Clinical and radiological evaluation of cervical disc arthroplasty with 5-year follow-up: a prospective study of 384 patients.

BACKGROUND: Cervical total disc replacement was developed to avoid known complications of cervical fusion. The purpose of this paper was to provide 5-year follow-up results of an ongoing prospective study after implantation of cervical disc prosthesis. METHODS: Three hundred and eighty-four patients were treated using Mobi-C cervical disc (Zimmer Biomet, Troyes, France) and included in a prospective multicentre study. Routine clinical and radiological examinations were reported preoperatively and postoperatively with up to 5-year follow-up. Complications and revision surgeries were also explored. RESULTS: Results at 5 years showed significant improvement in all clinical outcomes (NDI, VAS for arm and neck pain, SF-36 PCS and MCS). Motion at index level increased significantly from 6.0° preoperatively to 8.0°, and 72.1% of the implanted segments were still mobile (referring to threshold of ROM > 3°). Proximal and distal adjacent discs showed no significant change in average motion 5 years after surgery compared to baseline. Ossification resulting in complete fusion was observed in 16.4% of the implanted segments. Distal and proximal adjacent disc degeneration occurred in 42.2% and 39.1% of patients, respectively. Complications rate was 8.9%, and 1.5% of the patients had reoperation at the index level. Surgery rate of adjacent discs was 2.9%. An increased percentage of working patients and a decrease in medication consumption were observed. At 5 years, 93.3% patients were satisfied regarding the overall outcome. CONCLUSIONS: In this study, favourable 5-year follow-up clinical and radiological outcomes were observed with a low rate of adjacent level surgery. These slides can be retrieved under Electronic Supplementary Material.

Chondroblastoma of the thoracic spine: a rare location. Case report with radiologic-pathologic correlation.

Chondroblastoma is a rare benign cartilage neoplasm that arises from the appendicular skeleton in the vast majority of the cases (80%). Chondroblastoma of the spine is an even more rare condition (30 cases reported), and vertebral chondroblastomas, unlike chondroblastomas of the extremities, present with the appearance of an aggressive tumor on CT and MR imaging and occur at least a decade later. Even though vertebral chondroblastomas are very uncommon tumors, they should nonetheless be included in the differential diagnosis when encountered with an aggressive vertebral mass, and a histological confirmation should be performed. We present a case of chondroblastoma of the thoracic spine of a 27-year-old female for which detailed radiologic-pathologic correlation was obtained.

Comparison between single- and multi-level patients: clinical and radiological outcomes 2 years after cervical disc replacement.

In cervical multi-level degenerative pathology, considering the morbidity of the extensive fusion techniques, some authors advocate for the multilevel disc replacement. This study compared the safety and efficacy of disc replacement with an unconstrained prosthesis in multi- versus single-level patients. A total of 231 patients with cervical degenerative disc disease (DDD) who were treated with cervical disc replacement and completed their 24 months follow-up were analyzed prospectively: 175 were treated at one level, 56 at 2 levels or more. Comparison between both groups was based on usual clinical and radiological outcomes [Neck Disability Index (NDI), Visual Analog Scale (VAS), Range of Motion, satisfaction]. Safety assessments, including complication and subsequent surgeries, were also documented and compared. Mean NDI and VAS scores for neck and arm pain were improved in both groups similarly. Improvement of mobility at treated segments was also similar. Nevertheless, in the multi-level group, analgesic use was significantly higher and occurrence of Heterotopic Ossification significantly lower than in the single-level group. Subject satisfaction was nearly equal, as 94.2% of single-level group patients would undergo the surgery again versus 94.5% in the multi-level group. The overall success rate did not differ significantly. Multi-level DDD is a challenging indication in the cervical spine. This study showed no major significant clinical difference between the two groups. We need further studies to know more about the impact of multi-level arthroplasty, especially on the adjacent segments, but these results demonstrate initial safety and effectiveness in this patient sample.

[Dynamic instrumentation of the lumbar spine. Clinical and biomechanical analysis of success factors]. / Dynamische Versorgung der Lendenwirbelsäule : Klinische und biomechanische Analyse der Erfolgsfaktoren.

