Background/Purpose: A number of TKA recipients have suboptimal improvements after surgery. Our objective was to establish the efficacy of a motivational-interviewing (MI)-based telephone intervention aimed at improving functional outcomes post-TKA and to identify subgroups especially likely (or unlikely) to benefit from the intervention.

Methods: We conducted the RCT to compare functional status in TKA recipients randomized to one of two strategies: 1) enhanced postoperative care with frequent follow-up by a care navigator; 2) usual postoperative care. Those who were randomized into the care navigation arm received ten calls from a trained non-clinician care navigator over the first 6 months post-TKA. The trained navigator used theory driven MI to engage TKA recipients in discussions about their rehabilitation goals, including plans for and confidence in achieving those goals. Patients in the usual care arm received standard postoperative care. Patients in both arms were assessed at baseline, 3 and 6 months post-TKA. The study enrolled subjects 40+ years of age with OA who were scheduled for TKA. Primary outcome was the difference between the arms in WOMAC function score change, over the 6 months post-TKA. We defined a satisfactory functional improvement as either achieving WOMAC function scores <15 or reducing pre-operative functional score by 19+ points, suggested as MCID in TKA patients (Escobar, 2007). We examined whether sex, obesity and pain catastrophizing affected the efficacy of the care navigator intervention.

Results: We enrolled 309 TKA recipients, average age 67 years; 60% female, 84% Kellgren-Lawrence Grade 4, 50% obese (BMI>=30kg/m²). Mean pre-operative WOMAC function score was 40 (18), on a 0-100 scale, 100-worst. Baseline characteristics did not differ between study arms. At 6 months, participants in care navigation arm improved by 29.4 (16.1) points compared to 26.1 (18.3) in control arm (p=0.1126). Overall, 21% of study participants did not achieve satisfactory functional improvements, with similar rates across arms. Greater pain catastrophizing led to less improvement overall and its association with poor outcome was more prominent among females compared to males (p value for interaction = 0.002). Further analysis, restricted to females, showed that greater pain catastrophizing modified the impact of the intervention: females with a low degree of pain catastrophizing improved by 8 points more (33 vs. 25) in the navigation arm than in the control arm, while females with a high degree of pain catastrophizing improved by five points less in the navigation arm than in the control arm (p-value for interaction= 0.0233).

Conclusion: The results of this RCT did not show benefits of the MI based enhanced postoperative care navigation in functional improvements in TKA recipients. The negative overall result could be explained by differential effect of intervention among females with high and low levels of pain catastrophizing. Greater focus on understanding the determinants of and effective therapies for reducing pain catastrophizing could improve the efficacy of interventions focused on better functional outcomes in TKA recipients.