Summary. Optimum position of pedicle screws can be determined preoperatively by CT based planning. We conducted a comparative study in order to analyse manually determined pedicle screw plans and those that were obtained automatically by a computer software and found an agreement in plans between both methods, yet an increase in fastening strengths was observed for automatically obtained plans. Hypothesys. Automatic planning of pedicle screw positions and sizing is not inferior to manual planning. Design. Prospective comparative study. Introduction. Preoperative planning in spinal deformity surgery starts by a proper selection of implant anchors throughout the instrumented spine, where pedicle screws provide the optimum choice for bone fixation. In the case of severe spinal deformities, dysplastic pedicles can limit screw usage, and therefore studying the anatomy of vertebrae from preoperative images can aid in achieving the safest screw position through optimal fastening strength. The purpose of this study is to compare manually and automatically obtained preoperative pedicle screw plans. Materials and Methods. CT scans of 17 deformed thoracic spines were studied by two experienced spine deformity surgeons, who placed 316 pedicle screws in 3D using a software positioning tool by aiming for the safest trajectory that permitted the largest possible screw sizes. The resulting manually obtained screw sizes, trajectory angles, entry points and normalised fastening strengths were compared to those obtained automatically by a dedicated computer software that, basing on vertebral anatomy and bone density in 3D, determined optimal screw sizes and trajectories. Results. Statistically significant differences were observed between manually and automatically obtained plans for screw sizes (p < 0.05) and trajectory angles (p < 0.001). However, for automatically obtained plans, screws were not smaller in diameter (p < 0.05) or shorter in length (p < 0.001), while screw normalised fastening strengths were higher (p < 0.001). Conclusions. In comparison to manual planning, automatically obtained plans did not result in smaller screw diameters or shorter screw lengths, which is in agreement with the definition of the pull-out strength, but in different screw trajectory angles, which is reflected by higher normalised fastening strengths. Captions. Fig. 1. Visual comparison among automatically obtained (green colour) and manually defined pedicle screw placement plans by two experienced spine surgeons (red and blue colour) for three different patients with adolescent idiopathic scoliosis, shown from top to bottom in a three-dimensional view, left sagittal, right sagittal and coronal view. Fig. 2. Histograms of differences between observers and (left column), between observer and automated method (middle column), and between observer and automated method (right column), shown from top to bottom for differences in pedicle screw pedicle screw diameter, sagittal inclination, and normalised fastening strength. For figures/tables, please contact authors directly.

Purpose. To question the reliability of Thoracic Spine pain as a red flag and symptoms of a possible cause of Serious Spinal Pathology (SSP). Methods. The clinical notes and Magnetic Resonance Imaging (MRI) results of patients presenting to the Sheffield Spinal Service with Thoracic spine symptoms but no signs were retrospectively reviewed over the period of 2 year (September 2008-August 2010). The clinical reason for request of Thoracic MRIs were noted and the patient notes were reviewed to determine their presentation, length of time of symptoms, age and also it was noted whether any other recognized red flag symptoms were present. Exclusion criteria consisted of patients referred with known SSP or myelopathic symptoms. Results. 57 thoracic spine MRI requests were made in total by the orthopaedic spinal teams for patients presenting with thoracic spine pain in the time period. 8 patients were excluded as per criteria as they were referred with known SSP as were 4 other patients with a history of previous cancer. 45 patients presented with thoracic spine pain but no other red flag signs or symptoms of these none had MRI evidence of serious spinal pathology or indeed anything pathological indicating the cause of their symptoms. Conclusion. The majority of those presenting to orthopaedic spinal clinic with thoracic spine pain alone with no other red flag signs have no pathological cause. Thoracic pain is a widely accepted indicator (red flag) of potential serious spinal pathology. The findings from this review would not support thoracic pain alone as an indicator of SSP

