Carbon nanotube-based biomaterials for orthopaedic applications.

Carbon nanotubes (CNTs) are cylindrical tubular nanomaterials made of carbon with excellent electrical conductivity, thermal conductivity, and mechanical strength. The material is applied to improve performance in various industrial products. CNTs have been widely researched and developed as biomaterials that can offer high function, performance, and durability in orthopedic applications. However, the use of CNTs as biomaterials must be administered with caution, as the fibrous nanomaterial may be carcinogenic due to its similar size and shape to asbestos. In this review article, we examine the potential clinical application of CNTs in orthopedic surgery. We first provide an overview of biocompatibility and carcinogenicity studies of CNTs with a focus on their effects on the bone, joint, and respiratory system. Furthermore, we introduce CNT-based biomaterials for orthopedic applications that have been reported in the literature, including scaffolds for bone and cartilage regeneration, composites that enhance the performance of biomaterials, CNT coatings, and devices for treating musculoskeletal tumors.

Optimal cervical screw insertion angle determined by means of computed tomography scans pre- and postoperatively.

BACKGROUND CONTEXT: Cervical pedicle screw (CPS) insertion is technically demanding and carries a risk of serious neurovascular complications when screws perforate. To avoid such serious risks, we currently perform CPS insertion using a computed tomography (CT)-guided navigation system. However, there remains a low probability of screw perforation during CPS insertion that is affected by factors such as CPS insertion angle and anatomical pedicle transverse angle (PTA). PURPOSE: This study aimed to understand the perforation tendencies of CPS insertion angles in relation to anatomical PTA. STUDY DESIGN: This is a retrospective chart review. PATIENT SAMPLE: The study enrolled 151 consecutive patients (95 men and 56 women, with a mean age of 64.6 years). OUTCOME MEASURES: Anatomical PTA and CPS insertion angles were evaluated by axial CT images. METHODS: The medical records of 151 consecutive patients who underwent CPS insertion using a CT-based navigation system were reviewed. We examined the relationships between PTA and CPS insertion angle on axial CT images according to vertebral level. RESULTS: The average preoperative PTA at each vertebral level was 32.1° for C2, 41.5° for C3, 41.0° for C4, 39.4° for C5, 34.4° for C6, and 27.3° for C7. Corresponding CT-determined pedicle screw insertion angles were 24.9°, 31.3°, 28.7°, 27.8°, 28.0°, and 26.0°, respectively. The CPS insertion angles at C2-C6 were significantly smaller than those for PTA (p<.01). In evaluations of angle thresholds from C3 to C5 that predicted a higher risk of perforation, the receiver operating characteristic curve analysis determined CPS insertion angles of <24.5° and >36.5° for the identification of lateral and medial perforations, respectively. CONCLUSION: For CPS insertion into the C3-C5 pedicles using CT, there is an increased likelihood of lateral or medial perforation for insertion angles of <24.5° or >36.5°, respectively.

Challenges of Transarticular Screw Fixation in Young Children: Report of Surgical Treatment of a 5-Year-Old Patient's Unstable Os-Odontoideum.

Surgical procedures for atlantoaxial (C1-C2) fusion in young children are relatively uncommon. The purpose of this study was to report on a surgical treatment for a case of atlantoaxial instability caused by os-odontoideum in association with quadriparesis and respiratory paralysis in a 5-year-old girl. We present the patient's history, physical examination, and radiographic findings, describe the surgical treatment and a five year follow-up, and provide a literature review. The instability was treated by halo immobilization, followed by C1-C2 transarticular screw fixation using a computed tomography-based navigation system. At the five year follow-up, the patient had made a complete recovery with solid union. The authors conclude that C1-2 transarticular screw fixation is technically possible as in a case of atlantoaxial instability in a five-year-old child.

Comparison of Clinical and Radiological Results of Posterolateral Fusion and Posterior Lumbar Interbody Fusion in the Treatment of L4 Degenerative Lumbar Spondylolisthesis.

