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Synthesis of the 14th ArgoSpine Symposium

P. Kehr, A. Graftiaux

See the communication of :
Alain Graftiaux
Pierre Kehr

The 14th ArgoSpine International Symposium was held in a new venue, the Paris Marriott Rive Gauche Hotel, on January 28th and 29th, 2010. This fourteenth edition was a real success since in addition to regular attendees we were joined by 50 newcomers from all around the world. Once again, we would like to extend our warmest thanks to the fantastic Colloquium team, and especially to Alexandra Devillers.

Thursday 28 January 2010

Cages/Design/Evolutions/Complications — Moderated by C. Mazel (France) and L. Balabaud (France)

See the communication of :
C. Mazel
D. Kaech
B. Poffyn
D. Kaech
E. Vitzthum
K. Hasegawa

To give credit where credit is due, it was the Symposium President who opened the first session. Denis Kaech presented a historical overview of Lumbar and Cervical Cages as well as a brief description of all the aspects of this issue with a large number of illustrations. The second paper dedicated to Threaded Fusion Cages was delivered by Kazuhiro Hasegawa, who will, incidentally, serve as 2011 Symposium President. First, he focused on the chronology: with the development of the ALIF in 1970, PLIF in 1977 and posterior fusion with bone graft in 1983. When they first appear, Dr Hasegawa stated that fusion was achieved in 90% but some patients developed collapse. In 1993, however, cages were created to help prevent collapse of bone graft. Kazuhiro Hasegawa emphasized the importance of the distraction and compression principle. They ensure that stiffness and height are increased. According to him, if cages are appropriate for single fusion, it is not the case for multiple fusion levels; moreover, they do not permit to achieve sufficient reduction.
H-E. Vitzthum then addressed the reasons justifying the development of a New Cage for PLIF. Dr Vitzthum introduced a cage with two vertical Titanium fins to avoid rotation. He specified that this device be contraindicated in case of olisthesis.
In his presentation, Bart Poffyn discussed whether Stand-Alone Cages were sufficient for ALIF. Dr Poffyn’s presentation stated that plating provided stability in flexion/extension, lateral bending and rotation. The reported fusion rate for ALIF alone is 55% while fusion rate is enhanced with screw fixation (88%). The author did not note any relation between recurrence and fusion. In conclusion, from the biomechanical viewpoint, anterior plate is similar to posterior spine fusion following ALIF.

See the communication of :
S. Sano

Evaluation of instability/Motion preservation/Dynamic implants — Moderated by D. Kaech (Switzerland) and R. Schönmayr (Germany)

See the communication of :
K. Hasegawa

Then, after an interactive case discussion, the second presentation by Dr Hasegawa assessed the reliability of our tools by introducing a measurement system for instability. It was first tested on porcine spine then on human cadavers. Thanks to this system, we can measure stiffness in flexion and assess the neutral zone at each studied level. K. Hasagawa’s conclusion was that, in case of spondylolisthesis, a neutral zone value higher than 2 mm confirmed instability.

Interspinous devices and their future in the treatment of spinal disease

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G. Guizzardi
J. Sénégas
T. Fuji

The following topic explored in this session was the Classification and Biomechanics of Interspinous and Intralaminar Implants presented by Giancarlo Guizzardi. He explained that stabilization achieved with interspinous devices was satisfactory in extension but insufficient in other movements. As for the benefit derived from intralaminar devices in the intraspinal treatment, biomechanical results showed that they preserved motion and restored lordosis. The recommended indications are low-back pain, foraminal stenosis and prevention of disc collapse. Dr Guizzardi ended his presentation on the categories included in the classification itself: unconstrained spacers permitting an expansion; constrained devices aiming at posterior stabilisation and finally, semi-constrained implants.

Dr Matgé subsequently described a very valuable interspinous stabilisation system with a non-aggressive surgical technique. The indications are: degenerative disease, disc herniation with disstability, stenoses as well as junction disease.
The device has to be positioned deeply after resecting the inferior part of the upper spinous process and may be combined with microsurgical decompression. Dr Matgé reported a 91% patient satisfaction rate with this technique.

