Long-term outcomes of artificial cervical disc replacement versus anterior cervical discectomy and fusion for single-level cervical spondylosis

English Keywords:Single-segment cervical spondylosis  Artificial cervical disc replacement  Anterior cervical fusion  Long-term follow-up  Heterotopic ossification  Adjacent segment disease

English Abstract:

  【Abstract】 Objectives: To compare the long-term efficacies of artificial cervical disc replacement(ACDR) and anterior cervical discectomy and fusion(ACDF) in treating single-level cervical spondylosis. Methods: A retrospective analysis was conducted on the patients with C5/6 single-segment cervical spondylosis admitted and treated at the Department of Orthopedics at the Second Affiliated Hospital of Naval Medical University between January 2009 and August 2012, with follow-up periods exceeding 10 years. Based on surgical approach, the patients were divided into an ACDR group and an ACDF group. The ACDR group comprised 30 patients(20 males and 10 females), with a mean age of 41.5±4.4 years(range, 32 to 50 years), and the patients received the Discover artificial cervical disc prosthesis. The ACDF group included 27 patients(19 males and 8 females), with a mean age of 39.2±5.3 years(range, 31 to 50 years). The follow-up periods were 129.4±6.7 months for the ACDR group and 127.0±4.1 months for the ACDF group. There were no statistically significant differences between the two groups in terms of gender, age, body mass index(BMI), classification of cervical spondylosis, disease duration, operative time, and intraoperative blood loss(P>0.05). Neurological function was assessed preoperatively and at final follow-up using the Japanese Orthopaedic Association(JOA) score and neck disability index(NDI). The C2-C7 Cobb angle was measured on lateral cervical radiographs, and heterotopic ossification(HO) at the ACDR surgical level was graded according to the McAfee classification. The global cervical range of motion(ROM) and segmental ROM were measured on flexion-extension lateral radiographs. Intervertebral disc Pfirrmann grading was assessed according to T2-weighted MRI scans. Complications during follow-up, including neurological deterioration, cerebrospinal fluid leakage, implant loosening, and adjacent segment disease(ASD), were recorded. Results: At final follow-up, both JOA scores and NDI showed significant improvement compared to preoperative values in both groups(P<0.05). However, there were no statistically significant differences in JOA scores or NDI between the two groups at the same time points(P>0.05). No significant differences were found in the C2-C7 Cobb angle within or between groups before and after surgery(P>0.05). The global cervical ROM in the ACDF group decreased significantly from 47.1°±13.8° preoperatively to 38.3°±12.8° at final follow-up(P<0.05). In contrast, the global cervical ROM in the ACDR group showed no significant change(45.8°±13.5° at final follow-up vs 46.3°±13.4° preoperatively, P>0.05). The ROM at the surgical segment in the ACDR group significantly decreased from 10.0°±1.4° preoperatively to 9.2°±2.0° at final follow-up(P<0.05). The ROMs at both superior(C4/5) and inferior(C6/7) adjacent segments were significantly lower in the ACDR group compared to the ACDF group(P<0.05), while no significant difference was found at the non-adjacent segment(C3/4)(P>0.05). Pfirrmann grades at the superior, inferior, and non-adjacent segments increased significantly from preoperation to final follow-up in both groups(P<0.05). However, the Pfirrmann grades at both the superior and inferior adjacent segments were significantly lower in the ACDR group compared to the ACDF group(P<0.05), whereas no significant difference was observed at the non-adjacent segment(P>0.05). At final follow-up, HO occurred in 14(46.7%) cases in the ACDR group(2 cases of McAfee grade Ⅰ, 5 cases of grade Ⅱ, and 7 cases of grade Ⅲ), while none ASD was observed. Two patients(6.7%) in the ACDR group exhibited prosthesis subsidence with anterior migration, but were asymptomatic and did not require surgical intervention. In the ACDF group, two patients(7.4%) underwent secondary surgery due to ASD. The reoperation rate showed no statistically significant difference between the two groups(P>0.05). Conclusions: There is no significant difference in long-term efficacy and safety between ACDR and ACDF for treating C5/6 single-level cervical spondylosis. The incidence of HO after ACDR is high, but without McAfee Grade Ⅳ ossification. ACDR exhibits reduced ROM and lower degeneration grades in the adjacent segment than ACDF.