Short-segment Posterior Instrumentation Research Articles

Should the level of the posterior instrumentation combined with the intermediate screw be a short segment or a long segment in thoracolumbar fractures with fusion to the fractured segment?

It was aimed to compare the results of long segment posterior instrumentation with intermediate pedicular screw + fusion at the level of the fractured segment including one vertebra above and one below the fractured vertebra (LSPI) and short segment posterior instrumentation with intermediate pedicular screw + fusion at the level of the fractured segment including one vertebra above and one below the fractured vertebra (SSPI) in the surgical treatment of thoracolumbar vertebral fractures. Ninety patients with thoracolumbar vertebral (T11-L2) fractures operated between March 2015 and February 2022 were included in this retrospective study. The patients were divided into two groups as those who underwent LSPI (n, 54; age, 40.3) and those who underwent SSPI (n, 36; age, 39.7). Radiological evaluations like vertebral compression angle (VCA), vertebral corpus heights (VCH), intraoperative parameters, and complications were compared between the groups. Correction in early postoperative VCA was statistically significantly better in LSPI (p = 0.003). At 1-year follow-up, postoperative VCA correction was significantly more successful in LSPI (p = 0.001). There was no difference between the two groups in terms of correction loss in VCA measured at 1-year follow-up. There was no statistically significant difference between the two groups in terms of postoperative VCH, VCH at 1-year follow-up, and correction loss in VCH. LSPI provides better postoperative kyphosis correction of the fractured vertebra than SSPI. Regarding the segment level of posterior instrumentation, there was no difference between the two groups in terms of the loss of achieved correction of VCA, ABH, and PBH at 1-year follow-up. Operating a thoracolumbar fracture with LSPI will lengthen the operation and increase the number of intraoperative fluoroscopies compared to SSPI.

The effect of the size of pedicle screw on the long-term radiological and clinical results of short-segment posterior instrumentation in the management of thoracolumbar vertebral fractures.

It was aimed at evaluating the effect of the size of the pedicle screw placed on the fractured vertebra on the long-term radiological and clinical results of short-segment posterior instrumentation applied in the surgical treatment of thoracolumbar vertebral fractures. This retrospective study included 36 patients who underwent short-segment posterior instrumentation surgery for a single-level thoracolumbar (T11-L2) fracture between January 2015 and March 2021. The patients included in the study were divided into 2 groups according to the size of the pedicle screw placed in the fractured vertebra (group A: intermediate screw 4.5 mm, ≤35 mm+less than 50% of the vertebral corpus length, m/f: 13/4, n: 17, age: 36.5; group B: intermediate screw 5.5 mm, ≥40 mm+more than 70% of the vertebral corpus length, m/f: 11/8, n: 19, age: 42.6). All patients were periodically evaluated clinically and radiologically. Vertebral compression angle (VCA), anterior and posterior vertebral body height (ABH-PBH), intraoperative parameters (instrumentation time and intraoperative fluoroscopy number), and complications were compared between the 2 groups. Both groups were comparable with respect to age, sex, level of injury, AO classification, mechanism of injury, and American Spinal Cord Injury Association impairment scale. Restoration of VCA and vertebral corpus heights was achieved sufficiently in both groups after operation (P < .0001). There was no significant difference between the 2 groups in terms of early postoperative VCA, VCA measured at final follow-up, or loss of correction in VCA. At the last follow-up, PBH was statistically significantly better preserved in group B (P=.0424). There was no difference between the 2 groups in terms of operation time and the number of intraoperative fluoroscopies. Implant failure was observed in 1 patient in group A. This study has revealed that using a long, thick pedicle screw placed in the fractured vertebra can better preserve the PBH at the final follow-up. No correlation was found between the size of the intermediate screw and the preservation of the correction in the postoperative vertebral heights and VCA during the follow-up. Level III, Therapeutic Study.

