Motion capture evaluation of sagittal spino-pelvic biomechanics after lumbar spinal fusion.

PURPOSE: The spine and pelvis coexist as a dynamic linked system in which spinal and pelvic parameters are correlated. Investigation of this system can inform the understanding and treatment of spinal deformity. Here, we demonstrate the use of motion capture technology to measure spine biomechanical parameters using a novel testing apparatus. METHODS: Three complete cadaveric spines with skull and pelvis were mounted into a biomechanical testing apparatus. Each lumbar vertebra was monitored by motion capture cameras as the spines underwent maximal anterior and posterior pelvic tilts about two sagittal axes at a controlled speed and applied force. These axes were defined as the sacral axis which passes transversely through the ilium and S1, and the acetabular axis which passes transversely through both acetabula. The experiments were repeated after L4-L5 fusion, and then, after both L4-L5 and T12-S1 fusion with pedicle screw instrumentation. Data were collected for total range of motion and for coupled translation at each functional spinal unit (FSU). RESULTS: Total range of motion and coupled translation within functional spinal units (FSUs) was decreased after spinal fusion. The displacement of each individual FSU was captured and summarized along with the observed patterns under each experimental condition. CONCLUSION: Lumbar fusion decreases spinal motion in the sagittal plane in both overall ROM and individual coupled translations of lumbar vertebrae. This was demonstrated using motion capture technology which is useful for quantifying the translations of individual FSUs in a multisegmental spinal model.

Does It Matter: Total Hip Arthroplasty or Lumbar Spinal Fusion First? Preoperative Sagittal Spinopelvic Measurements Guide Patient-Specific Surgical Strategies in Patients Requiring Both.

BACKGROUND: In patients requiring both total hip arthroplasty (THA) and lumbar spinal fusion (LSF), consideration of preoperative sagittal spinopelvic measurements can aid in the prediction of postfusion compensatory changes in pelvic tilt (PT) and inform adjustments to traditional THA cup anteversion. This study aims to identify relationships between spinopelvic measurements and post-THA hip instability and to determine if procedure order reveals a difference in hip dislocation rate. METHODS: Patients at a single practice site who received both THA and LSF between 2005 and 2015 (292: 158 = LSF prior to THA, 134 = THA prior to LSF) were retrospectively reviewed for incidents of THA instability. Those with complete radiograph series (89) had their sagittal (standing) spinopelvic profiles measured preoperatively, immediately postoperatively, and 3 months, 6 months, 1 year, 1.5 years, and 2 years postoperatively. Measured parameters included lumbar lordosis (LL), pelvic incidence (PI), PT, and sacral slope (SS). RESULTS: No significant differences in dislocation rates between operative order groups were elicited (7/73 LSF first, 4/62 THA first; Z = 0.664, P = .509). Compared to nondislocators, dislocators had lower LL (-10.9) and SS (-7.8), and higher PT (+4.3) and PI-LL (+7.3). Additional risk factors for dislocation included sacral fusion (relative risk [RR] = 3.0) and revision fusion (RR = 2.7) . Predictive power of the model generated through multiple regression to characterize individual profiles of post-LSF PT compensation based on perioperative measurements was most significant at 1 year (R2 = 0.565, F = 0.000456, P = .028) and 2 years (R2 = 0.741, F = 0.031, P = .001) postoperatively. CONCLUSION: In performing THA after LSF, it is theoretically ideal to proceed with THA at a postfusion interval of at least 1 year, beyond which further compensatory PT change is minimal. However, the order of surgical procedure revealed no statistical difference in hip instability rates. In cases characterized by large PI-LL mismatch (larger or less predictable compensation profiles) or large SS or LL loss (considerably atypical muscle recruitment), consideration of full functional anteversion range between sitting and standing positions to account for abnormalities not appreciated with standing radiographic assessment alone may be warranted.

The Four Fixation Points of the Axis: Technique and Case Report.

