Introduction 

The present gold standard in surgical treatment of lumbar disc herniation is the microscopic discectomy via interlaminar approach. However it is not suitable for far lateral disc prolapse, therefor we usually need an additional partial or complete arthrectomy of the facet joint. As an alternative we can provide the percutaneous endoscopic approach as a safe and tissue conserving method. Though we had to note a relatively high recurrence rate up to 15% in the literature leading to repeated surgery. This scientific work examines risk factors for recurrent far lateral disc prolapse liable to repeated surgery in various aspects of degeneration and instability in preoperative MRI scans. 

Methods 

A retrospective analysis of 126 patients, following percutaneuos endoscopic sequestrectomy for a far lateral disc prolapse in BG Klinikum Bergmannstrost Halle, Germany between December 2012 and June 2019 was performed. To detect patients with recurrent prolapse, that required surgery, we dispatched a questionnaire and analyzed the medical records. Finally we divided them into the Recurrence-group and Control-group. 

The preoperative MRI of the lumbar spine were investigated for signs of degeneration and instability: degeneration of disc (Pfirrmann) and vertebral endplates (Modic), spondylolisthesis (Meyerding and percentage), degeneration of facet joints (Pathria/Weishaupt), facet joint angles, facet tropism (Vanharanta), facet fluid sign, angle of lordosis and a newly introduced segmental Cobb angle, reconstructed out of the biplanar acquired MRI sequences. 

A total of 73 patients were analyzed (17 patients Recurrence-group, 56 patients Conrol-group). After univariate examination of the patient related and treatment related risk factors we examined the MRI based parameter on the parameters distribution. The significant parameters underwent logistic regression binary and multinominal. 

Results 

We found comparable precondition for patients with and without recurrence. There were three variables to be related to recurrent disc herniation: 1) high grade degeneration of the disc itself (Pfirrmann grades 4 and 5), 2) presence of Modic (Type 1 or 2) degeneration of the vertebral endplate and 3) coronar angulation of the segment towards the prolapse. 

Especially the segmental Cobb angle seems to have a strong impact on recurrence: 88% of patients who suffered from recurrent prolapse showed a deviation of coronar axis towards the side of the prolapse. 

Discussion 

Far lateral disc prolapse is a challenging condition in therapy of lumbar spine diseases. Endoscopic approach is smart, safe and fast, even though there is a relatively high rate of recurrence at least in our experience. A major reason might be preexisting (micro-) instability, which leads to increased stress. Especially disturbance of the alignment in coronar plain might be a newly identified predictor for recurrence. As future purpose it would be desirable to develop a scoring system to assess the individual patients risk. Particularly the segmental Cobb angle, detected in coronar reconstruction of the MRI data, seems to be a strong parameter for predicting recurrence without necessity of additive X-ray examination