Analysis of sagittal lumbar alignment before and after posterior instrumentation: Risk factor for adjacent unfused segment

Correlation between thoracolumbar disc degeneration and anatomical spinopelvic parameters in supine position on MRI

Objective

This study aims to investigate the correlation between spinopelvic parameters in supine position (pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL)), disc degeneration and herniation of the thoracolumbar spine, as well as cardiovascular risk factors and back pain in a southern German cohort from the general population.

Methods

This study is a cross-sectional, case–control study drawn from a prospective cohort of the “Cooperative Health Research in the Region of Augsburg/Kooperative Gesundheitsforschung in der Region Augsburg” study (KORA). In total, 374 participants (mean age 56.4 ± 9.2 years; 57.8% male) from the whole-body MRI cohort (FF4) were included. All participants underwent a standardized whole-body MRI on which disc degeneration of the thoracic and lumbar spine was evaluated using a sequence adapted Pfirrmann score. PI, PT, SS and LL were measured according to the description in the literature, using sagittal imaging. Furthermore, disc bulging and protrusion were assessed. Correlations were estimated by logistic regression models providing odds ratios.

Results

Mean PI was 54.0° ± 11.1°, PT 13.0° ± 5.8°, SS 40.2° ± 8.8° and LL 36.2° ± 9.6°. SS was greater in men (p<0.05) and lumbar lordosis in women (p<0.001). PT increased by 0.09° per age-year with rising age. Age was not associated with PI, SS and LL. Neither BMI, hypertension, cholesterol, lipid levels, nor physical activity were associated with PI, PT, SS or LL. Diabetes mellitus negatively correlated with SS (β = -4.19; 95%CI -7.31–1.06, p<0.01). Smaller spinopelvic parameters (PI, SS and LL) where significantly (p<0.05) correlated with an increased frequency of disc bulging, as well as a local clustering in the lumbar, but not the thoracic spine.

Conclusion

In conclusion, spinopelvic parameters, measured in supine position, are significantly correlated with disc bulging alone; there is no significant correlation between supine spinopelvic parameters and disc degeneration, back pain or cardiovascular risk factors.

Spinal sagittal alignment goals based on statistical modelling and musculoskeletal simulations

The definition of target alignment for spinal fusion surgery follows anatomical criteria and strongly relies on surgical experience. However, the optimal patient-specific alignment often remains unknown. Statistical models could provide information about physiological alignments, and musculoskeletal models are powerful tools to investigate biomechanics. We aimed to statistically predict alignments and hypothesized they would be biomechanically favorable. A statistical model was trained with 60 annotated radiographs to predict physiological sagittal alignment based on position of femoral heads and sacrum. Predicted alignments for 11 back pain patients were clinically evaluated in terms of balance and compared to Original alignments. The normative ranges for spinal balance parameters were obtained from Surgimap™. Musculoskeletal loads were furthermore simulated in upright standing and 30° forward flexion, using alignment-specific musculoskeletal models. For the majority of Predicted alignments (n = 9) at least two of three investigated balance parameters were within the normative range, as opposed to the minority of the Original alignments (n = 4). Predicted alignments resulted in significantly lowered overall muscle activity and compressive loads (all levels, both postures). Shear force magnitudes in upright standing decreased significantly at levels L1L2 (-68 N) and L2L3 (-69 N) and clearly yet not significantly at L3L4 (-39 N) and L4L5 (-152 N). Shear loads at level L5S1 remained the same. In flexed postures identical trends were observed. The statistical model was able to predict spinal alignments that led to both improved balance and reduced musculoskeletal loads. Further studies are needed to investigate clinical validity of such models.

How Does Cage Lordosis Influence Postoperative Segmental Lordosis in Lumbar Interbody Fusion

BACKGROUND

Consideration of sagittal alignment is an integral part of spinal fusion surgery correlating with superior outcomes. Segmental lordosis is an important contributor to sagittal alignment. This study assessed surgical factors influencing segmental lordosis in a 360° fusion model, including cage dimensions, anterior longitudinal ligament resection, facetectomy, and posterior compression.

METHODS

Six L3-4 synthetic spinal motion segments were used in a repeated measures design. Each sample was sequentially instrumented with lateral cages of increasing height and angle. Lordosis was assessed from lateral radiographs of intact and each instrumented condition. The effect of anterior longitudinal ligament resection, posterior compression with pedicle screws, and bilateral facetectomy was additionally examined.

