Posterior Spinal Column Research Articles

Treatment of Thoracic Tuberculosis Through Posterior Costal Transverse Joint Window: A Clinical Study

BackgroundThe surgical treatment of thoracic spinal tuberculosis has garnered enormous interest from researchers towards the development of posterior surgical techniques that have contributed to greater use of the one-stage posterior approach. This study aims to demonstrate the initial clinical experience of a modified total posterior approach, in which the one-stage posterior approach preserves the posterior spinal column structure by combining with the endoprosthetic implant fusion for thoracic spinal tuberculosis. MethodsIn this clinical study, we intended to report the initial idea of a modified total posterior approach. In detail, a one-stage posterior approach was applied to preserve the posterior spinal column structure that could be applied to clinical practice. ResultsThe employed practical procedure presented a reduced duration of surgical intervention and intraoperative trauma. Nevertheless, further studies with large samples and multiple centers are required to explore the idea comprehensively. ConclusionsThis approach offered some advantages in terms of intraoperative exposure, blood loss volume, and length of surgery. Further, multi-center studies with large samples are needed to understand the precise effects and implications of the approach.

Clinical value and effectiveness profiles of oblique lateral interbody fusion and posterior lumbar interbody fusion in the treatment of lumbar brucellosis spondylitis.

The aim of this study was to assess the clinical efficacy of oblique lateral interbody fusion (OLIF) and posterior lumbar interbody fusion (PLIF) for lumbar brucellosis spondylitis. Between April 2018 and December 2021, 80 cases of lumbar brucellosis spondylitis admitted to our institution were evaluated for eligibility and randomly assigned to either PLIF (group A, lesion removal by posterior approach + interbody fusion + percutaneous pedicle screw internal fixation) or OLIF (group B, lesion removal by anterior approach + interbody fusion + percutaneous pedicle screw internal fixation). The outcome measures included operative time, intraoperative bleeding, hospital stay, preoperative and postoperative visual analogue scale (VAS) ratings, American Spinal Injury Association (ASIA) classification, Cobb angle, and interbody fusion time. PLIF resulted in shorter operative time and hospital stay and less intraoperative bleeding vs. OLIF (p<0.05). All eligible patients showed significantly lower VAS scores, and smaller ESR values and Cobb angles after treatment (p<0.05), but no significant intergroup differences were observed (p>0.05). The two groups showed similar preoperative ASIA (American Spinal Injury Association) classification and interbody fusion time (p>0.05). PLIF was associated with better ASIA classification at three months postoperatively vs. OLIF (p<0.05). Both surgical techniques are efficient at removing the lesion, relieving pain, maintaining spinal stability, promoting implant fusion, and facilitating prognostic inflammation control. PLIF features a shorter surgical duration and hospital stay, less intraoperative bleeding, and greater neurological improvement vs. OLIF. Nevertheless, OLIF outperforms PLIF in the excision of peri-vertebral abscesses. PLIF is indicated for posterior spinal column lesions, particularly those with spinal nerve compression in the spinal canal, whereas OLIF is indicated for structural bone deterioration in the anterior column, particularly for those with perivascular abscesses.

Lateral lumbar spine surgery: Fixation considerations

Lateral approaches to the lumbar spine offer an alternative technique for addressing numerous diseases of the lumbar spine. The retroperitoneal approach provides a surgical corridor that affords the use of large interbody footprints while maintaining the stabilizing ligaments of the anterior and posterior spinal columns and mitigating the need for mobilization of the great vessels associated with an anterior approach. While the literature highlights clinical scenarios whereby standalone lateral interbody devices may be used, supplemental fixation is often warranted. Supplemental fixation strategies include integrated interbody or supplemental lateral plate fixation, interspinous process fixation, facet screw, or pedicle screw fixation.

Posterior Focal Curettage and Spine Stability Reconstruction by Temporary Pedicle Screw Fixation in Children With Collapsed Vertebrae due to Eosinophilic Granuloma.

