Anterior Spine Research Articles

Evaluation of Perivascular Adhesion Formation in New Zealand White Rabbits Using Oxiplex and DuraSeal Xact Adhesion Barrier System.

BackgroundAdhesion formation after spine surgery is a result of normal wound healing that may place patients at increased risk for complications during revision surgery. Preventing adhesions could reduce the risk of complications during revision surgery, and possibly reduce the need for revision procedures. This study evaluates the ability of DuraSeal Xact Adhesion Barrier System (DSX) (Covidien, Mansfield, Massachusetts) and Oxiplex/SP gel (OX) (FzioMed, San Luis Obispo, California) to affect the extent and severity of postoperative perivascular adhesion development in an anterior spinal surgical rabbit model.MethodsWe determined the extent and severity of postoperative adhesion development 34 days after surgery in 12 male New Zealand White rabbits randomly assigned to intraoperative treatment with either DSX or OX, or to an untreated control group. Adhesion severity and extent were scored on scale from 0 (none) to 3 (severe).ResultsThe extent and severity of adhesions in the DSX group were significantly less than in the untreated control group. The DSX group mean extent score was 1.3 ± 0.5 (vs 2.5, P = .01) and the mean severity score was 1.25 ± 0.5 (vs 2.8, P = .005). The extent and severity of adhesions in the OX group were not significantly different from the control group.ConclusionIn this study, we found DSX to be the most effective compound in preventing adhesion formation after anterior spine surgery.Clinical RelevanceExtrapolating these results in rabbits to humans, less scarring between the major blood vessels could decrease the rate of complications in revision spine procedures.

Implant-related MRI artifacts of determined interbody test spacers: artifact calculations due to implant parameters in a porcine spine model

Aim: Intervertebral spacers for anterior spine fusion are made of different materials, which can affect the post-fusion MRI scans. Suscep- tibility artifacts specially for implants made of titanium alloys can decrease the image quality. This study focused on the influence of deter-mined implant parameters like shape and implant volume in MRI artifacting independent from se-lected MRI-sequences. Methods: In this study the post-implantation MRI scans of determined cuboids and cylinders were evaluated. All in-terbody test implants were made of titanium alloys. MRI scans were carried out by using T1 TSE sequences. The total artifact volume (TAV) of all examined implants were calculated for sta-tistical t-test correlation and implant volume (IV)/TAV-relation. Results: Considering all ex-amined test implants with an increasing implant size the TAV became significant larger (p<0,001) with simultaneous reduction of the respective IV/TAV-relation. According to an intergroup TAV- correlation for cylinders and cuboids with an equivalent implant volume the cylindric test im-plants demonstrated a significant smaller arti-fact range (p<0,05). Conclusions: Based on these results the MRI artifacts of larger test im-plants were more limited to the to the implant’s direct surroundings. In this connection for im- plants with identical material volumes a cylin- dric shape demonstrated more advantages con- sidering MRI artifacting than cubic forms.

Post Fusion MRI Artifacting - An In Vitro Study of Defined Intervertebral Test Spacers

Objectives: Interbody spacers for anterior spine fusion are made of different materials, which can affect the post-fusion MRI scans. Susceptibility artifacts specially for metallic implants can decrease the image quality. This study focused on the influence of determined implant parameters like shape and implant volume in MRI artifacting independent from selected MRI-sequences and implant materials. Material and methods: In this study we evaluated the post-implantation MRI scans of 3 determined titanium cuboids and 6 cylinders. MRI scans were carried out by using T1 TSE sequences. The total artifact volume (TAV) of all examined implants was calculated for statistical t-test correlation and implant volume (IV)/TAV-relation. Results: Considering all examined test implants with an increasing implant size the TAV became significantly larger (p < 0,001) with simultaneous reduction of the implant artifact relation. Regarding a TAV-correlation for cylinders with an implant volume equivalent to the cuboids significantly differences in MRI artifacting could be demonstrated (p < 0,05). Conclusion: Susceptibility artifacts are directly influenced by parameters which determine the implant size and volume. With regard to a more advantageous IV / TAV-relation for larger titanium implants the artifact rate was more limited to the implants direct surroundings. Significant differences with regard to the TAV could be determined in favor of a cylindric implant shape. The results demonstrated that the artifact rate of our used test implants is influenced by the material volume as well as implant shape. Keywords: Interbody test implants, MRI artifacting, implant parameters

