Jean-Paul Steib

Surgical correction of scoliosis by in situ contouring: A detorsion analysis

Study Design. A detorsion analysis of the scoliosis surgical correction by means of in situ contouring technique (ISC). Objective. To describe the technique of ISC. To measure the vertebral and intervertebral axial rotation in thoracic and lumbar curves and their correction obtained by ISC. Summary and Background Data. The vertebral and intervertebral axial rotation allows to evaluate the severity of the curves. However, the intervertebral axial rotation is barely studied and the vertebral axial rotation is a controversial point of the surgical correction. Methods. Twenty patients with thoracic and lumbar scoliosis were operated on with ISC. Vertebral axial rotation at the apex and the sum of intervertebral axial rotations all along the curve were computed before and after surgery from the three-dimensional stereoradiographic reconstruction of the spine and the pelvis. All the measurements were made in the standing position. Results. Correction of the axial rotation was obtained at the apex of both thoracic and lumbar curves of idiopathic and degenerative scoliosis. The mean values of correction (in terms of axial rotation) were 8° to 19° (62%–67%). The percentage of correction of the sum of intervertebral axial rotations all along the curve, proposed as a “detorsion index” (preoperative − postoperative/preoperative), was found at 57% to 92%. No significant differences were found for the correction (in terms of axial rotation and detorsion) between idiopathic and degenerative curves. Conclusions. The axial rotation was measured in clinics on standing patients with scoliosis from three-dimensional stereoradiographic reconstruction and demonstrated a reliable detorsion obtained by ISC.

Relevance of the anatomical location of the Adamkiewicz artery in spine surgery

PurposeThe aim of this study was to describe the preoperative topography of the Adamkiewicz artery and the blood supply of the lumbosacral spinal cord in patients who underwent spinal surgery. The relevance for anterior approaches of the thoracolumbar spine was then analyzed.MethodsOne hundred consecutive spinal angiographies were reviewed. Surgical indications were: 26 vertebrectomies, 30 anterior fusions in fractures, 13 malunions, 16 anterior releases in scoliosis, 11 pedicle subtraction osteotomies and 4 thoracic disc hernias. The level and the side of the Adamkiewicz artery and the presence of additional radiculomedullary arteries were determined. Modifications of surgical planning owing to the Adamkiewicz artery were analyzed.ResultsThe Adamkiewicz artery was always located between T8 and L3, at T9 or T10 in 50%, and coming from the left side in 75% of the cases. Additional radiculomedullary arteries were found in 43% of the cases. A concordance between the topography of the Adamkiewicz artery and the planned surgical approach was noted in 15%, which led to ten side changings and three modifications of surgical technique with segmental vessel preservation. An ischemic syndrome of the anterior spinal cord did not occur.ConclusionsSpinal cord ischemia is rarely reported after segmental vessel ligation. Spinal angiography allows determining the topography of the Adamkiewicz artery safely. If the planned surgical approach is located at the same level, a contralateral approach or selective surgical techniques without vessel ligation could avoid possible damage to the Adamkiewicz artery if the pathology does not dictate the side and the extent of the surgical approach.

Bacteriology of degenerated lumbar intervertebral disks.

Study Design: A prospective microbiological analysis of intervertebral disk material in surgically treated patients presenting lumbar disk degeneration. Objective: To determine the prevalence and species of bacteria in degenerated lumbar disks, their eventual role in the pathophysiology, and the possible influence of risk factors. Summary of Background Data: Intervertebral disk degeneration results from biochemical, mechanical, genetic, and toxic factors. The hypothesis of low-grade infection has been raised but not elucidated to date. Methods: Eighty-three patients (34 males, 49 females, 41 y) were treated by lumbar disk replacement at L3–L4, L4–L5, or L5–S1. An intraoperative biopsy and microbiological culture were performed for each disk to determine if intradiskal bacteria were present. Magnetic resonance stages were Pfirrmann IV or V, with Modic I in 32, and Modic II in 25 cases. A preoperative discography was performed in 49 patients, 24 had previous nucleotomy. Results: Bacteria were found in 40 disks, 43 cultures were sterile. The following bacteria were evidenced: Propionibacterium acnes 18, coagulase-negative staphylococci 16, gram-negative bacilli 3, Micrococcus 3, Corynebacterium 3, others 5. Ten biopsies presented 2 different species. Multinucleated cells were evidenced histologically in 33% of positive biopsies. Bacteria were predominantly found in males (P=0.012). The mostly positive level was L4–L5 (P=0.075). There was no significant relationship between bacterial evidence and Modic sign. A preoperative discography or previous nucleotomy did not represent significant contamination sources. None of the patients presented infectious symptoms. Conclusions: Although the hypothesis of biopsy contamination cannot be excluded, intradiskal bacteria might play a role in the pathophysiology of disk degeneration. However, the histologic presence of multinucleated cells may indicate an inflammatory process that could sustain the hypothesis of low-grade spondylodiscitis at 1 stage of the cascade of lumbar disk degeneration. These microbiological and histologic findings would need to be compared with nondegenerated disks. Level of Evidence: Diagnostic level III.