Study Design:Retrospective case series.Objectives:To evaluate the efficacy of growth-preserving posterior spinal column reconstruction surgery in children with collapsed vertebral eosinophilic granuloma (EG).Methods:We retrospectively reviewed 15 confirmed cases of vertebral EG who met the inclusion and exclusion criteria from March 2015 to March 2018 in our hospital. The recovery of diseased vertebrae was assessed.Results:The cases were composed of 11 males and 4 females with a mean age of 74.3 ± 38.8 months. Nine cases presented with thoracic vertebral destruction, 6 cases with lumbar vertebral destruction. Under Garg’s classification, 10, 3 and 2 cases were classified as Grade IIA, IB and IIB lesions, respectively. All patients had mild to moderate night-aggravated back pain and recovered at 1-week after surgery. Three patients had Frankel D neurologic symptoms and recovered at 1-week, 1-week and 4-weeks after surgery, respectively. Follow-up time after surgery ranged from 1.9 years to 4.5 years, with a mean of 2.9 years. The median vertebral height at 12 months after surgery was significantly higher than the preoperative height. Furthermore, the vertebral heights of all diseased vertebrae displayed significant recovery trends at 3, 6 and 12 months after surgical treatment. The percentages of vertebral height recovery to references at 12 months after surgery ranged from 34.7% to 92.5%, with an average of 71.2%.Conclusions:In children with collapsed vertebral EGs, active surgical treatment is necessary to retain the ability to restore height and to reconstruct the spine stability.

A Retrospective Study of Factors Associated with Restoration of Thoracic Kyphosis in 43 Patients with Adolescent Idiopathic Scoliosis with Lenke Type 1 Curvature.

BackgroundThis retrospective study aimed to identify the factors associated with successful surgical correction of thoracic kyphosis (TK) in 43 patients with adolescent idiopathic scoliosis (AIS) with Lenke type 1 curvature, in which the major curve with the largest Cobb angle was mainly in the thoracic region.Material/MethodsWe collected data from patients with Lenke 1 AIS. The following parameters were measured: Cobb angle, side-bending Cobb angle, cervical lordosis (CL), TK, lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), the sagittal vertical axis (SVA), the center of a C7 plumb line to the center sacral vertical line (C7-CSVL), correction rate, Ponte osteotomy, flexibility, and screw density. Univariate analysis and multivariate logistic regression analyses were performed.ResultsAmong the 43 cases analyzed, the mean postoperative Cobb angle at the last follow-up, C7-CSVL, SVA, CL, TK, LL, PI, SS, and PT were respectively 21.33±9.47°, 10.41±8.45 mm, 19.68±14.33 mm, 16.19±7.45°, 23.12±7.45°, 50.33±11.37°, 49.70±9.83°, 39.42±8.11°, and 10.16±6.63°. Univariate analysis suggested that preoperative TK, preoperative LL, and Ponte osteotomy were statistically significant (P<0.05), and multivariate analysis suggested that preoperative LL and Ponte osteotomy were statistically significant (P<0.05).ConclusionsThe results of this study demonstrated that preoperative TK, preoperative LL, and Ponte osteotomy were related factors for maintaining normal TK. Multivariate analysis suggested that preoperative LL and the use of Ponte osteotomy with full-thickness segmental resection of the spinal posterior column resulted in the successful surgical correction of TK in patients with AIS with Lenke type 1 curvature.

Prone Transpsoas Technique for Simultaneous Single-Position Access to the Anterior and Posterior Lumbar Spine.

Effective decompression, arthrodesis, and correction of spinal conditions frequently utilize operative approaches that expose both the anterior and posterior spinal column. Until now, circumferential spinal column access often requires the surgeon to reposition and drape the patient multiple times or utilize a posterior only approach that has limited anterior correction capability or to utilize a lateral-only approach that complicates otherwise traditional posterior surgical maneuvers. To describe a technique utilizing a single surgical position that enables minimally disruptive anterior column correction with simultaneous access to the posterior spinal column. The operative technique for accessing the lateral lumbar interbody space from a prone transpsoas (PTP) approach is described. The rationale for this approach and a representative case example are reviewed. The PTP approach was used to perform an L3-4 and L4-5 interbody fusion in a 71-yr-old female with spondylolisthesis, severe stenosis, and locked facets. The PTP approach enabled efficient completion of an anterior column correction, direct posterior decompression, multi-segment pedicle fixation, and maintenance of alignment, all while in a single prone position. There were no intraoperative or postoperative complications. The authors' early experience with the described PTP technique suggests it is not only feasible but offers some advantages, as it allows for single-position surgery maximizing both anterior and posterior column access and corrective techniques. Further follow-up studies of this technique are ongoing.