BACKGROUND: Instrumentation of the axis can be accomplished through a variety of techniques including transarticular screw fixation, pars and pedicle screw fixation, translaminar screw fixation, and posterior wiring. We report on the evolution of the axial 4-screw technique. METHODS: Retrospective case review. After exposure of posterior spinal elements, the medial and superior walls of the C2 pedicle were identified from within the spinal canal. A high-speed drill was then advanced under lateral fluoroscopy, which guided craniocaudal angulation. Medial angulation was based on anatomic landmarks and preoperative imaging. This was followed by placement of translaminar screws according to the technique described by Wright. When extending the construct into the subaxial spine or the occiput, lateral connectors are placed in translaminar screws, which are usually more offset. The rod is directly connected to the pedicle screws, which are usually more in alignment with the subaxial/occipital instrumentation. RESULTS: Two male patients ages 56 and 58 underwent posterior instrumentation of the axis employing a combination of pedicle and laminar polyaxial screws. Indications included multilevel spinal cord compression and deformity in a patient with Down syndrome and cervical meningioma, respectively. Follow-up was 1 year and 5 years, respectively. Medical complications (N = 2) occurred in the patient with Down syndrome resulting in prolonged intubation with tracheostomy placement. Reduction was maintained in both patients at last follow-up. There were no neurologic, vascular, or instrumentation related complications. CONCLUSIONS: The axis serves as a versatile anchor point and offers 4 potential points of fixation. Lateral connectors play a crucial role and allow for incorporation of the C2 screws with the rest of the construct. Local anatomy will dictate the necessity and ability to place instrumentation and detailed preoperative planning is of paramount importance.

Extreme proximal junctional kyphosis-a complication of delayed lambdoid suture closure in Hajdu-Cheney syndrome: a case report and literature review.

PURPOSE: To describe the manifestations, surgical treatment, and potential complications of Hajdu-Cheney syndrome (HCS), and the management of these complications. METHODS: The clinical presentation, management and outcome of HCS with severe osteoporosis and open skull sutures is presented, together with a literature review. RESULTS: A 20-year-old female with HCS underwent posterior occipitocervical fusion for symptoms of progressive basilar invagination. Because of delayed lambdoid suture closure, the stiff fusion construct lead to increased suture distraction, most notably in the upright (suture-open) position, with relief in the supine (suture-closed) position. This was successfully remedied with extension of the fusion construct anteriorly over the skull vertex to the frontal bones. CONCLUSIONS: In patients with HCS and other conditions with delayed suture closure, the surgeon must be cognizant of the presence of mobility at the suture lines, and consider extending the fusion construct anteriorly over the skull vertex up to the frontal bones. Because of significant osteoporosis in these syndromes, multiple fixation points and augmentation with bone graft are important principles.

Complications in Adult Patients with Down Syndrome Undergoing Cervical Spine Surgery Using Current Instrumentation Techniques and rhBMP-2: A Long-Term Follow-Up.

Introduction Cervical spine pathologies are common in Down syndrome (DS) patients. Cervical pathologies may cause cord compression and neurologic deterioration if left untreated. Complication rates of 73-100% have been reported in DS patients after cervical spine surgery in historical studies. This study reports updated perioperative complications rates and long-term outcome in patients with DS undergoing cervical spine surgery. Methods Retrospective review of patients with DS who have undergone cervical spine surgery from 1998 to 2011 (≥ 24 months of follow-up) was undertaken. Series of 17 adults with preoperative diagnoses that included atlantoaxial instability, stenosis, spondylosis, or cervical spondylolisthesis were evaluated. Nine patients received recombinant human bone morphogenetic protein-2 (rhBMP-2). Neurologic and ambulatory status was evaluated at regular intervals included pre- and postoperative imaging, range of motion evaluation, strength/neurologic testing, ambulation observation, and patient and caretaker pain reporting. Results A total of 20 surgical procedures were performed in 17 patients. Average follow-up was 78.7 months (range: 25-156 months). Overall, 37 complications were observed including pneumonia, respiratory distress, reintubation, dysphagia, deep venous thrombosis, sepsis, wound infection, dehiscence, neurologic complications, loss of reduction (LOR), pseudarthrosis, and hardware failure. Postoperative pneumonia was most common (23.5%). Three patients developed pseudarthrosis (all in the rhBMP-2 group); three demonstrated LOR. Neurologic complications (N = 3) included spasticity, loss of ambulation, and postoperative weakness with myelomalacia. Two were transient. Respiratory complications in the rhBMP-2 group were the most common (N = 3). The anterior approach resulted in a higher likelihood of complications than the posterior (p = 0.032). Conclusions Current techniques may improve pseudarthrosis (p = 0.009), LOR (p = 0.043), and first attempt (p = 0.038) and overall fusion rates (p = 0.018) compared with historical studies. Complications continue to challenge most patients (82.4%). A total of 16 of 17 patients (94.1%) demonstrated stabilization or improvement in neurologic status. Apparent successful outcome in the majority appears to warrant the high complication risk associated with cervical spine surgery in DS patients. The anterior approach resulted in a higher risk of complications than posterior (p = 0.032). We report a higher than expected incidence of pseudarthrosis in DS patients receiving rhBMP-2, putting its benefit in DS patients into question.

