Surgery to correct adult spinal deformity (ASD) is invasive and carries a substantial risk of complications.1–6 Appropriate patient selection and good surgical decisions are key to successful treatment.1–7 Several risk factors have been reported for surgical complications and inferior clinical outcomes,1–7 including frailty.7–12
In 1956, Parfentjev13 described frailty as a clinically recognizable state of increased vulnerability resulting from an aging-associated decline in reserves and function across multiple systems, such that the ability to cope with everyday or acute stressors is compromised. Several studies describe the importance of frailty on outcomes in general surgery.14–17 A systematic review by Abdullahi et al16 concluded that assessing frailty may improve the preoperative work-up and optimize risk stratification measures for patients undergoing cardiothoracic procedures. A systematic review by Eamer et al17 describe the preoperative frailty assessment as a promising tool for predicting surgical complications in general surgery in an elderly population. Although frailty has long been recognized as an established clinical syndrome, the effect of frailty on outcomes of elective spine surgery is still under discussion.14–19 After reviewing 100 patients older than 65 years who underwent elective spinal surgery, Rothrock et al18 concluded that cognitive recovery at 3 months after surgery was worse in frail patients. On the contrary, Charest-Morin et al19 concluded that frailty did not predict acute complications in 102 elderly patients (older than 65 years) who underwent simple lumbar spine surgery. Moreover, the existing literature does not address whether treating patients for frailty can affect complication rates in ASD or other spine surgery, even though several frailty indexes are modifiable. The present study was conducted to investigate relationships between treatment status for frailty and complications and outcomes of surgery for ASD.
MATERIALS AND METHODS
No external funding was used for this study.
This study was approved by our institution's review board. We retrospectively reviewed charts and radiographs for 240 consecutive patients with ASD who underwent corrective spine surgery at one of three academic hospitals. All patients were enrolled prospectively and analyzed retrospectively.
Inclusion and Exclusion Criteria
To be eligible for this study, patients had to be at least 21 years old at the time of surgery, with a spinal deformity defined by a Cobb angle of 20° or more, C7 sagittal vertical axis (C7SVA) of 5 cm or more, or pelvic tilt of 25° or more. Patients had to have 5 or more fused vertebral levels, segmental pedicle screw fixation from the upper-instrumented vertebra to the lower instrumented vertebra (LIV), and complete 2-year follow-up data. Patients were excluded if they lacked appropriate radiographs or had a syndromic, neuromuscular, or other pathological condition.
Data Collection and Assessment of Radiographs and Health-Related Quality of Life
We collected the following demographic and clinical data for each patient: age, sex, comorbidities (history of diabetes mellitus, cancer, congestive heart failure, hypertension requiring medication, cerebrovascular accident with or without neurological deficit, obstructive or other chronic pulmonary disease, conjunctive tissue disease, percutaneous coronary intervention, prior cardiac surgery, angina, transient ischemic attack, myocardial infarction, peripheral vascular disease, impaired sensorium, dementia, kidney disease, leukemia, lymphoma, liver disease, acquired immune deficiency syndrome or acquired immunodeficiency syndrome), body mass index, bone mineral density (BMD), and history of spine surgery. Frailty and comorbidities were assessed with the Modified Frailty Index (mFI) and Charlson Comorbidity Index (CCI).8,9,18,20–22 Patients were categorized as robust (mFI = 0), prefrail (mFI < 0.21), or frail (mFI > 0.21) based on their physical activity and comorbidities.
Surgical data collected for each patient included the Schwab-Scoliosis Research Society (SRS) ASD classification and subcategory,23 application of pedicle subtraction osteotomy, upper-instrumented vertebra and LIV levels, and number of fused vertebrae. BMD was calculated from dual-x ray absorptiometry scores of the right femoral neck. We used full-length standing whole-spine radiographs obtained at baseline and at the 6-week and 2-year follow-up appointments to determine the Cobb angle, C7SVA, T4-T12 thoracic kyphosis, T12-sacrum lumbar lordosis, sacral slope, pelvic tilt, pelvic incidence, T1 pelvic angle, and spinopelvic alignment (pelvic incidence −lumbar lordosis). As a health-related quality of life (HRQoL) surrogate, we used results from the Oswestry Disability Index and SRS-22r questionnaire (SRS-22r), obtained at baseline and at 2 years after surgery.
Of 249 candidates, 240 had complete demographic and radiographic data that would capture any postoperative complications. Seven patients were lost during follow-up and two patients died during follow-up for reasons unrelated to the surgery (cancer and unknown reason), and therefore were excluded from the analysis. Thus, the study included 240 patients (92% women; age 58.4 ± 16.7 years [22–79] years; mFI 0.07 ± 0.11 [0.00–0.64]; BMD T-score −1.0 ± 0.9 [−3.2–2.3], and 9.6 ± 2.8 [5–19] fused levels).
