Analysis of mid- to long-term follow-up outcomes after anterior cervical Hybrid surgery for the treatment of adjacent two-level cervical spondylosis

English Keywords:Cervical spondylosis  Anterior cervical Hybrid surgery  Bryan artificial cervical disc  Zygapophyseal joints  Center of rotation  Adjacent segment degeneration

English Abstract:

  【Abstract】 Objectives: To observe the clinical and radiological outcomes of mid- to long-term follow-up of anterior cervical Hybrid surgery for the treatment of adjacent two-level cervical spondylosis, and to evaluate the in vivo motor function status of the arthroplasty level with Bryan artificial cervical disc. Methods: A retrospective study was performed on the patients who underwent adjacent two-level anterior cervical Hybrid surgery(Bryan disc for arthroplasty level and MC+cage for fusion level) from July 2010 to December 2013. And a total of 43 patients(23 males and 20 females) each with a range of motion(ROM) >5° at the arthroplasty segment at final follow-up were included, who were averaged 49.1±5.6 years old at the time of surgery. Preoperative symptoms were mainly attributable to myelopathy(26 cases), radiculopathy(6 cases), and myeloradiculopathy(11 cases). The mean follow-up period was 95.43±8.21 months(range, 84-119 months). The clinical outcomes were assessed by the Odom criteria, Japanese Orthopaedic Association(JOA) score, visual analogue scale(VAS), and neck disability index(NDI). The neutral-lateral and flexion-extension cervical radiographs were collected before operation and at final follow-up. The radiological parameters including the ROMs of the overall cervical spine(C2-C7) and the arthroplasty level, flexion and extension-center of rotation(FE-COR) at the arthroplasty level, ROM of adjacent levels, as well as the lordosis angles of the operated level and overall cervical spine(C2-C7) were measured and compared between preoperation and the final follow-up. At final follow-up, adjacent segment degeneration(ASD) and bony fusion at the fusion level were observed, and the translation and the anatomical parameters of zygapophyseal joints were measured at the arthroplasty level, including the height of superior articular process(HSAP), orientation of zygapophyseal joint spaces(OZJS), and the length of superior articular surface(LSAS), and meanwhile correlations between FE-COR and other follow-up data were analyzed. Results: In comparison with preoperative values, the JOA score significantly increased(9.26±3.38 vs 15.21±1.42, P<0.05) with an improvement rate of (80.23±13.80)%, and the NDI, VAS(neck pain), and VAS(arm pain) significantly decreased(34.12±8.96 vs 7.21±4.32, P<0.05; 5.77±2.28 vs 1.72±0.96, P<0.05; 5.26±2.67 vs 1.14±0.83, P<0.05) with improvement rates of (80.03±10.52)%, (69.85±13.44)%, and (78.84±15.89)%, respectively. The excellent or good rate in Odom criteria was 83.72%(excellent, 24 cases; good, 12 cases; satisfactory, 7 cases). The lordosis angles of overall cervical spine and the operated level increased significantly from 14.76°±8.04° and 4.78°±5.86° preoperatively to 20.62°±9.06° and 6.75°± 4.65° at final follow-up, respectively(P<0.05). ROM of the overall cervical spine, FE-COR and ROM at the arthroplasty level, and ROM of adjacent levels at final follow-up showed no significant changes from those before operation(P>0.05). A total of 81 adjacent levels(43 superior levels and 38 inferior levels) were included in the study, and ASD occurred in 7 adjacent levels(7/81, 8.64%) of 7 patients(7/43, 16.28%). At final follow-up, one patient failed to achieve bony fusion at the fusion level, but the state was stable(ROM<2°). The fusion levels of the other patients all met the criteria for bony fusion. At final follow-up, no follow-up data showed at least moderate correlation with abscissa(X) of FE-COR at the arthroplasty level(P>0.05 or |r|<0.5), and ordinate(Y) of FE-COR was negatively correlated with ROM and translation(r=-0.674, P<0.05; r= -0.792, P<0.05) but positively correlated with HSAP(r=0.754, P<0.05) at the arthroplasty level, and moreover, no correlation was found between ordinate(Y) of FE-COR at the arthroplasty level and any other parameters(P>0.05 or |r|<0.5). Conclusions: The clinical and radiological outcomes were satisfactory at least 7 years after the adjacent two-level anterior cervical Hybrid surgery, and there was no evidence that the fusion level had an effect on the motor function status of the arthroplasty level.