Preoperative estimation of tibial nail length—Because size does matter

Abstract

IntroductionSelecting the correct tibial nail length is essential for satisfactory outcomes. Nails that are inserted and are found to be of inappropriate length should be removed. Accurate preoperative nail estimation has the potential to reduce intra-operative errors, operative time and radiation exposure. MethodsWe compared the most commonly used radiological, anthropometric and intra-operative techniques to determine ideal nail lengths for 16 paired cadaveric tibiae. Five different anthropometric measurements were taken from each intact cadaver including: knee joint line to ankle joint line distance (JJD), medial knee joint line to medial malleolus distance (MMD), tibial tuberosity to medial malleolus distance (TMD), olecranon to 5th metacarpal head distance (OMD) and body height (BHR). Each tibia also underwent antero–posterior (AP) and lateral scanograms. Computerised tomography was used to determine the ideal nail length for each tibia. Each anthropometric and radiological measurement was recorded by two orthopaedic surgeons independently. An expert tibial nail was then inserted after nail length estimation was performed using a guidewire technique and an intra-operative radiographic ruler. ResultsThe AP scanogram was found to be 100% accurate in selecting ideal nail length. The lateral scanogram was also found to be reasonably accurate but in 19% (3/16) of cases it led to a nail being too long. The intra-operative radiographic ruler was found to give a good indication of the ideal nail size, as did the guidewire technique, with only 6% (1/16) of cases producing an incorrect nail size. In general, the anatomical measurements gave a poor indication of ideal nail size compared with the other techniques. The following accuracies were noted: JJD 56%, MMD 50%, TMD 38%, BHR 13% and OMD 56%. ConclusionsWe found that radiological methods such as using an AP radiograph with known magnification and intra-operative radiographic ruler were able to predict nail length very accurately and we suggest that these measurements should be performed routinely. The guidewire technique was also effective but we recommend that it not be used in isolation as errors can occur. We found that anatomical measurements are not accurate for predicting tibial nail length.