Surgical Treatment of Adjacent Segment Stenosis

The primary endpoint is the proportion of participants achieving a reduction of at least 30% in the Oswestry Disability Index (ODI) compared with baseline. The ODI is a validated patient-reported outcome measure assessing disability related to lumbar spine disorders on a scale from 0% to 100%. A reduction of at least 30% is considered clinically meaningful.

Disability related to low back pain assessed using the Oswestry Disability Index (ODI). The ODI score ranges from 0 to 100%, with higher scores indicating greater disability and worse functional impairment.

Pain intensity assessed using the Numeric Rating Scale (NRS; 0-10) for leg pain at rest.The NRS ranges from 0 to 10, where 0 indicates no pain and 10 indicates the worst imaginable pain. Higher scores indicate greater pain intensity.

Pain intensity assessed using the Numeric Rating Scale (NRS; 0-10) for leg pain during movement.The NRS ranges from 0 to 10, where 0 indicates no pain and 10 indicates the worst imaginable pain. Higher scores indicate greater pain intensity.

Pain intensity assessed using the Numeric Rating Scale (NRS; 0-10) for back pain at rest.The NRS ranges from 0 to 10, where 0 indicates no pain and 10 indicates the worst imaginable pain. Higher scores indicate greater pain intensity.

Pain intensity assessed using the Numeric Rating Scale (NRS; 0-10) for back pain during movement.The NRS ranges from 0 to 10, where 0 indicates no pain and 10 indicates the worst imaginable pain. Higher scores indicate greater pain intensity.

Maximum walking distance measured in meters.

generates eight domain scores (physical functioning, role limitations due to physical health, bodily pain, general health perceptions, vitality, social functioning, role limitations due to emotional problems, and mental health), each transformed to a scale ranging from 0 to 100, with higher scores indicating better health-related quality of life and functional status. Unit of Measure: Points on a scale (0-100).

Health-related quality of life assessed using the EuroQol 5-Dimension 5-Level questionnaire (EQ-5D-5L). The EQ-5D-5L evaluates five dimensions of health status (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression), each with five response levels. Responses are converted into a single EQ-5D-5L Index Score using an established country-specific value set. Higher index scores indicate better health-related quality of life. Unit of Measure: Utility index score (higher scores indicate better health-related quality of life).

Depressive symptoms assessed using the German General Depression Scale - Short Form (ADS-K). The ADS-K is a self-report questionnaire comprising 15 items, each rated on a 4-point Likert scale (0-3 points). Total scores range from 0 to 45 points, with higher scores indicating more severe depressive symptomatology and worse mood status. Unit of Measure: Points on a scale (range: 0-45; higher scores indicate more severe depressive symptoms)

Sleep quality assessed using the Pittsburgh Sleep Quality Index (PSQI). The PSQI is a self-administered questionnaire evaluating sleep quality and disturbances over the previous month across seven domains: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction. Component scores are summed to generate a global PSQI score ranging from 0 to 21 points, with higher scores indicating poorer sleep quality and greater sleep disturbance. Unit of Measure: Points on a scale (range: 0-21; higher scores indicate worse sleep quality).

Length of hospital stay measured in days from surgery until hospital discharge.

Duration of intensive care unit stay measured in days.

Proportion of participants requiring additional spinal surgery or revision surgery during follow-up.

Number and type of perioperative complications associated with the surgical procedure.

Operative duration, intraoperative blood loss

Presence of dynamic spondylolisthesis defined as a translation of ≥3 mm on flexion-extension radiographs.Unit of Measure: Participants with dynamic spondylolisthesis.

Central canal stenosis at the adjacent segment assessed on MRI using the Schizas classification (Grades A-D).Unit of Measure: Grade (A-D; higher grades indicate more severe stenosis).

Foraminal stenosis at the adjacent segment assessed on MRI using the Lee classification (Grades 1-4).Unit of Measure: Grade (1-4; higher grades indicate more severe foraminal stenosis).

Implant integrity assessed on radiographs, including evidence of implant loosening, breakage, or material dislocation.Unit of Measure: Participants with implant failure.

Segmental lordosis measured on standing lateral radiographs.Unit of Measure: Degrees (°).