Steven Mardjetko

Pedicle morphology in thoracic adolescent idiopathic scoliosis: is pedicle fixation an anatomically viable technique?

Study Design. A radiographic study of thoracic pedicle anatomy in a group of adolescent idiopathic scoliosis (AIS) patients. Objective. To investigate the anatomic constraints of the thoracic pedicles and determine whether the local anatomy would routinely allow pedicle screw insertion at every level. Summary of Background Data. In spite of the clinical successes reported with limited thoracic pedicle screw-rod constructs for thoracic AIS, controversy exists as to the safety of this technique. Material and Methods. Twenty-nine patients with right thoracic AIS underwent preoperative thoracic CT scans and plain radiographs. Anatomic parameters were measured from T1 to T12. Results. Information on 512 pedicles was obtained. The transverse width of the pedicles from T1 through T12 ranged from 4.6–8.25 mm. The medial pedicle to lateral rib wall transverse width from T1 through T2 ranged from 12.6 to 17.9 mm. Measured dimensions from the CT scans showed the actual pedicle width to be 1–2 mm larger than would have been predicted from the plain radiographs. Age, Risser grade, curve magnitude, and the amount of segmental axial rotation did not correlate with the morphology or size of the thoracic pedicles investigated. In no case would pedicle morphology have precluded the passage of a pedicle screw. Conclusion. Based on the data identified in this group of adolescent patients, it is reasonable to consider pedicle screw insertion at most levels and pedicle-rib fixation at all levels of the thoracic spine during the treatment of thoracic AIS.

The use of the T1 sagittal angle in predicting overall sagittal balance of the spine.

BACKGROUND CONTEXT A balanced sagittal alignment of the spine has been shown to strongly correlate with less pain, less disability, and greater health status scores. To restore proper sagittal balance, one must assess the position of the occiput relative to the sacrum. The assessment of spinal balance preoperatively can be challenging, whereas predicting postoperative balance is even more difficult. PURPOSE This study was designed to evaluate and quantify multiple factors that influence sagittal balance. STUDY DESIGN Retrospective analysis of existing spinal radiographs. METHODS A retrospective review of 52 adult spine patient records was performed. All patients had full-column digital radiographs that showed all the important skeletal landmarks necessary for accurate measurement. The average age of the patient was 53 years. Both genders were equally represented. The radiographs were measured using standard techniques to obtain the following parameters: scoliosis in the coronal plane; lordosis or kyphosis of the cervical, thoracic, and lumbar spine; the T1 sagittal angle (angle between a horizontal line and the superior end plate of T1); the angle of the dens in the sagittal plane; the angle of the dens in relation to the occiput; the sacral slope; the pelvic incidence; the femoral-sacral angle; and finally, the sagittal vertical axis (SVA) measured from both the dens of C2 and from C7. RESULTS It was found that the SVA when measured from the dens was on average 16 mm farther forward than the SVA measured from C7 (p<.0001). The dens plumb line (SVA(dens)) was then used in the study. An analysis was done to examine the relationship between SVA(dens) and each of the other measurements. The T1 sagittal angle was found to have a moderate positive correlation (r=0.65) with SVA(dens), p<.0001, indicating that the amount of sagittal T1 tilt can be used as a good predictor of overall sagittal balance. When examining the other variables, it was found that cervical lordosis had a weak correlation (r=0.37) with SVA(dens) that was unexpected, given that cervical lordosis determines head position. Thoracic kyphosis also had a weak correlation (r=0.26) with SVA(C1), which was equally surprising. Lumbar lordosis had a slightly higher correlation (r=0.38), p=.006, than the cervical or thoracic spine. A multiple regression was run on the data to examine the relationship that all these independent variables have on SVA(dens). SPSS (SPSS, Inc., Chicago, IL, USA) was used to create a regression equation using the independent variables of T1 sagittal angle, cervical lordosis, thoracic kyphosis, lumbar lordosis, sacral slope, pelvic incidence, and femoral-sacral angle and the dependent variable of SVA(dens). The model had a strong correlation (r=0.80, r(2)=0.64) and was statistically significant (p<.0001). The T1 sagittal angle was the variable that had the strongest correlation with the SVA(dens) Spearman r=0.65, p<.0001, followed by pelvic incidence, p=.002, and lumbar lordosis, p=.006. We also observed that when the T1 tilt was higher than 25°, all patients had at least 10 cm of positive sagittal imbalance. In addition, patients with negative sagittal balance had mostly low T1 tilt values, usually lower than 13°. The other variables were not shown to have a statically significant influence on SVA. CONCLUSIONS This analysis shows that many factors influence the overall sagittal balance of the patient, but it may be the position of the pelvis and lower spine that have a stronger influence than the position of the upper back and neck. Unfortunately, to our knowledge, there are no studies to date that have established a normal sagittal T1 tilt angle. However, our analysis has shown that when the T1 tilt was higher than 25°, all patients had at least 10 cm of positive sagittal imbalance. It also showed that patients with negative sagittal balance had mostly low T1 tilt values, usually below 13° of angulation. The T1 sagittal angle is a measurement that may be very useful in evaluating sagittal balance, as it was the measure that most strongly correlated with SVA(dens). It has its great utility where long films cannot be obtained. Patients whose T1 tilt falls outside the range 13° to 25° should be sent for full-column radiographs for a complete evaluation of their sagittal balance. On the other hand, a T1 tilt within the above range does not guarantee a normal sagittal balance, and further investigation should be performed at the surgeons discretion.

