BACKGROUND

The ligamentum flavum is the anatomic plane between the epidural and laminar-extralaminar spaces, which should be meticulously preserved for a possible reoperation. Preservation of the ligamentum flavum together with other epidural anatomic structures, such as epidural fat tissue and venous plexuses, and limited removal of the lamina are important components in preventing epidural fibrosis that may be the cause of failed back surgery syndrome.

METHODS

One thousand five hundred patients underwent microdiskectomy with preservation of the ligamentum flavum over an 8-year period. This technique was performed with a small incision using an 18 mm-width mini Taylor retractor. The ligamentum flavum was released and preserved as a 3-sided flap. The disk content was totally removed and a pediculated fat graft was used to cover the root at the end. Four hundred patients operated on with the ligamentum flavum preserving technique were randomly selected for this study (Group 1). Their results were compared with those of 200 patients who were operated on with the standard microdiskectomy (Group 2). Standard microdiskectomy technique was performed with fenestration and foraminotomy and the ligamentum flavum was partially or totally excised. Early clinical outcome was classified as excellent, good, fair, poor, or failure. The clinical mean follow-up period in Group 1 was 36.8 months and in Group 2 it was 32.4 months. One hundred patients from each group had computed tomographic scans with contrast administration performed at least one year after the operation to examine late epidural fibrosis. A questionnaire was given to all patients at least 3 times during the late follow-up period. The questionnaire required patients to describe their relief of pain, job performance, and abstinence from narcotic analgesic use.

RESULTS

Early clinical outcome (fourth postoperative week) in Group 1 was satisfactory in 96.75% of the patients, whereas it was satisfactory in only 81.5% in Group 2 (p < 0.001). The radiological examinations revealed fibrosis in 18% of the patients in Group 1 and 37% in Group 2 (p < 0.001). None of the patients in Group 1 were readmitted because of fibrosis-related symptoms. The reoperation rate in Group 1 was 4.5%. The recurrence rate was 1.75% and disc at another level was 2.5%. One patient was reoperated because of a suture granuloma. In Group 2, the reoperation rate was 9% (p < 0.05). The recurrence rate was 4.5%, disc at another level was 3.5% and extensive epidural fibrosis was 1%. Two patients who underwent surgery for epidural fibrosis in this group had disappointing outcomes. Overall success rate based on the questionnaire was 91% in Group 1 and 76% in Group 2 (p < 0.001).

CONCLUSIONS

The ligamentum flavum preserving technique is useful in achieving a favorable long-term outcome, and reoperation, if necessary, is easier and safer.