Evaluation and Management of Abdominal Lymphoceles After Anterior Lumbar Spine Surgery

Case report. To examine the management of abdominal lymphoceles after anterior spine surgery and to review the existing literature on lymphoceles after access to the spine. Abdominal lymphoceles are a rare complication of anterior spinal approaches. Case report and review of the literature. In this article, we describe the management of 2 lymphoceles. In the first case, immediate operative drainage was required because of worsening abdominal pain and distention. In the second patient, conservative management was attempted, but the lymphocele ultimately persisted and required surgical intervention. Lymphoceles are often difficult to distinguish from ureteral injury, cerebrospinal fluid-leaks and hematomas using conventional imaging techniques. Although surgery remains the gold standard for the treatment of lymphoceles, expectant observation may be reasonable in some situations.

What's new in spinal surgery?

Fusion is now being performed such that the damage to surrounding tissues is minimized to maximize function around the fused segment. It is now possible to perform fusion to the anterior and posterior lumbar spine through minimally invasive approaches. Anterior fusion from the L4/5 disc space up into the thoracic spine via a retroperitoneal transpsoas approach can be performed with the patient in the lateral position using the Extreme Far Lateral Approach (XLIF, NuVasive, San Diego, USA). However, passing through the psoas is only possible because targeted motor monitoring is now available to prevent damage to the lumbar plexus. This technique is being used for stand alone fusions, spondylolisthesis and degenerate scoliosis. Previously more extensive surgery and different approaches meant that many patients were not fit enough to undergo fusion. The L5/S1 space can be fused anteriorly using the Transaxial ALIF approach (AXIALIF). This is a minimally invasive approach that is performed by passing instruments and a screw across the disc space via the presacral space behind the rectum. Both of these procedures can be supplemented with percutaneous posterior fixation using pedicle screws through tubes away from the midline. There is also continued interest in Posterior Lumbar Interbody Fusion and Trans Foraminal Interbody Fusion as ways of providing anterior fusion from a posterior approach; these are also becoming less invasive and destructive procedures. Total disc arthroplasty

Multislice Helical CT in the Diagnosis of Pharyngovertebral Fistula Due to Loosening of Anterior Screw-Plate Construct

Late dysphagia is a rare condition that results from hardware failure in anterior spine surgery patients. Dysphagia should be evaluated to find out the possible underlying causes. A barium swallow study and multislice helical computed tomography (CT) scan were used to evaluate a patient suffering from dysphagia 8 months after an anterior cervical fusion of C4-C7 vertebrae. A videofluoroscopic swallow study with a low-viscosity, high-density barium solution and different table tilt levels for obtaining slow passage of the barium meal revealed the existence of an esophagovertebral fistula with 2 ostia: one at the contact side of the screw and the other at a lower level with a pouch around the plate. A multislice helical CT scan provided volumetric data and multiplanar reconstruction that enabled us to delineate the extent of the abscess along the plate through the paravertebral space. It also showed the fistula location and relation of the fistula to the displaced screw, as well as the thickened retroesophageal soft tissue. Anterior spinal surgery patients should be followed carefully for progressive dysphagia. Videofluoroscopic swallow studies and multislice helical CT scans are efficient and complementary tools in the evaluation of late dysphagia.

