Jordy van Sambeeck

Chapter 2 40 of 30-40˚ on conventional x-ray. They state that a patellar height measurement that utilizes a femoral reference point is better than a tibial based method when patella alta is suspected. According to them a patellar height measurement that utilizes a femoral reference point would be more suitable when patellofemoral joint pathology due to patellar height is considered. A possible limitation of this study could be that a lot of the conventional radiographs were not perfect lateral views. Also, the scans were of variable quality because they came from a variety of hospitals. This could result in imperfect measurements; however it was decided not to change this because it is what best represents daily practice in most hospitals. With literature being divided on the best way to measure patellar height, clinicians are using many different methods. As for any clinical measurement, in order to accurately communicate between clinicians, define indications for surgery or do clinical research, it is important to have a gold standard. With most clinicians having accessibility to CT and/or MRI nowadays, it is important for that gold standard measurement method to be applicable to multiple imaging modalities. Conclusion In this study the Insall-Salvati ratio shows better intra- and inter-observer reliability than the Blackburne-Peel ratio, the Caton-Deschamps ratio and the modified Insall-Salvati ratio on all imaging modalities. Radiography and CT seem to have better reliability than MRI. The patellotrochlear index however shows good inter- and intra-observer reliability on MRI. Only for the IS method is there acceptable agreement between CR and MRI. This means the established Insall-Salvati normal values could be used for MRI as well. This study shows that the most reliable method to measure patella height is the Insall-Salvati ratio measured on conventional radiographs or the patellotrochlear index on MRI.