Impact of Lower Thoracic vs. Upper Lumbar UIV in MIS Correction of Adult Spinal Deformity

Presented at SMISS Annual Forum 2018
By Robert Eastlack MD
With Pierce Nunley MD, Juan S. Uribe MD, FACS, Paul Park MD, Stacie Tran MPH, Michael Wang MD, Khoi Than MD, David O Okonkwo , Adam Kanter MD, Neel Anand MD, Richard Fessler MD, Kai Ming Fu MD, Dean Chou MD, Praveen Mummaneni MD, Gregory M. Mundis MD, International Spine Study Group MD,

Disclosures: Robert Eastlack MD A; Nuvasive. B; Aesculap, Alphatec Spine, K2M, Nuvasive, Seaspine, Stryker, Titan. D; Alphatec, Carevature, DiFusion, Invuity, Nuvasive, Spine Innovations. F; Globus Medical Pierce Nunley MD B; K2M. C; K2M, LDR. D; Amedica, Paradigm, Spineology. F; K2M, LDR, Juan Uribe MD, FACS A; Nuvasive. B; Nuvasive. C; Nuvasive. D; Nuvasive. F; Nuvasive, Paul Park MD B; Biomet, Globus, Medtronic, Nuvasive. F; Globus, Stacie Tran MPH None, Michael Wang MD B; Aesculap, Depuy, JoiMax, K2M. C; Depuy. D; Spinicity. F; Depuy, Khoi Than MD None, David O Okonkwo None, Adam Kanter MD A; Nuvasive. F; Nuvasive, Zimmer Biomet, Neel Anand MD B; Medtronic. C; Globus, Medtronic. D; Atlas Spine, Globus, GYS Tech, Medtronic, Paradigm, Theracell. F; Globus, Medtronic, Richard Fessler MD B; Depuy. F; Depuy, Medtronic, Stryker, Kai Ming Fu MD Medtronic. C; Synthes, Dean Chou MD None, Praveen Mummaneni MD B; Depuy. C; Globus. D; Spinicity. F; Depuy., Gregory Mundis MD A; ISSGF, Nuvasive. B; K2M, Medicrea, Misonix, Nuvasive. C; K2M, Nuvasive. F; Nuvasive., International Spine Study Group MD A; Biomet, Depuy, K2M, Medtronic, Nuvasive, Orthofix, Stryker.,

Introduction:

Selecting the UIV in the region of the thoracolumbar junction when performing open deformity correction has traditionally defaulted to the lower thoracic (LT) spine. However, because of the more significant use of interbody cages/support and/or the preservation of posterior spinal musculature when utilizing MIS for ASD correction, there may be greater feasibility in choosing the upper lumbar (UL) region for the UIV.

Aims/Objectives:

Determine whether clinical and radiographic outcomes differ when the upper instrumented vertebra (UIV) level crosses the thoracolumbar junction in MIS correction of adult spinal deformity.

Methods:

Multicenter retrospective review of an adult spinal deformity database. Inclusion criteria were age ≥18 years, and one of the following: coronal cobb>20°, SVA>5cm, PT>20°, pelvic incidence-lumbar lordosis >10°. Patients were treated with circumferential or hybrid minimally invasive techniques at ≥3 spinal levels, and had 2-year minimum follow-up. They were then divided by UIV location of L1-2 (UL) or T10-12 (LT).

Results:

112 patients met inclusion criteria (68 LT and 46 UL). The UL group was older (67.5 vs. 62.3; p=0.015). Average follow-up was 40 months in both groups. The number of interbody fusions were similar between groups (3.9 in UL and LT; p=0.78), and percentage of patients with fixation crossing the lumbosacral junction was similar (70.6% vs. 67.4%, p=0.717). Preoperative spinopelvic parameters were similar, except for sacral slope, which was higher in the UL group (30.5 vs. 26.5; p=<0.001). OR time (460min vs. 587min; p=0.011) and EBL (594.0 vs. 1293.3; p=0.001) were both lower with UL vs. LT. Postop LL (41.4 vs. 37.3; p=0.01) and Cobb change (-23.2 vs. -9.6; p<0.001) were greater in the LT group, but the remainder of postop spinopelvic parameters and changes, as well as ODI (32.1 UL vs. 32.3 LT; p=0.96) were similar. Length of stay was similar between groups (8.4 UL vs. 8.9 LT; p=0.511). Reoperation rates were lower in the UL group (17.4% vs. 36.8%; p=0.025), largely as a result of less frequent radiographic failures (UL=10.9% vs. LT=26.5%; p=0.042); Overall complication rates were not different (60.3% vs. 43.5%; p=0.077).

Conclusions:

Choosing an upper lumbar vertebra for UIV when correcting ASD with MIS techniques results in lower reoperation rates than when extending fixation to the lower thoracic region. It was also associated with shorter operative times and less EBL. Extending fixation to the LT was associated with slightly higher LL and greater change in coronal Cobb, but this was not associated with better clinical outcomes.