Total disc replacement and posterior dynamic stabilization represent alternatives to lumbar spinal fusion which should reduce the risk of adjacent segment degeneration. Disc replacement is indicated for pure discopathy without facet joint degeneration. Spinopelvic balance influences the implant's biomechanics. Therefore pelvic incidence, sacral slope, segmental lordosis and the mean axis of rotation need to be considered. Dynamic stabilization is indicated in moderate discopathy and facet joint degeneration, in degenerative spondylolisthesis grade I with a hypermobile segment and in dynamic lumbar stenosis. The combination of caudal fusion and cranial dynamic stabilization allows a better maintenance of lordosis with multiple level instrumentation and prevents adjacent segment degeneration. If pelvic incidence and sacral slope are high, L5-S1 should be fused because of elevated shear forces.

Intermediate clinical and radiological results of cervical TDR (Mobi-C) with up to 2 years of follow-up.

The interest in cervical total disc replacement (TDR) as an alternative to the so-far gold standard in the surgical treatment of degenerative disc disease (DDD), e.g anterior cervical discectomy and fusion (ACDF), is growing very rapidly. Many authors have established the fact that ACDF may result in progressive degeneration in adjacent segments. On the contrary, but still theoretically, preservation of motion with TDR at the surgically treated level may potentially reduce the occurrence of adjacent-level degeneration (ALD). The authors report the intermediate results of an undergoing multicentre prospective study of TDR with Mobi-C prosthesis. The aim of the study was to assess the safety and efficacy of the device in the treatment of DDD and secondary to evaluate the radiological status of adjacent levels and the occurrence of ossifications, at 2-year follow-up (FU). 76 patients have performed their 2-year FU visit and have been analyzed clinically and radiologically. Clinical outcomes (NDI, VAS, SF-36) and ROM measurements were analyzed pre-operatively and at the different post-operative time-points. Complications and re-operations were also assessed. Occurrences of heterotopic ossifications (HOs) and of adjacent disc degeneration radiographic changes have been analyzed from 2-year FU X-rays. The mean NDI and VAS scores for arm and neck are reduced significantly at each post-operative time-point compared to pre-operative condition. Motion is preserved over the time at index levels (mean ROM = 9 degrees at 2 years) and 85.5% of the segments are mobile at 2 years. HOs are responsible for the fusion of 6/76 levels at 2 years. However, presence of HO does not alter the clinical outcomes. The occurrence rate of radiological signs of ALD is very low at 2 years (9.1%). There has been no subsidence, no expulsion and no sub-luxation of the implant. Finally, after 2 years, 91% of the patients assume that they would undergo the procedure again. These intermediate results of TDR with Mobi-C are very encouraging and seem to confirm the efficacy and the safety of the device. Regarding the preservation of the status of the adjacent levels, the results of this unconstrained device are encouraging, but longer FU studies are needed to prove it.

Sagittal alignment correction of the thoracolumbar junction in idiopathic scoliosis by in situ bending technique.

A long thoracolumbar sagittal rectitude is sometimes present in adolescent idiopathic scoliosis. The purpose of this study was to identify typical patterns, by comparing frontal plane deformities and vertebral rotation leading to this rectitude. Surgical thoracolumbar alignment correction by three-dimensional in situ bending of rods was then analyzed. Pre- and postoperative radiographs of 24 patients with scoliosis (36-104 degrees) were reviewed using Spineview software. Frontal curves and levels of sagittal rectitude were determined. Thoracic kyphosis, lumbar lordosis, sacral slope, pelvic incidence, pelvic tilt, T9 and T1 tilt were measured. Vertebral rotation was measured by computed tomography, Perdriolle's, Nash and Moe's methods. The intervertebral mobility of the rectitude was analyzed on side bending radiographs. Three patterns leading to sagittal rectitude were identified: 11 main thoracic curves (Lenke 1, King 3) with cranial prolongation of the physiological thoracolumbar junction (T7T12) and maximal vertebral rotation above this zone, 13 double major or thoracolumbar curves (Lenke 3 or 5, King 1 or 2) with cranial and caudal prolongation (T9L3) and maximal rotation above and below, 1 lumbar curve (Lenke 5) with caudal rectitude (T12L4) and maximal rotation at L1. There was no relationship between intervertebral mobility and rectitude. Postoperatively, this zone of rectitude disappeared in 17 out of 24 patients after anterior release followed by posterior instrumentation using the in situ bending technique. In situ bending realizes a stepwise correction of the three-dimensional deformity at different levels. An accurate preoperative analysis is mandatory to achieve an adequate sagittal balance, frontal curve correction and vertebral derotation simultaneously. The determined patterns of thoracolumbar rectitude are helpful to plan surgical correction accurately.

