title: The tip-apex distance in the X-Bolt dynamic plating system.
abstract: OBJECTIVE
  The Sliding Hip Screw (SHS) is commonly used to treat trochanteric hip fractures. Fixation failure is a devastating complication requiring complex revision surgery. One mode of fixation failure is lag screw cut-out which is greatest in unstable fracture patterns and when the tip-apex distance of the lag screw is > 25 mm. The X-Bolt Dynamic Hip Plating System (X-Bolt Orthopaedics, Dublin, Ireland) is a new device which aims to reduce this risk of cut-out. However, some surgeons have reported difficulty minimising the tip-apex distance with subsequent concerns that this may lead to an increased risk of cut-out.
  
  
  METHODS
  We measured the tip-apex distance from the intra-operative radiographs of 93 unstable trochanteric hip fractures enrolled in a randomised controlled trial (Warwick Hip Trauma Evaluation, WHiTE One trial). Participants were treated with either the sliding hip screw or the X-Bolt dynamic hip plating system. We also recorded the incidence of cut-out in both groups, at a median follow-up time of 17 months.
  
  
  RESULTS
  There was a significantly increased tip-apex distance with the use of the X-Bolt (mean difference 3.7mm (95% confidence interval 1.58 to 5.73); SHS mean 17.1 mm, X-Bolt mean 20.8; p = 0.001. However, this was not associated with an increased incidence of cut-out at a median follow-up time of 17 months, with three cut-outs (6%) in the SHS group and 0 (0%) in the X-Bolt group.
  
  
  CONCLUSIONS
  The X-Bolt is a safe implant with no increased risk for cut-out. Concerns about minimising the tip-apex distance may be justified but do not appear to be clinically important.Cite this article:M. A. Fernandez, A. Aquilina, J. Achten, N. Parsons, M. L. Costa, X. L. Griffin. The tip-apex distance in the X-Bolt dynamic plating system.Bone Joint Res2017;6:-207. DOI: 10.1302/2046-3758.64.BJR-2015-0016.R2.
authors.affiliation: University of Oxford, NDORMS, John Radcliffe Hospital, Oxford OX3 9DU and Specialty Registrar, Trauma and Orthopaedic Surgery, University Hospital Coventry, Clifford Bridge Road, Coventry, CV2 2DX, UK miguel.fernandez@ndorms.ox.ac.uk.
authors.forename: M A
authors.initials: MA
authors.lastname: Fernandez
authors.affiliation: University of Oxford, NDORMS, John Radcliffe Hospital, Oxford OX3 9DU, UK.
authors.forename: A
authors.initials: A
authors.lastname: Aquilina
authors.affiliation: University of Oxford, NDORMS, John Radcliffe Hospital, Oxford OX3 9DU, UK.
authors.forename: J
authors.initials: J
authors.lastname: Achten
authors.affiliation: Statistics and Epidemiology Unit, Warwick Medical School, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK.
authors.forename: N
authors.initials: N
authors.lastname: Parsons
authors.affiliation: University of Oxford, NDORMS, John Radcliffe Hospital, Oxford OX3 9DU, UK.
authors.forename: M L
authors.initials: ML
authors.lastname: Costa
authors.affiliation: University of Oxford, NDORMS, John Radcliffe Hospital, Oxford OX3 9DU, UK.
authors.forename: X L
authors.initials: XL
authors.lastname: Griffin
keywords: Hip fracture; Tip-apex distance; X-Bolt