Evaluation of antibody drug delivery efficiency via nebulizer in various airway models and breathing patterns.

BACKGROUND: Nebulizers are commonly used to treat respiratory diseases, which are a major cause of morbidity and mortality. While inhalation therapy with antibodies has been evaluated in preclinical studies and clinical trials for respiratory diseases, it has not yet been approved for treatment. Moreover, there is limited information regarding the delivery efficiency of therapeutic antibodies via nebulizer. METHODS: In this study, the nebulization characteristics and drug delivery efficiencies were compared when immunoglobulin G (IgG) was delivered by five nebulizers using two airway models and five breathing patterns. The study confirmed that the delivered dose and drug delivery efficiency were reduced in the child model compared to those in the adult model and in the asthma pattern compared to those in the normal breathing pattern. RESULTS: The NE-SM1 NEPLUS vibrating mesh nebulizer demonstrated the highest delivery efficiency when calculated as a percentage of the loading dose, whereas the PARI BOY SX + LC SPRINT (breath-enhanced) jet nebulizer had the highest delivery efficiency when calculated as a percentage of the emitted dose. CONCLUSION: The results suggest that the total inspiration volume, output rate, and particle size should be considered when IgG nebulization is used. We, therefore, propose a method for evaluating the efficiency of nebulizer for predicting antibody drug delivery.

Anterior dislodgement of a fusion cage after transforaminal lumbar interbody fusion for the treatment of isthmic spondylolisthesis.

Transforaminal lumbar interbody fusion (TLIF) is commonly used procedure for spinal fusion. However, there are no reports describing anterior cage dislodgement after surgery. This report is a rare case of anterior dislodgement of fusion cage after TLIF for the treatment of isthmic spondylolisthesis with lumbosacral transitional vertebra (LSTV). A 51-year-old man underwent TLIF at L4-5 with posterior instrumentation for the treatment of grade 1 isthmic spondylolisthesis with LSTV. At 7 weeks postoperatively, imaging studies demonstrated that banana-shaped cage migrated anteriorly and anterolisthesis recurred at the index level with pseudoarthrosis. The cage was removed and exchanged by new cage through anterior approach, and screws were replaced with larger size ones and cement augmentation was added. At postoperative 2 days of revision surgery, computed tomography (CT) showed fracture on lateral pedicle and body wall of L5 vertebra. He underwent surgery again for paraspinal decompression at L4-5 and extension of instrumentation to S1 vertebra. His back and leg pains improved significantly after final revision surgery and symptom relief was maintained during follow-up period. At 6 months follow-up, CT images showed solid fusion at L4-5 level. Careful cage selection for TLIF must be done for treatment of spondylolisthesis accompanied with deformed LSTV, especially when reduction will be attempted. Banana-shaped cage should be positioned anteriorly, but anterior dislodgement of cage and reduction failure may occur in case of a highly unstable spine. Revision surgery for the treatment of an anteriorly dislodged cage may be effectively performed using an anterior approach.

Comparison between the accuracy of percutaneous and open pedicle screw fixations in lumbosacral fusion.

