gms | German Medical Science

Objective: Herniation can impair the ability of the lumbar disc to bear loads due to a reduced capacity to contain pressure in the presence of an annular defect and a loss of nucleus. Elements such as the facet-joints may become overloaded as a result. One goal of an annular closure device (ACD) is to help maintain normal disc biomechanics after discectomy by closing the anular defect, thereby allowing the surgeon better nucleus preservation. The purpose of this study was to investigate the condition of the facet joints in patients who had undergone a lumbar discectomy with and without an ACD.

Methods: The Barricaid endoprosthesis is an ACD, which consists of a woven-PET mesh, intended to block an anular defect while anchored to a vertebral body by a Ti bone anchor. ACD patients (n=75) were enrolled in two prospective, multi-center trials; primary lumbar discectomy patients (n=137) were enrolled in one prospective, multi-center trial with similar inclusion/exclusion criteria. CTs were reviewed by an independent radiologist using a four-point facet-joint osteoarthritis scale (Pathria et al, 1987).

Results: In the discectomy only group, there were 94 patients with paired pre-op and one year CT, of which 52 also had two year CT. In the ACD group, there were 63 patients with paired pre-op and one year CT, of which 44 also had two year CT. In patients who had undergone discectomy only, 43% exhibited facet degeneration, defined as a worse facet-joint grade at one-year post-op relative to pre-op in at least one of the facets of the index-level, compared to 24% of ACD patients (p=0.018, Fisher's Exact). In separate, univariate logistic regressions of all patients, a lower probability for facet degeneration was observed in discs with smaller anular defects (p=0.041), discs which had less nucleus removed during discectomy (p=0.079), and discs implanted with the ACD (p=0.014). At two years, 41% of ACD and 56% of discectomy-only patients exhibited facet degeneration (p=0.158). The majority of these patients exhibited mild degeneration of their facets, however, 41% of discectomy-only patients exhibited moderate degenerative disease compared to 11% in ACD patients (p=0.047).

Conclusions: The significantly lower rate and the lower severity of facet degeneration in ACD patients suggest that the use of an ACD may help maintain the biomechanics of the disc and reduce the degenerative sequela observed after discectomy. ACD benefits may extend beyond preventing recurrence.