Revision hip arthroplasty requires a comprehensive appreciation of abnormal bony anatomy. Advances in radiology and manufacturing technology have made three-dimensional representation of actual osseous anatomy obtainable. These models provide a visual and tactile reproduction of the bony abnormality in question.

Life size three dimensional models were manufactured from CT scans of two patients. The first had multiple previous hip arthroplasties and bilateral hip infections. There was a pelvic discontinuity on the right and a severe postero-superior deficiency on the left. The second patient had a first stage revision for infection and recurrent dislocations. Specific metal reduction protocols were used to reduce artefact. The dicom images were imported into Mimics, medical imaging processing software. The models were manufactured using the rapid prototyping process, Selective Laser Sintering (SLS).

The models allowed accurate templating using the actual prosthesis templates prior to surgery. Acetabular cup size, augment and buttress sizes, as well as cage dimensions were selected, adjusted and re-sterilised in advance. This reduced operative time, blood loss and improved surgical decision making. Screw trajectory simulation was also carried out on the models, thus reducing the chance of neurovascular injury.

With 3D printing technology, complex pelvic deformities can be better evaluated and can be treated with improved precision. The life size models allow accurate surgical simulation, thus improving anatomical appreciation and pre-operative planning. The accuracy and cost-effectiveness of the technique were impressive and its use should prove invaluable as a tool to aid clinical practice.

Axial loading of the foot/ankle complex is an important injury mechanism in vehicular trauma, responsible for severe injuries such as calcaneus, talus and tibial pilon fractures. Axial loading may be applied to the leg externally, by the toepan and/or pedals, as well as internally by active muscle tension applied through the Achilles tendon during pre-impact bracing. In order to evaluate the effect of active muscle tension on the injury-tolerance of the foot/ankle complex, axial impact tests were performed on isolated lower legs, with and without experimentally stimulated muscle tension applied through the Achilles’ tendon. Acoustic emission was used to determine the exact time of fracture during the tests. The primary fracture mode was calcaneal fracture in both groups, but tibial pilon fractures occurred more frequently with the addition of Achilles tension. A linear regression model was developed that describes the expected axial loading injury tolerance of the foot/ankle complex in terms of specimen age, gender, mass and level of Achilles tension.