Three-Dimensional Quantitative Segmental Analysis of Scoliosis Corrected by the In Situ Contouring Technique

Study Design. A three-dimensional analysis of right thoracic scoliosis before and after surgical correction was performed. Objective. To compare the orientations of the vertebrae in apical and junctional zones before and after surgery. Summary and Background Data. Three-dimensional segmental analysis considering the lateral, sagittal, and axial (vertebral and intervertebral) rotations that can define apical and junctional zones has been described previously. Modern surgical techniques have been designed to correct scoliosis three-dimensionally. Therefore, the effect of the surgery must be evaluated in three dimensions. Methods. The three-dimensional reconstruction of the spine and pelvis of 10 patients with right thoracic scoliosis was obtained by a stereoradiographic method before and after surgery. The orientations of all vertebrae were computed, and the apical and junctional zones were defined. The correction of these characteristic vertebrae obtained by the in situ contouring technique was evaluated. Results. The mean three-dimensional pattern for the 10 patients was 20° of vertebral axial rotation with 6° of intervertebral extension in the thoracic apex and 30° of vertebral lateral rotation with 10° of intervertebral axial rotation in the junctional zones of the thoracic curve. The correction obtained by in situ contouring was 52% to 79% for all these three-dimensional vertebral orientations. Conclusions. Three-dimensional reconstruction of the spine allows quantitative segmental analysis of the deformity. This could be used as a reliable tool to evaluate both the severity of the scoliosis and the effects of the surgical correction.

In vivo distribution of spinal intervertebral stiffness based on clinical flexibility tests.

Study Design. A numerical study was conducted to identify the intervertebral stiffness of scoliotic spines from spinal flexibility tests. Objective. To study the intervertebral 3-dimensional (3D) stiffness distribution along scoliotic spine. Summary of Background Data. Few methods have been reported in literature to quantify the in vivo 3D intervertebral stiffness of the scoliotic spine. Based on the simulation of flexibility tests, these methods were operator-dependent and could yield to clinically irrelevant stiffnesses. Methods. This study included 30 patients surgically treated for severe idiopathic scoliosis. A previously validated trunk model, with patient-specific geometry, was used to simulate bending tests according to the in vivo displacements of T1 and L5 measured from bending test radiographs. Differences between in vivo and virtual spinal behaviors during bending tests (left and right) were computed in terms of vertebral rotations and translation. An automated method, driven by a priori knowledge, identified intervertebral stiffnesses in order to reproduce the in vivo spinal behavior. Results. Because of the identification of intervertebral stiffnesses, differences between in vivo and virtual spinal displacements were drastically reduced (95% of the differences less than ±3 mm for vertebral translation). Intervertebral stiffness distribution after identification was analyzed. On convex side test, the intervertebral stiffness of the compensatory curves increased in most cases, whereas the major curve became more flexible. Stiffness singularities were found in junctional zones: these specific levels were predominantly flexible, both in torsion and in lateral bending. Conclusion. The identification of in vivo intervertebral stiffness may improve our understanding of scoliotic spine and the relevance of patient-specific methods for surgical planning.

Influence of 2 different dynamic stabilization systems on sagittal spinopelvic alignment.

