Recurrence Rate and Survival Analysis of the Lumbar Disc Herniation After Open Discectomy / 대한정형외과학회잡지

ABSTRACT

PURPOSE: The aim of this study was to estimate the true recurrence rate of lumbar disc herniation after open discectomy, and to compare these results with those from other studies. MATERIALS AND METHODS: From January 1992 to June 2002, the medical records and radiological findings, including a telephone survey were studied retrospectively. This study examined 306 cases, who had been operated by an open discectomy on a single level and had no other spinal lesions such as spondylolisthesis, spondylolysis, or spinal stenosis. MRI was used to confirm the diagnosis of a lumbar disc herniation in all cases. The recurrence of lumbar disc herniation was diagnosed only in those cases who had the same pattern of symptoms and was confirmed by MRI. The cases who had undergone additional surgery at another hospital at the same spinal level were also included as recurrence. In order to make up for weak points such the losses to a long term follow-up, statistical survival analysis was carried out using a life table method. In the life table method, the assumption is that all patients undergo surgery simultaneously. The longest follow-up duration was 11 years. RESULTS: In 252 of the 306 cases (82%), follow-up study was possible. The average duration of the follow-up was 5.9 years (from 1 to 11 years). The average age of the patients was 27.1 years (17 to 75), and the male to female ratio was 11.6 1. The most common lesion of lumbar disc herniation was L4-5 (74%) at the initial diagnosis. The simple recurrence rate was 8.3% (21 cases) using the conventional method, in which the cases lost to follow-up were excluded. Survival analysis showed that, the annual recurrence rate was highest at the first year postoperatively as 3.4%, but decreased with time. At the last follow-up of 11 years, the cumulative survival rate was 88.9% and the recurrence rate was estimated to be 11.1% at final stage. CONCLUSION: Using survival analysis, the true rate of a recurrence of lumbar disc herniation after an open discectomy calculated. Even though the annual recurrence rate decreased with time, the true recurrence rate using the conventional method may be higher than the results obtained suggest.