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The authors report two cases of spontaneous regression of disc herniation at the level adjacent to the anterior lumbar interbody fusion (ALIF) level. This phenomenon may be due to the increased tension on the posterior longitudinal ligament (PLL) by appropriate restoration of the disc height and lumbar lordosis, which is a mechanism similar to ligamentotaxis applied to the thoracolumbar burst fracture.

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The authors report the case of a 52-year-old man who had undergone resection of an ossified posterior longitudinal ligament via the anterior approach. The patient experienced postoperative neurological deterioration that may have been caused by a massive cord herniation associated with a dural defect at the corpectomy site. Spinal cord herniation may develop as a complication of anterior cervical decompression. Surgeons should be alert to this condition when planning to treat cervical ossification of the ossified posterior longitudinal ligament via the anterior approach.

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STUDY DESIGN: Retrospective study of consecutive patient series. OBJECTIVE: To review the etiology of failed back surgery syndrome due to sagittal imbalance and radiographic and clinical results of surgical treatment of these patients who were treated with combined anterior and posterior arthrodesis. SUMMARY OF BACKGROUND DATA: Sagittal imbalance after spinal fusion surgery may be a major source of pain and disability. Preventing iatrogenic sagittal imbalance should be a key objective during spinal fusion surgery. METHODS: Retrospective review of revision spine surgery due to sagittal imbalance treated with combined anterior and posterior spinal arthrodesis in the 19 patients. Outcome variables included radiographic measures of preoperative, postoperative, and follow-up films, and a clinical assessment using the Verbal Analogue Scale (VAS), Oswestry Disability Index, Macnab criteria, Satisfactory Index Instrument, and a review of postoperative complications. RESULTS: Mean age was 62 years (range, 49-74 years), and mean follow-up was 31 months (range, 24-37 months) for clinical and radiographic outcome variables. The mean preoperative sagittal imbalance was 116 (+/-65) mm, which improved to 32 mm (+/-29) after surgery. Mean lumbar lordosis was 15 degrees (+/-20 degrees) before surgery, and increased to 38 degrees (+/-13 degrees) at follow-up, an increase of 23 degrees. The mean VAS improved from 7.2 (back pain), 6.8 (leg pain) before the surgery to 3 (back pain), 3.2 (leg pain) after the surgery (P < 0.0001). The mean Oswestry Disability Index scores improved from 62 (+/-11) before the surgery to 36 (+/-12) after the surgery (P < 0.0001). Excellent or good outcome was demonstrated in 16 patients (84.2%). CONCLUSION: Most common causes of revision spine surgery due to sagittal imbalance were failure to enhance lumbar lordosis and adjacent disc degeneration after lumbar fusion surgery. These patients were effectively treated with a combined anterior and posterior arthrodesis. Following these surgical treatment, sagittal balance was generally improved with fair-to-good clinical outcomes, high patient satisfaction, and low perioperative complication rates.

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Percutaneous endoscopic lumbar discectomy (PELD) for migrated disc herniations is technically demanding due to the absence of the technical guideline. The purposes of this study were to propose a radiologic classification of disc migration and surgical approaches of PELD according to the classification. A prospective study of 116 consecutive patients undergoing single-level PELD was conducted. According to preoperative MRI findings, disc migration was classified into four zones based on the direction and distance from the disc space: zone 1 (far up), zone 2 (near up), zone 3 (near down), zone 4 (far down). Two surgical approaches were used according to this classification. Near-migrated discs were treated with "half-and-half" technique, which involved positioning a beveled working sheath across the disc space to the epidural space. Far-migrated discs were treated with "epiduroscopic" technique, which involved introducing the endoscope into the epidural space completely. The mean follow-up period was 14.5 (range 9-20) months. According to the Macnab criteria, satisfactory results were as follows: 91.6% (98/107) in the down-migrated discs; 88.9% (8/9) in the up-migrated discs; 97.4% (76/78) in the near-migrated discs; and 78.9% (30/38) in the far-migrated discs. The mean VAS score decreased from 7.5 +/- 1.7 preoperatively to 2.6 +/- 1.8 at the final follow-up (P < 0.0001). There were no recurrence and no approach-related complications during the follow-up period. The proposed classification and approaches will provide appropriate surgical guideline of PELD for migrated disc herniation. Based on our results, open surgery should be considered for far-migrated disc herniations.

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