The next presentation by Jacques Sénégas focused on the History of the Development and Future of the Wallis Interspinous Device. This implant was created with the aim of removing, repairing, replacing and regenerating the mobile segment. Painful symptoms can therefore be relieved and adverse mechanical conditions improved without increasing the stiffness of the ligament. The Wallis also provides for restoration of normal range of motion, posterior transfer of the axis of rotation, reduction of disc pressure (regeneration of connective tissue) while ensuring adjacent level preservation. The procedure is very quick and is not associated with high operative risk. Survival rate after 14 years is 81%. Good results have been found in the following indications: stabilization to prevent low-back pain; prevention of hinge phenomenon in foraminal decompression and in case of instability above a fusion. T. Fuji
Then, it was the turn of Dr Fuji to introduce the Alligator Clamp: a simple, non-invasive interspinous fixation with latero-spinal plates soundly connected. This technique can be combined with PLIF cages, which were biomechanically tested by the author on calve lumbar spines. This allows to achieve excellent stabilisation with a 94,5 % fusion rate in the cases with accessible data and 5,4 % that could not be assessed, excluding non-unions.

The take-home message of the ensuing discussion between panellists and audience could be described as the 3 Rs: Recurrent pain in Retroflexion and Retrolisthesis seems to be the best indication for interspinous devices.

See the communication of :
C. Villas

Round-Table. Protection of the adjacent level to a fusion - Dynamic implants — Moderated by G. Guizzardi (Italy) and G. Matgé (Luxembourg)

See the communication of :
M. Szpalski
W. Skalli
G. Dubois
G. Perrin

Marek Szpalski opened the round table on Protection of the Adjacent Level after a Fusion with a presentation on the adjacent level degeneration problem itself. He noted that this phenomenon could be asymptomatic. According to the literature, the radiographic incidence is high: 92% on cervical spine X-rays; it is clinically relevant only in 6% of the cases, with a 2% evolution per year. Whereas the incidence is of 43% on lumbar spine X-rays and is of clinical significance in 30%, with an aggravation in 4% of the patients per year. He identified age as the most significant factor.
Prof. Szpalski explained that on MRI, particular attention should be paid to individual characteristics rather than to the type of fusion (genetic factor) and to multilevel degenerative discs that are not adjacent to the fusion. It is worth noting that there was no difference in the outcome achieved either with dynamic, semi-rigid, or rigid devices. Marek Spzalski concluded that the true nature of the degenerative disease (i.e., provoked by surgery or natural evolution) remained undecided.

The second paper of this round-table, presented by Wafa Skalli, dealt with the Biomechanical Behaviour of the Adjacent Level. She explained that degeneration depended of three factors: overstress due to hypermobility, overstress due to excessive loads and overstress due to pre-existing abnormality. Investigations using patients quantitative follow-up and numerical simulation can help understand biomechanical behaviour. Prof. Skalli further explained that there is a significant correlation between solid fusion, balance and good results. She added that studies have shown that a rigid instrumentation with poor balance resulted in higher intervertebral disc stress also at the adjacent level. Pelvic tilt and lordosis are key regulation parameters for each patient with their specific incidence. A dynamic instrumentation leaves the subject with a larger margin to seek for its own balance.
Due to a mechanism of compensation, the bending stiffness of the spine must increase in flexion because it is exposed to excessive loads. The effect of gravity and postural disorders explain why in case of kyphosis, in flexion, 5 cm are sufficient to increase the stress by over-compression of the disc and to result in poor status for the adjacent disc. The preoperative assessment of the soft tissues is important to comprehend the essential role of muscles.

Then, Gilles Dubois took over and reported on his experience with the Dynesis system, which concept is to improve anatomical conditions. This system brings dynamic stabilization and even more importantly improved disc healing through rehydration. The clinical results reported in the literature have shown that Adjacent Segment Disease is linked to age and to the type of fusion. It is worth noting that ASD rates (4,4%) remained stable over time.
The last speaker of this round-table was Gilles Perrin, who explored the long-term effect of the intervertebral dynamic stabilization as a protective technique for adjacent levels. His presentation focused on the intervertebral dynamic stabilization with the ISOBAR®. After detailing clinical examples of adjacent segment degeneration in patients treated with short instrumentation, Prof. Perrin explained that two factors were decisive in the onset of the disease: failure to restore lordosis and a coexisting disc lesion at the level above. He noted that MRI classification of disc degeneration was useful. One of the main characteristics of ISOBAR and ISOLOCK is to be equipped with a shock absorber creating a semi-rigid transitional intervertebral zone. He finally presented the results of long-term follow-up in two groups: one who underwent fusion with rigid fixation and the other who benefited from semi-rigid dynamic stabilization. There was a larger number of cases of adjacent disc degeneration in Group 1 (rigid fixation) than in Group 2 (semi-rigid fixation).