Inclusion of Complications
We analyzed intraoperative and postoperative complications during the 2-year follow-up period based on patient charts and radiographic findings. Based on previous reports, surgical complications were categorized as neurological, implant-related (proximal and distal junctional kyphosis, rod breakage, pseudoarthrosis, implant dislodgement, screw breakage, and others), surgical-site infection, other infection (urinary tract infection and others), excessive bleeding (>2000 mL), delirium, cardiopulmonary (hemodynamic instability, myocardial infarction, deep venous thrombosis, pulmonary embolisms, thoracic atelectasis, congestive heart failure, and others), gastrointestinal (ileus, cholecystitis), or renal (acute renal failure).11,24 Complication severity was assessed by the Clavien–Dindo (C–D) classification.25
Data Preparation and Evaluation of Frailty Status
Patients were categorized by frailty and treatment status as robust (R), frail or prefrail with good control (G), defined as a treatment regimen following the appropriate guidelines for each mFI factor (Supplemental Table 1, http://links.lww.com/BRS/B399), or poorly controlled frail or pre-frail (PC).26–31 Relationships between the treatment status for frailty and the development of complications were investigated by univariable and multivariable logistic regression analyses.
Differences between the R, G, and PC groups were compared by chi-square test, analysis of variance, or Tukey-honestly significant difference (HSD) test as appropriate. Changes between baseline and postoperative values were analyzed by paired t test. To compare the odds ratio (OR) of surgical complications between the R, G, and PC groups, we created a multivariable logistic regression model to evaluate age- and sex-adjusted associations and to predict the likelihood of developing surgical complications. A P value less than .05 with a confidence interval of 95% was considered statistically significant. Data were analyzed with the Statistical Package for the Social Sciences (SPSS statistics version 25.0, IBM Corp., Armonk, NY) and Stata14 (Stata Corporation, College Station, TX).
Characteristics of the R, G, and P Groups
Patient characteristics are shown in Table 1. Of the 240 patients, 81 (34%) were categorized as prefrail and 17 (7%) as frail. Among the 98 frail or prefrail patients, frailty was under good control in 71 patients (72%, G group) and poor control in 27 patients (28%, PC group). Baseline values in the G and P groups were comparable for age, body mass index, dual-x ray absorptiometry (T-score), and Charlson Comorbidity Index; these values were significantly worse in the G and P groups than in the R group (Table 1). Time in surgery was similar in the G and PC groups but was significantly shorter in the R group (Table 1). However, the estimated blood loss was similar in the three groups.
Comparison of Radiographic Parameters
The baseline sagittal-plane deformity was significantly worse in the G group than in the R group (Table 2). The postoperative C7SVA was worse in the G and PC groups than in the R group (Table 2). However, sagittal alignment was similar in the G and PC groups at the 2-year follow-up (Table 2).
Comparison of Complications
Major complications developed in 107 of 240 patients (45%) within 2 years of ASD surgery; 54 (50%) occurred within 30 days of surgery (perioperative complications) and the remaining 53 (50%) occurred after 30 days but within 2 years. The rate of both perioperative and 2-year complications increased as the severity of frailty increased (Figure 1A and B). The perioperative complication rates and 2-year overall complication rates were similar in the G and PC groups but were significantly lower in the R group (Figure 1C and D). After adjusted the age and sex of these groups, OR for 2-year complications or perioperative complications were not different between G and PC group when referencing the G group (2-year complication; OR 1.26 [0.49–3.21]; P = 0.630, preoperative complication; OR 1.19 [0.46–3.11]; P = 0.717, Table 3). The incidence of C–D 2 or higher or C–D 3 or higher complication were both similar in the GC and PC groups (C–D >2, G 34% vs. PC 33%; C–D >3, G 25% vs. PC 19%) but were significantly lower than those in the R group (11% and 10% respectively; P < 0.01; Figures 2 and 3A and B). The adjusted OR for complications with a severity of C–D 2 or higher or C–D 3 or higher did not differ in the PC group (C–D >2, OR 0.98 [0.38–2.55], P = 0.970; C–D >3, OR 0.67 [0.22–2.07], P = 0.490). However, the OR for complications in the R group was significantly lower than in the GC group for any time period (Table 3).
Clinical Outcomes in the R, G, and PC Groups
Regardless of the status of frailty treatment, clinical outcomes were similar in the G and PC groups at baseline and 2 years after surgery (Table 4). The SRS22 function and total scores were significantly lower in the G and PC groups than in the R group, both at baseline and 2 years after surgery (Table 4).
Several demographic, radiographic, and surgical factors have been reported as risk factors for complications in ASD surgery.1–12 Relationships between HRQoL and comorbidities in adults with chronic conditions are widely recognized.7–12 Recent studies have described relationships between comorbidities and inferior clinical outcomes in ASD surgery.32 Typically, the presence of severe comorbidities (i.e., chronic obstructive pulmonary disease, severe cardiovascular disease, cerebrovascular disease with neurological deficit, etc.) influences HRQoL, as measured by various protocols and scales, in ASD surgery.11,32
Frailty is frequently observed clinically in older adults. Frailty increases the risk of poor health outcomes, including falls, incidence of disability, prolonged hospitalization, and mortality.13,14 Frailty is reported to be a significant risk factor for postsurgical complications and the need for extended care.7–10,14 Afilalo et al33 reported that frailty more than doubles the risk of morbidity and mortality in general surgery and under cardiovascular conditions. Recent studies have indicated that frailty increases the risk for perioperative complications after ASD surgery.7–10 Rothrock et al18 reported that frail patients are less likely than prefrail and robust patients to recover to cognitive baseline after elective spine surgery. Miller et al34 described associations between frailty and inferior clinical outcomes using many common quality and value metrics, including an increased risk of major complications. Yagi et al7 reported that mFI is an independent risk factor for 2-year complications in ASD surgery. After reviewing 1001 patients with ASD from the American College of Surgeons National Surgical Quality Improvement Program database, Leven et al11 reported that frailty is an independent predictor of postoperative complications, mortality, and reoperation in patients undergoing surgery for ASD.