BACKGROUND CONTEXT: In pedicle screw fixation, accurate insertion is essential to avoid neurological injury or weak stability. The percutaneous pedicle screw system was developed for minimally invasive spine surgery, and its safety has already been reported. However, the accuracy of percutaneous pedicle screw fixation (PPF) has not been compared with that of the open system to date. PURPOSE: To compare the accuracy of PPF with that of open pedicle screw fixation (open PF) and to investigate the risk factors associated with pedicle wall penetration. STUDY DESIGN/SETTING: A retrospective case series. PATIENT SAMPLE: The study group included 237 patients who underwent posterior pedicle screw fixation between January 2008 and October 2010 at a single institute with a total of 1,056 pedicle screw fixations completed. One hundred and twenty-six patients with 558 screws underwent open PF and 111 patients with 498 screws underwent PPF. OUTCOME MEASURES: Postoperative computerized tomography, including sagittal and coronal reformatted images. METHODS: Consecutive surgeries with either conventional open PF or PPF for anterior lumbar interbody fusion or transforaminal lumbar interbody fusion were performed. The open pedicle screw employed was from the WSH system (Winova, Seoul, Korea), and the two percutaneous pedicle screw systems were the Sextant (Medtronics, Minneapolis, MN, USA) and the Viper systems (DePuy Spine, Raynham, MA, USA). Computed tomography images were evaluated to determine pedicle wall penetration after operation. Severity was classified as mild (<3 mm), moderate (3-6 mm), and severe (≥6 mm), and the direction was assessed as medial, lateral, inferior, and superior. RESULTS: Pedicle wall penetration occurred in 75 patients (13.4%) in the open PF group and 71 patients (14.3%) in the PPF group and was not statistically different between the groups (p=.695). Assessment of the severity of the pedicle wall penetration revealed that minor penetration was the most common (open PF group, 9.7%; PPF group, 10.6%), although the distribution of the degree of severity was not statistically different between the groups (p=.863). A relatively higher incidence of lateral penetration was observed in the open PF group (66.7% vs. 43.7%), whereas medial, superior, and inferior penetrations were higher in the PPF group (p=.033). Other parameters such as age, sex, surgical method, and surgeon factors did not influence the penetration rate, but bone mineral densitometry negatively correlated with the penetration. CONCLUSIONS: Pedicle wall penetration during screw fixation was not different between the open PF and PPF groups. The lateral, paraspinal, muscle-splitting approach seems to lessen medial wall penetration, especially in the S1 vertebra. Distribution of the direction of penetration differs between the groups, with lateral wall penetration being more prominent in the open PF group. Careful placement of pedicle screws is necessary for a stronger construct because of the high incidence of penetration.

Factors affecting clinical outcomes in treating patients with grade 1 degenerative spondylolisthesis using interspinous soft stabilization with a tension band system: a minimum 5-year follow-up.

STUDY DESIGN: Retrospective clinical study. OBJECTIVE: To explore the factors influencing the clinical outcomes and motion-preserving stabilization after interspinous soft stabilization (ISS) with a tension band system for grade 1 degenerative spondylolisthesis (DS). SUMMARY OF BACKGROUND DATA: Despite increasing recognition of the benefits of dynamic stabilization systems for treating lumbar degenerative disorders, the factors affecting the clinical and radiological outcomes of these systems have rarely been identified. METHODS: Sixty-five patients (mean age, 60.3 years) who underwent ISS with a tension band system between 2002 and 2004 were analyzed. The mean follow-up period was 72.5 months. The patients were divided according to the postsurgical clinical improvements into the optimal (n = 44) and suboptimal groups (n = 21), and the radiological intergroup differences were analyzed. Multiple linear regression analysis was performed to determine the impact of the radiological factors on the clinical outcomes. RESULTS: Significant intergroup differences were observed on the follow-up clinical examination. Radiologically, total lumbar lordosis (TLL) and segmental lumbar lordosis (SLL) were significantly improved only in the optimal group, resulting in significant intergroup differences in TLL (P = 0.023), SLL (P = 0.001), and the L1 tilt (P = 0.002). All these measures were closely associated with postoperative segmental lumbar lordosis, which also was the most influential radiological variable for the clinical parameters. CONCLUSION: In the patients with grade 1 DS, the back pain relief and functional improvement following ISS were affected by the improvements in the sagittal spinal alignment through the achievement of segmental lumbar lordosis. ISS can be an alternative treatment to fusion surgery for grade 1 DS in patients who do not require fixation or reduction.

A comparison of unilateral and bilateral laminotomies for decompression of L4-L5 spinal stenosis.

STUDY DESIGN: A retrospective review of clinical and radiographic data was performed at a single institution. OBJECTIVES: To compare clinical and radiologic outcomes between unilateral and bilateral laminotomies for bilateral decompression in patients with L4­L5 spinal stenosis. SUMMARY OF BACKGROUND DATA: Laminotomy has been shown to be comparable with laminectomy with the advantage of potentially maintaining more stability by preserving more of the osseous structures. However, the comparison between unilateral and bilateral laminotomies is available only for short-term follow-up. METHODS: Fifty-three patients at one institution having decompressive surgery for L4­L5 spinal stenosis, including grade 1 degenerative spondylolisthesis without instability, were entered into this study with a minimum of 3-year follow-up. Clinical outcomes were assessed with visual analog scale for back and leg pain and the Oswestry disability index. Radiographic measurements were performed and included translational motion, angular motion, and epidural cross-sectional area. RESULTS: The average age of the patients was 62.4 years (range: 31­82). The mean follow-up period was 49.3 months (range: 40­61). Clinical outcomes and complication rates were similar in both groups. Intraoperative blood loss and operative time were less in the unilateral laminotomy group. Radiographically, the amount of increased translational motion was significantly increased in the bilateral laminotomy group (P 0.012), but the amount of increased angular motion was not significantly different (P 0.195) between the two groups. Postoperative radiographic instability was detected more frequently in bilateral laminotomy group than in the unilateral group, without statistical significance. CONCLUSIONS: Both unilateral and bilateral laminotomies provide sufficient decompression of spinal stenosis and excellent pain reduction. However, unilateral laminotomy can be performed with shorter operative times and less blood loss. Radiologically, the use of a unilateral laminotomy induces less translational motion increase after surgery; thus, it may reduce the risk of late instability when compared with a bilateral laminotomy.

