SCREW AUGMENTATION WITH A NEW SYNTHETIC CORTICAL BONE VOID FILLER

Abstract

Screw stripping in osteoporotic bone and bone of otherwise poor quality represents a common problem. Treatment alternatives, such as using a larger diameter screw or a longer plate, may add time, increase morbidity, be impractical, or simply be ineffective. Alternatively, the stripped screw can be augmented with a bone cement. A new injectable synthetic cortical bone void filler (Cor-toSSTM) is based on a resin system, resulting in a very strong, radiopaque, extensively crosslinked, biocompatible composite that does not resorb. We tested the safety and efficacy of the new bone cement in augmenting stripped screws until bone healing.

Of a total of 143 screws implanted in 24 patients with ankle fractures (average age 66. 8 years), 61 became stripped and were augmented. The primary efficacy endpoint was successful intraoperative screw augmentation. The secondary endpoint was whether screw fixation, determined radiologically, remained effective during the 3-month follow-up required for the fracture to heal.

All the stripped screws were successfully augmented. During follow-up at 24 hours, 7 days, and 1 month, none showed any movement relative to either the plate or the bone. At 3 months, one augmented screw in a patient with severe osteoporosis showed gross movement above the plate, which did not affect healing. Serial radiographic analysis did not show the development of any lucencies or cracks in the cement. All fractures healed within 3 months following surgery.

Screw augmentation allowed successful reduction and fixation of the fractures. No adverse events directly attributable to the device were observed. The new bone void filler represents a safe, simple, and reliable method by which to achieve stable internal fixation constructs in patients in whom bone screws fail to gain purchase due to poor bone quality or overtightening.