Lumbar discectomy is associated with higher rates of lumbar fusion.

BACKGROUND CONTEXT: Lumbar disc herniation affects more than 3 million people in the United States every year, and the rate of operation continually increases, particularly in patients 60 years or older (Taylor et al., 1994; Jordan et al., 2011). Surgical discectomy is a common treatment for lumbar disc herniation (Taylor et al., 1994; Atlas et al., 1996). One concern for this method is the risk of undergoing additional surgeries (Jordan et al., 2011; Österman et al., 2003; Lebow et al., 2011). There are very limited population-level studies that examine the rate of lumbar fusion after lumbar discectomy. Additionally, there is no study that examines the risk of undergoing lumbar fusion in patients who have undergone lumbar discectomies compared with the risk of lumbar fusion in the general population with no previous lumbar discectomy.

PURPOSE: The present study aimed to calculate a more definitive rate of lumbar fusion after a lumbar discectomy procedure using a population-size study of more than 200,000 patients in the Truven Healthcare Analytics Marketscan Research Database who underwent discectomies. Additionally, the study aimed to compare the rate of lumbar fusion in patients who have undergone a lumbar discectomy to the rate of lumbar fusion in patients with no prior lumbar discectomy procedure.

STUDY DESIGN/SETTING: This is a retrospective cohort study.

PATIENT SAMPLE: The patients from both parts of the present study were extracted from the Truven Healthcare Analytics Marketscan Research Database. Ten-year fusion after discectomy rates: 223,291 patients who underwent discectomies from the years 2003 to 2015. Fusion rate comparison: 489,975 patients with a previous lumbar ICD-9 (International Classification of Diseases, Ninth Revision) diagnosis code who have also been enrolled in the database for at least 10 years.

OUTCOME MEASURES: Ten-year fusion after discectomy rates: The proportion of patients who received a lumbar fusion up to 10 years after a lumbar discectomy. Fusion rate comparison: The proportion of patients who received a lumbar fusion after a lumbar discectomy compared with the proportion of patients who received a lumbar fusion with no previous lumbar discectomy.

METHODS: Ten-year fusion after discectomy rates: The patients who had undergone discectomies were filtered in the Marketscan database via Current Procedural Terminology (CPT) codes specific for lumbar discectomy (63030, 63035). Patients who had a lumbar fusion before or concurrently with these indexed lumbar discectomy dates were removed from the index group. The group was then followed up every year up to 10 years after the initial indexed lumbar discectomy dates for reoperation involving a lumbar spinal fusion according to the lumbar fusion CPT codes (22533, 22558, 22612, 22630, 22632, 22633, 22634, 22534, 22585, 22614). Fusion rate comparison: Study population only included patients who had a previous lumbar ICD-9 diagnosis in the Marketscan database (7242, 72210, 72251, 72252, 72273, 72293, 7213, 72142, 72283, 72293, 7243, 72402, 72403, 7244, 7245, 7249). The patients were then separated into two arms: one with patients who had undergone lumbar discectomy after initial lumbar diagnosis and another with patients who had not undergone a lumbar discectomy procedure. Pearson chi-square test was used to assess significance when comparing the proportion of patients who receive lumbar fusion after lumbar discectomy with the proportion of patients who receive lumbar fusion without a prior lumbar discectomy in the general ICD-9 lumbar diagnosis population.

RESULTS: For the 10-year trend of lumbar fusion rates after lumbar discectomy, the rate of fusion ranged from 1.69% (1-year time frame after discectomy) to 8.50% (10-year time frame after discectomy). When comparing the two cohorts in the second part of the present study, the fusion rates were 12.50% for the discectomy group and 4.19% for the non-discectomy group. The Pearson chi-square test reported a statistically significant difference between the fusion rates of the two groups (p<.0001, α=.05). We found that people who had a lumbar discectomy procedure were 2.97 (95% confidence interval [2.86, 3.10]) times more likely to undergo a lumbar fusion than those who with a lumbar diagnosis but had not undergone a lumbar discectomy in the past.

CONCLUSIONS: Our study is the largest population study that explores the rate of lumbar fusion after an initial lumbar discectomy. To our knowledge, it is the first study that concludes that an initial lumbar discectomy is statistically associated with an increased likelihood of a patient undergoing a lumbar fusion in the future. We observed that patients who had previously undergone a lumbar discectomy were roughly three times more likely to undergo a lumbar fusion procedure than a patient with a lumbar diagnosis, but had not undergone a lumbar discectomy. Although not calculated, it stands to reason the difference would be even greater when comparing the discectomy population with a population without lumbar diagnoses. This finding can be an important supplement for the physician-patient discussion regarding expectations and potential for reoperation.