Application of Epidemiology to Change Health Policy: Defining Age-Related Thresholds of Bone Mineral Density for Primary Prevention of Fracture

In Australia, benefits for antifracture therapies have been available for patients with osteoporosis and a prior fracture. No benefits were available to those with no prior fracture. We aimed to define, in women with no prior fracture, age-related thresholds of bone mineral density (BMD) associated with fracture risk equivalent to that of women with prior fracture and osteoporosis. A case-control study of women (≥50 yr) was conducted, including 291 fracture cases and 823 controls. BMD was measured at the proximal femur and posterior anterior (PA) spine. A fracture risk score (FRS) for the group with no prior fracture was calculated with discriminant analysis. The thresholds for equivalent fracture risk between those with no prior fracture and those with prior fracture were assessed using logistic regression. Increasing the FRS to +0.98 in women with no prior fracture resulted in equivalent odds of sustaining a fracture to those with prior fracture and osteoporosis. The corresponding T-score thresholds at the spine were −4.6 at 50 yr, −3.9 at 60 yr, −3.1 at 70 yr, and −2.4 at 80 yr. The femoral neck T-score thresholds were lower by 0.5 standard deviation. The high-risk individuals defined by this study should be considered for primary fracture prevention therapy.

NOTES Is Successful for Vertebral Spinal Interventions with Significant Advantages for Anterior Spinal Procedures

Introduction: Surgical vertebral spine procedures are currently performed via thoracoscopy and other percutaneous approaches. NOTES techniques allow easy access to the posterior mediastinum. Aims: To identify the technical challenges and to assess the feasibility of transesophageal thoracic spine bone biopsy in a porcine model. Methods: This study was approved by Animal Institutional Review Board. Four 50-kg pigs were intubated and underwent general anesthesia. A forward-viewing upper endoscope was advanced into the esophagus while in supine position. A needle knife was used to create a 15-mm long mucosal puncture in the esophageal wall followed by 3 cm long submucosal endoscopy with a mucosal flap, and scope passage into the posterior mediastinum. The pig was changed to prone position to facilitate visualization of the thoracic spine. After mediastinoscopy, 5-mm incisions were performed in the anterior longitudinal ligament using a needle knife at the level of proximal, middle, distal thoracic spine. A 19 g needle was advanced into the vertebral body and intervertebral space under fluoroscopic monitoring. Bone biopsy was performed using a 19 g needle or biopsy forceps. The endoscope was withdrawn and esophagotomy closed with T-bars. Pigs were euthanized immediately after translumenal closure for necropsy. Results: The posterior mediastinum was successfully accessed in all animals. There was spectacular visualization of anterior vertebral bodies throughout the thoracic spine. Using fluoroscopy specific spinal vertebra could be accurately identified. A needle knife was advanced about 1 cm into three vertebral bodies (T4, T8, T12) while avoiding adjacent structures. The intervertebral spaces were easily identified and dissected allowing access to the space. The hardness of bone tissue resulted in fragmented tissue samples. None of the pigs suffered any acute hemodynamic compromise during esophagotomy or bone biopsy. At necropsy, the sites of esophagotomy, biopsy and T-bars did not cause any visible adjacent organ or vascular damage. Conclusions: This is the first study to define the technical challenges and feasibility of NOTES vertebral spinal interventions. Trans-esophageal access and thoracic bone biopsy can be performed safely. The proximity of the esophagus to the vertebral column is favorable for NOTES procedures in the anterior thoracic spine, providing superior visibility and ease of access to the anterior spine compared to conventional surgical approaches allowing for intervertebral disc removal and replacement. Long-term survival studies are being performed with interventions in the thoracic and lumbosacral spine.

