The outcomes in this retrospective study based on a single-center cohort demonstrated that surgical time, blood loss, and incidence of durotomy significantly increased in OW patients. The BMI cut-off value for durotomy was also high in OW patients. A consensus on the impact of OW on perioperative complications in elective surgeries has not been established despite the influence of lifestyle-related diseases, such as hypertension and diabetes mellitus [2, 3]. The unique feature of this study in comparison with previous ones was the focus on OW. Most previous studies on the effect of increased body size on perioperative compilations focused on the differences between patients with and without obesity in mucocutaneous surgeries [14]. To the best of our knowledge, evidence has been spared on the effect of OW.
The prevalence of OW is rapidly increasing [15], and we believe that the outcomes in our study can serve as a reference for physicians to be attentive to perioperative complications in spinal surgery, not only in cases of obesity but also in OW.
Regarding surgical time and blood loss, we found that OW patients had longer operative times and greater surgical blood loss than NOW patients. A recent systematic review and meta-analysis conducted by Goyal et al. demonstrated that patients with obesity had longer operative times and greater surgical blood loss than non-obese patients in elective lumbar spinal surgery with a diagnosis of degenerative lumbar spine disease[14]. While Goyal’s study focused on patients with obesity, this study focused on both OW and individuals with obesity. Our findings indicate that even in OW patients, surgical time and blood loss may be increased. We consider that the thick subcutaneous adipose tissue affected the operative times and surgical blood loss. Jackson et al. reported that patients with obesity had thick subcutaneous adipose tissue, making it difficult to develop and maintain the operative field. This situation resulted in longer surgical times and greater surgical blood loss [13]. OW patients had longer surgical time and more blood loss than patients with normal weight because the subcutaneous adipose tissue thickens with BMI [16].
This study investigated the incidence of dural tear in elective spinal surgery. A nationwide survey of perioperative complications in all spinal surgeries, which included 31,380 patients, showed that the perioperative complication with the highest incidence was dural tear, which occurred in 2.1% of patients [17]. The incidence rate of dural tear in this study was 4.8%, and OW was independently associated with an increased likelihood of dural tear. This may be because OW patients have thicker subcutaneous tissue than NOW patients. Additionally, the distance from the skin to the dura mater is more significant, making it difficult to achieve an adequate field of vision and intraoperative manipulation. In addition to the outcomes of this study that focuses on OW patients, the influence of obesity on the incidence of dural tear has also been investigated. In Goyal’s systematic review and meta-analysis, the incidence of dural tear was not significantly different between patients with obesity and non-obese patients (MD = 0.83, 95% CI = 0.56–1.23, P = 0.48, I2 = 64%). On the other hand, the prospective comparative study conducted by Murphy, which was not included in Goyal’s systematic review, suggested that obesity was independently associated with an increased likelihood of a dural tear on adjusted analysis [18]. In Murphy’s study, a dural tear requiring repair occurred in 0.6% of 104,930 patients. Murphy et al. suggested that the increase in dural tear was due to the difficulty developing and maintaining the operative field in patients with obesity and the vulnerability of the dura tear due to various inflammatory mediators from mast cells [5]. Because dural tears were affected by age and other factors, further research on the effect of OW and obesity on dural tears is warranted.
We consider that the adverse effect of OW may be significant in lumber spinal surgery. The subgroup analysis revealed that OW patients who underwent lumbosacral surgery had longer surgical times, more blood loss, and more significant durotomy than NOW patients but not those who underwent cervical and thoracic spinal surgeries. The subcutaneous tissue of the lumbosacral spine is thicker than that of the cervicothoracic spine [13]. Additionally, Kim et al. reported that the abdominal pressure was higher in the lumbosacral spine than in the cervicothoracic spine [19]. These factors may induce adverse events during OW lumber spinal surgery. Among spinal surgeries, lumbar spinal surgery is the most common.
The outcome of the subanalysis indicated that special attention should be paid to OW patients. The subgroup analysis was conducted on both instrumentation and noninstrumentation surgeries. The number of dural tears in OW patients who underwent instrumentation surgery was higher than those who underwent noninstrumentation surgery. In a previous prospective cohort study, Smorgick et al. demonstrated no significant difference in the incidence of dural tear between patients who underwent decompression alone and those who underwent decompression and instrumented spinal fusion [20]. In their study, no conclusions were drawn due to the low number of dural tears. Previous studies that determined dural tear predictors in spinal surgery did not investigate the association between dural tear and obesity [21, 22]. The instrumentation process for patients with obesity might be complicated for surgeons due to the deep operative field because of the thick subcutaneous tissue.
Our study suggests a BMI cut-off value of 22.3 kg/m2 for perioperative complications and 25.1 kg/m2 for durotomy. No previous studies have investigated BMI cut-off values for spinal surgery complications. Compared with a previous study on obesity in spinal surgeries, the patients included in this study were relatively light in weight.[14] The results are likely to differ from one study population to another but can be helpful information for similar populations.
This study has several limitations. First, the patients were recruited from a single institution. The elective spinal surgeries were not randomly performed. Because they are elective surgeries, OW and patients with obesity tend not to be selected, thus leading to selection bias. Second, any retrospective design introduces an element of uncertainty. The medical record data may be erroneous or missing, and clinical information may be lacking. Third, functional outcomes were not evaluated. Finally, the thickness of the subcutaneous adipose tissue was not measured. Due to the retrospective non-randomized nature of the study, a multicenter, prospective randomized study is required to confirm the effect of OW during spinal surgery.