The Biometrics Flexible Electrogoniometer (FEG) is a lightweight device which when attached over joints can record angular displacements for periods of up to 10 hours. The aim of this study was to examine the validity of the FEG for measuring the thoracic spine using the Cobb angle and functional activities. 12 subjects (6 F, 71±11years; 6 M, 65±11) were X-rayed in upright and “slumped” standing with the FEG attached to their thoracic spine. Three Cobb angles were obtained from the vertebrae underlying the FEG at the outer margins (OEB); the inner margins (IEB), and the mid points (MEB), of the FEG end blocks. Comparisons of FEG and Cobb angles were derived with intraclass correlation coefficients (ICC). In a separate experiment, 12 subjects (8F, 43±13; 4M, 35±17) performed 7 functional activities one week apart in order to assess day-to-day reliability of the FEG. Time 1 and time 2 angles were compared with an ICC. The mean FEG angles for upright and “slumped standing” were 31±7° and 39±8° (mean ± SD) respectively. The corresponding mean OEB Cobb angles were 48±13° and 52±12°; the mean IEB Cobb angles were 24±11° and 29±10°; and the MEB Cobb angles were 36±13° and 41±10°. The correlation between the FEG and OEB Cobb was ICC(2,1)=0.85; between FEG and IEB Cobb was ICC(2,1)=0.77 and between FEG and MEB Cobb was ICC(2,1)=0.87. The second experiment compared day-to day reliability of the FEG when used over the thoracic spine. For the 7 activities performed: standing erect, standing slumped, reaching up, reaching down, and walking on-the-spot, the mean correlation between the measures on day 1 and day 2 was ICC(2,1)=0.96 (range 0.94 to 0.98). This study has shown that the FEG demonstrates excellent internal and external validity in the thoracic spine. Further, it has demonstrated that the FEG measures the segment of the spine between the mid-endblocks. Future studies are planned which will use the FEG to evaluate interventions aimed at treating thoracic kyphosis

The thoracic spine has always been associated with a stability that is considerably augmented by the rib cage and associated ligaments. Fractures of the thoracic spine require great forces to be applied, causing high levels of other injuries. In addition, the narrow spinal canal dimensions result in high levels of neurological compromise when fractures occur. Between 2 February 1995 and 21 March 2001, 1249 patients were admitted to our spinal tertiary referral unit. Of these, 77 had suffered fractures to some part of their upper thoracic spine (T1-T6), of which 32 required surgical procedures. Using patient case notes, we retrospectively studied this series. 26 of the 32 patients were male, with an average age of the group of 24.4 ± 11.3 years and an average inpatient stay of 17.5 ± 10.5 days. 29 patients suffered fractures at more than one level and 23 patients suffered complete neurological compromise. Only 2 patients were neurologically intact. 90.7% sustained their injuries in road traffic accidents, with 53.9% of the male group being involved in motorcycle accidents. Multiple imaging (in addition to plain film radiography) was required in 30 cases with 20 patients suffering injuries apart from their spinal fracture. Of these, 15 had associated chest injuries. Cardiothoracic surgical consultations were required in 56.3% of cases, and from the general surgeons in 37.5% of patients. 59.4% of patients required intensive care unit therapy, with another 4 patients going to the high dependency unit. Fractures to the upper thoracic spine are injuries with devastating consequences, both due to high levels of neurological compromise and concomitant injuries. This series would suggest that patients suffering from these injuries are best treated in a multi-disciplinary approach within a general setting, rather than in a specialist orthopaedic unit, where other medical and surgical services may not be readily available

The aim of the present study was to record the MRI characteristics of the thoracic spine in asymptomatic adult males and their correlation with age and thoracic level. A cross sectional retrospective study was designed in order to record MRI thoracic spine findings in asymptomatic adult males, 35 to 65 years of age. All study participants were evaluated by MRI. The qualitative and quantitative assessed MRI parameters were as follows: disc degeneration (disk signal intensity), bulging, herniation, disc height, Modic changes, endplate irregularities, osteophytes. Intervertebral disc signal was decreased more in the lower thoracic spine (T6-T12 level). In addition there was a strong correlation between disc degeneration (disc signal loss) and the age of the study participants. Disc bulging was most frequently observed anteriorly than posteriorly with the prevalence increased caudally. Modic changes were not so frequent and there were most commonly seen in the lower thoracic spine (T11-T12 level). In addition osteophytes were larger anteriorly than posteriorly and their prevalence increased caudally. Endplate irregularities (Schmorl nodes) were more common in the upper endplates and in the lower thoracic spine (T6-T12 level). Finally strong positive correlation was noted between osteophytes, anterior and posterior and disc bulging. This study documents the mild to moderate grade of degenerative changes especially in the lower thoracic spine (T6-T12 level) of asymptomatic adult males, 35 to 65 years of age

