Faculty Bibliography

STUDY DESIGN.: Prospective case series and radiographical analysis. OBJECTIVE.: This study aimed to characterize the changes in subaxial alignment after surgical correction of occipitoaxial kyphosis, establish normal parameters, and report on clinical outcomes in a population of patients with chronic atlantoaxial dislocation patients presenting with swan neck deformities. SUMMARY OF BACKGROUND DATA.: Swan neck deformity of the cervical spine is a term used to describe the simultaneous development of both abnormal kyphosis and hyperlordosis malalignments. Currently, there are no published series that discuss their outcomes after treatment and, more specifically, the subsequent changes that occur in the subaxial spine after the correction of the primary deformity in cases of chronic hyperkyphosis at the occipitoaxial segment. METHODS.: This was a prospective clinical and radiographical study in a population of patients with chronic atlantoaxial dislocation presenting with swan neck deformities. C0-C2 and C2-C7 angles were measured using plain radiographs pre- and postsurgery. The relationship between the alignment of the occipitoaxial joint and the subaxial cervical spine was evaluated. Japanese Orthopaedic Society scores were used to assess functional outcomes. RESULTS.: C0-C2 improved from a mean of -14.4 degrees (SD, 9.5 degrees ) preoperatively to a mean of 7.8 degrees (SD, 1.0 degrees ) postoperatively (P = 0.02). C2-C7 changed from a mean of 43 degrees (SD, 2.8 degrees ) to a mean of 18.6 degrees (SD, 11.2 degrees ) postoperatively (P = 0.02). A significant correlation was detected between the changes that occurred in the upper and lower cervical alignments (R = 0.133; P < 0.01). Clinically, the Japanese Orthopaedic Society preoperative scores improved significantly to postoperative (P < 0.01). CONCLUSION.: This study reports the novel auto-correction of subaxial abnormalities after treatment of the primary upper cervical deformity and delineates the relationship between these 2 occurrences, thus demonstrating the reversibility of such complex abnormalities. Furthermore, the clinical outcomes after surgical treatment of swan neck deformities secondary to atlantoaxial dislocation are favorable and associated with a low complication rate.

STUDY DESIGN: : Prospective radiographic analysis. OBJECTIVE: : This study aimed to characterize the relationship between the alignment of the occipitoaxial (OA) and the subaxial spine, establish normal parameters, and to determine the influence of upper cervical spine alignment on subaxial degenerative disc disease (DDD) and clinical outcomes in this population. SUMMARY OF BACKGROUND DATA: : Previous studies reported that the alignments of the upper and lower cervical spine are closely interrelated in patients with atlantoaxial dislocations of a rheumatoid etiology. None have focused on congenital etiologies or included patients with OA kyphosis. The influence of the upper cervical alignment on subaxial (DDD) and outcomes is also unclear. METHODS: : Fifty-eight patients with congenital AAD undergoing surgical reduction and fusion were included. C0-C2 and C2-C7 angles were measured and DDD was assessed using plain radiographs. The relationship between the alignment of the OA joint and the subaxial cervical spine was evaluated, as well as the relationships between the cervical alignment, outcomes, and cervical DDD. RESULTS: : C0-2 improved from a mean of 1.59+/-17.3 degrees preoperatively to a mean of 15+/-9.8 degrees postoperatively (P<0.001). C2-7 changed from a mean of 25.55+/-19.6 degrees to a mean of 14.2+/-14.4 degrees postoperatively (P<0.001). The OA and subaxial alignment were negatively correlated in this population both before (r=-0.84; P<0.001) and after (r=-0.64; P<0.001) surgical treatment. There was an increased incidence of DDD postoperatively (P<0.01), which was positively correlated with the postoperative C0-2 angle (r=0.54; P<0.001), but negatively correlated with the postoperative C2-7 angle (r=-0.79; P<0.001). CONCLUSIONS: : Changes in OA alignment before and after surgery are associated with changes in the subaxial spine. There is a high incidence of postoperative DDD in the subaxial spine that seems to be related to sagittal alignment after surgery.

