Assessing the Accuracy and Safety Thresholds of Patient-Specific Screw Guide Template System in Cervical and Thoracic Spine Surgeries Using DAST Measurements.

Introduction: To analyze the reliability of the newly developed patient-specific Screw Guide Template (SGT) system as an intraoperative navigation device for spinal screw insertion. Methods: We attempted to place 428 screws for 51 patients. The accuracy of the screw track was assessed by deviation of the screw axis from the preplanned trajectory on postoperative CT. The safety of the screw insertion was evaluated by the bone breach of the screw. The bone diameter available for screw trajectory (DAST) was measured, and the relations to the bone breach were analyzed. Results: In the inserted screws, 98.4% were defined as accurate, and 94.6% were contained in the target bone. In the cervical spine, the screw deviation between breaching (0.57 mm) and contained screws (0.43 mm) did not significantly differ, whereas DAST for breaching screws (3.62 mm) was significantly smaller than contained screws (5.33 mm) (p<0.001). Cervical screws with ≥4.0 mm DAST showed a significantly lower incidence of bone breach (0.4%) than ≤3.9 mm DAST (28.3%) (p<0.001). In the thoracic spine, screw deviation and DAST had significant differences between breaching (1.54 mm, 4.41 mm) and contained (0.75 mm, 6.07 mm) (p<0.001). The incidence of the breach was significantly lower in thoracic screws with ≥5.0 mm (1.9%) than ≤4.9 (21.9%) DAST (p<0.001). Conclusions: This study demonstrated that our SGT system could support precise screw insertion for 98.4% accuracy and 94.6% safety. DAST was recommended to be ≥4.0 and ≥5.0 mm in the cervical and thoracic spines for safe screw insertion.

The factors of deterioration in long-term clinical course of lumbar spinal canal stenosis after successful conservative treatment.

BACKGROUND: The treatment of lumbar spinal canal stenosis (LSS) depends on symptom severity. In the absence of severe symptoms such as severe motor disturbances or bowel and/or urinary dysfunction, conservative treatment is generally the first choice for the treatment of LSS. However, we experienced cases of worsening symptoms even after successful conservative treatment. The purpose of this study is to investigate the long-term clinical course of LSS following successful conservative treatment and analyze the prognostic factors associated with symptom deterioration. METHODS: The study included 60 LSS patients (34 females and 26 males) whose symptoms were relieved by conservative treatment between April 2007 and March 2010 and who were followed up for 5 years or longer. The mean age at admission was 64.8 ± 8.5 years (range, 40-85 years old), and the mean follow-up period was 7.3 years (range, 5.8-9.5 years). We defined "deterioration" of symptoms as the shortening of intermittent claudication more than 50 m compared with those at discharge or the occurrence or progression of lower limb paralysis, and "poor outcome" as the deterioration within 5 years after discharge. The long-term outcome of conservative treatment for LSS was analyzed by Kaplan-Meier analysis. Furthermore, logistic regression analysis was performed to reveal the risk factors of poor outcome for clinical classification, severe intermittent claudication (≤ 100 m), lower limb muscle weakness, vertebral body slip (≥ 3 mm), scoliosis (Cobb angle ≥ 10°), block on myelography, and redundant nerve roots of the cauda equina. RESULTS: Thirty-four (56.7%) patients preserved their condition at discharge during the follow-up, whereas 26 patients (43.3%) showed deterioration. Sixteen patients had a decreased intermittent claudication distance, and 10 patients had newly developed or progressive paralysis. The probability of preservation was maintained at 68.3% at 5 years after discharge. Logistic regression analysis demonstrated that only severe intermittent claudication (≤ 100 m) was a significant risk factor of a poor outcome (p = 0.005, odds ratio = 6.665). CONCLUSIONS: The patients with severe intermittent claudication should be carefully followed up because those are the significant deterioration candidates despite the success in conservative treatment.

Prospective Multicenter Study of a Multistep Screw Insertion Technique Using Patient-Specific Screw Guide Templates for the Cervical and Thoracic Spine.

