodiagnostic testing. Conservative treatment may provide symptomatic relief; however, surgical management such as revision neuroplasty, neurolysis, nerve reconstruction, and/or anterior transposition may be indicated. Optimizing the biology of the local nerve environment is critical. No surgical treatment procedure has shown superiority over another; however, individualized treatment is emphasized to improve symptoms and maximize nerve recovery potential.

Ultrasonographic prevalence of ulnar nerve displacement at the elbow in young baseball players

BACKGROUND

Overhead-throwing athletes are at risk of elbow injury because of valgus stress, leading to unstable ulnar nerves and neuropathy. Studies regarding ulnar nerve damage/displacement have been performed primarily in adults.

OBJECTIVE

To determine the prevalence and related factors associated with ulnar nerve displacement at the elbow in young baseball players.

DESIGN

Cross-sectional study.

PARTICIPANTS

Youth baseball players ages 10-12 years were eligible to participate. Exclusion criteria were history of neuropathic pain, trauma, or prior surgery of the upper limb. Fifty-seven participants were eligible for inclusion in the study.

MAIN OUTCOME MEASUREMENTS

Demographic data and ultrasonography findings of ulnar nerve dynamics at the cubital tunnel were analyzed in a total of 114 elbows. Elbows were grouped into nondislocation and displacement (subluxation or dislocation) groups according to ultrasound findings. Logistic generalized estimating equations were used to identify factors associated with ulnar nerve displacement.

RESULTS

Thirty-six (31.6%) elbows demonstrated sonographic findings of ulnar nerve displacement, with 13 (11.4%) subluxations and 23 (20.2%) dislocations. Fourteen (24.6%) participants experienced nerve displacement in the dominant elbow only, whereas nerve displacement in both elbows occurred in 11 (19.3%) participants. Nerve displacement in the nondominant elbow only was not observed. Hand dominance and tenderness of the arcade of Struthers' were factors associated with ulnar nerve displacement (odds ratio, 2.81, and 9.73; 95% confidence interval, 1.34-5.91 and 2.45-38.68; p = .006 and .001, respectively).

CONCLUSION

One-third of the young baseball players evaluated had ultrasonographic findings compatible with ulnar nerve displacement at the elbow. Hand dominance and tenderness of Struthers arcade were the only factors associated with ulnar nerve displacement. Ultrasound may help identify patients with ulnar nerve displacement and contribute to the understanding of its pathophysiology in young baseball players.

Comorbidities, anthropometric, demographic, and lifestyle risk factors for ulnar neuropathy at the elbow: A case control study

We performed a prospective multicenter case-control study to explore the association between ulnar neuropathy at elbow (UNE) and body and elbow anthropometric measures, demographic and lifestyle factors, and comorbidities. Cases and controls were consecutively enrolled among subjects admitted to four electromyography labs. UNE diagnosis was made on clinical and neurographic findings. The control group included all other subjects without signs/symptoms of ulnar neuropathy and with normal ulnar nerve neurography. Anthropometric measurements included weight, height, waist, hip circumferences, and external measures of elbow using a caliper. The participants filled in a self-administered questionnaire on personal characteristics, lifestyle factors, and medical history. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) by fitting unconditional logistic regression models adjusted by center and education level. We enrolled 220 cases (males 61.8%; mean age 51.7 years) and 460 controls (47.4% males; mean age 47.8 years). At multivariable analysis, UNE was associated to male gender (OR = 2.4, 95%CI = 1.6-3.7), smoking habits (>25 pack-years (OR = 2.3, 95%CI = 1.3-4.1), body mass index (OR = 1.05, 95%CI 1.01-1.10), polyneuropathies (OR = 4.1, 95%CI 1.5-11.5), and leaning with flexed elbow on a table/desk (OR = 1.5, 95%CI 1.0-2.2). Cubital groove width (CGW) turned out to be negatively associated with UNE (OR = 0.80, 95%CI = 0.74-0.85). Our study suggests that some personal factors especially anthropometric measures of the elbow may play a role in UNE pathogenesis as the measures of wrist in CTS. We demonstrated that for each millimeter of smaller CGW the risk of idiopathic UNE increases of 25%.