Mini-open anterior spine surgery for anterior lumbar diseases

Minimally invasive surgeries including endoscopic surgery and mini-open surgery are current trend of spine surgery, and its main advantages are shorter recovery time and cosmetic benefits, etc. However, mini-open surgery is easier and less technique demanding than endoscopic surgery. Besides, anterior spinal fusion is better than posterior spinal fusion while considering the physiological loading, back muscle function, etc. Therefore, we aimed to introduce the modified “mini-open anterior spine surgery” (MOASS) and to evaluate the feasibility, effectiveness and safety in the treatment of various anterior lumbar diseases with this technique. A total of 61 consecutive patients (46 female, 15 male; mean age 58.2 years) from 1997 to 2004 were included in this study, with an average follow-up of 24–52 (mean 43) months. The disease entities included vertebral fracture (20), failed back surgery (13), segmental instability or spondylolisthesis (10), infection (8), herniated disc (5), undetermined lesion for biopsy (4), and hemivertebra (1). Lesions involved 13 cases at T12–L1, 18 at L1–L2, 18 at L2–L3, 22 at L3–L4 and 11 at L4–L5 levels. All patients received a single stage anterior-only procedure for their anterior lumbar disease. We used the subjective clinical results, Oswestry disability index, fusion rate, and complications to evaluate our clinical outcome. Most patients (91.8%) were subjectively satisfied with the surgery and had good-to-excellent outcomes. Mean operation time was 85 (62–124) minutes, and mean blood loss was 136 (minimal-250) ml in the past 6 years. Hospital stay ranged from 4–26 (mean 10.6) days. Nearly all cases had improved back pain (87%), physical function (90%) and life quality (85%). Most cases (95%) achieved solid or probable solid bony fusion. There were no major complications. Therefore, MOASS is feasible, effective and safe for patients with various anterior lumbar diseases.

THORACOSCOPIC VERTEBRAL BODY REPLACEMENT WITH AN EXPANDABLE CAGE AFTER VENTRAL SPINAL CANAL DECOMPRESSION

Minimally invasive thoracic anterior surgery using a thoracoscopic approach has evolved to include spinal biopsy, debridement, discectomy, decompressive corpectomy, interbody fusions, and internal fixations. Minimal access techniques can potentially decrease surgical access morbidity and also reduce the time required for recovery and healing. The thoracoscopic approach for decompression, stabilization, and anterior vertebral reconstruction of thoracolumbar fractures is described. In this article and video, we discuss patient selection, surgical positioning, port placement, thoracic level localization, exposure and removal of fractured vertebral bodies, anterior vertebral column reconstruction using an expandable cage, instrumentation, and postoperative management. The potential advantages of using a minimally invasive thoracoscopic approach include direct trajectory to anterior spine pathology, minimal tissue and rib retraction, and decreased postoperative pain and length of hospital stay. The associated disadvantages include the steep learning curve for the surgeon, the need to operate with two-dimensional visual information and long instruments, and the requirement that one have an experienced surgical assistant. Minimally invasive surgery using a thoracoscopic approach for vertebral body replacement with an expandable cage can be performed safely. Expandable cages facilitate the vertebral body reconstruction via minimal access surgery.

Biomechanical Performance of Anterior Grafts in Lumbar Spine Surgery. A Comparative Finite-element Analysis

To study the biomechanical performance of various allografts and the effects of endplate treatment on a lumbar corporectomy model. A modified non-lineal tri-dimensional finite-element model of the lumbar spine was used, to which a set of transpedicular instruments was adapted. By means of a finite- element analysis, modeling was carried out of diaphyseal fragments of the femur, the tibia and the fibula. Four configurations were analyzed: with one femur, with one tibia, with three fibulas and with six fibulas. Four surfaces were evaluated that gave support to the graft according to the resection of the various components. Compression loads of 1,000 N were applied, as well as flexion, extension and rotation of 15 Nm respectively. The stresses and displacements caused were calculated. Full cartilage and subchondral bone resection is the configuration that least disrupts stresses within the adjacent vertebrae whereas the use of fibular fragments causes the greatest disruption. The use of the tibial bone gives rise to an asymmetry in the displacement area because of the shape of the said graft. The femur does not bring about a significant disruption of stresses in the adjacent vertebrae thereby constituting a more physiological construct. Preservation of the endplate's cortical bone does not lead to any biomechanical advantage in the reconstruction of the anterior spine. Femoral allografts are the most appropriate ones to replace the vertebral body, compared with the tibia or the fibula. Investigar el comportamiento biomecánico de diversos aloinjertos y el efecto del tratamiento del platillo vertebral en un modelo de corporectomía lumbar. Se utiliza un modelo modificado no lineal de elementos finitos en tres dimensiones de la columna lumbar al que se adaptó un instrumental transpedicular. Se modelaron por elementos finitos un fragmento diafisario de fémur, uno de tibia y uno de peroné. Se investigaron cuatro configuraciones: con fémur, con tibia, con tres peronés y con seis peronés. Se evaluaron cuatro superficies sobre las cuales se sustentaba el injerto en función de la resección de los distintos componentes. Se aplicaron fuerzas de compresión de 1.000 N, flexión, extensión y rotación de 15 Nm respectivamente. Se calcularon las tensiones y desplazamientos generados. La resección completa de cartílago y hueso subcondral es la configuración que menos altera las tensiones dentro de las vértebras adyacentes. El uso de fragmentos de peroné modifica en mayor medida las tensiones en las vértebras adyacentes. El uso de tibia genera una asimetría en los campos de desplazamiento debido a la forma de dicho injerto. Los resultados con fémur modifican en menor medida los estreses en las vértebras adyacentes, configurando un montaje más fisiológico. La preservación del hueso cortical del platillo vertebral no ofrece ninguna ventaja biomecánica en la reconstrucción de la columna anterior. El aloinjerto de fémur es el más adecuado para la sustitución del cuerpo vertebral, comparado con tibia y peroné.

