Radiographic Characteristics of Carpal Instability Associated With Scaphotrapeziotrapezoid Osteoarthritis

Area of Science:

• Orthopedic Surgery
• Radiology
• Hand and Wrist Biomechanics

Background:

• Scaphotrapeziotrapezoid osteoarthritis (STT-OA) is a common condition affecting the wrist.
• The relationship between STT-OA severity and carpal instability, specifically dorsal intercalated segment instability (DISI), requires further investigation.
• Understanding these associations can aid in diagnosing and managing wrist instability.

Purpose of the Study:

• To analyze radiographic carpal indices in wrists with varying grades of STT-OA.
• To investigate the association between STT-OA severity and the occurrence of DISI.
• To identify radiographic characteristics of carpal instability associated with STT-OA.

Main Methods:

• Retrospective analysis of carpal indices in 135 wrists with STT-OA (Crosby's classification grades 2 and 3).
• Measurement of radiolunate (RL), radioscaphoid (RS), scapholunate (SL) angles, lunocapitate (LC) angle, and SL distance.
• Comparison of carpal indices and DISI occurrence between STT-OA grades; evaluation of other joint OA and correlation analysis for DISI wrists.

Main Results:

• Grade 3 STT-OA wrists showed smaller RL and RS angles, and a greater LC angle compared to grade 2.
• DISI was present in 5% of grade 2 and 60% of grade 3 STT-OA wrists.
• No SL angle >70°, widened SL distance, or RS joint OA was observed; DISI wrists showed negative RL-LC and positive RL-RS correlations.

Conclusions:

• An association exists between STT-OA severity and DISI occurrence.
• Carpal instability in STT-OA presents unique features: extended scaphoid, normal SL angle, and absence of RS-OA.
• These findings help characterize carpal instability patterns in STT-OA.