Patient Risk for Recurrent Herniation and Readmission by Annular Defect Size

Lumbar microdiscectomy is among the most frequently performed spinal procedures in the United States. At the 17^th Annual Meeting of the International Society for the Advance of Spine Surgery, Ali Araghi, DO, an orthopaedic spine surgeon at The CORE Institute in Phoenix, AZ cited current literature reporting that recurrent herniation and early readmission rates (within 90 days post-operatively) are predominant causes of negative outcomes in these patients.

According to the literature, the weighted average rate of early lumbar repeat surgeries at index and other levels is 2.1%. Noting the average cost of revision lumbar discectomy is nearly $40,000, Dr. Araghi emphasized the importance of identifying major factors that contribute to the increased risk.

Dr. Araghi emphasized the importance of identifying major factors that contribute to the increased risk.One study reported that patients with large annular defects had a 21% rate of reoperation, compared to a 1% rate among patients with small or slit-type defects. A second study reported an 18% recurrent herniation rate in patients with large annular defects. Noting that nearly 1 in 5 patients in the studies had a large annular defect, Dr. Araghi and colleagues undertook a study to evaluate annular defect size and its effect on early reherniation and subsequent readmission in lumbar discectomy patients.

Study Methods
The study compared 90-day reoperation rates cited in the literature (Group “A”) to revision rates in a cohort of 278 discectomy patients with annular defects measured intra-operatively to be larger than 6 mm, in a prospective manner (Group “B”; the large annular defect population). Group B patients were part of the Control (discectomy) group of a multicenter, prospective trial that compared patients with large annular defects (>6 mm) who had been randomized to treatment with either discectomy or discectomy with a bone-anchored annular closure device. For patients in Group B, the width of the annular defect was assessed with sizing paddles of incremental width. To obtain data for patients in Group A, investigators reviewed 112 manuscripts and identified 6 that reported lumbar reoperation within the first 90 days. A total of 49,331 patients were included in these manuscripts.

Study Results
A total of 13 of the 278 patients in Group B underwent reoperation (5.0%) at the index level within 90-days of initial surgery, compared to a 2.1% weighted average rate in Group A. Comparing the two groups, this study found that patients with large annular defects have more than twice the risk of early hospital readmission compared to the general discectomy population.

Explaining these findings, Dr. Araghi noted that the literature suggests that between 30% to 38% of the patients in Group A would be expected to have large annular defects. As such, they are already at elevated risk for recurrent herniation. At the same time, it would follow that patients with defects smaller than 6 mm would have an even lower rate of recurrent herniation than the cited 2.1% rate.

Dr. Araghi suggested that intra-operative identification of annular defect size may allow surgeons to risk-stratify patients for recurrent herniations, revision surgery and early readmission. Surgeons can potentially choose more aggressive discectomies for patients with annular defects >6 mm. Intra-operative risk stratification could ideally lower hospital costs (of up to nearly $40,000/case) and prevent negative patient outcomes.