Naoki Higashiyama

Multistep pedicle screw insertion procedure with patient-specific lamina fit-and-lock templates for the thoracic spine: clinical article.

OBJECT Pedicle screw fixation is a standard procedure of spinal instrumentation, but accurate screw placement is essential to avoid injury to the adjacent structures, such as the vessels, nerves, and viscera. The authors recently developed an intraoperative screw guiding method in which patient-specific laminar templates were used, and verified the accuracy of the multistep procedure in the thoracic spine. METHODS Preoperative bone images of the CT scans were analyzed using 3D/multiplanar imaging software and the trajectories of the screws were planned. Plastic templates with screw guiding structures were created for each lamina by using 3D design and printing technology. Three types of templates were made for precise multistep guidance, and all templates were specially designed to fit and lock on the lamina during the procedure. Plastic vertebra models were also generated and preoperative screw insertion simulation was performed. Surgery was performed using this patient-specific screw guide template system, and the placement of screws was postoperatively evaluated using CT scanning. RESULTS Ten patients with thoracic or cervicothoracic pathological entities were selected to verify this novel procedure. Fifty-eight pedicle screws were placed using the screw guide template system. Preoperatively, each template was found to fit exactly and to lock on the lamina of the vertebra models, and screw insertion simulation was successfully performed. Intraoperatively the templates also fit and locked on the patient lamina, and screw insertion was completed successfully. Postoperative CT scans confirmed that no screws violated the cortex of the pedicles, and the mean deviation of the screws from the planned trajectories was 0.87 ± 0.34 mm at the coronal midpoint section of the pedicles. CONCLUSIONS The multistep, patient-specific screw guide template system is useful for intraoperative pedicle screw navigation in the thoracic spine. This simple and economical method can improve the accuracy of pedicle screw insertion and reduce the operating time and radiation exposure of spinal fixation surgery.

Novel Dural Closure Technique Using Polyglactin Acid Sheet Prevents Cerebrospinal Fluid Leakage after Spinal Surgery

OBJECTIVE: Extradural or subcutaneous cerebrospinal fluid (CSF) leakage is a common complication after spinal surgery and is associated with the risks of poor wound healing, meningitis, and pseudomeningocele. Numerous methods to prevent postoperative CSF leakage are available, but pressure-tight dural closure remains difficult, especially with synthetic surgical membranes. The efficacy of a novel dural closure technique was assessed by detecting extradural or subcutaneous CSF leakage on magnetic resonance imaging. METHODS: The novel dural closure technique using absorbable polyglactin acid sheet and fibrin glue and the conventional procedure using only fibrin glue were evaluated retrospectively by identifying extradural or subcutaneous CSF leakage on magnetic resonance imaging scans in the acute (2–7 d) and chronic (3–6 mo) postoperative stages after spinal intradural surgery in 53 patients. RESULTS: The incidence of extradural and subcutaneous CSF leakage was significantly lower (P < 0.05) in the acute (20%) and chronic (0%) stages using polyglactin acid sheet and fibrin glue in 15 patients compared with that in the acute (81%) and chronic (24%) stages using only fibrin glue in 38 patients. One patient in the fibrin glue-only group required repair surgery for cutaneous CSF leakage. CONCLUSION: The combination of polyglactin acid sheet and fibrin glue can achieve water-tight closure after spinal intradural surgery and can minimize the risk of intractable postoperative CSF leakage. This simple, economical technique is recommended for dural closure after spinal intradural surgery.

β-Tricalcium phosphate promotes bony fusion after anterior cervical discectomy and fusion using titanium cages.

