Comparative Performance of the ISSG-Surgical Invasiveness Index and the ESSG-Adult Deformity Surgery Complexity Index: A Retrospective Analysis.

Retrospective single-center cohort study.To compare the predictive performance of the International Spine Study Group (ISSG) - Surgical Invasiveness Index (SII) and the European Spine Study Group (ESSG) - Adult Deformity Surgery Complexity Index (ADSCI) for outcomes after adult spinal deformity (ASD) surgery.In 2018, the ISSG and ESSG developed their surgical complexity indices specific to surgical treatment of ASD. However, no study has compared these two indices against one another, hindering surgeon decision-making.A retrospective single-center study of patients who underwent ASD surgery with complete baseline and two-year follow-up data were assessed via the ISSG-SII and the ESSG-ADSCI. The primary outcome measure was a composite binary outcome of any postoperative surgical or medical complications. Secondary outcomes included intraoperative estimated blood loss (EBL), operative time, length of stay (LOS), intraoperative complications, reoperations, and specific complications. We used multivariable logistic and linear regression to compare indices.A total of 586 patients who underwent surgery for ASD (mean age: 57.6 y; 76.5% female; BMI: 27.1 kg/m²; mean ISSG-SII score: 94.7±36.4; mean ESSG-ADSCI score: 21.9±6.6) met inclusion criteria. After controlling for age, gender, body mass index, and Charlson Comorbidity Index, the ISSG-SII (aOR: 1.007; P=0.019) and the ESSG-ADSCI (aOR: 1.031; P=0.046) were statistically significant but weak predictors of any surgical or medical complication. Similar weak results were observed for EBL, operative time, and LOS were seen (all unstandardized ß<0.300). Similar poor performance was seen for intraoperative complications, mechanical complications, reoperation, distal junctional kyphosis, coronal imbalance, sagittal imbalance, or pseudoarthrosis.ISSG-SII and ESSG-ADSCI demonstrated comparable but limited predictive ability across multiple surgical and postoperative outcomes among patients who underwent ASD surgery. While the results support practical utility, independent calibration is necessary prior to clinical application.

Duke Scholars

Author Peter Passias Orthopaedic Surgery