The higher postoperative rate of patella baja in the septic group became statistically significant even when preoperative incidence was considered. This may have been caused by infection-related scarring and by prolonged immobilization of septic knees with use of nonarticulating antibiotic spacers. By keeping these knees immobile with a nonarticulating spacer for a prolonged period in the healing phase of the infection, scar tissue may mature and form over the time between stages. A comparable example may be high tibial osteotomies, in which a high incidence of patella baja has been partly attributed to prolonged casting.11 Future work comparing the results of articulating and nonarticulating spacers will help to determine if immobilization contributes to patella baja in infected TKAs.
There are several limitations to our study. Patient outcome questionnaires were not used, and they would have allowed for the assessment of physical outcomes and emotional satisfaction by comparing outcomes between patients with and without patella baja and comparing septic and aseptic TKAs. In addition, there was no standard method for quantifying difficulty of revision, which would have enabled us to compare difficulty of revision in patients with patella baja.
Conclusion
This study identified a high rate of patella baja and decreased ROM in TKA revisions, particularly infected revisions treated with a nonarticulating spacer. It is important to determine if there are functional consequences. Further investigation is needed regarding the cause, prevention, and management of this potentially debilitating outcome after revision TKA.