Clinical And Radiological Analysis Of Artificial Cervical Disc Arthroplasty: Eight-year Follow-up Results Compared With Anterior Cervical Discectomy And Fusion

Objective: Artificial cervical disc has been reported with satisfactory short-and medium-term clinical results.However,the long-term clinical and radiographic outcomes are seldom reported.The purpose of this study was to compare the eight-year follow-up results in patients who underwent artificial cervical disc arthroplasty with patients received ACDF,and assess the incidence of heterotopic ossification(HO)and its effect on clinical outcome and mobility of the device.Methods: Thirty-one patients underwent artificial cervical disc arthroplasty,and 35 patients underwent ACDF were included in the study.The Japanese Orthopedic Association(JOA)scores,neck disability index(NDI),visual analogue scale(VAS)of neck and arm pain,and the radiographs were used to evaluate the outcomes.The heterotopic ossification(HO)was determined by CT scan and was classified into three subgroups to compare the related effect.Adjacent segment degeneration(ASD)was also observed.Results: At final follow-up,we reviewed the records of patients who underwent surgical treatment for cervical degenerative disk disease(CDDD)at a single institution by a single surgeon between January 2005 and December 2007.The inclusion criteria were degenerative disk disease leading to radiculopathy or myelopathy between C3-7,which had not responded to conservative treatment.Exclusion criteria for cervical arthroplasty included previous cervical spine surgery,active infection,ossification of the posterior longitudinal ligament,acute spinal trauma,pure axial neck pain,or radiographic signs of instability.Patients with the latter two conditions were performed with ACDF.Based on these criteria,39 patients implanted with artificial cervical discs and 48 patients received ACDF were enrolled in this study,but only 29 patients in artificial cervical disc arthroplasty group and 31 patients in ACDF group completed the clinical and radiological evaluations.The other patients were excluded for inadequate data or loss to follow-up.There were no significant differences in JOA scores between two groups,but the improvement in NDI and neck or arm VAS were significantly greater in the artificial cervical disc cohort.The ROM at the index levels were similar pre-operatively,but was significantly different at final follow-up between two groups.In artificial cervical disc arthroplasty group,the ROM decreased from 8.6°to 7.0°at final follow-up,with a significant difference between them.In the ACDF group uniformly lost ROM and achieved bone fusion(100 %).The range of movement of the cervical spine remained unchanged in artificial cervical disc arthroplasty group(47.7°vs.43.4°,p=0.190),whereas it decreased significantly in ACDF group(43.4°vs.37.2°,P=0.041)There were more restricted movement of the prosthesis and slight higher rate of axial pain in patients with severe-HO(grade ? and ?).Thirteen(28.9 %)levels developed ASD in artificial cervical disc group,which was significantly lower than that(59.6 %)in ACDF group.Conclusions: At eight year follow-up,the clinical and radiographic outcomes of artificial cervical disc arthroplasty compared favorably to those of ACDF.It avoided accelerated adjacent segment degeneration by preserving motion.However,severe HO restricted the ROM of the index segments and may be associated with postoperative axial pain.Long-term follow-up with large cohort is still necessary to determine what will happen to the adjacent levels.