In the current prospective observational study, patients scheduled to undergo surgical treatment for lumbar spinal disease were consecutively recruited at a single institution. The study was approved by the ethics committee of our institution (No.2428). All participants were informed of the purpose of the study, received information, and provided written consent.
Inclusion and exclusion criteria
The subjects were 30 to 90 years old who underwent surgeries at our hospital for lower back pain and lower limb symptoms due to lumbar degenerative disease. The diagnosis of lumbar degenerative disease was made by the treating spine surgeon based on the clinical evaluation, radiographic, and magnetic resonance imaging findings. The surgeries were performed by two spinal surgeons.
The exclusion criteria were as follows: (1) presence of motor weakness or deficit; (2) presence of severe painful osteoarthropathy; (3) coexisting gait disorder associated with a disease other than degenerative lumbar disease; and (4) a psychiatric or cognitive disorder.
Actual physical activity measurement
The objective physical activity of participants was evaluated using the Actigraph® Micro-Motion logger (Ambulatory Monitors Inc., Ardsley, NY, USA), a wristwatch-shaped waterproof omnidirectional accelerometer (size: 2.5×0.9 cm; weight: 14 g), with which acceleration is transduced by a piezoelectric element with a sensitivity of 0.01 G/min, and these voltages were recorded and averaged in 1-min epochs. The Actigraph is an evidence-based tracking system designed for continuous 24-h monitoring and analysis of activity levels and movement counts during both waking and sleeping hours. Each participant wore the logger on the non-dominant wrist for 1 week for each time point, allowing us to calibrate the data for daytime activities (between 8 AM to 6 PM). Data were collected and analyzed using the dedicated Action-W software (version 2.4.15), based on the validated algorithms (the Cole-Kripke, Sadeh, and University of California San Diego) . Outcome measures included items reported in previous studies for comparisons [7,12,13]: the proportional-integrating mode (PIM), the total amount of movement in a 1-min epoch. The PIM provides a high-resolution measurement (range: 0–65,000) of the area under the rectified analog signal, which is designed to quantify more sedentary types of motions. We measured the mean active count (MAC) in PIM before surgery and 1, 3, 6, and 12 months after surgery.
Patient-based outcome measurements
Clinical symptoms were evaluated using the visual analog scale (VAS) score for lower back pain, leg pain, and leg numbness ranging from 0 (no pain) to 100 mm (extreme pain), the Oswestry Disability Index (ODI) (0-100 points), the Roland-Morris Disability Questionnaire (RDQ) (0–24 points), and the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ). The first two items, VAS and ODI, can be used to evaluate lumbar pain, leg pain, and numbness, but these do not directly measure symptoms that occur in association with certain postures and activities. The RDQ was designed specifically to measure the impact of lumbar pain on the quality of life. The JOABPEQ includes 25 questions based on the RDQs and Short Form 36 (SF-36). Scores were calculated based on the answers to questions in five domains: pain-related disorders, lumbar spine dysfunction, gait disturbance, social life dysfunction, and psychological disorders. The score for each domain was calculated according to official guidelines and ranged from 0 to 100 points with lower scores indicating greater symptom severity, which is deemed proportional to the patient’s clinical condition [14,15].
To evaluate the change in the activity amount, the postoperative MAC divided by the preoperative MAC multiplied by 100 was calculated as the percentage change in each period. First, the percentage change before and after the surgery was calculated with a linear mixed model for repeated measures. Additionally, to evaluate the relationship between changes in the amount of activity for each period, a single regression analysis was performed using the former as the explanatory variable and the latter as the objective variable in the two periods.
Next, to evaluate the transition of patient-based outcome as well as activity level, the relationship between the preoperative and postoperative score was evaluated in each item using the Wilcoxon signed-rank test.
All data are reported as means ± standard deviations, unless otherwise indicated. We defined the significance level at 5% and used SAS Version 9.4 for all statistical analyses in the current study.