A-0086Treatment of scaphoid non-union in the middle third (Herbert D2) with conventional bone grafting and screw fixation: an analysis of clinical and radiological results

Abstract

Introduction: Internal fixation for undisplaced scaphoid fractures is becoming increasingly popular, especially in a young and active population. Although in a clinical setting it can be difficult, central placement is important for successful percutaneous screw fixation. It decreases time to fracture union and is biomechanically stronger. In this study we investigated the different possibilities to obtain a more central screw placement through a volar approach. Methods: We performed measurements on 20 CT scans of unfractured scaphoids. In the first part of the study, a central virtual guidewire was drawn in the sagittal and coronal plane in ten scaphoids to delineate the optimal placement of a screw for scaphoid fixation. The same procedure was repeated with the wrist in extension and ulnar deviation to look for dynamic variations. Secondly, in ten scaphoids a comparison was made between the central virtual guidewire, one that represents a transtrapezial approach and one for a standard volar approach. Results: The central virtual guidewire always transected the trapezium with either a neutral position of the wrist or extension and ulnar deviation. The average clearances in the frontal plane were 2.347 and 2.416 mm (P ¼ 0.7216), in the sagittal plane 4.697 and 4.029 mm (Po0.0001), respectively. Comparing a centrally placed guidewire to the transtrapezial approach, no statistical difference could be found. The transtrapezial approach was statistically better (Po0.001) for central screw placement than the standard volar approach in the distal and midwaist plane. Discussion: The ideal position for a screw in scaphoid fixation is centrally. This CT study shows that central placement of a screw in the scaphoid, using a volar approach, can be done by placing the guidewire through the trapezium. Alternatively, part of the trapezium needs to be resected or the scaphotrapezial joint needs to be opened and manipulated to allow exact central placement in the scaphoid.