Techniques to increase pedicle screw stability in osteoporotic vertebrae

Abstract

Objective: Operative stabilisation of osteoporotic vertebral fractures. Indications: Fractures of the thoracic and lumbar spine. Contraindications: None. Surgical technique: Preoperative determination of expected bone mineral density. Implantation of pedicle screws in special trajectories, cement augmentation of the screws and use of alternative implants. Postoperative management: Early functional mobilisation and initiation of osteoporosis therapy if indicated. Results: A biomechanical cadaver study with human vertebral bodies was performed. There was a highly significant correlation between bone mineral density and the fatigue load (r2 = 0.839, p < 0.001). Specimens with bone mineral density below 80 mg/cm3 only reached 60% of the fatigue load compared to the specimens with adequate bone quality (>120 mg/cm3) and therefore stability mightbe insufficient and an additional stabilisation should be considered. In osteoporotic vertebrae, the fatigue strength of cement augmented screws was increased by 52% compared to the non-augmented screws (fatigue load non-augmented: 173 N, augmented: 263 N; p = 0.001). Studies conducted by other research groups have demonstrated the effect of various screw trajectories and alternative implants to improve stability in the treatment of osteoporotic vertebral body fractures.