Chak-Bor Wong

Surgical treatment of adjacent instability after lumbar spine fusion.

Study Design. This study is a retrospective review of 39 patients with previous instrumented lumbar fusion who underwent secondary spine surgery for lumbar adjacent instability. To the authors’ knowledge, this is the largest study of surgical treatment of lumbar adjacent instability in the literature to date. Object. This study evaluated the feasibility of adjacent instability treated with medial facetectomy, fusion with autologous bone grafting, and pedicle screw instrumentation. Summary of Background Data. The surgical treatment of adjacent instability has seldom been discussed. Revision spine fusions are challenged by high pseudarthrosis rates. Methods. Thirty-nine patients with previous lumbar fusion underwent second lumbar spine surgery for adjacent instability. All were treated with autogenous posterolateral arthrodesis and transpedicle screw fixation in addition to decompressive laminectomy. Medical records, radiographs, and pain scores were obtained. Results. The clinical results were excellent or good in 76.9% of patients, and the radiographic fusion was successful in 37 (94.9%) of patients. Flat back was noted in 8 (20.5%) of patients. In 5 patients (12.8%), neighboring segment breakdown again developed, and 2 of those patients underwent a third lumbar fusion. Dural tear during operation occurred in 2 patients. One patient experienced cauda equina syndrome but recovered bladder function 1 month later. Conclusion. Autogenous posterolateral arthrodesis combined with pedicle screw fixation led to successful radiologic and clinical outcome in patients with lumbar adjacent instability. Adequate decompression of the adjacent stenosis requires medial facetectomy, thus preventing aggressive nerve root manipulation and reducing the incidence of dural tear.

Polymethylmethacrylate cement dislodgment following percutaneous vertebroplasty: a case report.

Study Design. A case report is presented. Objectives. To report a rare complication of delayed cement displacement following percutaneous vertebroplasty. Summary of Background Data. Although percutaneous vertebroplasty is considered a minimally invasive procedure, it may result in several complications. To our knowledge, this is the first report of delayed cement displacement after percutaneous vertebroplasty. Methods. A 69-year-old man with T12 osteoporotic compression fracture received percutaneous vertebroplasty. One month after surgery, the patient complained of progressive severe back pain, and roentgenographic image revealed a breakdown of the anterior cortex of the T12 vertebral body with anterior displacement of the bone cement. Results. The complication was solved by one stage anterior and posterior operation: thoracoabdominal approach with removal of the displaced cement and posterior instrumentation from T11 to L1. The severe back pain with associated weakness improved after surgery. Conclusions. This complication is rare and likely to occur in treatment of osteoporotic vertebral fracture with avascular necrosis and anterior cortical defect.

Instrumented posterior lumbar interbody fusion for patients with degenerative lumbar scoliosis.

Objective Surgery for degenerative lumbar scoliosis remains challenging for spine surgeons even with the application of pedicle screw instrumentation. This retrospective study assesses the outcomes of instrumented posterior lumbar interbody fusion (PLIF) for degenerative lumbar scoliosis. Methods From April 2000 to April 2004, 26 patients with degenerative lumbar scoliosis were treated with instrumented PLIF. Mean age of the 15 females and 11 males was 64.2 years (range, 51 to 77 y). Clinical and radiographic outcomes were retrospectively reviewed for each case at a minimum follow-up of 2 years (median follow-up, 3 y; range, 2 to 6 y). At final follow-up, patients were classified as “satisfied” or “dissatisfied” according to self-reported outcomes. Results At most recent follow-up, the average Oswestry Disability Index score was significantly lower than the preoperative score (25.8 vs. 58.0; P<0.001). Twenty (76.9%) patients reported that they were satisfied with their surgical outcomes. The average lumbar scoliosis angles were significantly less than preoperative angles (7.4 vs. 16.5 degrees; P<0.001), resulting in a reduction in mean scoliosis angles of 55.2%. The average angles of lumbar lordosis were significantly higher than preoperative angles (30.1 vs. 22.2 degrees; P=0.001), an increase in mean lumbar lordosis angles of 35.6%. No perioperative deaths or major medical complications occurred. Five patients had adjacent segment degeneration and 4 (80%) of 5 reported dissatisfactory outcomes. Further study is required to identify the etiologies of adjacent segment degeneration and methods for avoiding such degeneration. Conclusions Analytical results demonstrate that instrumented PLIF after laminectomy in patients with degenerative lumbar scoliosis is an effective and safe procedure.