Comparison of radiographic sagittal spinopelvic alignment between skeletally immature and skeletally mature individuals with Scheuermann's disease.

PURPOSE: The aim of this study was to compare radiographic sagittal spinopelvic parameters between skeletally immature and skeletally mature patients with Scheuermann's disease (SD). METHODS: Cross-sectional analysis of standing postero-anterior and lateral radiographs of the spine of patients with SD was performed. Sagittal vertical axis (SVA), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS) were measured on the lateral radiographs. Risser's sign was assessed on the postero-anterior radiographs. All of the parameters measured were compared between skeletally immature (Risser's sign 0-3) versus mature patients (Risser's sign 5). PI, PT, and SS in both groups were compared to PI, PT, and SS reported for normal children, adolescents, and adults. RESULTS: Sixty-six patients with SD (33 immature and 33 mature) were retrospectively reviewed and included in the study. There was no significant difference between the two groups of SD patients in: SVA (-16.6 vs. -22.9 mm, p = 0.74), TK (57.8° vs. 56°, p = 0.66), TLK (7.8° vs. 11.7º, p = 0.14), LL (63.2° vs. 62.2°, p = 0.74), PI (36.7° vs. 39.4°, p = 0.20), PT (3.8° vs. 7.3°, p = 0.10), and SS (32.8° vs. 32.1°, p = 0.75). Both, the immature and mature group of SD patients presented significantly lower PI and SS than normal children, adolescents, and adults, and significantly lower PT than normal adults. CONCLUSIONS: There is no significant difference in sagittal spinopelvic parameters between skeletally immature and mature subjects with SD. Pelvic incidence in both groups of SD patients was significantly lower than PI in normal children, adolescents, and adults. This challenges the role of PI in predicting desired LL in patients with SD.

Radiographic spinopelvic parameters in skeletally mature patients with Scheuermann disease.

STUDY DESIGN: Retrospective radiographical analysis of sagittal spinopelvic parameters in skeletally mature patients with Scheuermann disease (SD). OBJECTIVE: To analyze anatomical and positional parameters of spinopelvic sagittal alignment in mature patients with SD. SUMMARY OF BACKGROUND DATA: Sagittal spinopelvic alignment has already been characterized in normal subjects and deviations in sagittal parameters have been reported for various spinal pathologies. No study has investigated spinopelvic parameters in SD. METHODS: Standing posteroanterior and lateral radiographs of the skeletally mature patients with SD were analyzed. Immature patients and those with other spinal pathologies were excluded from the study. Pelvic positional and anatomic parameters and spinal parameters were measured. Pelvic incidence (PI) was compared with the values reported for healthy individuals. Correlations between the measured parameters were analyzed. RESULTS: Forty patients met the inclusion criteria. Sixteen females and 24 males (mean age, 25 yr) were analyzed. The mean PI in this group was 40° and was significantly lower than that reported for healthy adults and adolescents (P < 0.0001) and not significantly different than the values reported for healthy children (P = 0.44). Patients with atypical (thoracolumbar) SD had lower PI than those with typical (thoracic) form (41° vs. 38°; P = 0.09). There was no correlation between PI and LL, thoracic kyphosis, or thoracolumbar kyphosis. CONCLUSION: This study demonstrated that skeletally mature patients with SD have significantly lower PI than healthy adults. There was no correlation between PI and LL in individuals with SD. This challenges the role of PI in predicting the proper values of LL in this group of patients. Further studies are needed to investigate whether impaired spinopelvic alignment is a cause or a result of SD. LEVEL OF EVIDENCE: 3.

