Broken Pedicle Research Articles

Predicting pullout strength of pedicle screws in broken bones from X-ray images

Pedicle screw fixation is one of the most common procedures used in spinal fusion surgery. The screw loosening is a major concern, which may be caused by broken pedicles. In vitro pullout tests or insertion torque are the main approaches for assessing the stability of the screw; however, direct evidence was lacking for clinical human spines. Here, we aim to provide a model that can predict the pullout strengths of pedicle screws in various pedicle conditions from X-ray images. A weighted embedded bone volume (EBV) model is proposed for pullout strengths prediction by considering the bone heterogeneity and confinement of the screw. We showed that the pullout strength is proportional to the EBV for homogeneous bone and the weighted EBV for layered composite bone. The proposed weighted EBV model is validated with in vitro Sawbones® pullout experiments. The results show that the model has better accuracy than the simple EBV model, with a coefficient of determination of 0.94. The proposed weighted EBV model can help assess the stability of a pedicle screw in a broken pedicle by simply examining 2D X-ray images.

Broken lumbar pedicle screw – a short report

Abstract Spinal fixation is one of the common surgical procedure performed by spine surgeons. Among the various spinal fixation technique, pedicle screw fixation is of paramount importance especially when instability is in dorsolumbar and sacral region of spine. Like any surgical procedure, pedicle screw fixation is not devoid of complications. Broken pedicle screws are one of the rare complication of this procedure with a great challenge to deal with such situation. We are reporting one of the rare complication of pedicle screw fixation with literature review and our philosophy to deal such complication.

Effect of Insertion Status of a Pedicular Screw on its Mechanical Properties using the Finite Element Method

Purpose : The structural performance of a fixation system was investigated in the case of screw insertion into the pedicular canal with or without its threads fastened in the cortex and in the broken pedicle. Materials and Methods : The symmetric geometric model was used for the pull-out test, and the simplified 3-dimensional model at 3 level, namely, the 3rd, 4th and 5th lumbar vertebrae, was used for the axial compressive loading test. Results : According to the result of the axial-loading test, bending moments and Von-Mises stresses were increased at the junction between the head and the 2nd and 3rd pitches of the lumbar pedicle screw and at the center of 4th lumbar vertebral body, in the models of intact, posterior elements removed and unstable fractured spines. As the results of flexibility, there is no difference in intra-cortical insertion compared to intra-medullary pedicle insertion in the intact spine model. However, flexibility of the laminectomy model was 8% better that of the intra-cortical insertion, and the unstable fracture model 2% better. Conclusion : There is no difference in the flexibility of intra-cortical and intra-medullary pedicle screw insertion. The stability of the posterior structure is more important than anterior pedicle screw fixation.