126. Enhanced utility with greater number of levels treated for patient-specific, pre-contoured rods in posterior cervical fusion

BACKGROUND CONTEXT Patient-specific, pre-contoured rods are increasingly used in the surgical treatment of spinal pathologies. Previous studies show that pre-contoured rods help to achieve desired postoperative alignment goals, though it is unclear whether these benefits differ by fusion length. PURPOSE Assess how preoperative planning and patient-specific rods affect the outcomes of patients undergoing posterior cervical fusion surgery. STUDY DESIGN/SETTING Retrospective review of single-center cases of multilevel posterior cervical surgeries from 2014-2018. PATIENT SAMPLE This study included 65 patients. OUTCOME MEASURES Sagittal alignment: cervical sagittal vertical axis (cSVA), cervical lordosis (CL), T1 Slope (T1S) minus CL (TS-CL), and cervical-thoracic pelvic angle (CTPA). METHODS Patients undergoing posterior cervical fusion with available pre- and postop (3-month, 6-month, or 1-year) cervical radiographs were stratified: those whose surgeries involved preoperative planning and patient-specific, pre-contoured rods (PLAN), and those whose surgeries did not (NON). Independent samples t-tests assessed differences between PLAN and NON groups in alignment, and pre- to postop changes in alignment. Secondary analysis assessed differences in alignment between PLAN and NON groups for patients with lower-most instrumented vertebrae (LIV) above C7-T1, and below. RESULTS Included: 65 patients (55.1±9.9 years, 61% female) undergoing posterior cervical fusion (6.2±3.7 levels). Mean follow-up was 8.4±4.1 months. By group, 47.7% of patients had pre-contoured rods (PLAN, N=31), 53.3% did not (NON, N=34). Preoperatively, PLAN patients presented with greater cervical malalignment (CTPA: 4.0° vs 2.7°, p=0.015) and T1 Slope (33° vs 22°, p=0.013), but not global (SVA, TPA), or lumbopelvic alignment (PT, PI-LL, all p\u003e0.05). Postoperatively, PLAN patients had greater C2-C7 lordosis than NON patients (18° vs 7°, p=0.001), and a trend of superior TS-CL alignment (19° vs 23°, p=0.075), but did not differ in any other cervical, global, or lumbopelvic parameters (all p\u003e0.05). PLAN patients also showed superior pre- to postop changes in TS-CL (-7° vs 2.1°, p=0.026). Overall, 25% of patients had LIVs above C7-T1 (mean fusion length: 4.8±1.1 levels), while 75% had fusions extending lower (10.0±5.5 levels). For cases in which fusion extended below C7-T1, PLAN patients showed a trend of greater pre- to postop TS-CL correction (-3° vs 3°, p-0.076), more postop CL (14° vs 6°, p=0.007), and less lumbopelvic malalignment (PI-LL:-7.1° vs 0.1°, p=0.029) and (PT: 14° vs 19°, p=0.087), though this result is confounded by greater preop PI-LL and PT deformity for NON patients (both p 0.05). CONCLUSIONS For posterior cervical fusion cases, the use of preoperative planning and patient-specific, pre-contoured rods was associated with superior correction of cervical sagittal alignment. For cases in which fusion extended below C7-T1, use of contoured rods was associated with superior postop reciprocal alignment in the lumbopelvic spine, though this may be confounded by differences in preop alignment. For longer fusions, pre-planned and contoured rods may offer greater utility. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.