Faculty Bibliography

STUDY DESIGN/METHODS:Controlled laboratory study. OBJECTIVE:To evaluate the effect of lumbar degenerative disc diseases (DDDs) on motion of the facet joints during functional weight-bearing activities. SUMMARY OF BACKGROUND DATA/BACKGROUND:It has been suggested that DDD adversely affects the biomechanical behavior of the facet joints. Altered facet joint motion, in turn, has been thought to associate with various types of lumbar spine pathology including facet degeneration, neural impingement, and DDD progression. However, to date, no data have been reported on the motion patterns of the lumbar facet joint in DDD patients. METHODS:Ten symptomatic patients of DDD at L4-S1 were studied. Each participant underwent magnetic resonance images to obtain three-dimensional models of the lumbar vertebrae (L2-S1) and dual fluoroscopic imaging during three characteristic trunk motions: left-right torsion, left-right bending, and flexion-extension. In vivo positions of the vertebrae were reproduced by matching the three-dimensional models of the vertebrae to their outlines on the fluoroscopic images. The kinematics of the facet joints and the ranges of motion (ROMs) were compared with a group of healthy participants reported in a previous study. RESULTS:In facet joints of the DDD patients, there was no predominant axis of rotation and no difference in ROMs was found between the different levels. During left-right torsion, the ROMs were similar between the DDD patients and the healthy participants. During left-right bending, the rotation around mediolateral axis at L4-L5, in the DDD patients, was significantly larger than that of the healthy participants. During flexion-extension, the rotations around anterioposterior axis at L4-L5 and around craniocaudal axis at the adjacent level (L3-L4), in the DDD patients, were also significantly larger, whereas the rotation around mediolateral axis at both L2-L3 and L3-L4 levels in the DDD patients were significantly smaller than those of the healthy participants. CONCLUSION/CONCLUSIONS:DDD alters the ROMs of the facet joints. The rotations can increase significantly not only at the DDD levels but also at their adjacent levels when compared to those of the healthy participants. The increase in rotations did not occur around the primary rotation axis of the torso motion but around the coupled axes. This hypermobility in coupled rotations might imply a biomechanical mechanism related to DDD.

STUDY DESIGN/METHODS:Case-control study. OBJECTIVE:To evaluate the effect of lumbar degenerative disc disease (DDD) on the disc deformation at the adjacent level and at the level one above the adjacent level during end ranges of lumbar motion. SUMMARY OF BACKGROUND DATA/BACKGROUND:It has been reported that in patients with DDD, the intervertebral discs adjacent to the diseased levels have a greater tendency to degenerate. Although altered biomechanics have been suggested to be the causative factors, few data have been reported on the deformation characteristics of the adjacent discs in patients with DDD. METHODS:Ten symptomatic patients with discogenic low back pain between L4 and S1 and with healthy discs at the cephalic segments were involved. Eight healthy subjects recruited in our previous studies were used as a reference comparison. The In Vivo kinematics of L3-L4 (the cephalic adjacent level to the degenerated discs) and L2-L3 (the level one above the adjacent level) lumbar discs of both groups were obtained using a combined magnetic resonance imaging and dual fluoroscopic imaging technique at functional postures. Deformation characteristics, in terms of areas of minimal deformation (defined as less than 5%), deformations at the center of the discs, and maximum tensile and shear deformations, were compared between the two groups at the two disc levels. RESULTS:In the patients with DDD, there were significantly smaller areas of minimal disc deformation at L3-L4 and L2-L3 than the healthy subjects (18% compared with 45% of the total disc area, on average). Both L2-L3 and L3-L4 discs underwent larger tensile and shear deformations in all postures than the healthy subjects. The maximum tensile deformations were higher by up to 23% (of the local disc height in standing) and the maximum shear deformations were higher by approximately 25% to 40% (of the local disc height in standing) compared with those of the healthy subjects. CONCLUSION/CONCLUSIONS:Both the discs of the adjacent level and the level one above experienced higher tensile and shear deformations during end ranges of lumbar motion in the patients with DDD before surgical treatments when compared with the healthy subjects. The larger disc deformations at the cephalic segments were otherwise not detectable using conventional magnetic resonance imaging techniques. Future studies should investigate the effect of surgical treatments, such as fusion or disc replacement, on the biomechanics of the adjacent segments during end ranges of lumbar motion.

BACKGROUND:Little information is available on vertebral motion in patients with discogenic low back pain under physiological conditions. We previously validated a combined dual fluoroscopic and magnetic resonance imaging system to investigate in vivo lumbar kinematics. The purpose of the present study was to characterize mechanical dysfunction among patients with confirmed discogenic low back pain, relative to asymptomatic controls without degenerative disc disease, by quantifying abnormal vertebral motion. METHODS:Ten subjects were recruited for the present study. All patients had discogenic low back pain confirmed clinically and radiographically at L4-L5 and L5-S1. Motions were reproduced with use of the combined imaging technique during flexion-extension, left-to-right bending, and left-to-right twisting movements. From local coordinate systems at the end plates, relative motions of the cephalad vertebrae with respect to caudad vertebrae were calculated at each of the segments from L2 to S1. Range of motion of the primary rotations and coupled translations and rotations were determined. RESULTS:During all three movements, the greatest range of motion was observed at L3-L4. L3-L4 had significantly greater motion than L2-L3 with left-right bending and left-right twisting movements (p < 0.05). The least motion occurred at L5-S1 for all movements; the motion at this level was significantly smaller than that at L3-L4 (p < 0.05). Range of motion during left-right bending and left-right twisting at L3-L4 was significantly larger in the degenerative disc disease group than in the normal group. The range of motion at L4-L5 was significantly larger in the degenerative group than in the normal group during flexion; however, the ranges of motion in both groups were similar during left-to-right bending and left-to-right twisting. CONCLUSIONS:The greatest range of motion in patients with discogenic back pain was observed at L3-L4; this motion was greater than that in normal subjects, suggesting that superior adjacent levels developed segmental hypermobility prior to undergoing fusion. L5-S1 had the least motion, suggesting that segmental hypomobility ensues at this level in patients with discogenic low back pain.

