Solis cage (PEEK) for anterior cervical fusion: preliminary radiological results with emphasis on fusion and subsidence

Background contextRecent literature has raised some apprehensions with regard to the usage of cervical cages.PurposeRadiological review of cases performed at our institution with a novel cage made of polyetheretherketone (PEEK).Study designRetrospective study.MethodsA retrospective review of the first 15 consecutive cases of single-level anterior cervical interbody fusion using the Solis cage (PEEK material) for cervical spondylotic radiculopathy or myelopathy was performed. The follow-up ranged from 12 to 35 months (average 18 months). Anteroposterior and lateral radiographs were taken immediately after the surgery and at intervals of 3, 6, 12, and 24 months after surgery. Anterior disc height (ADH), posterior disc height (PDH), interbody height ratio (IBHR), distance between the posterior margin of the cage and the posterior wall of the vertebral body (D-CPW), and interbody angle (IBA) were measured on the lateral radiographs and compared. Fusion was assessed by examining for trabecular continuity, bridging of bone across the disc space, and sclerosis at the vertebral end plates on both sides. The parameters assessed were time for fusion, subsidence, segmental sagittal alignment of the operated segment, and presence/absence of migration of the cage. Data were analyzed using the Mann-Whitney nonparametric test.ResultsFusion was evident at 3–6 months postsurgery in all cases except one (93.33% fusion rate at 6 months). At the last follow-up, fusion was maintained in all cases. The immediate postoperative ADH and PDH was significantly greater than the respective preoperative values and was maintained at the last follow-up though there was a significant amount of subsidence when the follow-up radiographs were compared with the immediate postoperative X-rays. The immediate postoperative IBHR was significantly greater than the preoperative IBHR, and was maintained at the last follow-up, but not statistically significant. The immediate postoperative IBA (lordotic angle) was greater than the preoperative IBA but was not statistically significant. The IBA at the last follow-up was lesser than the preoperative value but with no statistical significance. The IBA measured at the last follow-up was less than the value at the immediate postoperative period, but not statistically significant. There was no migration or extrusion of the cage at latest follow-up.ConclusionsThe high fusion rate, low subsidence, stability provided by the cage, and facilitation of radiological assessment are the result of the physical properties of the PEEK material as well as the design of the cage.