Maintenance of Alignment Following Adult Spinal Deformity Surgery: A Comparative Analysis of the Impact of Utilization of Supplemental Rods Relative to Interbody Placement

Introduction: There is a paucity of literature on whether multiple lumbar interbody fusions or supplemental rod constructs achieve superior maintenance of lordosis and/or superior surgical outcomes.

Methods: Operative ASD patients (scoliosis >20º, SVA>5cm, PT>25º, or TK>60º) with fusion UIV at or above L1 and fusion to pelvis with available baseline (BL) and 2-year (2Y) radiographic and HRQL data were included. Patients were divided into 2 groups, 1) those who had a supplemental rod construct (SUP) crossing at least 4 levels of the lumbar spine with no lumbar interbody fusion (LIBF), and 2) greater than or equal to 4 LIBF with no SUP. High loss of lumbar lordosis (HL) was defined as 1STD above the mean change in lordosis from post-op to 2Y.

Results: Out of 381 ASD patients who met inclusion criteria, 53 were analyzed: 24 with LIBF, and 29 with SUPs. At BL patients with a SUP had a greater SVA (9.3cm vs 7cm), p< 0.05). SUP patients had higher rates of prior fusion (82% vs 48%), and greater usage of 3CO (40% vs 3%, both p<.05). No differences in age, gender, BMI, CCI, frailty, or BL HRQLs. ANCOVA adjusting for BL deformity, 3CO, and revision status found SUP patients had a lower operative time (341min vs 663min, p<.001), crystalloid usage (3600 vs 6300) and LOS (7.4 vs 10.3 days). LIBF had greater usage of BMP2 (30% vs 0%, all p<.05. LIBF patients had a comparable degree of LL correction (18 vs 22) and greater HL (19% vs 4%). LIBF patients had higher rates of implant failure (42% vs 14%), rod breakage (21% vs 4%), rod dislocation (13% vs 0%) and overall mechanical complications (71% vs 35%, all p<.05). Rates of PJF trended higher (25% vs 10%). At 2Y, SUP patients had comparable HRQLs and trended higher for 6W GAP Proportionality (35% vs 21%).

Conclusion : The use of supplemental rods relative to the performance of multiple lumbar interbodies appear to better maintain alignment and substantially lower rates of rod breakage, implant failure, and overall mechanical complications by two years and beyond.