Ultrasound evaluation of ulnar nerve anatomy in the pediatric population

Ultrasonographic evaluation of ulnar nerve morphology in patients with ulnar nerve instability

INTRODUCTION/AIMS

Ulnar nerve instability (UNI) in the retroepicondylar groove is described as nerve subluxation or dislocation. In this study, considering that instability may cause chronic ulnar nerve damage by increasing the friction risk, we aimed to examine the effects of UNI on nerve morphology ultrasonographically.

METHODS

Asymptomatic patients with clinical suspicion of UNI were referred for further clinical and ultrasonographic examination. Based on ulnar nerve mobility on ultrasound, the patients were first divided into two groups: stable and unstable. The unstable group was further divided into two subgroups: subluxation and dislocation. The cross-sectional area (CSA) of the nerve was measured in three regions relative to the medial epicondyle (ME).

RESULTS

In the ultrasonographic evaluation, UNI was identified in 59.1% (52) of the 88 elbows. UNI was bilateral in 50% (22) of the 44 patients. Mean CSA was not significantly different between groups. A statistically significant difference in ulnar nerve mobility was found between the group with CSA of <10 versus ≥10 mm2 (p = .027). Nerve instability was found in 85.7% of elbows with an ulnar nerve CSA value of ≥10 mm2 at the ME level.

DISCUSSION

The probability of developing neuropathy in patients with UNI may be higher than in those with normal nerve mobility. Further prospective studies are required to elucidate whether asymptomatic individuals with UNI and increased CSA may be at risk for developing symptomatic ulnar neuropathy at the elbow.

Hearing and Seeing Nerve/Tendon Snapping: A Systematic Review on Dynamic Ultrasound Examination

Nerve/tendon snapping can occur due to their sudden displacement during the movement of an adjacent joint, and the clinical condition can really be painful. It can actually be challenging to determine the specific anatomic structure causing the snapping in various body regions. In this sense, ultrasound examination, with all its advantages (especially providing dynamic imaging), appears to be quite promising. To date, there are no comprehensive reviews reporting on the use of dynamic ultrasound examination in the diagnosis of nerve/tendon snapping. Accordingly, this article aims to provide a substantial discussion as to how US examination would contribute to 'seeing' and 'hearing' these pathologies' different maneuvers/movements.

Ultrasonography of the pediatric elbow

Ultrasound of the elbow can be incorporated into routine pediatric practice in the radiology department, emergency department, orthopedic clinic, and interventional suite. Ultrasound is complementary to radiography and magnetic resonance imaging for the evaluation of elbow pain in athletes with overhead activities or valgus stress, focusing on the ulnar collateral ligament medially and capitellum laterally. As a primary imaging modality, ultrasound can be used for a variety of indications including inflammatory arthritis, fracture diagnosis, and ulnar neuritis/subluxation. Ultrasound is also well-suited to guide diagnostic and therapeutic elbow joint interventions with precise localization of anatomic landmarks and needle placement. Here, we describe technical aspects of elbow ultrasound and illustrate its application in pediatric patients from infants to teen athletes.

A less invasive operative method using a medial cannulated cancellous screw and single plate fixation for the treatment of transcondylar fracture of the humerus in elderly patients in multicenter (TRON group) study

BACKGROUND

Double plate fixation for transcondylar fracture (TCF) tends to be more invasive to the soft tissue, and often carries a higher risk of postoperative complications, including ulnar nerve neuropathy. This study presents the outcomes of TCF of the distal humerus between patients treated with a single plate and cannulated cancellous screw fixation and patients treated with double plate fixation.

METHODS

Between 2011 and 2021, 371 cases involving treatment of distal humeral fracture were recorded in our multicenter (named TRON group) database. Patients of ≥ 65 years of age with TCF treated with opeb n reduction and internal fixation were included. Clinical outcomes were assessed by the Mayo elbow performance score, range of motion, and total elbow arc joint. Complications included fracture-related infection (FRI) and ulnar neuropathy.

RESULTS

There were significant differences in the average operative time (CCS group vs. Plate group: 119.0 min vs. 186.5 min; p < 0.001) and average tourniquet time (CCS group vs. Plate group: 91.5 min vs. 121.0 min; p < 0.001). FRI occurred as a complication in the Plate group (n = 6). The rates of FRI did not differ to a statistically significant extent (CCS group vs. Plate group: 0% vs. 9.2%; p = 0.477). No patients underwent reoperation. The rate of sensory symptoms in the Plate group was higher than that in the CCS group (CCS group: none [n = 25], numbness [n = 1] vs. Plate group: none [n = 57], numbness [n = 15], sensory depression [n = 2]; p = 0.039).

DISCUSSION

Among patients of ≥ 65 years of age with TCF, the clinical outcomes of patients treated with medial CCS and lateral/posterolateral plate did not differ from those of patients who received double plate fixation, and the former treatment was associated with significantly fewer complications, including ulnar nerve palsy. In addition to double plate fixation, this less invasive method of medial CCS and single plate fixation should be considered as a treatment option for TCF in elderly patients.

