Surgical treatment for lumbar disc herniation has evolved from conventional open surgery to minimally invasive procedures, such as endoscopic surgery that has grown in popularity. Percutaneous endoscopic lumbar discectomy (PELD) offers several advantages related to its limited tissue manipulation such as minimal trauma and blood loss, shorter operation time, and early return to work due to its minimally invasive nature.

However, despite technology advancement, postoperative clinical outcome parameters have been unchanged for the last 40 years [1]. Visual analogue scale (VAS), Sciatica Bothersomeness Index (SBI), and Oswestry Disability Index (ODI) are commonly used to evaluate clinical outcome. VAS directly evaluate patient’s subjective pain scale, ODI evaluates disability caused by the back pain, and SBI evaluates how the pain has bothered the patient’s daily living [2,3].

Evaluation with a scoring-based system are prone to subjectivity and is associated with varying sensitivity and specificity [4,5]. Advances in technology have brought forth mainstream use of smart wearable technologies such as smart watches. These technologies have the capability of measuring objective parameters relevant to health such as heart rate, steps count, and distance traveled. The usefulness of such measured parameters as an objective instrument for postoperative adjuvant monitoring and evaluation has not been widely studied [6,7].

In this study, we explore the correlation between changes in traditionally used outcome measurements such as VAS, ODI, and SBI with changes in the wearable-based parameters of heart rate, and steps taken following endoscopic spine surgery.

This study aims to explore the correlation and predictive value of wearable-based parameters to conventional questionnaire-based parameters for postoperative clinical outcome measure in patients undergoing interlaminar PELD.

This study used an analytical observational method with a pilot prospective cohort research design and was conducted at SMF Orthopaedi and Traumatology Dr. Sardjito Hospital from July 2023 to December 2023 or until the sample data was achieved with a nonprobability sampling method of consecutive type.

Subjects of this study were men and women over 18 years of age with herniated nucleus pulposus who would undergo the first interlaminar PELD procedure at Dr. Sardjito Hospital Yogyakarta. Exclusion criteria in this study were spinal pain related to tumor metastases, spinal fractures, spondylolisthesis, spinal stenosis, a history of previous spinal surgery. Patient with any history of heart disease, vascular disease musculoskeletal problem is excluded. Special populations such as soldiers or athletes also excluded due to special body conditioning towards exercise.

Wearables utilized in this study are the brand-new Xiaomi Mi Band 4. It uses a 3-axis accelerometer and 3-axis gyroscope to detect, measure, and analyze acceleration and movement patterns in user’s wrist. When the patient walked, the device will evaluate arm swings, creating repetitive motion data. Algorithms interpret these data patterns as steps and filter out random movements like typing or waving. This device estimated walking distance based on user’s height, sex, and weight settings, which it used to calculate an average step length. This step length was then multiplied by the number of steps you take to estimate the total distance. Photoplethysmography measures heart rate by evaluating skin perfusion based on refraction and absorption of mid-wavelength visible light detected by a sensor held on the skin. Heartrate data acquired by collecting recorded data of the daily average heart rate at one point on each follow-up session. The accuracy of the device has been validated in previous study [8]. The variables to be measured are VAS score, ODI score, SBI score, number of daily steps, daily heart rate, daily mileage from 2 weeks before surgery to 4 weeks after surgery. Wearable device data acquired weekly at one-time point to be cross-sectioned with the questionnaire-based parameter data. Routine follow-up with active effort to reach the patient was deployed to prevent lost to follow up and missing data. Any trouble with the wearable device during the observation time was reported to the investigators. To decrease inaccurate data or missing data due to removal of the band, we explained to the subject and the accompanying family or relative that the band should not be removed at any time. Its waterproof ability up to 50 ATM could prevent water penetration during shower. The device only removed from the patient’s wrist during follow-up period weekly for charging process

The data obtained were then analyzed with IBM SPSS Statistics ver. 22.0 (IBM Co., USA) with statistical tests of comparison based on the normality test. Further analysis then performed to find if any specific correlation to detect confounding factors between patient’s demographic profile (independent variable) to each data from both questionnaire-based and wearable-based data (dependent variable). Analysis then followed with measuring correlation between wearable-based and questionnaire-based parameter. If any of the wearable-based correlates significantly to all of the wearable-based, further regression analysis would be conducted.

This study was approved by the Research Ethics Committee of the Faculty of Medicine, Public Health and Nursing, Universitas Gadjah Mada (KE/FK/0583/EC/2022). The study was conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from all participants prior to enrollment, including consent for participation in the study and continuous monitoring using wearable devices.

A total of 21 patients with lumbar disc herniation undergoing interlaminar PELD were observed from 2 weeks preoperatively up to 4 weeks postoperatively. Patient demographics are presented on Table 1. No patients were lost to follow-up, and complete data were obtained for all participants.

Daily step count, distance traveled, and heart rate were continuously recorded using a smart band throughout the observation period. Measurements for all parameters are summarized in Table 2. Statistical analysis conducted using paired-sample t-test. We previously checked the normality of all data di in this research. The result, using Shapiro-Wilk test, presents p-value > 0.05.

