18 research outputs found

    An approximate model for cancellous bone screw fixation

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    This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2013 Taylor & Francis.This paper presents a finite element (FE) model to identify parameters that affect the performance of an improved cancellous bone screw fixation technique, and hence potentially improve fracture treatment. In cancellous bone of low apparent density, it can be difficult to achieve adequate screw fixation and hence provide stable fracture fixation that enables bone healing. Data from predictive FE models indicate that cements can have a significant potential to improve screw holding power in cancellous bone. These FE models are used to demonstrate the key parameters that determine pull-out strength in a variety of screw, bone and cement set-ups, and to compare the effectiveness of different configurations. The paper concludes that significant advantages, up to an order of magnitude, in screw pull-out strength in cancellous bone might be gained by the appropriate use of a currently approved calcium phosphate cement

    Pedicle Screw Surgery in the UK and Ireland: A Questionnaire Study

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    Pedicle screw (PS) malpositioning rates are high in spine surgery. This has resulted in the use of computed navigational aids to reduce the rate of malposition; but these are often expensive and limited in availability. A simple mechanical device to aid PS insertion might overcome some of these disadvantages. The purpose of this study was to determine the demand and design criteria for a simple device to aid PS placement, as well as to collect opinions and experiences on PS surgery in the UK and Ireland. A postal questionnaire was sent to 422 spinal surgeons in the UK and Ireland. 101 questionnaires were received; 67 of these (16% of total sent) contained useful information. 78% of surgeons experienced problems with PS placement. The need for a simple mechanical device to aid PS placement was expressed by 59% of respondent surgeons. The proportion of respondents that inserted PSs in the cervical spine was 14%; PSs are mainly inserted in the thoracic, lumbar and sacral spine, but potential exists for a PS placement aid for the cervical and thoracic spine. From the experiences of these 67 surgeons, there is evidence to suggest that surgeons would prefer a pedicle aid that is multiple use, one-piece, hand-held, radiolucent, unilateral and uses the line of sight principle in traditional open surgery. Based on the experiences of 67 surgeons, there is evidence to suggest that computed navigational aids are not readily used in PS surgery and that a simple mechanical device could be a better option. This paper provides useful data for improving the outcomes of spinal surgery
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