Combined anterior/posterior scoliosis surgery is the mainstay of scoliosis surgery in large curves with Cobb angle more than 65°, in stiff curves that correct to above 40° only on the pre-operative bending films and in Steersman’s kyphosis greater than 90°. The combined anterior/posterior scoliosis surgery allows better correction of the curve, saving motion segments in the spine and eliminating the occurrence of the crankshaft phenomenon. Video-assisted spinal surgery (VATS) and Mini open thoracotomy, thoracoscopically assisted (MOT-TA) allow for the performing of multi level discectomies and soft tissue release, as an anterior adjunct to posterior spine fusion, through minimal approach to the thoracic spine in scoliosis surgery. During the last year we have begun using the MOT-TA for anterior thoracic spine release and fusion, as the first step in releasing, reducing, and fusing large and stiff scoliotic curves, utilizing standard surgical instrumentation and techniques. Materials and Methods: Mini-Thoracotomy Thoracoscopic Assisted was performed on 15 patients, age 4 to 48 (mean 20 years old) between January 2000 to present. There was a female predominance (12:3). In the group, 13 patients were scoliosis patients and 2 were kyphosis patients. All patients underwent anterior release and discectomy before performing posterior fusion. A mean of 4 discs (range 3 to 5 discs) was excised at surgery. The mean Cobb angle was 62°. No anterior instrumentation was placed in the first 14 cases. In case No. 15 an anterior crew-rod construct was placed through the mini thoracotomy incision. Technique: MOT-TA is performed with the patient positioned in a lateral decubitus with the convex side of the scoliotic curve up through a 5–7 cm skin incision above the apical vertebra obliquely from the posterior to the middle axillary line. Results: There was a short learning curve associated with the technique, which proved to be an easy and straight forward surgical technique. Pre-operative thoracic Cobb angle measured 50°–80° (average 62°) that bends to 30°–66° on the pre-operative thoracic bend films (average 45°). The pot-operative thoracic Cobb angle measured 15°–38° (average 28°). The overall curve correction was 59% on average. The anterior soft tissue releases and discectomies were a quick and relatively “dry” part of the surgery. Estimated blood loss ranged 50–800cc, less than a quarter of the total intra-operative blood loss averaging 220cc out of 1227cc of the total EBL. Anterior surgery time ranged 100 to 170 min averaging 147min for mean of 6.1 discs (range 4 to 9 discs). When compared to the total operative time, the anterior part of the surgery took about a 1/3 of the total surgery time. Discussion: The results of the study show that the mini open thoracotomy, thoracoscopically assisted, for anterior thoracic spine release and discectomies is a fast, easy to learn technique with a short learning curve leading to complete anterior release, short operative time, allowing same day front and back surgery with no difficulty in performing internal thoracoplasty that results in structural and cosmetically superior outcome. In the hands of an experienced surgeon, the usage of VATS could be an effective and beneficial in scoliosis surgery; however, in the case of less experienced surgeon, who has no experience in thoracoscopic surgery, the MOT-TA could be an elegant and useful way to perform the technically demanding anterior discectomies and releases in severely deformed and rigid scoliotic spine. In our last case we have demonstrated the ability to instrument the anterior spine utilizing the same mini thoracotomy incision, this advance will be carried further to more extensive instrumentation in the future. In conclusion: Mini open thoracotomy, thoracoscopically assisted, for anterior thoracic spine release and fusion is a faster, easier, cosmetically superior and surgically justified procedure

In multilevel posterior cervical instrumented fusions, extending the fusion across the cervico-thoracic junction at T1 or T2 (CTJ) has been associated with decreased rate of re-operation and pseudarthrosis but with longer surgical time and increased blood loss. The impact on patient reported outcomes (PROs) remains unclear. The primary objective was to determine whether extending the fusion through the CTJ influenced PROs at 3 and 12 months after surgery. Secondary objectives were to compare the number of patients reaching the minimally clinically important difference (MCID) for the PROs and mJOA, operative time duration, intra-operative blood loss (IOBL), length of stay (LOS), discharge disposition, adverse events (AEs), re-operation within 12 months of the surgery, and patient satisfaction. This is a retrospective analysis of prospectively collected data from a multicenter observational cohort study of patients with degenerative cervical myelopathy. Patients who underwent a posterior instrumented fusion of 4 levels of greater (between C2-T2) between January 2015 and October 2020 with 12 months follow-up were included. PROS (NDI, EQ5D, SF-12 PCS and MCS, NRS arm and neck pain) and mJOA were compared using ANCOVA, adjusted for baseline differences. Patient demographics, comorbidities and surgical details were abstracted. Percentafe of patient reaching MCID for these outcomes was compared using chi-square test. Operative duration, IOBL, AEs, re-operation, discharge disposittion, LOS and satisfaction were compared using chi-square test for categorical variables and independent samples t-tests for continuous variables. A total of 206 patients were included in this study (105 patients not crossing the CTJ and 101 crossing the CTJ). Patients who underwent a construct extending through the CTJ were more likely to be female and had worse baseline EQ5D and NDI scores (p> 0.05). When adjusted for baseline difference, there was no statistically significant difference between the two groups for the PROs and mJOA at 3 and 12 months. Surgical duration was longer (p 0.05). Satisfaction with the surgery was high in both groups but significantly different at 12 months (80% versus 72%, p= 0.042 for the group not crossing the CTJ and the group crossing the CTJ, respectively). The percentage of patients reaching MCID for the NDI score was 55% in the non-crossing group versus 69% in the group extending through the CTJ (p= 0.06). Up to 12 months after the surgery, there was no statistically significant differences in PROs between posterior construct extended to or not extended to the upper thoracic spine. The adverse event profile did not differ significantly, but longer surgical time and blood loss were associated with construct extending across the CTJ