Effect of lumbar angular motion on central canal diameter: positional MRI study in 491 cases.

BACKGROUND: Lumbar spinal stenosis is a common problem that is receiving attention with the advent of novel treatment procedures. Prior positional MRI studies demonstrated lumbar canal diameter changes with flexion and extension. There have not been any studies to examine the amount of spinal canal diameter change relative to the amount of angular motion. The purpose of this study was to evaluate the correlation between the lumbar canal diameter change and the angular motion quantitatively. METHODS: Positional MRI (pMRI) images for 491 patients, including 310 males and 181 females (16 years-85 years of age), were obtained with the subjects in sitting flexion 40 degree, upright, and with extension of 10 degrees within a 0.6 T Positional MRI scanner. Quantitative measurements of the canal diameter and segmental angle of each level in the sagittal midline plane were obtained for each position. Then the diameter change and angular motion were examined for correlation during flexion and extension with linear regression analysis. RESULTS: The lumbar segmental angles were lordotic in all positions except L1-2 in flexion. The changes of canal diameters were statistically correlated with the segmental angular motions during flexion and extension (P < 0.001). The amount of canal diameter change correlated with the amount of angular change and was expressed as a ratio. CONCLUSIONS: Positional MRI demonstrated the amount of spinal canal diameter change that was statistically correlated with the segmental angular motion of the spine during flexion and extension. These results may be used to predict the extent of canal diameter change when interspinous devices or positional changes are used to treat spinal stenosis and the amount of increased canal space may be predicted with the amount of angular or positional change of the spine. This may correlate with symptomatic relief and allow for improved success in the treatment of spinal stenosis.

Interspinous ligamentoplasty in the treatment of degenerative spondylolisthesis: midterm clinical results.

OBJECT Pseudarthrosis and adjacent-segment degeneration remain problems after fusion surgery. To overcome these complications, many dynamic stabilization methods have been developed. This study was conducted to elucidate the midterm results on the effectiveness of interspinous ligamentoplasty (ILP) to treat degenerative spondylolisthesis. METHODS Thirty-two consecutive surgeries involving decompression and ILP were performed by 2 surgeons at the authors' institution during 2001 and 2002. Nine patients were excluded from the study because of inadequate follow-up or radiological data, leaving a study population of 23 patients with a mean duration of follow-up of 64.6 months (range 60-77). All the patients had symptomatic spinal stenosis and Grade 1 spondylolisthesis at L4-5 level without foraminal stenosis and deformity. Clinical outcomes were evaluated by visual analog scale (VAS) for back and leg pain and the Oswestry Disability Index (ODI). Radiological measurements included segmental lordosis, total lumbar lordosis, posterior disc height, anterior slippage, angular motion, translational motion, and facet degeneration grade. Eighteen patients who had undergone bilateral laminotomy alone were included as a Control Group. RESULTS Twenty-two of the 23 patients who underwent ILP returned to their active daily lives. Symptomatic instability was less common in the ILP Group than in the Control Group (4.3% vs 27.8%). The mean postoperative VAS leg scores, VAS back scores, and ODI scores at final follow-up were significantly improved in both groups, in comparison to preoperative scores; however, the mean difference in ODI scores was significantly greater in the ILP group (29.3% vs 16.6%, p = 0.049). In radiological analysis, segmental and total lordoses were significantly increased in the ILP Group. In both groups slippage increased, disc height decreased, and angular motion was maintained, but translational motion decreased with statistical significance in the ILP Group, whereas it increased in the Control Group. Radiological instability was observed in 3 patients in the ILP Group, and 9 in the Control Group (significant between-groups difference, p = 0.016). CONCLUSIONS Interspinous ligamentoplasty is a good option treating patients with Grade 1 degenerative spondylolisthesis requiring surgery. It is less invasive and effectively stabilizes the unstable spine with a relatively small incidence of postoperative instability. Interspinous ligamentoplasty provides satisfactory clinical and radiological results at midterm follow-up.