STUDY DESIGN: Multicenter analysis of two groups of patients surgically treated for degenerative L4 unstable spondylolisthesis. PURPOSE: To compare the clinical and radiographic outcomes of posterolateral fusion (PLF) and posterior lumbar interbody fusion (PLIF) for degenerative L4 unstable spondylolisthesis. OVERVIEW OF LITERATURE: Surgery for lumbar degenerative spondylolisthesis is widely performed. However, few reports have compared the outcome of PLF to that of PLIF for degenerative L4 unstable spondylolisthesis. METHODS: Patients with L4 unstable spondylolisthesis with Meyerding grade II or more, slip of >10° or >4 mm upon maximum flexion and extension bending, and posterior opening of >5 degree upon flexion bending were studied. Patients were treated from January 2008 to January 2010. Patients who underwent PLF (n=12) and PLIF (n=19) were followed-up for >2 years. Radiographic findings and clinical outcomes evaluated by the Japanese Orthopaedic Association (JOA) score were compared between the two groups. Radiographic evaluation included slip angle, translation, slip angle and translation during maximum flexion and extension bending, intervertebral disc height, lumbar lordotic angle, and fusion rate. RESULTS: JOA scores of the PLF group before surgery and at final follow-up were 12.3±4.8 and 24.1±3.7, respectively; those of the PLIF group were 14.7±4.8 and 24.2±7.8, respectively, with no significant difference between the two groups. Correction of slip estimated from postoperative slip angle, translation, and maintenance of intervertebral disc height in the PLIF group was significantly (p<0.05) better than those in the PLF group. However, there was no significant difference in lumbar lordotic angle, slip angle and translation angle upon maximum flexion, or extension bending. Fusion rates of the PLIF and PLF groups had no significant difference. CONCLUSIONS: The L4-L5 level posterior instrumented fusion for unstable spondylolisthesis using both PLF and PLIF could ameliorate clinical symptoms when local stability is achieved.

Mini Open Foraminotomy for Cervical Radiculopathy: A Comparison of Large Tubular and TrimLine Retractors.

STUDY DESIGN: Retrospective chart review. PURPOSE: A comparison of mini open foraminotomy (MOF) for cervical radiculopathy using either large tubular (LT) or TrimLine (TL) retractors. OVERVIEW OF LITERATURE: Posterior foraminotomy relieves compression of the cervical nerve root in radiculopathy patients. However, invasion of the paravertebral muscle may cause major problems in these patients. To address these problems, we performed MOF. METHODS: Twenty cervical radiculopathy patients (16 male and 4 female) who underwent MOF between May 2004 and August 2011 were assigned to LT and TL groups. Each group contained 10 subjects. Surgical and clinical outcomes were compared. RESULTS: The average operating time in the TL group was significantly shorter than that in the LT group. The final follow-up mean neck disability indices significantly improved compared to the preoperative values (LT group, 12.0±7.8 vs. 28.0±9.4; TL group, 6.0±5.9 vs. 21.9±10). The final follow-up neck pain visual analog scale (VAS) scores also decreased significantly from the preoperative of 8.0±1.5 and 2.5±2.5 to the final follow-up values of 2.2±2.2 and 1.0±2.5 in the LT and TL groups, respectively. The recovery rate for the neck pain VAS score was 70.0±31.9 in the LT group and 87.0±32.0 in the TL group, thus suggesting no significant difference between the two groups. CONCLUSIONS: MOF with the TL retractor is an easy and safe procedure. Furthermore, the use of the TL retractor allows for a minimally invasive and effective surgical treatment of cervical radiculopathy patients.

Screw perforation features in 129 consecutive patients performed computer-guided cervical pedicle screw insertion.

