Haruki Funao

Establishment of a real-time, quantitative, and reproducible mouse model of Staphylococcus osteomyelitis using bioluminescence imaging.

ABSTRACT Osteomyelitis remains a serious problem in the orthopedic field. There are only a few animal models in which the quantity and distribution of bacteria can be reproducibly traced. Here, we established a real-time quantitative mouse model of osteomyelitis using bioluminescence imaging (BLI) without sacrificing the animals. A bioluminescent strain of Staphylococcus aureus was inoculated into the femurs of mice. The bacterial photon intensity (PI) was then sequentially measured by BLI. Serological and histological analyses of the mice were performed. The mean PI peaked at 3 days, and stable signals were maintained for over 3 months after inoculation. The serum levels of interleukin-6, interleukin-1β, and C-reactive protein were significantly higher in the infected mice than in the control mice on day 7. The serum monocyte chemotactic protein 1 level was also significantly higher in the infected group at 12 h than in the control group. A significantly higher proportion of granulocytes was detected in the peripheral blood of the infected group after day 7. Additionally, both acute and chronic histological manifestations were observed in the infected group. This model is useful for elucidating the pathophysiology of both acute and chronic osteomyelitis and to assess the effects of novel antibiotics or antibacterial implants.

Surgical treatment of spinal extradural arachnoid cysts in the thoracolumbar spine.

BACKGROUND Because an idiopathic spinal extradural arachnoid cyst (SEAC) is rare, its optimal surgical treatment remains controversial. OBJECTIVE To evaluate the results of surgical treatments for SEACs and to clarify features of the disease associated with poor outcomes. METHODS Twelve patients with SEACs who underwent surgery at our hospital between 1988 and 2008 were examined retrospectively. The mean follow-up period was 4.7 years. Total resection of the cyst was performed in 7 patients and closure of the dural defect without cyst resection in 5 patients. Surgical outcomes were evaluated with regard to the duration of symptoms, the size of the cyst, and the surgical procedure used. RESULTS Neurological recovery was observed in all patients, and there was no recurrence. Poor outcomes were observed in patients with a long duration of symptoms (>1 year, P < .01) and large cyst size (>5 vertebrae, P < .05). The surgical procedure had no significant association with the postoperative neurological recovery. However, there was a significant difference in the degree of the mean postoperative kyphotic angle between the patients treated by total resection of the cyst (9.7 degrees) and those treated by closure of the dural defect without cyst resection through selective laminectomy (2.2 degrees) (P < .01). CONCLUSION There was no significant difference in postoperative neurological recovery between the 2 surgical procedures. However, closure of the dural defect without cyst resection was less invasive, preventing postoperative kyphotic deformity of the thoracolumbar spine.

A novel hydroxyapatite film coated with ionic silver via inositol hexaphosphate chelation prevents implant-associated infection

Various silver-coated implants have been developed to prevent implant-associated infections, and have shown dramatic effects in vitro. However, the in vivo results have been inconsistent. Recent in vitro studies showed that silver exerts antibacterial activity by mediating the generation of reactive oxygen species in the presence of oxygen. To maintain its antibacterial activity in vivo, the silver should remain in an ionic state and be stably bound to the implant surface. Here, we developed a novel bacteria-resistant hydroxyapatite film in which ionic silver is immobilized via inositol hexaphosphate chelation using a low-heat immersion process. This bacteria-resistant coating demonstrated significant antibacterial activity both in vitro and in vivo. In a murine bioluminescent osteomyelitis model, no bacteria were detectable 21 days after inoculation with S. aureus and placement of this implant. Serum interleukin-6 was elevated in the acute phase in this model, but it was significantly lower in the ionic-silver group than the control group on day 2. Serum C-reactive protein remained significantly higher in the control group than the ionic-silver group on day 14. Because this coating is produced by a low-heat immersion process, it can be applied to complex structures of various materials, to provide significant protection against implant-associated infections.

