Shape-matching-based fracture reduction aid concept exemplified on the proximal humerus-a pilot study

Optimizing fracture reduction quality is key to achieve successful osteosynthesis, especially for epimetaphyseal regions such as the proximal humerus (PH), but can be challenging, partly due to the lack of a clear endpoint. We aimed to develop the prototype for a novel intraoperative C-arm-based aid to facilitate true anatomical reduction of fractures of the PH.

The proposed method designates the reduced endpoint position of fragments by superimposing the outer boundary of the premorbid bone shape on intraoperative C-arm images, taking the mirrored intact contralateral PH from the preoperative CT scan as a surrogate. The accuracy of the algorithm was tested on 60 synthetic C-arm images created from the preoperative CT images of 20 complex PH fracture cases (Dataset A) and on 12 real C-arm images of a prefractured human anatomical specimen (Dataset B). The predicted outer boundary shape was compared with the known exact solution by (1) a calculated matching error and (2) two experienced shoulder trauma surgeons.

A prediction accuracy of 88% (with 73% 'good') was achieved according to the calculation method and an 87% accuracy (68% 'good') by surgeon assessment in Dataset A. Accuracy was 100% by both assessments for Dataset B.

By seamlessly integrating into the standard perioperative workflow and imaging, the intuitive shape-matching-based aid, once developed as a medical device, has the potential to optimize the accuracy of the reduction of PH fractures while reducing the number of X-rays and surgery time. Further studies are required to demonstrate the applicability and efficacy of this method in optimizing fracture reduction quality.