84. Does interbody fusion change ASD in the disc next to the fusion? 10 years of MRI follow-up on a randomized controlled study

Abstract

<h3>BACKGROUND CONTEXT</h3> Due to the increasing number of spinal procedures performed worldwide, adjacent degenerative disease has become a new focus area. Whether adjacent segment disease is a matter of normal degenerative development in the disc over time or a result of increased stiffness and stress due to the fusion is still debated. Nowadays TLIF is the most widely used interbody fusion method. The use of interbody fusion has been claimed to reduce degenerative changes in the spared free disc over time due to better sagittal balance and restoration of the lost lumbar lordosis. <h3>PURPOSE</h3> To compare degenerative changes on MRI between PLF and TLIF 10 years postsurgery in an RCT cohort. <h3>STUDY DESIGN/SETTING</h3> Randomized clinical trial (RCT). Long-term follow-up. <h3>PATIENT SAMPLE</h3> Out of a primary cohort of 100 patients included in a prospective RCT between inter-body fusion and instrumented posterolateral fusion, 79 were available for follow-up 10 years after inclusion in the RCT. Patients were seen in the outpatient clinic and offered MRI at long-term follow-up. <h3>OUTCOME MEASURES</h3> Changes over time in Modic, Pfirmann, Schizas, and Fardon and Milette. <h3>METHODS</h3> All MRI were classified according to degree of Modic changes, Pfirmann classification, Schizas classification, and Fardon and Milette classification in order to show the degree of degeneration of the discs above and below the fusion. The grading was done by independent observers without any contact to the patient. In patients who underwent secondary surgery, the immediately previous MRI was used and the degenerative changes measured according to the above-mentioned classifications. <h3>RESULTS</h3> The groups were equal regarding sex, age, diagnosis and number operated levels. The follow-up was 9.6 years. The Modic change found at the first upper level was none in (85%/68%), mostly grade 2 (12%TLIF/26%PLF). There was no significant difference between the two groups p=0.274. Nearly all patients did not show any sign of treatment needs regarding spinal stenosis according to Schizas classification 92%/92%; only 8/8% had type C and D at the first proximal level 9.6 years after surgery. Interestingly, the amount of spinal stenosis grade C and D was higher at second proximal disc. No difference between groups could be detected p = 0.930 & p = 0.500. The Pfirmann grading at the first proximal level did not show any difference between groups p = 0.952. <h3>CONCLUSIONS</h3> In an RCT, the use of interbody fusion (TLIF) does not reduce the degenerative changes in the first proximal disc next to the fusion in a long-term observational study period in comparison to a normal posterolateral instrumented fusion (PLF). Thus, degenerative changes in the first proximal level are not influenced by intercorporal devices. The incidence of spinal stenosis grade C and D, 10 years after lumbar fusion surgery are 8% at first proximal disc, 13 % at second proximal disc and 8% at first distal level. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.