Lightning Podiums: Adult Spinal Deformity - Room 801A

Presented by: C. Varlotta

Author(s):

P. Zhou(1), J. Moon(1), J. Tishelman(1), C. Varlotta(1), N. Frangella(1), T. Errico(1), T. Protopsaltis(1), P. Passias(1), A. Buckland(1)

(1) New York University Langone Orthopedic Hospital, Division of Spinal Surgery, New York, NY, United States

Abstract

Introduction: Transitional lumbosacral vertebrae (TLSV) are segments that can have the characteristics of both lumbar and sacral vertebrae. Difficulties in identification of the S1 endplate may come from nomenclature, number of lumbar vertebrae, sacra, morphology, and may influence interpretation and consistency of spinal alignment parameters. The aim of this study was to better understand the variability in selection of the sacral endplate in TLSV and its impact on pelvic, regional and global alignment.

Methods: Retrospective radiographic review. Radiographic review of a retrospective single institutional spinal surgery database was performed. Patients were included if they had 90 cm spinal AP and lateral radiographs, and TLSV as defined by the presence of a true bony union between a transverse process and the sacrum (Types III and IV - Castellvi et al. 1984). Exclusion criteria included poor visualization of TLSV or femoral heads, congenital abnormalities, spondylolisthesis, >Grade 1 or previous interbody fusion or osteotomy at the TLSV. Radiographic measurements were performed twice with the sacral endplate at the upper and lower option. A paired t-test assessed difference between different selection groups.

Results: Of 1869 patients, 70 (3.7%) were found to have TLSV on radiographic imaging. Of those, 58 (82.9%) had lumbarized sacral segments while 12 (17.1%) had sacralized lumbar segments. 32 (45.78%) of the patients were female and the mean age was 52.5 years. T1SPi (Mean: -1.77°) and TK (Mean: 34.86°) did not vary as a result of altering sacral endplate selection of the TLSV. Selection of the lower TLSV as the sacral endplate resulted in an increase in all pelvic parameters (PI: 66.8° vs 44.3°, PT: 25.1°; vs 12.7° and SS: 41.6° vs 31.6°), regional lumbar parameters (LL: -54.1° vs 44.0°, PI-LL: 12.7° vs 0.3°), and global parameters (SVA: 46.1 mm vs 28.3 mm, TPA: 23.3° vs 10.8°) as compared to selecting the upper TLSV. All mean differences between radiographic parameters were found to be statistically significant (p< 0.001).

Conclusions: Variation in sacral endplate selection in TLSV significantly effects spinal alignment parameter measurement. A standardized method for measuring TLSV is needed to reduce measurement error and ultimately allow more accurate understanding of alignment targets in patients with TLSV.