The incidence of dural tears after complete resection of lumbar synovial cysts and the relation to the outcome.

Objective: Synovial cysts in the lumbar spine are uncommon causes of radicular pain. In cases where conservative treatment fails, surgical resection is recommended. Dural adhesions are common intraoperative findings; therefore, the removal of the cyst may sometimes result in dural tears. The frequency of dural tears is greater with synovial cysts than in other lumbar surgeries. Clinical parameters and characteristics seen on magnetic resonance imaging were assessed to investigate the correlation between the outcome after surgery of lumbar synovial cysts and dural tears.

Methods: This study was designed as a retrospective practice audit. Patient data were drawn from an electronic medical record system. Included were consecutive patients after microsurgical resection of symptomatic lumbar synovial cysts between May 2013 and November 2015. The surgical report was evaluated retrospectively regarding the extent of decompression and cyst resection as well as surgery-related complications. Pre-operative magnet resonance imaging was assessed concerning the reason for compression of the neural structures, the dimension of the cyst, and the signal of the cyst content in T2 images. In a follow-up examination about four weeks after surgery, the patient satisfaction index was evaluated.

Results: Forty-four consecutive patients after resection of a lumbar synovial cyst met the inclusion criteria. The mean patient satisfaction index was 2.0±1.0. Twenty-nine patients of the 38 patients with follow-up (76.3%) with a satisfaction index of 1 or 2 were rated as favorable. One revision surgery was necessary because of a cerebrospinal fluid fistula. Furthermore, in 4 patients an incidental durotomy occurred without any symptoms after surgery. Accordingly, the rate of dural tears was 11.4%. Dural tears were significantly more common in patients with a satisfaction index of 3 or 4 (P=0.04). Sixty percent of the patients with dural tears were operated on in level L5/S1 compared to 3 patients without a dural tear (P=0.008). There was no statistically significant difference between the different patient subgroups in any other analyzed parameter.

Conclusion: Dural tears were found significantly more often in patients without a good outcome; they appear to portend a poorer prognosis. The level L5/S1 was significantly more often affected. During surgery, it should be considered whether to remove the cyst completely and risk a dural tear, or to leave residuals of the cyst wall if otherwise a good decompression is achieved.