The Scoliosis Research Society Health-Related Quality of Life (SRS-30) age-gender normative data: an analysis of 1346 adult subjects unaffected by scoliosis.

Study Design. Prospective, cross-sectional study. Objective. To determine Scoliosis Research Society (SRS)-30 health-related quality of life (HRQOL) reference values by age and gender in an adult population unaffected by scoliosis thereby allowing clinicians and investigators to compare individual and/or groups of spinal deformity patients to their generational peers. Summary of Background Data. Normative data are collected to establish means and standard deviations of health-related quality of life outcomes representative of a population. The SRS HRQOL questionnaire has become the standard for determining and comparing treatment outcomes in spinal deformity practices. With the establishment of adult SRS-30 HRQOL population values, clinicians, and investigators now have a reference for interpretation of individual scores and/or the scores of subgroups of adult patients with spinal deformities. Methods. The SRS-30 HRQOL was issued prospectively to 1346 adult volunteers recruited from across the United States. Volunteers self-reported no history of scoliosis or prior spine surgery. Domain medians, means, confidence intervals, percentiles, and minimum/maximum values were calculated for six generational age–gender groups: male/female; 20–39, 40–59, and 60–80 years of age. Results. Median and mean domain values ranged from 4.1 to 4.6 for all age–gender groups. The older the age–gender group, the lower (worse) the reported domain median and mean scores. The only exception was the mental health domain scores in the female groups which improved slightly. Males reported higher (better) scores than females but only the younger males were significantly higher in all domains than their female counterparts. In addition, all male groups reported higher Mental Health domain scores than their female counterparts (P = 0.003). Conclusion. This study reports population medians, means, standard deviations, percentiles, and confidence intervals for the domains of the SRS-30 HRQOL instrument. Clinicians must be mindful of age–gender differences when assessing deformity populations. Generational decreases noted in the older adult volunteer scores may provide a basis for future investigators to interpret observed score decreases in patient cohorts at long-term follow-up.

A comparison of magnetic and radiographic imaging artifact after using three types of metal rods: stainless steel, titanium, and vitallium

BACKGROUND CONTEXT After spinal fusion surgery, postoperative management often includes imaging with either computed tomography (CT) or magnetic resonance imaging (MRI) to assess the spinal canal and nerve roots. The metallic implants used in the fusion can cause artifact that interferes with this imaging, reducing their diagnostic value. Stainless steel is known to produce large amounts of artifact, whereas titanium is known to produce significantly less. Other alloys such as vitallium are now being used in spinal implants, but their comparison to titanium and stainless steel has not been well documented in the orthopedic literature. Titanium is a desirable metal because of its light weight and lower production of artifact on imaging, although it is not as stiff as stainless steel. Vitallium is proposed as a replacement for titanium because it has stiffness similar to stainless steel, while still being as light as titanium. PURPOSE The purpose of this study was to compare the amount of artifact produced on MRI and CT by three types of spinal implants: stainless steel, titanium, and vitallium. STUDY DESIGN A prospective experimental design was used to compare three types of spinal implants used in posterior spinal fusion surgery. OUTCOME MEASURES The resulting images were evaluated by a radiologist to measure the amount of artifact (in millimeters) and by an orthopedic surgeon to assess the diagnostic quality (on a Likert scale). METHODS A porcine torso was used for repeated MRI and CT scans before and after implantation with pedicle screws and rods made of the three metals being studied. RESULTS Images produced after the insertion of vitallium rods and titanium screws as well as those with titanium rods and screws were found to have less artifact and a better overall diagnostic quality than those produced with stainless steel implants. Overall, there was not a difference between the amount of artifact in the spinal images with vitallium and titanium rods, with the exception of a few trials that showed small but statistically significant differences between the two metals, where titanium had slightly better images. CONCLUSIONS If vitallium rods are used in posterior spinal surgery in place of implants made of titanium or stainless steel, any postoperative imaging of the spine using MRI or CT should have amounts of artifact that are similar to titanium and better than stainless steel.

