Percutaneous computed tomography fluoroscopy-guided conformal ultrasonic ablation of vertebral tumors in a rabbit tumor model. Laboratory investigation.

OBJECT: Radiofrequency ablation (RFA) has proven to be effective for treatment of malignant and benign tumors in numerous anatomical sites outside the spine. The major challenge of using RFA for spinal tumors is difficulty protecting the spinal cord and nerves from damage. However, conforming ultrasound energy to match the exact anatomy of the tumor may provide successful ablation in such sensitive locations. In a rabbit model of vertebral body tumor, the authors have successfully ablated tumors using an acoustic ablator placed percutaneously via computed tomography fluoroscopic (CTF) guidance. METHODS: Using CTF guidance, 12 adult male New Zealand White rabbits were injected with VX2 carcinoma cells in the lowest lumbar vertebral body. At 21 days, a bone biopsy needle was placed into the geographical center of the lesion, down which an acoustic ablator was inserted. Three multisensor thermocouple arrays were placed around the lesion to provide measurement of tissue temperature during ablation, at thermal doses ranging from 100 to 1,000,000 TEM (thermal equivalent minutes at 43°C), and tumor volumes were given a tumoricidal dose of acoustic energy. Animals were monitored for 24 hours and then sacrificed. Pathological specimens were obtained to determine the extent of tumor death and surrounding tissue damage. Measured temperature distributions were used to reconstruct volumetric doses of energy delivered to tumor tissue, and such data were correlated with pathological findings. RESULTS: All rabbits were successfully implanted with VX2 cells, leading to a grossly apparent spinal and paraspinal tissue mass. The CTF guidance provided accurate placement of the acoustic ablator in all tumors, as corroborated through gross and microscopic histology. Significant tumor death was noted in all specimens without collateral damage to nearby nerve tissue. Tissue destruction just beyond the margin of the tumor was noted in some but not all specimens. No neurological deficits occurred in response to ablation. Reconstruction of measured temperature data allowed accurate assessment of volumetric dose delivered to tissues. CONCLUSIONS: Using a rabbit intravertebral tumor model, the authors have successfully delivered tumoricidal doses of acoustic energy via a therapeutic ultrasound ablation probe placed percutaneously with CTF guidance. The authors have thus established the first technical and preclinical feasibility study of controlled ultrasound ablation of spinal tumors in vivo.

The evolution of intramedullary spinal cord tumor surgery.

OBJECTIVE: Resections of intramedullary spinal cord tumors were attempted as early as 1890. More than a century after these primitive efforts, profound advancements in imaging, instrumentation, and operative techniques have greatly improved the modern surgeon's ability to treat such lesions successfully, often with curative results. METHODS: We review the history of intramedullary spinal cord tumor surgery, as well as the evolution and advancement of technologies and surgical techniques that have defined the procedure over the past 100 years. RESULTS: Surgery to remove intramedullary spinal cord tumors has evolved to include sophisticated imaging equipment to pinpoint tumor location, laser scalpel systems to provide precise incisions with minimal damage to surrounding tissue, and physiological monitoring to detect and prevent intraoperative motor deficits. CONCLUSION: Modern surgical devices and techniques have developed dramatically with the availability of new technologies. As a result, continual advancements have been achieved in intramedullary spinal cord tumor surgery, thus increasing the safety and effectiveness of tumor resection, and progressively improving the overall outcomes in patients undergoing such procedures.

Radiographic and clinical evaluation of free-hand placement of C-2 pedicle screws. Clinical article.