Cervical sagittal alignment in adult hyperkyphosis treated by posterior instrumentation and in situ bending.

BACKGROUND: In the normal adult spine, a link between thoracolumbar and cervical sagittal alignment exists, suggesting adaptive cervical positional changes allowing horizontal gaze. In patients with thoracic hyperkyphosis, cervical adaptation to sagittal global alignment might be different from healthy individuals. However, this relationship has not clearly been reported in hyperkyphotic deformity. PURPOSE: The purpose of this study was to identify cervical sagittal alignment types observed on radiographs in young adults with thoracic hyperkyphosis. The relationship between cervical and thoracolumbar alignment as well as the effect of posterior instrumentation and adaptive positional changes of the mobile cervical segment were retrospectively analyzed. PATIENTS AND METHODS: Twenty-three patients (32.7 years; 5-year follow-up) were included. Full spine radiographic measurements were: T1 slope, T1-T4 kyphosis, T4-T12 kyphosis, L1-S1 lordosis, pelvic incidence, pelvic tilt, sacral slope, SVA C7, SVA C2, lordosis between C0-C2, C2-C7, C2-C4 and C4-C7. A Bayesian model and Spearman correlation were used. RESULTS: Two alignment types existed: cervical lordosis (group A) and cervical kyphosis (group B). Preoperatively, T4-T12 kyphosis and L1-S1 lordosis were significantly higher in group A: 76.6° versus 59.4° and -72.8° versus -65.8° (probability of>5° difference P (ß>5)>0.95). Pelvic incidence was higher in group A (49.8° versus 44.2°) and C0-C2 lordosis in group B (-29.4° versus -21.6°). A significant correlation existed between: T4-T12 kyphosis and C2-C7 lordosis, L1-S1 lordosis and pelvic incidence, C2-C7 lordosis and T1 slope, C2-C7 lordosis and T1-T4 kyphosis. Postoperatively, T4-T12 kyphosis decreased by 33.1° P (ß>5)=0.9995), L1-S1 lordosis decreased by 17.7° (P (ß>5)=0.961), T1-T4 kyphosis increased by 14.1° (P (ß>5)=0.973). SVA C2 (translation) increased by 13.8mm. C0-C2 lordosis (head rotation) remained unchanged. Six patients changed cervical alignment. PJK occurred in 15 patients, unrelated to cervical alignment or proximal instrumentation level. DISCUSSION: Two cervical alignment types, lordotic or kyphotic, were observed thoracic hyperkyphosis patients. This alignment was mainly triggered by the amount of thoracic kyphosis and lumbar lordosis, linked to pelvic incidence. Moreover, the inclination of the C7-T1 junctional area plays a key role in the amount of cervical lordosis. The correction of T4-T12 kyphosis induced compensatory modifications at adjacent segments: T1-T4 kyphosis increase (PJK) and L1-S1 lordosis decrease. Global spino-pelvic alignment and head position did not change in the sagittal plane. The cervical spine tented to keep in its preoperative position in most patients. LEVEL OF EVIDENCE: Level IV.

Comparison between total disc replacement and hybrid construct at two lumbar levels with minimum follow-up of two years.

INTRODUCTION: Lower back pain due to degenerative disc disease is a therapeutic challenge in young patients. Although arthrodesis is currently the gold standard for surgical treatment, improvement in total disc replacement techniques makes it possible to preserve segmental mobility with good results in one-level surgery. Nevertheless, the French National Health Authority does not recommend total disc replacement for multilevel surgery. Thus, hybrid constructs that combine one-level disc replacement with arthrodesis have been developed for multilevel indications. HYPOTHESIS: The outcome of two-level lumbar disc arthroplasty does not differ from hybrid constructs. METHODS: The clinical and radiographic outcomes of disc arthroplasty were compared to hybrid constructs for two-level degenerative disc disease in 72 patients after a continuous follow-up of at least 2 years. The patients were divided into two groups that were similar for the indication and type of implants. RESULTS: There was no statistical difference in pain relief (-3.9 points versus -3.5 points for lumbar VAS) or reduction in ODI (-29.5% versus -27.0%) between TDR and hybrid constructs, respectively. There was no statistical difference in range of motion at the level of arthroplasty (8.4° versus 7.6°) and no kinematic dysfunction was identified. The re-operation rate at two years for persistent lumbar pain was respectively 6.7% for two-level disc arthroplasty and 4.3% for hybrid constructs. The complication rate was 4.8% and 8.7% respectively. DISCUSSION: No difference was found in this comparison of two homogeneous series between two-level disc arthroplasty and hybrid constructs for the treatment of degenerative disc disease after two years of follow-up. Two-level disc arthroplasty may be an alternative for young patients depending on an evaluation of long-term results. LEVEL OF EVIDENCE: Cohort observational study level III.