Consecutive case series. To evaluate the efficacy of a strict stepwise radioanatomical procedure protocol in avoiding neurological complications through tool malplacement in fluoroscopy guided percutaneous procedures of the thoracic spine. Fluoroscopy guided percutaneous access to thoracic vertebral bodies is technically demanding. There is a trend towards computed tomography (CT) guidance on grounds of perceived lesser risk of spinal canal instrument malplacement. CT is however not always readily accessible and a safe technique for fluoroscopy guided procedures therefore desirable. 350 consecutive fluoroscopy guided percutaneous procedures (biopsy, vertebroplasty or kyphoplasty) covering all thoracic vertebral levels T1-T12 were performed according to a strict stepwise radioanatomical protocol. The crucial step of the protocol was not to advance the tool beyond the anterior-posterior (ap) projection of the medial pedicle wall until the tip of the instrument had been verified to have reached the posterior vertebral cortex in the lateral projection. The neurological status of patients was assessed through clinical examination prior to, immediately after the procedure and before discharge. Percutaneous instrument placement in the targeted thoracic vertebral body was achieved in all cases and the stepwise radioanatomical protocol was followed in all cases. There was no case of neurological deterioration in the case series. Conclusion: Attention to radiographic landmarks, specifically not crossing the ap projection of the medial pedicle cortex prior to reaching the posterior vertebral wall in the lateral projection, allows neurologically safe performance of fluoroscopy guided percutaneous procedures of the thoracic spine. This simple protocol is particularly useful when access to CT is limited

Introduction/Aim. Intra-operative localisation of thoracic spine levels can be difficult due to anatomical constraints such as scapular shadow, patient's size and poor bone quality. This is particularly true in cases of thoracic discectomies in which the vertebral bodies appear normal. We describe a simple and reliable technique to identify the correct thoracic spine level. Methods. After induction of general anaesthesia, the patient is placed prone and the pedicle of interest is identified using fluoroscopy. A ‘K’ wire is then inserted percutaneously into this pedicle under image guidance (confirmed in the antero-posterior (AP) and lateral views). The ‘K’ wire is then cut flush and the patient is then positioned laterally and the intended procedure is performed. Results. We routinely use this technique in all our thoracic discectomies. Placing the ‘K’ wire into a fixed point like the pedicle, facilitates rapid intra-operative viewing of the level of interest and is removed easily at the conclusion of surgery. Conclusion. Per-operative placement of the ‘K’ wire avoids the patient undergoing two procedures as some of the other invasive techniques have described in the literature for correct level identification. Furthermore, this technique is simple and requires no more ability than placing an implant in the pedicle under fluoroscopy. It has the added advantage of reducing anaesthetic, surgery and fluoroscopy time

Thoracic spine fractures and fracture dislocations often lead to neurological deficit, and associated injuries to morbidity and mortality. An audit conducted between January 1999 and December 2000 evaluated the outcome of 63 patients with fractures and fracture dislocations of the thoracic spine. The mean age of patients, 41 of whom were male, was 30 years. In 45 patients the injury was sustained in a motor vehicle accident, and 23 patients had associated injuries. We used the Margel radiological classification. There were 37 fracture dislocations and 23 pure fractures. Twenty patients had a type-A injury (flexion), of which 19 were type AIII (burst). There were 40 patients with a type-B injury, 35 of which were type BI (flexion distraction), and three type BIII (flexion and axial loading). In three patients there was a type-C injury (rotational). There was total neurological deficit in 39 patients, 10 with type-A, 26 with type-B and three with type-C injuries. Fifteen patients had partial neurological deficit and nine were neurologically intact. Posterior spinal fusion and bone graft was performed on 43 patients, anterior decompression and bone graft without instrumentation on seven, and combined anterior and posterior surgery on one. The remaining 12 were treated conservatively with orthoses. The neurological status of eight patients improved by a single grade following surgery and the neurological status of two following conservative treatment. Of the 54 patients with neurological deficit, 52 were wheelchair-bound. The poor neurological outcome was comparable to that in other studies