OBJECT: Stabilization of the cervical spine can be challenging when instrumentation involves the axis. Fixation with C1-2 transarticular screws combined with posterior wiring and bone graft placement has yielded excellent fusion rates, but the technique is technically demanding and places the vertebral arteries (VAs) at risk. Placement of screws in the pars interarticularis of C-2 as described by Harms and Melcher has allowed rigid fixation with greater ease and theoretically decreases the risk to the VA. However, fluoroscopy is suggested to avoid penetration laterally, medially, and superiorly to avoid damage to the VA, spinal cord, and C1-2 joint, respectively. The authors describe how, after meticulous dissection of the C-2 pars interarticularis, such screws can be placed accurately and safely without the use of fluoroscopy. METHODS: Prospective follow-up was performed in 55 consecutive patients who underwent instrumented fusion of C-2 by a single surgeon. The causes of spinal instability and type and extent of instrumentation were documented. All patients underwent preoperative CT or MR imaging scans to determine the suitability of C-2 screw placement. Intraoperatively, screws were placed following dissection of the posterior pars interarticularis. Postoperative CT scans were performed to determine the extent of cortical breach. Patients underwent clinical follow-up, and complications were recorded as vascular or neurological. A CT-based grading system was created to characterize such breaches objectively by location and magnitude via percentage of screw diameter beyond the cortical edge (0 = none; I = < 25% of screw diameter; II = 26-50%; III = 51-75%; IV = 76-100%). RESULTS: One-hundred consecutive screws were placed in the pedicle of the axis by a single surgeon using external landmarks only. In 10 cases, only 1 screw was placed because of a preexisting VA anatomy or bone abnormality noted preoperatively. In no case was screw placement aborted because of complications noted during drilling. Early complications occurred in 2 patients and were limited to 1 wound infection and 1 transient C-2 radiculopathy. There were 15 total breaches (15%), 2 of which occurred in the same patient. Twelve breaches were lateral (80%), and 3 were superior (20%). There were no medial breaches. The magnitude of the breach was classified as I in 10 cases (66.7% of breaches), II in 3 cases (20% of breaches), III in 1 case (6.7%), and IV in 1 case (6.7%). CONCLUSIONS: Free-hand placement of screws in the C-2 pedicle can be done safely and effectively without the use of intraoperative fluoroscopy or navigation when the pars interarticularis/pedicle is assessed preoperatively with CT or MR imaging and found to be suitable for screw placement. When breaches do occur, they are overwhelmingly lateral in location, breach < 50% of the screw diameter, and in the authors' experience, are not clinically significant.

Treatment of diffuse intrinsic brainstem gliomas: failed approaches and future strategies.

Diffuse intrinsic pontine gliomas constitute ~ 60-75% of tumors found within the pediatric brainstem. These malignant lesions present with rapidly progressive symptoms such as cranial nerve, long tract, or cerebellar dysfunctions. Magnetic resonance imaging is usually sufficient to establish the diagnosis and obviates the need for surgical biopsy in most cases. The prognosis of the disease is dismal, and the median survival is < 12 months. Resection is not a viable option. Standard therapy involves radiotherapy, which produces transient neurological improvement with a progression-free survival benefit, but provides no improvement in overall survival. Clinical trials have been conducted to assess the efficacy of chemotherapeutic and biological agents in the treatment of diffuse pontine gliomas. In this review, the authors discuss recent studies in which systemic therapy was administered prior to, concomitantly with, or after radiotherapy. For future perspective, the discussion includes a rationale for stereotactic biopsies as well as possible therapeutic options of local chemotherapy in these lesions.

Diagnosis and management of sacral tumors.

Sacral tumors pose significant challenges to the managing physician from diagnostic and therapeutic perspectives. Although these tumors are often diagnosed at an advanced stage, patients may benefit from good clinical outcomes if an aggressive multidisciplinary approach is used. In this review, the epidemiology, clinical presentation, imaging characteristics, treatment options, and published outcomes are discussed. Special attention is given to the specific anatomical constraints that make tumors in this region of the spine more difficult to effectively manage than those in the mobile portions of the spine.

Current technological advances of bipolar coagulation.

BACKGROUND: Heat has been used to control bleeding for thousands of years. In the 1920s, this concept was applied to the development of electrosurgical instruments and was used to control hemorrhage during surgical procedures. In the time that has passed since its first use, electrosurgery has evolved into modern-day bipolar technology, involving a diverse group of coagulation instruments. METHODS: We review the evolution and advances in electrosurgery, specifically bipolar coagulation, and the current technologies available for intraoperative hemorrhage control. RESULTS: Electrosurgery has evolved to include highly accurate devices that deliver thermal energy via nonstick and noncontact methods. Over time, the operative range of coagulation instruments has increased dramatically with the incorporation of irrigating pathways, a wide range of instrument tips to perform various functions, and the application of bipolar technology to microforceps and microscissors for minimally invasive procedures. CONCLUSION: Electrosurgical devices and techniques, especially bipolar coagulation, have developed significantly with the availability of new technologies. This has led to better intraoperative coagulation control while minimizing iatrogenic damage associated with heat spread and tissue adherence, thus potentially improving outcomes for neurosurgical procedures.

Evaluation of factors associated with postoperative infection following sacral tumor resection.

