[Conversions from failed unicompartmental prostheses to total knee replacement]

The evolution and challenges of unicompartmental knee prostheses (UNIS) are addressed, highlighting their use since the 1970s as an alternative to osteotomies. Over the years, these prostheses have gained popularity, although they initially faced criticism due to higher revision rates compared to total knee arthroplasties (TKA). Multicenter studies, such as that of Heck et al., revealed an increase in failures associated with body mass index and female sex. Despite this, recent reviews, such as that of Vasso et al., have shown a positive evolution in the results of UNIS, although with a higher percentage of revisions than TKA. The importance of adequate patient selection, meticulous surgical technique, and avoidance of overcorrection for surgical success is also emphasized. It is mentioned that external UNIS, although representing a small percentage of total prosthetic knees, have shown favorable results in terms of long-term survival. In addition, technical aspects such as minimal bone resection and polyethylene wear, which are crucial for the performance of prostheses, are discussed. In conclusion, the need for further research and improvement of techniques to optimize the results of unicompartmental arthroplasties is highlighted.