From the Guidelines
To diagnose between flexor carpi ulnaris (FCU) injury and triangular fibrocartilage complex (TFCC) injury, a combination of clinical examination and imaging, with an emphasis on MRI and MR arthrography, is necessary. Start with a focused physical examination: FCU injuries typically present with pain along the medial forearm and wrist, tenderness over the FCU tendon, and pain with resisted wrist flexion and ulnar deviation. TFCC injuries usually cause pain on the ulnar side of the wrist, particularly with rotation, clicking or popping sensations, and pain with axial loading of the ulnar wrist. The ulnar fovea sign (pain with deep palpation between the ulnar styloid and flexor carpi ulnaris tendon) is highly specific for TFCC injuries.
For imaging, ultrasound can visualize FCU tendon abnormalities like thickening or tears, while MRI is highly accurate for lesions involving the radial (central) zone of the disc, especially with the use of high-resolution fast spin-echo or 3-D gradient-recalled pulse sequences 1. However, MR arthrography is the most sensitive and specific imaging modality for detecting TFCC injuries, with a sensitivity ranging from 63% to 100% and specificity ranging from 89% to 97% 1. Wrist arthroscopy may be needed for definitive diagnosis of TFCC injuries in unclear cases. These conditions often coexist, as both affect the ulnar side of the wrist, so a comprehensive evaluation is important for accurate diagnosis and appropriate treatment planning.
Key points to consider in the diagnosis include:
- Clinical presentation: FCU injuries present with medial forearm and wrist pain, while TFCC injuries cause ulnar-sided wrist pain.
- Imaging modalities: Ultrasound for FCU, MRI for TFCC, and MR arthrography for improved sensitivity and specificity in TFCC injuries.
- Specific signs: Ulnar fovea sign for TFCC injuries.
- The importance of a comprehensive evaluation due to the potential coexistence of these conditions.
From the Research
Diagnosing Flexor Carpi Ulnaris vs TFCC
To diagnose flexor carpi ulnaris vs TFCC, several factors and diagnostic markers should be considered:
- The clinical picture of ulnar-sided wrist pain can be confusing due to various coexistent pathologies 2
- MRI findings can help identify potential causes of ulnar-sided wrist pain, including TFCC tears, distal radioulnar joint arthritis, and extensor carpi ulnaris pathology 2, 3
- The presence of extensor carpi ulnaris tendon pathology and ulnar styloid bone marrow edema can be used as diagnostic markers for peripheral TFCC tears on wrist MRI 3
Diagnostic Markers
Some key diagnostic markers for TFCC tears include:
- ECU pathology (tenosynovitis, tendinosis, tear, or subluxation) 3
- Ulnar styloid process bone marrow edema 3
- Distal radioulnar joint arthritis 2
- Ulnocarpal abutment and degenerative tears 2
Surgical Approach
A surgical approach to the triangular fibrocartilage complex can provide wide exposure of the dorsoulnar aspect of the wrist, allowing for various procedures to be performed through a single approach 4
- This approach preserves the extensor carpi ulnaris and its sheath, and allows for minimal postoperative immobilization and early rehabilitation 4
Effect of TFCC Injury on Extensor Carpi Ulnaris
TFCC injury can affect extensor carpi ulnaris function and friction:
- Injury to the TFCC can increase the moment arm of the extensor carpi ulnaris, reducing its force-producing capacity but increasing its mechanical advantage 5
- Tendon friction during flexion-extension may be decreased following TFCC injury, while friction during radial-ulnar deviation remains unchanged 5