Life-history strategies of Brachionus havanaensis subject to kairomones of vertebrate and invertebrate predators

We evaluated the different life-history strategies of the rotifer Brachionus havanaensis in the presence of vertebrate (salamander axolotl, Ambystoma mexicanum) or invertebrate (copepod Acanthocyclops robustus) predator using population growth and life-table demography at two algal food levels ($0.5\ imes 10^{6}$ and 1.0×106 cells ml−1 of Chlorella vulgaris). Generally, increased food availability resulted in higher densities of B. havanaensis. At any algal food level, B. havanaensis grown in the presence of kairomones showed higher population abundances than controls. Within the kairomone treatments, rotifers grown using A. mexicanum-conditioned medium showed a higher population growth than those using A. robustus medium. The average lifespan of B. havanaensis varied from 6 to 13 d, depending on the presence or absence of kairomones and the algal food density, the shortest being in treatments containing kairomones from Ambystoma. Gross (19–22 offspring female−1) and net reproductive rates (11 offspring female−1) were significantly higher in the Ambystoma-conditioned medium than in the other treatments including controls (9–10 and 6–7 offspring female−1, respectively). Generation time (4–6 d) was influenced by algal density as well as the presence of kairomones. B. havanaensis had the shortest generation time in Ambystoma-conditioned medium. The rate of population increase of B. havanaensis varied from 0.34 to 0.87 d−1, with higher values in treatments containing Ambystoma-conditioned water. The total lorica length, anterior, and posterior spine lengths of B. havanaensis were significantly higher in the presence of kairomones from both vertebrate and invertebrate predators than in controls. In general, there was a greater lorica and spine length of B. havanaensis due to Ambystoma infochemicals than those from Acanthocyclops.

Simulation of an anterior spine instrumentation in adolescent idiopathic scoliosis using a flexible multi-body model

Anterior spinal instrumentation is an alternative option to posterior instrumentation for surgical treatment of adolescent idiopathic scoliosis (AIS). However, optimal instrumentation configuration and strategies are not yet clearly defined. A biomechanical kinematic model using flexible mechanism was developed to study instrumentation strategies. Preoperative 3D reconstruction of scoliotic patient's spine was used to define the patient-specific geometry of the model. Mechanical properties were adjusted to consider the discectomy and surgical manoeuvres were reproduced. Anterior spine surgeries of ten patients were simulated and results were compared to immediate post-operative data and showed differences of <5 degrees for the Cobb angles. The validated model was used to find optimal instrumentation configurations for one patient prior to surgery. Six strategies were tested out of which the optimal one was identified while two were not recommended for surgery since screw forces exceeded published pullout forces. This study demonstrates the possibility to simulate anterior spine instrumentations.

