Modified Carpal Stretch Test as a Screening Test for Detection of Scapholunate Interosseous Ligament Injuries Associated with Distal Radial Fractures

Abstract

Intra-articular distal radial fractures are frequently accompanied by a scapholunate interosseous ligament injury, which may adversely affect the outcomes. Arthroscopy may not be appropriate as a first-line evaluation method to diagnose these injuries because of time, expense, and availability issues. The purpose of this study was to evaluate the effectiveness of the modified carpal stretch test for screening for scapholunate interosseous ligament injuries in patients with an intra-articular distal radial fracture. The carpal stretch test is a radiographic evaluation in which disruption of the smooth arc of the proximal carpal row joint line indicates a lack of integrity of the scapholunate interosseous ligament. We modified the original carpal stretch test and prospectively performed the modified test on forty-eight patients with a total of forty-nine unstable intra-articular distal radial fractures. With the patient under anesthesia, the injured wrist was evaluated with the modified carpal stretch test with fluoroscopy. The wrist was then examined arthroscopically to classify the scapholunate interosseous ligament injury. Three observers independently determined whether there was disruption of the proximal carpal row joint line (Gilula's arc II), used as an indicator of a grade-III or IV scapholunate interosseous ligament tear, on fluoroscopic images. The fluoroscopic results were compared with the arthroscopic findings. The average sensitivity of the modified carpal stretch test was 78%, the average specificity was 72%, the average positive predictive value was 60%, the average negative predictive value was 87%, and the average accuracy was 74%. The intraclass correlation coefficient (ICC) for interobserver agreement was 0.73, and the ICCs for intraobserver agreement were 0.86, 0.68, and 0.84 for the three observers. The modified carpal stretch test was useful to rule out grade-III or IV scapholunate interosseous ligament tears associated with intra-articular distal radial fractures, but it was not as useful to confirm the presence of a tear. This test may reduce the necessity for arthroscopic assessment to identify scapholunate interosseous ligament injuries following distal radial fractures and may improve the rates of detection of important carpal ligament injuries accompanying intra-articular distal radial fractures.