New concepts in fusion technology — Moderated by M. Mayer (Germany) and M. Szpalski (Belgium)

See the communication of :
R. Schönmayr

After an interactive discussion, in the following paper, R. Schönmayr introduced a new technique in lumbo-sacral fusion with a number of possible approaches: the AxiaLIF. Prof. Schönmayr emphasized that with an axial approach, spinal canal and abdominal cavity were untouched. He added that this approach concerned only L5S1 via the presacral space, close to the midline of S1, through S1; then the surgeon had to remove the disc, fill the space with bone and insert a screw with variable pitch. This procedure can be associated with posterior fusion. In conclusion, Robert Schönmayr stated that fusion rate was high with this technique; there were very few complications although rectoscopy was an essential final step.

Tumours

See the communication of :
S. Boriani

Then it was the turn of Stefano Boriani to describe Minimally Invasive Posterior Stabilization for Malignancies of the Spine. He first insisted that an accurate diagnosis was a prerequisite for appropriate indications. He subsequently gave an outline of endoscopic removal after embolization combined with stabilization in case notably of a large plasmacytoma, allowing quick recovery and return to normal life. Prof. Boriani added that percutaneous fixation after endoscopic removal could also prove useful in some cases. He noted that in primary tumours, endoscopy was only a step. In his very informative presentation, Stefano Boriani introduced the mini-invasive techniques for removal of tumours with minimal change to the life quality of patients.

See the communication of :
M. Vilendecic

Barriers to disc reherniation

The last speaker of this session was L. Darko who explored the question of the efficacy of a new system such as the Barricaid to prevent recurrent disc herniation. He first noted that in disc surgery two types of surgical approaches were used today: a conservative or an aggressive treatment. He subsequently investigated whether conservation or reconstruction of the anulus gave the best results. The available reconstruction methods involve sutures or the Barricaid anular prosthesis. He presented the results of a study on the results of the treatment with the Barricaid: disc height was maintained and it prevented disc reherniations. He concluded with the additional applications of this system including fusion with bone graft and stabilization of the nucleus implant.

Minimally invasive technology in spine surgery — Moderated by B. Poffyn (Belgium) and H.E. Vitzthum (Germany)

See the communication of :
J.C. Le Huec
J.P. Elsig
M. Szpalski

After the coffee break, Michael Mayer opened the last session of the day by covering the Minimally Invasive Techniques in the Treatment of Lumbar Degenerative Disc Disease. During his presentation, he went through the numerous benefits offered by this type of procedures: reduced blood loss, lesser muscular damage, enhanced visual assessment in the first three days, lower CRP level, shorter operating time, decreased postoperative morbidity, fewer perioperative complications and shorter hospitalization stays.

Jean-Charles Le Huec further elaborated on minimally invasive technology, focusing this time on Percutaneous Screw Fixation. The objective of his paper was to assess if it was a viable technique for the treatment of thoracolumbar fractures and to make a recommendation as to whether a surgeon or a radiologist should perform this technique. Prof. Le Huec first indicated that only one pedicular screw was available on the market (Sextant™ – Medtronic) but there were many surgical techniques. According to him, fluoroscopic or navigation control (O-Arm navigation) is ideal and entry portal selection (obliquely) is crucial. In the Sextant procedure, screw extenders must be aligned before the rod is inserted. In case of fracture reduction, JC Le Huec would recommend to use a retractor in minimal access techniques or alternatively, a screw extender and finger dissection. He explained that according to the literature, 20% of thoracolumbar fractures needed anterior support and percutaneous technique was shown no to allow effective grafting. In case of tumours, percutaneous screw fixation is only the first step of the treatment providing temporary stabilization. He concluded that the problem lay in the indication (to be determined only by a spine surgeon). The surgical practitioner could be a radiologist although the fixation was eventually up to the spine surgeon.