491 Durability of Short Segment Instrumentation With Vertebrectomy in the Setting of Metastatic Disease to the Thoracic Spine

INTRODUCTION: Current treatment of spinal metastases in the thoracic spine requiring vertebrectomy entails pedicle screw fixation at least two levels above and below the level of reconstruction. METHODS: We reviewed a series of 30 patients treated for single-level, non-junctional (T2 to T11) thoracic spinal metastasis via single level vertebrectomy with posterior short segment instrumentation. The primary outcome was need for reoperation due to construct failure. Secondary outcomes included local tumor recurrence, pain scores, neurological function, estimated blood loss, operative time, length of hospital stay, and post-operative wound complications. RESULTS: The most common primary tumor origin was non-small cell lung carcinoma (n = 9). All patients had a SINS score of at least 10 and Bilsky Grade of 2 or 3. Mean intraoperative blood loss was 605 mL (range 50 – 1200 mL) and mean operative time was 260.73 minutes (range 169 to 442 minutes). Two patients suffered perioperative complications but there was no construct failure or need for revision surgery at any time during the follow-up period. Mean length of follow-up was 24 months (range 1-65 months). An overall improvement in pain was seen postoperatively (7.67 versus 2.77, p &lt; 0.001) and no patient experienced worsening neurological function. Average length of stay was six days. Three patients in this cohort had local tumor recurrence, although two of these patients suffered from a radioresistant tumor pathology. CONCLUSIONS: Our results encourage consideration of this less invasive technique in the management of patients suffering from metastatic disease requiring vertebrectomy and reconstruction in the non-junctional thoracic spine.

Treatment and Outcome of Osteoporotic Thoracolumbar Vertebral Fractures With Anterior or Posterior Tension Band Failure (OF 5): Short-Term Results From the Prospective EOFTT Multicenter Study

Subgroup analysis of a multicenter prospective cohort study. To analyse surgical strategies applied to osteoporotic thoracolumbar osteoporotic fracture (OF) 5 injuries with anterior or posterior tension band failure and to assess related complications and clinical outcome. A multicenter prospective cohort study (EOFTT) was conducted at 17 spine centers including 518 consecutive patients who were treated for an osteoporotic vertebral fracture (OVF). For the present study, only patients with OF 5 fractures were analysed. Outcome parameters were complications, Visual Analogue Scale (VAS), Oswestry Disability Questionnaire (ODI), Timed Up & Go test (TUG), EQ-5D 5L, and Barthel Index. In total, 19 patients (78 ± 7 years, 13 female) were analysed. Operative treatment consisted of long-segment posterior instrumentation in 9 cases and short-segment posterior instrumentation in 10 cases. Pedicle screws were augmented in 68 %, augmentation of the fractured vertebra was performed in 42%, and additional anterior reconstruction was done in 21 %. Two patients (11 %) received short-segment posterior instrumentation without either anterior reconstruction or cement-augmentation of the fractured vertebra. No surgical or major complications occurred, but general postoperative complications were observed in 45%. At a follow-up of mean 20 ± 10 weeks (range, 12 to 48 weeks), patients showed significant improvements in all functional outcome parameters. In this analysis of patients with type OF 5 fractures, surgical stabilization was the treatment of choice and lead to significant short-term improvement in terms of functional outcome and quality of life despite a high general complication rate.

Observational study of short-segment pedicle screw fixation for dorsolumbar spine injury: A prospective study

Background: Traumatic injury of dorsolumbar spine is one of the most common sites of spinal injuries because of its location between rigid kyphotic thoracic and mobile lordotic lumbar spine. Its treatment by pedicle screw fixation by short segment (one level above and below the fractured vertebra) or long segment (two levels above and below the fractured vertebra) has always remained a matter of debate. The aim of this study was to assess the functional outcome of short-segment fixation in dorsolumbar spine injury.Materials and Methods: This prospective study was conducted on thirty, single-level, unstable dorsolumbar spine fracture patients, who underwent short-segment pedicle screw instrumentation at Indira Gandhi Institute of Medical Sciences, Patna, between October 2019 and September 2021. All the patients were operated by posterior approach and stabilized the vertebrae with short-segment pedicle screw instrumentation. All patients were followed up for 1 year.Results: Thirty patients (21 males and 9 females) of mean age 34.2 ± 11.74 years were included in the study. The most common mode of injury was fall from height (24 patients, 80%), followed by road traffic accident (six patients, 20%). The most common fracture pattern was compression fractures in 23 (76.67%) patients, followed by burst fractures in 7 (23.33%) patients. The most common level of injury was L1, followed by D12. Neurological improvement of at least one level was seen in 21 patients, and nine patients had no neurological improvement. There was a statistically significant correction of kyphotic angle of 14.9°. At 1 year of follow-up, 21 (70%) patients had <40% Oswestry Disability Index (ODI) and 9 (30%) patients had more than 40% ODI. Out of 30 patients, 2 (6.67%) patients had bedsore, 1 (3.33%) patient had superficial infection, and 1 (3.33%) patient had implant failure.Conclusion: The short-segment posterior instrumentation system is a very stable construct. It maintained the corrected deformity after fracture reduction and spares the motion segment which is sacrificed in the conventional long-segment fixation. The soft tissue dissection, blood loss, and duration of surgery are less in this procedure.