RESULTS

A linear relationship between segmental lordosis and cage height was found. This effect was greater with the anterior longitudinal ligament divided. In cages of the same anterior height, increased intrinsic cage lordosis did not result in increased segmental lordosis; cages with no intrinsic lordosis resulted in the highest segmental lordosis. In examining this finding, it was shown that posterior cage height had a larger influence on segmental lordosis. Posterior compression with pedicle screws and bilateral facetectomy increased the segmental lordosis by a further 3.4° and 2.6°, respectively.

CONCLUSIONS

Cage height was a key factor, with posterior compression further increasing lordosis. The finding that 0° cages results in the most segmental lordosis was an unexpected finding and highlights the importance of appropriate sizing on resulting lordosis. These findings are relevant to cage selection but require further study prior to applying to clinical practice and may influence future cage design.

Does Preserving or Restoring Lumbar Lordosis Have an Impact on Functional Outcomes in Tuberculosis of the Lumbosacral Region?

STUDY DESIGN

Single-center retrospective cohort analysis.

OBJECTIVES

To analyze the impact of loss of global lumbar lordosis (GLL) on functional outcomes in tuberculosis of the lumbar and lumbosacral spine and to define strategies to restore or preserve the physiological lumbar lordosis.

SUMMARY OF BACKGROUND DATA

In tuberculosis of lumbosacral spine, loss of lumbar lordosis (LL) leads to altered lumbosacral biomechanics. All available studies have assessed treatment outcomes with respect to physical well-being, neurologic improvement, bone healing, and changes in radiologic parameters. None have studied the correlation between functional outcomes and LL following treatment. We reviewed 63 patients with tuberculosis of lumbar and lumbosacral spine, with an attempt to analyze the impact of loss of GLL on functional outcomes and have defined strategies to restore the same.

METHODS

We retrospectively reviewed 63 patients with lumbar and lumbosacral tuberculosis, treated conservatively (n = 33) or surgically (n = 30) from March 2007 to July 2013. Average follow-up was 43.1±7.2 months. The correlation between posttreatment GLL and the functional outcome (Oswestry Disability Index), measured at 36 months' follow-up, was analyzed.

RESULTS

All patients showed good bone healing (at 8.4±1.5 months), significant improvement in neurology, VAS scores, ESR and CRP, p<0.001. Mean loss of GLL in the conservatively treated group was 6.4°±5.7°, whereas there was an average gain of 10.9°±9.9° of GLL with surgery. In all patients with minimal disability at the end of treatment, the final GLL was above 40°. In patients with severe disability and in a few with moderate disability, the posttreatment GLL was below 40°. Pearson's test showed a strong negative correlation between final posttreatment GLL and the degree of disability (r = -0.867, p<0.001).

CONCLUSIONS

Early disease with minimal loss of lordosis can be managed conservatively, whereas in advanced disease with gross hypolordosis/kyphosis, posterior stabilization with or without global spinal reconstruction is essential to regain LL. The management of lumbosacral tuberculosis should aim at preserving or restoring the normal LL to achieve good functional outcomes.

LEVEL OF EVIDENCE

Level III.

The Sagittal Balance Does not Influence the 1 Year Clinical Outcome of Patients With Lumbar Spinal Stenosis Without Obvious Instability After Microsurgical Decompression

STUDY DESIGN

A retrospective study with retrospective and prospective inclusion of 100 patients.

OBJECTIVE

To determine whether the sagittal balance (SB) influences the clinical outcome of patients with degenerative lumbar spinal stenosis, who underwent microsurgical decompression.

SUMMARY OF BACKGROUND DATA

The SB has become a critical factor for clinical decision making in the surgical treatment of spinal degenerative diseases. However, a frequently recommended sagittal realignment of elderly, multimorbid patients is accompanied by a significant rate of complications. The influence of SB on the clinical outcome of patients with degenerative spinal stenosis, who undergo decompressive surgery is not well understood. The aim of this study was to explore whether the clinical outcome of these patients is related to the SB and whether patients with spinal stenosis and degenerative sagittal imbalance necessitate restoration of the SB in addition to microsurgical decompression.

