Understanding the complex progression of carpal injuries is essential for effective scapholunate instability diagnosis. A recent biomechanical study by Rodriguez GLG et al. investigated how specific ligaments contribute to carpal alignment. Specifically, the researchers focused on the dorsal scaphotriquetral ligament (DSTL) and its impact on the scapholunate (SL) joint.

Initially, the researchers performed sequential sectioning on twenty-four cadaveric wrists to observe progressive instability. They found that isolated tears of the palmar and proximal scapholunate interosseous ligament (SLIOL) caused no major changes. However, once the team sectioned the dorsal SLIOL, the specimens exhibited dynamic instability under axial loading. This means that while resting radiographs remained normal, the SL gap increased significantly during active stress.

Advancing Scapholunate Instability Diagnosis with DSTL Assessment

Furthermore, the study revealed that the superficial dorsal intercarpal ligament (DICL) played a minimal role in stability compared to the DSTL. When the researchers finally cut the DSTL, the carpal bones progressed to static instability. This stage included a permanent dorsal intercalated segment instability (DISI) deformity and marked diastasis. Consequently, surgeons must recognize the DSTL as a vital dorsal restraint that prevents permanent carpal collapse.

Moreover, the authors introduced a new CT-derived measure called the dorsal instability scaphoid angle (DISA). This tool tracks dorsal scaphoid subluxation more accurately than traditional radiographic methods. Therefore, clinicians can use DISA to improve the precision of scapholunate instability diagnosis, although the measure requires further clinical validation.

What is the difference between dynamic and static scapholunate instability?

Dynamic instability only appears when the wrist is under load or in motion, whereas static instability is visible on resting radiographs and indicates a more severe ligamentous injury.

How does the DSTL influence scapholunate instability diagnosis?

The DSTL acts as a primary secondary stabilizer. Its rupture marks the transition from dynamic instability to static collapse, making it a critical structure to evaluate during scapholunate instability diagnosis.

Disclaimer: This content is for informational and educational purposes only... Refer to the latest local and national guidelines for clinical practice.

References

Rodriguez GLG et al. The role of the dorsal scaphotriquetral ligament: a biomechanical study. J Hand Surg Eur Vol. 2026 Mar 21. doi: 10.1177/17531934261432885. PMID: 41863232.

Mitsuyasu H, Patterson RM, Shah MA, et al. The role of the dorsal intercarpal ligament in dynamic and static scapholunate instability. J Hand Surg Am. 2004;29(2):279-288.

Elsaidi GA, Ruch DS, Kuzma GR, Smith BP. Dorsal wrist ligament insertions stabilize the scapholunate interval: cadaver study. Clin Orthop Relat Res. 2004;(425):152-157.