STUDY DESIGN: A cross-sectional study of the data retrospectively collected by chart review. OBJECTIVES: This study aimed to clarify screw perforation features in 129 consecutive patients treated with computer-assisted cervical pedicle screw (CPS) insertion and to determine important considerations for computer-assisted CPS insertion. CPS fixation has been criticized for the potential risk of serious injury to neurovascular structures. To avoid such serious risks, computed tomography (CT)-based navigation has been used during CPS insertion, but screw perforation can occur even with the use of a navigation system. METHODS: The records of 129 consecutive patients who underwent cervical (C2-C7) pedicle screw insertion using a CT-based navigation system from September 1997 to August 2013 were reviewed. Postoperative CT images were used to evaluate the accuracy of screw placement. The screw insertion status was classified as grade 1 (no perforation), indicating that the screw was accurately inserted in pedicle; grade 2 (minor perforation), indicating perforation of less than 50 % of the screw diameter; and grade 3 (major perforation), indicating perforation of 50 % or more of the screw diameter. We analyzed the direction and rate of screw perforation according to the vertebral level. RESULTS: The rate of grade 3 pedicle screw perforations was 6.7 % (39/579), whereas the combined rate of grades 2 and 3 perforations was 20.0 % (116/579). No clinically significant complications, such as vertebral artery injury, spinal cord injury, or nerve root injury, were caused by the screw perforations. Of the screws showing grade 3 perforation, 30.8 % screws were medially perforated and 69.2 % screws were laterally perforated. Of the screws showing grades 2 and 3 perforation, 21.6 % screws were medially perforated and 78.4 % screws were laterally perforated. Furthermore, we evaluated screw perforation rates according to the vertebral level. Grade 3 pedicle screw perforation occurred in 6.1 % of C2 screws; 7.5 % of C3 screws; 13.0 % of C4 screws; 6.5 % of C5 screws; 3.2 % of C6 screws; and 4.0 % of C7 screws. Grades 2 and 3 pedicle screw perforations occurred in 12.1 % of C2 screws, 22.6 % of C3 screws, 31.5 % of C4 screws, 22.2 % of C5 screws, 14.4 % of C6 screws, and 12.1 % of C7 screws. C3-5 screw perforation rate was significantly higher than C6-7 (p = 0.0024). CONCLUSIONS: Careful insertion of pedicle screws is necessary, especially at C3 to C5, even when using a CT-based navigation system. Pedicle screws tend to be laterally perforated.

Mid-term results of computer-assisted cervical pedicle screw fixation.

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.

Comparison of Spinous Process-Splitting Laminectomy versus Conventional Laminectomy for Lumbar Spinal Stenosis.

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.

Mid-term results of computer-assisted cervical reconstruction for rheumatoid cervical spines.

STUDY DESIGN: A retrospective single-center study. We routinely have used C1-C2 transarticular and cervical pedicle screw fixations to reconstruct highly destructed unstable rheumatoid arthritis (RA) cervical lesions. However, there is little data on mid-term results of surgical reconstruction for rheumatoid cervical disorders, particularly, cervical pedicle screw fixation. OBJECTIVES: The purpose of this study was to evaluate the mid-term surgical results of computer-assisted cervical reconstruction for such lesions. METHODS: Seventeen subjects (4 men, 13 women; mean age, 61 ± 9 years) with RA cervical lesions who underwent C1-C2 transarticular screw fixation or occipitocervical fixation, with at least 5 years follow-up were studied. A frameless, stereotactic, optoelectronic, CT-based image-guidance system, was used for correct screw placement. Variables including the Japanese Orthopaedic Association (JOA) score, Ranawat class, EuroQol (EQ-5D), atlantodental interval, and Ranawat values before, and at 2 and 5 years after surgery, were evaluated. Furthermore, screw perforation rates were evaluated. RESULTS: The lesions included atlantoaxial subluxation (AAS, n = 6), AAS + vertical subluxation (VS, n = 7), and AAS + VS + subaxial subluxation (n = 4). There was significant neurological improvement at 2 years after surgery, as evidenced by the JOA scores, Ranawat class, and the EQ-5D utility weight. However, at 5 years after surgery, there was a deterioration of this improvement. The Ranawat values before, and at 2 and 5 years after surgery, were not significantly different. Major screw perforation rate was 2.1 %. No neural and vascular complications associated with screw insertion were observed. CONCLUSIONS: Subjects with rheumatoid cervical lesions who underwent C1-C2 transarticular screw fixation or occipitocervical fixation using a pedicle screw had significantly improved clinical parameters at 2 years after surgery. However, there was a deterioration of this improvement at 5 years post surgery.

Factors influencing the residual rib hump after posterior spinal fusion for adolescent idiopathic scoliosis with Lenke 1 and 2 curves.