Aim:. Historically, anterior decompression followed by posterior fusion has been the surgical management of choice in spinal tuberculosis. Due to theatre time being at a premium, we have evolved to performing anterior only debridement, allograft strut reconstruction and instrumentation for tuberculosis in the adult thoracic spine. The aim of this study is to review the safety and the efficacy of this treatment. Methods:. Twenty-eight adult thoracic tuberculosis patients were identified where anterior only surgery had been performed. These were all in the mid-thoracic spine as circumferential surgery is still favoured in thoracolumbar disease. The surgery was performed by a single surgeon at a tertiary hospital. Following transthoracic aggressive debridement, allograft humeral shafts were cut to size and inserted under compression and the spines instrumented with the use of screw-rod constructs into the body above and below. A retrospective review of clinical notes and radiological studies was performed. Results:. Twenty-seven of the patients presented with altered neurology; 2 had only sensory changes while 25 presented with paraparesis; 22 of these patients were unable to walk. The average surgical time was 2 hours 20 minutes with a median blood loss of 726 ml. The majority of patients had 2 vertebral bodies involved and required an average of a 4 body fusion. Surgical complications included inadvertent opening of the diaphragm in 1 patient and 1 patient deteriorated neurologically post operatively. 21 of 28 patients recovered to independent mobility at their latest follow-up appointment. 1 patient showed no recovery, 3 had some motor recovery that was not useful, 1 had some sensory but no motor recovery. 16 of 28 patients have documented bony fusion with no evidence of instrumentation failure in any patients. Conclusion:. Anterior only debridement, allograft strut reconstruction and instrumented fusion for the treatment of thoracic spinal tuberculosis is a safe and effective alternative to circumferential surgery in the adult patient

The use of cervical pedicle screws as anchors in posterior reconstruction surgery has not been widely accepted due to the neurological or vascular injury. We thus sought to investigate the accuracy of free-handed pedicle screw placement in the cervical and upper thoracic spine at the early stage of clinical application. Eight patients (five males and three females) were included in this study. Mean age was 63 years (31 to 78 years). There were three patients with rheumatoid arthritis, three with cervical fracture-dislocation, and two with spinal metastasis. Twenty-four pedicle screws (3.5 mm diameter: Vertex, Medtronic Sofamordanek) were placed into the pedicle from C2 to T2 level by free-handed technique2). Grade of breaching of pedicle cortex was divided into four groups (Grade 0–3). In addition, screw axis angle (SAA) were calculated from the horizontal and sagittal CT images and compared with pedicle transverse angle (PTA). Furthermore, perioperative complications were also examined. Our free-handed pedicle screw placement with carving technique is as follows: A longitudinal gutter was created at the lamina-lateral mass junction and then transverse gutter perpendicular to the longitudinal gutter was made at the lateral notch of lateral mass. The entry point of the pedicle screw was on the midline of lateral mass. Medial pedicle cortex through the ventral lamina was identified using the probes to create the hole within the pedicle. The hole was tapped and the screw was gently introduced into the pedicle to ensure the sagittal trajectory using fluoroscopy. In the transverse direction, 22 out of 24 screws (92%) were entirely contained within the pedicle (Grade 0). In contrast, only teo screws (8%) produced breaches less than half the screw diameter (Grade 1). In the sagittal direction, all screws were within the pedicle (Grade 0). Screw trajectories were not consistent with anatomical pedicle axis angle; the mean SAA were smaller than the mean PTA at all levels. The pedicle diameter ranged from 3.9 to 9.2 mm. The mean value gradually increased toward the caudal level. There were no neurological and vascular complications related to screw placement

The thoracoscopic technic is a minimal surgical approach that minimizes the skin, muscle and ribs trauma without altering the effectiveness of the treatment. This type of surgery has been gaining importance due to its advantages: excellent lighting, visualization and magnification. It offers an acute visual control during manipulation and dissection of delicate structures. We aim to assess the anterior release and the thoracic spine arthrodesis through thoracoscopic approach and measure the effectiveness and security of anterior thoracoscopic instrumentation in an experimental study in pigs. The study was performed on 18 pigs which weighed between 40 and 60 kg. The surgical procedures were conducted at the Hospital Italiano in Buenos Aires. A thoracoscopic surgery was performed as an access to the spine. The quality of the anterior release ranged significantly from cases in which the incision of the common anterior vertebral ligament could not be finished to cases in which more than 75% of the anterolateral disk circumference was released. In the subjective thoracoscopic assessment of the surgeon the screws were placed successfully in all The radiographic assessment confirmed the surgeon’s presumption, all the screws had been placed correctly. The rod presented complications in several cases. The radiographic assessment showed that 40.6% (13 patients) of the disc spaces were pseudoarthrosic or with a delayed union. The macroscopic examination confirmed this finding and raised the number of pseudoarthrosic spaces up to 46.8% (15 patients) revealing 4 discs that still had a nucleus pulposus. The data were reinforced by histologic examination. This histologic cuts were performed using the E & O method. The fibrous ring was clearly identified in the pseudoarthrosic cases as well as the processes of the osteochondral bone formation in its different phases of maturation. It is very important to highlight that in our experience we had found a direct relationship between the quality of the disectomy, the fusion technique and the experience of the surgeon. The surgical technique, the rod placement on the screws needs proper positioning and depth. The radiographic and microscopic examination confirmed that the posterior longitudinal ligaments was not damaged. The thoracoscopic instrumentations in pigs using a rod and screws of third generation is a secure technique. It is essential the development of instrumentation which allows effective thoracoscopic distraction and compression