Spino-Pelvic Thresholds for Prevention of Proximal Junctional Kyphosis Following Combined Anterior Column Realignment and Short Posterior Spinal Fusion in Degenerative Lumbar Kyphosis.

ObjectiveTo analyze ideal indication for combined anterior column realignment (ACR) with short posterior spinal fusion (PSF) and posterior column osteotomy (PCO) for preventing proximal junctional kyphosis (PJK) in adult spinal deformity (ASD) patients with lower lumbar kyphosis and compensatory thoracolumbar lordosis.MethodsA retrospective study was conducted. This study included 27 ASD patients (average age of 66.6 years; one male and 26 females) with lower lumbar kyphosis and compensated thoracolumbar lordosis who underwent short PSF with PCO following ACR from 2006 to 2010. The minimum follow‐up period was 5 years. The patients were divided into two groups based on the sagittal vertical axis (SVA) of the last follow‐up radiographs, and a comparative analysis was performed evaluating spino‐pelvic parameters and clinical outcomes including the Oswestry Disability Index (ODI), Visual Analog Scale (VAS), and complications.ResultsThe mean follow‐up time of included patients was 109.7 months, and the mean number of fused segments was 3.7. The uppermost instrumented vertebra was L2 in 18 patients or L3 in nine patients, and lowermost instrumented vertebra was sacrum in all patients. The mean lumbar lordosis (LL) values in the optimal SVA and suboptimal SVA groups were 4.4° and 4.2° preoperatively (P = 0.639), −48.1° and −35° postoperatively (P = 0.007), and −45.2° and −20.7° at the last follow‐up (P < 0.05). Overcorrection was seen in seven patients in the optimal SVA group, whereas all of the patients of the suboptimal SVA group were in the category of undercorrection (P = 0.021). Pelvic incidence (PI) of optimal SVA group (<50 mm, n = 16) and suboptimal SVA group (≥50 mm, n = 11) was 44.1° and 53.8° (P = 0.009). The prevalence of PJK was significantly higher in the suboptimal SVA group (P = 0.008), and last follow‐up VAS for back pain (P < 0.05), and postoperative and last follow‐up ODI (P = 0.002 and P < 0.05) were statistically larger for the suboptimal group than the optimal group.ConclusionsCombined ACR with short PSF and PCO could effectively prevent sagittal decompensation of PJK and help achieve sagittal balance in the treatment of ASD patients with lower lumbar kyphosis, compensatory thoracolumbar lordosis, and especially low PI (<50°).

Atypical presentation of clay shoveler’s fracture: A case report and literature review

Clay shoveler’s fracture causes disruption of the spinous processes at C6 to T3 spinal vertebrae. This is a case report of an atypical clay shoveler’s fracture from Babcock university teaching Hospital ,Ogun-state, Nigeria. It involved a 62-year-old male travelling in the south-western region of Nigeria who was invloved in a Road traffic accident and presented with pain at the posterior aspect of the neck. X-ray and 3D oriented CT scan confirmed the fractures with lateral views being the most favored. Classical Clay shoveler’s fracture usually has no neuromuscular deficit since it is a stable fracture and involves only the posterior spinal column based on the Denis classification for 3 column concept for stable and unstable fractures of the spine. When a fracture involves the spinolaminar line it’s proximity to the spinal cord and risk of neurological deficit must be adequately ruled out. This report evaluates the mechanism of injury, treatment given and prognosis of the patient involved.

Correction of rotational deformity and restoration of thoracic kyphosis are inversely related in posterior surgery for adolescent idiopathic scoliosis

Adolescent Idiopathic Scoliosis (AIS) is a complex three dimensional deformity the treatment of which remains to be surgical correction of the deformity as it had progressed over certain thresholds. The main focus in surgical treatment had, for decades, been the amount of correction in the coronal plane whereas corrections in sagittal and rotational (axial) planes have also been recognized as almost as important as the coronal over the recent decades.The hypotheses presented and discussed in this study is the virtual adversity between the rates of correction in these two (sagittal and axial) planes. Namely, we are suggesting that due to an elongated anterior spinal column as an intrinsic component of AIS, posterior surgery cannot correct both the axial plane deformity and the thoracic hypokyphosis in the sagittal plane at the same time, unless the posterior spinal column is substantially lengthened. This hypothesis is supported by 3D modeling of the AIS spine as well as the relative inability in changing the sagittal alignment of the thoracic spine demonstrated by a literature search by us.Understanding and internalization of this hypothesis by AIS surgeons is important as it suggests that by posterior instrumentation, unless a riskier approach of substantially lengthening the spinal column is taken, surgeons need to make the choice of correcting the hypokyphosis OR axial rotation.

