Is low regional Hounsfield units (HU) of screw trajectory being one of the risk factors of hardware failure after posterior cervical fusions (PCFs) with instrumentation?

BACKGROUND CONTEXT For patients with multilevel degenerative cervical myelopathy, laminectomy and posterior cervical fusions (PCFs) with instrumentation are widely accepted technique for symptom relief. However, hardware failure is not rare which results in neck pain or even permanent neurological leision. The prevalence of hardware-related complications of laminectomy and posterior cervical fusions (PCFs) with instrumentation are lack of in-depth study. PURPOSE To investigate risk factors of hardware failure after laminectomy and posterior cervical fusions (PCFs) with instrumentation in patients with degenerative cervical myelopathy. STYDU DESIGN: single-center, retrospective study. METHODS Fifty-six patients who underwent laminectomy and posterior cervical fusions (PCFs) with instrumentation between January 2019 and January 2021 were included in a single institution. Patients were divided into the hardware failure group (n = 14) and no hardware failure group (n = 42). The sex, age, screw density, end vertebra (C7 or T1), cervical sagittal alignment parameters (C2-C7 lordosis, C2-C7 sagittal vertical axis, T1 slope, CL correction), and regional Hounsfield units (HU) of screw trajectory, morbidity of osteoporosis were collected and compared between the two groups. RESULTS The mean overall follow-up was 20.6 months (range, 12–30 months). There were no significant statistical differences in general information (age, gender, follow-up period) of patients between the two groups. The differences of fusion rate, fixation levels and screw density between the two groups were not statistically significant (p > 0.05). The failure rate of the fixation endpoint at T1 was lower than that at C7 (9% vs. 36.3%) (p < 0.05). The regional HU of pedicle screw(PS) and lateral mass screw(LMS) in failure group were lower than the ones of no failure group (PS: 267 ± 45 vs. 368 ± 43; LMS: 308 ± 53 vs. 412 ± 41) (p  0.05). The hardware failure rate in cases without osteoporosis was lower than that in cases with osteoporosis (14.3% vs. 57.1%) (p < 0.05). CONCLUSION Hardware failure was not uncommon after laminectomy and PCFs with instrumentation in patients with degenerative cervical myelopathy. Osteoporosis, fixation ended at C7, and low regional HU of screw trajectory were the independent risk factors.