One-year correlation between smart implantable device-derived gait metrics and patient-reported outcomes after primary total knee arthroplasty.

BACKGROUND

Continuous recovery monitoring after total knee arthroplasty (TKA) traditionally relies on patient-reported outcome measures (PROMs), which are limited by subjectivity. A smart implantable device (SID) provides objective, implant-derived gait data, which enables longitudinal assessment of recovery. This study evaluates one-year outcomes comparing PROMs with smart implant data to assess correlation and recovery trajectories.

METHODS

A retrospective cohort study of 356 patients undergoing primary TKA with the SID between May 2023 and May 2024 at a single high-volume ambulatory surgery center. When available, PROMs (KOOS Jr., VR-12 PCS/MCS, and NRS pain) and SID metrics (step count, distance, cadence, walking speed, stride length, functional ROM, and tibial ROM) were analyzed at 6 weeks, 12 weeks, 6 months, and 1 year. Spearman correlations assessed associations between PROMs and SID metrics, adjusted for demographics.

RESULTS

Both PROMs and SID metrics improved significantly across all timepoints (p < 0.001). Step count increased from 2,314 to 4,465 steps/day, walking speed from 0.57 to 0.66 m/s, and KOOS Jr. from 54.8 to 76.3. However, correlations between PROMs and SID metrics remained weak at 6 months and 1 year. The VR-12 PCS modestly correlated with step count, distance, stride length, and walking speed (r ≤ 0.35), which diminished after adjustment. Neither KOOS Jr. nor VR-12 MCS was significantly correlated with SID metrics.

CONCLUSIONS

Over one year following TKA, PROMs and SID-derived gait metrics both improve, yet remain weakly correlated, suggesting they may be complementary in postoperative assessment. The SID offers continuous, objective insight into functional recovery, enhancing traditional PROM-based follow-up.