Comparison of Radiographic and Surface Topography Measurements in Adolescents with Idiopathic Scoliosis

Purpose: In patients with adolescent idiopathic scoliosis (AIS), radiographic surveillance is the gold standard of assessing spinal deformity, but has negative long-term effects. The Formetric 4D surface topography system was compared to standard radiography as a safer option for evaluating patients with AIS. Methods: Fourteen volunteers with typical AIS patient stature had 30 repeated Formetric 4D measurements taken, and reproducibility was assessed. Sixty-four patients with AIS were then enrolled during routine clinic visits. Evaluation included standard radiographs and surface topography measurements. A comparison analysis was performed. Results: When assessing same-day repeated scans, a standard deviation of +/- 3.4 degrees for scoliosis curve measurements was determined, and the Reliability Coefficient (Cronbach) was very high (0.996). Cobb angles measured with the Formetric 4D differed from radiographic measurements by an average of 9.42 (lumbar) and 6.98 (thoracic) degrees, while the correlation between the two measurements was strong (95% confidence interval [CI]), 0.758 (lumbar) and 0.872 (thoracic) respectively. Conclusions: The Formetric 4D is comparable to radiography in terms of its test-retest reproducibility. Although this device does not predict curve magnitude exactly, the predictions correlate strongly with the Cobb angles determined from radiographs. It can be reliably used in the surveillance of patients with AIS.

Aneurysmal bone cysts of the spine : Excision and stabilization

The treatment of aneurysmal bone cysts (ABCs) of the spine remains controversial in the literature. Treatment options have included radiation, curettage and bone graft, extirpation, and various combinations of these. Conspicuously missing in previously published articles and texts are guidelines for dealing with the instability and deformity that often accompany ABCs of the spine. The index case in this report highlights the potentially devastating effects of treating the tumor in isolation without addressing the concomitant deformity and instability. The status of the structural integrity of the spine must be assessed before initiating treatment. If instability or deformity or both are already present or if the amount of osseous tissue to be resected may render the spine unstable, then instrumentation and fusion should be performed at the time of surgical resection or before other forms of therapy. We present three cases of ABCs of the spine in which the tumor itself was treated with surgical extirpation and the associated deformity and instability were treated with spinal instrumentation and long fusions.

Selective anterior fusion and instrumentation for the treatment of neuromuscular scoliosis

Study Design A retrospective cohort study was conducted. Objective To evaluate the results of anterior spinal fusion with anterior instrumentation alone in selected patients with neuromuscular scoliosis. Summary of Background Data Traditionally posterior spinal fusion with instrumentation has been done, usually to the pelvis, to achieve correction of neuromuscular scoliosis. However, certain selected patients might benefit from shorter fusion segment to preserve some motion and yet still achieve good correction of the curve. This may serve to improve or preserve various functional abilities that might be adversely affected by a long fusion. Method Patients who had anterior spinal fusion (ASF) with anterior instrumentation (AI) alone were selected from an entire group of patients with neuromuscular spinal deformity who had surgery at Shriners Hospital for Children-Chicago since January of 1988. The charts and radiographs of these patients were examined and various radiographic parameters were measured pre- and after surgery and at final follow-up. Additionally, functional level of the patients included, ambulatory status was obtained from the medical records. Results In these 21 patients excellent results were obtained with regard to primary and secondary curve correction as well as the pelvic obliquity without significant deterioration at final follow-up. Ambulatory status was not changed after surgery. This cohort of patients had various neuromuscular diseases. However, the majority of them had myelomeningocele. Few complications occurred which resulted in the reoperation of several patients who had progression of the curve around the instrumented segment which itself remained unchanged when the complication was recognized. One infection occurred requiring irrigation and debridement Conclusions In selected patients with neuromuscular scoliosis, even that associated with pelvic obliquity, excellent correction and maintenance correction can be obtained fusing a relatively short segment of the spine with ASF and AI rather than a long construct posteriorly to the pelvis. Maintenance of the correction of the primary curve as well as the pelvic obliquity was maintained over the period of follow-up. This approach for selected patients should be offered as a way of limiting the extend of the surgery, preserving motion segments and maintaining orenhancing functions such as activities of daily living.

Arterial injury following percutaneous vertebral augmentation: a case report.

Study Design. Case report. Objective. To report a case of injury to a segmental branch of the L4 lumbar artery following kyphoplasty. Summary of Background Data. To our knowledge, arterial injury following vertebral augmentation has not been described. The complications that have been reported rarely require additional intervention. The caliber of the fourth lumbar artery is such that injury to it, or to its more proximal branches, may cause significant morbidity. Methods. An 84-year-old female who presents 10 days after surgery from L5 kyphoplasty with pulsatile bleeding from the kyphoplasty site. An angiogram revealed an injury to a segmental branch of L4 lumbar artery. Results. A superselective angiogram was performed, followed by embolization of a branch of the L4 lumbar artery. This procedure successfully controlled the bleeding. Conclusion. Surgeons performing percutaneous procedures for the augmentation of vertebral compression fractures are not able to visualize the arterial channels on the posterior aspect of the vertebral column. Although injury to these structures may be difficult to prevent, awareness of this complication will improve our response and decrease associated morbidity.