Pedicle screw insertion: computed tomography versus fluoroscopic image guidance

Computed tomography image-guided surgery (CTGS) clearly improves the accuracy of pedicle screw insertion. Recent reports claim that a fluoroscopy-guided system (FGS) offered high accuracy and easy application. However, the superiority of either technique remains unclear in clinical application. This study compares the accuracy of pedicle screws installed using CTGS with that of screws installed using FGS. Seventy-four screws inserted using FGS in 13 patients and 76 screws inserted using CTGS in 11 patients were compared. The study population included ten cases of vertebral fracture, five cases of degenerative spondylolisthesis, three cases of spondylolytic spondylolisthesis, two cases of tuberculous spondylitis, two cases of failed earlier back surgery and two case of ankylosing spondylitis with pseudarthrosis. The installed vertebral levels ranged from T8 to S1. Screw positions were assessed with postoperative radiographs and computed tomography. Sixty-nine (93.2%) screws were correctly placed in the FGS group, and seventy-three (96.1%) screws were correctly placed in the CTGS group (P = 0.491). The results indicated that both image-guided systems offer high accuracy. However, the fluoroscope image-guided system could be considered the primary tool for lower thoracic and lumbosacral pedicle placement because it enables real-time navigation and does not require a preoperative CT scan.RésuméLa chirurgie assistée par imagerie (CTGS) permet d’avoir une meilleure sécurité lors de l’implantation de vis pediculaires. Des articles récents montrent que le système avec amplificateur de brillance (fluoroscopie FGS) permet également cette implantation. Cependant, la supériorité d’une technique ou d’une autre n’apparaît pas clairement. Le but de cette étude est de comparer la bonne implantation des vis pediculaires en utilisant les deux systèmes. 74 vis ont été insérées avec le système FGS chez 13 patients et 66 vis avec le système CTGS chez 11 patients. Ces deux séries ont été comparées. Cette étude inclut 10 cas de fractures vertébrales, 5 cas de spondylolisthésis dégénératifs, 3 cas de spondylolisthésis avec spondylolyse, à 2 cas d’atteintes tuberculeuses, 2 cas d’échec de chirurgie par voie postérieure et 2 cas de spondylarthrite ankylosante avec pseudarthrose. Les niveaux d’instrumentation se sont échelonnés de T8 à S1. 69 (93.2%) vis ont été correctement mises en place dans le groupe FGS et, 73 (96.1%) avec le groupe CTGS (P = 0.491). Les résultats montrent que le système d’images guidées CTGS offre beaucoup plus de sécurité dans l’implantation des vis tant au niveau lombaire qu’au niveau thoracique ou lombosacré ceci ne nécessite pas par ailleurs un scanner pré opératoire.

Computer-assisted fluoroscopic navigation of pedicle screw insertion An in vivo feasibility study

Background Accurate placement of pedicle screws is difficult. Patients and methods We evaluated the feasibility and accuracy of pedicle screw insertion assisted by a real-time, 2-dimensional (2D) image-guided navigation system in 12 patients who underwent thoraco-lumbar and/or lumbar stabilization. 66 pedicle screws were inserted either by senior spine surgeons or residents. The accuracy of positioning of the screws was evaluated using postoperative plain radiographs and thin-cut CT. Results 61 of the 66 screws were inserted successfully. 5 screw insertions showed structural violations: 4 on the medial and 1 on the lateral pedicle wall. The accuracy was higher in the sagittal plane than in the axial plain. There was no difference between the surgical error rates caused by the senior surgeons and the residents. Interpretation Using computer-assisted 2D fluoroscopic image navigation, it is possible to achieve reliable and accurate pedicle screw insertion during low thoracic and lumbar spinal surgery.

Mesenchymal stem cells expressing baculovirus-engineered BMP-2 and VEGF enhance posterolateral spine fusion in a rabbit model.

BACKGROUND CONTEXT Mesenchymal stem cell (MSC)-based cell therapy and gene transfer have converged and show great potential for accelerating bone healing. Gene therapy can provide more sustained expression of osteogenic factors such as bone morphogenetic protein-2 (BMP-2). We previously demonstrated that low-dose BMP-2 enhanced spinal posterolateral fusion by MSCs in a rabbit model. Herein, we genetically modified rabbit MSCs with a recombinant baculovirus encoding BMP-2 (Bac-CB) and vascular endothelial growth factor (Bac-VEGF) seeded into porous scaffolds to enhance spinal fusion. PURPOSE This study evaluates the success rate of the MSC-based cell therapy and gene transfer approach for single-level posterolateral spine fusion. We hypothesize that combining three-dimensional tricalcium phosphate (TCP) scaffolds and genetically modified allogeneic MSCs with baculovirus-mediated growth factor expression would increase the success rate of spinal fusion. STUDY DESIGN The study design was based on an animal model (approved by the Institutional Animal Care and Use Committee) using 18 adult male New Zealand rabbits. METHODS This study included 18 male New Zealand rabbits, weighing 3.5 to 4 kg. Allogeneic bone marrow-derived MSCs were isolated and genetically modified with Bac-CB and Bac-CV seeded onto TCP scaffolds (MSC/Bac/TCP). The animals were divided into three groups according to the material implanted into the bilateral L4-L5 intertransverse space: TCP scaffold (n=6), MSC/TCP (n=6), and MSC/Bac/TCP (n=6). After 12 weeks, the rabbits were euthanized for radiographic examination, manual palpation, and histologic study. RESULTS Bilateral fusion areas in each animal were evaluated independently. The radiographic fusion rates at 12 sites were 0 of 12 in the TCP scaffold group, 4 of 12 in the MSC/TCP group, and 10 of 12 in the MSC/Bac/TCP group. By manual palpation, there were zero solid fusions in the TCP scaffold group, two solid fusions in the MSC/TCP group, and five solid fusions in the MSC/Bac/TCP group. Fusion rates were significantly greater in the MSC/Bac/TCP group. CONCLUSIONS The results indicate the potential of using baculovirus as a vector for gene/cell therapy approaches to improve bone healing and support the feasibility of using allogeneic MSCs for inducing bone formation and intertransverse process fusion.

