# The Pronator Teres Muscle Revisited: Morphological Classification, Neurovascular Entrapment, and Surgical Implications

## TL;DR

This paper reviews the different types of the pronator teres muscle and their role in median nerve entrapment, offering insights for diagnosis and treatment.

## Contribution

The paper introduces a morphology-based classification of the pronator teres muscle integrating anatomy, imaging, and surgical relevance.

## Key findings

- Three morphological types of the pronator teres were identified, each with distinct entrapment mechanisms.
- Dynamic ultrasound and MR neurography improve diagnostic accuracy for median nerve entrapment.
- Published management approaches vary by type, with inconsistent outcomes reported.

## Abstract

Background: The pronator teres (PT) muscle, although traditionally described as a constant two-headed forearm flexor, demonstrates considerable morphological variability. These variants play a crucial role in the pathogenesis of pronator syndrome, a rare but clinically significant entrapment of the median nerve in the proximal forearm. Despite growing interest, there is no widely adopted classification integrating anatomy, imaging, and surgical relevance. This review summarises and contextualises current classifications of the pronator teres in relation to median nerve entrapment, with emphasis on their anatomical, imaging, and surgical relevance. Methods: We performed a narrative review of the literature using PubMed, Scopus, and Web of Science (1960–2025). Studies were included if they reported cadaveric findings, imaging features, or clinical management of PT-related median nerve entrapment. Representative anatomical and clinical sources were analysed to synthesise a morphology-based framework. Results: We identified three morphological types of the PT: Type I (median nerve between humeral and ulnar heads, 74%), Type II (beneath both heads, 12%), and Type III (beneath the humeral head only, 14%). Each type demonstrates distinct entrapment mechanisms and imaging features. Dynamic ultrasound and advanced MRI sequences, particularly MR neurography, have been reported to improve diagnostic confidence but remain underutilised. Published reports describe differing management approaches by type, with variable outcomes. Tables and summary boxes compile previously published findings on entrapment potential, imaging pitfalls, and surgical approaches by type. Conclusions: This review summarises existing classifications linking PT variability to median nerve entrapment. Such integration may have potential clinical relevance but requires further empirical validation. Future studies should standardise imaging protocols, validate electrodiagnostic correlations, and explore functional classifications incorporating clinical, radiological, and anatomical data.