Faculty Bibliography

Lumbar vertebrae are complicated in structure and function. The purpose of this study was to investigate the in-vivo motion characteristics of different portions of the lumbar vertebrae during functional activities. Motion of L2, L3 and L4 was reproduced using a combined dual fluoroscopic and MR imaging technique during flexion-extension and left-right twisting of the trunk. The ranges of motion (ROM) of the proximal vertebra with respect to the distal one at 3 representative locations: the center of the vertebral body, the center of the spinal canal and the tip of the spinous process were measured. Centers of rotation (COR) of the vertebrae were then determined by calculation of the points of zero motion in 2D sagittal and transverse planes. During flexion-extension, the center of the vertebral body moved less than 0.6mm, while the tip of the spinous process moved less than 7.5mm in the sagittal plane. The CORs of both L23 (L2 with respect to L3) and L34 were located inside the vertebral body, at a distance about one-third the length of the vertebral body from the posterior edge. During left-right twisting, the center of the vertebral body moved less than 1.0mm, while the tip of the spinous process moved less than 1.6mm in the transverse plane. The CORs of both L23 and L34 were located approximately 30mm anterior to the front edge of the vertebral body. The results of this study may be used to define the ideal locations for surgical placement of the disc prosthesis, thus help improve the prosthesis design and surgical treatment of various pathological conditions

Patients with Klippel-Feil syndrome (KFS) have congenital fusions of at least 1 cervical motion segment, and often present with compensatory hypermobility or symptomatic stenosis of the cranio-vertebral junction which requires occipitocervical reconstruction and fusion. One subgroup of KFS patients in which this is particularly common is those with isolated C2-3 congenital fusion (C2-3 CF). The anatomic suitability for C2 pedicle and laminar screw placement had been analyzed in the general adult population, and guidelines for their techniques had been established. However, the feasibility and safety of the two techniques in KFS patients with congenital C2-3 fusion has not been reported. This radiographic study was performed to evaluate the feasibility of these two widely used methods in such patients. We recruited 108 patients with atlantoaxial dislocation and reconstructed CTs were performed. Among them, 53 had C2-C3 congenital fusion diagnosed as KFS and 55 had normal cervical segmentation (NCS). The maximum possible diameters and length were measured along the ideal screw trajectories. Both of mean diameters and lengths of the C2 laminar screw trajectory in the C2-3 CF group were significantly larger than that in NCS. Mean diameters of the C2 pedicle screw trajectory in this group were significantly smaller than that in NCS group, however, C2-3 CF patients had longer pedicle paths than NCS. In the C2-3 CF group, all 53 cases had suitable trajectory for C2 laminar screw, while 21 (39.6%) had a pedicle diameter less than 4.5 mm. In the NCS group, 5 cases (9.1%) had a pedicle diameter less than 4.5 mm. All 108 cases had sufficient diameters for C2 laminar screw placement. Klippel-Feil patients with C2-3 CF are good candidates for the technique of C2 laminar screw. Preoperative radiography should be carefully evaluated and the option of C2 fixation be determined with a thorough consideration in these patients

Thoracic pedicle screws have superior anchoring strength compared with other available fixation techniques. However, these are not universally accepted in many developing countries because of the concerns regarding safety and complications. In addition, there is evidence that pedicle morphology is unique in Chinese patients. The goal of this study was to analyze the complications seen at our institution, while using thoracic pedicle screws for the treatment of thoracic deformity, and to determine the safety of our techniques for the treatment of thoracic deformity in a Chinese population. From 1998 to 2005, there were 208 thoracic deformity patients treated at our institution, 70 of whom were male and 138 were female. Their age ranged from 11 to 55 years (mean of 14.9 years). All of them underwent corrective deformity surgery using posterior pedicle screw systems and follow-up was available for at least 3 years. Etiologic diagnoses included adolescent idiopathic scoliosis in 119 patients, congenital kyphoscoliosis in 38, adult scoliosis in 37 and undetermined in 14. Screw positions were evaluated using intraoperative and postoperative radiographs and a CT scan was performed when a concern for screw malposition was present. All radiographic evaluations were carried out in a double-blinded fashion. A total of 1,123 thoracic pedicle screws were inserted (5.4 thoracic screws/patient). The deformity correction rate was 81, 65 and 62% for idiopathic, congenital and adult scoliosis patients, respectively. The overall complication rate was 16.5% at the final follow-up. Complication rates directly and indirectly related to pedicle screws were 7.2 and 9.3%, respectively. There were no significant screw-related neurologic or visceral complications that adversely affected long-term results. The complications seen with thoracic pedicle screws in a Chinese population were similar to other populations and could be utilized safely for the treatment of thoracic deformity in this population