It can be said that frailty is not simply the coexistence of many comorbidities, but is rather a state of increased vulnerability resulting from an aging-related decline in reserves and function. The mFI is currently the most common and most widely used method for measuring the severity of frailty, and most studies have used the mFI to determine predictors for adverse postoperative outcomes.7–12 However, the mFI is an index based primarily on the patient's medical history and activity and does not reflect the treatment status of each comorbidity. In the present study, we first investigated how the status of treatment for frailty affected the complication rates and clinical outcomes in ASD surgery. The clinical outcomes and complication rates were similar in the G and PC groups, which clearly indicated that even when prefrailty or frailty and its comorbidities are treated following the appropriate guidelines for each mFI factor, the clinical outcomes and complication rates for ASD surgery are not improved.
Possible explanations for the lack of association between treatment for frailty and complications and clinical outcomes in ASD surgery include the invasiveness of spinal surgery for ASD, which typically requires large dissection, long-segment spinal fusion, osteotomy, blood transfusion, and extended hospitalization. Thus, corrective surgery for ASD provides favorable outcomes but also poses a substantial risk for major complications and poor outcomes in both the perioperative and long-term postoperative periods.2,24,32 Yagi et al7 reported inferior clinical outcomes and higher complication rates for frail middle-aged and elderly patients who underwent surgery for ASD, whereas no difference was observed between robust, prefrail, and frail patients who underwent laminectomy, posterior lumbar interbody fusion for degenerative lumbar spondylolisthesis, or laminoplasty for cervical spondylotic myelopathy. Taken together, our findings indicate that frail patients may not fully recover after ASD or other highly invasive surgeries, even when frailty is treated according to the relevant guidelines for each mFI factor. It is also possible that associations between frailty and outcomes were confounded by differences in the degree of invasiveness between individual patients. Although indicators of surgical invasiveness (number of levels fused, time in surgery, and EB) were similar in the G and P groups, the complication rates might have been affected by variables that were not measured in this study.
This study was limited by its retrospective design, which precludes drawing firm conclusions about the effect of frailty treatment status on complications in ASD surgery. A prospective study by Smith et al32 reported higher complication rates for ASD surgery than those observed in the present study. However, we enrolled consecutive patients from a prospective database and analyzed the patients retrospectively, which is the most common method for investigating how a factor affects outcomes and complications in clinical research when randomized controlled trials are not possible. Our study is also limited by the lack of consensus criteria for treating frailty and prefrailty. In the present study, we evaluated treatment for frailty according to the appropriate guidelines for each mFI factor. However, treatment guidelines are evidence-based recommendations for clinicians caring for patients with specific conditions, and these guidelines aim to provide effective intervention for the specific condition rather than addressing how interventions might affect other conditions, surgical complications, HRQoL, and so forth. Therefore, it might be necessary to reconsider whether the specific comorbidity cut-off values offered in these guidelines are appropriate for analyzing associations between frailty treatment status and complications in ASD surgery.
Despite these limitations, the present study indicates that the status of treatment for frailty did not affect the risk of complications in ASD surgery. Careful patient selection and preoperative planning that takes patient frailty along with demographic and radiographic factors into account may decrease surgical complications and improve clinical outcomes for corrective surgery for ASD. Surgeons should routinely evaluate and consider frailty when contemplating surgical correction of ASD and when informing patients of possible complications.
Our study demonstrated that treatment for frailty did not improve the risk of complications in surgery for ASD surgery. Frailty is a risk factor for inferior clinical outcomes and high rates of operative complications in ASD surgery regardless of whether the patient is being treated for frailty. Surgeons should routinely evaluate and consider frailty when contemplating surgical correction of ASD and when informing patients of possible complications.Key PointsA retrospective multicenter database review of 240 consecutive patients at least 21 years of age (range 58 ± 17) who underwent surgery for ASD and were followed at least 2 years.Patients were categorized as robust (R group), prefrail, or frail based on the mFI; prefrail and frail patients were divided by good control of frailty (G group), defined as treatment following the appropriate guidelines for each mFI factor, or poorly controlled frailty (PC group).The age- and sex-adjusted OR for 2-year complications was not different in the P group when the G group was referenced (OR 1.3 [0.5–3.2], P = 0.63).Regardless of its treatment status, frailty increases the risk of complications and inferior clinical outcomes in ASD surgery. Surgeons should routinely evaluate frailty and inform patients of frailty-related risks when considering surgery for ASD.
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