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1.  Mid-Term Results of Computer-Assisted Cervical Pedicle Screw Fixation 
Asian Spine Journal  2014;8(6):759-767.
Study Design
A retrospective study.
Purpose
The present study aimed to evaluate mid-term results of cervical pedicle screw (CPS) fixation for cervical instability.
Overview of Literature
CPS fixation has widely used in the treatment of cervical spinal instability from various causes; however, there are few reports on mid-term surgical results of CPS fixation.
Methods
Record of 19 patients who underwent cervical and/or upper thoracic (C2-T1) pedicle screw fixation for cervical instability was reviewed. The mean observation period was 90.2 months. Evaluated items included Japanese Orthopaedic Association (JOA) score and C2-7 lordotic angle before surgery and at 5 years after surgery. Postoperative computerized tomography was used to determine the accuracy of screw placement. Visual analog scale (VAS) for neck pain and radiological evidence of adjacent segment degeneration (ASD) at the 5-year follow-up were also evaluated.
Results
Mean JOA score was significantly improved from 9.0 points before surgery to 12.8 at 5 years after surgery (p=0.001). The C2-7 lordotic angle of the neutral position improved from 6.4° to 7.8° at 5 years after surgery, but this was not significant. The major perforation rate was 5.0%. There were no clinically significant complications such as vertebral artery injury, spinal cord injury, or nerve root injury caused by any screw perforation. Mean VAS for neck pain was 49.4 at 5 years after surgery. The rate of ASD was 21.1%.
Conclusions
Our mid-term results showed that CPS fixation was useful for treating cervical instability. Severe complications were prevented with the assistance of a computed tomography-based navigation system.
doi:10.4184/asj.2014.8.6.759
PMCID: PMC4278981  PMID: 25558318
Cervical pedicle screw; Cervical instability; Mid-term results; Adjacent segment degeneration
2.  Comparison of Spinous Process-Splitting Laminectomy versus Conventional Laminectomy for Lumbar Spinal Stenosis 
Asian Spine Journal  2014;8(6):768-776.
Study Design
Seventy-five patients who had been treated for lumbar spinal stenosis (LSS) were reviewed retrospectively.
Purpose
Invasion into the paravertebral muscle can cause major problems after laminectomy for LSS. To address these problems, we performed spinous process-splitting laminectomy. We present a comparative study of decompression of LSS using 2 approaches.
Overview of Literature
There are no other study has investigated the lumbar spinal instability after spinous process-splitting laminectomy.
Methods
This study included 75 patients who underwent laminectomy for the treatment of LSS and who were observed through follow-ups for more than 2 years. Fifty-five patients underwent spinous process-splitting laminectomy (splitting group) and 20 patients underwent conventional laminectomy (conventional group). We evaluated the clinical and radiographic results of each surgical procedure.
Results
Japanese Orthopaedic Association score improved significantly in both groups two years postoperatively. The following values were all significantly lower, as shown with p-values, in the splitting group compared to the conventional group: average operating time (p=0.002), postoperative C-reactive protein level (p=0.006), the mean postoperative number of days until returning to normal body temperature (p=0.047), and the mean change in angulation 2 years postoperatively (p=0.007). The adjacent segment degeneration occurred in 6 patients (10.9%) in the splitting group and 11 patients (55.0%) in the conventional group.
Conclusions
In this study, the spinous process-splitting laminectomy was shown to be less invasive and more stable for patients with LSS, compared to the conventional laminectomy.
doi:10.4184/asj.2014.8.6.768
PMCID: PMC4278982  PMID: 25558319
Lumbar spinal stenosis; Spinous process-splitting laminectomy; Postoperative low back pain; Paravertebral muscle, posterior approach
3.  Myxopapillary Ependymoma of the Cauda Equina in a 5-Year-Old Boy 
Asian Spine Journal  2014;8(6):846-851.
Myxopapillary ependymoma in childhood typically occurs in the central nervous system. There are few surgical cases of myxopapillary ependymoma of the cauda equina in children. We report a case of myxopapillary ependymoma of the cauda equina in a 5-year-old boy, who presented with leg pain and abnormal gait. Subtotal resection surgery was performed. Following the subtotal tumor resection, follow-up magnetic resonance imaging evaluation showed a recurrent tumor. As a result, we performed a second subtotal tumor resection and followed with postoperative radiation therapy. No further evidence of the disease has been noted elsewhere in the patient in over ten years of follow-up. Myxopapillary ependymoma of the cauda equina in a young boy was improved by subtotal tumor resection and postoperative radiation therapy.
doi:10.4184/asj.2014.8.6.846
PMCID: PMC4278994  PMID: 25558331
Myxopapillary ependymoma; Child; Radiation therapy; Cauda equina
4.  Cervical Pedicle Screw Fixation Combined with Laminoplasty for Cervical Spondylotic Myelopathy with Instability 
Asian Spine Journal  2012;6(4):241-248.
Study Design
A retrospective study.
Purpose
To evaluate the surgical results of cervical pedicle screw (CPS) fixation combined with laminoplasty for treating cervical spondylotic myelopathy (CSM) with instability.