Quantitative data on the range of in vivo vertebral motion is critical to enhance our understanding of spinal pathology and to improve the current surgical treatment methods for spinal diseases. Little data have been reported on the range of lumbar vertebral motion during functional body activities. In this study, we measured in vivo 6 degrees-of-freedom (DOF) vertebral motion during unrestricted weightbearing functional body activities using a combined MR and dual fluoroscopic imaging technique. Eight asymptomatic living subjects were recruited and underwent MRI scans in order to create 3D vertebral models from L2 to L5 for each subject. The lumbar spine was then imaged using two fluoroscopes while the subject performed primary flexion-extension, left-right bending, and left-right twisting. The range of vertebral motion during each activity was determined through a previously described imaging-model matching technique at L2-3, L3-4, and L4-5 levels. Our data revealed that the upper vertebrae had a higher range of flexion than the lower vertebrae during flexion-extension of the body (L2-3, 5.4 +/- 3.8 degrees ; L3-4, 4.3 +/- 3.4 degrees ; L4-5, 1.9 +/- 1.1 degrees , respectively). During bending activity, the L4-5 had a higher (but not significant) range of left-right bending motion (4.7 +/- 2.4 degrees ) than both L2-3 (2.9 +/- 2.4 degrees ) and L3-4 (3.4 +/- 2.1 degrees ), while no statistical difference was observed in left-right twisting among the three vertebral levels (L2-3, 2.5 +/- 2.3 degrees ; L3-4, 2.4 +/- 2.6 degrees ; and L4-5, 2.9 +/- 2.1 degrees , respectively). Besides the primary rotations reported, coupled motions were quantified in all DOFs. The coupled translation in left-right and anterior-posterior directions, on average, reached greater than 1 mm, while in the proximal-distal direction this was less than 1 mm. Overall, each vertebral level responds differently to flexion-extension and left-right bending, but similarly to the left-right twisting. This data may provide new insight into the in vivo function of human spines and can be used as baseline data for investigation of pathological spine kinematics

CMA values have been effectively used to evaluate the amount of BI, the brainstem and medulla compression, and the amount of postoperative decompression. However, the reliability and reproducibility of this measurement have yet to be determined. In addition, the information that is available concerning CMA values in normal individuals has been limited to small series of patients. We recruited 200 patients that underwent MR imaging of the craniovertebral junction (CVJ) for unrelated reasons. None of the patients had evidence of abnormalities at the CVJ. Two senior spine surgeons then measured the CMAs of these patients in a blind manner on three separate occasions. The CMA values ranged from 139.0 degrees to 175.5 degrees , with an average value of 158.46 degrees , and a 95% confidence interval from 144.8 degrees to 172.1 degrees . Overall, the CMA had excellent intraobserver repeatability and interobserver reliability. The CMA also had excellent intraobserver repeatability based on both the age and gender of the patients (P = 0.87 and 0.93, respectively). At the same time, the CMA also demonstrated excellent interobserver reliability based on gender (P = 0.97), while good interobserver reliability based on patients age (P = 0.23). No significant correlation between the actual CMA values and the patients' gender (P = 0.17), age (P = 0.058), or spin-echo series used (P = 0.342). This study demonstrated that CMA values obtained from midsagittal T1 MR images were a highly reliable and repeatable measurement. The data reported in this study can be used as baseline parameters for normal individuals