Lumbar Spondylolysis and Spondylolisthesis in Down Syndrome: A Cross-sectional Study at One Institution.

STUDY DESIGN: Retrospective cross-sectional study. OBJECTIVES: To describe lumbar spondylolysis and spondylolisthesis and establish their prevalence in individuals with Down syndrome. SUMMARY OF BACKGROUND DATA: Orthopedic problems in Down syndrome are variable and numerous. Lumbar spondylolysis and spondylolisthesis may be common conditions in Down syndrome. However, there has been a paucity of data on the association of these conditions in the published literature. METHODS: A retrospective review of 110 patients with Down syndrome seen at a single institution from 2000 through 2012 was performed. Medical records, X-rays, and physician dictations were carefully reviewed to establish a detailed database of the study population. RESULTS: Of the 110 patients in the study, 20 exhibited spondylolysis (unilateral, n = 11; bilateral, n = 9), whereas 38 had lumbar spondylolisthesis (isthmic, n = 9; dysplastic, n = 2; degenerative, n = 27). No gender difference was noted (p ≥ .7732). Fifteen patients reported low back pain (LBP) and/or leg pain. There was no significant association between LBP, leg pain, and spondylolysis (p = .9232). Both of these symptoms were highly predictive of lumbar spondylolisthesis, however (p = .0006). No significant findings were noted in pelvic parameters (pelvic incidence, sacral slope, pelvic tilt, or lumbar lordosis) in this study. CONCLUSIONS: The prevalence of spondylolysis and spondylolisthesis in individuals with Down syndrome may be as high as 18.7% and 32.7%, respectively, significantly higher than in the non-Downs population. Etiopathogenesis of these conditions in Down syndrome does not appear to be related to pelvic parameters. Low back pain and leg pain may be more predictive of spondylolisthesis in Down syndrome than in the general population. Therefore, it is recommended that individuals with Down syndrome and LBP and/or leg pain be evaluated for lumbar spondylolisthesis.

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.

Convex hemiepiphysiodesis: the limits of vertebral stapling.

STUDY DESIGN: We performed a retrospective chart review of patients with nonadolescent idiopathic scoliosis who underwent open vertebral stapling for treatment of spinal deformity. OBJECTIVE: The objective of this study was to determine the efficacy of vertebral stapling in patients with scoliosis. Measurements included initial deformity correction and maintenance of correction. SUMMARY OF BACKGROUND DATA: Growth modulation has become a topic of interest recently in the spinal deformity literature. It refers to the tethering of growth on one side of the spine to allow for compensatory growth on the contralateral side, and, in theory, correction of scoliosis. Recent studies on endoscopic vertebral stapling have shown promising early results in adolescents with idiopathic scoliosis. Little is known about its applicability in patients with more "malignant" types of scoliosis. METHODS: The medical records and radiographs of 11 children who underwent open vertebral stapling between June 2003 and August 2004 were reviewed. Patients with adolescent idiopathic scoliosis (AIS) were excluded. RESULTS.: Diagnoses included myelodysplasia, congenital scoliosis, juvenile, and infantile idiopathic scoliosis, Marfan syndrome, paralytic scoliosis, and neuromuscular scoliosis. The average age at surgery was 6 + 11 year. All patients were skeletally immature. Preoperative curves averaged 68° (22°-105°). Of the 11, six thoracic curves and five thoracolumbar curves were stapled. Four patients had minor curves, which were not stapled. Initial postoperative radiographs averaged 45° (24°-88°). Average follow-up was 22 month for our series (16-28 month). At final follow-up, scoliosis averaged 69° (36°-107°). Five of the 11 patients have subsequently undergone secondary surgical procedures for progression of scoliosis, including growing rod insertion in three, combined anterior/posterior spinal fusion in another, and bilateral vertical expandable prosthetic titanium rib insertion in a patient with myelodysplasia. Three of the remaining six patients are scheduled for secondary surgery. CONCLUSION: More than half of the patients in our series have undergone or are scheduled to undergo further spinal surgery, at an average of 2 year after anterior vertebral stapling. It is unclear if progression may be related to the young age at surgery, the relatively severe average preoperative curve magnitude, the nature of the underlying scoliosis, or a combination of these.