Study Design A retrospective study. Objective To analyze and compare the sagittal spinopelvic alignment variation after implantation of purely dynamic and hybrid pedicle screw-based stabilization systems, seeking for its clinical implication. Summary of Background Data Numerous studies have investigated the kinematic features of pedicle screw-based dynamic stabilization systems since their clinical application. However, there is a lack of literature concerning their influence on the sagittal spinopelvic alignment, which has been proved to be important in the development of future adjacent segment degeneration (ASD). Methods Lateral standing lumbar radiographs of 29 patients (17 males, 12 females, 27 to 64 y) who were implanted with purely dynamic (Dynesys: group A, n=15) or hybrid (FlexPLUS: group B, n=14) stabilization systems, and with a minimum follow-up of 1 year, have been reviewed. These parameters were measured using Spineview software and were compared within and between groups: L1 to S1 lordosis, lordosis of instrumented segments (ISL), cranial adjacent segment lordosis (CASL) next to the instrumentation, highest instrumented segment lordosis (HISL), pelvic incidence, sacral slope, and pelvic tilt. Results Preoperative lordosis parameters were not significantly different between group A and B. The average L1 to S1 lordosis decreased from 55.3 degrees preoperatively to 52.6 degrees postoperatively in group A (P=0.007) and from 60.2 degrees to 59.3 degrees in group B (P=0.054). There was no significant difference between both groups (P=0.083). The average ISL decreased from 25.9 degrees preoperatively to 21.7 degrees postoperatively (P=0.00002) in group A and from 30.0 degrees to 28.6 degrees in group B (P=0.153). The prepostoperative ISL variation was significantly different between group A and B (P=0.015). The average HISL decreased from 9.5 degrees to 6.2 degrees in group A (P=0.0007) and from 13.1 degrees to 12.4 degrees in group B (P=0.295). The loss of HISL was significantly greater (P=0.010) in group A than in group B. The average CASL increased from 6.9 degrees to 9.2 degrees (P=0.013) in group A. The CASL variation from 10.6 degrees to 10.4 degrees was not significant (P=0.763) in group B. When comparing both groups, the difference of CASL variation was statistically significant (P=0.043). The pelvic incidence, sacral slope, and pelvic tilt did not change significantly before and after instrumentation in both groups. Conclusions On the basis of the result of this study, the hybrid stabilization system could better preserve the lordosis of instrumented segments and subsequently reduce the extent of compensatory lordosis increase at the cranial adjacent segment. This could theoretically prevent the development of an ASD. The long-term outcome and the correlation between lordosis-preserving capacity and ASD need to be further prospectively analyzed.

Intraoperative three dimensional correction during in situ contouring surgery by using a numerical model.

Study Design. A numerical study was conducted by simulating in situ contouring (ISC) surgery. Objective. To quantify intraoperative correction during ISC surgery. Summary of Background Data. Surgical techniques correcting scoliosis, like the ISC one, lead to a complex 3-dimensional correction of the spine. Using motion analysis devices to analyze the effect of intraoperative surgical maneuvers was tedious and limited the study to the kinematics of exposed vertebrae. An alternative method consisted in simulating the surgical gestures. However, proposed models were based on rigid instrumentations, and focused attention on specific gestures of the rod-rotation and the distraction techniques through operator-dependent simulations. Methods. This study included 10 patients with severe idiopathic scoliosis treated by ISC surgery. From a patient-specific finite-element model (T1–L5 and pelvis), all main steps of the ISC surgery were automatically simulated. A specific algorithm was developed to determine the sequences of bending maneuvers according to the rod shapes chosen by the surgeon. The accuracy of the automated surgery simulation was assessed regarding the virtual postoperative spinal configuration and postoperative clinical data. For each maneuver, vertebral kinematics was computed as well as the evolution of various clinical parameters. Results. The bending maneuvers of both the first and the second rods provided complementary effects inside, but also outside the fused spinal area. These main maneuvers combined the intraoperative spinal corrections induced by maneuvers specific to the rod-rotation surgery. Conclusion. The automated patient-specific simulation of ISC surgery may improve the understanding of the main mechanisms involved in the scoliosis surgical correction.

In situ contouring technique in the treatment of thoracolumbar fractures.