OBJECT: Resection of sacral tumors has been shown to improve survival, since the oncological prognosis is commonly correlated with the extent of local tumor control. However, extensive soft-tissue resection in close proximity to the rectum may predispose patients to wound complications and infection. To identify potential risk factors, a review of clinical outcomes for sacral tumor resections over the past 5 years at a single institution was completed, paying special attention to procedure-related complications. METHODS: Between 2002 and 2007, 46 patients with sacral tumors were treated with surgery. Demographic data, details of surgery, type of tumor, and patient characteristics associated with surgical site infections (SSIs) were collected; these data included presence of the following variables: diabetes, obesity, smoking, steroid use, previous surgery, previous radiation, cerebrospinal fluid leak, number of spinal levels exposed, instrumentation, number of surgeons scrubbed in to the procedure, serum albumin level, and combined anterior-posterior approach. Logistic regression analysis was implemented to find an association of such variables with the presence of SSI. RESULTS: A total of 46 patients were treated for sacral tumor resections; 20 were male (43%) and 26 were female (57%), with an average age of 46 years (range 11-83 years). Histopathological findings included the following: chordoma in 19 (41%), ependymoma in 5 (11%), rectal adenocarcinoma in 5 (11%), giant cell tumor in 4 (9%), and other in 13 (28%). There were 18 cases of wound infection (39%), and 2 cases of repeat surgery for tumor recurrence (1 chordoma and 1 giant cell tumor). Factors associated with increased likelihood of infection included previous lumbosacral surgery (p = 0.0184; odds ratio [OR] 7.955) and number of surgeons scrubbed in to the operation (p = 0.0332; OR 4.018). Increasing age (p = 0.0864; OR 1.031), presence of complex soft-tissue reconstruction (p = 0.118; OR 3.789), and bowel and bladder dysfunction (p = 0.119; OR 2.667) demonstrated a trend toward increased risk of SSI. CONCLUSIONS: Patients undergoing sacral tumor surgery may be at greater risk for developing wound complications due to the extensive soft-tissue resections often required, especially with the increased potential for contamination from the neighboring rectum. In this study, it appears that previous lumbosacral surgery, number of surgeons scrubbed in, patient age, bowel and bladder dysfunction, and complex tissue reconstruction may predict those patients more prone to developing postoperative SSIs.

Minimally invasive direct repair of lumbar spondylolysis with a pedicle screw and hook construct.

Object Lumbar spondylolysis occurs in approximately 6% of the population and presents with localized mechanical back pain, often in young athletes. Surgical treatment may involve decompression, lumbar intersegmental fusion, or direct repair of pars defects. Although such open procedures may effectively resolve symptoms, minimal-access approaches may additionally decrease collateral damage to soft tissues, allowing young, active patients to resume athletic activities sooner. In this study, the authors review their experience repairing bilateral lumbar spondylolyses with screw and hook constructs placed via a minimal-access approach. Methods Five consecutive pediatric patients with bilateral L-5 spondylolysis were treated. Bilateral incisions (2.5 cm) were made over L-5. Exposure was maintained with bilateral expandable tubular retractor systems. Pedicle screws were placed in the L-5 pedicles and attached to hooks under the L-5 laminae. A direct repair was performed at the pars defect. Clinical characteristics, operative variables, and postoperative outcomes were collected. Results All 5 patients underwent surgery; 4 were male (80%) and 1 was female (20%), and the mean age was 15.8 years (range 15-17 years). The mean estimated blood loss and duration of surgery were 37 ml (range 15-75 ml) and 1.94 hours (range 1-3 hours), respectively. Postoperative hospital stays ranged from 1 to 3 days (mean 1.8 days). The only complication occurred in 1 patient who experienced minor superficial wound breakdown. All patients have experienced resolution of symptoms at this preliminary stage, which has continued over an 8-month follow-up period. Conclusions Lumbar spondylolysis can be adequately and safely treated via minimal-access surgical repair of the pars interarticularis by using pedicle screws and rod-hook constructs. This approach may decrease the collateral soft tissue damage common to open dissections, and may be ideal for young, active surgical candidates.

Supraciliary keyhole craniotomy for brain abscess debridement.