STUDY DESIGN: A prospective clinical study of a multistep screw insertion method using a patient-specific screw guide template system (SGTS) for the cervical and thoracic spine. OBJECTIVE: To evaluate the efficacy of SGTS for inserting screws into the cervical and thoracic spine. SUMMARY OF BACKGROUND DATA: Posterior screw fixation is a standard procedure for spinal instrumentation; however, screw insertion carries the risk of injury to neuronal and vascular structures. METHODS: Preoperative bone images of the computed tomography (CT) scans were analyzed using 3D/multiplanar imaging software, and the screw trajectories were planned. 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 the templates were specially designed to fit and lock onto the lamina during the procedure. In addition, plastic vertebra models were generated, and preoperative screw insertion simulation was performed. This patient-specific SGTS was used to perform the surgery, and CT scanning was used to postoperatively evaluate screw placement. RESULTS: Enrolled to verify this procedure were 103 patients with cervical, thoracic, or cervicothoracic pathologies. The SGTS were used to place 813 screws. Preoperatively, each template was found to fit exactly and to lock onto the lamina of the vertebra models. In addition, intraoperatively, the templates fit and locked onto the patient lamina, and the screws were inserted successfully. Postoperative CT scans confirmed that 801 screws (98.5%) were accurately placed without cortical violation. There were no injuries to the vessels or nerves. CONCLUSION: The multistep, patient-specific SGTS is useful for intraoperative pedicle screw (PS) navigation in the cervical and thoracic spine. This method improves the accuracy of PS insertion and reduces the operating time and radiation exposure during spinal fixation surgery. LEVEL OF EVIDENCE: 3.

Postoperative Walking Ability of Non-ambulatory Cervical Myelopathy Patients.

STUDY DESIGN: A retrospective analysis. OBJECTIVE: The aim of this study was to clarify the postoperative improvement of walking ability and prognostic factors in nonambulatory patients with cervical myelopathy. SUMMARY OF BACKGROUND DATA: Many researchers have reported the surgical outcome in compressive cervical myelopathy. However, regarding severe gait disturbance,, it has not been clarified yet how much improvement can be expected. METHODS: One hundred thirty-one nonambulatory patients with cervical myelopathy were treated surgically and followed for an average of 3 years. Walking ability was graded according to the lower-extremity function subscore (L/E subscore) in Japanese Orthopedic Association score. We divided patients based on preoperative L/E subscores: group A, L/E subscore of 1 point (71 patients); and group B, 0 or 0.5 point (60 patients). The postoperative walking ability was graded by L/E subscore: excellent, ≥2 points; good, 1.5 points; fair, 1 point; and poor, 0.5 or 0 points. We compared preoperative and postoperative scores. The cutoff value of disease duration providing excellent improvement was investigated. RESULTS: Overall, 50 patients were graded as excellent (38.2%), and 21 patients were graded as good (16.0%). In group B, 17 patients (28.3%) were graded as excellent. Seventeen patients who were graded as excellent had shorter durations of myelopathic symptoms and/or gait disturbance (7.9 and 3.8 months respectively) than the others (29.5 and 8.9 months, respectively) (P < 0.05). Receiver-operating characteristic curve showed that the optimal cutoff values of the duration of myelopathic symptoms and gait disturbance providing excellent improvement were 3 and 2 months, respectively. CONCLUSION: Even if the patients were nonambulatory, 28.3% of them became able to walk without support after operation. If a patient becomes nonambulatory within 3 months from the onset of myelopathy or 2 months from the onset of gait disturbance, surgical treatment should be performed immediately to raise the possibility to improve stable gait. LEVEL OF EVIDENCE: 3.

Dysphagia After Occipitothoracic Fusion is Caused by Direct Compression of Oropharyngeal Space Due to Anterior Protrusion of Mid-cervical Spine.

STUDY DESIGN: This was a retrospective study. OBJECTIVE: To investigate the relationship among the craniocervical alignment, the oropharyngeal space, and the incidence of dysphagia after occipitothoracic fusion (OTF). SUMMARY OF BACKGROUND DATA: Craniocervical malalignment after OTF is one of a trigger of dysphagia. However, there has been no logical explanation for the etiology yet. METHODS: A total of 32 patients who underwent OTF (5 male, 27 female) were reviewed. Following 4 parameters on the lateral cervical radiogram, pharyngeal tilt angle (PTA); the angle between the McGregor's line and the line that links the center of C2 pedicle and the center of vertebral body at the apex of cervical sagittal curvature, diameter of oropharyngeal airway space (dPS), O-C2 angle, and C2-C7 angle were measured at follow-up and then the relationship of these parameters and their influence to the incidence of dysphagia were analyzed. RESULTS: Six of 32 cases (18.8%) exhibited postoperative dysphagia. ROC curves showed that PTA and dPS had moderate accuracy for the predictor of the dysphagia after OTF with the area under the curve (AUC) of 0.76 and 0.86 respectively, whereas O-C2 angle had low accuracy with AUC of 0.69 and C2-C7 angle was almost useless for prediction of postoperative dysphagia with AUC of 0.51. A multiple linear regression analysis showed that only PTA was significantly correlated with dPS (ß=0.822, P=0.014), whereas the O-C2 angle (ß=0.101, P=0.779) and C2-C7 angle (ß=0.352, P=0.157) had negligibly small influence on dPS. CONCLUSIONS: Our results demonstrated strong relationships between PTA and the value of dPS, and the incidence of dysphagia. As PTA reflects anterior protrusion of mid-cervical spine, these results indicated that dysphagia after OTF is caused by narrowing of oropharyngeal space due to direct compression from anteirorly protruded mid-cervical spine.