Optimization of Spinal Reconstructions for Thoracolumbar Burst Fractures to Prevent Proximal Junctional Complications: A Finite Element Study.

The management strategies of thoracolumbar (TL) burst fractures include posterior, anterior, and combined approaches. However, the rigid constructs pose a risk of proximal junctional failure. In this study, we aim to systemically evaluate the biomechanical performance of different TL reconstruction constructs using finite element analysis. Furthermore, we investigate the motion and the stress on the proximal junctional level adjacent to the constructs. We used a T10-L3 finite element model and simulated L1 burst fracture. Reconstruction with posterior instrumentation (PI) alone (U2L2 and U1L1+(intermediate screw) and three-column spinal reconstruction (TCSR) constructs (U1L1+PMMA and U1L1+Cage) were compared. Long-segment PI resulted in greater global motion reduction compared to constructs with short-segment PI. TCSR constructs provided better stabilization in L1 compared to PI alone. Decreased intradiscal and intravertebral pressure in the proximal level were observed in U1L1+IS, U1L1+PMMA, and U1L1+Cage compared to U2L2. The stress and strain energy of the pedicle screws decreased when anterior reconstruction was performed in addition to PI. We showed that TCSR with anterior reconstruction and SSPI provided sufficient immobilization while offering additional advantages in the preservation of physiological motion, the decreased burden on the proximal junctional level, and lower risk of implant failure.

Radiological comparison of the biomechanical characteristics of short segment posterior instrumentation (Moss- Miami system), with and without transverse connector, in unstable thoraco-lumbar fracture

Introduction: Wedge compression fracture was most common type of fracture (66.6 %) and first Lumbar vertebra (L1) was the most common fracture site (38 %). The choice of surgical approach and instrumentation depends on fracture type, injury level and degree of neural injury. This paper evaluated efficacy of transpedicular screw fixation by Moss Miami instrumentation with transverse connector for surgical treatment in traumatic unstable thoraco-lumbar fractures.&#x0D; Materials and Method: Fifty-five cases were prospectively studied over three years. Comparison was done between two groups- Group 1 without transverse connector and Group 2 with transverse connector. Radiologically evaluation was done in both groups pre-operatively, tenth day, six weeks and six months interval. All X-rays were assessed by lateral and dynamic antero- posterior views for measuring kyphotic (cobb’s) angle and inter-rod angle.&#x0D; Results: In both groups post-operative Mean Cobb’s angle level were increased and remained same until 6months. Variation in Group 2 with transverse connector was slightly higher in initial period (i.e.) after 10 days and then it remains minimal from 6 weeks to 6 months. But in Group 1 without transverse connector the change in angle variation was minimal which worsen over 6 weeks and it continues to remain worse at 6 months, suggestive of parallelogram effect.&#x0D; Conclusion: Transverse connector does play role in preventing parallelogram effect of implants and provides additional stability to the construct. This is first study done in vivo which is done to study the role of transverse connector and evaluate any parallelogram effect in spinal instrumentation.&#x0D; Key words&#x0D; Transverse connector, Thoraco-lumbar fracture, parallelogram effect

Comparing porous tantalum fusion implants and iliac crest bone grafts for spondylodesis of thoracolumbar burst fractures: Prospectice Cohort study

