Prospective validation of an indication algorithm for UKA

Abstract

Aims and Objectives: Patients with isolated medial gonarthrosis benefit from a treatment with a unicompartmental knee arthroplasty (UKA) compared to a total knee arthroplasty (TKA). They have a shorter rehabilitation time, better function, lower morbidity and a higher satisfaction rate. However, the revision rate is higher than in patients with TKA. Patient selection and the resulting incorrect indication may be one reason. Hamilton et al.'s research group prepared a radiological "decision aid" for the indication of a UKA. The aim of this study was to validate this uncomplicated diagnostic procedure based on intraoperative findings. Materials and Methods: In this prospective study, 85 patients received routinely conventional x-rays. Strictly lateral and anterior-posterior view as well as varus/valgus stress x-rays were taken. Using Hamilton et al.'s "desiscion aid", the x-ray images were preoperatively evaluated with regard to medial and lateral cartilage damage and the function of the anterior cruciate ligament. The cartilage damage of the individual tibial and femoral compartments was also scaled and documented intraoperatively. The results of the decision aid were validated with regard to the intraoperative findings. Indication-justifying cartilage damage was defined as focal complete cartilage loss. The sensitivity (SEN) and specificity (SPE) of decision aid with regard to cartilage damage in the medial and lateral compartments and the functionality of the anterior cruciate ligament were determined. Results: In the area of the medial compartment, decision aid has a SEN and PES of 79.4% and 82.4% respectively. The SEN and SPE for lateral compartments are 98.5% and 55.0%, respectively. Intact ACLs are correctly diagnosed at 94.7%. Insufficient ACLs at 33.3%. Conclusion: These data suggest that according to our findings, only about 2 out of 10 patients are not reliably diagnosed with medial gonarthrosis. However, about 2 out of 10 patients are diagnosed with medial gonarthrosis, which does not yet have to be treated with UKA. Furthermore, it could be shown that almost all patients with a completely laterally preserved cartilage are also recognized as such. However, every second patient with relevant cartilage damage is not radiologically identified. These data refer only to the radiological findings. Coupled with the patient's medical history and clinic, the "Desicion Aid" is a very good aid for the correct indication for a UKA.