ABSTRACT Background Traditional assessments of functional recovery after spine surgery rely on patient‐reported outcomes, which are prone to bias. Wearables and smartphone activity tracking offer objective monitoring but may be unreliable if devices are not carried continuously. Capacity‐oriented measures, such as the 1‐min walk test (1MWT) and 6‐min walk test (6MWT), may be more reliable. This study evaluated smartphone‐derived interval metrics after lumbar spine surgery retrospectively. Methods iPhone Health exports from 41 patients were analyzed. A sliding‐window algorithm parsed daily distances to simulate 1MWT and 6MWT. Step counts and active time were extracted. Activity was compared across four intervals: 6‐month baseline, final 2 weeks preoperatively, early postoperative (0–2 weeks), and late postoperative (2–6 weeks). Paired t ‐tests or Wilcoxon signed‐rank tests were used, with Simes–Hochberg adjustment for multiple comparisons. Day‐to‐day stability was summarized by the coefficient of variation (CV). Pearson correlations were calculated. Results Median 1MWT fell from 98 m at baseline to 82 m in the final two preoperative weeks ( p < 0.05) and increased to 105 m by late recovery ( p < 0.05 vs. preoperative). Median 6MWT declined from 403 to 345 m preoperatively, with this decline not reaching significance ( p = 0.07), and increased to 407 m by late recovery ( p < 0.05 vs. preoperative). Steps declined from 5030 to 3825 preoperatively ( p < 0.05) and rose to 5538 at 2–6 weeks ( p < 0.05 vs. preoperative). The 1MWT and 6MWT were strongly correlated. CV was lower for 1MWT and 6MWT than for steps. Conclusions Smartphone‐derived 1MWT and 6MWT improved significantly from the immediate preoperative period to late postoperative recovery, showed lower day‐to‐day variability than longitudinal activity metrics, and were strongly correlated with each other. These findings support smartphone‐derived interval metrics as a feasible method to monitor recovery following lumbar spine surgery.
Puhakka et al. (Sun,) studied this question.