Measuring tip-apex distance using a picture archiving and communication system (PACS)

Background: The sliding hip screw is currently the most frequently used prosthesis used to fix trochanteric fractures of the hip. The tip-apex distance' (TAD) has been found to be predictive of hardware failure, with a larger TAD being associated with an increasing risk of cut-out. Previous studies have either used hard-copy radiographs and geometrical aids or a mixture of scanned hard-copy images and extra software to measure TAD. The current study describes a new method of tip-apex distance estimation using an entirely digital picture archiving and communication system (PACS). Materials and methods: Ten radiographs were measured for TAD by four surgeons of differing experience using the described measurement protocol, at two different time points (4 weeks apart). The results were then subjected to two-tailed t-tests to determine if they differed significantly. Results: No tests attained significance (i.e. no statistical difference existed between the observers' measurements and no difference existed over time from a single observer's results). Conclusion: This study shows that TAD can be easily, accurately and, importantly, reproducibly measured using an entirely digitally based image capture and archiving system. The ease with which the measurements and calculations can be made will facilitate orthopaedic practitioners and trauma units in their auditing activities, and allows for quick TAD estimation in the 'X-ray meeting' environment. (K) 2007 Elsevier Ltd. All rights reserved.