Ken Sneddon

Screw and washer fixation for onlay rib grafts to the mandible

fractured edentulous mandible can be a challenging injury o treat, particularly so in a patient with a severely atrophic andible the vertical height of which is less than 10 mm.1 ne technique for fixation of such a fracture that was previusly described from our unit is the use of autologous rib as nlay fixation grafts.2 We have found that this is a reliable ay of achieving bony union in a severely atrophic mandible. One of the difficulties with the technique is how to secure he rib. Newman has described the use of circummandibular ires to secure the rib in place.2 This can be effective, but he fixation is often not rigid and the fragments can move uring the postoperative period. To improve the rigidity we ave tried using screws from our 2.0 miniplate fixation set. hese screws pass through the buccal rib graft, both cortices f the mandible, and then the lingual rib graft. The rib graft s soft bone compared with the mandible. The screws effecively slide through the outer graft and compress the graft on he buccal aspect of the mandible. Unfortunately the conical hape of the head of a 2.0 screw is designed to fit in a counersunk hole in a miniplate. When used to secure rib grafts he conical head acts as a wedge, and causes the soft bone of he rib to split as the screw is tightened. The solution is to use a washer, which spreads the load of he screw as it is tightened, and prevents the onlayed rib from plitting. The use of biconcave washers has recently been escribed in the fixation of mandibular fractures with lag crews.3 Biconcave washers will work well; however, they ere not available when we treated the patient described. he photographs show single holes cut from a 2.0 miniplate hat were used as substitute washers. This is an alternative