A prospective randomised study on the long-term effect of lumbar fusion on adjacent disc degeneration

Abstract

The existence and importance of an accelerated adjacent segment disc degeneration (ASD) after lumbar fusion have previously not been demonstrated by RCTs. The objectives of this study were, to determine whether lumbar fusion in the long term accelerates degenerative changes in the adjacent disc and whether this affects the outcome, by using a prospective randomised design. A total of 111 patients, aged 18-55, with isthmic spondylolisthesis were randomised to exercise (EX, n = 34) or posterolateral fusion (PLF, n = 77), with (n = 37) or without pedicle screw instrumentation (n = 40). The minimum 10 years FU rate was 72%, with a mean FU time of 12.6 years (range 10-17 years). Three radiographic methods of ASD quantification were used, i.e. two digital radiographic measurement methods and the semi quantitative UCLA grading scale. One digital measurement method showed a mean disc height reduction by 2% in the EX group and by 15% in the PLF group (p = 0.0016), and the other showed 0.5 mm more disc height reduction in the PLF compared to the Ex group (ns). The UCLA grading scale showed normal discs in 100% of patients in the EX group, compared to 62% in the PLF group (p = 0.026). There were no significant differences between instrumented and non-instrumented patients. In patients with laminectomy we found a significantly higher incidence of ASD compared to non laminectomised patients (22/47 vs. 2/16 respectively, p = 0.015). In the longitudinal analysis, the posterior and anterior disc heights were significantly reduced in the PLF group, whereas in the EX group only the posterior disc height was significantly reduced. Except for global outcome, which was significantly better for patients without ASD, the clinical outcome was not statistically different in patients with and without ASD. In conclusion, the long-term RCT shows that fusion accelerates degenerative changes at the adjacent level compared with natural history. The study suggests that not only fusion, but also laminectomy may be of pathogenetic importance. The clinical importance of ASD seems limited, with only the more severe forms affecting the outcome.

Adjacent segment degeneration after single-segment PLIF: the risk factor for degeneration and its impact on clinical outcomes

“…In a prospective clinical study, Ekman et al [24] found that postoperative adjacent segment degeneration occurred in all the patients receiving decompressive laminectomy and posterior fusion with fixation, and that its incidence was significantly higher than that in patients not undergoing decompressive laminectomy. They speculated that decompressive laminectomy was a risk factor for adjacent segment degeneration.…”

Recurrent adjacent segment disease and cauda equina syndrome

“…The clinical relevance of ASD is low in the great majority of cases [2,[6][7][8]. Cauda equina syndrome is a very unusual onset of ASD.…”

“…Unfortunately, the prevalence of degenerative changes in patients for whom fusion has been prescribed, but not performed, is uncertain. A recent prospective randomized study [8] comparing the effect of fusion with natural history in isthmic spondylolisthesis suggests that laminectomy and fusion accelerate degeneration of the adjacent segment. However, the prevalence of severe ASD is low and the effect on clinical outcome limited.…”

Treatment of Adult Spondylolisthesis: PLIF versus PLF: Comparitive Study of Early Functional Outcome

“…In a study by Shalabi [22] adjacent segment degeneration was considered of prime importance and proved to be a factor in outcome. Compared to PLF only, PLF+ PLIF/TLIF were statistically significantly associated with a greater correction of spondylolisthesis.…”