While it is widely accepted that increased age serving as an indactor to predict postoperative complications, however, because the heterogeneity of different population, some younger people can be frail, and some older people can be robust. In recent years, frailty, as distinguished by 5-item Fried frailty phenotype was one of the most commonly uesd to evaluate postoperative outcomes. Nevertheless, on one hand, in previous literatures, comparing frailty and age the superiority to predict postoperative complications was the focus. In a retrospective analysis of 199 patients, Leung et al demonstrated that age was a significant moderator of the relationship between pre-frailty and body measures. Analogously, in a retrospective analysis of 8174 patients, performed by Moguilner et al, the results of receiver operating characteristic curve indicated that the addition of age to an frailty index could improve its mortality prediction. However, it cannot be ingored that frailty is significantly related to increasing age, which has been verified in previous studies[16–18]. On the other hand, in previous literatures, patients were dichotomized as non-frailty and pre-frality/frailty groups, without considering pre-frailty as an independent group[16, 24]. Hence, in our study, PS matching for age, sex, ASA, fusion levels was used to guarantee comparable clinical characteristics between groups and pairwise comparisions was performed to compare the effects of frailty on complications. After PS matching, we found that the LOS, the rate of urinary retention and surgical site infection of pre-frailty patients were greater than that of non-frailty patients, meanwhile, the pre-frail patients were more vulnerable to greater stress response associated with surgery than that of non-frail patients. Binary logistic regression indicated that CRP and pre-frailty were independently correlated with postoperative complications between non-frailty patients and pre-frailty patients. While there were statistically difference just in LOS and CRP between pre-frail and frail patients, which reflected the reasonability of grouping dichotomously in some extent.
As frailty is being increasingly studied as a common characteristic impacting postoperative outcomes in spine surgery. In a prospective cohort analysis of 668 patients following spine surgery, frailty, as distinguished by risk assessment index, Agarwal et al found that pre-frail and frail patients suffered longer LOS (3.9 d ± 3.6 vs 3.1 d ± 2.8, p < 0.001). Likewise, in a retrospective cohort study of geriatric patients receiving single-level lumbar fusion, after propensity score matching, Shahrestani et al showed significantly greater LOS (9.9 ± 10.1 versus 4.0 ± 3.9, p < 0.0001) in frail patients than non-frail patients. In line with previous studies, we found that after propensity score matching, pre-frail patients had longer LOS (7.21 ± 2.99 versus 6.35 ± 2.66, p = 0.010) than non-frail patients and similar result was found between frail patients and pre-frail patients ( 8.23 ± 3.40 versus 7.06 ± 2.95, p = 0.019). With the aging population as well as the prevalence of frality among spine surgery patients, evaluating the impact of frailty on postoperative complications has been a hot topic. In a retrospective review of 426 patients undergoing elective posterior thoracolumbar fusion surgery, frailty, as distinguished by modified frailty index, Sun et al showed that frailty was independently associated with adverse events. Shahrestani et al reported that frail patients encountered higher rate of UTI (OR: 3.97, 95%CI: 3.21–4.95, p < 0.0001), infection (OR: 6.87, 95%CI: 4.55–10.86, p < 0.0001), and 30-day readmission (OR: 1.24, 95%CI: 1.02–1.51, p = 0.035). Nevertheless, in a retrospective review of 5296 patients, Elsamadicy et al reported that modified frailty index cannot independently predict complications. In our study, while higher rate of urinary retention ( p = 0.031 ), and surgical site infection ( p = 0.021 ) were observed in pre-frail patients than that of non-frail patients, there were no significant difference in other complications, binary logistic regression indicated that pre-frailty was independently related to postoperative complications. However, similar results were not observed between pre-frail patients and frail patients. Whereas the current findings were inconsistent with previously publicated in some extent by our department. The possible explanations were as follows. Firstly, comparing with results of Sun et al, “ the severity of frailty was an independent predictor of minor complication in the short spinal fusion (SSF) group ” whose frailty was evaluted by 11-item modified frailty index, in current research, however, 5-item Fried frailty phenotype was used to describe frailty status. Secondly, propensity score matching was performed in current study to offset the effects of confounding factors, which elevating the reliablility of current study. The contradictory results revealed that high-quality studies are needed for a more precise evaluation of the impact of frail status on postoperative complications.
In previous studies[26, 27], early ambulation could significantly reduce the rate of postoperative complications and early mobilization within 24 hours after short-level lumbar fusion surgery was feasible. In our department, all patients receiving short-level fusion surgery were advocated to ambulate within 24 hours if there were no patient-reported discomfort. In this matching cohorts, not-frail patients were more likely to ambulate ( 2.06 ± 1.18 versus 2.46 ± 1.29, p = 0.006 ) and remove urinary catheter ( 1.79 ± 1.12 versus 2.14 ± 1.30 p = 0.015 ) earlier than pre-frail patients. However, there were no statistically difference between pre-frail patients and frail patients.
CRP is usually used to serve as an indicator to evaluate the stress response associated with surgery and in previous studies, which was confirmed to be correlated with postoperative complications[21, 28]. In current study, after PS matching, severer stress response was observed in pre-frail patients than non-frail patients (Fig. 2A) and even frail patients suffered more stress response than pre-frail patients (Fig. 2B), which means pre-frail and frail patients have higher risk of postoperative complications than non-frail patients. Therefore, in the perioperative management, in order to reduce postoperative complications, more attention should be paid to patients idnetified with pre-frailty or frailty.
There were several limitations in resent study. Firstly, this was a monocentric, retrospective cohort study, which may have introduced selection bias. Secondly, as only patients receiving short-level lumbar fusion surgery were included, there were 559 patients enrolled in this study, after propensity score matching, there were only 84 well-balanced patients between pre-frailty and frailty, the small sample sizes may lead to the current results. Despite above limitation, segragating patients into 3 groups according to Fried frailty phenotype and comparing stepwise is a noval attempt to evaluate the impact of frailty on postoperative complications.