Introduction: The use of anterior vertebral staples in the fusionless correction of scoliosis has received increased attention in recent literature. Several animal studies have shown stapling to be effective in modulating vertebral growth. In 2005 Betz (1) published the only clinical series to date. Despite the increasing volume of literature suggesting the efficacy of this treatment, little is known about it’s biomechanical consequences. In 2007 Puttlitz (2) measured the change in spinal range of motion after staple insertion in a bovine model. They found a small but statistically significant decrease in range of motion in axial rotation and lateral bending. The clinical significance of this is questionable as the differences were only a few degrees over three vertebral levels. A well designed biomechanical evaluation of the effects of staple insertion on spinal stability is needed. The aim of this study was to evaluate the effect of insertion of a laterally placed anterior vertebral staple on the stiffness characteristics of a single motion segment.

Methods: Four-pronged shape memory alloy staples were inserted into fourteen individual bovine thoracic motion segments. A displacement controlled six degree-of-freedom robotic facility was used to test control and staple constructs through a pre-determined range of motion in flexion, extension, lateral bending, and axial rotation. All data were synchronised with robot position data and filtered using moving average methods. The stiffness in each condition was calculated in units of Nm/degree of rotation. Paired t-tests were used to compare results.

Results: Stiffness measurements in the control condition correlated with previously published measures (3). A significant decrease in stiffness (p< 0.05) following staple insertion was found in flexion, extension, lateral bending away from the staple, and axial rotation away from the staple. Stiffness for axial rotation towards the stapled side was significantly greater than for away. A near significant increase in lateral bend stiffness away from the staple compared with towards was also seen.

Discussion: These results suggest that staple insertion consistently decreased stiffness in all directions of motion. This is contrary to the results of Puttlitz (2), which reported a reduced range of motion (i.e. increased stiffness) for some motions using moment-controlled testing. This decrease in stiffness could not be explained by changes in anatomy or tissue properties between specimens, as each stapled motion segment was compared with its own intact state. Addition of the staple would intuitively be expected to increase motion segment stiffness, however we suggest that the staple prongs may cause sufficient disruption to the vertebral bodies and endplates to slightly reduce overall stiffness. Hence, growth modulation may be achieved through physical disruption of the endplate, rather than static mechanical stress. Further research is planned to investigate the proportion of load carried by the staple during spinal movement and the anatomical effect of the staple on the physis. In conclusion, anterior vertebral stapling causes a slight but significant decrease in the stiffness of treated motion segments.

PURPOSE: To record our experience in surgical treatment of thoracic spine fractures with posterior stabilization, decompression and ligamentotaxis.

MATERIALS AND METHODS: From January 2000 until July 2006, 67 patients (48 males and 19 females), aged 16 to 85 years old (average 41,2 y.o) were surgically treated in our department due to thoracic spine fractures. Preoperative X-Ray and CT scan were used in all cases while in most of the cases we performed MRI to further evaluate the damage. In all cases we performed decompression and posterior stabilization using four different hardware types and whenever possible ligamentotaxis. Continuous electrophysiological monitoring was alo ued in all operations. We recorded the pre- and postoperative neurological status, the vertebral height loss, the kyphotic angle and spinal canal occupation. Moreover we recorded the average hospitalization time, the transfusion needs as well as major and minor complications. At the follow-up we measured the loss of correction at 3, 6 and 12 months postoperatively. The follow up ranged from 4 to 48 months.

RESULTS: Neurological damage was recorded in 43 % of the patients. The average preoperative kyphotic angle was 38.2° while the average spinal canal occupation was 29.8 %. The immediate postoperative correction was 16.7 °. During the follow-up we observed small, insignificant loss of correction. There were no major complications.