The aim of this study was to compare two different techniques of performing one-level spondylodesis for thoracolumbar burst fractures using either an autologous iliac crest bone graft (ICBG) or a porous tantalum fusion implant (PTFI). In a prospective nonrandomized study, 44 patients (20 women, 24 men; average age 43.1 ± 13.2 years) suffering from severe thoracolumbar burst fractures were treated with combined anterior–posterior stabilization. An ICBG was used in 21 cases, and a PTFI was used in the other 23 cases. A two-year clinical and radiographic follow-up was carried out. There were no statistically significant differences in age, sex, localization/classification of the fracture, or visual analog scale (VAS) before injury between the two groups. All 44 patients were followed up for an average period of 533 days (range 173–1567). The sagittal spinal profile was restored by an average of 11.1° (ICBG) vs. 14.3° (PTFI) (monosegmental Cobb angle). Loss of correction until the last follow-up tended to be higher in the patients treated with ICBG than in those treated with PTFI (mean: 2.8° vs. 1.6°). Furthermore, significantly better restoration of the sagittal profile was obtained with the PTFI than with the iliac bone graft at the long-term follow-up (mean: ICBG 7.8°, PTFI 12.3°; p < 0.005). Short-segment posterior instrumentation combined with anterior one-level spondylodesis using either an ICBG or a PTFI resulted in sufficient correction of posttraumatic segmental kyphosis. PTFI might be a good alternative for autologous bone grafting and prevent donor site morbidities.

Outcomes of Thoracolumbar Fracture-Dislocation Managed by Short-Segment and Long-Segment Posterior Fixation: A Single-Center Retrospective Study.

Long-segment posterior fixation has been used as a mainstay treatment of spine fracture-dislocations. Studies using short-segment posterior fixation in cases of thoracolumbar fracture-dislocation are limited. We describe our experience of 26 patients with thoracolumbar fracture-dislocation treated by short-segment or long-segment posterior spinal fixation and fusion. This is a single-center retrospective study of 26 patients with thoracolumbar fracture-dislocation treated by long-segment (group 1, n = 12) and short-segment posterior instrumentation (group 2, n = 14). Clinical (visual analog scale [VAS], Oswestry Disability Index [ODI]), neurological (American Spinal Injury Association [ASIA] scale), radiological (kyphotic angle, translational percentage, and displacement angle), and surgical (blood loss, operative time) outcomes and complications were recorded with each method. The mean follow-up period was 8.64 months (6-20 months). The mean duration of surgery was 3.92 ± 0.67 hours in group 1 and 3.21 ± 0.54 hours in group 2, and mean blood loss was 583.33 ± 111.5 mL and 478.6 ±112.2 mL in groups 1 and 2, respectively (P < .05). There was no radiologically visible pseudarthrosis, implant failure, or screw breakage in either group at follow up with no statistically significant difference between the 2 groups with regard to the radiological outcome (P > .05). Two patients in group 1 and 6 patients in group 2 improved after surgery at least 1 ASIA grade. VAS and ODI improved in both groups at the final follow up. Short-segment fixation can be used for treating fracture-dislocation patients, as it results in less blood loss, decreased intraoperative time, and saves fusion segments with similar radiological and clinical outcomes as long-segment fixation. 3.

Evaluation of titanium release from titanium alloy implants in patients with spinal instrumentation.

ObjectiveThis study was performed to investigate the baseline serum titanium levels in patients with short-segment titanium alloy posterior instrumentation and to assess patient-, implant-, and surgery-related factors that might affect the serum titanium level.MethodTwo groups of patients were included in the study. The study group comprised 39 patients who had undergone short-segment posterior instrumentation from January 2013 to June 2016. The control group comprised 11 randomly selected patients who presented to the outpatient clinic with no history of orthopedic surgery. The serum titanium levels and inter-group differences were analyzed.ResultsThe mean serum titanium level was significantly higher in the study group than in the control group. No significant difference was observed between patients with different etiologies, implants used for fusion, numbers of instrumented segments, or postoperative durations.ConclusionThe serum titanium levels of patients with posterior lumbar spinal instrumentation are significantly higher than those of the normal population even after achievement of solid fusion. These levels are not affected by the use of transverse connectors, the use of cages, the operated segments, or the duration of implants.

