Anatomical basis of pronator teres for electromyography needle placement using ultrasonography

A Proposed Safe Electromyographic Needle Insertion Technique for the Flexor Pollicis Longus Muscle Using Arterial Pulse Palpation: Preliminary Study with Ultrasonography

Electromyographic needle access to the flexor pollicis longus (FPL) is challenging because of the risk of injuries to the superficial radial nerve (SRN) or radial artery (RA), which run close to the FPL. This study aimed to investigate the safe electromyographic needle insertion point of the FPL using a newly proposed RA pulse palpation method. Fifty forearms of 25 healthy individuals were studied. At the junction of the middle and distal third of the forearm, an RA pulse was palpated, and 5 mm lateral to the pulse was determined as the preliminary needle insertion point. The distance from the vertical virtual needle pathway to the RA and SRN was measured using ultrasonography. In ultrasonography, the distances from the needle pathway to the RA and the SRN were 3.4 ± 0.8 (range, 2.1–6.0) and 5.9 ± 1.8 (range, 2.4–9.4) mm, respectively. The depth of the FPL muscle was 8.4 ± 1.7 mm. Electromyographic needle insertion into the FPL can be safely performed using the RA palpation method. The needle insertion point is 5 mm lateral to the RA pulse at the level between the middle and distal third of the forearm.

Safety of Dry Needling of the Pronator Teres Muscle in Cadavers: A Potential Treatment for Pronator Syndrome

BACKGROUND

Entrapment of the median nerve at the pronator teres muscle can contribute to symptoms in the forearm and wrist. The pronator teres is also involved in patterns of spasticity observed in people who had suffered a stroke. Research on treatment efficacy with dry needling is scarce.

OBJECTIVE

To determine if a solid filiform needle safely penetrates the pronator teres muscle during the clinical application of dry needling.

DESIGN

A cadaveric descriptive study.

METHODS

Needle insertion of the pronator teres was conducted in ten cryopreserved forearms with a 30*0.32 mm filiform needle. With the forearm supinated, the needle was inserted 3 cm distal to the mid-point between the biceps tendon insertion and the medial epicondyle. The needle was advanced in a cranial and medial direction to a depth clinically judged to be in the pronator teres muscle. Safety was assessed by measuring the distance from the needle to the surrounding neurovascular bundles.

RESULTS

Accurate needle penetration of the pronator teres was observed in 100% of the specimens (mean needle penetration: 16.7 ± 4.3 mm, 95%CI 13.6 to 19.7 mm). No neurovascular bundles were pierced in any of the specimen's forearms. The distances from the tip of the needle to the surrounding neurovascular bundles were 16.4 ± 3.9 mm (95%CI 13.6 to 19.2 mm) to the ulnar nerve (A), 9.0 ± 2.2 mm (95%CI 7.3 to 19.5 mm) to the median nerve (B), and 12.8 ± 4.0 mm (95%CI 10.0 to 15.7 mm) to brachial artery (C).

CONCLUSION

The results from this cadaveric study support the assumption that needling of the pronator teres using described anatomical landmarks can be accurately and safely conducted by an experienced clinician.

Prediction Model for Choosing Needle Length to Minimize Risk of Median Nerve Puncture With Dry Needling of the Pronator Teres

OBJECTIVE

The aim of this study was to relate forearm anthropometric measures to ultrasound pronator teres depth to determine the necessary needle length to prevent median nerve (MN) injury during pronator teres dry needling.

METHODS

We conducted a study employing a diagnostic accuracy prediction model (NCT03308279) at a Spanish university center. The study recruited 65 participants to predict the depth of the MN (measured with ultrasound) in the pronator teres using a decision tree algorithm to reduce the risk of MN puncture using 2 needle lengths (13 mm or 25 mm). The decision tree was developed by automatically selecting a cutoff for body mass index, forearm length and circumference, and pronator teres thickness.

RESULTS

For forearm circumferences ≤27.5 cm, the predictive value for the 13-mm needle was 92%. For forearm circumferences >27.5 cm and forearm lengths ≤26.75 cm, the predictive value for the 25-mm needle was 100%.

CONCLUSION

Based upon the findings of this study, we suggest that needle length should be selected according to forearm anthropometric measures to prevent MN injury during pronator teres dry needling.

Sonography of the Pronator Teres: Normal and Pathologic Appearances

The pronator teres muscle is rarely examined during a routine sonographic examination of the elbow joint. Nevertheless, it can be affected by a variety of conditions, including trauma and tumors, and can be implicated in compression of the median nerve. This pictorial essay first illustrates the anatomy and biomechanics of the pronator teres. Then we present the sonographic technique for examination, normal sonographic appearance, and anatomic variations of the pronator teres and adjacent structures as well as sonography of their main disorders. Normal and pathologic sonographic appearances are correlated with magnetic resonance imaging and radiographic results.