The effect of minimally invasive dorsal cervical decompression for myelopathy on spinal alignment and range of motion.

OBJECTIVE: Minimally invasive dorsal cervical decompression (miDCD) has been reported as a novel alternative to open dorsal decompression techniques such as laminectomy, laminoplasty, or laminectomy and fusion. Only limited data have been presented regarding the effects of a minimally invasive approach on cervical motion and alignment. The object of the current study is to provide a more comprehensive analysis of radiographic outcomes following miDCD. PATIENTS AND METHODS: Thirty-five patients who had undergone miDCD for myelopathy were included. Exclusion criteria included prior cervical spine surgery, prior cervical spine fracture, fusion of the cervical spine during miDCD, and/or acute spinal cord injury. Analysis of x-rays included the following data elements: degrees of flexion, degrees of extension, and total range of motion; C2-C7 angle as a measure of cervical lordosis; C2-C7 sagittal vertical axis; effective lordosis; and C7 slope. Patient reported outcome measures included neck Visual Analog Score (VAS), Neck Disability Index (NDI), SF-12 Physical Component Score (PCS), SF-12 Mental Component Score (MCS), Nurick score, and modified Japanese Orthopedic Association Myelopathy scale (mJOA). RESULTS: Pre-operative to post-operative comparisons of all radiographic parameters - including total range of motion, C2-C7 Cobb angle, C2-C7 sagittal vertical axis, effective lordosis, and C7 slope angle - remained stable. Several clinical outcomes demonstrated statistical improvement, namely neck VAS, Nurick score, mJOA, NDI, and SF-12 PCS. CONCLUSIONS: miDCD can maintain cervical range of motion and alignment better than traditional laminectomy or laminoplasty techniques.

Great Vessel Excursion: Prone Versus Supine Position.

BACKGROUND: It is theorized that pedicle screws could be placed into the anterior vertebral cortex to increase biomechanical strength by 20% to 25%. Although stereotactic navigational tools allow for accurate docking of spinal implants, no data exist regarding operative positioning as it relates to great vessel alignment. Our hypothesis is that the great vessels fall anteriorly, with prone positioning providing a safer margin for implantation of screws from a posterior approach. METHODS: Volunteers underwent magnetic resonance imaging of the spine. Twenty healthy volunteers, affiliated with the academic medical center performing the study, underwent magnetic resonance imaging in both the supine and prone positions. Measurements were taken of the distance (mm) from the projected tip of a pedicle screw to the neighboring great vessels.Measurements were made at every other vertebral level from T3 to L5 by bisecting the pedicle in the transverse and sagittal planes and projecting the trajectory of a screw to the anterior cortex. We then evaluated great vessel position in relationship to the tip of the projected pedicle screw at the anterior cortex in the supine and prone orientations. RESULTS: The vessels were found to lie in a range of 2 to 10 mm from the anterior cortex. The comparison between the supine and prone positions showed that the great vessels in the lumbar region are held securely by the surrounding soft tissue. However, in the thoracic spine, anterior excursion does occur, just not as we expected. The aorta moves anteriorly while prone by 1.4 to 5 mm; however, its movement causes it to slide forward along the vertebra, shortening the distance to the anterior cortex. As a result, the screw trajectory is in a riskier geographic location. In the thoracolumbar area, the inferior vena cava translates 1.7 to 2.9 mm. CONCLUSIONS: These data suggest that the risks of vascular injury from anterior cortical fixation of the vertebra using pedicle screws placed posteriorly in the prone position are apparent. In the lumbar region, the upper thoracic region around the aortic arch, and the thoracolumbar junction the great vessels remain close to the vertebra. While in the mid-thoracic region, the aorta moves closer to the area of screw penetration anteriorly when the subject is prone. CLINICAL RELEVANCE: Spine surgeons commonly attempt pedicle screw placement into the anterior cortex of the vertebral body. Our study helps elucidate the inherent risks of this technique due to vessel positioning when prone.

Minimally Invasive Surgical Management of Thoracic Ossification of the Ligamentum Flavum Associated with X-linked Hypophosphatemia.

BACKGROUND: X-linked hypophosphatemia (XLH) is the most common inherited form of renal phosphate wasting and inherited rickets. Patients have hyperplasia of fibrochondrocytes in tendons and ligaments, causing the structures to thicken and calcify. Thickening of the lamina, hypertrophy of facet joints, and calcification of spinal ligaments are sequelae of this condition and can result in central or foraminal stenosis that compresses nerve roots or the spinal cord. We present a case of XLH with calcification of the ligamentum flavum in which the patient was operated on using minimally invasive posterior decompression. CASE DESCRIPTION: A 49-year-old man with a history of XLH presented to our emergency department with symptomatic myelopathy from multilevel thoracic stenosis. Radiographically, the calcified ligamentum flavum appeared to be the cause of the stenosis at various levels. The patient underwent a posterior decompression at the levels of compression, T4-T5, T8-T9, T9-T10, and T11-T12, via a minimally invasive spine surgery approach. Intraoperatively, the ligamentum flavum appeared to be both calcified and the source of spinal compression. Postoperatively, the patient experienced neurologic and radiographic improvement. CONCLUSION: Patients with a history of XLH and multilevel symptomatic spine stenosis can be treated successfully and safely with a minimally invasive posterior decompression.

Low pressure traumatic epidural hematoma in a child with a prior hemispherectomy: Case report.

A 2½-year-old male child with a prior history of a left anatomic hemispherectomy to treat refractory epilepsy fell down two steps, striking his head on the ipsilateral side of the hemispherectomy. He presented with non-consolable crying and emesis. CT scan of the head demonstrated a left frontal epidural hematoma beneath the site of his prior craniectomy. The patient was initially treated by close observation. However, due to an increase in the hematoma from 29.5 to 49.3 ml over a 12-hour period along with the patient's lack of clinical improvement, surgical evacuation was performed. Intraoperatively, the source of the hemorrhage was found to be the skull fracture. Postoperatively, he returned to his neurologic baseline and was discharged home on postoperative day 3.