Kinetic change of spinal cord compression on flexion-extension magnetic resonance imaging in cervical spine

ObjectiveWe aimed to determine the changes in cervical canal diameters and spinal cord compression at each level from C2-3 to C7-T1 in flexion and extension positions and to study the use of flexion-extension magnetic resonance imaging (MRI). We also aimed to assess the changes in the length of the spinal cord in flexion and extension positions of the cervical spine. Patients and methodsFlexion-extension MRI scans were performed consecutively on sixty-six patients with neck pain with/without neurogenic symptoms of the cervical spine. All patients were treated conservatively. We investigated the length of the cervical spinal cord (LSC), length of the cervical spinal anterior column (LAC), length of the cervical spinal posterior column (LPC), spinal canal diameter, and severity of cord compression in flexion, neutral, and extension positions. ResultsAt each intervertebral level (from C2-3 to C7-T1), the average spinal canal diameter showed significant decrease from flexion to extension positions (P < 0.05). The average LSC, LAC, and LPC were decreased on extension of the neck compared with flexion (P < 0.05). Higher stages were found in extension position than in flexion position with statistically significant differences (P < 0.05). ConclusionThe use of flexion-extension MRI may demonstrate true pathology that contributes in the pathogenesis of cervical degenerative disease (CDD). Higher stages in spinal cord compression were found in extension position than in flexion position. However, higher stages in spinal cord compression in extension position did not necessarily cause severe myelopathy. This finding is an important evidence for conservative therapy on patient neck position education.

Anterior-posterior length discrepancy of the spinal column in adolescent idiopathic scoliosis—a 3D CT study

Background ContextOne of the characteristics of reported observations in adolescent idiopathic scoliosis (AIS) is that the thoracic spine is longer anteriorly than posteriorly, more pronounced around the apex than the transitional zones. This reversal of the normal kyphotic anatomy of the thoracic spine is related to questions of etiopathogenesis of AIS. The changes in the anatomy of the anterior column have been described rather in detail; however, the role of the posterior spinal column and the laminae has so far not been elucidated. If the posterior column exhibits a longitudinal growth disturbance, it could act as a tether, leading to a more or less normal anterior column with a deformed and shorter posterior aspect of the spine. So far, it has remained unclear whether this anterior-posterior length discrepancy is the result of relative anterior lengthening or relative posterior shortening, and which tissues (bone, disc, intervertebral soft tissue) are involved. PurposeThe present study aimed to compare the discrepancy of the anterior-posterior length of the spinal column in the “true” midsagittal plane of each vertebra in patients with idiopathic scoliosis versus controls, using three-dimensional computed tomography (CT) scans. Study Design/SettingThis is a cross-sectional study. Patient SampleThe sample consisted of computed tomography scans of 80 patients with moderate to severe AIS (Cobb angle: 46°–109°) before scoliosis navigation surgery and 30 non-scoliotic age-matched controls. Outcome MeasuresThe height of the osseous and non-osseous structures from anterior to posterior in the “true” midsagittal plane has been determined: the anterior side of the vertebral body and disc, the posterior side of the vertebral body and disc, the lamina and interlaminar space and the spinous process and interspinous space, as well as the height ratios between the anterior column and posterior structures of the primary thoracic and lumbar AIS curves and corresponding levels in non-scoliotic controls. MethodsSemiautomatic software was used to reconstruct and measure the parameters in the true midsagittal plane of each vertebra and intervertebral structure that are rotated and tilted in a different way. ResultsIn AIS, the anterior height of the thoracic curve was 3.6±2.8% longer than the posterior height, 2.0±6.1% longer than the length along the laminae, and 8.7±7.1% longer than the length along the spinous processes, and this differed significantly from controls (−2.7±2.4%, −7.4±5.2%, and +0.7±7.8%; p<.001). The absolute height of the osseous parts did not differ significantly between AIS and controls in the midsagittal plane. In contrast, the intervertebral structures contributed significantly to the observed length discrepancies. In absolute lengths, the anterior side of the disc of the thoracic curve was higher in AIS (5.4±0.8 mm) than controls (4.8±1.0 mm; p<.001), whereas the interspinous space was smaller in AIS (12.3±1.4 mm vs. 14.0±1.6 mm; p<.001). ConclusionsBased on this in vivo analysis, the true three-dimensional anterior-posterior length discrepancy of AIS curves was found to occur through both anterior column lengthening and posterior column shortening, with the facet joints functioning as the fulcrum. The vertebrae contribute partly to the anterior-posterior length discrepancy accompanied by more significant and possibly secondary increased anterior intervertebral discs height.

