REINFORCEMENT OF LAG SCREW FIXATION WITH A NEW COMPOSITE BIOMATERIAL (CORTOSS®) FOR PERTROCHANTERIC FRACTURES

Abstract

Purpose: Healing may be problematic after lag screw osteosynthesis of pertrochanteric fractures in osteoporotic bone due to the greater risk of defective fixation. Acrylic cement has been proposed to reinforce the fixation of the lag screw in these patients, principally to avoid the risk of cutout, but the acrylic cement’s thermal toxicity, its poor biocompatibility, and the difficult manipulation are important drawbacks. Cortoss® is a new composite biomaterial composed of bisphenol-aglycidly (bis-GMA) which could be an attractive alternative to classical cements. Cortoss is an injectable material with mechanical properties similar to human cortical bone. The purpose of this clinical study was to describe the new method for injection the material and to assess the anchoring force and safety of Cortoss in osteoporotic patients undergoing surgical fixation of pertrochanteric fractures.

Material and methods: This prospective study was approved by the local ethics committee. Twenty consecutive patients aged 70 years or more with pertro-chanteric fracture were included. The lag screw was inserted under fluoroscopic guidance, and the maximum insertion torque was measured. The screw was then unscrewed seven turns (length of the threaded head), and 2.5 cm Cortoss was injected via a polyimide catheter measuring 2.5 mm in diameter. The screw was then rescrewed in place to a troque 30% above that measured without Cortoss

Results: Eighteen women and two men, age 70 – 96 years, gave their informed consent to participate in the study. Mean maximal insertion torque without Cortoss was 1.23 Nm (min 0, max 4.8 Nm), which was increased 30% with Cortoss. Posto-operative x-rays showed that the screw head was embedded in an envelope of Cortoss and that the Cortoss had diffused into the adjacent bone. There were no adverse effects.

Discussion and conclusion: Cortoss provided effective reinforcement of the fixation as demonstrated by the higher insertion torque. Cortoss can also increase the mechanical resistance of the screw-cancellous bone interface, limit fixation default, and reduce secondary displacement of the lag screw in patients with osteoporotic bone. Improved stability can also reduce immobilisation time and facilitate bone healing without increasing the risk of secondary displacement and subsequent morbidity. Due to its safety, easy use, and efficacy, Cortoss provides a better alternative than acrylic cement for reinforcement of lag screw fixation of porotic bone.