Burst fractures typically occur at T12 or L1 and create a sagittal deformity by a compression mechanism. This posttraumatic kyphosis is evaluated preoperatively by measuring the sagittal index of Farcy. Posterior instrumentation using in situ contouring is based on a bilateral insertion of rods which take the shape of the spine first. The rods are placed in a perpendicular position to monoaxial pedicular screws and then bent in situ, which makes the spine follow the movements of the rods. This principle makes it possible to correct the posttraumatic kyphosis at the level of the fractured vertebra and the overlying disk, which will open progressively using a ligamentotaxis mechanism. An additional anterior approach is indicated if the sagittal correction through the disk represents less than 50% compared to the total correction (in otherwords, if the correction of the traumatic deformity is obtained more in the disk than in the bone (>50%), an additional anterior approach is performed: more through the disk than the vertebral body (>50%)). This reliable technique meets the requirements of sagittal posttraumatic kyphosis correction, and provides a solid construct which avoids bracing.

Biomechanical evaluation of a bipedicular spinal fixation system: a comparative stiffness test.

Study Design. This biomechanical study using cadaver thoracic spines evaluated the initial stiffness of two different fixation constructs using a new spinal implant: the bipedicular spinal fixation device (BSF). Objective. To compare the biomechanical stiffness of a new construct using BSF with a regular construct using pedicular and laminar hooks. Summary of Background Data. Disadvantages of thoracic posterior implants and developments in in situ rod contouring led to the creation of a new implant for spine deformity surgery that would provide immediate stiffness to preserve spine correction, allow efficient postoperative rehabilitation, and obtain a good fusion rate. Methods. Two age-paired groups of six human thoracic spines each (T3–T12) were compared: a regular group whose construct was in accordance with the Cotrel–Dubousset technique and the BSF group. In both groups, the spines were tested intact and then after injury. An injury was induced by transections of interspinous and anterior longitudinal ligaments and anterior discectomies. A three-dimensional ultrasonic measurement device, the Zebris 3D Motion Analyzer, was used to record the motion of the T6 relative to the T8 vertebra under loads, and to determine the ranges of motion (ROMs) between intact spines and the spine construct. Results. In flexion–extension, the regular construct showed a significantly greater mean of relative ROMs than the BSF construct for principal rotation (88% and 69% respectively, P = 0.015). However, no significant differences were demonstrated in any of the other motions. Conclusion. The BSF construct showed stiffness similar to that of the regular construct, encouraging clinical investigation.

Percutaneous Image-guided Laser Photocoagulation of Spinal Osteoid Osteoma: A Single-Institution Series

PURPOSE To retrospectively evaluate the safety and efficacy of percutaneous image-guided laser photocoagulation for the treatment of spinal osteoid osteoma (OO) in proximity to neural structures. MATERIALS AND METHODS This study was institutional review board-approved with waivers of informed consent. From January 1994 until October 2014, 58 patients with spinal OO (mean age, 25 years; 40 men, 17 women) were treated in one institution by using laser photocoagulation with combined computed tomographic (CT) and fluoroscopic guidance. One patient was excluded because of less than 3 months of follow-up. All patients had typical clinical and imaging findings. Clinical features, radiologic data, and procedure-related data were reviewed, and limitations, complications, and failure rate were evaluated. All data were expressed as means ± standard deviation. P values of less than .05 were indicative of statistical significance. RESULTS OO was in the vertebral body for 18 of 57 patients, the neural arch for 21 of 57 patients, and the articular process for 18 of 57 patients. Mean nidal diameter was 8 mm, and the mean distance from the closest neural structure was 6.6 mm (minimum distance, ≤5 mm in 35 of 57 patients). In 35 of 57 patients, no cortical coverage was present between the nidus and neural structure in danger. Mean total energy delivered was 1271 J (2-watt continuous power mode). Thermal insulation (carbon dioxide and/or hydrodissection), temperature monitoring, and electrostimulation were used in 42, 24, and one patient, respectively. Primary clinical success at 1 month was 98.2%. Total recurrence rate was 5.3%. All recurrences were addressed percutaneously. Secondary success rate was 100%. One-year follow-up is available in 54 of 57 patients. No major complications were noted. CONCLUSION Spinal OO can be safely and effectively treated with percutaneous laser photocoagulation. In cases that are less than 8 mm to 10 mm distance and in the absence of cortical coverage, thermal protection techniques of the neural structures should be used.