Design and assessment of a surgical instrument for passing the Gigli saw during pelvic osteotomies

The goal of this master thesis is to design, manufacture and test a new orthopaedic surgical instrument which will be used during pelvic osteotomies. The concerned osteotomy is the Salter osteotomy which consists of a reorientation of the pelvis thanks to a bone cutting. The bone cutting is performed along the innominate line. This surgery increases the covering of the femoral head and in this way decreases the risks of hip dislocation and degenerative diseases such as osteoarthritis. The patients are most of the time children aged between 18 months and six years with acetubular dysplasia. The acetabulum is the part of the pelvis in which the femoral head is positioned. The thesis begins with a clinical context in which the acetabular dysplasia is described with its different treatments. The challenges of these treatments are presented. The main challenge of the Salter osteotomy is the passage of the Gigli saw through the greater sciatic notch; that means the passage of the saw around the bone of the pelvis which has to be sawed. When the iliac fossa is well cleared and the Rang retractors are correctly placed, the passage of the guidewire can take only a few minutes. However when the iliac fossa is not cleared enough, or the Rang retractors are not correctly placed or if the dysplasia is acute, the passage of the Gigli saw through the greater sciatic notch can take up to thirty minutes. In this case, the child is under longer anaesthesia which is not good for his health. The request of the surgeon is thus clear: designing and testing a surgical instrument which assists the surgeon to pass the Gigli saw through the greater sciatic notch during Salter osteotomy. Following the clarification of this request, a first functional analysis and the list of specification are realized. After that, based on the list of specifications, a second functional analysis specific to the instrument is established. Afterwards, the concept variants responding to the list of specifications are designed following a classical design method. The retained solutions are prototyped. The last step is a feasibility test of the retained solutions. A first test was performed on an experimental setup which reproduces the surgical cavity with the pelvis and the Rang retractors. A second test was executed on a cadaver in the laboratory of anatomy from UCL. An additional test consisting of an analysis of the resistance of magnet to a steam sterilization process was performed. Following these tests, the feasibility of the final solution, consisting of a set of magnetic instruments, was approved. Research can therefore continue !