Short Segment Posterior Instrumentation with Intermediate Screw in Thoracolumbar Junction Injury: Prospective Study

Short Segment Posterior Instrumentation with Intermediate Screw in Thoracolumbar Junction Injury: Prospective Study

The Stiffness Comparison of Four-Screw versus Six-Screw Short Segment Pedicle Posterior Stabilization Instrumentation in Cyclic Axial Compression

Background: Thoracolumbar burst fracture required to conduct short segment posterior stabilization as the operative therapy. The short segment fixation (above and under fracture level (four-screw pedicle)) encounters loss of correction and failure including progressive kyphosis, screw pedicles and rods that are bent or fractured. Rod around fracture site receives bigger loads than other parts due to its function as cantilever. To overcome this, it uses short-segment posterior stabilization instrumentation in which pedicle screw is installed above, under, and on fracture site level (six-screw pedicle) to increase stiffness.Objective: To analyze the comparison stiffness of four-screw versus six-crew short segment pedicle posterior stabilization instrumentation in cyclic axial compression.Method: This study used in vitro mechanical test in simulation of vertebrae from UHMWPE (Ultra High Molecular Weight Polyethilene) that was fixated with four-screw and six-screw pedicle. Each construction is given cyclic axial compression. Afterwards, the stiffness of each construction was measured.Results: Six-screw short segment pedicle posterior vertebrae stabilization instrumentation had higher stiffness of 43.38% than four-screw short segment pedicle posterior vertebrae stabilization instrumentation in cyclic axial compression. There was a significant difference in both groups (p<0.05)Conclusion: Six-screw short segment pedicle posterior vertebrae stabilization instrumentation was better than four-screw short segment pedicle posterior vertebrae stabilization instrumentation in cyclic axial compression

Short-Segment Instrumentation with Fractured Vertebrae Augmentation by Screws and Bone Substitute for Thoracolumbar Unstable Burst Fractures.

Background For thoracolumbar burst fractures, traditional four-screw (one above and one below) short-segment instrumentation is popular and has a high failure rate. Additional augmentation at the fractured vertebrae is believed to reduce surgical failure. The purpose of this study was to examine the clinical and radiographic results of patients who underwent short-segment posterior instrumentation with augmentation by screws and bone substitutes at the fractured vertebrae and to compare these data to those of patients who underwent long-segment instrumentation for thoracolumbar burst fractures. Methods The study group had twenty patients who underwent short-segment instrumentation with additional augmentation by two screws and bone substitutes at the fractured vertebrae. The control group contained twenty-two patients who underwent eight-screw long instrumentation without vertebra augmentation. Local kyphosis and the anterior body height of the fractured vertebrae were measured. The severity of the fractured vertebrae was evaluated with the load sharing classification (LSC). Any implant failure or loss of correction >10° at the final follow-up was defined as surgical failure. Results Both groups had similar distributions in terms of age, sex, the injured level, and the mechanism of injury before operation. During the operation, the study group had significantly less blood loss (136.0 vs. 363.6 ml, p=0.001) and required shorter operating times (146.8 vs. 157.5 minutes, p=0.112) than the control group. Immediately after surgery, the study group had better correction of the local kyphosis angle (13.4° vs. 11.9°, p=0.212) and restoration of the anterior height (34.7% vs. 31.0%, p=0.326) than the control group. At the final follow-up, no patients in the study group and only one patient in the control group experienced surgical failure. Conclusions Patients with thoracolumbar burst fractures who received six-screw short-segment posterior fixators with augmentation at the level of the fractured vertebrae via injectable artificial bone substitute achieved satisfactory clinical and radiographic results, and this method could replace long-segment instrumentation methods used in unstable thoracolumbar burst fractures.