In the next paper, Jean Pierre Elsig explained why he abandoned percutaneous fusion and external fixation. He started by reminding that in the aging spine greater load is placed posteriorly and he explained that the advantages of the MIS percutaneous approach to the lumbar intervertebral space had been learned from percutaneous decompressions. Percutaneous fusion and external fixation was created in Zürich in 1988 with limited approach and view. At the time, Dr Elsig used the external fixator of Magerl (introduced in 1985). The radiological follow up results were as follows: early resorption in 15 % of the cases, non-union in 27 % and subsidence in 30 %. Osteonecrosis and severe instability were also noted and one case presented with stenosis and instability below a fusion after fixation removal. Having commented several other examples of illustrative cases he ended his presentation on the drawbacks of percutaneous fusion that led him to abandon this technique: invasive diagnostic method, heavy procedure for the patient, offering no control of balance with a high non-fusion rate.

After a discussion, the last lecture of the day was delivered by Marek Szpalski on the Indications and Limitations of Interspinous Spacers for Lumbar Stenosis Treatment. From the viewpoint of biomechanics, the diameter of the spinal canal decreases in extension. The classical treatment of lumbar stenosis consists in a wide resection inducing destabilisation. He recommended to perform preferably a conservative decompression allowing to keep the tension band in flexion. The spacer is inserted with a unilateral approach in order to preserve the posterior ligament. The addition of a band reduces the instability in flexion. Prof. Szaplski reported the results of studies showing that stabilisation was obtained in the antero-posterior direction but stated that interspinous spacers were contraindicated in acute instability.

See the communication of :
S. Fokter
diainter

Friday 29 January 2010

Disc arthroplasty and nucleus replacement. Total lumbar disc replacement — Moderated by J.P. Elsig (Switzerland) and P. Heini (Switzerland)

See the communication of :
F. Kandziora
JC. Le Huec
M. Mayer M. Szpalski

The Friday morning session was devoted to Disc Arthroplasty, Nucleus Replacement and Total Lumbar Disc Replacement. The first guest speaker of this session was Michaël Mayer focusing on the present of lumbar total disc replacement. He reported good results in an uncontrolled trial with 10% of reoperations and complications up to 40%. Return to work and sports activities were allowed at 6 months on average. Prof. Mayer noted that no recent study results were available. According to the literature, most improvements occur in the first three months and a multilevel implantation is more likely to lead to a poorer outcome than a unilevel. Furthermore, better results are achieved at L4L5 than L5S1 while previous surgery has no influence on the clinical outcomes. On the other hand, the influence of age is unclear. The indications are especially for one level and acceptable for two levels. However, this procedure should be avoided in older patients and those suffering from facet joint osteoarthritis. He showed comparable rates of reoperation with fusion or disc, explaining that these second surgeries were due to technical failures. Lumbar total disc replacement may increase facet osteoarthritis, disc degeneration at the adjacent level with a higher rate at L5S1. Prof. Mayer added that facet joint osteoarthritis led to unsatisfactory outcomes. Among the prognostic factors, he noted a correlation between a higher preoperative morbidity and a poorer outcome. A significant interdependence was also observed between a higher preoperative range of motion as well as disc space height and a satisfactory postoperative segmental mobility. He noted that cases of heterotopic ossification were rare. Finally, in the treatment of low back pain, identical or better outcomes were obtained with disc prosthesis as compared to fusion. Then, it was the turn of Marek Szpalski to address the somewhat provocative question: Are Prosthetic Discs Worth Their High Price? The objective of this paper was to present a critical evaluation of lumbar disc prostheses and determine the future of such implants. Prof. Szpalski first presented to the audience the success achieved with the TDR in preservation of motion and of the adjacent level. He subsequently provided a history of fusion devices since Paul Harmon. The results reported in the literature with Charité are as satisfactory as with the BAK™ cage using non-inferiority margin with a delta of 10 %. He added that most fused patients were not candidates for ADR/TDR and that complications were not rare in TDR. Moreover, revision surgery for a failed disc arthroplasty is a life threatening surgery. On the other hand, the risk for serious complications with TDR revision surgery is high. His conclusion was that the devil is in the details and that an accurate indication depended on an accurate diagnosis.

In a second presentation, Jean-Charles Le Huec discussed the importance of Spinal Balance in Total Lumbar Disc Replacement. In introduction, he explained that the pelvis is the basement of the spine. The sacral slope and pelvic angle are variable but the pelvic incidence is constant. On images of the biomechanical analysis of the spine with a software, lumbar lordosis is located between the apex and the S1 endplate. Prof. Le Huec presented the results of a prospective study showing that the effect of total disc prosthesis is a decreased lordosis at the adjacent level and increased lordosis at the level of the prosthesis. The take-home message is that TDR at L4L5 level seems to be the best indication while TDR or fusion at L5S1 level show equivalent results. In case of two levels, a hybrid construct with fusion at level below and prosthesis at the upper level is the best option.

