Jean-Marc Voyadzis

The rising psoas sign: an analysis of preoperative imaging characteristics of aborted minimally invasive lateral interbody fusions at L4-5

Minimally invasive lateral interbody fusion for the treatment of degenerative disc disease, spondylolisthesis, or scoliosis is becoming increasingly popular. The approach at L4-5 carries the highest risk of nerve injury given the proximity of the lumbar plexus and femoral nerve. The authors present 3 cases that were aborted during the approach because of pervasive electromyography responses throughout the L4-5 disc space. Preoperative imaging characteristics of psoas muscle anatomy in all 3 cases are analyzed and discussed. In all cases, the psoas muscle on axial views was rising away from the vertebral column as opposed to its typical location lateral to it. Preoperative evaluation of psoas muscle anatomy is important. A rising psoas muscle at L4-5 on axial imaging may complicate a lateral approach.

MINIMALLY INVASIVE POSTERIOR OSTEOTOMIES

OBJECTIVESurgery for thoracolumbar deformity can lead to significant muscle injury, excessive blood loss, and severe postoperative pain. The aim of the following studies was to determine the feasibility of minimally invasive posterior thoracic corpectomy and thoracolumbar osteotomy techniques for deformity in human cadavers and select clinical cases. METHODSHuman cadaveric specimens were procured for thoracic corpectomy and Smith-Petersen and pedicle subtraction osteotomy using a minimally invasive approach. Post-procedural computed tomography was used to assess the degree of decompression following corpectomy and the extent of bone resection after osteotomy. Pre and post-osteotomy closure Cobb angles were measured to evaluate the degree of correction achieved. RESULTSThe minimally invasive lateral extracavitary approach for thoracic corpectomy provided adequate exposure and allowed excellent spinal canal decompression while minimizing tissue disruption. Nearly complete osteotomies of both types could be achieved through a tubular retractor with a modest change in Cobb angle. CONCLUSIONThese techniques may play a role in deformity surgery for select cases with further technological advancements.

Fiducial-free CyberKnife stereotactic body radiation therapy (SBRT) for single vertebral body metastases: acceptable local control and normal tissue tolerance with 5 fraction approach

This retrospective analysis examines the local control and toxicity of five-fraction fiducial-free CyberKnife stereotactic body radiation therapy (SBRT) for single vertebral body (VB) metastases. All patients had favorable performance status (ECOG 0–1), oligometastatic disease, and no prior spine irradiation. A prescribed dose of 30–35 Gy was delivered in five fractions to the planning target volume (PTV) using the CyberKnife with X-sight spine tracking. Suggested maximum spinal cord and esophagus point doses were 30 and 40 Gy, respectively. A median 30 Gy (IQR, 30–35 Gy) dose was delivered to a median prescription isodose line of 70% (IQR, 65–77%) to 20 patients. At 34 months median follow-up (IQR, 25–40 months) for surviving patients, the 1- and 2-year Kaplan–Meier local control estimates were 80 and 73%, respectively. Two of the five local failures were infield in patients who had received irradiation to the gross tumor volume and three were paravertebral failures just outside the PTV in patients with prior corpectomy. No local failures occurred in patients who completed VB radiation alone. The 1- and 2-year Kaplan–Meier overall survival estimates were 80 and 57%, respectively. Most deaths were attributed to metastatic disease; one death was attributed to local recurrence. The mean maximum point doses were 26.4 Gy (SD, 5.1 Gy) to the spinal cord and 29.1 Gy (SD, 8.9 Gy) to the esophagus. Patients receiving maximum esophagus point doses greater than 35 Gy experienced acute dysphagia (Grade I/II). No spinal cord toxicity was documented. Five-fraction fiducial-free CyberKnife SBRT is an acceptable treatment option for newly diagnosed VB metastases with promising local control rates and minimal toxicity despite the close proximity of such tumors to the spinal cord and esophagus. A prospective study aimed at further enhancing local control by targeting the intact VB and escalating the total dose is planned.

