Comparison of Clinical and Imaging Outcomes of Cervical Disc Replacement in Patients with Different Hounsfield Units

To compare clinical and imaging outcomes after cervical disc replacement (CDR) in patients with different Hounsfield units (HU).We performed a retrospective study of patients with cervical degenerative disc disease treated by 1-level and 2-level Prestige-LP arthroplasty. The patients were divided into group A (HU <320), group B (HU 320-347), and group C (HU >347) according to the results of cervical vertebral HU measurement in the literature, and the clinical and radiographic results were compared among the 3 groups.A total of 127 patients were reviewed, comprising 13 patients in group A, 31 patients in group B, and 83 patients in group C. The clinical parameters were significantly improved postoperatively in the 3 groups (P < 0.05). However, no significant differences were found among the 3 groups at the final follow-up (P > 0.05). The mean postoperative intervertebral space height (ISH) was 4.76 ± 0.45 mm, 5.23 ± 0.81 mm, and 6.26 ± 1.12 mm in the 3 groups, respectively. The postoperative ISH in group C was significantly higher than those in the other groups at the final follow-up (P < 0.001). One patient in group A and 1 patient in group B had implant subsidence, and degeneration at the inferiorly adjacent level was radiographically identified in 30.77% patients in group A, 16.13% patients in group B, and 9.64% patients in group C. However, there were only significant differences between group A and group C in subsidence (P = 0.011) and occurrence of adjacent level degeneration (P = 0.032).The HU value has a large variation range among the patients with T-score ≥ -2.5. We found significantly increased rates of implant subsidence, loss of ISH, and adjacent segment degeneration in patients with lower HU value undergoing CDR. However, these radiographic complications did not predispose patients with lower HU value to worse clinical outcomes. Routine application of HU combined with dual-energy X-ray absorptiometry measurement to evaluate bone quality may help to screen the optimal candidates for CDR and reduce the implant-related complications.