Percutaneous surgery for thoraco-lumbar fractures in ankylosing spondylitis: Study of 31 patients.

BACKGROUND: The risk of vertebral fracture is increased 4-fold in patients with ankylosing spondylitis (AS). Diagnostic challenges and the vulnerability associated with AS combine to generate high morbidity and mortality rates. The objective of this study was to assess the outcome of percutaneous thoraco-lumbar fracture surgery in patients with AS, in terms of quality of life, fracture healing, and complications. HYPOTHESIS: Percutaneous surgery used to treat thoraco-lumbar fractures in patients with AS reliably provides fracture healing, preserves self-sufficiency, and minimises post-operative complications. METHODS: Two centres included 31 patients with AS who were managed by percutaneous surgery for thoraco-lumbar fractures in 2013-2015. The data were reviewed retrospectively, although admission data were collected prospectively. Clinical outcomes were assessed by comparing the values at baseline and last follow-up of three variables: the Parker score, the visual analogue scale (VAS) pain score, and the EuroQol five dimensions (EQ-5D) quality-of-life score. Computed tomography was performed 1 year after surgery to evaluate bone healing, screw position, and implant loosening. Intra- and post-operative complications were recorded. RESULTS: The 31 patients had a mean age at surgery of 75.1 years, a mean follow-up of 35.6 months, and a minimum follow-up of 12 months. Three patients died during follow-up. Mean hospital stay duration was 6 days. Cemented screw fixation was used in 18 patients. At last follow-up, all patients had recovered their self-sufficiency; the mean Parker score was 7.14, compared to 6.73 at baseline, the mean VAS pain score was 1.8, and the mean EQ-5D score decrease versus baseline was 0.07 (P=0.02). Bone healing was consistently achieved. Loosening of an uncemented pedicle screw was noted in 1 patient. Of the 228 screws implanted, 6 (2.6%) were improperly positioned, including 1 within the spinal canal in a patient free of neurological manifestations. Asymptomatic cement leakage was noted in 2 patients. DISCUSSION: Percutaneous fixation of thoraco-lumbar fractures in patients with AS is a reliable method that produces a high healing rate and allows prompt patient mobilisation with preservation of self-sufficiency. The post-operative complication rate is low. LEVEL OF EVIDENCE: IV, retrospective observational study.

Evolution and complications after surgery for spine deformation in patients with Parkinson's disease.

INTRODUCTION: Surgical treatment of spinal deformity is high risk in patients suffering from Parkinson's disease (PD). Several series have already reported a high rate of complications. However, none of these studies included more than 40 patients and none of the risk factors of complications were described. The aim of this study was to describe the rate and risk factors of revision surgery as well as the clinical outcome at the last visit in a large multicenter study of PD patients operated for spinal deformities. METHODS: A multicenter retrospective study included arthrodesis for spinal deformity in patients with PD. Clinical and surgical data including revision surgeries were collected. Assessment of functional outcomes at last follow-up was classified in 3 grades and spinal balance was assessed on anteroposterior and lateral plain X-rays of the entire spine. RESULTS: Forty-eight patients were included. Median age was 67 years old (range 41-80). Median follow-up was 27 months. The rate of surgical revision was 42%. Eighty per cent of revisions were performed for chronic mechanical complication. Global results were considered to be good in 17 patients (35%), doubtful in 17 patients (35%) and a failure in 14 patients (30%), for the whole series. CONCLUSIONS: The results of surgery for spinal deformities in patients with Parkinson disease vary with a high rate of complications and revisions. Nevertheless, these results should be seen in relation to the natural progression of these spinal deformities once spinal imbalance has developed. The association between preoperative clinical balance and final outcome suggests that early surgery can probably play a role in treatment. LEVEL OF EVIDENCE: Level IV (e.g. case series).

