Patient Recovery Following Uniportal Endoscopic Vs Open Lumbar Spine Surgery: Objective Analysis of Postoperative Mobility and Gait Patterns Using Wearable Sensors

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Figure 1
Wearable sensor developed by Genesys Electronic Design (Sydney, Australia) placed at the center of the chest below the jugular notch.
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Figure 2
Pie charts representing the mean proportion of time endoscopic and open spine surgery patients spent in each position (standing/walking, sitting, and lying). Differences in postoperative metrics between the 2 groups were assessed using the Mann-Whitney U test for non-normally distributed data or the independent samples t test (2-tailed) for normally distributed data.
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Figure 3
Radar plot comparing the gait metrics of endoscopic and open spine surgery patients. Values represent the percentage difference between endoscopic (orange) and open (blue) spine surgery patient gait metrics, with open spine surgery patient values placed at 0%. Differences in postoperative metrics between the 2 groups were assessed using the Mann-Whitney U test for non-normally distributed data or the independent samples t test (2-tailed) for normally distributed data.

Table 1

Definition of metrics used in the present study.

Metric	Definition (units)
Position metrics
Standing/walking	Time spent standing or walking (%)
Sitting	Time spent sitting (%)
Lying	Time spent lying (%)
Steps
Daily step count	Average steps walked per day
Base gait metrics
Gait velocity	Distance traveled per second (m/s)
Step length	Distance between 2 consecutive contacts of any foot with the ground (m)
Step time	Time between 2 consecutive contacts of any foot with the ground (s)
Double support	Percentage of time where both feet are in contact with the ground (%)
Derivative gait metrics
Symmetry score	Gait symmetry index (score from 0–100), calculated as the sum of the 3 components below. Gait velocity (m/s) Step time asymmetry: step-to-step variability in step time (ms) Step length asymmetry: step-to-step variability in step length (cm)
Gait velocity variability score	Step-to-step variability of gait velocity, calculated as the coefficient of variation (CoV): $\text{[math]}$
WORM score	Quantiﬁes the stability, or “ﬁgure-of-8” motion of a subject’s trunk during walking as an indicator of falls-risk with exact calculations by Mobbs et al.23

Abbreviation: WORM, walking orientation randomness metric.
Note: Position metrics, steps, and base gait metrics are directly calculated by the sensor. Derivative gait metrics are mathematically derived from the base gait metrics and are not directly calculated by the sensor. Symmetry is related to differences between the left and right leg. Variability is related to differences in gait velocity between each step.

Table 2

Demographic and clinical characteristics of the endoscopic and open surgery participants.

Variable	Endoscopy (n = 13)	Open (n = 11)	P
Continuous variables, mean ± SD
Age, y	66.85 ± 16.94	61.82 ± 11.54	0.414
Height, cm	168.85 ± 10.73	172.00 ± 10.21	0.422
Body mass, kg	81.92 ± 19.45	83.27 ± 17.46	0.861
Categorical variables, n (%)
Female	6 (46.2)	5 (45.5)	-
Smoking	1 (7.7)	1 (9.1)	-
Diabetes	3 (23.1)	1 (9.1)	-
Hypertension	5 (38.5)	4 (36.4)	-
Falls in the past 12 months	3 (23.1)	1 (9.1)	-
Hip/knee pain	4 (30.8)	5 (45.5)	-
Back/knee pain	13 (100)	11 (100)	-
Walking aids	4 (30.8)	1 (9.1)	-
Health rating, 0–100, mean ± SD	83.08 ± 6.63	84.27 ± 5.73	0.644
EQ-5D score, mean ± SD or median (IQR)	0.770 ± 0.851	0.800 (0.040)	0.392
Mobility, n (%)
No problem	0 (0)	0 (0)	-
Slight	7 (53.8)	1 (9.1)
Moderate	4 (30.8)	5 (45.5)
Severe	2 (15.4)	5 (45.5)
Unable	0 (0)	0 (0)
Self-care, n (%)
No problem	0 (0)	0 (0)	-
Slight	7 (53.8)	7 (63.6)
Moderate	4 (30.8)	2 (18.2)
Severe	2 (15.4)	2 (18.2)
Unable	0 (0)	0 (0)
Activities of daily living, n (%)
No problem	1 (7.7)	0 (0)	-
Slight	7 (53.8)	8 (72.7)
Moderate	4 (30.8)	3 (27.3)
Severe	1 (7.7)	0 (0)
Unable	0 (0)	0 (0)
Pain/discomfort, n (%)
None	0 (0)	0 (0)	-
Slight	3 (23.1)	4 (36.4)
Moderate	8 (61.5)	7 (63.6)
Severe	2 (15.4)	0 (0)
Extreme	0 (0)	0 (0)
Anxiety/depression, n (%)
None	12 (92.3)	10 (90.9)	-
Slight	1 (7.7)	0 (0)
Moderate	0 (0)	1 (9.1)
Severe	0 (0)	0 (0)
Extreme	0 (0)	0 (0)

Note: For continuous variables, mean ± SD was reported for normally distributed data, and median (interquartile range [IQR]) was reported for non-normally distributed data. For categorical variables, frequency counts (n) and percentages (%) were reported.

Table 3

Comparison of immediate postoperative position metrics, step count, and gait metrics of endoscopic and open surgery patients.

Variable	Endoscopy (n = 13)	Open (n = 11)	Group Difference (Endoscopy—Open)
Variable	Mean ± SD or Median (IQR)		95% CI	%	P
Position metrics
Stand/walk, %	20.62 ± 12.76	19.00 ± 10.43	−8.37; 11.60	8.526	0.741
Sit, %	52.31 ± 25.43	27.82 ± 22.69	3.91; 45.07	88.03	0.022^{^a}
Lie, %	26.92 ± 18.06	53.18 ± 24.31	−44.21; −8.31	−49.38	0.006^{^a}
Steps
Daily step count	475.91 ± 254.94	244.00 ± 105.54	50.19; 413.62	95.05	0.015^{^a}
Gait Metrics
Gait velocity, m/s	0.966 ± 0.831	0.831 ± 0.629	0.061; 0.208	16.25	0.001^{^a}
Step length, m	0.650 ± 0.141	0.607 (0.088)	−0.146; 0.158	0.071	0.888
Step time, s	0.680 ± 0.059	0.675 (0.077)	−0.182; 0.118	0.741	0.423
Double support, %	21.60 (8.85)	29.88 ± 4.92	−11.10; 0.00	−27.71	0.046^{^a}
Symmetry score	87.47 ± 3.50	85.01 (3.67)	−2.58; 5.13	2.821	0.277
Variability score	11.82 ± 5.89	22.43 ± 6.77	−17.15; −4.07	−47.30	0.004^{^a}
WORM score	0.810 ± 0.82	0.817 (0.415)	−0.58; 0.57	−0.857	0.673

Abbreviation: WORM, walking orientation randomness metric.
Note: Mean ± SD was reported for normally distributed data, and median interquartile range [IQR]) was reported for non-normally distributed data.
↵a Statistically significant result (P < 0.05).