According to the United Nations 2022 Revision of World Population Prospects, the proportion of people over 65 years of age is expected to increase from approximately 9.7% in 2022 to 16.4% in 2050. The burden of spine disorders has increased substantially with the unprecedented aging population and the increase in life expectancy. Recent studies using multicenter data have showed that the increase in spinal fusions for spinal degenerative diseases was highest among patients over 75 years. Despite improved quality-adjusted life years and symptomatic benefits with spinal fusion surgery, there is an observed excess of adverse postoperative outcomes in older patients (aged 75 years and older) compared with younger patients. Enhanced Recovery After Surgery (ERAS) involves multidisciplinary perioperative measures to reduce surgical stress responses and improve perioperative outcomes and postoperative recovery. However, ERAS does not include preoperative comprehensive interventions to address or optimize the comorbidities, malnutrition, decreased functional capacity that are commonly present in older patients. In addition to the comorbid risk factors that older patients share with younger ones, older patients may also have malnutrition and cognitive or functional impairment. In older patients, the accumulation of geriatric frailty and various geriatric syndromes leads to decreased physiological reserves, resulting in a challenging recovery process after spine surgery. A possible way to overcome this variability and therefore to identify the patients at risk of adverse events (AEs) is to use specific tools developed by geriatricians and included in the so-called Comprehensive Geriatric Assessment (CGA).

CGA is a multi-dimensional diagnostic process designed to evaluate an elderly patient's medical, psychosocial, functional, and environmental resources and links them with an overall plan of treatment and follow-up. Guidelines and recommendations have addressed the importance of combined geriatric assessment and operational risks as an alternative to traditional preoperative assessment in elderly patients. The value of CGA in predicting long-term quality-of-life and functional decline has been demonstrated in previous studies on cancer surgery and hip fracture surgery; however, few studies on spine surgery included CGA in their analyses. Although some items in CGA, such as frailty and depression, have been shown to be associated with postoperative complications after spinal surgery, few studies have performed a complete evaluation of CGA in older patients. The reluctance of site leads and participants to use the comprehensive tool may reflect the volume of information it included, which may have made it difficult for clinicians to identify and use relevant sections. Most older people who have spinal disorders are frail, have comorbidities, and show a functional deterioration, which adversely affects quality of life and delays postoperative rehabilitation. Prehabilitation programs aim to strengthen patients physically and mentally before surgery by addressing modifiable risk factors during the preoperative period while they are waiting for surgery thereby filling this existing gap. Emerging evidence suggests a benefit of prehabilitation before major abdominal and cardiothoracic surgery. However, high-level evidence supporting the integration of CGA-based prehabilitation into ERAS program is still limited, particularly within the context of spine surgery.

The overall aim of this work is to examine the effect of multimodal prehabilitation combined with perioperative ERAS care (PREERAS) compared to only-ERAS in older patients (aged 75 years and older) scheduled for spinal fusion surgery. The study hypothesizes that the PRE-ERAS program will be more effective than only-ERAS care in improving postoperative clinical outcomes and patients-reported outcomes (PRO).

Study design and setting This study is a prospective, multicenter, parallel, randomized, controlled study. This study will be carried out in three tertiary teaching hospitals, including Xuanwu Hospital, Peking University First Hospital, and Beijing Friendship Hospital. The patients of control group will receive the established perioperative ERAS care. Pre-admission intervention include education on smoking and excessive drinking cessation, available counseling services, optimization of chronic disease, and nutritional assessment and support (only through nutritional education). Participants randomized to the intervention group will receive PREERAS management. PREERAS mainly consists of geriatric assessment, Vivifrail multicomponent exercise, nutritional intervention, cognitive prehabilitation and brain protection. The study will start in April 2024. The recruitment period will be 20 months, with a follow-up of 90 days. The results of the study will be expected in December 2025.

Primary outcomes: The primary outcome is the Comprehensive Complication Index (CCI; scores range from 0 to 100, with a score of 100 being death as a result of complications) which integrates all complications with their respective severities on a continuous scale ranging from 0 (no burden due to complications) to 100 (death as a result of complications). The CCI is based on the complication grading by the Clavien-Dindo Classification and captures every complication that occurred after an intervention. Postoperative complications were recorded to 90-day after surgery (definitions provided in supplementary table 1) and scored by severity using the Clavien-Dindo classification. The CCI was derived from these scores using the CCI calculator available online (http://www.assessurgery.com). Previous studies have validated the CCI as a measure of postoperative morbidity, suggesting that it offers a more comprehensive and sensitive endpoint for surgical research compared to traditional morbidity measures, such as the overall rate of complications or the rate of severe complications.

Secondary outcomes: Pain levels and pain-related function and activity limitation will be measured by visual analogue scale (VAS) and Oswestry/Neck disability index (ODI/NDI). Health- related quality of life will be evaluated by EuroQol Five Dimensions Questionnaire (EQ-5D, 0 = worst health and 100 = best health). Physical function will be assessed using 6 m walking speed and hand grip strength. Patient satisfaction will be measured using the North American Spine Society (NASS) satisfaction scale, measured on a scale of 1-4, with 1 indicating most satisfied and 4 indicating least satisfied. Answers on the satisfaction scale are as follows: The treatment met my expectations (score 1); I don't not improve as much as I had hoped, but I would undergo the same treatment for the same outcome (score 2); I don't improve as much as I had hoped, and I would not undergo the same treatment for the same outcome (score 3); I am the same or worse than before treatment (score 4). Data regarding primary and total length of hospital stay, non-home discharge, readmissions, and unplanned readmission within 90 days after surgery will be followed up. The discharge criteria for all patients were as follows: (1) preoperative symptoms are entirely or mainly relieved, or treatment has met the patient's expectations; (2) patients have no surgery-related complications, or the postoperative complications have been controlled, and (3) no further treatment is required.