The Preparation of Graphene Oxide-Silver Nanocomposites: The Effect of Silver Loads on Gram-Positive and Gram-Negative Antibacterial Activities

In this work, silver nanoparticles (Ag NPs) were decorated on thiol (–SH) grafted graphene oxide (GO) layers to investigate the antibacterial activities in Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Pseudomonas aeruginosa). The quasi-spherical, nano-sized Ag NPs were attached to the GO surface layers, as confirmed by using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), respectively. The average size of GO-Ag nanocomposites was significantly reduced (327 nm) from those of pristine GO (962 nm) while the average size of loaded Ag NPs was significantly smaller than the Ag NPs without GO. Various concentrations of AgNO3 solutions (0.1, 0.2, and 0.25 M) were loaded into GO nanosheets and resulted in the Ag contents of 31, 43, and 65%, respectively, with 1–2 nm sizes of Ag NPs anchored on the GO layers. These GO-Ag samples have negative surface charges but the GO-Ag 0.2 M sample (43% Ag) demonstrated the highest antibacterial efficiency. At 10 ppm load of GO-Ag suspension, only a GO-Ag 0.2 M sample yielded slight bacterial inhibition (5.79–7.82%). As the GO-Ag content was doubled to 20 ppm, the GO-Ag 0.2 M composite exhibited ~49% inhibition. When the GO-Ag 0.2 M composite level was raised to 100 ppm, almost 100% inhibition efficiencies were found on both Staphylococcus aureus (S.A.) and Pseudomonas aeruginosa (P.A.), which were significantly higher than using pristine GO (27% and 33% for S.A. and P.A.). The combined effect of GO and Ag nanoparticles demonstrate efficient antibacterial activities.

Computer-assisted fluoroscopic navigation of pedicle screw insertion

BACKGROUND Accurate placement of pedicle screws is difficult. PATIENTS AND METHODS We evaluated the feasibility and accuracy of pedicle screw insertion assisted by a real-time, 2-dimensional (2D) image-guided navigation system in 12 patients who underwent thoraco-lumbar and/or lumbar stabilization. 66 pedicle screws were inserted either by senior spine surgeons or residents. The accuracy of positioning of the screws was evaluated using postoperative plain radiographs and thin-cut CT. RESULTS 61 of the 66 screws were inserted successfully. 5 screw insertions showed structural violations: 4 on the medial and 1 on the lateral pedicle wall. The accuracy was higher in the sagittal plane than in the axial plain. There was no difference between the surgical error rates caused by the senior surgeons and the residents. INTERPRETATION Using computer-assisted 2D fluoroscopic image navigation, it is possible to achieve reliable and accurate pedicle screw insertion during low thoracic and lumbar spinal surgery.

Exposure of Prebiopsy Antibiotics Influence Bacteriological Diagnosis and Clinical Outcomes in Patients With Infectious Spondylitis.

AbstractThe benefit of prebiopsy empirical antibiotics for patients with infectious spondylitis and the effect on clinical outcome are not well known. This study assessed the impact of prebiopsy empirical antibiotics in patients with infectious spondylitis.We retrospectively reviewed 41 adult in-patients with infectious spondylitis who received percutaneous endoscopic debridement and drainage (PEDD) at a tertiary care hospital from August 2002 to August 2012. The average patient age was 55.2 years old and causative bacteria were identified in 32 out of 41 biopsy specimens (78.0%) via the PEDD procedure, which has good diagnostic efficacy comparable to open biopsy.Seventeen patients (41.5%) received prebiopsy empirical antimicrobial therapy, and these patients were less likely to have positive cultures than those who did not receive preoperative antibiotics (64.7% vs 87.5%, P = 0.04). Patients with positive cultures had a better infection control rate (78.1% vs 67.7%) and were less likely to undergo subsequent open surgery. Patients given preoperative antibiotics were more likely to need subsequent open surgery (35.3% vs 16.7%, P = 0.02). From multivariate logistic analysis showed age at diagnosis to be an independent risk factor for the need of further surgery. There were no major complications following the PEDD procedure, except 2 patients had transient paresthesia in the affected lumbar segments.Prebiopsy empirical antibiotic therapy was associated with lower positive culture rate and an increased need for subsequent open surgery. Patients with positive cultures were more likely to have initially adequate treatment, better infection control, and better clinical outcome.