Matching of articular surface shape of selected donor and recipient sites for cylindrical osteochondral grafts of the femur -quantitative evaluation using a three dimensional laser scanner

Abstract

Objectives: Autogenous osteochondral grafting has been widely performed as the treatment of the focal osteochondral defects. In this procedure, it is ideal and important to match the articular surface shape between the donor and recipient site to reproduce the original articular surface of the femur. The purpose of this study was therefore to investigate the ideal matching pattern of the articular surface profile between the donor and recipient site of the femur using a three dimensional (3D) laser scanning method. Methods: Eleven cadaveric knees were employed for this study. The 3D laser scanner was used to obtain 3D profile of the femur. Firstly, we indicate a point of the joint surface from the obtained mesh data and calculate the normal vector of the indicated point. Moreover, we determine an analysis area of a constant diameter from the normal vector, and calculate the vertical interval (VI) from the highest and lowest points along within the analysis area. For the data analysis, we divided the donor and recipient sites into the 12 areas. In the donor site, the peripheral and middle one-third areas of the femoral articular surface in medial and lateral patellofemoral (PF) joint were extracted and additionally, these areas were divided into 3 areas(proximal/interlevel/distal). In the recipient site, the peripheral, middle and central one-third areas of the articular surface in medial and lateral femoral condyle were extracted and moreover these areas were divided into the contact surface to the tibia in knee extension (anterior) and flexion (posterior). VIs were calculated in each area and we investigated the matching of the articular surface between the donor and recipient site for cylindrical osteochondral grafts of 6, 8 and 10 mm diameter. Results: In the donor site, the VIs of the middle area were significantly smaller than those of the peripheral area. In the recipient site, the VIs of the anterior area were significantly smaller than those of the posterior area. (table1). These results showed that the VIs of the middle area in the donor site showed no significant differences with those of the anterior area in the recipient site. Moreover, the VIs of the peripheral area in the donor site showed no significant differences with those of the posterior area in the recipient site. Therefore, the articular surface profile of these areas matched each other (Fig.1). These VIs and matching patterns of the articular surface profile had a similar tendency in all sizes of osteochondral grafts. Conclusion: We demonstrated the matching of the articular surface shape between the donor and recipient site in autogenous osteochondral grafting. This study indicated that the VI of the middle one-third area in the donor site and the contact surface to the tibia in knee extension in the recipient site was small and the articular surface profile of these areas seemed to be congruent. Moreover, the VI of the peripheral one-third area in the donor site and the contact surface to the tibia in knee flexion in the recipient site was large and the articular surface shape of these areas seemed to be fitting. Considering these matching patterns, surgeons should select the donor site fitting the articular surface profile in the recipient site in order to perform ideal cylindrical osteochondral grafts. As a clinical relevance, this study will be useful for improving the donor site selection as a preoperative planning in this technique by using data derived from CT and MRI scans of the knee.