Clinical impact and imaging results after a modified procedure of ACDF: a prospective case-controlled study based on ninety cases with two-year follow-up

Study design This is a prospective case-controlled study. Background To analyze the postoperative axial pain and cage subsidence of patients presenting with cervical spondylotic myelopathy (CSM) after a modified procedure of ACDF (mACDF). Methods Ninety patients with CSM were prospectively collected from 2014 to 2018. The patients were divided into spread group and non-spread group (48:42 ratio) according to the cage placement with or without releasing the Caspar cervical retractor after decompression. Spread group received conventional ACDF and non-spread group received mACDF. Patients were followed-up for at least 24 months after surgery. Radiologic data, including height of intervertebral space and Cobb Angle, were collected. Nervous system function was obtained using JOA scores, and level of pain was assessed using VAS scores. Results A total of 90 patients were enrolled and the patients were divided into spread group (n = 48) and none-spread group(n = 42). Cage subsidence of (spread group vs none-spread group) was (0.82 [+ or -] 0.68 vs 0.58 [+ or -] 0.81) mm, (0.64 [+ or -] 0.77 vs 0.34 [+ or -] 0.46) mm, (0.48 [+ or -] 0.43 vs 0.25 [+ or -] 0.28) mm, and (0.45 [+ or -] 0.47 vs 0.17 [+ or -] 0.32) mm at 3 months, 6 months, 12 months and 24 months, respectively. The period exhibiting the most decrease of the height of intervertebral space was 3 months postoperatively. However, there was no statistical difference in the height of intervertebral space, JOA or VAS scores at the final follow-up between the two groups. Conclusions The mACDF can avoid excessive distraction by releasing the Caspar Cervical retractor, restore the "natural height" of cervical vertebra, relieve immediate pain after surgery, and prevent rapid Cage subsidence and the loss of cervical curvature. Keywords: Cervical spondylotic myelopathy, Modified ACDF, Axial pain, Cage subsidence, Natural height