Evaluation of Various Fixation Methods in Acute Scapholunate Dissociation, A Finite Element Study

Objective: This study aimed to compare the outcomes of fixing scapholunate with pins and screws in parallel,convergent, and divergent orientations.Methods: In this computer simulation study, the CT scan images of a healthy subject wereused to construct a 3D model of the wrist joint using MIMICS software. The imposed force to scaphoid and3D model lunate bones, as well as the scapholunate angle and distance, were compared in different surgicaltechniques using parallel, divergent, and convergent pins and screws.Results: In the absence of external force, the imposed stress applied to the scaphoid and lunate bones in casesof parallel pins and screws were 7.5MPa, 5.08MPa (pins), 1.134MPa, and 1.151MPa (screws), and 10.90MPa,10.90MPa (pins), 9.7MPa, and 34.1MPa (screws) for 50N flexion force. The imposed stress in this approach issignificantly lower compared to other interventions. Better outcomes were seen regarding scapholunate angleand scapholunate distance in using parallel pins or screws as well.Conclusion: In conclusion, implementing parallel pins and screws for scapholunate fixation had better resultsin terms of achieving carpal stability in scapholunate dissociation. However, fixation with pins and screwsshowed a statistically significant difference. Furthermore, a wide range of motion exercises with no additionalforces can be used in the rehabilitation of patients undergoing this surgery.