Delayed Propionibacterium acnes surgical site infections occur only in the presence of an implant

Whether Propionibacterium acnes (P. acnes) causes surgical-site infections (SSI) after orthopedic surgery is controversial. We previously reported that we frequently find P. acnes in intraoperative specimens, yet none of the patients have clinically apparent infections. Here, we tracked P. acnes for 6 months in a mouse osteomyelitis model. We inoculated P. acnes with an implant into the mouse femur in the implant group; the control group was treated with the bacteria but no implant. We then observed over a 6-month period using optical imaging system. During the first 2 weeks, bacterial signals were detected in the femur in the both groups. The bacterial signal completely disappeared in the control group within 28 days. Interestingly, in the implant group, bacterial signals were still present 6 months after inoculation. Histological and scanning electron-microscope analyses confirmed that P. acnes was absent from the control group 6 months after inoculation, but in the implant group, the bacteria had survived in a biofilm around the implant. PCR analysis also identified P. acnes in the purulent effusion from the infected femurs in the implant group. To our knowledge, this is the first report showing that P. acnes causes SSI only in the presence of an implant.

A Retrospective Cohort Study Comparing the Safety and Efficacy of Minimally Invasive Versus Open Surgical Techniques in the Treatment of Spinal Metastases

Study Design: A retrospective cohort study. Objective: This study was conducted to assess the invasiveness, efficacy, and safety of minimally invasive spine stabilization (MISt) for metastatic spinal tumor patients with short life expectancy. Summary of Background Data: Conventional open surgery for metastatic spinal tumors has the disadvantages of significant blood loss, potential infection, damage to back muscles, and extended hospital stays. The minimally invasive spine surgery has changed the treatment of metastatic spinal tumors radically and fundamentally. Materials and Methods: We retrospectively reviewed data from 50 consecutive patients registered with the Keio Spine Research Group (KSRG) who underwent posterior palliative surgery for metastatic spinal tumors from January 2009 to June 2015. Of these, 25 patients underwent MISt surgery (M group), and 25 underwent conventional open surgery (C group). The patients were assessed by demographic data, surgical invasiveness, complications, pain improvement, and neurological recovery. Results: The 2 groups did not differ significantly in baseline characteristics. The M group had significantly less blood loss (M, 340.1 mL; C, 714.3 mL; P=0.005), less postoperative drainage (M, 136.0 mL; C, 627.0 mL; P<0.001), lower rates of red blood cell transfusion (M, 3 cases; C, 10 cases; P=0.029), and a shorter postoperative period of bed rest (M, 2.0 d; C, 3.6 d; P<0.001), compared with the C group. The perioperative complication rates were significantly lower (P=0.012) in the M group (3 patients, 12%) than in the C group (11 patients, 44%). Neurological deficits and pain improved significantly and comparably in the 2 groups after surgery. Conclusions: MISt is a less invasive and effective alternative surgery to conventional open surgery for metastatic spinal tumors. MISt should be considered as a valid option for the treatment of metastatic spinal tumor patients with a short life expectancy. Level of Evidence: Level 3.

A novel mouse model of soft-tissue infection using bioluminescence imaging allows noninvasive, real-time monitoring of bacterial growth.

Musculoskeletal infections, including surgical-site and implant-associated infections, often cause progressive inflammation and destroy areas of the soft tissue. Treating infections, especially those caused by multi-antibiotic resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) remains a challenge. Although there are a few animal models that enable the quantitative evaluation of infection in soft tissues, these models are not always reproducible or sustainable. Here, we successfully established a real-time, in vivo, quantitative mouse model of soft-tissue infection in the superficial gluteus muscle (SGM) using bioluminescence imaging. A bioluminescent strain of MRSA was inoculated into the SGM of BALB/c adult male mice, followed by sequential measurement of bacterial photon intensity and serological and histological analyses of the mice. The mean photon intensity in the mice peaked immediately after inoculation and remained stable until day 28. The serum levels of interleukin-6, interleukin-1 and C-reactive protein at 12 hours after inoculation were significantly higher than those prior to inoculation, and the C-reactive protein remained significantly elevated until day 21. Histological analyses showed marked neutrophil infiltration and abscesses containing necrotic and fibrous tissues in the SGM. With this SGM mouse model, we successfully visualized and quantified stable bacterial growth over an extended period of time with bioluminescence imaging, which allowed us to monitor the process of infection without euthanizing the experimental animals. This model is applicable to in vivo evaluations of the long-term efficacy of novel antibiotics or antibacterial implants.