Effect of loss of correction on functional outcomes in thoracolumbar burst fractures treated with short segment posterior instrumentation

Aim: Burst fractures are defined as vertebra fractures involving the anterior and middle columns and are associated with kyphotic deformity and retropulsion of bone fragment into the spinal canal. Although their treatment is controversial in the literature, use of transpedicular screws and short segment posterior instrumentation are increasingly common practices. The aim of this study is to investigate the radiological and functional outcomes of thoracolumbar vertebra burst fractures treated with short segment posterior instrumentation and to examine the effects of postoperative correction loss on these results.Methods: Patients who were surgically treated for thoracolumbar burst fractures and prospectively followed-up between 2000-2003 were scanned retrospectively for this cohort study. 48 patients were included in the study, of which 18 were females (37.5%) and 30 were males (62.5%). Denis Pain Scale (DPS) and Denis Work Scale (DWS) were used for functional analysis. Cobb angles that were measured preoperatively, on the first postoperative day, and at the last follow-up visit were used for evaluation of radiological outcomes. Spinal stenosis and remodelization rates were also calculated by computerized tomography obtained preoperatively and at the last follow-up. One-way ANOVA and Pearson correlation tests were used for statistical analysis.Results: No patient had any chronic pain complaints, and none were unable to work. The mean Cobb angles in the preoperative, early post-operative and final controls were measured as 23.2, 4.9, and 12.3 degrees, respectively. While preoperative mean Cobb angle and mean correction were positively correlated (r=0.85, P&lt;0.001), there was no correlation between preoperative mean Cobb angle and loss of correction (r=0.27, P=0.43). There was a correlation between correction and loss of correction (r=0.38, P=0.008). Spinal stenosis, which was 35.7% preoperatively, reduced to 17.1% in the last follow-up. The mean remodelization was 51.3%, which was significant (P&lt;0.001). Loss of correction was found significant in patients with poor DWS (P=0.003), and no such relationship was found in DPS. No correlation was found between the Cobb angle at the last follow-up, DPS and DWS. Conclusion: In conclusion, the loss of correction after short segment posterior instrumentation and fusion surgery is significantly higher in thoracolumbar burst fractures, especially when intraoperative correction exceeds 15 degrees. Denis Work Scale was significantly worse in patients with loss of correction above 10 degrees. The degree of loss of correction at the last follow-up is directly related to clinical and functional outcomes.

Finite element analysis comparing short-segment instrumentation with conventional pedicle screws and the Schanz pedicle screw in lumbar 1 fractures.

Previous finite element studies of thoracolumbar fractures were mostly based on simulation analysis of one single object, which was difficult to objectively evaluate the differences between conventional pedicle screws and Schanz pedicle screws. The aim of this study was to evaluate the stress of screw and injured vertebrae displacement using the finite element model of conventional pedicle screw and Schanz pedicle screw instrumentation for the treatment of lumbar 1 fractures. Data of eight healthy volunteers were used to simulate the finite element model. The instrumentation models were divided into four groups: moderate fracture conventional (MC), moderate fracture Schanz (MS), unstable/severe fracture conventional (UC), and unstable/severe fracture Schanz (US) pedicle screw groups. The maximum screw stress and lumbar 1 displacement/micro-motion in each group increased with the increase of torque and/or load. Under the same fracture, maximum von Mises stress of conventional pedicle screw (MC/UC) was larger than Schanz pedicle screw (MS/US) (P < 0.05) and lumbar 1 displacement/micro-motion of Schanz pedicle screw (MS/US) was larger than conventional pedicle screw (MC/UC) (P < 0.05). Under the same screws, the maximum von Mises stress and displacement/micro-motion of unstable fracture (UC/US) were larger than moderate fracture (MC/MS) (P < 0.05). Posterior short-segment instrumentation with Schanz pedicle screws were recommended for unstable fractures. The compression displacement/micro-motion of bony defect during flexion may lead to the postoperative re-collapse of injured vertebrae.

The Predictive Value of the Load Sharing Classification Concerning Sagittal Collapse and Posterior Instrumentation Failure: A Systematic Literature Review.

Study design:Systematic review.Objective:In 1994, the Load Sharing Classification (LSC) was introduced to aid the choice of surgical treatment of thoracolumbar spine fractures. Since that time this classification system has been commonly used in the field of spine surgery. However, current literature varies regarding its use and predictive value in relation to implant failure and sagittal collapse. The objective of this study is to assess the predictive value of the LSC concerning the need for anterior stabilization to prevent sagittal collapse and posterior instrumentation failure.Methods:An electronic search of PubMed, Medline, Embase, and the Cochrane Library was performed. Inclusion criteria were (1) cohort or clinical trial (2) including patients with thoracolumbar burst fractures (3) whose severity of the fractured vertebrae was assessed by the LSC.Results:Five thousand eighty-two articles have been identified, of which 21 articles were included for this review. Twelve studies reported no correlation between the LSC and sagittal collapse or instrumentation failure in patients treated with short-segment posterior instrumentation (SSPI). Seven articles found no significant relation; 5 articles found no instrumentation failure at all. The remaining 9 articles experienced failure in patients with a high LSC or recommended a different surgical technique.Conclusions:Although the LSC was originally developed to predict the need for anterior stabilization in addition to SSPI, many studies show that SSPI only can be sufficient in treating thoracolumbar fractures regardless of the LSC. The LSC might have lost its value in predicting sagittal collapse and posterior instrumentation failure.

