4:54 Maintenance of reduction in patients undergoing transforaminal lumbar interbody fusion for isthmic spondylolisthesis

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Purpose of study: Transforaminal lumbar interbody fusion (TLIF) represents an increasingly popular alternative to the traditional anterior-posterior spinal fusion and posterior lumbar interbody fusion (PLIF) technique in the treatment of patients with spondylolisthesis. Previous reports have demonstrated a reduction in perioperative complications and cost. To date, however, no reports have been published demonstrating long-term efficacy of TLIF in stabilizing and reducing slippage in patients with isthmic spondylolisthesis.Methods used: Plain lateral radiographs of 20 consecutive patients identified to have undergone a TLIF procedure for Grade 1 or 2 isthmic spondylolisthesis of L4–L5 or L5–S1 performed using a unilateral oblique Brantigan CFRP cage by one of three surgeons were analyzed for slip angle, slip percentage and intervertebral disc height. Films were reviewed for preoperative, first postoperative and most recent postoperative visits. For L5–S1 disease, slip angle was measured by taking the angle between a line drawn through the superior end plate of L5 and a line perpendicular to the posterior body of the S1. Slip percentage was determined by measuring the distance from the posterior aspect of S1 to the intersection of a line drawn through the posterior body of L5 and the superior end plate of S1, divided by the length of the inferior end plate of L5. Disc height was measured at the midpoint of the overlap between the two vertebrae. Similar methods were employed for L4–L5 spondylolisthesis. Data were analyzed using a paired, two-tailed t test.of findings: Average time from surgery to first follow-up was 39 days; average time to most recent follow-up was 242 days. Average preoperative values for slip angle, slip percentage and disc height were −22 degrees, 29% and 6.6 mm, respectively. For initial follow-up, these values were −16.2 degrees, 21.8% and 8.9 mm, and recent follow-up values were −16.6 degrees, 21.6% and 9.0 mm. Changes in slip angle, slip percentage and disc height were significantly different between preoperative and first postoperative values (p=.035, p<.002, p<.002, respectively) as well as most recent follow-up (p<.002, p<.0002, p<.001, respectively). There were no significant differences for slip angle, slip percentage or disc height between the two postoperative measurements.Relationship between findings and existing knowledge: Presently, no series of patients have been published demonstrating the efficacy of TLIF in deformity correction for patients with isthmic spondylolisthesis. The results of this study indicate that this procedure is useful in reducing slip angle and slip percentage, while increasing disc space height. The data presented here also suggest that these changes are stable over time, as indicated by the lack of significant difference between the two follow-up groups.Overall significance of findings: As demonstrated in this series, TLIF is an effective technique for reducing spinal deformity caused by isthmic spondylolisthesis. Moreover, this reduction in deformity appears to be stable over at least mid-length follow-up. Longer-term follow-up and a comparison of these results with those of patients undergoing PLIF would be helpful in the future.Disclosures: Device or drug: unilateral use of Brantigan cage. Status: investigational.Conflict of interest: Todd Albert, grant research support; Dupuy Acromed; Dr. Albert receives royalties on certain products used in TLIF procedure.