Radiological Signs of Adjacent Segment Degeneration Patients with Cervical Spondylotic Radiculopathy Treated with Posterior Cervical Cages: Two-Year Follow-Up

BACKGROUND CONTEXT: Select patients with nerve compression and cervical radiculopathy secondary to spondylosis can be successfully treated with indirect posterior cervical decompression and fusion with posterior cervical cages. Cervical fusion may have an influence on adjacent segment degeneration (ASD). PURPOSE: The aim of this study was to assess radiological signs of ASD at 2 years follow-up in patients treated with posterior cervical cages for cervical spondylotic radiculopathy. STUDY DESIGN/SETTING: Retrospective evaluation of cervical radiographs. PATIENT SAMPLE: Fifty-three patients who underwent posterior cervical fusion with DTRAX cervical cages for cervical spondylotic radiculopathy were enrolled into the study. The lateral cervical X-ray images were taken in neutral position preoperatively and at 1 and 2 years postoperatively. OUTCOME MEASURES: The adjacent levels were evaluation consisted of measurements of:1) Proximal junctional kyphosis (PJK);2) Disc height ratio (DHR) – ratio of the disc height and the lower vertebrae height measured in the in the middle;3) Heterotopic ossification (HO) – none,!50%, O50 % , complete bridging of the disc;4) Kellgren and Lawrence Osteoarthritis Severity Grade (OSG).5) Neck Disability Index(NDI), Visual Analog Scale(VAS), and SF-12 Mental(MCS) and Physical Component Score(PCS). METHODS: The results were compared with ANOVA test, with p!0.05 considered as significant. ASD was defined as an increase of HO or OSG by 1 grade in new cases and by 2 grades if pre-existing disc degeneration was present before surgery (DDS). RESULTS: There were no revision surgeries at the operated level or at adjacent levels. Disc degeneration signs were present before surgery (DDS) in 21 patients in upper level and in 22 patients in lower level. In 2 patients there were new grade 1 ASD changes, 1 in level above and 1 in level below at 2 years postoperatively. In patients with pre-existing disc degeneration at the adjacent level, there were 0 cases of adjacent level degeneration progression of 2 grade or more. There were no significant changes in DHR and in PJK in all patients and in patients with ASD, however, there were tendency in patients with signs of ASD to decrease DHR in time. The mean PJK before surgery was -1.02 64.6 , 1 year after surgery -0.86 64.7 and 2 years after surgery was -0.59 65.4 ; p50.5342The mean DHR in all patients before surgery was 43.3 66.3 , 1 year after surgery 43.3 66.6 and 2 years after surgery was 43.1 66.8 ; p50.7290The mean DHR in ASD patients before surgery was 44.1 65.6 , 1 year after surgery 42.667.2 and 2 years after surgery was 40.9 67.8 ; p50.1836.The mean preop and 2-year scores were: NDI: 32.3 vs 9.1 (p!0.0001); VAS Neck Pain: 7.4 vs 2.6(p!0.0001); VAS Arm Pain: 7.4 vs 2.6 (p!0.0001); SF-12 PCS: 34.6 vs 43.6(p!0.0001) and SF-12 MCS: 40.8 vs 51.4 (p!0.0001). CONCLUSIONS: Indirect decompression and posterior cervical fusion using the DTRAX Cage may be an effective option in select patients with single level cervical radiculopathy. In patients treated with posterior cervical cage progression of disc degeneration is much more common on the basis of preoperative changes than new ASD. Posterior cervical fusion with cervical cage does not induce or accelerate adjacent segment degeneration in the great majority of patients (more than 1 score). Further evaluation to establish long-term incidence of ASD in patients treated with posterior cervical cage is needed. FDA DEVICE/DRUG STATUS: DTRAX Cervical Cage (Providence Medical Technology, Inc.) (Approved for this indication).