Quantitative data of spinal intervertebral disc deformation is instrumental for investigation of spinal disc pathology. In this study, we employed a combined dual fluoroscopic imaging system and the MR imaging technique to determine the lumbar disc deformation in living human subjects. Discs at L2-3, L3-4 and L4-5 levels were investigated in 8 normal subjects. The geometric deformation of the discs under full body weight loading condition (upright standing) was determined using the supine, non-weightbearing condition as a reference. The average maximum tensile deformation was -21% in compression and 24% in tension, and maximum shear deformation on the disc surface reached 26%. The data indicated that different portions of the disc are under different tensile and shear deformation. Further, discs of L2-3, L3-4 and L4-5 have different deformation behavior under the physiological weightbearing condition. In general, the higher level discs have higher deformation values. The technique used in this study can be used to investigate the deformation behaviors of diseased discs as well as the efficacy of different surgical modalities at restoring normal disc deformation patterns

The study design included an in vivo laboratory study. The objective of the study is to quantify the kinematics of the lumbar spinous processes in asymptomatic patients during un-restricted functional body movements with physiological weight bearing. Limited data has been reported on the motion patterns of the posterior spine elements. This information is necessary for the evaluation of traumatic injuries and degenerative changes in the posterior elements, as well as for improving the surgical treatment of spinal diseases using posterior procedures. Eight asymptomatic subjects with an age ranging from 50 to 60 years underwent MRI scans of their lumbar segments in a supine position and 3D models of L2-5 were constructed. Next, each subject was asked to stand and was positioned in the following sequence: standing, 45 degrees flexion, maximal extension, maximal left and right twisting, while two orthogonal fluoroscopic images were taken simultaneously at each of the positions. The MRI models were matched to the osseous outlines of the images from the two orthogonal views to quantify the position of the vertebrae in 3D at each position. The data revealed that interspinous process (ISP) distance decreased from L2 to L3 to L4 to L5 when measured in the supine position; with significantly higher values at L2-3 and L3-4 compared with L4-5. These differences were not seen with weight-bearing conditions. During the maximal extension, the ISP distance at the L2-3 motion segment was significantly reduced, but no significant changes were detected at L3-4 and L4-5. During flexion the ISP distances were not significantly different than those measured in the MRI position at all segments. Going from the left to right twist positions, the L4-5 segment had greater amounts of ISP rotation, while all segments had similar ranges of translation in the transverse plane. The interspinous process distances were dependent on body posture and vertebral level

STUDY DESIGN: Retrospective case-control study. OBJECTIVE: The purpose of this study was to compare the self-reported outcomes between operatively and nonoperatively treated patients over the age of 65 with adult scoliosis, using 4 distinct self-assessment questionnaires (SRS-22, SF-12, EQ5D, and Oswestry disability index [ODI]) and standard radiographic measurement parameters. SUMMARY OF BACKGROUND DATA: The current spine literature contains no studies that directly compare the self-reported and radiographic outcomes of operatively and nonoperatively treated patients over the age of 65 years with adult scoliosis. METHODS: We retrospectively analyzed the self-reported outcomes of 83 adult scoliosis in patients over the age of 65 years. A total of 34 patients were treated operatively, whereas 49 patients were managed nonoperatively. For each of these patients, standard radiographic measurements were recorded both before and after treatment, and each patient received 4 questionnaires (SRS-22, SF-12, EQ5D, and ODI) that were completed with a minimum of 2-year follow-up from the time the treatment was initiated. The outcomes of both groups were then statistically compared. RESULTS: As compared to the nonoperative group, the operative group reported significantly better self-assessment scores for the EQ5D index, EQ5D Visual Analogue Score, and SRS-22 questionnaires. However, no statistically significant difference between the groups was detected for the ODI, SF-12 Mental Health Component Summary, and SF-12 PCS. Furthermore, the operative group also had a significant improvement in radiographic measurements. CONCLUSION: Adult scoliosis patients over the age of 65 years treated operatively had significantly less pain, a better health-related quality of life, self image, mental health, and were more satisfied with their treatment than patients treated conservatively. However, we found no statistically significant differences in their degree of disability as measured by the ODI as well as physical and mental health by the SF-12 instrument. Preoperative radiographic deformity was not determined to be a significant factor for predicting whether an operative or nonoperative treatment course was chosen