Minimally Invasive Lumbar Transfacet Screw Fixation in the Lateral Decubitus Position After Extreme Lateral Interbody Fusion A Technique and Feasibility Study

Study Design: Prospective evaluation of 10 patients undergoing minimally invasive lumbar interbody fusion for degenerative disk disease and radiculopathy. Objective: To assess the feasibility of percutaneous lumbar transfacet screw fixation in the lateral decubitus position after lateral interbody fusion. Summary of Background Data: Lumbar interbody fusion is commonly performed for the treatment of degenerative disk disease with associated radiculopathy due to foraminal stenosis or disk protrusion. Minimally invasive techniques, such as the lateral interbody fusion, have been developed to achieve this while reducing operative morbidity. Subsequent vertebral fixation is best achieved with a pedicle screw and rod construct in the prone position. Transfacet screw placement has been shown to have near biomechanical equivalence and may reduce operative time and morbidity if placed while the patient remains in the lateral decubitus position. Methods: Ten patients with back pain and radicular pain due to single-level degenerative disk disease at L3-L4 or L4-L5 underwent minimally invasive lateral interbody arthrodesis with placement of bilateral percutaneous transfacet screws in the lateral decubitus position. Patients had close perioperative follow-up including recordings of intraoperative blood loss, operative time, and hospital length of stay. Clinical outcome measures including visual analog scores (VAS) were assessed preoperatively and at last follow-up with a minimum of 6 months. Dynamic radiographs were obtained at last follow-up to evaluate the instrumentation and fusion rate. Results: The procedure was well tolerated by all patients. Mean operative time was 2 hours and 42 minutes. Mean blood loss was 26.5 mL. Mean hospital length of stay was 46.5 hours. Nine of 10 patients had good-to-excellent relief of their preoperative back pain and leg pain. Mean preoperative VAS score for back pain was 8.9 and for leg pain was 8. At a mean follow-up of 8.2 months, mean postoperative VAS score for back pain was 0.9 and for leg pain was 0.9. There were no complications. One patient suffered persistent mild leg dysesthesias. There were no instances of graft or screw dislodgement on follow-up imaging. Conclusions: Minimally invasive percutaneous transfacet screw fixation can be performed safely and effectively in the lateral decubitus position. This is an attractive option for posterior percutaneous fixation that can lead to a reduction of operative time and surgical morbidity in select cases.

Minimally invasive resection of lumbar synovial cysts from a contralateral approach

Synovial cysts of the lumbar spine result from degeneration of the facet capsule and often mimic symptoms commonly seen with herniated intervertebral discs. In symptomatic patients, the prevalence of synovial cysts may be as high as 10%. Although conservative management is possible, the majority of patients will require resection. Traditional procedures for lumbar synovial cyst resection use an ipsilateral approach requiring partial or complete resection of the ipsilateral facet complex, possibly leading to further destabilization. A contralateral technique using minimally invasive tubular retractors for synovial cyst resection avoids facet disruption. The authors report 2 cases of a minimally invasive synovial cyst resection via a contralateral laminotomy. In both cases, complete resection of the cyst was achieved while sparing the facet joint.

Minimally invasive approach for far lateral disc herniations: results from 20 patients.

BACKGROUND Far lateral lumbar disc herniations, while infrequent, are a substantial cause of morbidity causing painful radicular syndromes often accompanied by a motor or sensory deficit. Surgical treatment can be challenging technically because of unfamiliar lateral anatomy and the importance of adjacent osseous structures, notably the pars interarticularis and facet joint. METHOD The traditional approach for a far lateral lumbar disc herniation involves a midline incision, wide lateral subperiosteal exposure and partial removal of these structures with the potential for iatrogenic instability. A paramedian approach to the lateral compartment of the disc space is advantageous because it directly targets the pathology. The use of recently developed minimally invasive retractor systems decreases tissue dissection and blood loss and improves postoperative recovery. RESULTS AND DISCUSSION We present a series of 20 patients who underwent far lateral discectomy using a minimally invasive muscle splitting approach.

