Assembly of osseous fragments in orthopaedic surgery: the need for new standards of evaluation

In orthopaedic surgery, intra-operative bone machining and assembly of osseous fragments are two very important research areas. One of the most challenging applications is the treatment of malignant osseous tumors within the pelvis due to its complex tri-dimensional geometry. The conventional surgical procedure includes tumoral resection (cutting of the osseous tumor) and reconstruction by allograft (assembly of fragments). Accuracy of bone cutting and osseous assembly has not yet been documented. This paper presents an experimental study on plastic bones, with experienced surgeons working under ideal conditions. The goal was to assess the accuracy by using geometrical parameters resulting from the surgical usual language: surgical margin for tumor cuttings, and maximal gap, gap volume and mean gap between the 2 osseous fragments. Both mean values and correlation between assembly parameters were relatively poor. Experienced surgeons did not manage to consistently perform accurate cuttings and osseous assemblies, even under ideal working conditions. The complex tri-dimensional architecture of the pelvis can mainly explain this inaccuracy. There is a need to adapt computer and robotic assisted technologies for tumor cuttings and osseous assemblies. Finally, our attempt to evaluate accuracy using simple geometrical parameters, was not satisfactory. There is a need to define new evaluation standards for these assemblies. We think that mechanical engineering tools like geometrical tolerances and mechanical fittings are more suitable for this problem of quality evaluation.