**1. Introduction**

The social burden caused by low back pain (LBP) is relevant, having a first-ever episode incidence of 15% and an 80% recurrence rate within a year [1]. This percentage increases in patients affected by adult spine deformity [2] and various studies showed that this condition has a negative impact on the patients' quality of life [3,4]. Surgical deformity correction involves complex procedures; given the advances in surgical and anesthesiological techniques, it is now possible to perform surgery in patients at an older age and with more comorbidities [5–8]. So, disability and pain levels play a decisive role in the assessment of a patient and in the decision-making process [9]. However, the postoperative motion restriction following fusion of the lumbar spine should be considered when indicating surgical managemen<sup>t</sup> to ensure that the benefits of the surgery outweigh the limitations [10].

Patient-reported outcome measures (PROMs) are used to obtain a more complete overview of a patient's status, as they allow to match objective informations such as radiographic findings with subjective data regarding different aspects of the patient's

**Citation:** Baroncini, A.; Migliorini, F.; Langella, F.; Barletta, P.; Trobisch, P.; Cecchinato, R.; Damilano, M.; Quarto, E.; Lamartina, C.; Berjano, P. Perioperative Predictive Factors for Positive Outcomes in Spine Fusion for Adult Deformity Correction. *J. Clin. Med.* **2022**, *11*, 144. https:// doi.org/10.3390/jcm11010144

Academic Editors: Takashi Hirai, Hiroaki Nakashima, Masayuki Miyagi, Shinji Takahashi and Masashi Uehara

Received: 28 November 2021 Accepted: 26 December 2021 Published: 28 December 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

quality of life [11]. In particular, the Oswestry disability index (ODI) and the visual analogic scale (VAS) are two parameters widely used for pre- and postoperative assessment of patients undergoing spine surgery [12,13].

The effects of the correction of sagittal and coronal parameters on disability and pain levels have been evaluated in multiple studies [14–17]. However, the effects of demographic and perioperative data on the postoperative outcome has not ye<sup>t</sup> been thoroughly investigated, and patients with a low risk of a poor clinical outcome have not ye<sup>t</sup> been characterized [18]. Thus, the aim of this study was to analyze the demographic and perioperative data of adult spine deformity patients undergoing long fusion involving the lumbar spine, in order to seek possible associations between these parameters and levels of disability (ODI) and pain (VAS back and leg) at the one- and two-year follow-up.

#### **2. Materials and Methods**

#### *2.1. Patient Recruitment*

The present retrospective study was conducted according to the Strengthening the Reporting of Observational Studies in Epidemiology: the STROBE Statement [19].

All patients who underwent spine fusion at IRCCS Istituto Ortopedico Galeazzi (Milano, Italy) between January 2016 and June 2019 were retrospectively screened for inclusion on the local spine registry using the ICD (International Classification of Diseases) diagnosis and procedure codes listed in Table 1. The use of ICD codes for diagnosis and procedure allows to retrieve data from the registry, but also offers an internationally acknowledged key to replicate data extraction, if necessary. Inclusion criteria for the current study were age ≥ 18, diagnosis of adult spine deformity, and fusion of at least four segments—at least three of which in the lumbar spine. Patients who did not have an ODI and/or VAS preoperatively and at the one- or two-year follow-up were not eligible for the study.

**Table 1.** List of all ICD diagnosis and procedure codes used for data extraction from the local spine registry.


ICD, International Classification of Diseases.

#### *2.2. Outcomes of Interest*

We analyzed the effects of demographic and perioperative parameters on ODI and VAS over time, as well as the mutual association between ODI and VAS at different followups. Furthermore, question n. 11 of the COME back questionnaire (CB11) [20] was used to identify whether patients felt overall that surgery had helped or not (0 = helped a lot, 4 = made things worse). Demographic parameters included age, sex, body mass index (BMI), and American Society of Anaesthesiologists (ASA) score. The level of the upper and lowest instrumented vertebra (UIV and LIV, respectively) was analyzed. Length of surgery, estimated blood loss (EBL), and length of hospital stay were also considered.

#### *2.3. Statistical Analysis*

For the statistical analysis, STATA software (StataCorp, College Station, TX, USA) was used. Continuous variables are expressed as mean ± standard deviation. Comparisons between continuous variables across the follow-ups were assessed through the mean difference and t-test, with values of *p* < 0.05 considered statistically significant. A multivariate diagnostic through the Pearson product-moment correlation coefficient (*r*) was performed to investigate potential correlations between continuous variables. According to the Cauchy–Schwarz equation of inequality, the final effect can score between +1 (positive linear correlation) and −1 (negative linear correlation). Values of 0.1 > |*r*| < 0.3, 0.3 < |*r*| < 0.5, and |*r*| > 0.5 indicate weak, moderate, and strong association, respectively. The test of overall significance was performed through the χ2 test, with values of *p* > 0.05 considered statistically significant.