METHODS

One hundred patients with lumbar spinal stenosis, who received microsurgical decompression, were retrospectively identified and classified according to the severity of sagittal imbalance: (1) normal balance group, (2) minor loss of balance group, and (3) major loss of balance group. Sagittal parameters were determined from preoperative lateral spinal radiographs. As outcome parameters, we analyzed pre- and postoperative visual analogue scales for leg and back pain, walking distance, Oswestry disability index, Roland and Morris disability questionnaire, Odom's criteria, and the SF-36 score.

RESULTS

All groups significantly benefited from surgery concerning leg pain, back pain, and disability in every day's life. There was no difference in patients with decompensated sagittal imbalance compared to patients with normal SB regarding life quality 6 to 24 months after microsurgical decompression.

CONCLUSIONS

Patients with symptomatic degenerative spinal stenosis and excluded major instability significantly benefit from microsurgical decompression regardless of their sagittal spinal balance. Thus, restoration of the SB for patients with symptomatic degenerative spinal stenosis cannot be recommended in addition to microsurgical decompression.

LEVEL OF EVIDENCE

3.

Sagittal balance, a useful tool for neurosurgeons?

New instrumentation techniques have made any correction of the spinal architecture possible. Sagittal balance has been described as an important parameter for assessing spinal deformity in the early 1970s, but over the last decade its importance has grown with the published results in terms of overall quality of life and fusion rate. Up until now, most of the studies have concentrated on spinal deformity surgery, but its use in the daily neurosurgery practice remains uncertain and may warrant further studies.

Compensatory mechanisms contributing to keep the sagittal balance of the spine

INTRODUCTION

Aging spine is characterized by facet joints arthritis, degenerative disc disease, bone remodeling and atrophy of extensor muscles resulting in a progressive kyphosis of the lumbar spine.

OBJECTIVE

The aim of this paper is to describe the different compensatory mechanisms for patients with severe degenerative lumbar spine.

MATERIAL AND METHODS

According to the severity of the imbalance, three stages are observed: balanced, balanced with compensatory mechanisms and imbalanced. For the two last stages, the compensatory mechanisms permit to limit the consequences of loss of lumbar lordosis on global sagittal alignment and therefore contribute to keep the sagittal balance of the spine.

RESULTS

The basic concept is to extend adjacent segments of the kyphotic spine allowing for compensation of the sagittal unbalance but potentially inducing adverse effects.

CONCLUSION

Finally, we propose a three-step algorithm to analyze the global balance status and take into consideration the presence of the compensatory mechanisms in the spinal, pelvic and lower limb areas.

Avaliação dos parâmetros espinopélvicos pelo posicionamento intra-operatório na artrodese de coluna lombo-sacra

OBJETIVO: Avaliar a relação dos parâmetros espinopélvicos pré-operatório, intra-operatório, pós-operatório e a influência do posicionamento cirúrgico com esses valores. MÉTODOS: Estudo retrospectivo, avaliando imagens radiográficas pré, intra e pós-operatória de pacientes que foram submetidos a artrodese de coluna lombossacral. RESULTADOS: Dos 16 pacientes avaliados observou-se que houve uma diminuição da inclinação sacral entre os momentos pré e pós-operatórios com uma influência direta sobre os valores da lordose lombar, com a consequente redução angular. CONCLUSÃO: Existe variação da inclinação sacral em função do posicionamento na mesa de cirurgia, principalmente entre o momento pré e intra-operatório posicionado, durante a cirurgia de fusão da coluna lombossacra e a inclinação sacral é responsável diretamente pela variação da lordose lombar

Correlation between symptoms and sagittal alignment parameters in patients with lumbar canal stenosis: a case-control study

OBJECTIVE: To examine the relationship between sagittal balance parameters and different symptoms of spinal disease in patients with lumbar canal stenosis (LCS) and controls. METHODS: In this prospective, diagnostic, case-control study, we included all patients consecutively admitted to a public teaching hospital for surgical treatment of LCS between July 2010 and October 2011, aged more than 40 years, with back pain plus radiculopathy or neurogenic claudication, and controls without LCS. Magnetic resonance and x-rays allowed the measurement of sagittal axis parameters. Clinical data, the Oswestry Disability Index and the visual analogue scale of pain were assessed. RESULTS: 23 patients were in the Stenosis group, and 17 were controls. The Stenosis group presented lower values of total lumbopelvic lordosis and regional lordosis L1, L2 and L3. In LCS patients and back pain, total lumbopelvic and regional lordosis at L1, L2 and L3 were smaller. Those with stenosis and radiculopathy had higher values of pelvic tilt and lower total lumbopelvic lordosis and regional lordosis in L1 and L2. In patients with claudication, regional lumbopelvic lordosis in L1 and L2 and the T9 sagittal offset were smaller. All patients with pain had higher values of thoracic kyphosis, regional lumbopelvic lordosis in L1, lower values for pelvic tilt, sagittal T1 offset, sacro-femoral distance and overhang compared to patients without pain. CONCLUSIONS: This study shows significant correlations between symptoms and sagittal axis parameters between patients with and without spinal canal stenosis and also in subgroups of the patients with stenosis with different complaints.