The biomechanical effect of single-level laminectomy and posterior instrumentation on spinal stability in degenerative lumbar scoliosis: a human cadaveric study.

OBJECTIVEDegenerative lumbar scoliosis, or de novo degenerative lumbar scoliosis, can result in spinal canal stenosis, which is often accompanied by disabling symptoms. When surgically treated, a single-level laminectomy is performed and short-segment posterior instrumentation is placed to restore stability. However, the effects of laminectomy on spinal stability and the necessity of placing posterior instrumentation are unknown. Therefore, the aim of this study was to assess the stability of lumbar spines with degenerative scoliosis, characterized by the range of motion (ROM) and neutral zone (NZ) stiffness, after laminectomy and placement of posterior instrumentation.METHODSTen lumbar cadaveric spines (T12-L5) with a Cobb angle ≥ 10° and an apex on L3 were included. Three loading cycles were applied per direction, from -4 Nm to 4 Nm in flexion/extension (FE), lateral bending (LB), and axial rotation (AR). Biomechanical evaluation was performed on the native spines and after subsequent L3 laminectomy and the placement of posterior L2-4 titanium rods and pedicle screws. Nonparametric and parametric tests were used to analyze the effects of laminectomy and posterior instrumentation on NZ stiffness and ROM, respectively, both on an individual segment's motion and on the entire spine section. Spearman's rank correlation coefficient was used to study the correlation between disc degeneration and spinal stability.RESULTSThe laminectomy increased ROM by 9.5% in FE (p = 0.04) and 4.6% in LB (p = 0.01). For NZ stiffness, the laminectomy produced no significant effects. Posterior instrumentation resulted in a decrease in ROM in all loading directions (-22.2%, -24.4%, and -17.6% for FE, LB, and AR, respectively; all p < 0.05) and an increase in NZ stiffness (+44.7%, +51.7%, and +35.2% for FE, LB, and AR, respectively; all p < 0.05). The same changes were seen in the individual segments around the apex, while the adjacent, untreated segments were mostly unaffected. Intervertebral disc degeneration was found to be positively correlated to decreased ROM and increased NZ stiffness.CONCLUSIONSLaminectomy in lumbar spines with degenerative scoliosis did not result in severe spinal instability, whereas posterior instrumentation resulted in a rigid construct. Also, prior to surgery, the spines already had lower ROM and higher NZ stiffness in comparison to values shown in earlier studies on nonscoliotic spines of the same age. Hence, the authors question the clinical need for posterior instrumentation to avoid instability.

Results of short segment posterior fixation in AO type C fracture of dorsolumbar spine

