Cervical spondylosis is a chronic degenerative condition of the spine that affects the vertebral bodies and intervertebral discs. It can lead to disc herniation, osteophyte formation, and ligament hypertrophy, ultimately resulting in nerve root and spinal cord compression [1]. A long-term follow-up study indicated that anterior cervical discectomy and fusion (ACDF) can yield favorable outcomes when conservative treatment is ineffective [2]. It is characterized by minimal trauma, low complication rates, high fusion rates, and mild postoperative pain and demonstrated clinical effectiveness, leading to its widespread clinical application [3]. Accordingly, since 1996, ACDF has evolved into a standard outpatient procedure in Western countries [4–7].

Recent meta-analyses have shown that outpatient ACDF surgery is safe, with complication rates comparable with those of inpatient ACDF surgery in carefully selected patients [8]. A study indicated that surgeons can safely perform outpatient ACDF surgeries by using appropriate patient selection criteria and perioperative management protocols [7]. Nevertheless, it remains a high-risk operation that requires exceptional surgical skills and experience. Despite the rarity of postoperative hematoma, it is a serious complication that can lead to airway obstruction, respiratory difficulties, and spinal cord compression, and in severe cases, it may be life-threatening [9]. Although evidence suggests that a postoperative observation period of 4–6 hours following outpatient ACDF for 1–2 levels is safe and feasible, significant complications, such as hematoma, can typically be identified within this timeframe [5,6]. Reports on outpatient ACDF surgeries in Western countries primarily focus on Caucasians [10]. The coagulation function varies across different racial groups [11]. Specifically, East Asians tend to have a higher bleeding risk than Caucasians [12,13], which may contribute to the high risk of postoperative hematoma in East Asians undergoing ACDF. Consequently, probably due to concerns about the risk of death [14], there have been no reports in East Asia so far.

Currently, orthopedic outpatient surgeries, such as arthroscopy, vertebroplasty, and percutaneous endoscopic lumbar discectomy, are conducted in China [15–17]. However, outpatient ACDF surgery is currently in its preliminary exploration stage. With the increasing experience of surgeons using microscopes/loupes, as well as advancements in implants, ACDF has evolved into a common procedure [18]. In recent years, based on our advanced ACDF surgical techniques, strict patient inclusion criteria, and precise postoperative management, our department has initially explored outpatient ACDF surgery among Chinese Han patients. Thus, this study retrospectively analyzed and reported the safety, efficacy, adverse events, etc., associated with the technique.

All methods performed in this retrospective study were conducted in accordance with the Declaration of Helsinki, and this study was approved by the Medical Ethics Committee of the Second Affiliated Hospital of Soochow University (approval no., JD-HG-2022-47). The participants provided written informed consent.

Outpatient ACDF surgery has rapidly improved in Europe and the United States in the past 30 years. Many studies have shown that ACDF performed as an outpatient surgery has lower complication and readmission rates, with the same level of safety as inpatient surgery [4,8,19]. However, compared with the Black and Caucasians, the coagulation functions of the East Asians were significantly different [11,20]. As one of the largest racial groups in East Asia, the Chinese might experience more bleeding, which usually requires careful hemostasis intraoperatively [12,13], and the risk of postoperative hematoma may be higher. Thus, whether the safety of ACDF outpatient surgery in Han Chinese patients is consistent with those of the Black and Caucasians remains unaddressed. To our knowledge, this is the first study of Chinese Han patients undergoing this procedure. The results showed no significant difference in safety and efficacy between the two groups. Hospital costs, length of preoperative waiting time, and the length of hospital stay were considerably decreased in the outpatient group.