BACKGROUND: Despite remarkable improvement in Cobb angle after surgery for scoliosis, many patients have a residual rib hump. We studied the factors responsible for this hump and their influence on patient satisfaction. METHODS: We recruited 2 men and 38 women (mean age 14.9 years) who underwent skip pedicle screw fixation combined with direct vertebral body derotation for adolescent idiopathic scoliosis with Lenke type 1 and 2 curves. Hump size was evaluated by measuring apical trunk rotation (ATR). Patients with postoperative ATR ≤10° were categorized as group A and those with postoperative ATR >10° as group B. We analyzed postoperative self-image and satisfaction subscores of the SRS-22 questionnaire. We also compared the rate of postoperative improvement in ATR between patients who underwent additional Ponte osteotomy and those who did not. RESULTS: Preoperative ATR, preoperative apical translation, and preoperative and postoperative apical rotation significantly differed between groups A and B. In contrast, Cobb angles before and after surgery, Cobb angle correction rates, apical translation after correction, and postoperative self-image and satisfaction scores did not differ significantly between the groups. However, the rate of improvement in ATR showed a strong correlation with self-image (correlation coefficient 0.64) and satisfaction (correlation coefficient 0.52). This improvement rate did not differ significantly between subjects who underwent additional Ponte osteotomy and those who did not. CONCLUSIONS: Preoperative apical rotation and ATR were clearly related to postoperative residual hump. For decreasing the postoperative rib hump, removal of the deformation by apical rotation was considered more important than correction of Cobb angle. Patient satisfaction and self-image scores were not significantly related to postoperative residual hump size, but they were influenced by improvement in ATR.

Surgical treatment of Klippel-Feil syndrome with basilar invagination.

INTRODUCTION: Klippel-Feil syndrome (KFS) is a congenital cervical vertebral union caused by a failure of segmentation during abnormal development and frequently accompanies conditions such as basicranial malformation, atlas assimilation, or dens malformation. Especially in basilar invagination (BI), which is a dislocation of the dens in an upper direction, compression of the spinomedullary junction from the ventral side results in paralysis, and treatment is required. CLINICAL PRESENTATION: We present the case of a 38-year-old male patient with KFS and severe BI. Plane radiographs and computed tomography (CT) images showed severe BI, and magnetic resonance image (MRI) revealed spinal cord compression caused by invagination of the dens into the foramen magnum and atlantoaxial subluxation. Reduction by halo vest and skeletal traction were not successful. Occipitocervical fusion along with decompression of the foramen magnum, C1 laminectomy, and reduction using instruments were performed. Paralysis was temporarily aggravated and then gradually improved. Unsupported walking was achieved 24 months after surgery, and activities of daily life could be independently performed at the same time. CT and MRI revealed that dramatic reduction of vertical subluxation and spinal cord decompression were achieved. CONCLUSION: Reduction and internal fixation using instrumentation are effective techniques for KFS with BI; however, caution should be exercised because of the possibility of paralysis caused by intraoperative reduction.

The effect of a prostaglandin E1 derivative on the symptoms and quality of life of patients with lumbar spinal stenosis.

BACKGROUND: Quality of life (QOL) is a concern for patients with lumbar spinal stenosis (LSS). In this study, QOL was examined using the 5-item EuroQol (EQ-5D). METHODS: QOL and activities of daily living (ADL) were surveyed for 91 patients who visited 18 medical institutions in our prefecture and were diagnosed with LSS-associated intermittent claudication. A second survey was performed after ≥6 weeks for 79 of the subjects to evaluate therapy with limaprost (an oral prostaglandin E1 derivative) or etodolac (an NSAID). Symptoms, maximum walking time, QOL, ADL items, and relationships among these variables were investigated for all 91 patients. Leg pain, leg numbness, and low back pain while walking were surveyed by use of VAS scores (0-100). RESULTS: Leg pain, leg numbness, and low back pain while walking (VAS ≥25) were present in 83.5, 62.6, and 54.9 % of the patients in the first survey, and approximately half of the patients had a maximum walking time <15 min. The mean EQ-5D utility value for QOL was 0.59 ± 0.12. This value was significantly associated with maximum walking time (p = 0.030) based on classification of patients into groups with walking times <7.5, 7.5-15, 15-30, and >30 min, showing that maximum walking time affected health-related QOL. Of the 79 patients who completed the second survey, 56 had taken limaprost and 23 (control group) had received etodolac. Limaprost improved possible walking time, reduced ADL interference, and significantly increased the EQ-5D utility score, whereas no significant changes occurred in the control group. Maximum walking time was prolonged by ≥10 min and the EQ-5D utility value was improved by ≥0.1 points in significantly more patients in the limaprost group than in the control group. CONCLUSION: According to the findings of this survey, at an average of 8 weeks after administration limaprost improved symptoms, QOL, and ADL in LSS patients whereas treatment with an NSAID reduced pain but did not have any other effects.