Questionnaire-based parameters (VAS, ODI, and SBI), which reflect patients’ subjective assessments, demonstrated a significant decreasing trend over time. In contrast, wearable-based parameters (daily step count, distance traveled, and heart rate), representing objective patient activity, also showed significant changes between the preoperative and postoperative periods, as illustrated in Figure 1. Data represented as weekly routine since weekly follow-up appointed to the patient for visiting our orthopedic outpatient clinic.

Correlation study showed no statistically significant (p>0.05) between patient’s demographic profile to all outcome parameters to ensure no confounding factors were found in the subjects (n=21) (Table 3). No adjustment on patient’s demographic profile is required since no confounding factors were identified.

Linearity assumption firstly checked before further correlation study. Using scattered dots of each bivariate parameter, we identify that linearity assumption is fulfilled. Normality test show normally distributed data, by that further analysis conducting using Pearson correlation study. The analysis showed significant correlation between all questionnaire-based parameters with daily steps and distance traveled as showed in Table 4. However, only SBI was correlated with all technology-based parameters.

Multivariate regression study was conducted between wearable-based parameter and SBI based on to the significant correlation as shown in Table 5. The analysis showed no predictive ability of the wearable-based parameter to the value of SBI.

Many studies stated an urgent need for a transition from subjective to objective assessment tools. Wearables may provide valuable objective data that is significantly correlated with subjective measurement along with its additional benefits as objective measurement, which could potentially replace the less reliable subjective questionnaires. This is the first study that explore the potential use of wearable device-based parameters to predict postoperative patient outcome and satisfaction following PELD surgery.

Previous studies have found varying correlations between subjective and objective parameters, indicating the potentials of wearables to observe postoperative improvement. Mobbs et al. [9] introduced gait posture index (GPi) as an objective operative outcome questionnaire by considering the number of steps, gait speed, stride length, and posture that can be measured using wearable technology devices. The GPi measurement results showed a significant postoperative correlation between the GPi score and the ODI assessment. However, there was no significant correlation during subsequent observations. The study conducted by Scheer et al. [10] also found that there was a significant correlation between subjective assessments of the ODI, 36-Item Short Form Health Survey physical component summary, and postoperative physical activity which both increased postoperatively, but the increase in physical activity reached a plateau of improvement faster than subjective assessments. Meanwhile, Inoue et al. [11] found that the trend of postoperative physical activity continued to increase while pain assessment became stagnant 1 month after surgery.

Heart rate is highly activity-dependent, this becomes the challenges that may affect the validity of data analysis. In our study showed that heart rate parameter did not correlate significant with VAS. By that pain parameter could not be the factor related to increasing or decreasing heart rate. However, its significant corelated with SBI which lower SBI will increase heart rate due to increasing capacity to daily activities [12]. There is no previous study that explore the correlation of heart rate and SBI. However, one study presented by Södervall et al. [13], sciatica patient had sympathetic dominance compared to healthy controls which leads to higher heart rate average.

The preoperative physical activity levels observed in this cohort were notably low, with a mean daily step count of approximately 1,900 steps and a mean distance traveled of 0.85 km. These values likely reflect substantial functional limitation due to pain and disability, as evidenced by elevated baseline VAS, ODI, and SBI scores. This interpretation is further supported by the strong negative correlations between mobility-related wearable parameters and questionnaire-based outcomes, particularly SBI. According to Sears et al. [14], these activity estimates should be interpreted with caution, as wrist-worn pedometers have been reported to underestimate step counts by approximately 2.7%–10.2% compared with waist-worn devices, which demonstrate minimal underestimation.

In this study, several potential confounding factors were controlled, including analgesic use and postoperative rehabilitation protocols. Analgesic regimens and rehabilitation protocols were standardized and applied uniformly across all participants.

The use of wearables may provide several benefits, namely enhanced monitoring and recovery as wearables provide real-time tracking of patient’s mobilization postsurgery. Meanwhile, questionnaires are typically carried out at specific timepoints, creating substantial gaps of time interval in questionnaire assessment, affected by patient compliance and loss to follow-up. Reduction of patient’s mobility as indicated by the number of steps could also be the predictor of falls and mortality, which help clinicians rapidly screen patient’s health status for early intervention. In our study, we found that wearable device- based parameter did not have any regression value with questionnaire-based analysis. By that, these 2 groups of parameters cannot be interchangeable. Wearable device-based parameter should be used as real-time functional capacity monitoring while questionnaire-based parameter could be used as one-time evaluation as per follow-up period.

This study has several limitations, including limited number of samples as well as majority being within moderate disability, which may result in insignificant change of mobility compared to presurgery condition. From the wearable devices, there is an accuracy limitation and cannot explicitly log “removed time” on the data record. Further studies with larger sample sizes and longer follow-up periods are needed to more accurately evaluate the ability of wearable devices to monitor postoperative mobility progression.

The number of steps and distance traveled parameters had significant correlations with the standardized questionnaire-based parameters in patients undergoing interlaminar PELD. However, only the SBI questionnaire is significantly correlated with the 3 technology-based parameters. The new technology-based parameters have not been able to predict patient satisfaction based on standardized questionnaire-based parameters after interlaminar PELD surgery, but the advantages of objectivity, continuous assessment, and technology-based parameters may serve as complementary objective measures alongside conventional questionnaires, warranting further investigation in larger, adequately powered studies.