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.

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 surgeon's discretion.

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.

Intraoperative techniques to reduce the potential of set-screw loosening in long spinal constructs: a static and fatigue biomechanical investigation.

STUDY DESIGN: The purpose of this study was to investigate the effects of implant selection and set-screw tightening technique on the loosening torques in long scoliosis constructs after long-term biaxial fatigue loading. SUMMARY OF BACKGROUND DATA: Expanded use of pedicle screws in the correction of long scoliotic curves and the mechanical demands on segmental fixation systems requires surgeon awareness of revisiting set screws to ensure full screw/rod engagement and minimize the potential of set-screw loosening and/or rod slippage postoperatively. METHODS: Biomechanical tests were performed to evaluate the effect of set-screw tightening techniques and rod approximation on screw/rod interface strength. RESULTS: Rod reduction test shows the force required to approximate a rod to a pedicle screw is statistically lower with uniplanar or polyaxial screws, when compared with monoaxial screws. This ease of approximation in both polyaxial and uniplanar screws directly correlate to improvement in the axial slippage resistance. In the simulated spinal model construct, rod/screw securement can vary based on the number of tightening torques applied to the system. CONCLUSIONS: Sequential revisiting of sets crews in long scoliosis constructs resulted in a statistically significant increase in loosening torque for monoaxial and polyaxial screw systems. Intraoperative securement assessment of set screws is recommended. The use of polyaxial and uniplanar screws at the distal ends in long constructs is recommended to increase the screw/rod interface strength.

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 patient's 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.

Iatrogenic thoracic outlet syndrome secondary to vertical expandable prosthetic titanium rib expansion thoracoplasty: pathogenesis and strategies for prevention/treatment.

BACKGROUND: An innovative treatment for thoracic insufficiency syndrome involves a vertical expansion of the chest wall through a horizontal chest wall osteotomy maintained by a distraction device (vertical expandable prosthetic titanium rib or VEPTR). Upper-extremity neurovascular dysfunction has been reported after expansion. The purposes of this study are to identify potential etiologies for compression of the brachial plexus after expansion thoracoplasty and to suggest strategies to reduce the incidence of this complication. METHODS: A simulated VEPTR procedure was performed on 8 fresh cadaveric specimens. Manometric measurements were taken in the 3 anatomic regions of the thoracic outlet after thoracotomy and rib distraction were performed. Confirmation of the location of compression was performed by placing barium-impregnated putty along the course of the brachial plexus and evaluating the effect of expansion using video fluoroscopy. A midclavicular osteotomy was then performed and video fluoroscopy repeated. RESULTS: A 20% increase in pressure was seen in the costoclavicular region of the thoracic outlet after expansion. Constriction of the midclavicular region of the thoracic outlet between the first rib and clavicle was confirmed using the putty model. Midclavicular osteotomy alleviated this region of compression. CONCLUSIONS: Expansion thoracoplasty with the VEPTR procedure causes increased pressure in the costoclavicular region of the thoracic outlet. A midclavicular osteotomy may be one method to alleviate thoracic outlet narrowing after VEPTR procedure, although the short- and long-term effects of this is procedure is not known. CLINICAL RELEVANCE: Our model supports an iatrogenic thoracic outlet syndrome caused by expansion thoracoplasty. Based on our data as well as a review of the literature, we recommend intraoperative neurologic monitoring of the ipsilateral upper extremity during the VEPTR procedure.

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 degrees in trunk rotation and +/-2 degrees 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.

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.