Sagittal balance disorders in severe degenerative spine. Can we identify the compensatory mechanisms?

INTRODUCTION

Aging of the spine is characterized by facet joints arthritis, degenerative disc disease and atrophy of extensor muscles resulting in a progressive kyphosis. Recent studies confirmed that patients with lumbar degenerative disease were characterized by an anterior sagittal imbalance, a loss of lumbar lordosis and an increase of pelvis tilt. The aim of this paper was thus to describe the different compensatory mechanisms which are observed in the spine, pelvis and/or lower limbs areas for patients with severe degenerative spine.

METHODS

We reviewed all the compensatory mechanisms of sagittal unbalance described in the literature.

RESULTS

According to the severity of the imbalance, we could identify three different stages: balanced, balanced with compensatory mechanisms and imbalanced. For the two last stages, the compensatory mechanisms permitted to limit consequences of lumbar kyphosis on the global sagittal alignment. Reduction of thoracic kyphosis, intervertebral hyperextension, retrolisthesis, pelvis backtilt, knee flessum and ankle extension were the main mechanisms described in the literature. The basic concept of these compensatory mechanisms was to extend adjacent segments of the kyphotic spine allowing for compensation of anterior translation of the axis of gravity.

CONCLUSIONS

To avoid underestimate the severity of the degenerative spine disorder, it thus seems important to recognize the different compensatory mechanisms from the upper part of the trunk to the lower limbs. We propose a three steps algorithm to analyse the balance status and determine the presence or not of these compensatory mechanisms: measurement of pelvis incidence, assessment of global sagittal alignment and analysis of compensatory mechanisms successively in the spine, pelvis and lower limbs areas.

Geometry of the vertebral bodies and the intervertebral discs in lumbar segments adjacent to spondylolysis and spondylolisthesis: pilot study

The objective is to evaluate the geometric parameters of vertebral bodies and intervertebral discs in spinal segments adjacent to spondylolysis and spondylolisthesis. This pilot cross-sectional study was an ancillary project to the Framingham Heart Study. The presence of spondylolysis and spondylolisthesis as well as measurements of spinal geometry were identified on CT imaging of 188 individuals. Spinal geometry measurements included lordosis angle, wedging of each lumbar vertebra and intervertebral disc. Last measurements were used to calculate ΣB, the sum of the lumbar L1-L5 body wedge angles; and ΣD, the sum of the lumbar L1-L5 intervertebral disc angles. Using Wilcoxon-Mann-Whitney test we compared the geometric parameters between individuals with no pathology and ones with spondylolysis (with no listhesis) at L5 vertebra, ones with isthmic spondylolisthesis at L5-S1 level, and ones with degenerative spondylolisthesis at L5-S1 level. Spinal geometry in individuals with spondylolysis or listhesis at L5 shows three major patterns: In spondylolysis without listhesis, spinal morphology is similar to that of healthy individuals; In isthmic spondylolisthesis there is high lordosis angle, high L5 vertebral body wedging and very high L4-5 disc wedging; In degenerative spondylolisthesis, spinal morphology shows more lordotic wedging of the L5 vertebral body, and less lordotic wedging of intervertebral discs. In conclusion, there are unique geometrical features of the vertebrae and discs in spondylolysis or listhesis. These findings need to be reproduced in larger scale study.

Spinopelvic alignment of patients with degenerative spondylolisthesis

OBJECTIVE

The main objectives of this study were to analyze and compare spinopelvic parameters, including the pelvis shape, in a population of 40 patients with degenerative spondylolisthesis (DSPL) and to compare these patients with a control group of asymptomatic volunteers.

