Jordy van Sambeeck

Chapter 1 22 techniques of osteotomy can differently affect biomechanical properties of the tibia. Various osteotomy techniques lead to different stress risers thereby affecting the fracture probability. So, different techniques can differently alter the blood supply of the bone and lead to different biomechanical strength. A surgical technique should aim for the best clinical result with the lowest complication rate. However, studies describing results of different techniques of TTO in terms of procedure specific complications are lacking, but it is essential to have knowledge on this for an optimal patient specific treatment plan. Outcome measurement The goal of treatment of patients with patellofemoral instability is to create a stable patella and decrease functional impairment and pain due to patellar instability. An obvious outcome measure is recurrent dislocation or instability of the patella. This objective outcome parameter is always described in studies reporting on conservative and/or surgical treatment of patients with patellofemoral instability. However, this objective outcome is not always the most critical in the perspective of a patient, who might value more subjective outcome such as functional impairment, inability to perform tasks of daily life and inability to participate in sports both caused by the instability and the concomitant pain. Measuring only recurrent dislocation, could lead to a false good objective outcome, while the subjective outcome (in the outcome domain pain for instance) might be worse than before treatment. Another issue that might influence the objective outcome recurrent dislocation the other way around (false worse objective outcome) is the risk of recurrent dislocation due to demographic risk factors such as age at first dislocation, number of previous dislocations and grade of trochlear dysplasia. Ignoring these risk factors and with that the natural course, might bias the objective outcome. In addition to objective outcome, subjective outcome can be measured by valid and reliable disease specific patient reported outcome measurements (PROMs), which currently lack in Dutch language for patients with patellofemoral disorders. Outline dissertation The issues described in this introduction illustrate the complexity in decision making for adequate treatment of patients with patellofemoral instability due to its multifactorial character. This thesis is built on knowledge and evidence from previous research on patellofemoral instability, both national and international. Major international developments on patellofemoral instability include the definition of anatomic and radiographic factors affecting patellar instability including trochlear dysplasia by Dejour in 1994 4 , the description of the rationale for MPFL-reconstruction by Arendt in 2000s, the description of new trochleoplasty principles by Dejour 24 (1990) and Bereiter 25 (1994) and the description of the