A Mini-Open Approach to Medial Pinning in Pediatric Supracondylar Humeral Fractures May Be Safer Than Previously Thought

BACKGROUND

Displaced pediatric supracondylar humeral fractures (SCHFs) are stabilized after reduction by smooth pins. Although some SCHFs are biomechanically stable after lateral-only entry pinning (lateral pinning), an additional medial entry pin (cross-pinning) confers superior stabilization in some SCHFs. There is a recognized risk of iatrogenic ulnar nerve injury with medial entry pinning. The best existing evidence has estimated an iatrogenic ulnar nerve injury rate of approximately 3.4% in cross-pinning. In similar studies, the rate of iatrogenic nerve injury (all nerves) in lateral pinning is estimated at 1.9%. This study aimed to use a large, single-center, single-technique (mini-open) retrospective case series to determine the rate of iatrogenic ulnar nerve injury in cross-pinning.

METHODS

Patients undergoing percutaneous cross-pinning via the mini-open technique for SCHFs from 2007 to 2017 were retrospectively reviewed. Injury characteristics, operative variables, fixation technique, and complications, such as iatrogenic nerve injury, were recorded. Patients who underwent operative treatment at another hospital, had no postoperative follow-up, or died due to polytrauma were excluded.

RESULTS

In this study, 698 patients undergoing cross-pinning during the study period were identified. Patients treated with cross-pinning had severe fractures, including a total of 198 preoperative neurovascular injuries (28.4%), 32 patients (4.6%) with skin tenting, and 19 patients (2.7%) with open fractures. Iatrogenic nerve injury was reported in 3 cases (0.43%), all of which affected the ulnar nerve. In 2 of 3 cases of iatrogenic nerve injury, the ulnar nerve symptoms resolved at a mean follow-up of 15 weeks.

CONCLUSIONS

The mini-open approach for medial pin insertion is safer than previous estimates. Here, in the largest single-center study of cross-pinning for SCHFs, the iatrogenic ulnar nerve injury rate of 0.43% was nearly 10 times lower than estimated rates from recent meta-analyses. Considering all nerves, the iatrogenic injury rate for this cross-pinning cohort was also lower than the estimated iatrogenic nerve injury rate for lateral pinning.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

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.

Surgical Technique: Closed Reduction and Percutaneous Pinning of Posterolaterally Displaced Supracondylar Humerus Fractures

Gartland type III posterolateral (IIIB) supracondylar humerus fractures are common among the pediatric population and can lead to concomitant injury, including compromise of the brachial artery and median nerve and long-term deformity, such as cubitus varus. These fractures can be difficult to reduce, and there is little consensus regarding the optimal technique for closed reduction and percutaneous pinning. Here, we discuss the management of Gartland III posterolateral supracondylar humerus fractures, including an in-depth technical description of the methods of operative fixation. We describe a lateral pin-only fixation technique for Gartland III posterolateral supracondylar humerus fractures that uses the intact periosteum during reduction of the distal fragment to assist in realigning the medial and lateral columns anatomically. We also discuss a safe method for placing a medial-based pin if there is persistent rotational instability at the fracture site after placement of the laterally based pins.

Ulnar nerve subluxation and dislocation: a review of the literature

The pathogenesis of ulnar nerve subluxation and dislocation is widely debated. Upon elbow flexion, the ulnar nerve slips out of the groove for the ulnar nerve, relocates medial or anterior to the medial epicondyle, and returns to its correct anatomical position upon extension. This chronic condition can cause neuritis or neuropathy; however, it has also been suggested that it protects against neuropathy by reducing tension along the nerve. This article reviews the extant literature with the aim of bringing knowledge of the topic into perspective and standardizing terminology.

Establishing Safe Zones to Avoid Nerve Injury in the Approach to the Humerus in Pediatric Patients: A Magnetic Resonance Imaging Study

BACKGROUND

The surgical anatomy of upper-extremity peripheral nerves in adults has been well described as "safe zones" or specific distances from osseous landmarks. In pediatrics, relationships between nerves and osseous landmarks remain ambiguous. The goal of our study was to develop a model to accurately predict the location of the radial and axillary nerves in children to avoid iatrogenic injury when approaching the humerus in this population.

METHODS

We conducted a retrospective review of 116 magnetic resonance imaging (MRI) scans of entire humeri of skeletally immature patients; 53 of these studies met our inclusion criteria. Two independent observers reviewed all scans. Arm length was measured as the distance between the lateral aspect of the acromion and the lateral epicondyle. We then calculated the distances (defined as the percentage of arm length) between the radial nerve and distal osseous landmarks (the medial epicondyle, transepicondylar line, and lateral epicondyle) as well between the axillary nerve and the most lateral aspect of the acromion.