[Pedicle closing-wedge osteotomy for the treatment of fixed sagittal imbalance]. / Ostéotomie de soustraction pédiculaire dans le traitement des déséquilibres antérieurs du rachis: à propos de 34 cas.

PURPOSE OF THE STUDY: The aim of this study was to analyze x-ray results in patients who underwent pedicle subtraction osteotomy for complex deformations (flat back, kyphosis) leading to fixed sagittal imbalance. MATERIAL AND METHODS: Thirty-four patients underwent surgery between 1996 and March 2003 in two centers, the orthopedic surgery unit devoted to spinal surgery and sports traumatology at the Strasbourg University Hospitals and the spinal surgery unit at the Chenove Clinic (Dijon). The series included 20 women and 14 men, mean age 46.5 years (range 14-74 years) treated for: postoperative flat back (n = 19), kyphoscoliosis (n = 6), ankylosing spondylarthritis (n = 5), and malunion (n = 4). After careful planning to achieve the necessary degree of correction, the patient was installed on a Cotrel table with a stable support enabling limited blood loss and facilitated reduction maneuvers via elevation of the lower limbs. The technique started by resection of the posterior arch, the transverse processes, and the pedicles, followed by partial resection of the body with a chisel under fluoroscopic control. The closure was achieved by in situ reduction with compressive rotation. Adjacent discs were then evaluated to search for any opening which could be filled by an anterior graft to complete the stabilization. The osteosynthesis used 2-, 4-, and 6-rod assemblies. The 6-rod assemblies enabled anchoring the fixation above and below before the osteotomy. Two prebent rods completed the assembly at reduction after osteotomy. Weight-bearing started on day 4. A protective corset was worn for three months by 19 patients. The patients resumed their occupational activities on average 6.73 months postoperatively without change in activity for 63%. Overall satisfaction was close to 90% excellent outcome. RESULTS: All clinical results were analyzed with the Profil software of Surgiview. X-ray data were analyzed with Spineview. A self-administered clinical questionnaire was used to evaluate pain, result of the operation, and the impact on the patient's body image. On average, the wedge osteotomy measured 28.9 degrees for correction of lumbar lordosis by 31.5 degrees with a maximum of 65 degrees. The misalignment at C7 was reduced from 51 mm to 2 mm. At the pelvic level, version improved 16 degrees, sacral slope 8 degrees. There were four dura mater breaches which had to be sutured, but with no clinical consequence (one progression to meningocele). Mean intraoperative blood loss was 1400 cc (300-4500cc) for a mean operative time of 260 minutes (165-450 min). There were two early infections at day 15 postop which resolved with antibiotics. Four patients developed resolutive sciatica (n = 2) or cruralgia (n = 2) during the following months. The short-term follow-up revealed eight non-unions (25%) with rupture of osteosynthesis material and loss of correction. The opening in the adjacent discs and the insufficient posterior closure explained this mechanical complication. CONCLUSION: Pedicle subtraction osteotomy is an original operative technique reserved for specialized centers. A well-experienced team is needed to control the risks involved. Sagittal balance should be one of the important goals for modern spinal surgery.

Finite element simulation of spinal deformities correction by in situ contouring technique.

Biomechanical models have been proposed in order to simulate the surgical correction of spinal deformities. With these models, different surgical correction techniques have been examined: distraction and rod rotation. The purpose of this study was to simulate another surgical correction technique: the in situ contouring technique. In this way, a comprehensive three-dimensional Finite Element (FE) model with patient-specific geometry and patient-specific mechanical properties was used. The simulation of the surgery took into account elasto-plastic behavior of the rod and multiple moments loading and unloading representing the surgical maneuvers. The simulations of two clinical cases of hyperkyphosis and scoliosis were coherent with the surgeon's experience. Moreover, the results of simulation were compared to post-operative 3D measurements. The mean differences were under 5 degrees for vertebral rotations and 5 mm for spinal lines. These simulations open the way for future predictive tools for surgical planning.

Management of thoracolumbar spine fractures with neurologic disorder.