See the communication of :
J. Schroeder

Total cervical disc replacement and alternatives — Moderated by D. Kaech (Switzerland) and G. Perrin (France)

See the communication of :
G. Matgé
M. Mayer
Robert Schönmayr

After two interactive case discussions, Michaël Mayer centred his presentation on the Rationale and Indications for Cervical Disc Prosthesis. He first detailed the range of prostheses available and their different biomechanical properties. Prof. Mayer emphasized that overall results were satisfactory and that the cervical disc prosthesis was the gold standard for disc herniations and bone compression. On the other hand, he noted that in the cervical spine results of fusions were excellent. Among the arguments in favour of artificial disc replacement, he mentioned the low complication rate (6,8 % with the Bryan prosthesis), while according to him, the necessity to protect adjacent segments was questionable. The usual contraindications include osteoporosis and myelopathy. Heterotopic ossifications (HO) are also a concern. Only 33.8 % of the cases did not develop HO. Hence, Prof. Mayer advocated the administration of postoperative NSAID to prevent their onset. He noted that wear did not seem to play a significant role and postoperative rehabilitation time was shorter than in fusion.

In his comparison of 4 types of cervical disc prosthesis, Robert Schönmayr detailed the characteristics of the: 1). Bryan™: requires elaborate instruments and extensive milling of endplate; it is filled with water. Among the possible sources of error are the kyphotic position of the prosthesis, the risk of heterotopic ossification and late fusion (in 15% of the cases reported). 2). Prodisc-C™: the bone canal has to be chiselled into the endplates. One significant source of error lies in posterior migration after removal of the osteophytes. 3). PCM® (2nd generation): specific shaping of the anterior groove. Anterior migration of the superior endplate and an oversized prosthesis are the main possible sources of error. 4). With the M6™ no migrations were observed. In conclusion, Prof. Schönmayr did not report any difference in clinical results for these four types of implants.

The next presentation by Guy Matgé dealt with dynamic cervical implants. He summarized the DCI philosophy as dynamic cervical stabilisation. In published retrospective studies, the estimate of the incidence of adjacent degeneration in fusion is 2,9 %. Unlike most cervical prostheses requiring techniques that may cause damage to the bone and involve bleeding, during the surgery, Dr Matgé insisted that care must be taken not to remove the cartilage and added that there is no need to resect anterior osteophytes. The usual complications observed with the cervical disc prostheses are notably heterotopic ossification and kyphosis. After presenting several examples of U-shaped DCI, he explained that indications were large and ranged from disc herniation and stenosis to adjacent fusion. This type of implant is however contraindicated in case of tumours or vertebral fractures. The results of biomechanical tests found the DCI to reproduce physiological flexion and extension. Moreover, no evidence of subsidence was detected. Dr Matgé ended his paper with a description of the insertion tools.

After a controversial round-table on fusion versus arthroplasty, moderated by J.P. Elsig (Switzerland) and P. Heini (Switzerland), the paper Surgical Outcome of Posterior Approach in Patients with Thoracic Myelopathy due to Disc Herniation that won the Showa Ika award was presented by Taketoshi Kushida, followed by the ArgoSpine Thesis Award bestowed to Roel Hoogendorn for his work on the Degeneration and Regeneration of the Intervertebral Disc.

See the communication of :
M. Ronai
M. Mayer
C. Villas
K. Hasegawa
T. Kushida
R.J. W Hoogendoorn

Nucleus Replacement — Moderated by J.C. Le Huec (France) and J.P. Steib (France)

See the communication of :
Robert Schönmayr

The first guest speaker of the afternoon was Robert Schönmayr who explored the past, Present and Future of Nucleus Replacement. He explained that the concept was to stop the evolution of Degenerative Disc Disease early by restoring nucleus size thus preserving disc height and facet joints. It is worth noting that the hydrogel devices allow viscoelastic motion. The complications (30%) include damage to nerve, roots, facet or endplate, migration or are related to the fusion. The polymer-based implants use either an inflated balloon or silicone for nucleus replacement. There is also a range of mechanical devices. Satisfying results are obtained with all these implants provided that there are no complications. Therefore, Prof. Schönmayr supports the concept of nucleus replacement as a viable surgical option in degenerative disc disease, although indications are difficult to define and the restoration of disc height is still a concern. The future belongs to the least invasive techniques.