Powers ratio, as assessed on plain radiographs or computed tomography (CT) images, appears to have clinical and prognostic value. To date, the validation of this assessment tool has been limited to a small number of observers at a single site. No study has examined the intraobserver reproducibility and interobserver reliability of the Powers ratio measurement on plain radiographs or CT images among a large cohort of spine surgeons. This type of validation is critical to allow for the broader use of the Powers ratio methodology in research studies and clinical applications. Plain radiographs and spiral CT images of the cervical spine of 32 patients were assessed, and the Powers ratio was determined by five spine surgeons. Each surgeon performed three readings, 7 months apart. In the first round of measurements, the observers used only the Powers' method of instruction. The second and third measurement sets were obtained after an interactive teaching session on the methodology. The order of the images was altered for the second and third set of measurements. The coefficient of variation (Cv) was calculated to determine the intraobserver repeatability and interobserver reliability for each imaging technique. A Bland-Altman plot was then used to assess the agreement between the two imaging techniques. For interobserver reliability, the mean Cv of the Powers ratio was 9.09 and 4.31% for plain radiographs and CT, respectively. The Cv mean value for intraobserver reproducibility averaged 4.95% (range 1.39-9.08) when CT scans were used and 14.17% (range 7.54-34.30) when plain radiographs were used. For intraobserver reproducibility, the lowest and highest Cv mean value of five raters was 1.39 and 9.08% using CT scans and 7.54 and 34.3% using plain radiographs. The Bland-Altman plot, demonstrated that the two methods were in close agreement on the -0.8 and 0.89% interval for limits of agreement (bias +/- 1.96sigma). The intraobserver reproducibility and interobserver reliability of Powers ratio measurement was acceptable (<5%) with CT scans but not with plain radiographs. However, despite the statistically inferior reliability and repeatability, the Bland-Altman plot analysis showed that given the -0.8 and 0.89% limits of agreement, the two methods may be used interchangeably in clinical practice

STUDY DESIGN: Controlled laboratory study. OBJECTIVE: To measure the range of motion of lumbar facet (zygapophyseal) joints in vivo during various functional weight-bearing positions of the upper body. SUMMARY OF BACKGROUND DATA: Determination of normal in vivo motion of the lumbar facet joints remains elusive despite numerous in vitro studies, animal models, and finite element simulations. Alterations in motion of the facet joints have been thought to be associated with various types of lumbar spine pathology including disc degeneration, facet degeneration, and neural impingement. METHODS: Eleven healthy subjects underwent magnetic resonance imaging (MRI) to obtain three-dimensional models of the lumbar vertebrae from L2-L5. Each patient was then scanned using a dual-fluoroscopic imaging system while positioning the body in different postures: maximal forward-backward bend, side-to-side bending, and maximal left-right torsion. This fluoroscopic set-up was then recreated in solid modeling software where positions of the vertebrae were reproduced at each studied posture by matching the MRI-based models to the fluoroscopic images. The kinematics was measured using a Cartesian coordinate system placed in the center of each facet. The facet orientation in the sagittal and transverse plane was also determined. RESULTS: During flexion-extension movements of the trunk, the facet joints rotated primarily along the mediolateral axis (average: 2 degrees -6 degrees ) and were translated in the cephalad caudad direction (average: 2-4 mm). However, during lateral bending and twisting, the facet joints did not rotate or translate in 1 dominant direction. Instead, the resulting motion represented a coupling of rotation and translation in different directions (average: <5 degrees and 3 mm). Further, the kinematic behavior of the facets of the upper lumbar spine (L2-L3 and L3-L4) were similar but different from that of the lower lumbar spine (L4-L5). CONCLUSION: These findings provide baseline information to enable the study of kinematic changes that occur in pathologic conditions of the spine and to determine how these might be affected following surgical intervention