Evaluation of clinical results and quality of life after surgical reconstruction for rheumatoid cervical spine.

BACKGROUND CONTEXT: The EuroQol (EQ-5D) is a widely used comprehensive measure of health-related quality of life. There has been no study that has evaluated the health-related quality of life before and after the surgical reconstruction of rheumatoid arthritis (RA) cervical spine lesions using EQ-5D. PURPOSE: The present study aimed to evaluate the improvement of quality of life before and after surgical reconstruction of rheumatoid cervical spine using EQ-5D, and the surgical outcomes of cervical spine affected by RA. STUDY DESIGN: A retrospective study of the patients who underwent surgical reconstruction of cervical disorders in RA. PATIENT SAMPLE: Twenty-five patients (seven men, 18 women, mean age 62.2 years) who underwent surgical reconstruction of cervical disorders in RA were enrolled. OUTCOME MEASURES: Japanese Orthopaedic Association (JOA) score and EQ-5D. METHODS: Clinical symptoms were evaluated before surgery and at 2 years after surgery by measuring the JOA score. We also investigated health-related quality of life before surgery and outcome at 2 years after surgery using the EQ-5D questionnaire. RESULTS: Mean observation period was 46.3 months. Mean JOA score significantly improved from 9.1 ± 4.5 points before surgery to 12.4 ± 2.8 at the 2 years after surgery (p=.0001). All the EQ-5D data were improved at the 2 years after surgery, compared with the data before surgery; especially, pain (p=.005), usual activity (p=.005), mobility (p=.008), and anxiety/depression (p=.02) were significantly improved. Utility weight was 0.37 ± 0.27 before surgery and 0.56 ± 0.26 at the 2 years after surgery, showing significant improvement at the 2 years after surgery compared to before surgery (p=.002). CONCLUSIONS: The surgical reconstruction of rheumatoid cervical spine has been demonstrated to improve patients' health-related quality of life.

Pedicle morphology using computed tomography-based navigation system in adolescent idiopathic scoliosis.

STUDY DESIGN/SETTING: Retrospective study. OBJECTIVE: The purpose of this study was to use multidimensional analysis with a computed tomography (CT)-based navigation system to measure the outer cortical diameter and the maximum screw trajectory length of the pedicle of the thoracic and lumbar regions of the spine in adolescent idiopathic scoliosis (AIS) patients. Another objective was to identify pedicles that require cautious insertion of screws. SUMMARY OF BACKGROUND DATA: Pedicle diameter in AIS patients was narrower on the concave side of the scoliotic curve. Many researchers have measured pedicle diameter and length of AIS patients by using standard CT or magnetic resonance imaging (MRI), but only few have used 3-dimensional imaging, especially CT-based navigation. METHODS: Fifteen patients with right-side thoracic AIS who underwent pedicle screw fixation were studied. A CT-based navigation system was used to measure the pedicle diameter, defined as the widest outer cortical diameter at the narrowest part of the pedicle. Moreover, the maximum pedicle screw trajectory length was measured as the distance between the posterior cortical entry point of the pedicle screw and the anterior vertebral cortex in line with the axis of the pedicle between T1 and L5. In addition, the values of each parameter taken using the CT navigation system and the standard axial CT were compared. RESULTS: Pedicles on the concave side of the main thoracic curve apex and proximal thoracic curve tended to have the narrowest diameters. The mean length of the longest screw that could be fixed was longer on the right side, except for T8 and T9. Our data showed screw size feasibility as follows: 25 or 30 mm screws were feasible from T1 to T5; 30 or 35 mm screws, from T6 to T12; and 35 or 40 mm screws, from L1 to L5. Pedicle diameter measured by the CT navigation system was larger than that measured by standard axial CT. Left-side pedicle length measured by the CT navigation system was lesser than that measured by standard axial CT. CONCLUSIONS: Pedicle diameter in patients with AIS is narrower on the concave side of the scoliotic curve, and therefore, caution should be exercised during screw insertion on the concave side.

