Improvement in Patient-Reported Outcomes after Revision Total Knee Arthroplasty Is Comparable to Primaries in Some Diagnoses, but Not Others.

BACKGROUND

Patient-reported outcome measures (PROMs) are becoming increasingly important for reimbursement after primary total knee arthroplasty (TKA) and are likely soon to follow for revision TKA (rTKA). Therefore, as the Centers for Medicare and Medicaid Services establish criteria for minimal clinically important differences (MCID), substantial clinical benefit (SCB), and patient-acceptable symptom state (PASS) metrics, it is critical to understand which patients have the greatest propensity for clinical improvement after rTKA. This study compared PROMs of rTKAs by diagnosis to a cohort of primary TKAs.

METHODS

A total of 2,308 primary and 340 aseptic rTKAs using consistent clinical protocols were retrospectively reviewed. Study data were extracted from patient health records. Modern PROMs and their associated MCID, SCB, and PASS thresholds were evaluated with P < 0.05 as significant. The mean follow-up was 27.1 months (range, one to 153).

RESULTS

Primary TKA and rTKA cohorts did not differ by demographic variables (P ≥ 0.10); however, primaries had slightly longer follow-ups (mean five months, P < 0.001). Satisfaction for cases revised for loosening (81%) and polyethylene wear/osteolysis (72%) was not different compared to primary TKAs (84%, P ≥ 0.19). The mean improvement scores for University of California, Los Angeles Activity Level and pain with level walking were not different when comparing primary TKAs to cases revised for loosening (P ≥ 0.73). Primary TKAs achieved MCID, SCB, and PASS thresholds most often (range, 60 to 90%), followed by revisions for loosening and wear/osteolysis (range, 48 to 81%); and then arthrofibrosis and instability (range, 33 to 70%; P ≤ 0.009).

CONCLUSIONS

Study results show that rTKAs for loosening and polyethylene wear/osteolysis may have comparable improvement in outcomes compared to primary TKA. Study results provide data to possibly help Centers for Medicare and Medicaid Services set rational metrics for reimbursement and set appropriate expectations.

LEVEL OF EVIDENCE: III.