Value of ultrasonography in the diagnosis of carpal tunnel syndrome-a new ultrasonographic index in carpal tunnel syndrome diagnosis: A clinical study

We analyze the effectiveness of ultrasonography in diagnosing carpal tunnel syndrome (CTS) and propose the use of sonographic index of median nerve (MN) in carpal tunnel (SIMNCT) in a diagnostic algorithm and in establishing a scale of severity.We studied a group of 344 patients with CTS symptoms, examining them by ultrasound. We measured in all patients, on the affected hand: the size of the cross-sectional area of the MN at carpal tunnel (CT) inlet and outlet, nerve morphology at passage through CT, the vertical thickness of the MN entering into the CT - G1, the lowest vertical thickness into the CT or leaving the CT - G2, the thickness of the MN in the transversal plane as entering in the CT - L. Normal values were considered the similar measurements taken on the healthy hand and we established as normal SIMNCT = 16%. We proposed the formula SIMNCT = 100% (1-G2/G1) in order to calculate the index.Statistics show a significant sensitivity of SIMNCT (P < .0001) compared with cross-sectional area (CSA) and flattening ratio in the diagnosis of CTS. Analyzing the SIMNCT developed by us, we demonstrated a sensitivity of 94.81% and a specificity of 99.66% in CTS diagnosis. Thereby, we propose a CTS severity classification: normal = 16%, mild = 16-19%, moderate = 19% to 28%, severe = 28% to 50%, very severe > 50%.Ultrasonography is an effective method of studying the morphology of the tunnel and compressed nerve at various CTS stages and determining the cause of compression. The SIMNCT is a valuable and practical indicator and it can be used in the CTS diagnosis.

The external elbow measure as surrogate of the anatomical width of cubital groove and possible risk factor of ulnar neuropathy at the elbow

Introduction: There are no studies on elbow anthropometry in ulnar neuropathy at the elbow (UNE). We aimed to test the interrater agreement of external elbow measurements with caliper, the matching of external width of cubital groove (WCG) measures with those obtained through conventional radiography (XR) and ultrasonography (US). The final aim was to evaluate the differences of anthropometric elbow and body measures between UNE cases and controls with multicenter prospective study.Materials and methods: After common training of five observers for external elbow and body anthropometric measurements, we assessed the interrater agreement of measures in a single blind measurement session in 16 healthy volunteers. Then we verified if external WCG measures in eight and four of the above 16 subjects matched with those obtained with US and XR. Finally, we enrolled 40 consecutive idiopathic UNE cases in four electromyographic labs matched for sex and age with 40 controls to evaluate the differences of anthropometric measures.Results: There was high interrater agreement of all anthropometric body and elbow measures (Kendal's and interclass correlation coefficients between 0.84 and >0.9). We found high relations between WCG caliper measures and those obtained with US and XR (r > 0.9). WCG was smaller in cases than in controls (13.2 vs.15.7 mm, p < 0.001). There were no differences in body anthropometric measures (BMI and waist-to-hip ratio).Conclusion: The external measurement of WCG is reliable and reproducible and may be risk factor of UNE. Future studies should be performed in lager samples evaluating the relations with lifestyle and occupational factors.

Ultrasound Measurements and Assessments of the Ulnar Nerve at the Elbow and Cubital Tunnel: A Scoping Review

Ulnar neuropathy at the elbow (UNE) is the second most frequent peripheral nerve entrapment neuropathy in the upper extremity. The diagnosis is determined through a combination of history, physical examination, and electrodiagnostic testing. However, the use of high-resolution sonography is increasing, with sonographic measurements of ulnar nerve dimension established as a reliable diagnostic criterion for UNE. Sonographic imaging can describe anatomical features beyond ulnar nerve size, and therefore additional observations could potentially be used in UNE diagnosis and treatment follow-up. This review was a scoping of the literature on different sonographic measurements and assessments that have been reported to evaluate the ulnar nerve and cubital tunnel. This should provide a guide to scanning protocols for sonographers.

Ulnar nerve instability in the cubital tunnel of asymptomatic volunteers

PURPOSE

Ulnar nerve instability (UNI) in the cubital tunnel is defined as ulnar nerve subluxation or dislocation. It is a common disorder that may be noted in patients with neuropathy or in the asymptomatic. Our prospective, single-site study utilized high-resolution ultrasonography (US) to evaluate the ulnar nerve for cross-sectional area (CSA) and measures of shear-wave elastography (SWE). Mechanical algometry was obtained from the ulnar nerve in the cubital tunnel to assess pressure pain threshold (PPT).

