Technical Notes and Tips: The World's Longest Instrument – An Aid to Acetabular Cup Extraction in Revision Hip Surgery

Component removal is a time-consuming, yet necessary, step during revision hip surgeries. Because of the diversity of the components and the methods used to secure them, an equal diversity of approaches and tools are necessary for component removal. Many instruments are described for removing the acetabular component of a total hip replacement. Cement-component debonding is an important step in acetabular component removal. Revision instruments,1 chisels, ultrasound tools and commercially available purpose built devices, such as the ‘Explant’ acetabular cup removal system (Implex/Zimmer Inc.), achieve this to a greater or lesser degree. We report a modification of a technique that the senior author was instructed in at the Nuffield Orthopaedic Centre in Oxford, UK. Direct disimpaction of the cup is desirable to avoid leverage forces acting on, and potentially damaging, the acetabular bone stock when removing the cup. A cork-screw slap hammer device is ideal for this. Whilst these are available as combined or one-piece instruments, we describe a technique using instruments which should be readily available in any revision theatre, namely a corkscrew, a slap hammer and a universal femoral component extractor, assembled together in series as shown in Figure 1. The connection between the two extraction components (the corkscrew and the slap hammer) is rigid, rather than a loop of steel wire as was used in the original assembly used in Oxford (where this device was colloquially known in theatre as ‘the world's longest instrument’). The more solid arrangement described here is superior to its predecessor in several respects: our device employs a better coupling mechanism (the universal femoral extractor) which is less likely to break during use, directly imparts the disimpacting force (achieved by upwards blows of the slap hammer to the cork-screw engaged in the cup) allowing greater control in cup removal and, unlike single-purpose commercially available devices, has a versatility which allows it be used for a number of different potential purposes. Figure 1 Cork-screw, slap hammer and a universal femoral component extractor assembled together in series.