151 - Validation Of The Indication ”pain Without Loosening” For Revision Of Knee Arthroplasties In The Danish Knee Arthroplasty Register

Background
13% of revisions of knee arthroplasties registered in the Danish Knee Arthroplasty Register (DKR) are for the indication “pain without loosening”.

Objectives
We aimed to investigate “pain without loosening” as indication for revision knee arthroplasties, and screen for other possible indications hidden in this category in order to improve future registration and data quality.

Study Design & Methods
We included 104 patients undergoing first-time revision knee arthroplasty for the indication “pain without loosening” from January 1, 2016 to December 31, 2018 at five Danish centers. Medical records and radiographs were reviewed for all patients and CT scans for those available.

Results
The primary knee’s were 68 total knee arthroplasty’s (TKA), 28 medial unicompartmental knee arthroplasty’s (mUKA), 3 patellofemoral prostheses and 5 hemicaps. The Kellgren-Lawrence arthrosis grades prior to primary knee arthroplasty were 1-2 (31%) and 3-4 (69%). In 103 of 104 (99%) cases we could confirm “pain without loosening” as indication for revision. We found other hidden indications in 44 (42%) cases; malposition of components (n=19), stiffness (n=13), progression of arthrosis (n=6), instability (n=3), liner dislocation (n=1), residual cement (n=1) and aseptic loosening (n=1).

Conclusions
The indication “pain without loosening” covered patients revised because of pain, but other hidden indications were present. Stiffness and malposition of components were hidden indications and lack as indication option in the DKR and other registers.
The relative high frequency of arthrosis grade 1-2 prior to primary knee arthroplasty is concerning and may explain the need for revision of a painful knee in cases without any other pathology present.