BACKGROUND CONTEXT/BACKGROUND:Despite increasing utilization of surgical spine fusions, a paucity of literature addressing perioperative complications after revision posterior spinal fusion (RPSF) versus primary posterior spine fusion (PPSF) of the thoracic and lumbar spine exists. PURPOSE/OBJECTIVE:To examine demographics of patients undergoing PPSF and RPSF of the thoracic and lumbar spine, assess the incidence of perioperative morbidity and mortality, and determine independent risk factors for in-hospital death. STUDY DESIGN/SETTING/METHODS:Analysis of nationally representative data collected for the National Inpatient Sample (NIS). PATIENT SAMPLE/METHODS:All discharges included in the NIS with a procedure code for posterior thoracic and lumbar spine fusion from 1998 to 2006. OUTCOME MEASURES/METHODS:In-hospital mortality and morbidity. METHODS:Data collected for each year between 1998 and 2006 for the NIS were analyzed. Discharges with a procedure code for thoracic and lumbar spine fusion were included in the sample. The prevalence of patient- as well as health care-related demographics was evaluated by procedure type (primary vs. revision). Frequencies of procedure-related complications and in-hospital mortality were analyzed. Independent predictors for in-hospital mortality were determined. RESULTS:We identified 222,549 PPSF and 12,474 RPSF discharges between 1998 and 2006. Patients undergoing PPSF were significantly younger (51.23 years; confidence interval [CI]=51.16, 51.31) and had lower average comorbidity indices (0.40; CI=0.39, 0.41) than those undergoing RPSF (52.69 years; CI=52.43, 52.97) and (0.44; CI=0.43, 0.45), p<.0001. The incidence of procedure-related complications was 16.02% among RPSF compared with 13.44% in PPSF patients (p<.0001). In-hospital mortality rates after PPSF were approximately twice those of RPSF (0.28% vs. 0.15%, p=.006). Adjusted risk factors for increased in-hospital mortality included PPSF compared with RPSF, male gender, and increasing age. A number of comorbidities, complications, and specific surgical indications increased the risk for perioperative death. CONCLUSION/CONCLUSIONS:Despite being performed in generally younger and healthier patients and having lower perioperative morbidity, PPSF procedures are associated with increased mortality compared with RPSF procedures. The findings of this study can be used for risk stratification, accurate patient consultation, and hypothesis formation for future research.

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

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

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

STUDY DESIGN: A prospective study. OBJECTIVE: To evaluate a novel technique involving an endoscopically assisted anterior release and reduction through an anterolateral retropharyngeal approach with minimum follow-up interval of 31 months. SUMMARY OF BACKGROUND DATA: Irreducible atlantoaxial dislocation is typically a chronic process that requires surgical treatment. However, the current literature does not agree on the single best method of treatment. Previously, the best outcomes have been reported with transoral reduction followed by anterior or posterior fixation. Despite recent innovations, numerous complications remain associated with this approach. METHODS: About 21 consecutive irreducible atlantoaxial dislocation patients with mean age of 32 years underwent endoscopically assisted anterior release and reduction through the anterolateral retropharyngeal approach followed by posterior fixation. The primary pathologies included 8 late odontoid fractures, 7 cases of os odontoideum, 5 with laxity of the transverse ligament, and 1 with atlanto-occipital assimilation with a hypoplastic odontoid. Neurologic status was evaluated using the Japanese Orthopedic Association scoring system. Radiographic parameters including the atlantodental interval (ADI) and cervicomedullary angle were also measured. Follow-up data were obtained for a minimum of 31 months. RESULTS: Anatomic reduction was achieved in 20 cases and near-anatomic reduction in 1 case. All patients had an uneventful recovery with significant improvement in neurologic function and radiographic parameters. No complications were seen. The atlantodental interval was corrected from an average 6.3 mm before surgery to 2.7 mm after surgery (P < 0.01). The cervicomedullary angle was also corrected from an average 109 degrees before surgery to 152 degrees after surgery (P < 0.01). Preoperative muscle strength was on average 3.5 (on scale from 1 to 5) and improved after surgery to 4.5 (P < 0.01). The average preoperative and postoperative Japanese Orthopedic Association scores were 9.6 and 15.5, respectively, indicating 82.8% improvement. CONCLUSION: Endoscopically assisted anterior retropharyngeal release combined with posterior fixation is a safe and effective alternative for the treatment of irreducible atlantoaxial dislocation

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

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