gms | German Medical Science

Objectives: Until recently, the gold standard for the sawing off stage of femur and tibial arthroplasty was the use of standard cutting blocks or the use of a navigation system. In both cases standard cutting blocks were used, which, in order to be positioned correctly, required the secondary marking steps and the installation of additional tools. All of these increased the total time of surgical treatment and often did not justify the result.

The aim of this study is to improve the functional results of knee arthroplasty by improving the method of preoperative planning and creating innovative individual cutting blocks.

Methods: In the course of this study, 17 patients aged from 58 to 70 years were examined. The study was conducted on a Toshiba Aquilion 64 computed tomograph and on a Magnetom Avanto 1.5T Tim I-Class magnetic resonance tomograph using specially developed protocols. Using a complex of adapted 3D software, we performed individual 3D modeling and prototyping of anatomical models of the knee joint on 3D printers Raise3DN2, CreatBot D600 and manufacturing individual cutting blocks on a 3D printer Objet 260 Connex 3.

Results and conclusion: The individual protocol of virtual preoperative planning, created by us, made it possible to take into account individual anthropometric indices and peculiarities of each patient, which allowed us to select the necessary sizes of the components of the knee joint and take into account the femur and tibial saw cuts. What is unique when planning the level of saw cuts, is also taking into account the cartilage according to MRI results. For the first time, a unique cutting block for performing all the five femur saw cuts was created. This cutting block takes into account all the necessary anatomical features. Due to its perfectly compact configuration, the cutting block is conveniently placed and stably fixed on the condyles of the femur. Properly selected material from which the cutting block was created, and also its configuration allow, without removing the cutting block, to perform all the five saw cuts successively. All the completed saw cuts were analyzed and proved to be in full compliance with the original plan. It was revealed that in 100% of cases the average difference in measurements of resected saw cuts of the femoral and tibial condyles compared to virtual calculations was p <0.05. The expected results of the virtual protocol precisely corresponded to the actual results obtained. The levels of the saw cuts and the sizes of the components of the knee joint endoprosthesis completely coincided.

Individual cutting blocks allowed us to reduce the time of surgical treatment by 30 minutes, to eliminate the use of standard cutting blocks completely, as well as the use of secondary tools for their installation. In all cases we managed to achieve the most favorable spatial arrangement of the components of the knee joint endoprosthesis, to restore the mechanical axis and achieve the stability of the knee joint.