Carpal Motion in Chronic Geissler IV Scapholunate Interosseous Ligament Wrists

This study evaluated the biomechanics of Geissler IV (G4) wrists in cadavers and compared them with intact specimens after multiple ligament sectioning to create scapholunate instability. It also evaluated carpal motion changes after sectioning of the lunotriquetral interosseous ligament (LTIL). Eight cadaver wrists determined to be G4 arthroscopically were tested using a wrist joint motion simulator. The LTIL was then sectioned, and carpal motion was recorded again. Carpal motions were compared with 37 normal wrists after sectioning of the scapholunate interosseous ligament and other ligaments to create a G4 wrist. Carpal motion of the 37 normal wrists after ligamentous sectioning was similar to motion of the 8 specimens noted to be G4. These wrists did not demonstrate subluxation of the scaphoid that may occur after ligament sectioning. After sectioning of the LTIL, there were significant changes in lunate and triquetral motion. These findings support the hypothesis that sectioning multiple ligaments in normal wrists to create scapholunate instability causes average motion comparable to that seen in G4 wrists. Ligamentous sectioning can cause a range of scaphoid instability. Lunotriquetral interosseous ligament sectioning in native G4 wrists caused greater changes in triquetral than scaphoid range of motion. Patients with arthroscopically determined G4 lesions have an incompetent SLIL and scapholunate instability but do not necessarily have scapholunate dissociation and subluxation. Cadaver studies that evaluate instability by sectioning specific intact wrist ligaments are similar to the G4 specimens and thus are a good approximation of naturally occurring wrist instability. The functionality of secondary stabilizers not seen arthroscopically may explain the differences in motion. Geissler IV wrists and ligament-sectioned wrists are points on the spectrum of carpal instability, which is determined by the extent of damage to multiple ligamentous structures.