METHODS

Forty patients with DSPL were included in this study. Spinopelvic parameters were analyzed on preoperative full spine x-rays in a standardized standing position. The following spinopelvic parameters were measured: pelvic incidence (PI), sacral slope, pelvic tilt, lumbar lordosis, thoracic kyphosis, and positioning of the C7 plumb line. The population of patients was compared with a control population of 154 normal and asymptomatic adults who were studied in a recently published study. In order to understand variations of spinopelvic parameters, a control group was matched according to the PI, which is a morphological parameter.

RESULTS

The PI was significantly greater for patients with DSPL (60.1 +/- 10.6 degrees) compared with the control group (52 +/- 10.7 degrees) (P < 0.0005). After matching according to the pelvic incidence, the DSPL population was characterized by an anterior translation of the C7 plumb line (P < 0.05), a loss of lumbar lordosis (P < 0.0005), and a decrease of the sacral slope (P < 0.0005). Retrolisthesis and/or segmental intervertebral hyperextension were observed in the upper lumbar spine in 30% of the cases.

CONCLUSION

Matching according to the PI between the patients in the study and the control group enabled us to understand variations of the spinopelvic parameters in a population of patients with DSPL. DSPL patients were characterized by a greater PI than the asymptomatic population; therefore, we suggest that a high PI may be a predisposing factor in developing DSPL. Finally, we observed significant variations in spinopelvic alignment, such as loss of lordosis and sagittal unbalance, which were partially compensated by pelvis back tilt and hyperextension in the upper lumbar spine.

Sagittal balance of the pelvis-spine complex and lumbar degenerative diseases. A comparative study about 85 cases

Retrospective analysis of the spino-pelvic alignment in a population of 85 patients with a lumbar degenerative disease. Several previous publications reported the analysis of spino-pelvic alignment in the normal and low back pain population. Data suggested that patients with lumbar diseases have variations of sagittal alignment such as less distal lordosis, more proximal lumbar lordosis and a more vertical sacrum. Nevertheless most of these variations have been reported without reference to the pelvis shape which is well-known to strongly influence spino-pelvic alignment. The objective of this study was to analyse spino-pelvic parameters, including pelvis shape, in a population of 85 patients with a lumbar degenerative disease and compare these patients with a control group of normal volunteers. We analysed three different lumbar degenerative diseases: disc herniation (DH), n = 25; degenerative disc disease (DDD), n = 32; degenerative spondylolisthesis (DSPL), n = 28. Spino-pelvic alignment was analysed pre-operatively on full spine radiographs. Spino-pelvic parameters were measured as following: pelvic incidence, sacral slope, pelvic tilt, lumbar lordosis, thoracic kyphosis, spino-sacral angle and positioning of C7 plumb line. For each group of patients the sagittal profile was compared with a control population of 154 asymptomatic adults that was the subject of a previous study. In order to understand variations of spino-pelvic parameters in the patients' population a stratification (matching) according to the pelvic incidence was done between the control group and each group of patients. Concerning first the pelvis shape, patients with DH and those with DDD demonstrated to have a mean pelvic incidence equal to 49.8 degrees and 51.6 degrees, respectively, versus 52 degrees for the control group (no significant difference). Only young patients, less than 45 years old, with a disc disease (DH or DDD) demonstrated to have a pelvic incidence significantly lower (48.3 degrees) than the control group, P < 0.05. On the contrary, in the DSPL group the pelvic incidence was significantly greater (60 degrees) than the control group (52 degrees), P < 0.0005. Secondly the three groups of patients were characterized by significant variations in spino-pelvic alignment: anterior translation of the C7 plumb line (P < 0.005 for DH, P < 0.05 for DDD and P < 0.05 for DSPL); loss of lumbar lordosis after matching according to pelvic incidence (P < 0.0005 for DH, DDD and DSPL); decrease of sacral slope after matching according to pelvic incidence (P = 0.001 for DH, P < 0.0005 for DDD and P < 0.0005 for DSPL). Measurement of the pelvic incidence and matching according to this parameter between each group of patients and the control group permitted to understand variations of spino-pelvic parameters in a population of patients.

Rigid, semirigid versus dynamic instrumentation for degenerative lumbar spinal stenosis: a correlative radiological and clinical analysis of short-term results

STUDY DESIGN

Prospective comparative randomized clinical and radiologic study.

OBJECTIVE

This study was conducted to compare the short-term effects of rigid versus semirigid and dynamic instrumentation on the global and segmental lumbar spine profile, subjective evaluation of the result, and the associated complications.

