#373 Adjacent Segment Disease and Cervical Fusion Methods

Oral Posters: Cervical

Presented by: V. Agarwal

Author(s):

V. Agarwal (1)
S. Sarafini (1)
K. Knott (1)
M. Haglund (1)

(1) Duke University, Neurosurgery, Durham, NC, USA

Abstract

Background Context: ACDF is used to treat several conditions, with adjuncts such as grafts and locking plates to further enhance fusion. Given the large number of cervical fusions, examining long-term consequences is of importance. Adjacent segment disease, via degeneration at the inferior or superior segment(s), is the most well documented consequence. The current rate of prevalence is approximately 25% over 10-years, with C5-C6 the segment at greatest risk. Differences in incidence of ASD using various ACDF techniques is less well investigated.

Purpose: To compare prevalence/incidence of adjacent segment disease requiring surgical intervention between Autograft Without Plating (AWOP) and Allograft With Plating (one-level, ALP1; two-level, ALP2).

Study Design/Setting: Retrospective study of anterior cervical discectomy and fusions (ACDF) from 1996-2006 with follow-up through 2010.

Patient Sample: Consecutive series of 611 patients (275 males, 336 females) and 627 ACDF procedures using AWOP (n=179, 73 males, 98 females, mean age 48.7 years) or ALP techniques (nALP1=250, 122 males, 128 females, 49.6 years), nALP2=198 (80 males, 118 females, 53.5 years) with maximum 13 year follow-up (AWOP range 8-13 years, mean = 10.83 years, ALP1 range 3-13 years, mean = 6.05, ALP2 range 3-13 years, mean = 6.17).

Outcome Measures: Differences in prevalence, segments at risk, and mean annual incidence of adjacent segment disease requiring surgical intervention in previous ACDF patients were measured, while Kaplan-Meier survivorship analysis predicted time course to a second surgery (α< 0.05).

Methods: Retrospective analysis of one surgeon at our home institution from 1996-2006 of ASD requiring surgical intervention, defined as myelopathy or radiculopathy failing conservative therapy and leading to a second ACDF adjacent to the original fusion. Chi-squared and independent t-tests detected differences in prevalence, segments at risk, and mean annual incidence. Kaplan-Meier survivorship analysis predicted time course to a second surgery.

Results: Prevalence was found in 14.5% (89 cases/611 patients) over 13 years. Further surgery occurred in 22.3% of cases after AWOP, significantly more than ALP1/ALP2 (10.4%/11.6%, p< .005). Mean annual incidence was 1.6% for AWOP, significantly higher than ALP1/ALP2 (0.74%/0.68%, p< .05). Cumulative survival was 73.5% for AWOP, significantly lower than ALP1 only (88.4%, p< .03). Original fusions involving C5-6 were at most risk (p< .05).

Conclusions: ALP1/ALP2 required about half the additional ACDFs compared to AWOP over 13 years. Annual incidence was nearly double for AWOP versus ALP procedures. The C5-6 level was at greatest risk, involving superior/inferior segments comparably.