CONCLUSION: In cases of thoracic spine fractures the surgical treatment with posterior stabilization and ligamentotaxis is offering significant stability and adequate long term results.

A prospective cohort outcome evaluation of unstable thoracic spine fractures treated with posterior pedicle screw fixation. The purpose of this study was to determine the accuracy of placement and safety of pedicle screws in open reduction of unstable thoracic spine fractures. The surgeries were performed by one of five fellowship trained spinal surgeons. CT scans were formed on twenty-three patients totaling two hundred screws using 3mm cuts. Three independent reviewers assessed and categorized the screw position as within the pedicle or as a violation of the pedicle wall. 98% of the screws were accurate and we recommend the use of pedicle screws in thoracic fractures .

A prospective cohort outcome evaluation of unstable thoracic spine fractures treated with posterior pedicle screw fixation.

This study is to determine the accuracy of placement, safety of pedicle screws in open reduction of unstable thoracic spine fracture

Surgery was performed by one of five fellowship trained spine surgeons. CT scans were performed on twenty-three patients using 3mm cuts in both sagittal and transverse planes. Pedicle screw position was assessed by three independent reviewers. Screw position was categorized as within the wall of the pedicle or in violation of the wall. Further sub-classification of pedicle wall violation reviewed the direction and distance of perforation. Independent perioperative and postoperative surveillance for complications was done.

Twenty-three unstable thoracic spine fractures treated with two hundred posterior pedicle screws were analyzed. The pedicle screws spanned from T1-T12 with the majority of screws in the mid-thoracic region. Of the two hundred thoracic pedicle screws placed, 70% were fully contained within the pedicle wall. The remaining screws were deemed “out” with cortical perforation (30%). Of these, 20% were lateral perforations, 5% were medial perforations and 5% were anterolateral perforations. No superior, inferior, or anteromedial perforations were found. There was no regional area variation in incidence of perforations. 10% of all perforations were directly related to pedicle diameter to screw diameter mismatch. There were no adverse neurological, vascular, or visceral injuries detected intraoperatively or postoperatively.

Surgical management of unstable thoracic spine fractures with posterior pedicle screw fixation is safe. 98% of screws had satisfactory accuracy. Although very minor misplacement of pedicle screws occurred, there were no complications and we recommend the use of pedicle screws in thoracic fractures.

Purpose: The mechanical integrity of vertebral bone is compromised when metastatic cancer cells migrate to the spine, rendering it susceptible to burst fracture under physiologic loading. Risk of burst fracture has been shown to be dependent on the magnitude of the applied load, however limited work has been conducted to determine the effect of load type on the stability of the metastatic spine. The objective of this study was to evaluate the effect of multiple loading conditions and the presence of the ribcage on a metastatically-involved thoracic spinal motion segment.

Methods: A parametric biphasic finite element model was developed and validated against experimental data under axial compressive loading. Fifteen loading scenarios were analysed, including axial compression, flexion, extension, lateral bending, torsion, and combined loads. Axial loads were applied up to 800N and moment loads up to 2Nm. Multiple analyses were conducted with and without the ribcage to assess its impact on thoracic spinal stability. Vertebral bulge (VB) and load induced canal narrowing (LICN) were utilised as main outcome parameters to assess burst fracture risk.

Results: For single loads, pure 800N axial loading yielded the highest level of VB (0.48mm) and LICN (0.26mm). The smallest increases in VB were measured in 1Nm pure flexion (0.018mm). Combined loading scenarios also demonstrated that axial loading is the principal factor contributing to VB, as changes in VB for combined loads were no greater than 4.35% of VB under axial loading alone. Inclusion of the ribcage was found to reduce the potential for burst fracture by 27% under axial load.

Conclusions: Axial loading is the predominant load type leading to increased risk of burst fracture initiation. Rotational loading (bending, flexion and extension) led to only moderate increases in risk. The ribcage provides substantial stability to reduce overall risk of burst fracture. These findings are important in developing a more comprehensive understanding of burst fracture mechanics in the metastatic spine and in directing future modeling efforts. The results in this study may also be useful in advising less harmful activities for patients affected by lytic spinal metastases.