Study Design. Retrospective consecutive cohort study. Objective. To study the effectiveness of &bgr;-tricalcium phosphate (&bgr;-TCP) granules as a packing material in the titanium cages for anterior cervical discectomy and fusion (ACDF), compared with the conventional hydroxyapatite (HA) granules. Summary of Background Data. ACDF using titanium cages is a standard procedure for the treatment of cervical spinal degenerative diseases. Synthetic bone substitutes are widely used to pack the titanium cage to augment intervertebral bony fusion, but the efficacy has not been confirmed. Methods. Fusion condition was evaluated on lateral radiographs and computed tomography. Complete fusion of the treated segments was defined by three criteria: movement of the spinous process at flexion and extension positions of less than 3 mm, bony bridging between vertebral bodies, and absence of the halo around the titanium cage. The evaluation was performed at 6 months, 1 year, and 2 years after surgery. Results. Intervertebral fusion was studied in patients who underwent ACDF using &bgr;-TCP (93 segments of 57 patients) or HA (72 segments of 48 patients) packing of cylindrical titanium cages. Complete fusion rate at 6 months and 1 year was significantly better in the &bgr;-TCP group (46% at 6 months and 69% at 1 year) than in the HA group (24% at 6 months and 49% at 1 year), but the rate was similar at 2 years in the &bgr;-TCP group (94%) and the HA group (90%). There were no material-related adverse effects. Conclusion. Satisfactory final fusion rates were obtained after ACDF using both &bgr;-TCP- and HA-packed titanium cages. &bgr;-TCP showed higher fusion rate in the early stage after surgery and can be recommended as a bone substitute for ACDF with titanium cages.

A novel screw guiding method with a screw guide template system for posterior C-2 fixation: clinical article.

OBJECT Accurate insertion of C-2 cervical screws is imperative; however, the procedures for C-2 screw insertion are technically demanding and challenging, especially in cases of C-2 vertebral abnormality. The purpose of this study is to report the effectiveness of the tailor-made screw guide template (SGT) system for placement of C-2 screws, including in cases with abnormalities. METHODS Twenty-three patients who underwent posterior spinal fusion surgery with C-2 cervical screw insertion using the SGT system were included. The preoperative bone image on CT was analyzed using multiplanar imaging software. The trajectory and depth of the screws were designed based on these images, and transparent templates with screw guiding cylinders were created for each lamina. During the operation, after templates were engaged directly to the laminae, drilling, tapping, and screwing were performed through the templates. The authors placed 26 pedicle screws, 12 pars screws, 6 laminar screws, and 4 C1-2 transarticular screws using the SGT system. To assess the accuracy of the screw track under this system, the deviation of the screw axis from the preplanned trajectory was evaluated on postoperative CT and was classified as follows: Class 1 (accurate), a screw axis deviation less than 2 mm from the planned trajectory; Class 2 (inaccurate), 2 mm or more but less than 4 mm; and Class 3 (deviated), 4 mm or more. In addition, to assess the safety of the screw insertion, malpositioning of the screws was also evaluated using the following grading system: Grade 0 (containing), a screw is completely within the wall of the bone structure; Grade 1 (exposure), a screw perforates the wall of the bone structure but more than 50% of the screw diameter remains within the bone; Grade 2 (perforation), a screw perforates the bone structures and more than 50% of the screw diameter is outside the pedicle; and Grade 3 (penetration), a screw perforates completely outside the bone structure. RESULTS In total, 47 (97.9%) of 48 screws were classified into Class 1 and Grade 0, whereas 1 laminar screw was classified as Class 3 and Grade 2. Mean screw deviations were 0.36 mm in the axial plane (range 0.0-3.8 mm) and 0.30 mm in the sagittal plane (range 0.0-0.8 mm). CONCLUSIONS This study demonstrates that the SGT system provided extremely accurate C-2 cervical screw insertion without configuration of reference points, high-dose radiation from intraoperative 3D navigation, or any registration or probing error evoked by changes in spinal alignment during surgery. A multistep screw placement technique and reliable screw guide cylinders were the key to accurate screw placement using the SGT system.

Accurate and Simple Screw Insertion Procedure with Patient-Specific Screw Guide Templates for Posterior C1-C2 Fixation.