Thoracic and lumbar fractures represent approximately 50% of neurologic spinal trauma. They lead to paraplegia or cauda equina syndrome depending on the level injured. In the acute phase, the extension of spinal cord lesions should be limited by immediately treating secondary systemic injury factors. Quick recovery of hemodynamic stability, with mean arterial blood pressure>85 mm Hg, appears essential. There is no clinical evidence in favor of high-dose corticosteroid protocols. Their effect on neurologic recovery is unproven, whereas they lead to a higher rate of secondary septic and pulmonary complications. Incomplete deficits (ASIA B-D) require urgent surgery. There is no consensus with regard to complete paraplegia (ASIA A), but early surgery can enable neurologic recovery in some cases. The principle of surgical treatment is based on spinal cord decompression, instrumentation and fracture reduction. Early stabilization of the spine improves respiratory function and shortens the duration of mechanical ventilation and thus intensive care unit stay. Depending on the severity of associated lesions, early surgery within 48 hours is beneficial in polytrauma patients. Percutaneous instrumentation combined with mini-open posterior decompression stabilizes the spine, limiting approach-related morbidity.

Pullout characteristics of percutaneous pedicle screws with different cement augmentation methods in elderly spines: An in vitro biomechanical study.

BACKGROUND: Vertebroplasty prefilling or fenestrated pedicle screw augmentation can be used to enhance pullout resistance in elderly patients. It is not clear which method offers the most reliable fixation strength if axial pullout and a bending moment is applied. The purpose of this study is to validate a new in vitro model aimed to reproduce a cut out mechanism of lumbar pedicle screws, to compare fixation strength in elderly spines with different cement augmentation techniques and to analyze factors that might influence the failure pattern. MATERIALS AND METHODS: Six human specimens (82-100 years) were instrumented percutaneously at L2, L3 and L4 by non-augmented screws, vertebroplasty augmentation and fenestrated screws. Cement distribution (2 ml PMMA) was analyzed on CT. Vertebral endplates and the rod were oriented at 45° to the horizontal plane. The vertebral body was held by resin in a cylinder, linked to an unconstrained pivot, on which traction (10 N/s) was applied until rupture. Load-displacement curves were compared to simultaneous video recordings. RESULTS: Median pullout forces were 488.5 N (195-500) for non-augmented screws, 643.5 N (270-1050) for vertebroplasty augmentation and 943.5 N (750-1084) for fenestrated screws. Cement augmentation through fenestrated screws led to significantly higher rupture forces compared to non-augmented screws (P=0.0039). The pullout force after vertebroplasty was variable and linked to cement distribution. A cement bolus around the distal screw tip led to pullout forces similar to non-augmented screws. A proximal cement bolus, as it was observed in fenestrated screws, led to higher pullout resistance. This cement distribution led to vertebral body fractures prior to screw pullout. CONCLUSION: The experimental setup tended to reproduce a pullout mechanism observed on radiographs, combining axial pullout and a bending moment. Cement augmentation with fenestrated screws increased pullout resistance significantly, whereas the fixation strength with the vertebroplasty prefilling method was linked to the cement distribution.

Percutaneous laser photocoagulation of spinal osteoid osteomas under CT guidance.

BACKGROUND AND PURPOSE: Spinal osteoid osteomas are rare; when they occur, they are usually treated by surgical or percutaneous excision. The aim of percutaneous interstitial laser photocoagulation (ILP) of osteoid osteomas under CT guidance is thermal destruction of the nidus using low-power laser energy, thus precluding bone resection and open surgery. METHODS: Three cases of spinal osteoid osteomas were treated with percutaneous ILP of the nidus. Under CT guidance, the needle was positioned in the center of the nidus, at least 8 mm from neurologic structures. Using a high-power semiconductor diode laser (805 nm) with a 400-microm optical fiber, we delivered 600 to 800 joules to the nidus, depending on its size. The procedure was performed with the patient under neuroleptanalgesia and required overnight hospitalization. RESULTS: Complete pain relief was obtained in all three patients within 24 hours of the procedure, and no major complications were incurred. Follow-up ranged from 20 months to 60 months. CONCLUSION: Percutaneous ILP of spinal osteoid osteoma is a promising, simple, precise, and minimally invasive technique and may be an alternative to traditional surgical and percutaneous ablations.