Esophageal Perforation With a Locking Screw

A case report with a review of the literature. Anterior cervical spine surgery (ACS) has received widespread acceptance, and as a result, a variety of complications have been reported. Several cases of esophageal complications, arising from the use of various implants and grafts, have been described. The purpose of this article is to provide insight into the clinical presentation, diagnosis, types of involved implants, and the treatment of this entity. Previous reports of esophageal complications (esophageal perforation, diverticula, and stricture) after ACS are reviewed. Retrospective case study and literature review. Redundant locking screws should be removed due to the potential for extrusion into the esophagus. Regular, long-term follow-up of the patient undergoing anterior spine surgery is crucial. The wide range of possible complications mandates thorough workup. Early surgical treatment is imperative in the majority of esophageal complications.

Balloon-Assisted Endoscopic Retroperitoneal Gasless Approach (BERG) for Lumbar Interbody Fusion: Is it a Valid Alternative to the Laparoscopic Approach?

In the last years the use of interbody fusion devices with an anterior spinal lumbar approach has become a common procedure for the treatment of degenerative disc disease and spinal instability. We analysed our series of a simplified endoscopic approach to the anterior spine and made a review of the retroperitoneal endoscopically assisted approach to the anterior lumbar spine in the international literature. From 1999 through 2002, twenty consecutive "balloon-assisted endoscopic retroperitoneal gasless (BERG)" lumbar fusions were performed at San Filippo Neri Hospital in Rome, Italy. The surgical indications included patients with grade I or II spondylolisthesis and symptomatic degenerative disc disease with foraminal stenosis. Fourteen patients underwent a single level fusion (4 cases at L4-L5; 10 cases at L5-S1) and six patients underwent a double level fusion (L4-L5 and L5-S1). Mean operating time was 135 minutes (single level fusion), 175 minutes (double level fusion) and the mean intraoperative blood loss was 177 mL. No perioperative complications were observed and no procedure was converted to open surgical fusion. Patients were allowed to ambulate on the second postoperative day. Fusion was achieved in nineteen patients (fusion rate of 95%) 12 months after surgery. The BERG technique is a safe, effective, simplified, less technically demanding alternative approach when performing ALIF procedures, without the morbidity associated with laparoscopic or traditional approaches.

Retropharyngeal cerebrospinal fluid collection as a cause of postoperative dysphagia after anterior cervical discectomy

Background Transient dysphagia after anterior cervical discectomy is not uncommon. It is usually related to esophageal edema secondary to retraction, mechanical adhesions of the esophagus to the anterior spine, and stretch injuries to nerves involved in the swallowing mechanism. Structurally induced dysphagia, secondary to laceration of the neck viscera or to the presence of retropharyngeal masses, is by far less frequent, and it does not usually improve over time. Case Description The authors present the case of a 36-year-old woman who complained of severe dysphagia both for solids and liquids after C4 through C5 anterior discectomy and fusion, complicated by a millimetric dural tear of the anterior thecal sac. Postoperative neuroimaging revealed retropharyngeal fluid collection, extending in front of the vertebral bodies of C3, C4, and C5, exerting a mass effect on the posterior wall of the pharynx. Taking into account both the MRI aspect of the collection and the dramatic improvement of symptoms after lumbar punctures, we conducted a diagnosis of CSF collection in continuity with the subarachnoid space. The dysphagia and the CSF collection resolved with conservative therapy (bed rest and 3 lumbar punctures). Conclusion To the best of our knowledge, such a complication has never been described before in the literature. It should be included in the differential diagnosis of patients with postoperative dysphagia lasting more than 48 hours.

Postfusion Magnetic Resonance Imaging Artifacts Caused by a Titanium, Cobalt-Chromium-Molybdenum, and Carbon Intervertebral Disc Spacer