The Prediction and Prevention of Dysphagia After Occipitospinal Fusion by Use of the S-line (Swallowing Line).

STUDY DESIGN: Clinical case series and risk factor analysis of dysphagia after occipitospinal fusion (OSF). OBJECTIVE: The aim of this study was to develop new criteria to avoid postoperative dysphagia by analyzing the relationship among the craniocervical alignment, the oropharyngeal space, and the incidence of dysphagia after OSF. SUMMARY OF BACKGROUND DATA: Craniocervical malalignment after OSF is considered to be one of the primary triggers of postoperative dysphagia. However, ideal craniocervical alignment has not been confirmed. METHODS: Thirty-eight patients were included. We measured the O-C2 angle (O-C2A) and the pharyngeal inlet angle (PIA) on the lateral cervical radiogram at follow-up. PIA is defined as the angle between McGregor's line and the line that links the center of the C1 anterior arch and the apex of cervical sagittal curvature. The impact of these two parameters on the diameter of pharyngeal airway space (PAS) and the incidence of the dysphagia were analyzed. RESULTS: Six of 38 cases (15.8%) exhibited the dysphagia. A multiple regression analysis showed that PIA was significantly correlated with PAS (ß = 0.714, P = 0.005). Receiver-operating characteristic curves showed that PIA had a high accuracy as a predictor of the dysphagia with an AUC (area under the curve) of 0.90. Cases with a PIA less than 90 degrees showed significantly higher incidence of dysphagia (31.6%) than those with a 90 or more degrees of PIA (0.0%) (P = 0.008). CONCLUSION: Our results indicated that PIA had the high possibility to predict postoperative dysphagia by OSF with the condition of PIA <90°. Based on these results, we defined "Swallowing-line (S-line)" for the reference of 90° of PIA. S-line (-) is defined as PIA <90°, where the apex of cervical lordosis protruded anterior to the "S-line," which should indicate the patient is at a risk of postoperative dysphagia. LEVEL OF EVIDENCE: 4.

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 ±â€Š0.42 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.

Preliminary Evaluation of the Pathomechanisms of Dysphagia After Occipitospinal Fusion: Kinematic Analysis by Videofluoroscopic Swallowing Study.

STUDY DESIGN: Kinematic analysis of swallowing function using videofluoroscopic swallowing study (VFSS). OBJECTIVES: The aims of this study were to analyze swallowing process in the patients who underwent occipitospinal fusion (OSF) and elucidate the pathomechanism of dysphagia after OSF. SUMMARY OF BACKGROUND DATA: Although several hypotheses about the pathomechanisms of dysphagia after OSF were suggested, there has been little tangible evidence to support these hypotheses since these hypotheses were based on the analysis of static radiogram or CT. Considering that swallowing is a compositive motion of oropharyngeal structures, the etiology of postoperative dysphagia should be investigated through kinematic approaches. METHODS: Each four patients with or without postoperative dysphagia (group D and N, respectively) participated in this study. For VFSS, all patients were monitored to swallow 5-mL diluted barium solution by fluoroscopy, and then dynamic passing pattern of the barium solution was analyzed. Additionally, O-C2 angle (O-C2A) was measured for the assessment of craniocervical alignment. RESULTS: O-C2A in group D was -7.5 degrees, which was relatively smaller than 10.3 degrees in group N (P = 0.07). In group D, all cases presented smooth medium passing without any obstruction at the upper cervical level regardless of O-C2A, whereas the obstruction to the passage of medium was detected at the apex of mid-lower cervical ocurvature, where the anterior protrusion of mid-lower cervical spine compressed directly the pharyngeal space. In group N, all cases showed smooth passing of medium through the whole process of swallowing. CONCLUSION: This study presented that postoperative dysphagia did not occur at the upper cervical level even though there was smaller angle of O-C2A and demonstrated the narrowing of the oropharyngeal space towing to direct compression by the anterior protrusion of mid-lower cervical spine was the etiology of dysphagia after OSF. Therefore, surgeon should pay attention to the alignment of mid-cervical spine as well as craniocervical junction during OSF. LEVEL OF EVIDENCE: 4.