Electromagnetic topographical technique of curve evaluation for adolescent idiopathic scoliosis.

Study Design. Diagnostic testing. Objective. The goal of this study is to measure the accuracy and reliability of the Orthoscan (Orthoscan Technologies, Inc.) and to determine whether it can be substituted for radiographs in the surveillance of adolescent idiopathic scoliosis (AIS). Summary of Background Data. AIS is usually followed using scoliosis radiographs, which offer the most reliable way to quantify the curve, but carry the risk of exposure to ionizing radiation. The Orthoscan is a nonradiographic topographic method for measuring spinal curves. Materials and Methods. There were 5 phases of this study that measured: the accuracy and reliability of the machine when used with a plastic model; the variability with a real patient; the intraobserver variability; the correlation between the measurements of the machine and that of the radiograph; and the correlation between the change in radiograph measurement over time and the change in Orthoscan measurement over time. Results. In measurement of a static plastic model, the machine measured curves with a standard deviation of ±1° in trunk rotation and ±2° in curve measurement. Error increased with a real patient. Thirty-six comparisons in the thoracic spine, and 19 comparisons in the lumbar spine, were made between measurements using the Orthoscan and radiographs. Mean curves in the 2 groups were not significantly different and had poor-to-moderate correlation. Longitudinal evaluation included 47 curves in 28 patients. The Orthoscan predicted the radiograph change within an acceptable range 55.3% of the time. Conclusions. The Orthoscan does not accurately predict the scoliosis curve magnitude or the overall change in curve over time. While analysis in groups of patients using this technique reveals group means that begin to look acceptable, if the variability is too great, then this technology is not yet ready to replace the radiograph in the evaluation of a scoliosis curve.

Atlantoaxial rotatory fixation in the setting of associated congenital malformations: A modified classification system

Study Design. A case report. Objective. To raise awareness of the development of atlantoaxial rotatory fixation (AARF) in the setting of congenital vertebral anomalies/malformations. Summary of Background Data. Klippel-Feil Syndrome (KFS) is a complex, heterogeneous condition noted as congenital fusion of 2 or more cervical vertebrae with or without spinal or extraspinal manifestations. Although believed to be a rare occurrence in the population, KFS may be underreported. Proper diagnosis of KFS and other congenital conditions affecting the spine is imperative to devise proper management protocols and avoid potential complications resulting from the altered biomechanics associated with such conditions and their abnormal vertebral morphology. Craniovertebral dislocation and AARF may cause severe cervicomedullary and spinal cord compression and could thereby be potentially fatal, especially in patients with KFS who present with congenitally-associated comorbidities. Methods. A 13-year-old boy with Chiari type I malformation, craniofacial abnormalities, and other irregularities underwent thoracolumbar spine surgery for his scoliosis curve correction at another institution, which immediately following surgery he became a quadriparetic. The initial preoperative assessment of his cervical spine was limited and the associated KFS was initially undiagnosed. At 14 years of age, he presented to our clinic with an ASIA-C spinal cord injury. Plain radiographs, normal and 3-dimensional reformatted computed tomographs (CT), and magnetic resonance imaging (MRI) noted assimilation of the patients occiput to the atlas (occipitalization) with congenital fusion of C2–C3, indicative of KFS, and the presence of anterior craniovertebral dislocation with a Fielding and Hawkins type II AARF. Closed reduction of the craniovertebral dislocation was noted, but his atlantoaxial rotatory subluxation was nonresponsive and fixed (AARF). As such, at the age of 14, the patient underwent posterior instrumentation and fusion from the occiput to C4 to maintain reduction of thecraniovertebral dislocation and reduce his AARF. Results. At 9 months postoperative follow-up of his craniovertebral surgery, the instrumentation remained intact, reduction of the atlantoaxial rotatory subluxation was maintained, and posterior bone fusion was noted. Neurologically, he remained an ASIA-C without any substantial return of function. Conclusion. This report raises awareness for the need of a thorough evaluation of the cervical spine to determine patients at high risk for craniovertebral dislocation and atlantoaxial rotatory subluxation, primarily in the context of KFS or other congenital conditions. Three-dimensional CT and MR imaging are ideal radiographic methods to determine the presence and extent of craniovertebral dislocation, AARF, and of abnormal vertebral anatomy/malformations. In addition, the authors propose a modification to the Fielding and Hawkins classification of AARF to include variants and subtypes that account for abnormal anatomy and congenital anomalies/malformations.