A concerning factor related to outpatient ACDF surgery was the potential inability to promptly detect postdischarge hematoma. Studies have revealed that postoperative hematoma, which is often found within 4–6 hours after surgery, is the most serious complication [5,6]. Furthermore, delayed occurrence of cervical hematoma is a rare but known complication of this surgery. O’Neill et al. [21] reported a 0.7% hematoma rate, of which 35% had a late onset. The increase in fibrinolytic activity may lead to an increase in blood loss in spine surgery [22]. Compared with the Black and Caucasian populations, the coagulation functions of the East Asian population were significantly different, with lower levels of antihaemophilia factor (factor VIII) and fibrinogen [20], in addition to a relatively prolonged APTT and decreased thrombin generation [11]. The APTT of East Asians (29.7 seconds) was significantly higher than that of Caucasians (26.4 seconds) [11]. In addition, East Asians exhibited a higher bleeding risk than Caucasians [12,13]. Therefore, East Asians may encounter increased bleeding and delayed clotting during surgery.

The mean APTT of the patients in our cohort was 33.51 seconds, which was significantly higher than previous reports of both the Black and Caucasians (26.4 seconds) [11]. No significant differences in the drain outputs and EBL were found between the outpatient group (12.21±8.22 mL and 7.26±3.72 mL, respectively) and the inpatient group (12.48±8.33 mL and 9.14±7.65 mL, respectively). Postoperative Hb and Hct levels decreased to varying degrees in both groups. The average Hb level fell by 8.43 g/L in the outpatient group and 9.02 g/L in the inpatient group, showing no significant difference between the two groups. Changes between preoperative and postoperative Hb and Hct levels include hidden blood loss and intraoperative blood loss. The levels of Hb reduction preoperatively and postoperatively in this study were lower than previously reported (10.0 g/L) [22]. This may be related to meticulous technical exposure with careful hemostasis. The international normalized ratio (INR) is a measure of the extrinsic pathway of coagulation. Previous studies have indicated that a preoperative INR value of >1.2 and preoperative anemia were high-risk factors for hematoma after ACDF [14]. The preoperative INR value of the patients was low in this study. Anemia was not noted in either group before surgery, indicating that both groups had a favorable preoperative nutritional status. This also establishes the groundwork for the expedited recovery of patients postoperatively and the safety of outpatient surgery. No epidural or retropharyngeal hematomas were found in this study. Compared with Caucasians, Chinese Han have significantly different coagulation functions, which may lead to a higher risk of intraoperative bleeding or postoperative hematoma [12,13]. However, the risk of return to the operating room is generally the same for Caucasians and Asians [23], with the most common reason being postoperative hematoma [24]. No differences were noted in the incidence of postoperative hematoma between the outpatient and inpatient groups. In general, outpatient ACDF surgery is also safe among Chinese Han patients.

In a retrospective analysis conducted by Garringer and Sasso [25], the readmission rate of outpatient ACDF surgery was 6% because of nausea and pain at the iliac bone graft site. In another study of 629 patients who underwent outpatient surgery for one-level ACDF and 365 patients who underwent outpatient surgery for two-level ACDF, Adamson et al. [5] found a delayed discharge rate of 0.8% and a readmission rate of 2.2% within 30 days. In this investigation, three patients in the outpatient group had delayed discharge because of postoperative nausea and vomiting, dysphagia, and dizziness, resulting in a delayed discharge rate of 7.1%. In addition, one patient had an unplanned readmission because of fever and dizziness on postoperative day 4, leading to an unplanned readmission rate of 2.4%. The higher delayed discharge rate in this study can be attributed to these cases being performed early in our practice and to the limited case volume.

In 1996, Silvers et al. [4] conducted a comparative analysis of 53 inpatient and 50 outpatient procedures, revealing no significant difference in complication rates. According to Gennari et al. [26], the complication rate was exceedingly low, even lower than that of patients treated as inpatients in comparative studies. Consistent with research conducted in Western countries [4,26], no significant difference in the incidence of adverse events 30 days after surgery was noted between the two cohorts in this study. Dysphagia was the primary postoperative complication observed in both cohorts, which resolved spontaneously within 3–5 days. Studies have indicated that dysphagia is a prevalent complication of ACDF. The majority of dysphagia symptoms occur in the immediate postoperative period and are typically mild, gradually diminishing over time [27]. Dysphagia significantly affects the daily life of patients who underwent outpatient ACDF. Care must focus on dysphagia prevention [27].

