Anterior intervertebral osteotomy and fusion (AIOF): an IPUP-guided standardized extension of anterior cervical discectomy and fusion for multilevel cervical spondylotic myelopathy

Abstract Purpose To evaluate the clinical and radiographic outcomes of anterior intervertebral osteotomy and fusion (AIOF), guided by the inflection point of the uncinate process (IPUP), for the treatment of multilevel cervical spondylotic myelopathy (MCSM), and to compare these outcomes with those of laminoplasty. Methods We retrospectively reviewed 118 patients with MCSM who underwent surgery between January 2017 and December 2022 and had a minimum follow-up of 24 months. Of these, 57 patients underwent AIOF and 61 underwent laminoplasty. Perioperative outcomes, radiographic parameters, clinical outcomes, and complications were compared between the two groups. Repeated-measures outcomes were analyzed using linear mixed-effects models with adjustment for the corresponding baseline values and prespecified clinical covariates. Results Intraoperative blood loss was significantly lower in the AIOF group than in the laminoplasty group ( P < 0.05). After adjustment, at the final follow-up, the AIOF group had a greater C2–C7 Cobb angle (adjusted mean difference, 9.12°; 95% CI 6.83–11.42), a lower C2–C7 sagittal vertical axis (SVA) (− 9.75 mm; 95% CI − 13.30 to − 6.21), and a smaller spinal cord rotation angle (− 1.67°; 95% CI − 2.20 to − 1.15) than the laminoplasty group. In contrast, the laminoplasty group preserved greater cervical range of motion (AIOF vs. laminoplasty: −3.36°; 95% CI, −5.76 to −0.96). No clear between-group difference in Japanese Orthopaedic Association (JOA) scores was observed at the final follow-up (adjusted mean difference, 0.87; 95% CI − 0.09 to 1.84). VAS and NDI scores were statistically lower in the AIOF group, but the between-group differences did not reach previously reported minimal clinically important difference (MCID) thresholds. Measurement of spinal cord rotation showed good interobserver and intraobserver reliability (ICC, 0.86–0.94). The bony fusion rate in the AIOF group was 93.0%. Dysphagia occurred in 6/57 patients (10.5%) in the AIOF group, whereas axial symptoms and C5 palsy occurred in 10/61 (16.4%) and 4/61 (6.6%) patients, respectively, in the laminoplasty group. Conclusions Both AIOF and laminoplasty were associated with postoperative improvement in neurological function, with no clear between-group difference in JOA recovery. In this retrospective cohort, AIOF was associated with more favorable cervical sagittal parameters and a smaller spinal cord rotation angle, whereas laminoplasty preserved greater cervical range of motion at the final follow-up. Given the single-center, nonrandomized, retrospective design of this study, these findings require further validation in prospective, multicenter studies.