Computer-assisted C1-C2 Transarticular Screw Fixation "Magerl Technique" for Atlantoaxial Instability.

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.

Carcinogenicity evaluation for the application of carbon nanotubes as biomaterials in rasH2 mice.

The application of carbon nanotubes (CNTs) as biomaterials is of wide interest, and studies examining their application in medicine have had considerable significance. Biological safety is the most important factor when considering the clinical application of CNTs as biomaterials, and various toxicity evaluations are required. Among these evaluations, carcinogenicity should be examined with the highest priority; however, no report using transgenic mice to evaluate the carcinogenicity of CNTs has been published to date. Here, we performed a carcinogenicity test by implanting multi-walled CNTs (MWCNTs) into the subcutaneous tissue of rasH2 mice, using the carbon black present in black tattoo ink as a reference material for safety. The rasH2 mice did not develop neoplasms after being injected with MWCNTs; instead, MWCNTs showed lower carcinogenicity than carbon black. Such evaluations should facilitate the clinical application and development of CNTs for use in important medical fields.

Biocompatibility and bone tissue compatibility of alumina ceramics reinforced with carbon nanotubes.

AIMS: The addition of carbon nanotubes (CNTs) remarkably improves the mechanical characteristics of base materials. CNT/alumina ceramic composites are expected to be highly functional biomaterials useful in a variety of medical fields. Biocompatibility and bone tissue compatibility were studied for the application of CNT/alumina composites as biomaterials. METHODS & RESULTS: Inflammation reactions in response to the composite were as mild as those of alumina ceramic alone in a subcutaneous implantation study. In bone implantation testing, the composite showed good bone tissue compatibility and connected directly to new bone. An in vitro cell attachment test was performed for osteoblasts, chondrocytes, fibroblasts and smooth muscle cells, and CNT/alumina composite showed cell attachment similar to that of alumina ceramic. DISCUSSION & CONCLUSION: Owing to proven good biocompatibility and bone tissue compatibility, the application of CNT/alumina composites as biomaterials that contact bone, such as prostheses in arthroplasty and devices for bone repair, are expected.

Carbon nanotubes induce bone calcification by bidirectional interaction with osteoblasts.

Multi-walled carbon nanotubes (MWCNTs) promote calcification during hydroxyapatite (HA) formation by osteoblasts. Primary cultured osteoblasts are incubated with MWCNTs or carbon black. After culture for 3 weeks, the degree of calcification is very high in the 50 µg mL(-1) MWCNT group. Transmission electron microscopy shows needle-like crystals around the MWCNTs, and diffraction patterns reveal that the peak of the crystals almost coincides with the known peak of HA.

Stable reconstruction using halo vest for unstable upper cervical spine and occipitocervical instability.

INTRODUCTION: Upper cervical or occipitocervical disorders such as rheumatoid arthritis present as atlantoaxial subluxation, vertical subluxation of the axis, and subaxial subluxation, which produce myelopathy and severe pain. In such cases, occipitocervical reconstruction surgery may be indicated, and several reports have described reduction of subluxation by fixing the halo vest before this surgery. PURPOSE: The purpose of this study was to evaluate the efficacy of using the halo vest before the surgery for unstable upper cervical spine and for occipitocervical instability. METHODS: Twenty-eight patients (9 men and 19 women; mean age, 61.8 years at surgery) who presented with atlantoaxial or occipitocervical fusion were studied. In all cases, the halo vest was fixed in the conscious condition, and subluxation was reduced before the surgery. The mean follow-up period was 45 months. Roentgenologic measurement and clinical evaluation were performed before the surgery and at the final follow-up. RESULTS: Using the halo vest resulted in significant reductions in the atlantodental interval, the space available for the spinal cord, and the Ranawat value (p < 0.05), and these were maintained until the final follow-up. The mean Japanese Orthopedic Association score significantly improved from 9.5 before surgery to 12.2 at the final follow-up (p = 0.01). Nineteen cases (68%) improved by more than 1 grade by Ranawat's classification after surgery and 16 cases (57%) maintained the same at the follow-up visit. CONCLUSION: Conscious preoperative reduction using the halo vest for occipitocervical disorders is a useful and safe technique.