[Positions of Sustentacular Screw in Osteosynthesis of Calcaneal Fractures: Clinical and Radiographic Study]

PURPOSE OF THE STUDY The aim of the study was to analyse the options for sustentacular screw placement in osteosynthesis of intra-articular fractures of the heel bone and to assess the effect of various screw positions on failure to maintain the reduction in the postoperative period. In addition, problems related to screw-end protrusion over the medial cortical bone or to screw penetration into the talocalcaneal joint were assessed. MATERIAL AND METHODS The group comprised 23 patients with a total of 25 intra-articular fractures of the heel bone treated by surgery. The procedure involved insertion of a sustentacular screw under fluoroscopic guidance. Post-operatively, screw position in the sustentacular fragment was evaluated on CT scans. During follow-up, attention was focused on the effect of screw placement on maintenance of fracture reduction, and clinical symptoms potentially associated with screw malposition were recorded. RESULTS All sustentacular screws were fixed sustentacular fragments. Seven screws (28%) were inserted in the talar shelf, seven (28%) were placed under and nine (36%) over the sustentaculum tali. Two screws penetrated into the talocalcaneal joint (8%). The end of a screw projecting by 2 mm over the medial wall of the calcaneus was found in 11 cases (44%). Two patients with screws penetrating into the talocalcaneal joint had problems. On the other hand, no clinical effect of a screw extending over the medial wall of the calcaneus was recorded. No significant association of screw position with late //delayed failure of fracture reduction was detected. DISCUSSION Although the ideal trajectory for a sustentacular screw have been defined using a model of the calcaneus, it is not easy to achieve optimal screw placement due to the complex anatomy of the calcaneus and limited possibilities of intra-operative control of screw insertion. Any sustentacular screw malposition is a potential risk factor, particularly if the screw has penetrated into the talocalcaneal joint. Therefore, it will be useful to seek methods allowing for safer screw insertion and elimination of risks associated with screw misplacement. The technique of sustentacular screw insertion by means of a compression-based device, described by the authors, designated to allow for screw placement in distal humerus fractures is one of the options. CONCLUSIONS Optimisation of techniques for sustentacular screw insertion in the osteosynthesis of calcaneal fractures should contribute to reduction of risks related to screw malposition. The assessment of effects which the position of a screw may have on delayed failure of fracture reduction should be based on a thorough biomechanical study.

sustentacular screw, calcaneal fracture, insertion, malposition.