C5 nerve palsy after posterior reconstruction surgery: predictive risk factors of the incidence and critical range of correction for kyphosis.

PURPOSE: It has been reported that the incidence of post-operative segmental nerve palsy, such as C5 palsy, is higher in posterior reconstruction surgery than in conventional laminoplasty. Correction of kyphosis may be related to such a complication. The aim of this study was to elucidate the risk factors of the incidence of post-operative C5 palsy, and the critical range of sagittal realignment in posterior instrumentation surgery. METHODS: Eighty-eight patients (mean age 64.0 years) were involved. The types of the disease were; 33 spondylosis with kyphosis, 27 rheumatoid arthritis, 17 athetoid cerebral palsy and 11 others. The patients were divided into two groups; Group P: patients with post-operative C5 palsy, and Group NP: patients without C5 palsy. The correction angle of kyphosis, and pre-operative diameter of C4/5 foramen on CT were evaluated between the two groups. Multivariate logistic regression analysis was used to determine the critical range of realignment and the risk factors affecting the incidence of post-operative C5 palsy. RESULTS: Seventeen (19.3 %) of the 88 patients developed C5 palsy. The correction angle of kyphosis in Group P (15.7°) was significantly larger than that in Group NP (4.5°). In Group P, pre-operative diameters of intervertebral foramen at C4/5 (3.2 mm) were significantly smaller than those in Group NP (4.1 mm). The multivariate analysis demonstrated that the risk factors were the correction angle and pre-operative diameter of the C4/5 intervertebral foramen. The logistic regression model showed a correction angle exceeding 20° was critical for developing the palsy when C4/5 foraminal diameter reaches 4.1 mm, and there is a higher risk when the C4/5 foraminal diameter is less than 2.7 mm regardless of any correction. CONCLUSIONS: This study has indicated the risk factors of post-operative C5 palsy and the critical range of realignment of the cervical spine after posterior instrumented surgery.

Safe and accurate midcervical pedicle screw insertion procedure with the patient-specific screw guide template system.

STUDY DESIGN: Clinical trial for midcervical pedicle screw insertion using a novel patient-specific intraoperative screw guiding device. OBJECTIVE: To evaluate the availability of the "Screw Guide Template" (SGT) system for insertion of midcervical pedicle screws. SUMMARY OF BACKGROUND DATA: Despite many efforts for accurate midcervical pedicle screw insertion, there still remain unacceptable rate of screw malpositioning that might cause neurovascular injuries. We developed patient-specific SGT system for safe and accurate intraoperative screw navigation tool and have reported its availability for the screw insertion to C2 vertebra and thoracic spine. METHODS: Preoperatively, the bone image on computed tomography was analyzed and the trajectories of the screws were designed in 3-dimensional format. Three types of 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, drilling, tapping, and screwing were performed with each template. We placed 80 midcervical pedicle screws for 20 patients. The accuracy and safety of the screw insertion by SGT system were evaluated using postoperative computed tomographic scan by calculation of screw deviation from the preplanned trajectory and evaluation of screw breach of pedicle wall. RESULTS: All templates fitted the laminae and screw navigation procedures proceeded uneventfully. All screws were inserted accurately with the mean screw deviation from planned trajectory of 0.29 ± 0.31 mm and no neurovascular complication was experienced. CONCLUSION: We demonstrated that our SGT system could support the precise screw insertion in midcervical pedicle. SGT prescribes the safe screw trajectory in a 3-dimensional manner and the templates fit and lock directly to the target laminae, which prevents screwing error along with the change of spinal alignment during the surgery. These advantages of the SGT system guarantee the high accuracy in screw insertion, which allowed surgeons to insert cervical pedicle screws safely. LEVEL OF EVIDENCE: 3.

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.

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.

Prospective cohort study of mild cervical spondylotic myelopathy without surgical treatment.