BACKGROUND DATA

Lumbar spine fusion with rigid instrumentation for degenerative spinal disorders seems to increase the fusion rate. However, rigid instrumentation may be associated with some undesirable effects, such as increased low back pain following decrease of lumbar lordosis, fracture of the vertebral body and pedicle, pedicle screw loosening, and adjacent segment degeneration. The use of semirigid and dynamic devices has been advocated to reduce such adverse effects of the rigid instrumentation and thus to achieve a more physiologic bony fusion.

MATERIALS AND METHODS

This study compared 3 equal groups of 45 adult patients, who underwent primary decompression and stabilization for symptomatic degenerative lumbar spinal stenosis. The patients of each group were randomly selected and received either the rigid (Group A), or semirigid (Group B), or dynamic (Group C) spinal instrumentation with formal decompression and fusion. The mean ages of the patients who received rigid, semirigid, and dynamic instrumentation were 65 +/- 9, 59 +/- 16, and 62 +/- 10 years, respectively. All patients had detailed roentgenographic study including computed tomography scan and magnetic resonance imaging before surgery to the latest follow-up observation. The following roentgenographic parameters were measured and compared in all spines: lumbar lordosis (L1-S1), total lumbar lordosis (T12-S1), sacral tilt, distal lordosis (L4-S1), segmental lordosis, vertebral inclination, and disc index. The SF-36 health survey and Visual Analogue Scale was used before surgery to the latest evaluation.

RESULTS

All patients were evaluated after a mean follow-up of 47 +/- 14 months. Both lumbar and total lordosis correction did not correlate with the number of the levels instrumented in any group. Total lordosis was slightly decreased after surgery (3%, P < 0.05) in Group C. The segmentallordosis L2-L3 was increased after surgery by 8.5% (P < 0.05) in Group C, whereas the segmentallordosis L4-L5 was significantly decreased in Group Aand C by 9.8% (P = 0.01) and 16.2% (P < 0.01), respectively. The disc index L2-L3 was decreased after surgery in Group A and C by 17% (P < 0.05) and 23.5% (P < 0.05), respectively. The disc index L3-L4 was increased in Group C by 18.74% (P < 0.01). The disc index L4-L5 was after surgery decreased in all 3 groups: Group A by 21% (P = 0.01), Group B by 13% (P < 0.05), and Group C by 13.23% (P < 0.05). The disc index L5-S1 was significantly decreased in Group B by 13% (P < 0.05). The mean preoperative scores of the SF-36 before surgery were 11, 14, and 13 for Groups C, B, and A, respectively. In the first year after surgery, there was a significant increase of the preoperative SF-36 scores to 65, 61, and 61 for Groups C, B, and A, respectively, that represents an improvement of 83%, 77%, and 79%, respectively. In the second year after surgery and thereafter, there was a further increase of SF-36 scores of 19%, 23%, and 21% for Groups C, B, and A, respectively. The mean preoperative scores of Visual Analogue Scale for low back pain for Groups C, B, and A were 5, 4.5, and 4.3, respectively, and decreased after surgery to 1.9, 1.5, and 1.6, respectively. The mean preoperative scores of the Visual Analogue Scale for leg pain for Groups C, B, and A were 7.6, 7.1, and 6.9, respectively, and decreased after surgery to 2.5, 2.5, and 2.7, respectively. All fusions healed radiologically within the expected time in all three groups without pseudarthrosis or malunion. Delayed hardware failure (1 screw and 2 rod breakages) 1 year and 18 months after surgery without radiologic pseudarthrosis was observed in 2 patients in Group C. Asymptomatic radiolucent areas were shown around pedicle screws in the pedd pedicle screws in the pedicles L5 and S1 in 2, 3, and 4 cases in Group C, A, and B, respectively. There was no adjacent segment degeneration in any spine until the last evaluation.

DISCUSSION AND CONCLUSION

This comparative study showed that all three instrumentations applied over a short area for symptomatic degenerative spinal stenosis almost equally after surgery maintained the preoperative global and segmental sagittal profile of the lumbosacral spine and was followed by similarly significant improvement of both self-assessment and pain scores. Hardware failure occurred at a low rate following dynamic instrumentation solely without radiologically visible pseudarthrosis or loss of correction. Because of the similar clinical and radiologic data in all three groups and the relative small number of patients that were included in each group, it is difficult for the authors to make any recommendation in favor of any instrumentation.