Incremental benefits of circumferential minimally invasive surgery for increasingly frail patients with adult spinal deformity
Authors: Passias Peter G. , Tretiakov Peter S. , Nunley Pierce D. , Wang Michael Y. , Park Paul , Kanter Adam S. , Okonkwo David O. , Eastlack Robert K. , Mundis Gregory M. , Chou Dean , Agarwal Nitin , Fessler Richard G. , Uribe Juan S. , Anand Neel , Than Khoi D. , Brusko Gregory , Fu Kai-Ming , Turner Jay D. , Le Vivian P. , Line Breton G. , Ames Christopher P. , Smith Justin S. , Shaffrey Christopher I. , Hart Robert A. , Burton Douglas , Lafage Renaud , Lafage Virginie , Schwab Frank , Bess Shay , Mummaneni Praveen V. 
Published: April 2023

OBJECTIVE
Circumferential minimally invasive surgery (cMIS) may provide incremental benefits compared with open surgery for patients with increasing frailty status by decreasing peri- and postoperative complications.

METHODS
Operative patients with adult spinal deformity (ASD) ≥ 18 years old with baseline and 2-year postoperative data were assessed. With propensity score matching, patients who underwent cMIS (cMIS group) were matched with similar patients who underwent open surgery (open group) based on baseline BMI, C7–S1 sagittal vertical axis, pelvic incidence to lumbar lordosis mismatch, and S1 pelvic tilt. The Passias modified ASD frailty index (mASD-FI) was used to determine patient frailty stratification as not frail, frail, or severely frail. Baseline and postoperative factors were assessed using two-way analysis of covariance (ANCOVA) and multivariate ANCOVA while controlling for baseline age, Charlson Comorbidity Index (CCI) score, and number of levels fused.

RESULTS
After propensity score matching, 170 ASD patients (mean age 62.71 ± 13.64 years, 75.0% female, mean BMI 29.25 ± 6.60 kg/m2) were included, split evenly between the cMIS and open groups. Surgically, patients in the open group had higher numbers of posterior levels fused (p = 0.021) and were more likely to undergo three-column osteotomies (p > 0.05). Perioperatively, cMIS patients had lower intraoperative blood loss and decreased use of cell saver across frailty groups (with adjustment for baseline age, CCI score, and levels fused), as well as fewer perioperative complications (p < 0.001). Adjusted analysis also revealed that compared to open patients, increasingly frail patients in the cMIS group were also more likely to demonstrate greater improvement in 1- and 2-year postoperative scores for the Oswestry Disability Index, SRS-36 (total), EQ-5D and SF-36 (all p < 0.05). With regard to postoperative complications, increasingly frail patients in the cMIS group were also noted to experience significantly fewer complications overall (p = 0.036) and fewer major intraoperative complications (p = 0.039). The cMIS patients were also less likely to need a reoperation than their open group counterparts (p = 0.043).

CONCLUSIONS
Surgery performed with a cMIS technique may offer acceptable outcomes, with diminishment of perioperative complications and mitigation of catastrophic outcomes, in increasingly frail patients who may not be candidates for surgery using traditional open techniques. However, further studies should be performed to investigate the long-term impact of less optimal alignment in this population.