OBJECT: Because the main pathology of cervical spondylotic myelopathy (CSM) is spinal cord damage due to compression, surgical treatment is usually recommended to improve patient symptoms and prevent exacerbation. However, lack of clarity of prognosis in cases that present with insignificant symptoms, particularly those of mild CSM, lead one to question the veracity of this course of action. The purpose of this study was to elucidate the prognosis of mild CSM without surgical intervention by evaluation of clinical symptoms and MR imaging findings. METHODS: Sixty cases of mild CSM (42 males and 18 females, average age 57.2 years) presenting with scores of 13 or higher on the Japanese Orthopaedic Association (JOA) scale were treated initially by in-bed Good Samaritan cervical traction without surgery. These patients were enrolled between 1995 and 2003 and followed up periodically until the date of myelopathy deterioration or until the end of March 2009. The deterioration of myelopathy was defined as a decline in JOA score to less than 13 with a decrease of at least 2 points. As a prognostic factor, the authors used their classification of spinal cord shapes at their lateral sides on axial T1-weighted MR imaging. "Ovoid deformity" was classified as a situation in which both sides were round and convex, and "angular-edged deformity" where one or both sides exhibited an acute-angled lateral corner. The duration of follow-up was assessed as the tolerance rate of mild CSM using Kaplan-Meier survival analysis and compared between 2 groups classified by MR imaging findings. Furthermore, differences between groups were analyzed by various applications of the log-rank test. RESULTS: Of the initial 60 cases, follow-up records existed for 55, giving a follow-up rate of 91.7% (38 males and 17 females, average age 56.1 years). The mean JOA score at end point was 14.1, which was not statistically different from the mean of 14.5 at the initial visit. Deterioration in myelopathy was observed in 14 (25.5%) of 55 cases, whereas 41 (74.5%) of 55 cases maintained mild extent myelopathy without deterioration through the follow-up period (mean 94.3 months). The total tolerance rate of mild CSM was 70%. However, there was a significant difference in the tolerance rate between the cases with angular-edged deformity (58%) and cases with ovoid deformity (95%; p = 0.049). CONCLUSIONS: The tolerance rate of mild CSM was 70% in this study, which proved that the prognosis of mild CSM without surgical treatment was relatively good. However, the tolerance rate of the cases with angular-edged deformity was 58%. Therefore, surgical treatment should be considered when mild CSM cases show angular-edged deformity on axial MR imaging, even if patients lack significant symptoms.

Prospective study and multivariate analysis of the incidence of C5 palsy after cervical laminoplasty.

STUDY DESIGN: A prospective comparative study about the incidence of postoperative C5 palsy and multivariate analysis of the risk factors of C5 palsy. OBJECTIVE: To clarify the risk factors of occurrence of C5 palsy after laminoplasty (LP) by comparing the 2 surgical procedures of open-door and double-door LP prospectively. SUMMARY OF BACKGROUND DATA: The incidence of C5 palsy has been reported to average 4.6%, and there has been no difference of the incidence among surgical procedures. However, there were only indirect retrospective studies. METHODS: A total of 146 patients who underwent the LP procedure between 2006 and 2007 were studied prospectively. In 2006, the patients were assigned to undergo the open-door LP, and in 2007, they were assigned to undergo the double-door LP. The incidence of postoperative C5 palsy was compared prospectively between these 2 LP procedures, and the risk factors of C5 palsy were detected with multivariate logistic regression analysis. RESULTS: Postoperative C5 palsy occurred in 7 of 73 cases after open-door LP (9.6%) and in 1 of 73 cases after double-door LP (1.4%). The incidence of C5 palsy after open-door LP was statistically higher than the one after double-door LP (P = 0.029), and open-door LP was recognized as a significant risk factor for postoperative C5 paralysis (odds ratio: 69.6, P = 0.043). In addition, ossification of posterior longitudinal ligament (OPLL) was recognized as a significant risk factor for postoperative C5 paralysis (odds ratio: 43.8, P = 0.048). CONCLUSION: This study showed significant evidence indicating the higher risk of postoperative C5 palsy in open-door LP than double-door LP. Because OPLL as well as open-door LP were recognized as the risk factors of C5 palsy, asymmetric decompression by open-door LP might introduce imbalanced rotational movement of spinal cord and result in C5 palsy. We recommend double-door LP to minimize the postoperative C5 palsy, in particularly, if the patient has OPLL.

Matrix metalloproteinase (MMP)-3 gene up-regulation in a rat tail compression loading-induced disc degeneration model.

