Discussion
fatigue, aseptic loosening, UKA, fractures, UKA failure
RECRUITMENT, OSTEOARTHRITIS, COMPLICATION
According to the main findings of the present clinical trial, MB implants performed similar to FB in PKA in octogenarians. The MB group demonstrated shorter surgical time. No difference was found in PROMs, ROM, implant positioning, and survivorship.We were unable to identify previous clinical study which compared MB versus FB in PKA in octogenarians. Similar results were found in previous systematic reviews and meta-analyses in the younger population, which found no clinically relevant benefits of MB over the FB implants [Osteoarthritis progression to the contralateral side, aseptic loosening, and polyethylene insert wear, are the most common reason for revision in PKA [This data regarding aseptic loosening, is coherent with current literature. In fact, the primary mechanisms for UKA failure have remained consistent since early clinical reports in the 1980s. Goodfellow et al. cited aseptic loosening as the primary reason for revision (incidence 6.6%) in their series of 103 patients with an MB implant at mean follow-up of 3 years [Insights on implants biomechanics might explain such difference in the reasons for revision. Given their more congruent bearing surfaces with a larger contact area, MB implants have been introduced to better reproduce the physiological knee kinematics [Regarding medial collateral ligament (MCL) tension, a computational study highlights that the implantation of an UKA to the medial side influence the distribution of load transfer in knee joint. In other words, MCL force increase keeps the knee from tilting too much into valgus during loading, thus preventing overload on the lateral side. In addition, decreased contact stress on lateral compartment in valgus model supported it. Therefore, more loads pass throughout the medial compartment even in optimum balancing condition. It may lead to clinical problems such as loosening of the tibial component or fractures of the medial tibial plateau or the underlying bone [The flat tibial component of FB implants, given their fatigue and sheer stress-related mechanism, are less compliant during flexion and can lead to point loading; hence, they are more prone to inlay surface deformation and delamination [The present study has several limitations. Patients were not randomly allocated. These limitations impacted negatively the quality of our conclusions, increasing the risk of selection, detection, and performance biases. However, we must point out that randomization and blinding is not easily accepted by patients and surgeons alike. The reduced sample size may jeopardize the efficacy of such study to identify seldom complication; however, given the restriction of the eligible orthopedic interventions during the Covid-19 pandemic, the patient recruitment stopped. Moreover, 26% (19 of 73) of patients were lost at follow-up. In this respect, we further remark the negative impact that the Covid-19 pandemic exert on the conduction of the present study, especially in the patient follow-up.