STUDY DESIGN/METHODS:Analysis of population-based national hospital discharge data collected for the Nationwide Inpatient Sample. OBJECTIVE:To study perioperative outcomes of circumferential spine surgery performed on either the same or different days of the same hospitalization. SUMMARY OF BACKGROUND DATA/BACKGROUND:Circumferential spine fusion surgery has been linked to an increased adjusted risk in perioperative morbidity and mortality compared with procedures involving only 1 site. To minimize these risks, some surgeons elect to perform the 2 components of this procedure in separate sessions during the same hospitalization. The value of this approach is uncertain. METHODS:Data collected between 1998 and 2006 for the Nationwide Inpatient Sample were analyzed. Hospitalizations during which a circumferential noncervical spine fusion was performed were identified. Patients were divided into those who had their anterior and posterior portion performed on the same and those performed on different days of the same hospitalization. The prevalence of patient and health care system-related demographics was evaluated. Frequencies of procedure-related complications and mortality were determined. Multivariate regression models were created to identify whether timing of procedures was associated with an independent increase in risk for adverse events. RESULTS:We identified a total of 11,265 entries for circumferential spine fusion. Of those, 71.2% (8022) were operated in 1 session. Complications were more frequent among staged- versus same-day surgery patients (28.4% vs. 21.7%, P < 0.0001). The incidence of venous thrombosis and adult respiratory distress syndrome also increased among staged candidates, while the trend toward higher mortality (0.5% vs. 0.4%) did not reach significance. In the regression model, staged circumferential spine fusions were associated with a 29% increase in the odds morbidity and mortality compared with same-day procedures. CONCLUSION/CONCLUSIONS:Staging circumferential spine surgery procedures during the same hospitalization offers no mortality benefit and may even expose patients to increased morbidity.

BACKGROUND:The ideal surgical treatment for adult low-grade isthmic spondylolisthesis (ALIS) remains unknown. Isolated anterior and posterior procedures are popular but have resulted in equivocal outcomes, whereas combined anterior and posterior procedures are associated with higher complication rates despite improved outcome. OBJECTIVE:To evaluate the clinical and radiographic outcomes following the treatment of ALIS using a 1-stage posterior approach with posterior decompression and posterolateral arthrodesis combined with an interbody fibular allograft strut. METHODS:Fifteen patients underwent fusion by a single surgeon using our modified technique. Seven patients were female and 8 were male, with a mean age of 48 years. All patients were classified as Meyerding grade II slips and underwent a posterior approach only, a decompressive laminectomy, and a circumferential fusion with the use of a transsacral fibular allograft and a posterolateral instrumented fusion. Postoperative clinical and radiographic evaluations were performed at 3, 6, and 12 months, and then on an annual basis. RESULTS:The average follow-up interval was 61 months. Three complications were seen: a single dural tear, an L5 radiculopathy secondary to a malpositioned pedicle screw, and one patient with urinary retention. The spines of all patients were determined to be fused by the 6-month postoperative visit. All patients returned to their normal activities of daily living. Significant improvements in the visual analog score were seen at all follow-up intervals. CONCLUSION/CONCLUSIONS:Transsacral interbody fibular allograft can be used successfully to supplement a posterolateral instrumented fusion in selected patients with low-grade ALIS.

STUDY DESIGN/METHODS:Controlled experimental study. OBJECTIVE:To evaluate the kinematical effects of X-Stop device on the spinal process at the operated and the adjacent segments before and after X-Stop surgeries during various weight-bearing postures in elderly patients with lumbar spine stenosis. SUMMARY OF BACKGROUND DATA/BACKGROUND:The mechanism of interspinous process (ISP) devices is to directly distract the ISP of the implanted level to indirectly decompress the intervertebra foramen and spinal canal. Few studies have investigated the changes of ISP gap caused by X-Stop implantation using magnetic resonance imaging or radiography, but the effect of X-Stop surgery on the kinematics of spinous processes during functional activities is still unclear. METHODS:Eight patients were tested before and, on average, 7 months after surgical implantation of the X-Stop devices using a combined computed tomography/magnetic resonance imaging and dual fluoroscopic imaging system during weight-bearing standing, flexion-extension, left-right bending, and left-right twisting positions of the torso. The shortest distances of the ISPs at the operated and the adjacent levels were measured using iterative closest point method and was dissected into vertical (gap) and horizontal (lateral translation) components. RESULTS:At the operated levels, the shortest vertical ISP distances (gap) significantly (P<0.05) increased by 1.5 mm during standing, 1.2 mm during left twist, 1.3 mm during extension, and 1.1 mm during flexion, whereas they also increased yet not significantly (P>0.05) in right twist, left bend, and right bend after the X-Stop implantation. The lateral translations were not significantly affected. At both cephalad and caudad adjacent levels, the ISP distances (vertical and horizontal) were not significantly affected during all postures after X-Stop implantation. CONCLUSION/CONCLUSIONS:The findings of this study indicate that implantation of the X-Stop devices can effectively distract the ISP space at the diseased level without causing apparent kinematic changes at the adjacent segments during the studied postures.

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.

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.

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.

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.

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