Minimally invasive lateral approach to the thoracolumbar junction for corpectomy

Diseases that affect the thoracolumbar junction present a unique challenge to the spine surgeon. Various techniques have been described to treat this clinical entity from the anterior, lateral, or posterior direction. These can be associated with significant morbidity due to extensive tissue dissection, blood loss, and postoperative pain leading to a lengthy recovery. The use of a tubular retractor allows the surgeon to minimize tissue dissection and potentially reduce approach-related morbidity while obviating the need for an approach surgeon for exposure. The surgical technique of a minimally invasive lateral approach to the thoracolumbar junction for corpectomy is described in detail and two illustrative patients are presented.

Cadaveric evaluation of minimally invasive posterolateral thoracic corpectomy: a comparison of 3 approaches.

Study Design A cadaver study comparing 3 different minimally invasive approaches to the anterior thoracic spine. Objective To assess the feasibility of minimally invasive thoracic corpectomy from a posterolateral approach and to compare surgical results from 3 approaches. Summary of Background Data Traditional posterolateral approaches to the thoracic spine are effective but are associated with a high rate of operative morbidity. Methods Thoracic corpectomies were performed using a modified tubular retractor starting at 3, 6, and 9 cm off of midline. Postoperative computed tomography scans were performed and analyzed to assess the extent of corpectomy and ventral decompression. Results From 3 to 6 to 9 cm, a significant difference in extent of corpectomy (65.8%, 81.5%, and 82.6%, P=0.02) and ventral decompression (83.6%, 90.4%, 94.6%, P=0.05) was noted between 3 cm and the more lateral approaches. The 9 cm approach required more rib resection and average working distances of 8.4 to 11.3 cm, which made the procedure more difficult technically and less suited to the length of standard instruments. Conclusions Minimally invasive thoracic corpectomy is feasible and a 6 cm approach off of midline appears optimal.

Thoracic Spine Localization Using Preoperative Placement of Fiducial Markers and Subsequent CT. A Technical Report

STUDY DESIGN A retrospective case series evaluating the use of fiducial markers with subsequent computed tomography (CT) or CT myelography for intraoperative localization. OBJECTIVE To evaluate the safety and utility of preoperative fiducial placement, confirmed with CT myelography, for intraoperative localization of thoracic spinal levels. SUMMARY OF BACKGROUND DATA Thoracic spine surgery is associated with serious complications, not the least of which is the potential for wrong-level surgery. Intraoperative fluoroscopy is often used but can be unreliable due to the patients body habitus and anatomical variation. METHODS Sixteen patients with thoracic spine pathology requiring surgical intervention underwent preoperative fiducial placement at the pedicle of the level of interest in the interventional radiology suite. CT or CT myelogram was then done to evaluate fiducial location relative to the level of pathology. Surgical treatment followed at a later date in all patients. RESULTS All patients underwent preoperative fiducial placement and CT or CT myelography, which was done on an outpatient basis in 14 of the 16 patients. Intraoperatively, fiducial localization was easily and quickly done with intraoperative fluoroscopy leading to correct localization of spinal level in all cases. All patients had symptomatic improvement following surgery. There were no complications from preoperative localization or operative intervention. CONCLUSIONS Preoperative placement of fiducial markers confirmed with a CT or CT myelogram allows for reliable and fast intraoperative localization of the spinal level of interest with minimal risks and potential complications to the patient. In most cases, a noncontrast CT should be sufficient. This should be an equally reliable means of localization while further decreasing potential for complications. CT myelography should be reserved for pathology that is not evident on noncontrast CT. Accuracy of localization is independent of variations in rib number or vertebral segmentation. The technique is a safe, reliable, and rapid means of localizing spinal level during surgery.