METHODS

Forty-two asymptomatic subjects (n = 84 elbows) (25 males, 17 females) aged 22-40 were evaluated. Two chiropractic radiologists, both with 4 years of ultrasound experience performed the evaluation. Ulnar nerves in the cubital tunnel were sampled bilaterally in three different elbow positions utilizing US, SWE, and algometry. Descriptive statistics, two-way ANOVA, and rater reliability were utilized for data analysis with p ≤ 0.05.

RESULTS

Fifty-six percent of our subjects demonstrated UNI. There was a significant increase in CSA in subjects with UNI (subluxation: 0.066 mm² ± 0.024, p = 0.027; dislocation: 0.067 mm² ± 0.024, p = 0.003) compared to controls (0.057 mm² ± 0.017) in all three elbow positions. There were no significant group differences in SWE or algometry. Inter- and intra-observer agreements for CSA of the ulnar nerves within the cubital tunnel were assessed using intraclass correlation coefficient (ICC) and demonstrated moderate (ICC 0.54) and excellent (ICC 0.94) reliability.

CONCLUSIONS

Most of the asymptomatic volunteers demonstrated UNI. There was a significant increase in CSA associated with UNI implicating it as a risk factor for ulnar neuropathy in the cubital tunnel. There were no significant changes in ulnar nerve SWE and PPT. Intra-rater agreement was excellent for the CSA assessment of the ulnar nerve in the cubital tunnel. High-resolution US could be utilized to assess UNI and monitor for progression to ulnar neuropathy.

Anterior Subcutaneous Transposition of the Ulnar Nerve Affects Elbow Range of Motion: A Mean 13.5 Years of Follow-up

BACKGROUND

Surgical decompression of the ulnar nerve is effective for cubital tunnel syndrome. However, deep approaches may result in iatrogenic elbow stiffness. This long-term study was to evaluate the range of motion (ROM) of the elbow and functional outcomes after anterior subcutaneous transposition.

METHODS

A total of 115 patients (78 male and 37 female; mean age: 46.6 years) who underwent anterior subcutaneous transposition of the ulnar nerve between 2001 and 2005 were evaluated retrospectively; mean follow-up was 13.5 years. Elbow ROM was measured as flexion arc, flexion, and extension preoperatively and at the final follow-up, and compared via a mixed analysis of variance adjusting for age. Neuropathy was assessed preoperatively using a modified McGowan neuropathy grade and postoperatively using modified Wilson-Krout criteria. An ordinal logistic regression analysis used postoperative modified Wilson-Krout criteria as the outcome and preoperative factors as predictors.

RESULTS

Preoperative McGowan grades were Grade 1 in 14 patients (12.2%), Grade 2A in 28 (24.3%), Grade 2B in 53 (46.1%), and Grade 3 in 20 (17.4%) patients. Postoperatively, 66 patients (57.4%) had excellent results, 26 (22.6%) had good results, 16 (13.9%) had fair results, and 7 (6.1%) had poor results at the final follow-up, as per the Wilson-Krout criteria. There were no complications. Pre- and postoperative elbow ROM was significantly decreased in patients with previous trauma or surgery of the elbow compared with those without (P < 0.05). Anterior subcutaneous transposition of the ulnar nerve did not significantly affect elbow ROM regardless of previous trauma or surgical history nor preoperative ROM (P > 0.05), after adjusting for age. Patients with prolonged symptoms prior to surgery and worse neuropathy tended to have less satisfactory functional outcomes (P < 0.05), after adjusting for covariates.

CONCLUSIONS

Anterior subcutaneous transposition of the ulnar nerve is an effective and reliable treatment of cubital tunnel syndrome with satisfactory outcomes and minimal effect on elbow ROM.

Ultrasonographic and Electrophysiological Evaluation of Ulnar Nerve Instability and Snapping of the Triceps Medial Head in Healthy Subjects

OBJECTIVE

To evaluate the relationship between ulnar nerve instability and snapping of the triceps medial head during elbow flexion.

DESIGNS

Twenty-six healthy individuals were recruited. The primary outcome measures were ultrasonographic and electrophysiological parameters of the ulnar nerve. Ulnar nerve instability was classified into three types based on the degree of ulnar nerve movement: no dislocation (Type N), subluxation (Type S), and dislocation (Type D).