Overview of Literature
Cervical fixation and spinal cord decompression are required for CSM patients with instability. However, only a few studies have reported on CPS fixation combined with posterior decompression for unstable CSM patients.
Methods
Thirteen patients that underwent CPS fixation combined with laminoplasty for CSM with instability were evaluated in this study. We assessed the clinical and radiological results of the surgical procedures. The Japanese Orthopedic Association (JOA) scoring system was used to evaluate the clinical results. The percentages of sli p, difference in sli p angle between maximum flexion and maximum extension of unstable intervertebrae, and perforation rate of CPS were evaluated.
Results
The mean JOA scores before surgery, immediately after surgery, and at final follow-up were 9.1, 13.3, and 12.6, respectively. The mean percentages of sli p before surgery, immediately after surgery, and at final follow-up were 9.1%, 3.2%, and 3.5%, respectively; there were significant improvements immediately after surgery and at final follow-up. The difference in sli p angle between the maximum flexion and maximum extension of the unstable intervertebrae changed from 9.0° before surgery to 1.6° at the final follow-up. The perforation rate of CPS was 10.9%.
Conclusions
The results suggest that CPS fixation combined with laminoplasty is an effective surgical procedure for treating CSM with instability.
doi:10.4184/asj.2012.6.4.241
PMCID: PMC3530698  PMID: 23275807
Cervical spondylosis; Myelopathy; Instability; Cervical fixation
5.  Computer-assisted C1-C2 Transarticular Screw Fixation "Magerl Technique" for Atlantoaxial Instability 
Asian Spine Journal  2012;6(3):168-177.
Study Design
A retrospective study.
Purpose
To evaluate the surgical results of computer-assisted C1-C2 transarticular screw fixation for atlantoaxial instability and the usefulness of the navigation system.
Overview of Literature
We used a computed tomography (CT)-based computer navigation system in planning and screw insertion in Magerl's procedure, which provides the most rigid atlantoaxial fusion, to avoid risk of vertebral artery (VA) tear by avoiding high-riding VA during screw insertion.
Methods
Twenty patients who underwent atlantoaxial fusion under the CT-based navigation system were studied. The mean observation period was 33.5 months. The evaluated items included the existence of VA stenosis by preoperative magnetic resonance angiography, surgical time, blood loss volume, Japanese Orthopaedic Association (JOA) score and Ranawat's pain criteria before surgery and at final follow-up, postoperative screw position evaluated by CT, and bony fusion.
Results
The mean operation time was 205 minutes, with the mean blood loss volume of 242 ml. The mean JOA score was 11.6 points before surgery and 13.7 at final follow-up. Occipital and/or cervical pain presented before operation was remitted or resolved in all patients. Evaluation of screw insertion by CT revealed correct penetration to atlantoaxial joints, with a perforation rate of 2.6%. There was no complication, including VA tear, and all patients who were followed-up during one year or more after surgery achieved bony fusion. Some subjects who appeared inappropriate for surgery from CT images were assessed as eligible for surgery based on the evaluation results obtained using the navigation system.
Conclusions
It was demonstrated that the CT-based navigation system is an effective support device for Magerl's procedure.
doi:10.4184/asj.2012.6.3.168
PMCID: PMC3429607  PMID: 22977696
Atlantoaxial joint; Atlantoaxial instability; CT-based computer navigation system; C1-C2 transarticular screw fixation
6.  Perforation Rates of Cervical Pedicle Screw Insertion by Disease and Vertebral Level 
Background:
Different perforation rates for cervical pedicle screws by disease are expected in relation to bone quality and pedicle morphology; however, no report comparing pedicle screw perforation rate by disease had previously been published. This study investigated the perforation rates of pedicle screws inserted to cervical pedicle by disease and vertebral level using a CT-based navigation system.
Materials/Methods:
Fifty-three patients who underwent cervical pedicle screw insertion using CT based navigation system were studied. Diseases included rheumatoid arthritis (RA) (24 cases), destructive spondyloarthropathy (DSA) (10), cervical spondylotic myelopathy (CSM) (9), spine tumor (6), and cervical spondylotic myelopathy associated with athetoid cerebral palsy (CP) (4). Screw perforation rates for cervical pedicle screws were studied. Major perforation was defined as perforation 50% of screw diameter or more.
Results:
Major perforation rate by disease from C3 to C7 was as follows: spine tumor (0/24, 0%), RA (2/59, 3.4%), DSA (3/65, 4.6%), CP (2/20, 10.0%), and CSM (6/40, 15.0%). There were no clinically important complications such as vertebra arterial injury, spinal cord injury, or nerve root injury caused by any screw perforation. Major perforation rate by vertebral level was: C2(2/30, 6.7%), C3(4/49, 8.2%), C4(6/43, 14.0%), C5(1/32, 3.1%), C6(1/41, 2.4%), and C7(1/45, 2.2%), showing highest rate for C4, followed by C3.
Conclusions:
Cervical pedicle screw perforation rate by disease was higher in CSM compared to RA and DSA. The perforation rate by vertebral level was higher for C4 and C3, in this order.
doi:10.2174/1874325001004010142
PMCID: PMC2864428  PMID: 20448816
Cervical pedicle screw; image guidance; perforation rate.

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