Explicit calibration method and specific device designed for stereoradiography.

The three-dimensional geometry of the human spine is noteworthy information that can be obtained by stereoradiographic methods. These methods are based on the identification of anatomical structures in several views which are obtained by rotation of a patient standing on a turntable. Calibration algorithms for computer vision or photogrammetry are well documented, but they generally yield calibration devices which are cumbersome for the use in clinical stereoradiography. This paper presents a calibration method adapted to a two-view stereoradiography calibration (frontal and lateral incidences) and based on a simplified geometric modeling of the radiological environment. The a priori knowledge yields four calibration equations related to the vertical and horizontal planes of both views, leading to a specific calibration procedure and device. Moreover this device is attached to the stereoradiographic system (directly integrated on the turntable) in order to facilitate clinical applications. A validation was performed on 26 dried lumbar vertebrae in order to evaluate clinical situation. The mean accuracy of the stereoradiographic reconstruction was 1.2mm.

Epithelioid sarcoma of the spine: a case report.

STUDY DESIGN: This case report illustrates a patient presenting with sciatica and diagnosed with epithelioid sarcoma involving the spine. OBJECTIVES: The treatment of this patient involved multiple mass resections and decompressions of the spinal canal. Radio- and chemotherapy were applied once a clear diagnosis was obtained. SUMMARY OF BACKGROUND DATA: Epithelioid sarcoma is a rare tumor mainly arising in the extremities. Confusion with a benign inflammatory process are possible. Treatment after histologic diagnosis involves wide resection. To our knowledge, this report represents the first case of epithelioid sarcoma involving the spine. METHODS: After initial discectomy, recurrent scarring and mass formation required multiple decompression procedures and fusion. The initial pathology revealed inflammatory reaction on fibrosis. In a later procedure, the histologic diagnosis of epithelioid sarcoma was made. Radiotherapy and chemotherapy were begun immediately. RESULTS: Despite aggressive resections, radiotherapy, and chemotherapy, the patient died 3 months after the last surgical procedure. CONCLUSION: Spinal epithelioid sarcoma can be mistaken for a benign inflammatory process. After a histologic diagnosis, aggressive wide resection is necessary. Multiple recurrences are documented with this tumor in other sites. Prognosis in trunk involvement is less favorable than involvement of the extremities. The role of adjuvant radio- and chemotherapy is unclear for spinal involvement.

Validation of the relative 3D orientation of vertebrae reconstructed by bi-planar radiography.

The three dimensional (3D) reconstruction of the spine can be obtained by stereoradiographic techniques. To be safely used on a routine clinics basis, stereoradiography must provide both accurate vertebral shape and coherent position. Although the accuracy of the reconstructed morphology of the vertebrae is well documented, only few authors studied the accuracy of the vertebral orientation. Therefore, this paper focuses on the evaluation of the orientation accuracy of the reconstructed vertebrae (obtained by non-stereo corresponding point technique) considering either a 178 point vertebral model or a 6 point vertebral model (previously proposed in the literature). Five dried vertebrae were fixed on holders containing four markers each. The 3D reconstruction of both vertebrae and markers were obtained by stereoradiographic techniques. Using least square method matching from one position to another, the relative orientation was computed for the vertebral models (6 or 178 points) and the four markers. These vertebral and holder orientations were compared (considering the holder's one as reference). The repeatability of these relative orientations (vertebrae and holders) was also evaluated. The mean (RMS) orientation error of 178 point vertebral model was 0.6 degrees (0.8 degrees ), for lateral rotation, 0.7 degrees (1.0 degrees ) for sagittal rotation and 1.4 degrees (1.9 degrees ) for axial rotation. The intra-observer repeatability was 0.5 degrees (0.7 degrees ) for lateral rotation, 0.7 degrees (0.8 degrees ) for sagittal rotation and 0.9 degrees (1.2 degrees ) for axial rotation. The orientation was found more accurate and precise when using the 178 point vertebral model than when using the basic 6 point vertebral model. The relative orientation (in post-operative follow-up with respect to the pre-operative examination) of the vertebrae of one scoliotic patient was performed as an example of clinical application. The stereoradiographic method is a reliable 3D quantitative tool to assess the spine deformity, that can be used in clinics for the follow-up of scoliotic patients.