Study Design. Prospective clinical trial of the screw insertion method for posterior C1-C2 fixation utilizing the patient-specific screw guide template technique. Objective. To evaluate the efficacy of this method for insertion of C1 lateral mass screws (LMS), C2 pedicle screws (PS), and C2 laminar screws (LS). Summary of Background Data. Posterior C1LMS and C2PS fixation, also known as the Goel-Harms method, can achieve immediate rigid fixation and high fusion rate, but the screw insertion carries the risk of injury to neuronal and vascular structures. Dissection of venous plexus and C2 nerve root to confirm the insertion point of the C1LMS may also cause problems. We have developed an intraoperative screw guiding method using patient-specific laminar templates. Methods. Preoperative bone images of computed tomography (CT) were analyzed using three-dimensional (3D)/multiplanar imaging software to plan the trajectories of the screws. Plastic templates with screw guiding structures were created for each lamina using 3D design and printing technology. Three types of templates were made for precise multistep guidance, and all templates were specially designed to fit and lock on the lamina during the procedure. Surgery was performed using this patient-specific screw guide template system, and placement of the screws was postoperatively evaluated using CT. Results. Twelve patients with C1-C2 instability were treated with a total of 48 screws (24 C1LMS, 20 C2PS, 4 C2LS). Intraoperatively, each template was found to exactly fit and lock on the lamina and screw insertion was completed successfully without dissection of the venous plexus and C2 nerve root. Postoperative CT showed no cortical violation by the screws, and mean deviation of the screws from the planned trajectories was 0.70 ± 0.42 mm. Conclusion. The multistep, patient-specific screw guide template system is useful for intraoperative screw navigation in posterior C1-C2 fixation. This simple and economical method can improve the accuracy of screw insertion, and reduce operation time and radiation exposure of posterior C1-C2 fixation surgery. Level of Evidence: 3

The Availability of the Screw Guide Template System for the Insertion of Mid-Cervical Pedicle Screw âTechnical Note

Abstract Study background: Although cervical pedicle screw method is the most stable instrumentation, which is useful for reconstruction of unstable or deformed cervical spine, to insert cervical pedicle screw accurately is sometimes challenging at the risk of the neurovascular injuries due to the anatomical features of cervical pedicles. The purpose of this study is to introduce our Screw Guide Template (SGT) system developed to insert mid-cervical pedicle screws accurately and safely with less risk. Method: Preoperatively, the bone image on CT was analyzed by the multiplanar imaging software and then the trajectory and the depth of the screws were designed three-dimensionally. Three types of transparent templates were created for each lamina: location template, drill guide template and screw guide template. During the operations, after engaging the templates directly with the laminae, three steps; drilling, tapping, and screwing were performed with each template. The screws were inserted accurately as we planned, which was confirmed by postoperative CT. Case presentation: Three cases underwent posterior spinal fusion surgeries with mid-cervical pedicle screw insertion using the SGT system. The location of all screws were perfectly matched the trajectory planned preoperatively in Case 1 and 2. While, the improper templates engagement due to inadequate par spinal muscle retraction lead to the mal-positions of two screws in Case 3. Conclusion: We demonstrated the availability of the SGT system as intraoperative screw navigation for cervical pedicle screw insertion in mid-cervical spine. Proper engaging templates and adequate muscles traction play an important role for the SGT system through the procedure.

Limaprost Alfadex Improves Myelopathy Symptoms in Patients With Cervical Spinal Canal Stenosis

Study Design. Myelopathy symptoms were prospectively studied in patients with cervical spinal canal stenosis (CSCS), using objective grading systems and stabilometry, to examine the effect of administration of prostaglandin E1 derivative limaprost alfadex (limaprost). Objective. Myelopathy scores/grades and stabilometry parameters were evaluated before, and 1 and 3 months after starting the limaprost treatment. Summary and Background Data. Limaprost is a potent vasodilator and antiplatelet agent and has been used to treat the symptoms of lumbar spinal canal stenosis. The action presumably involves increased blood flow in the compressed cauda equina. Limaprost can also increase blood flow in the compressed spinal cord, but effects on myelopathy symptoms in patients with CSCS have not been established. Methods. This study examined 21 patients with mild spondylotic CSCS based on neurologic findings and compression of the cervical spinal cord on magnetic resonance imaging. Japanese Orthopedic Association score, grip and release test, and finger escape sign were measured, and stabilometry was performed by independent examiners, before, and 1 and 3 months after starting the oral limaprost treatment. Results. Most patients experienced amelioration of the symptoms at 1 month after starting the treatment. Mean Japanese Orthopedic Association score and grip and release count were significantly improved and finger escape sign grade was higher in some patients. Stabilometry area with eyes closed and Romberg rate were also significantly improved. These improvements were maintained at 3 months. Conclusion. The efficacy of oral limaprost administration for patients with CSCS was confirmed by objective scoring and quantitative data.