OBJECT: Treatments for brain abscesses have typically involved invasive craniotomies followed by debridement. These methods often require large incisions with vast exposure and may be associated with high morbidity rates. For supraorbital lesions of the anterior and middle cranial fossa, minimally invasive craniotomies may limit exposure and decrease surgically related morbidity while allowing adequate debridement and decompression. The authors report their experience in treating frontal epidural abscesses in pediatric patients through minimally invasive supraciliary craniotomies over a 4-year period. METHODS: Three pediatric patients with frontal epidural abscesses underwent minimally invasive debridement procedures. Each procedure consisted of a supraciliary incision and a small craniotomy to expose the abscess. All patients underwent pre- and postoperative radiological evaluation including computed tomography and magnetic resonance imaging. Data were collected on preoperative characteristics, operative management, and postoperative outcomes. RESULTS: Two patients were male and 1 patient was female. The ages of the patients ranged from 6 to 10 years (mean 8 years). A frontal abscess was diagnosed in all patients, and all were treated surgically without perioperative complications. Microbes cultured postoperatively included methicillin-resistant Staphylococcus aureus in 2 patients and Staphylococcus viridans in 1 patient. The mean follow-up duration was 12.3 months. No neurological or vascular complications were noted during follow-up. All patients were treated with antibiotics postoperatively and experienced resolution of symptoms and excellent outcomes. CONCLUSIONS: Frontal epidural abscesses can be adequately and safely debrided via a minimally invasive supraciliary craniotomy. This approach has a cosmetic benefit and may decrease approach-related morbidity.

Laminar screw fixation of the axis.

OBJECT: Laminar fixation of the axis with crossing bilateral screws has been shown to provide rigid fixation with a theoretically decreased risk of vertebral artery damage compared with C1-2 transarticular screw fixation and C-2 pedicle screw fixation. Some studies, however, have shown restricted rigidity of such screws compared with C-2 pedicle screws, and others note that anatomical variability exists within the posterior elements of the axis that may have an impact on successful placement. To elucidate the clinical impact of such screws, the authors report their experience in placing C-2 laminar screws in adult patients over a 2-year period, with emphasis on clinical outcome and technical placement. METHODS: Sixteen adult patients with cervical instability underwent posterior cervical and cervicothoracic fusion procedures at our institution with constructs involving C-2 laminar screws. Eleven patients were men and 5 were women, and they ranged in age from 28 to 84 years (mean 57 years). The reasons for fusion were degenerative disease (9 patients) and treatment of trauma (7 patients). In 14 patients (87.5%) standard translaminar screws were placed, and in 2 (12.5%) an ipsilateral trajectory was used. All patients underwent preoperative radiological evaluation of the cervical spine, including computed tomography scanning with multiplanar reconstruction to assess the posterior anatomy of C-2. Anatomical restrictions for placement of standard translaminar screws included a deeply furrowed spinous process and/or an underdeveloped midline posterior ring of the axis. In these cases, screws were placed into the corresponding lamina from the ipsilateral side, allowing bilateral screws to be oriented in a more parallel, as opposed to perpendicular, plane. All patients were followed for >2 years to record rates of fusion, instrumentation failure, and other complications. RESULTS: Thirty-two screws were placed without neurological or vascular complications. The mean follow-up duration was 27.3 months. Complications included 2 revisions, one for pseudarthrosis and the other for screw pullout, and 3 postoperative infections. CONCLUSIONS: Placement of laminar screws into the axis from the standard crossing approach or via an ipsilateral trajectory may allow a safe, effective, and durable means of including the axis in posterior cervical and cervicothoracic fusion procedures.

Microsurgical removal of intramedullary spinal cord gliomas in a rat spinal cord decreases onset to paresis, an animal model for intramedullary tumor treatment.

OBJECTIVE: Intramedullary spinal cord tumors (IMSCT) pose significant challenges given their recurrence rate and limited treatment options. Using our previously described rat model of IMSCT, we describe a technique for microsurgical tumor resection and present the functional and histopathological analysis of tumor progression. METHODS: Twenty-four Fischer 344 rats were randomized into two groups. All animals received a 5-microl intramedullary injection of 9L gliosarcoma cells. Animals were evaluated daily for signs of paralysis using the Basso, Beattie, and Bresnahan (BBB) scale. Group 1 continued with daily assessments using the BBB scale following tumor implantation, but received no further treatment. Group 2 underwent surgical removal of intramedullary tumor on postoperative day five. At a BBB score less than 5 (e.g., functional paraplegia), all animals of both groups were killed and sent for histopathological analysis. RESULTS: Group 1 had a median onset of functional hind limb paraplegia at 15 +/- 1.0 days. Group 2 had a median onset of hind limb paresis at 53 +/- 0.46 days. Hematoxylin-eosin cross-sections confirmed the presence of intramedullary 9L tumor invading the spinal cord in both groups. CONCLUSION: Animals with 9L IMSCTs consistently developed hind limb paraplegia in a reliable and reproducible manner. Animals undergoing microsurgical resection of IMSCT had a significant delay in the onset of functional paraplegia compared to the untreated controls. These findings suggest that this model may mimic the behavior of IMSCTs following operative resection in humans and thus may be used to examine efficacy of new treatment options for high-grade intramedullary tumors.

