Beyond Palmer: a topographic classification of non-Palmer triangular fibrocartilage complex injuries.

Triangular fibrocartilage complex (TFCC) injuries are a common cause of ulnar-sided wrist pain. The Palmer classification remains the standard framework, but high-resolution MRI and wrist arthroscopy have revealed injury patterns not included in the original scheme. These include refinements of foveal avulsions (Palmer type 1B) and radial-sided tears (type 1D), as well as broader anatomical and functional concepts of TFCC organization. In this educational review, we present a topographic classification of non-Palmer TFCC injuries into three groups: central lesions, capsular tears, and complex or combined injuries. Each group has different therapeutic implications. We review the relevant pathomechanics, clinical presentation, and imaging findings, with emphasis on MRI and MR or CT arthrography, and correlate them with arthroscopic and surgical findings to guide treatment planning. KEY POINTS: Question: although the Palmer classification remains the standard framework for TFCC injuries, MRI and arthroscopy frequently demonstrate clinically relevant lesion patterns beyond its original categories. Findings: non-Palmer TFCC injuries fall into three topographic categories: central, capsular, and complex or combined lesions, each with characteristic MRI features and treatment implications. Critical relevance statement: topographic classification of non-Palmer TFCC injuries supports more accurate preoperative MRI interpretation and surgical planning in patients with ulnar-sided wrist pain.