Postoperative nausea and vomiting are among the main factors contributing to extended hospital stay for outpatient surgery, and such postdischarge complications may also lead to unplanned readmission [28]. Consequently, a risk assessment for postoperative nausea and vomiting must be undertaken in patients undergoing outpatient ACDF, and multimodal prophylaxis must be implemented based on the risk assessment levels [28]. Postoperative dizziness hinders patients from promptly engaging in ground-based exercise for rehabilitation, thus significantly impeding postoperative recovery. The primary factors comprise a history of motion sickness, postoperative nausea and vomiting, residual effects of general anesthetic drugs, and perioperative use of tramadol and pregabalin [29].

With the introduction of the concept of enhanced recovery after surgery, the evaluation of the clinical efficacy is not only limited to the surgical complication and readmission rates but also to subjective outcome indicators. Patel et al. [19] conducted a retrospective analysis of 100 outpatient and 172 inpatient surgery cases. They compared the NDI and VAS scores of the two groups before the operation and found no significant difference in the NDI and VAS scores at each time point between the two groups. They found no significant difference in the clinical efficacy between the two groups [19]. Consistent with the results of Patel et al. [19], the present study did not find a significant difference in the JOA score and NDI between the two groups at each time point. In addition, no significant difference in the excellent rate in the MacNab criteria clinical efficacy evaluation was noted between the two groups, and the symptoms of cervical spondylosis in the two groups were significantly improved. In this study, the VAS scores of the two groups were evaluated on postoperative day 1, and the outpatient group had ≤3 points, indicating that all patients met the discharge criteria for pain. The VAS score of the outpatient group was significantly lower than that of the inpatient group for the following reasons: (1) it may be related to adequate postoperative analgesia in the outpatient group and (2) to the incomplete remission of radicular symptoms after surgery in two inpatients.

Considering healthcare cost reduction, shortening the length of hospital stays and decreasing perioperative morbidity are among the means to reduce expenses. In inpatient ACDF in China, preoperative examinations will be completed in 1–2 days, and postoperative monitoring and care will be provided in the hospital for 3–5 days following the surgery. In addition, Silvers et al. [4] demonstrated that outpatient ACDF reduced an average of $1,800 per patient. This study found that one- and two-level outpatient surgeries can reduce approximately RMB 5,000 and 2,500 Yuan in hospital costs, respectively, leading to substantial cost savings and a positive economic effect. Erikson et al. [30] examined 58 outpatient ACDFs and found high satisfaction and no compromise of patient safety. The present study showed similar results. The overall satisfaction rate was 9.81/10 in the outpatient group, which was significantly higher than that in the inpatient group.

This study has several limitations. First, the findings are confined to healthy persons and may not be generalizable to populations with significant comorbidities. Second, this was a retrospective study, which may have some bias in case selection. Third, the sample size of the patients included was small, consisting entirely of early-stage outpatient ACDF surgical cases with a relatively short follow-up period. Although no life-threatening complications (such as postoperative hematoma) occurred, the possibility of other rare or serious complications in larger sample studies cannot be excluded. Therefore, a large, prospective multicenter randomized controlled study is urgently needed to determine the efficacy and safety of outpatient ACDF surgery in China.

The results indicate that with proper patient selection, outpatient ACDF surgery has comparable safety and clinical efficacy to inpatient surgery among Chinese Han patients. Furthermore, among Chinese Han patients, outpatient ACDF surgery has equal safety and clinical efficacy to Black and Caucasian patients, has high patient satisfaction, and could significantly reduce hospital costs. In addition, strict access standards and discharge criteria can ensure sufficient development of outpatient ACDF surgery.