Our last paper will be by Dr. Rohan Bhimani, and he will be talking about femoral length and lateral knee x-rays, how they influence the accuracy of radiographic landmarks for MPFL complex reconstruction. Good morning. I would like to thank all my co-authors, the Academy, AUSSM, and ISTCOS for this opportunity. I'm Rohan Bhimani. I'm one of the research fellows at Massachusetts General Hospital. My co-authors and I have no disclosures relevant to this talk. So the medial patellofemoral complex is described as consisting of two bundles, the straight inferior bundle of the medial patellofemoral ligament and the superior oblique bundle comprising of the medial quadricep tendon femoral ligament. Accuracy of femoral tunnel positioning is critical during MPFC reconstruction, and this has been shown in literature in different articles. However, many surgeons utilize intraoperative fluoroscopy to accurately position MPFC femoral tunnel. There are various radiographic landmarks that have been described in literature. However, Shuttles Point is one of the most frequently cited radiographic landmarks for MPFC reconstruction. Ziegler and his colleagues showed that Shuttles Point can be erroneous when there is more than five degrees of deviation from a true lateral projection. Aside from getting a true lateral image, visible femoral length during intraoperative assessment has not been standardized. So the main purpose of our study was to assess the effect of visible femoral length on the accuracy of radiographic landmarks of the MPFC. In our study, nine unpaired cadaveric knees were included. None of these specimens had any signs of knee OA or ligamentous instability or previous injuries or surgeries. The MPFC footprint was exposed on the medial femur, and the proximal and distal boundaries of the MQTFL and the distal boundary corresponding to MPFL were marked, as you can see on this image on your right. We then obtained lateral fluoroscopic images of the knee, and we assessed each knee in one centimeter length increment of visible femoral length, starting from one centimeter proximal to the posterior condyle of femur and going up to eight centimeter of visible femoral length. The MPFC midpoint on each image were described relative to the posterior cortical line of the femur and line perpendicular to the posterior cortical line relative to the proximal margin of the posterior condyle. And images were then measured using ImageJ, and we used linear regression analysis to assess the effect of femoral length on radiographic position of the MPFC. In addition, we also performed ROC curve analysis and urine statistics to determine the minimum visible femoral length that should be obtained interoperatively. So looking at our results, we found that when using posterior cortical line as a reference, the midpoint of MPFC was 4.1 millimeter posterior to the posterior cortical line when the femoral length was eight centimeters, and it moved anteriorly as the visible femoral length decreased, especially when the visible femoral length was less than four centimeters or less. And it went up to 1.1 millimeters anterior when the visible femoral length was one centimeter. However, we did not see any proximal or distal relationship change when we use the line perpendicular to the posterior cortical line passing through the proximal margin of the medial condyle. On our linear regression analysis, we saw a relationship between the visible femoral length and the anterior position of the MPFC on the radiograph with the slope coefficient of 0.636, which means that for every one centimeter decrease in the visible femoral length, the anatomic footprint of MPFC moved anteriorly by 0.6 millimeter, which can be appreciated on the image on the right, where image A represents the visible femoral length is eight centimeters, and as you go down to image H, where the visible femoral length is one centimeter and the midpoint of MPFC moves anteriorly. Looking at our ROC curve analysis, we found that the visible femoral length should be at least four centimeters intraoperatively to accurately localize the femoral tunnel positioning with an AUC of 0.8 and accuracy of 72.9%. Moreover, our inter and intra-observer reliability were excellent in this study. So to conclude, the radiographic landmarks for MPFC femoral tunnel footprint can change depending on the length of distal femur visible on radiographs. We found that at least four centimeters of femoral shaft should be visible for radiographic landmarks to be accurate. As fluoroscopy is frequently used intraoperatively for MPFC reconstruction, our findings may serve as a guide when assessing femoral tunnel placement on fluoroscopy. These are our references. Thank you.

Dr. Rohan Bhimani

femoral length

lateral knee x-rays

radiographic landmarks

MPFL complex reconstruction