An Integrated Modelling Approach for the Optimised Design of Patient-specific, Low Profile Clavicle Fracture Fixation Plates
Clavicle fractures are common injuries. They account for 2.6-4 % of all fractures, and their incidence increased in Belgium from 56.5/100,000 persons/year in 2006 to 70.6/100,000 in 2015. While these fractures were typically treated conservatively, the number of surgically treated clavicular fractures has increased by 190 % over the last decade. Fixation plates currently used to surgically stabilise the fracture, are however suboptimal. They need three-dimensional intra operative contouring and detachment of muscle attachment sites to achieve an adequate fit. Furthermore, the reoperation rate after clavicle fracture plate fixation is 20%, with isolated hardware removal -mostly due to plate irritation- accounting for 16 %. In a recent systematic review, reoperation rates up to 53 % are reported. Possible causes of plate irritation are poor geometric fit on the one hand, and soft tissue irritation due to the thickness of the current fixation plates on the other hand. Low profile patient-specific fixation plates could provide an ideal solution. Current incremental forming techniques would theoretically allow the production of low profile fixation plates for clavicle fractures.
The aim of this PhD is to develop a modelling workflow for low profile patient-specific fixation plates that are both geometrically and biomechanically optimised. Therefore, the design of current clavicle fracture fixation plates should be improved by accounting for the clavicle morphology and loading. Identification of the morphology allows to design plates that optimally fit the geometry of the clavicle and respect its muscle attachment sites. The loading to which the clavicle is exposed in everyday activities should be accounted for to determine the minimal thickness of the fixation plates, while safeguarding their stiffness.
To achieve this aim, finite element analysis was combined with statistical shape models to optimise the plate geometry, and boundary conditions were defined based on loading profiles calculated using musculoskeletal modelling. The performance of the optimal design was then compared to a commercial fixation plate in terms of geometrical fit, anatomical outline, strength, and fracture stability. The patient-specific plate performed better in each of these aspects when compared to the commercial plate.
The developed workflow allows to model fracture fixation plates with patient-specific geometry and low profile, accounting for load cases during activities of daily living. The use of these patient-specific fixation plates is expected to decrease operation time, as intra operative contouring will become irrelevant, and decrease reoperation rates caused by implant irritation.