Minimally Invasive Stereotactic Separation Surgery for Resection of Metastatic Spine Lesion: A Feasibility Study

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Introduction The current treatment of spinal metastasis consists of algorithms combining reconstructive surgical and radiation modalities. Recently, the concept of separation surgery followed by adjuvant stereotactic radiosurgery (SRS) was shown to be a safe and effective treatment to achieve long-term local tumor control. We examined the possibility of a minimally invasive approach to separation surgery first in a cadaveric feasibility study and then in a patient cohort with spinal metastasis in conjunction with intraoperative computer-assisted navigation. Methods A cadaveric study using standard minimally invasive access systems examined the feasibility of spinal cord decompression in the thoracic and lumbar spine. Subsequently, 10 patients (7 males and 3 females) with spinal metastasis underwent minimally invasive separation surgery (MISS) and percutaneous pedicle screw fixation using intraoperative navigation or standard fluoroscopy. The O-arm three-dimensional imaging with stereotactic navigation was used intraoperatively to localize and guide the resection of the metastatic spinal tumors. All patients were at least 3/5 strength in the lower extremities preoperatively. Pre- and postoperative CT scan and CT myelography were used to evaluate the degree of decompression. Endpoints included neurological function, operative time, estimated blood loss, incision length, hospital stay duration, and complications. Results The cadaveric study demonstrated a proof of principle with a wide decompression of the spinal cord. For the operative cases, the postoperative imaging demonstrated excellent separation that meets the requirements for safe SRS. All patients remained at/or improved their neurological baseline with excellent pain control. One patient incurred a perioperative complication (pulmonary embolism). The mean estimated blood loss was 290 mL. The mean incision length was 4.9 cm. The operative time mean was 5.2 hours and the mean length of stay was 7.5 days. Conclusion MISS for spinal metastasis allows for a circumferential decompression of the spinal cord and safe postoperative SRS. In addition, we demonstrated the efficacy of intraoperative navigation in guiding the resection. Future prospective enrollment of patients can help to determine which patients would be ideal candidates for MISS and if the smaller incision and an enduring faster healing process can allow a faster start of radiation and chemotherapy.