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.

Implant-related metal hypersensitivity (MH) after total joint arthroplasty (TJA) is an uncommon and diagnostically challenging complication in which antigen-specific T-cell responses may coexist with nonspecific inflammatory reactions to wear and corrosion products. This narrative review critically summarizes current evidence on the molecular immunopathogenesis, clinical presentation, diagnosis, and management of suspected MH, with particular emphasis on HLA-associated susceptibility and the 2023 European Academy of Allergy and Clinical Immunology (EAACI) mechanistic nomenclature. A structured search of PubMed, Scopus, and Web of Science was used to identify relevant clinical, immunological, and consensus literature. Metal sensitization is substantially more common than clinically relevant implant-associated hypersensitivity, and positive patch or lymphocyte transformation tests do not by themselves establish causality. Current evidence supports selective, clinically contextualized testing after exclusion of infection and mechanical causes; routine preoperative screening in patients without a suggestive history is not recommended. HLA class II associations and metal–peptide–MHC/T-cell receptor interactions provide a plausible molecular basis for interindividual susceptibility, but available genetic data remain insufficient for clinical risk stratification or implant selection. Future studies should integrate standardized phenotyping, quantitative metal exposure, histopathology, and molecular immune profiling before implementing precision arthroplasty.