Minimally invasive anterior, lateral, and oblique lumbar interbody fusion: a literature review.

Lumbar interbody fusion involves insertion of a structural graft into an intervertebral disc space to promote bony arthrodesis. It is a well-established surgical strategy for multiple spinal disorders ranging from degenerative conditions to trauma, neoplastic diseases, and deformities requiring correction. Since the inception of lumbar interbody fusion, the most established techniques have been two posterior approaches, the posterior lumbar interbody fusion (PLIF) and the transforaminal lumbar interbody fusion (TLIF). Within the past 15 years, multiple anterolateral approaches to the spine have become widely adopted. These approaches can be performed minimally invasively and spare disruption of the paraspinal muscles and posterior spinal column while enabling wide exposure of the disc space for insertion of interbody grafts much larger than PLIF and TLIF instrumentation. This review highlights three minimally invasive anterolateral approaches: the anterior lumbar interbody fusion (ALIF), the transpsoas lateral lumbar interbody fusion (LLIF), and prepsoas or anterior to the psoas oblique lumbar interbody fusion (OLIF). Relevant topics for discussion and comparison include patient selection, surgical techniques, outcomes, and complications for the three surgical approaches.

Investigation of stress-strain state in spinal model for various methods of surgical treatment of thoracolumbar burst fractures (Рart one)

There are different views on the treatment of burst fractures of the lower thoracic and lumbar spine. Some specialists pre­fer conservative methods of treatment, others use a spinal fu­sion of 360° (anterior and posterior). However, questions of the extent of fixation, its strength, the possibility of correc­tion of deformation from the posterior approach, the feasibil­ity of performing laminectomy, etc. are discussed. Objective: to create a finite element biomechanical model of an burst frac­ture of the ThXIIvertebra body in the ThIX–LVvertebra block and analyze the stress-strain state in different fixation types. Methods: three computational models of the ThIX–LVvertebra block were created with the destruction of 50 % of the body volume of the ThXIIvertebra and fixation: 1) ThIXand LV; 2) ThIX, ThXIIand LI; 3) ThX, ThXIand LI, LII, as well as variants of the model with destruction of vertebral pedicles. Results: with the verti­cal load, the posterior spinal column is the most stressed, and the maximum stresses (45.9–46.6 MPa) in the fixing structures are located in the rods. In the case of fixation by 6 screws, the stresses in the rods are reduced by approximately 20 % (to 37.7–38.1 MPa). With the use of 8 screws, the total stress level compared to the fixation of 4 and 6 screws significantly decreased, in particular in the block of vertebrae LI–LValmost twice. Damage to the posterior support complex in the form of vertebral arches fracture led to a significant increase in ten­sion (by 17 %) in the injured vertebral body only in a model with 4 screws. Conclusions: the use of any transpedicular fixa­tion leads to a decrease in stress in the damaged vertebra. With an increase in the number of screws in the fixing structure, the level of stresses decreases, but the pattern of their distribu­tion in the spine does not change.

Anatomic and functional reconstruction of the spinal posterior column after resection of intraspinal neoplasms