RESULTS

In the elbow 90-degree position, the incidences of Type N, S, and D were 41 (78.8%), 8 (15.4%), and 3 (5.8%) elbows, respectively; in the full flexion position, the incidences of Types N, S, and D were 24 (46.2%), 19 (36.5%), and 9 (17.3%) elbows, respectively. Spearman's correlation coefficients between ulnar nerve instability and snapping of the triceps medial head in the elbow 90-degree and full flexion positions were 0.808 and 0.889 (P < 0.001), respectively. The ulnar sensory response in Type S was of prolonged latency and decreased amplitude compared with that in Type N or D in the elbow full flexion position.

CONCLUSIONS

Ulnar nerve instability increased with elbow flexion and correlated with snapping of the triceps medial head. Ultrasonography of the ulnar nerve is an important tool in ulnar nerve instability assessment.

Ultrasound biomechanical anatomy of the soft structures in relation to the ulnar nerve in the cubital tunnel of the elbow

BACKGROUND

Chronic ulnar nerve entrapment worsened by elbow flexion is the most common injury, but rare painful conditions may also be related to ulnar nerve instability. The posterior bundle of the medial collateral ligament (pMCL) and the retinaculum, respectively form a soft floor and a ceiling for the cubital tunnel. The aim of our study was to dynamically assess these soft structures of the cubital tunnel focusing on those involved in the biomechanics of the ulnar nerve.

METHODS

Forty healthy volunteers had a bilateral ultrasonography of the cubital tunnel. Elbows were scanned in full extension, 45° and 90°, and maximal passive flexion. Morphological changes of the nerve and related structures were dynamically assessed on transverse views.

RESULTS

Both the pMCL and the retinaculum tightened with flexion. During elbow flexion, the tightening of the pMCL superficially moved the ulnar nerve remote from the osseous floor of the retroepicondylar groove. A retinaculum was visible in all 69 tunnels with stable nerves (86.3%), tightened in flexion, but absent in 11 tunnels with unstable nerves (13.7%). The retinaculum was fibrous in 60 elbows and muscular in nine, the nine muscular variants did not significantly influence the biomechanics of stable nerves. Stable nerves flattened in late flexion between the tightened pMCL and retinaculum, whereas unstable nerves transiently flattened when translating against the anterior osseous edge of the groove.

CONCLUSION

The retinaculum and the pMCL are key structures in the biomechanics of the ulnar nerve in the cubital tunnel of the elbow.

Entrapment and traumatic neuropathies of the elbow and hand: An imaging approach

Ultrasound and magnetic resonance imaging currently offer a detailed analysis of the peripheral nerves. Compressive and traumatic nerve injuries are the two main indications for imaging investigation of nerves with several publications describing the indications, technique and diagnostic capabilities of imaging signs. Investigation of entrapment neuropathies has three main goals, which are to confirm neuronal distress, search for the cause of nerve compression and exclude a differential diagnosis on the entire nerve. For traumatic nerve injuries, imaging, predominantly ultrasound, occasionally provides essential information for management including the type of nerve lesion, its exact site and local extension.

Altered Ulnar Nerve Kinematic Behavior in a Cadaver Model of Entrapment

BACKGROUND:

Ulnar nerve entrapment at the elbow is more than a compressive lesion of the nerve. The tensile biomechanical consequences of entrapment are currently marginally understood.

OBJECTIVE:

To evaluate the effects of tethering on the kinematics of the ulnar nerve as a model of entrapment neuropathy.

METHODS:

The ulnar nerve was exposed in 7 fresh cadaver arms, and markers were placed at 1-cm increments along the nerve, centered on the retrocondylar region. Baseline translation (pure sliding) and strain (stretch) were measured in response to progressively increasing tension produced by varying configurations of elbow flexion and wrist extension. Then the nerves were tethered by suturing to the cubital tunnel retinaculum and again exposed to progressively increasing tension from joint positioning.

RESULTS:

In the native condition, for all joint configurations, the articular segment of the ulnar nerve exhibited greater strain than segments proximal and distal to the elbow, with a maximum strain of 28 ± 1% and translation of 11.6 ± 1.8 mm distally. Tethering the ulnar nerve suppressed translation, and the distal segment experienced strains that were more than 50% greater than its maximum strain in an untethered state.

CONCLUSION:

This work provides a framework for evaluating regional nerve kinematics. Suppressed translation due to tethering shifted the location of high strain from articular to more distal regions of the ulnar nerve. The authors hypothesize that deformation is thus shifted to a region of the nerve less accustomed to high strains, thereby contributing to the development of ulnar neuropathy.