Incidence and prevalence of surgery at segments adjacent to a previous posterior lumbar arthrodesis. [Journal Article - principal author]
Sears WR, Sergides IG, Kazemi N, Smith M, White GJ, Osburg B.
The Spine Journal 11 (2011) 11–20.
The Spine Journal 11 (2011) 11–20.
Abstract:
BACKGROUND CONTEXT: Adjacent segment disease (ASD) following lumbar spinal fusion has been an important reason behind the development of non-fusion stabilization technology. However, the incidence, prevalence and factors contributing to adjacent segment degeneration in the lumbar spine remain unclear. A range of prevalence rates for ASD have been reported in the lumbar spinal literature but the annual incidence has not been widely studied in this region. Conflicting reports exist regarding risk factors, especially fusion length.
PURPOSE: To determine the annual incidence and prevalence of further surgery for adjacent segment disease (SxASD) following posterior lumbar arthrodesis and to examine possible risk factors.
STUDY DESIGN: Retrospective cohort study.
PATIENT SAMPLE: 912 patients who underwent 1000 consecutive posterior lumbar interbody fusion (PLIF) procedures, with mean follow-up duration of 63 months (range: 5 months – 16 years).
OUTCOME MEASURES: Further surgery for ASD or surgery free survival.
METHODS: A postal and telephone survey. Follow-up rate: 91% of patients. The annual incidence and prevalence of ASD requiring further surgery were determined using Kaplan-Meier survivorship analysis. Cox proportional-hazards (Cox) regression was used for multivariate analysis of possible risk factors. Significance was set at p<0.05.
RESULTS: Further surgery for ASD occurred following 130/1000 or 13% of procedures at a mean time of 43 months (range: 2.3 – 162 months). The mean annual incidence of SxASD over the first 10-years, in all patients, was 2.5% (95%CI: 1.9-3.1) with prevalences of 13.6% & 22.2% at 5 & 10 years, respectively. Cox regression modelling found that the number of levels fused (p≤0.0003), age of the patient, fusing to L5 and performing an additional laminectomy adjacent to a fusion all independently affect the risk of SxASD. The mean annual incidence figures in the first 10-years following a lumbar fusion were 1.7 % (95%CI: 1.3-2.2) following fusion at single levels, 3.6% (2.1-5.2) post two levels and 5.0% (3.3-6.7) post three and four levels. The five and ten year prevalences were 9% & 16%, 17% & 31% and 29% & 40% following one, two and three/four level fusions, respectively. The risk of SxASD in patients less than 45-years was one quarter (95%CI: 10-64%) the risk of patients over 60-years (p=0.003). A laminectomy adjacent to a fusion increases the relative risk by 2.4 times (95%CI: 1.1-5.2, p=0.03). Stopping a fusion at L5 is associated with a 1.7 fold increased risk (95%CI: 1.2-2.4, p=0.007) of SxASD compared with a fusion to S1, for fusions of the same length.
CONCLUSION: The overall annual incidence and predicted 10-year prevalence of further surgery for ASD following lumbar arthrodesis were 2.5% and 22.2%, respectively. These rates varied widely depending on the identified risk factors. While young patients who underwent single level fusions were at low risk, patients who underwent fusion of three or four levels had a three-fold increased risk of further surgery, compared with single-level fusions (p<0.0001), and a predicted 10-year prevalence of 40%.
BACKGROUND CONTEXT: Adjacent segment disease (ASD) following lumbar spinal fusion has been an important reason behind the development of non-fusion stabilization technology. However, the incidence, prevalence and factors contributing to adjacent segment degeneration in the lumbar spine remain unclear. A range of prevalence rates for ASD have been reported in the lumbar spinal literature but the annual incidence has not been widely studied in this region. Conflicting reports exist regarding risk factors, especially fusion length.
PURPOSE: To determine the annual incidence and prevalence of further surgery for adjacent segment disease (SxASD) following posterior lumbar arthrodesis and to examine possible risk factors.
STUDY DESIGN: Retrospective cohort study.
PATIENT SAMPLE: 912 patients who underwent 1000 consecutive posterior lumbar interbody fusion (PLIF) procedures, with mean follow-up duration of 63 months (range: 5 months – 16 years).
OUTCOME MEASURES: Further surgery for ASD or surgery free survival.
METHODS: A postal and telephone survey. Follow-up rate: 91% of patients. The annual incidence and prevalence of ASD requiring further surgery were determined using Kaplan-Meier survivorship analysis. Cox proportional-hazards (Cox) regression was used for multivariate analysis of possible risk factors. Significance was set at p<0.05.
RESULTS: Further surgery for ASD occurred following 130/1000 or 13% of procedures at a mean time of 43 months (range: 2.3 – 162 months). The mean annual incidence of SxASD over the first 10-years, in all patients, was 2.5% (95%CI: 1.9-3.1) with prevalences of 13.6% & 22.2% at 5 & 10 years, respectively. Cox regression modelling found that the number of levels fused (p≤0.0003), age of the patient, fusing to L5 and performing an additional laminectomy adjacent to a fusion all independently affect the risk of SxASD. The mean annual incidence figures in the first 10-years following a lumbar fusion were 1.7 % (95%CI: 1.3-2.2) following fusion at single levels, 3.6% (2.1-5.2) post two levels and 5.0% (3.3-6.7) post three and four levels. The five and ten year prevalences were 9% & 16%, 17% & 31% and 29% & 40% following one, two and three/four level fusions, respectively. The risk of SxASD in patients less than 45-years was one quarter (95%CI: 10-64%) the risk of patients over 60-years (p=0.003). A laminectomy adjacent to a fusion increases the relative risk by 2.4 times (95%CI: 1.1-5.2, p=0.03). Stopping a fusion at L5 is associated with a 1.7 fold increased risk (95%CI: 1.2-2.4, p=0.007) of SxASD compared with a fusion to S1, for fusions of the same length.
CONCLUSION: The overall annual incidence and predicted 10-year prevalence of further surgery for ASD following lumbar arthrodesis were 2.5% and 22.2%, respectively. These rates varied widely depending on the identified risk factors. While young patients who underwent single level fusions were at low risk, patients who underwent fusion of three or four levels had a three-fold increased risk of further surgery, compared with single-level fusions (p<0.0001), and a predicted 10-year prevalence of 40%.