Funding : Other Education Grant

Funding Parties : Natural Sciences and Engineering Research Council

To analyze the dynamics of the thoracic spine during deep breathing in AIS patients and in healthy matched controls. Case-control cross-sectional study. 20 AIS patients (18 girls, Cobb angle, 54.7±7.9°; Risser 1.35±1.2) and 15 healthy volunteers (11 girls) matched in age (12.5 versus 15.8 yr. mean age) were included. In AIS curves, the apex was located in T8 (14) and T9 (6). Conventional sagittal radiographs of the whole spine were performed at maximal inspiration and expiration. The ROM of each spinal thoracic functional segment (T1-T7, T7-T10, T10-T12), the global T1–T12 ROM were measured. Respiratory function was assess by forced vital capacity (FVC), expiratory volume (FEV1), FEV1/FVC, inspiratory vital capacity (IVC) and peak expiratory flow (PEF). In healthy subjects, the mean T1–T12 ROM during forced breathing was 16.7±3.8. AIS patients showed a T1-T12 ROM of 1.1±1.5 (p<0.05) indicating a sagittal stiffness of thoracic spine. A wide T7–T10 ROM (15.3±3.0) was found in healthy controls (91.6% of the T1–T12 ROM). AIS patients showed only 0.4±1.4 ROM at T7-T10 (36.4% of the T1–T12 ROM) (p<0.001). There was a significant correlation between T7-T10 ROM and IVC. Lenke 1A AIS patients show a restriction of the thoracic spine motion with an almost complete abolition of T7-T10 ROM, a crucial segment participating in the deep breathing. T7-T10 stiffness could explain the ventilatory limitations found in AIS patients

In healthy subjects, respiratory maximal volumes are highly dependent on the sagittal range of motion of the T7-T10 segment. In AIS, the abolition of T7-T10 dynamics related to the stiffness induced by the apex region in Lenke IA curves could harm ventilation during maximal breathing. The aim of this study was to analyze the dynamics of the thoracic spine during deep breathing in AIS patients and in healthy matched controls. This is a cross-sectional, case-control study. 20 AIS patients (18 girls, Cobb angle, 54.7±7.9°; Risser 1.35±1.2) and 15 healthy volunteers (11 girls) matched in age (12.5 versus 15.8 yr. mean age) were included. In AIS curves, the apex was located at T8 (14) and T9 (6). Conventional sagittal radiographs of the whole spine were performed at maximal inspiration and exhalation. The ROM of each spinal thoracic functional segment (T1-T7, T7-T10, T10-T12) and the global T1-T12 ROM were measured. In healthy subjects, the mean T1-T12 ROM during forced breathing was 16.7±3.8. AIS patients showed a T1-T12 ROM of 1.1±1.5 (p<0.05), indicating a sagittal stiffness of the thoracic spine. A wide T7-T10 ROM (15.3±3.0) was found in healthy controls (91.6% of the T1–T12 ROM). AIS patients showed only 0.4±1.4 ROM at T7-T10 (36.4% of the T1-T12 ROM) (p<0.001). There was a significant positive correlation between the magnitude of T7-T10 kyphosis in maximal exhalation and both FVC (% of predicted FVC) and FEV1. In conclusion, Lenke 1A AIS patients show a restriction of the thoracic spine motion with an almost complete abolition of T7-T10 ROM, a crucial segment for deep breathing. T7-T10 stiffness could explain the ventilatory limitations found in AIS patients

Introduction. Adolescent Idiopathic Scoliosis (AIS) is a three-dimensional deformity of the spine with unclear etiology. Due to the asymmetry of lateral curves, there are differences in the muscle activation between the convex and concave sides. This study utilized a comprehensive thoracic spine and ribcage musculoskeletal model to improve the biomechanical understanding of the development of AIS deformity and approach an explanation of the condition. Methods. In this study, we implemented a motion capture model using a generic rigid-body thoracic spine and ribcage model, which is kinematically determinate and controlled by spine posture obtained, for instance, from radiographs. This model is publicly accessible via a GitHub repository. We simulated gait and standing models of two AIS (averaging 15 years old, both with left lumbar curve and right thoracic curve averaging 25 degrees) and one control subject. The marker set included extra markers on the sternum and the thoracic and lumbar spine. The study was approved by the regional Research Ethics Committee (Journal number: H17034237). Results. We investigated the difference between the muscle activation on the right and left sides including erector spinae (ES), psoas major (PS), and multifidus (MF). Results of the AIS simulations indicated that, on average throughout the gait cycle, the right ES, left PS and left MF had 46%, 44%, and 23% higher activities compared to the other side, respectively. In standing, the ratios were 28%, 40%, and 19%, respectively. However, for the control subject, the differences were under 7%, except ES throughout the gait, which was 17%. Conclusion. The musculoskeletal model revealed distinct differences in force patterns of the right and left sides of the spine, indicating an instability phenomenon, where larger curves lead to higher muscle activations for stabilization. Acknowledgement. The project is funded by the European Union's Horizon 2020 program through Marie Skłodowska-Curie grant No. [764644]