Reliability Analysis of Spino-Pelvic Parameters in Adult Spinal Deformity: A Comparison of Whole Spine and Pelvic Radiographs.

Study Design. Retrospective study. Objective. To examine the reliabilities of sagittal spino-pelvic alignment measurements using whole spine-pelvic and local pelvic radiographs and to determine whether spinal deformity affects these reliabilities. Summary of Background Data. Sagittal spino-pelvic alignment is important in adult spinal deformity patients (ASD). Spino-pelvic parameters are closely related to health-related quality of life and indispensable for surgical planning. However, few studies have focused on the reliability of these measurements. Methods. Three spino-pelvic parameters, pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS) were measured in 2 patient groups: 33 adult scoliosis (AS) and 33 nondeformity (ND) patients, using whole spine-pelvic lateral radiographs (whole spine radiographs) and local pelvic lateral radiographs (local pelvic radiographs), by 5 experienced spine surgeons. Intra- and interobserver reliabilities for each procedure were evaluated by intraclass correlation coefficients (ICC). The interobserver reliability differences between the 2 procedures were statistically evaluated. The difference between the largest and smallest measurements among the 5 observers was also evaluated in the AS and ND groups. Results. Measurement of the 3 parameters using whole spine or local pelvic radiographs showed good to excellent intraobserver reliability (range of ICC: 0.820–0.935). The interobserver reliabilities of PI and PT from local pelvic radiographs were significantly higher than those from whole spine radiographs (P < 0.002). The intraobserver reliabilities of PI and PT from pelvic radiographs tended to be higher than those from whole spine radiographs, but the differences were not statistically significant. The reliability of SS was comparable between the 2 methods. The differences between the highest and lowest PI and PT measurements were smaller with the pelvic compared to whole spine radiographs. These findings were consistent in the AS and ND groups. Conclusion. Local pelvic radiography is more reliable than whole spine radiography for determining spino-pelvic parameters, and we recommend its use for evaluating ASD patients. Level of Evidence: 3

Risk Factors for Proximal Junctional Fracture following Fusion Surgery for Osteoporotic Vertebral Collapse with Delayed Neurological Deficits: A Retrospective Cohort Study of 403 Patients

Introduction Approximately 3% of osteoporotic vertebral fractures develop osteoporotic vertebral collapse (OVC) with neurological deficits, and such patients are recommended to be treated surgically. However, a proximal junctional fracture (PJFr) following surgery for OVC can be a serious concern. Therefore, the aim of this study is to identify the incidence and risk factors of PJFr following fusion surgery for OVC. Methods This study retrospectively analyzed registry data collected from facilities belonging to the Japan Association of Spine Surgeons with Ambition (JASA) in 2016. We retrospectively analyzed 403 patients who suffered neurological deficits due to OVC below T10 and underwent corrective surgery; only those followed up for　≥2 years were included. Potential risk factors related to the PJFr and their cut-off values were calculated using multivariate logistic regression analysis and receiver operating characteristic (ROC) analysis. Results Sixty-three patients (15.6%) suffered PJFr during the follow-up (mean 45.7 months). In multivariate analysis, the grade of osteoporosis (grade 2, 3: adjusted odds ratio (aOR) 2.92; p=0.001) and lower instrumented vertebra (LIV) level (sacrum: aOR 6.75; p=0.003) were independent factors. ROC analysis demonstrated that lumbar bone mineral density (BMD) was a predictive factor (area under curve: 0.72, p=0.035) with optimal cut-off value of 0.61 g/cm2 (sensitivity, 76.5%; specificity, 58.3%), but that of the hip was not (p=0.228). Conclusions PJFr was found in 16% cases within 4 years after surgery; independent risk factors were severe osteoporosis and extended fusion to the sacrum. The lumbar BMD with cut-off value 0.61 g/cm2 may potentially predict PJFr. Our findings can help surgeons select perioperative adjuvant therapy, as well as a surgical strategy to prevent PJFr following surgery.

