New ASD frailty index links severe frailty to increased length of stay and major complication rate

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FrailtyA new model for measuring frailty in adult spinal deformity (ASD) patients has been assessed by the International Spine Study Group (ISSG) for its ability to predict both perioperative and postoperative complications. The team found an association between frailty and both increased length of stay in hospitals, and increased major complications rate. A second study—from both the ISSG and the AOSpine Knowledge Forum Group—came to similar conclusions, especially for severely frail patients, when researchers applied the index to the complex deformity patients catalogued in the Scoli-Risk-1 database. Both studies were presented at the Scoliosis Research Society Annual Meeting (SRS; 21–24 September, Prague, Czech Republic).

Frailty as an indicator of risk in surgery is an increasingly prominent area of research. An article recently published in the Annals of Thoracic Surgery has suggested that identifying frailty in older patients may help to improve survival rates, as well as other outcomes, following surgery. “Patients with frail health have less ability to overcome stressors such as illness, falls, and injury, and have a higher risk of adverse effects from medications, procedures, and surgery,” said co-author Angela K Beckert, Medical College of Wisconsin, Milwaukee, USA, in a press release. In Beckert and team’s study of 125 elderly patients considered candidates for major thoracic surgery, the majority (68.8%) were deemed either “pre-frail” or “frail” by a frailty screening which identified characteristics such as unintentional weight gain and weakness according to grip strength. “Knowing what these factors are can help physicians, patients, and the patients’ families better understand the risks and may motivate them to participate in activities that reduce their risks,” said Mark K Ferguson, The University of Chicago Medicine, Chicago, USA. With the rapid growth of the elderly population across much of the globe, more and more elderly patients are expected to undergo surgery. For the spinal field, this growing burden of disease is of particular concern. In the case of adult spinal deformity, ISSG researchers stated that “the relationship between frailty and complication rate following adult spinal deformity is unclear.”

The first ISSG study of the recently-validated Adult Spinal Deformity-Frailty Index (ASD-FI) was a retrospective review of a prospective multicentre database. Described by authors as a “valuable tool for risk stratification in adult spinal deformity patients”, the index was predicted to link frailty to prolonged hospital length of stay and increased risk of complication.

The study population was made up of adult spinal deformity patients, catalogued in a prospective registry. Four hundred and seventeen participants with a minimum of two-years’ follow-up were included in this review (n=450), which divided the population according to degree of frailty. A score on the ASD-FI of below 0.3 deemed a participant “not frail” (n=171), whilst a score between 0.3 and 0.5 deemed them “frail” (n=162). Patients with scores higher than 0.5 were considered “severely frail” (n=84). The average ASD-FI score was 0.34, with a range between 0 and 0.8.

The researchers then “performed a multivariate logistic regression to determine the relationship between ASD-F1 cohorts, incidence of major complications and hospital length of stay”. Their regression model adjusted results to compensate for covariates before and during surgery, including blood loss and operative time.

The average length of stay was significantly greater for both the frail (2.6 days, range 0.95–4.3, p<0.01) and severely frail patients (6.4 days, range 4.2–8.7, p<0.001), in comparison to those deemed non-frail. When the researchers calculated the likelihood of experiencing a major complication during or after surgery, they found that frail patients were 9.4 times more likely than non-frail to develop a complication, with severely frail patients 14.5 times as likely.

Medical complications, specifically, were 3.9 times more likely to happen in frail than non-frail patents, and 14.6 times more likely for the severely frail. Surgical complication rates were less starkly varied, with frail patients experiencing an odds ratio of 1.8 compared to non-frail patients, and severely frail patients experiencing an odds ratio of 2.1. For severely frail patients, the researchers also discovered an odds ratio of 4.4 for the development of proximal junctional kyphosis, and 5.1 for the development of a wound infection, when compared to non-frail patients.

Given these strong results, the team concluded that the ASD-FI “could be applied to improve the accuracy of preoperative risk stratification.” This, they claim, “would assist with surgical planning and patient counselling.”

The second study of the ASD-FI, performed by both the ISSG and the AOSpine Knowledge Forum Deformity, evaluated the index in a complicated patient population, suffering from severe forms of adult spinal deformity. The researchers used participants in the Scoli-Risk-1 database—a multicentre, international, prospective registry of patients with deformity including Cobb curvature of greater than 80 degrees, or congenital deformity. These patients also underwent complex procedures, with 206 out of 267 having three-column osteotomies.

Using a similar study design, patients with at least two years’ worth of clinical and radiographic follow-up were assessed for frailty according to the ASD-FI. The same parameters were used to distinguish between non-frail (105, 39%), frail (103, 39%) and severely frail patients (59, 22%). In this study, the average ASD-FI score was 0.32, with a range from 0 to 0.72. Multivariate logistic analysis was performed to determine any links between frailty, length of stay, and major complication rate.

The percentage of patients who experienced complications was starkly different between the groups. Sixty-five point seven per cent of non-frail patients experienced a complication, with 27.6% experiencing a major complication. Seventy-seven point seven per cent of frail patients, however, experienced a complication, while 36.9% developed a major complication. Severely frail patients, as expected, experienced complications most regularly, with 91.5% of patients experiencing any complication, and 57.6% experiencing major complication. The odds ratios for major complication before logistic regression was 3.6 [1.8–7] (p<0.001) for severely frail in comparison to non-frail patients.

When results were adjusted according to preoperative co-variates, frailty was associated with increased odds ratios for major complications, with ratios of 1.5 (0.8–2.8, p=0.2) for frail patients and 4.1 (1.9–9.2, p<0.001) for the severely frail. After adjustment, length of stay was significantly (p<0.05) increased for severely frail patients, who experienced 18.9% (1.4–39.4) more time in hospital than non-frail patients.

The authors of this study concluded that “given this validation of the index in even the most complex deformity patients, the ASD-FI could be applied to improve the accuracy of preoperative risk stratification.”

Commenting on his work in the Annals of Thoracic Surgery, Ferguson explained, “There is an increasing awareness of the frailty problem among surgeons…We anticipate that screening efforts will expand substantially in the near future.”

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