RESULTS

The axillary nerve was identified at a distance equaling 18.6% (95% confidence interval [CI], ±0.62%) of arm length inferior to the lateral edge of the acromion. The radial nerve crossed (1) the medial cortex of the posterior part of the humerus at a distance equaling 63.19% (95% CI: ±0.942%) of arm length proximal to the medial epicondyle, (2) the middle of the posterior part of the humerus at a distance equaling 53.9% (95% CI: ±1.08%) of arm length proximal to the transepicondylar line, (3) the lateral cortex of the posterior part of the humerus at a distance equaling 45% (95% CI: ±0.99%) of arm length proximal to the lateral epicondyle, and (4) from the posterior to the anterior compartment at a distance equaling 35.3% (95% CI: ±0.92%) of arm length proximal to the lateral epicondyle. A strong linear relationship between these distances and arm length was observed, with an intraclass correlation coefficient of >0.9 across all measurements.

CONCLUSIONS

The positions of the radial and axillary nerves maintain linear relationships with arm lengths in growing children. The locations of these nerves in relation to palpable osseous landmarks are predictable.

CLINICAL RELEVANCE

Knowing the locations of upper-extremity peripheral nerves as a proportion of arm length in skeletally immature patients may help to avoid iatrogenic injuries during surgical approaches to the humerus.

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.

Results of crossed versus lateral entry K-wire fixation of displaced pediatric supracondylar humeral fractures: A systematic review and meta-analysis

PURPOSE

Supracondylar humeral fractures (SCHF) are among the most common injuries in children. The aim of this systematic review was to investigate functional and radiographic outcome after crossed and lateral K-wire fixation for displaced extension-type SCHF, and complications related to the type of K-wire construction used.

METHODS

RCTs and prospective comparative cohorts on the functional outcome and complications after fracture reduction and K-wire fixation were identified in MEDLINE, Embase, Web of Science and the Cochrane Library.

RESULTS

Thirteen studies were identified, including 1158 patients in seven RCTs and six prospective comparative cohorts. According to the Flynn criteria, there was no difference in outcome between the K-wire configurations (Relative Risk 1.07). Loss of reduction occurred in 27 (11.6%) of 232 patients treated with crossed K-wires, and in 35 (12.4%) of 282 patients treated with lateral entry K-wires. Twenty (4.1%) of 493 patients in the crossed group were diagnosed with iatrogenic ulnar nerve injury, compared with 2 (0.3%) of 666 patients in the lateral entry group. The overall incidence of persistent ulnar nerve related complaints was 3.5/1000.

CONCLUSIONS

Crossed and lateral entry pin fixation of SCHF result in similar construct stability and functional outcome. Although ulnar nerve injury was three times more likely in the crossed K-wire group, the overall incidence of this complication was very low. The available evidence does not support the use of either approach for daily practice. If the surgeon wishes to avoid all potential risk of iatrogenic ulnar nerve injury, the lateral K-wire approach is safest.

Applications of musculoskeletal ultrasonography in pediatric patients

Ultrasonography is an excellent adjunct to other musculoskeletal imaging tools utilized in the pediatric population and in some instances offers advantages over CT and MRI. It permits dynamic examination of anatomic structures and assists in guiding minimally invasive procedures. In the lower extremity, ultrasonography assists in screening for such disorders as developmental dysplasia of the hip and in detecting slipped capital femoral epiphysis and femoral acetabular impingement. In the neonatal spine, ultrasonography can identify unossified vertebral arches. Among other applications in the upper extremity, ultrasonography may be used in the evaluation and examination of peripheral nerve injuries and is a preferred modality for imaging the shoulder in infants with neonatal brachial plexus palsy. It is also considered an optimal adjunct for administration of botulinum toxin-A in children with cerebral palsy. The portability, relative low cost, lack of radiation, and absence of known contraindications enhances the utility of ultrasonography in pediatric orthopaedics.

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

BACKGROUND

We investigated the dynamics of the ulnar nerve during elbow flexion and the relationships between these dynamics and the morphology of the ulnar nerve groove in healthy individuals.

MATERIALS AND METHODS

Twenty healthy volunteers (40 elbows) underwent ultrasonographic examination of the ulnar nerve at the elbow. We measured the breadth and depth of the ulnar nerve groove at 90° of elbow flexion and calculated the depth-to-breadth ratio. We recorded the distance from the trochlea of the humerus to the nerve and the short-axis diameter of the nerve at 30°, 60°, 90°, and 120° of elbow flexion. We calculated the medial shift and flattening of the ulnar nerve at each angle relative to 30° of flexion, compared the values among the different angles, and compared the depth-to-breadth ratio with the location, medial shift, and flattening ratio of the ulnar nerve.

RESULTS

The medial shift was significantly greater at 120° than at other angles (P < .001). Flattening increased with increasing elbow flexion and was significantly different at 60°, 90°, and 120° (all P < .001). The flattening ratios were significantly correlated with the depth-to-breadth ratio at 120° (r = -0.43, P = .005).

CONCLUSIONS

The ulnar nerve moves medially and is flattened with the elbow flexed between 90° and 120°. When the ulnar nerve groove is shallow, high degrees of elbow flexion result in flattening of the ulnar nerve in the groove.