Introduction: Spinal traumas are common and leading problem in orthopaedics practice. The individuals are at a risk of high energy trauma in modern era. Unstable thoraco-lumbar burst fractures are serious injuries of concern, if left untreated may result in marked morbidity and disability to the patient. Thoracolumbar is the second most common segment involved in the vertebral column following cervical segment in patients with spinal injuries. Historically, the thoracolumbar fractures were treated by recumbency (bed rest for a period of 8-12 weeks). In a resource scarce country like India, the care is often neglected to the victims. So, it is the need of the hour to explore possibility of surgical stabilization, early mobilization and rehabilitation of patients. In this study, we stabilized the patients with unstable thoracolumbar burst fractures with short segment posterior instrumentation with transpedicular screws.Aim: To study efficacy of short segment posterior instrumentation in achieving stabilization of thoracic and lumbar fractures of spine.Materials and Methods: This was a prospective interventional study undertaken in the Department of Orthopedics, New Civil Hospital, Ahmedabad. 32 Adult patients with acute thoracolumbar injury admitted to Civil Hospital, AHMEDABAD were included in this study after obtaining their valid, written informed consent. Plain x-rays in anterio-posterior and lateral views were obtained and the instability of spine was confirmed using Thoraco-Lumbar Injury Classification and Severity Score. All patients underwent short segment posterior Fixation and were followed up in OPD every 4th week after surgery till 6 months and for each follow up, neurological, radiological and clinical examinations were done to assess the spinal stability.Results and Discussion: All fractures were classified as Type C fractures according to the AO classification system. Intermediate screw was inserted in 21 patients out of 32. This study showed that fracture level screw fixation technique could achieve and maintain correction, regional angle and vertebral height. We have used the intermediate screw option in the fractured vertebra level as a method of augmentation in the current study. The results were comparable to other studies in the past.Conclusion: The findings of these study show that short segment posterior instrumentation is an excellent implant system used in the treatment of vertebral fractures. There is a very high statistically significant restoration of vertebral body height, mean regional angle and mean anterior wedge angle.

Comparison of Four Different Posterior Screw Fixation Techniques for the Treatment of Thoracolumbar Junction Fractures

The purpose of this study was to compare clinical and radiologic outcomes of patients who underwent short-segment posterior instrumentation with screw augmentation at the fracture level and long-segment instrumentation for thoracolumbar junction fractures. Sixty-three patients were retrospectively evaluated by being divided into the following 4 groups: Groups A, B, C, and D included patients who had undergone 4-level instrumentation without insertion of screws at the fracture level, 3-level instrumentation by insertion of screws at the fracture level, 4-level instrumentation by insertion of screws at the fracture level, and 5-level instrumentation by insertion of screws at the fracture level, respectively. No significant difference was observed in preoperative local kyphosis angle (LKA) (P > 0.05), whereas there was a significant decrease in early postoperative LKA in Group C compared with the other groups (P < 0.05). However, there was no significant difference of LKA in the 4 groups measured on radiographs obtained at the final follow-up (P > 0.05). Anterior corpus height loss, Cobb angle of the fractured vertebra, and sagittal index, measured pre- and postoperatively and at the final follow-up, showed no significant difference (P > 0.05). There was no statistically significant difference between clinical scores of the 4 groups (P > 0.05). Short-segment posterior instrumentation with screw augmentation at the fracture level provides at least as much mechanical stability as long-segment instrumentation. Moreover, there is no difference between short-segment instrumentation with screw augmentation at the fracture level and long-segment instrumentation in terms of clinical outcomes.

Modified Posterior Short-Segment Pedicle Screw Instrumentation for Lumbar Burst Fractures with Incomplete Neurological Deficit

We have introduced a method of modified posterior short-segment pedicle screw fixation and evaluated its clinical effects in treating lumbar burst fractures with incomplete neurological deficits. The data from 22 patients with lumbar burst fracture and incomplete neurological deficits who had undergone modified posterior short-segment instrumentation with Schanz screw fixation from January 2012 to February 2018 in our clinic were evaluated in the present retrospective study. All Schanz screws were implanted in an oblique downward direction into the vertebrae above and below the injured vertebra (insertion depth, 90%-100%). The implants were removed ∼1 year after surgery. Neurological function, back pain, anterior and posterior body height ratio, kyphosis angle, percentage of canal compromise, fracture severity, and treatment-related complications were evaluated. Technical success was achieved in all 22 patients. No infection, instrument loosening or failure, or breakage was observed. Statistically significant improvements with regard to the anterior body height (P < 0.05) and posterior body height (P < 0.05) ratios, kyphosis angle, and percentage of canal compromise (P < 0.05) were observed at 1 week postoperatively or the final follow-up visit. No correction loss had occurred at the final follow-up examination. Postoperatively, all patients with neurological deficits had functional improvement equivalent to ≥1 grade on the American Spinal Injury Association impairment scale and fracture union. Back pain was greatly improved postoperatively. Short-segment Schanz screw fixation implanted in an oblique downward direction seems to be a promising method for lumbar burst fractures with incomplete neurological deficits because it provided good clinical and radiographic outcomes.