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.

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.

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.

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 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.

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.

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.