[Use of a cannulated 3.0 mm AO screw with an intraosseous support washer in osteosynthesis of the scaphoid: results and analysis of problems in 28 cases].

The cannulated 3.0 mm AO/ASIF screw with threaded washer is a new implant for scaphoid osteosynthesis. After insertion into the distal scaphoid pole, the washer serves as an intraosseous support for the head of the cannulated lag screw. From June 1997 to March 1998 the new implant was used in 28 male patients between 14 and 50 years of age. In fourteen patients, acute scaphoid fractures were operated on, including five transscaphoid perilunate fracture dislocations (Herbert type B2 and B4, respectively). Fourteen patients had scaphoid pseudarthroses, among those two re-pseudarthroses after prior surgery elsewhere. Using a palmar approach, the scaphoid was reduced. In pseudarthroses an iliac cortico-cancellous bone block was inserted, and the implants were inserted in a distal-to-proximal manner. In the fourteen acute fractures, follow-up assessment at a mean of 11 months revealed one pseudarthrosis (7%) and four screw removals (29%) for screw back-out after bony consolidation. In the fourteen pseudarthroses, follow-up assessment at a mean of ten months revealed one re-pseudarthrosis (7%) after a technical fault. It was treated by re-operation using the same implant, and healing was now uneventful. One screw removal became necessary after bony consolidation in another patient (7%). In conclusion, our preliminary results suggest that the new implant is suitable for stabilization of scaphoid pseudarthroses after insertion of an iliac crest bone graft. The complication rate in the treatment of acute fractures was inacceptably high.