Antibiotic-impregnated shunt catheters for the treatment of infantile hydrocephalus.

INTRODUCTION: Antibiotic-impregnated shunt (AIS) components decrease shunt infections by preventing bacterial colonization that occurs during implantation. Despite studies showing improved efficacy in preventing infection however, concern still exists regarding using AIS components in infants, especially premature ones. In this study, clinical outcomes were assessed in infants with hydrocephalus (<1 year) following AIS placement. METHODS: A prospective observational study was conducted involving pediatric patients <1 year of gestational age with hydrocephalus who underwent placement of AIS components (ventriculoperitoneal, ventriculoatrial, and cystoperitoneal) as initial treatments, shunt revision surgery, or following previous placement of a ventricular access device (VAD, Rickman reservoir). Measured outcomes included: infection, shunt revision surgery, and complications. RESULTS: Seventy-four infants underwent 108 AIS procedures, and all were followed for over 9 months. Twenty-seven patients (36.5%) possessed previous VADs. Average weight and gestational age at birth were 1,976 g (range: 560-3,500 g) and 32.8 weeks (range: 23-41 weeks), respectively. The average age at the time of surgery was 14.6 weeks (range: 1 day to 50 weeks). Five infections occurred in 5 patients (4.6% of procedures, 6.75% of patients), 60% of which were very premature (<32 weeks). Thirty-three patients (44.6%) required shunt revision surgery, 5 (15%) for infection and 28 (85%) for malfunction. Three cerebrospinal fluid leaks occurred perioperatively without significant sequelae, and no mortalities occurred from the procedures. CONCLUSION: AIS systems can safely be used to treat hydrocephalus in pediatric patients <1 year old, even for those with a history of prematurity. One possible therapeutic application for such premature patients may be the incorporation of antibiotic impregnation into VADs or ventriculosubgaleal components to treat infants with hydrocephalus prior to definitive CSF shunt placement.

Spinal stenosis surgery in pediatric patients with achondroplasia.

OBJECT: Achondroplasia is a hereditary form of dwarfism caused by a defect in endochondral bone formation, resulting in skeletal abnormalities including short stature, shortened limb bones, macrocephaly, and small vertebral bodies. In the pediatric population, symptomatic spinal stenosis occurs at all spinal levels due to the abnormally narrow bone canal. In this study, clinical outcomes were assessed in children with achondroplasia after spinal canal decompression. METHODS: A retrospective review was conducted involving pediatric patients with heterozygous achondroplasia and symptomatic stenosis after decompressive procedures at the authors' institution within a 9-year period. Measured outcomes included resolution of symptoms, need for repeated surgery, presence of fusion, development of deformity, and complications. Forty-four pediatric patients underwent a total of 60 decompressive procedures. The average patient age at surgery was 12.7 years (range 5-21 years). Forty-nine operations were performed for initial treatment of stenosis, and 11 were performed as revision surgeries on previously operated levels. A large proportion of patients (> 60%) required additional cervicomedullary decompressions, most often preceding the symptoms of spinal stenosis. Of the initial procedures, decompression locations included 32 thoracolumbar (65%), 10 lumbar (20%), four cervical (8%), two cervicothoracic (4%), and one thoracic (2%). Forty-three of the decompressive procedures (72%) included spinal fusion procedures. Of the 11 revisions, five were fusion procedures for progressive deformity at levels previously decompressed but not fused (all thoracolumbar), five were for decompressions of symptomatic junctional stenosis with extension of fusion, and one was for repeated decompression at the same level due to recurrence of symptomatic stenosis. CONCLUSIONS: Decompression of the spinal canal in pediatric patients with achondroplasia can be accomplished safely with significant clinical benefit. Patients with a history of cervicomedullary compression may be at an increased risk of developing symptomatic stenosis prior to adolescence. Fusion procedures are recommended in patients with a large decompression overlying a thoracolumbar kyphosis to avoid progressive postoperative deformity.