Objective To investigate the operative outcomes of anatomic and functional reconstruction of the spinal posterior column after resection of intraspinal neoplasms. Methods From January 2010 through October 2014, we treated 32 patients with intraspinal neoplasm in the spine. They were 18 men and 14 women, 13 to 62 years of age (average, 38 years). The neoplasm was detected in the cervical spine in 10 cases, in the thoracic spine in 14 and in the lumbar spine in 8. All cases received expansive open door laminoplasty via the posterior approach for resection of the intraspinal neoplasm, followed by replantation and titanium plate fix-ation for anatomic and functional reconstruction of the spinal posterior column. The neural functional recovery, spinal motion and sagittal diameter of the spinal canal before and after operation, spinal stability and graft fusion were observed. Results The patients were followed up for 3 to 23 months (average, 13 months). All the intraspinal neoplasms were completely resected. The Frankel grading of neural functional recovery was improved differently in all the cases. By the final follow-ups, the spinal motion was normal in all the cases, without any significant limitation. Graft fusion and rigid internal fixation were achieved in all the cases. Short-term follow-ups revealed no signs of spondylolisthesis or spinal instability. At the final follow-ups, the 3-D CT reconstruction showed no significant shortening in the sagittal diameter of the same spinal canal before and after operation (P >0.05). Conclusions For intraspinal neoplasm in the spine, the whole vertebral lamina is opened or re-moved via the posterior approach to resect the neoplasm, followed by reduction of the vertebral lamina and mini titanium plate fixation to reconstruct the anatomy and function of the original spine. This is an ideal way to treat intraspinal neoplasms in the spine. Key words: Spine; Reconstructive surgical procedure; Treatment outcome; Posterior approach

Energy Criterion in the Assessment of Damping of a Spinal Motion Segment Subjected to Cyclic Loading

The primary functions of the spine, and in particular the intervertebral disc, are to support transfer of loads, permit motion, and dissipate energy in the spine. The objective of this study was to analyse changes in damping of a spinal motion segment subjected to cyclic loading using the energy criterion. Another important aspect of the undertaken study was an evaluation of the impact of posterior spinal column elements, i.e. articular processes joints on changes in energy dissipation by the intervertebral disc.

SU‐E‐T‐369: Evaluating Intensity Modulated Proton Therapy Relative to Passive Scattering Proton Therapy for Increased Vertebral Column Sparing in CSI of Pediatric Patients

Purpose:To investigate the trade‐off between vertebral column sparing and thecal‐sac target coverage in craniospinal irradiation (CSI) of pediatric patients treated with passive‐scattering (PS) and intensity modulated (IMPT) proton therapy.Methods:We selected 2 pediatric patients treated with PS CSI for medulloblastoma. Spinal irradiation was re‐planned with IMPT. For all cases, we assumed prescription dose of 23.4 Gy(RBE), with the spinal canal receiving at least 95% of 23.4 Gy(RBE). PS planning was performed using the commercial system XiO. IMPT planning was done using the Astroid planning system. Beam arrangements consisted of (a) PS posterior‐anterior (PA) field, PS‐PA, (b) IMPT PA field, IMPT‐PA, and (c) two posterior oblique IMPT fields, IMPT2 (‐35°, 35°). Dose distributions were re‐calculated using TOPAS Monte Carlo, along with LET distributions, to investigate LET variations within the target and vertebra anatomy. Variable RBE‐weighed dose distributions were also calculated based on a dose and LET‐dependent biophysical model. Dosimetric data were compared among the plans for the target volume, spinal cord and adjacent critical organs (thecal‐sac and cauda equina).Results:IMPT2 resulted in better sparing of the posterior vertebral column (entrance region posterior to thecal‐sac), where planned dose was approximately 6–8Gy(RBE). For IMPT‐PA and PS‐PA the MC‐calculated dose to the posterior vertebral column was, on average, 20Gy and 18Gy respectively. For IMPT2 higher mean‐LET (5keV/µm/(g/cm3)) values were observed in anterior vertebral column (beyond the thecal‐sac) relative to IMPT‐PA and PS‐PA, where mean‐LET was 3.5keV/µm/(g/cm3) and 2.5keV/µm/(g/cm3) respectively. The higher LET region observed for both IMPT plans was in the distal end of treatment fields, where dose delivered was less 5Gy(RBE).Conclusion:The two‐oblique proton beams IMPT2 best spared the spinal column, while reducing the dose to the posterior spinal column from 18–20 to 6–8 Gy(RBE). The best LET distribution was obtained with the PS‐PA fields.

Increase or decrease in stability after nucleotomy? Conflicting in vitro and in vivo results in the sheep model.