See the communication of :
P. Papagelopoulos
R. Delfini

UltraCision technology in a posterior spinal approach

See the communication of :
C. Mazel

Christian Mazel then shared with us his experience of the use of UltraCision technology in the posterior spinal approach. He introduced the Harmonic UltraCision, which like a traditional electrocutter, permits coagulation and cutting. This device can achieve an ultrasonic speed of 55500 cycles per second and four qualities of action: coagulation, cutting, cavitation and coaptation. The formation of vapour bubbles leads to the dessication of the tissues without bleeding. The difference between electrocautery and UltraCision is that here the patient is not exposed to electricity. Moreover, the temperature is 150° vs. 400° when using electrocautery. Another advantage of UltraCision is decreased bleeding in posterior spine surgery. Prof. Mazel reported on the results of a study conducted in 36 patients who underwent surgery with the Harmonic scalpel in 17 of the cases vs. 19 with electrocautery: although blood loss is difficult to evaluate, a statistical decrease of postoperative pain was shown in the Harmonic series while a learning curve is necessary with electrocautery. No other significant differences were found.

Vertebral body stenting and percutaneous approaches

See the communication of :
A. Gangi

Paul Heini presented a comparison of Vertebroplasty versus Kyphoplasty in the Treatment of Vertebral Fractures. Vertebroplasty (vertebral augmentation) is commonly performed but according to a published randomized trial, infiltration is shown to provide pain improvement in 50% of the cases. Vertebral augmentation is indicated for pain relief and to limit progressive collapse. The reported pain outcomes are similar with either vertebroplasty or kyphoplasty. Dr Paul Heini emphasized that viscosity was the key to prevent leakage. None of these two techniques can restore vertebral height or correct kyphotic deformity. In this respect, patient’s good posture is more effective than surgery using a balloon. However, Vertebral Body Stenting combined with cement proves useful for height restoration in fresh fractures.

The following discussant was Prof. Gangi who elaborated on the Percutaneous Treatment of Vertebral Body Tumours. He described two options in tumour management: single tumour with complete ablation or tumour reduction. According to him, quality imaging is the key to see the whole vertebral body in all planes. The introduction of cement is performed using image-guidance. The MRI has the double advantage of low radiation exposure with a good view of the tissues. An anaesthetist is present. A. Gangi detailed several techniques: thermal ablation, RadioFrequency ablation, argon-based cryoablation, which is performed in thirty minutes as well as a thermocouple to control the temperature around the tumour. All these techniques require knowledge of anatomy and technique, experience, equipment and interdisciplinarity.

Navigation in spine surgery — Moderated by K. Hasegawa (Japan) and G. Matgé (Luxembourg)

See the communication of :
J.C. Le Huec
R. Schönmayr

The final session was dedicated to navigation in spine surgery and Robert Schönmayr explained the reasons why he uses and recommends this tool. According to him, it can prove useful to detect malpositioning – particularly – of transpedicular and transarticular screws in the cervical spine. He insisted on the correct fixation of the target for calibration and on the matching of X-ray with CT-scan images. Prof. Schönmayr described the steps of the robot-assisted procedure for screw placement, adding that accurate positioning was achieved in 98,6%. However, among the drawbacks, he mentioned the learning curve and artefacts. Lastly, Jean-Charles Le Huec addressed the O-arm possibilities and limits. He first explained that some perioperative problems should be solved such as anatomical variability (loss of landmarks in scoliosis) and iatrogenic variations of the anatomy. Furthermore, the incidence of misplaced screws ranges between 14 % and 41 % according to the different published data. When using CT-based navigation, misplacement rate is only of 6,2 % vs. 14 % with fluoroscopic navigation. Prof. Le Huec presented the O-Arm as an intraoperative CT scan. He gave illustrative examples of thoracolumbar scolioses in which 175 screws were placed and none misplaced. The O-arm can be used for mediastinoscopy and in the cervical spine for endoscopic surgery. In revision surgery, it proves useful when landmarks are lost. Moreover, there are no complications related to O-Arm navigation-guided screw fixation. In conclusion, the CT-scan images performed with the O-Arm during the whole surgery are extremely valuable to the surgeon.

The symposium was closed with two interactive case discussions and the vote for the best poster.

See the communication of :
Seyed Rezaian
Giuseppe Bonfiglio
Kazuhiro Hasegawa