On 20 January 2015 Vahur Metsna will defence her doctoral thesis „Anterior knee pain in patients following total knee arthroplasty: the prevalence, correlation with patellar cartilage impairment and aspects of patellofemoral congruence“.
Supervisor: Associate Professor Aare Märtson (Department of Traumatology and Orthopaedics)
Opponent: professor Christoph H. Lohmann, Dr. med. (Magdeburgi Otto von Guericke University),
Associate Professor Bruno Verschuere, University of Amsterdam
Anterior knee pain (AKP) is the cause of dissatisfaction with an artificial joint in more than half of patients following total knee arthroplasty (TKA). The prevalence of AKP following TKA has not been studied in Estonia before. We estimated the prevalence of AKP in patients who had undergone TKA without patellar resurfacing in East-Tallinn Central Hospital. We diagnosed a 20.2% prevalence of AKP in a postal survey based solely on patient reported data and a 60% prevalence of AKP using physician specific information. A patients’ gender, mobility of the tibial insert and Outerbridge grade 4 cartilage defects of the patella diagnosed at knee replacement did not predict the incidence of postsurgical AKP following TKA without patellar resurfacing. The etiology of AKP is multifactorial and degeneration of the articular cartilage of the patella may be one of the causes. Histological changes precede macroscopic degeneration of the cartilage and this is why only a visual inspection may lead to improper conclusions regarding the condition of the cartilage. We evaluated the state of the patellar cartilage during TKA with the OARSI score, which combines the histologic assessment of depth with a visual inspection of the extent of cartilage impairment. We discovered that the OARSI score of the patellar cartilage correlates positively with postoperative AKP following TKA with unresurfaced patella. Patients with greater patella cartilage impairment, as expressed by higher OARSI scores, have a higher risk of AKP. Resection of the joint surfaces during knee replacement and stress-induced remodelling of the unresurfaced patella distort the landmarks necessary for measuring patellofemoral congruence using current methods. We introduced a reliable new radiographic measurement of patellofemoral congruence that evaluates patellar alignment in the axial plane following TKA with unresurfaced patella – the patellar shift index (PSI). The necessary landmarks for the calculation of PSI are always present and easily discernible. PSI is independent of radiographic magnification or knee dimensions and is applicable on different media such as digital images and printed radiographs.