Nucleotomy is a common surgical procedure to treat disc herniations. The potential occurrence of segmental instability after surgery, however, is suspected to necessitate re-operation and fusion. Although in vitro studies support the theory of destabilization after nucleotomy, a prior, in-house animal study contrarily revealed an increase in stability after surgery. To identify which structural compartment of the motion segment is decisive for increased stability after nucleotomy in vivo, the flexibilities of ovine motion segments were measured after different stepwise reductions at the anterior and posterior spinal column. Different test groups were used in which nucleotomy had been performed during surgery in vivo and under isolated in vitro conditions, respectively. In accordance with expectations, in vitro nucleotomy on ovine motion segments significantly increased flexibility. By contrast, nucleotomy significantly decreased flexibility 12 weeks after surgery. After removal of the posterior structures, however, the differences in flexibility diminished. The present results thus suggest that it might not exclusively be the trauma to the intervertebral disc during surgery which is decisive for post-operative stability, but rather adaptive mechanisms in the posterior structures. Therefore, care should be taken to minimize the damage to the posterior structures in the course of the surgical approach, which more likely compromises stability.

Flexion-distraction injuries of the thoracolumbar spine: open fusion versus percutaneous pedicle screw fixation

Flexion-distraction injuries occur due to distractive forces causing disruption of the posterior and middle spinal columns. These fractures classically consist of a fracture line through the posterior bony elements; involvement of the posterior ligamentous complex is, however, common. Surgical treatment is often required for these unstable injuries to avoid neurological deterioration and posttraumatic kyphosis, and the surgery traditionally consists of an open posterior approach with instrumented fusion. Percutaneous pedicle screw fixation for these injuries, with the goal of minimal tissue disruption and preservation of normal anatomy while achieving adequate stabilization, has recently been reported in the literature, but to date, a direct comparative study comparing open and percutaneous fixation has not been reported. The authors report their experience treating these fractures with both techniques and review the available literature. Patients with flexion-distraction injury who were treated between May 2003 and March 2013 were prospectively followed. American Spinal Injury Association scores and degree of kyphotic angulation were recorded at admission, discharge, and follow-up. Data regarding intraoperative blood loss and operative time were obtained from a chart review. Patients treated with open versus minimally invasive procedures were compared. The authors identified 39 patients who suffered flexion-distraction injuries and were treated at their institution during the specified period; one of these patients declined surgery. All had injury to the posterior ligamentous complex. Open surgical procedures with pedicle screw fixation and posterolateral fusion were performed in 27 patients, while 11 patients underwent minimally invasive pedicle screw placement. Overall, there was improvement in kyphotic angulation at the time of discharge as well as most recent follow-up in both the open surgery and minimally invasive surgery (MIS) groups. The authors found no significant difference in American Spinal Injury Association score or the degree of kyphotic angulation between the MIS and open surgery groups. There was a trend toward shorter operative time for the MIS group, and patients who underwent minimally invasive procedures had significantly less blood loss. Minimally invasive percutaneous pedicle screw fixation appears to have similar efficacy in the treatment of flexion-distraction injuries and it allows for reduced blood loss and tissue damage compared with open surgical techniques. Therefore it should be considered as an option for the treatment of this type of injury.

Mechanisms of postural instability in hereditary spastic paraplegia

Hereditary spastic paraplegia (HSP) is characterized by progressive lower extremity spasticity and weakness, due to retrograde axonal degeneration of the corticospinal tract and posterior spinal columns. HSP patients fall frequently. We hypothesized that delayed postural responses contribute to their balance impairments. To distinguish between a delay in afferent and efferent signals, we combined postural responses with a startling acoustic stimulus (SAS). The SAS triggers a postural response directly, bypassing afferent proprioceptive input. We performed two experiments. First, 18 HSP patients and nine healthy controls stood on a balance platform and were instructed to counteract forward and backward balance perturbations, without taking a step or grabbing a handrail. Second, 12 HSP patients and nine controls received backward perturbations, while a SAS accompanied onset of platform motion in 25% of trials. HSP patients were less successful than controls in maintaining balance following backward and forward perturbations. Furthermore, latencies of postural responses were significantly delayed in HSP-patients, by 34 ms in gastrocnemius following forward, and by 38 ms in tibialis anterior following backward perturbations. A SAS accelerated postural responses in all participants, but more so in HSP patients whose latencies were normalized. Our results suggest that delayed postural responses in HSP patients contribute to their balance problems. Combining balance perturbations with a SAS restored normal latencies, suggesting that conduction of efferent signals (presumably by the reticulospinal tract) is normal. We therefore suggest that the delayed postural responses in HSP are caused by slowed conduction time via the posterior spinal columns.

Imaging Findings of the Posterior Spinal Column and Potential Correlation With Back Pain

Imaging Findings of the Posterior Spinal Column and Potential Correlation With Back Pain