Ultrasonic Osteotome Assisted Full-Endoscopic en Block Resection of Thoracic Ossified Ligamentum Flavum: Technical Note and 2 Years Follow-up

Background: Conventional open laminectomy is considered to be the standard procedure for the treatment of thoracic ossified ligamentum flavum, but multi-segment thoracic laminectomy extensively removes the facet joints and ligamentous tissue, destroying the thoracic spine biomechanics and stability, may lead to delayed thoracic spine kyphosis deformities, which in turn can lead to potential neurological deterioration and local intractable pain. Objective: To introduce the technical notes and clinical outcome of ultrasonic osteotome assisted full-endoscopic en block resection of thoracic ossified ligamentum flavum. Study Design: A prospective cohort study. Setting: Hospital and outpatient surgery center. Methods: From January 2017 to March 2018, 15 patients with 1 - 2 segment thoracic ossified ligamentum flavum were treated with ultrasonic osteotome assisted full-endoscopic en block resection of thoracic ossified ligamentum flavum under local anesthesia. The magnetic resonance imaging and computed tomography of the thoracic spine was reexamined after the operation to evaluate the completeness of ossified ligamentum flavum resection and spinal cord decompression. The patients were followed up on the visual analog scale of back pain and radicular pain, Nurick score and mJOA score of neurological function, and Oswestry Disability Index at 1 week, 3 months, 6 months, one year, and 2 years after operation. Results: All operations of 17 segments thoracic ossified ligamentum flavum in 15 patients were successfully completed without intraoperative conversion to open surgery. There were no intraoperative spinal cord injuries, dura tears, postoperative cerebrospinal fluid leakage, postoperative infections, and postoperative spinal cord injury aggravated symptoms. Postoperative thoracic spine magnetic resonance imaging and computed tomography examinations of all patients showed that the spinal cord was fully decompressed without any residual pressure. Back pain and radicular pain were relieved significantly, and spinal cord function (Nurick, mJOA, and Oswestry Disability Index scores) was obviously restored. The mJOA recovery rate at the 2-year follow-up was 78.3% in average. Limitations: This is an observational cohort study with relative small sample and short-term follow-up. Conclusions: Ultrasonic assisted full-endoscopic en block resection of ossified ligamentum flavum is a safe and effective minimally invasive spine surgery for thoracic myelography caused by thoracic ossified ligamentum flavum.