The rodent static compression loading-induced disc degeneration model still has important gaps among the radiographic, magnetic resonance imaging (MRI), and histological schemes and the acute and chronic expression of catabolic genes such as matrix metalloproteinase (MMP)-3. Our objectives were to assess the validity of a rat tail two-disc static compression model and to elucidate a representative catabolic marker, MMP-3 gene alterations, throughout the degenerative process. Static compression at 1.3 MPa for up to 56 days produced progressive disc height loss in radiographs, lower nucleus intensity on T2-weighted MRIs, and histomorphological degeneration. Real-time RT-PCR mRNA quantification showed significant MMP-3 up-regulation in nucleus pulposus cells from 7 days and a significantly progressive increase as the loading duration lengthened, with high correlations to radiological degenerative scores. Immunohistochemistry demonstrated progressively increased positive staining for MMP-3. These results validate this animal model for disc degeneration research. Progressive mRNA and protein-distributional up-regulations indicate the significant role of MMP-3 and its feasibility as a disc degenerative marker. This model should prove useful for investigating the pathomechanism and for evaluating molecular therapies for degenerative disc disease.

Fas ligand expression on human nucleus pulposus cells decreases with disc degeneration processes.

BACKGROUND: The intervertebral disc has been reported to be an immunologically privileged environment, possibly mediated by Fas ligand (FasL) expression. On the other hand, recent studies have shown the infiltration of host immune cells into the degenerated disc, which may indicate the failure of the immune-privilege feature of the disc with degeneration. However, the relationship between FasL expression and disc degeneration is still unclear. Therefore, the purpose of this study was to clarify the relationship between FasL expression and disc degeneration. METHODS: Ten human degenerated disc specimens were obtained from spondylolisthesis patients and ten nondegenerated discs from idiopathic scoliosis patients during surgical procedures. Immunohistochemical staining was performed to determine the presence of FasL in cross-sections of those discs. Parts of the disc tissues were used to examine FasL expression quantitatively with Western blot analysis. To examine whether the change in FasL expression was influenced by aging, an animal study comparing the discs from young and old rats were performed using magnetic resonance imaging (MRI) and real-time polymerase chain reaction (PCR) assessment. RESULTS: Nucleus pulposus cells showed strong positive staining for FasL in all specimens examined. Quantitative examination demonstrated a significant decrease in FasL expression in the degenerated group compared with the nondegenerated group (average 67.6%, P<0.05). MRI showed no significant differences in the grade of disc degeneration between young and old rats, and also no significant difference in FasL mRNA in real-time PCR assay. CONCLUSIONS: The current results indicate that FasL and its potential mechanism of immunological privilege could influence the protection of the intervertebral disc against degeneration.

Thoracic myelopathy due to ossification of the yellow ligament in young baseball pitchers.

STUDY DESIGN: Case series. OBJECTIVES: To report rare cases of thoracic myelopathy due to ossification of the yellow ligament (OYL) in relatively young baseball pitchers and show clinical evidence of the role of dynamic mechanical stress on the development of OYL. SUMMARY OF BACKGROUND DATA: The pathogenesis of OYL is still unclear. The majority of cases of OYL occur in middle-aged men whereas younger people are rarely affected. This has lead to the hypothesis that diffuse mechanical stress and degenerative changes correlate with the development of OYL. However, there have been no clinical reports demonstrating the critical role of mechanical stress in the ossification. METHODS: Two young highly active baseball pitchers with thoracic myelopathy due to OYL are presented. Both had no previous systemic disorders or family history of treatment for OYL. Magnetic resonance imaging and computed tomography demonstrated compression of the spinal cord by unilateral left sided OYL at the level of the thoracolumbar junction. RESULTS: Both patients were treated with posterior decompression. They recovered full muscle power after operation and resumed pitching training. CONCLUSIONS: Patients had no other factors influencing the development of OYL and the lesions were localized at the left side in the thoracolumbar junction, indicating that repeated, localized rotatory mechanical stress caused by the pitching motion probably influenced the development of OYL in these young baseball pitchers.

A surgical approach for an avulsion fracture of the ischial tuberosity: a case report.

We report a case of an avulsion fracture of the ischial tuberosity treated with a new surgical approach early after injury. Although surgical treatment of this fracture is usually avoided because of the difficulty of the procedure and the risk of sciatic nerve complication, we believe our subgluteal approach is simple and safe. We therefore recommend it for treating avulsion fractures of the ischial tuberosity, especially when the fragment is displaced by >2 cm and the sciatic nerve is not involved. If there is clinical evidence of sciatic nerve disturbance, it is likewise an indication for surgery. However, the incision needs to be deepened to approach the nerve, along the lines of the incisions advocated by both Miller and Spinner.