Intervertebral spacers for anterior spine fusion are made of different materials, such as titanium and CoCrMo-alloys or carbon fiber reinforced polymers (CFRP). Implant-related susceptibility artifacts can decrease the quality of magnetic resonance imaging (MRI) scans. This cadaveric study aimed to demonstrate the extent that implant-related MRI artifacting affects the postfusion differentiation of the spinal canal (SC) and intervertebral disc space (IDS). In 6 cadaveric porcine spines, we evaluated the postimplantation MRI scans of a titanium, CoCrMo-spacer and CFRP-spacer that differed in shape and surface qualities. A spacer made of human cortical bone was used as a control. A defined evaluation unit was divided into regions of interest (ROI) to characterize the SC and IDS. Considering 15 different MRI sequences read independently by an interobserver-validated team of specialists artifact-affected image quality of the median MRI slice was rated on a score of 0-1-2-3. A maximum score of 15 points for the SC and 9 points for the IDS (100%) was possible. Turbo spin echo sequences produced the best scores for both spacers and the control. Only the control achieved a score of 100%. For the IDS the CoCrMo-spacer, titanium and CFRP-spacer maximally scored 0%, 0% and 74%, for the SC 60%, 80% and 99%, respectively. By using favored T1 TSE sequences the CFRP-spacer represented clear advantages in postfusion spinal imaging. Independent of artifact dimensions the used scoring system allowed us to create an implant-related ranking of MRI scan quality in reference to the bone control.

Results of Vascularized Rib Grafts in Complex Spinal Reconstruction

The application of vascularized rib grafts in spine surgery has been limited to the treatment of kyphosis with anterior placement of the rib graft to facilitate anterior spine arthrodesis. The outcomes following use of vascularized rib grafts in complex spinal reconstruction have not been adequately evaluated. The purpose of this study was to determine the results, including the time to osseous union and complications, following anterior or posterior placement of pedicled vascularized rib grafts for complex spinal reconstruction. The medical records and images of all patients in whom a vascularized rib graft had been used for a multisegmental spine reconstruction at a single institution between 1994 and 2004 were retrospectively reviewed. Eighteen patients (mean age, 45.3 years) who had been followed for an average of 31.8 months were identified. Details regarding indications, the levels that were spanned, the graft length, the time to union, and complications were evaluated. The preoperative diagnoses included metastatic or primary tumor (thirteen patients) and progressive kyphosis secondary to chronic osteomyelitis (two), injury (one), congenital anomalies (one), or implant failure (one). On the average, 4.4 levels were fused and 1.9 vertebral bodies were excised. All eighteen arthrodeses included various forms of allograft and/or autograft material, and instrumentation was used, in addition to the vascularized rib graft, in twelve patients. The mean rib length was 16.1 cm, and a rib between the fifth and eleventh ribs, inclusive, was used, depending on the location of the spinal reconstruction. The average time to union was 6.8 months, and all rib grafts united. There were no complications specific to the rib-harvesting procedure. The use of a vascularized rib graft in complex spinal reconstruction adds little time to the overall procedure, is associated with low morbidity, and appears to offer substantial benefits to the patient.

A CT-free, intra-operative planning and navigation system for minimally invasive anterior spinal surgery – an accuracy study

Objective: A comprehensive study was performed to evaluate the accuracy of a newly developed CT-free, intra-operative planning and navigation system for anterior spine surgery.Materials and Methods: Instruments and an image intensifier were tracked using the SurgiGATE® navigation system. A laboratory study was performed on 27 plastic vertebrae. Fiducial markers were implanted in the vertebrae for accuracy evaluation purposes, and a dynamic reference base was placed on the vertebrae to establish a patient coordinate system (P-COS). Two fluoroscopic images were used for intra-operative planning. The graft bed plan was recorded in P-COS, followed by surgical formation of the graft bed, which was visualized. To evaluate the accuracy, the vertebrae were scanned with CT, and the markers were used to calculate an accurate paired-point registered transformation between the CT coordinate system and P-COS.Results: Using the new SPO module, accurate planning and navigation of a resection of the vertebral body is possible using two fluoroscopic images. The overall mean error between the planned resection volume and the actual resection was 0.98 mm. In addition, the module can serve as an educational tool for training spine surgeons.Conclusions: The new fluoroscopy-based system can be used safely for accurate performance of anterior resection during spondylodesis. New methods for safe and accurate registration during anterior spine surgery need to be developed.

THE CLASSIC: Surgical Treatment of Fresh Injuries to the Major Ligaments of the Knee

THE CLASSIC: Surgical Treatment of Fresh Injuries to the Major Ligaments of the Knee