Assessment of the damage in retrieved patellar components

Patellofemoral complications are cited as a leading cause for revision surgery following total knee arthroplasty. Despite widespread clinical use, the decision to resurface the patella, or not, is controversial and remains surgeon dependent. Damage to the patellar component can lead to revision surgery; however, little work exists investigating the damage they sustain in vivo. Twenty-four retrieved patellar components were assessed for damage. There was a wide variation in wear scar morphology, although the mean wear scar area spanned mediolaterally in a band across the articular surface and was 364.32±64.7 mm2 in area. Maximum linear penetration was located in the lateral region of the articular surface. Assessment of damage mode grading indicated that it was more severe in the lateral quadrant, although the method's lack of consideration of the chronological progression of wear creates uncertainty over this finding. Volume change ranged from −1.3 to −45.16 mm3/year, and maximum penetration was in the lateral region. Damage to the patellar component of knee replacement has been shown to be significant. The number of components in the study was too small to determine a difference in damage in all-polyethylene and metal-backed designs; however, the volume loss of all-polyethylene patellae was found to be significant.