Utilization of a Technique of Percutaneous S2 Alar-Iliac Fixation in Immunocompromised Patients with Spondylodiscitis.

BACKGROUND Spondylodiscitis still remains a serious problem, especially in immunocompromised patients. Surgery is necessary when nonsurgical treatment is unsuccessful. Although minimally invasive spine stabilization (MISt) with percutaneous pedicle screws is less invasive, percutaneous sacropelvic fixation techniques are not common practice. Here, we describe 2 cases in which spondylodiscitis in the lumbosacral spine was treated with percutaneous stabilization using an S2 alar-iliac (S2AI) screw technique. CASE DESCRIPTION Case 1 is a 77-year-old man who presented with low back pain and high fever. He was diagnosed with spondylodiscitis at L4-5. He had a history of lung cancer, which was complicated by the recurrence. Because nonsurgical treatment failed, MISt with percutaneous S2AI screws was performed. The patients low back pain subsided markedly 1 week after surgery, and there was no screw/rod breakage or recurrence of infection during the follow-up period. Case 2 is a 71-year-old man who presented with hemiparesis because of a stroke. He also developed high fever and was diagnosed with spondylodiscitis at L5-S1. Because nonsurgical treatment failed, the patient was treated by MISt with percutaneous S2AI screws while being maintained on anticoagulants for stroke. Although his clinical symptoms had markedly improved, a postoperative lumbar computed tomography scan demonstrated a bone defect at L5-S1. An anterior spinal fusion with an iliac bone graft at L5-S1 was performed when a temporary cessation of anticoagulants was permitted. Both patients tolerated the procedures well and had no major perioperative complications. CONCLUSIONS MISt with percutaneous S2AI screws was less invasive and efficacious for lumbosacral spondylodiscitis in providing rigid percutaneous sacropelvic fixation.

A Novel Groove-Entry Technique for Inserting Thoracic Percutaneous Pedicle Screws.

Study Design: Surgical technique. Objective: To evaluate the efficacy of a novel groove-entry technique for thoracic percutaneous pedicle screw (PPS) insertion. Summary of Background Data: Minimally invasive spine stabilization (MISt) using posterior thoracolumbar instrumentation has many advantages over open procedures. Because of the variability among PPS entry points, the sloped cortex of the transverse process, and the narrow thoracic pedicle, thoracic PPS placement is technically challenging. Materials and Methods: A retrospective review of 24 patients who underwent minimally invasive spine stabilization procedures involving 165 thoracic PPS placements using the novel technique was performed. The thoracic PPS entry is a groove formed by 3 bony elements: the cranial portion of the base of the transverse process, the rib neck, and the posterolateral wall of the pedicle. This groove can be easily identified under fluoroscopy with a Jamshidi needle allowing thoracic PPS insertion in the craniocaudal direction. Results: Of the 165 thoracic PPSs placed, “Good” or “Acceptable” PPS placement accuracy was achieved in 152 (92.1%) and 164 (99.4%) placements, respectively. No complications such as organ injury, and screw loosening or breakage were observed with thoracic PPS insertion. Conclusions: This novel technique is both safe and reliable, with low misplacement and complication rates. In hospitals in which computer image guidance or navigation is unavailable, this groove-entry technique may become the standard for thoracic PPS insertion.