Spinopelvic alignment after interspinous soft stabilization with a tension band system in grade 1 degenerative lumbar spondylolisthesis.

STUDY DESIGN: Retrospective clinical study. OBJECTIVE: The purpose of this study was to examine the changes in spinopelvic alignment after interspinous soft stabilization (ISS) with a tension band system and to identify the lumbosacral parameters related to those changes and to determine their impact on the clinical outcomes compared with posterior lumbar interbody fusion (PLIF) in patients with low-grade degenerative spondylolisthesis (DS). SUMMARY OF BACKGROUND DATA: The sacropelvic morphometric changes after fusion surgery have received much research attention. However, few reports have addressed the issue after use of dynamic or soft stabilization systems. METHODS: From April 2001 to November 2003, 45 patients presenting with grade 1 DS with stenosis underwent either ISS with a tension band system (ISS group) or PLIF with pedicle screw fixation (PLIF group). The mean follow-up period was 76.8 months. Three pelvic parameters, the sacral slope (SS), pelvic tilt (PT), and pelvic incidence, were investigated to address the sacropelvic morphometric change. Clinical outcomes were assessed using the visual analog scale score, the Oswestry Disability Index, and the patient's satisfaction index. RESULTS: Both groups showed significant improvements in all of the clinical outcomes, with no significant differences between groups. In the ISS group, the SS increased and PT decreased, whereas in the PLIF group, the SS decreased and PT increased, resulting in pelvic anteversion and retroversion, respectively, with significant intergroup differences in SS and PT (SS: P = 0.047; PT: P = 0.01). The positive association of lumbar lordosis with SS (r = 0.448) and its negative association with PT (r = -0.674) in the respective groups indicate the influence of changes in lumbar lordosis on pelvic positional changes. Significant correlations between follow-up segmental lumbar lordosis and the visual analog scale score for leg pain (r = -0.685) and Oswestry Disability Index score (r = -0.425) were found in the ISS group alone. CONCLUSION: Segmental lordotic change after ISS with a tension band system was the possible decisive factor in the development of pelvic anteversion while maintaining sagittal lumbar balance; lack of lumbar lordosis led to compensatory pelvic retroversion in the PLIF group. Considering the comparable clinical results with PLIF surgery and the achievement of physiologic sagittal spinopelvic balance, the ISS procedure can be a feasible alternative to fusion surgery in patients with grade 1 DS with stenosis.

A Comparison of fixed-hole and slotted-hole dynamic plates for anterior cervical discectomy and fusion.

STUDY DESIGN: A retrospective review of clinical data at 1 institution was performed. OBJECTIVES: To compare the clinical and radiologic outcomes between fixed-hole and slotted-hole dynamic cervical plates. SUMMARY OF BACKGROUND DATA: Anterior cervical plating is commonly used to increase stability and promote spinal fusion. Two techniques, fixed-hole dynamic plating that uses variable angled screws and slotted-hole dynamic plating that permits sliding, are viable options, but there have been no clinical studies comparing their effectiveness. METHODS: Fifty-six patients at 1 institution having anterior cervical discectomy and fusion for degenerative disease over a 5-year period were entered into this study. Surgeries were performed with 1 of the dynamic plates for 1 to 3 levels. For the slotted-hole dynamic plate group, a slotted-hole plate was used (ABC, Aesculap, Tuttlingen, Germany or C-tek, Biomet, Parssipany, NJ) and for the fixed-hole dynamic plated group, a variable angled screw was used (C-tek, Biomet, Parssipany, NJ). Radiographic measurements included were graft subsidence, lordotic angle change from each end plate of fusion construct, and implant translation from end plates after a minimum of 12 months follow-up. Fusion state and clinical outcome using Odom's criteria were also evaluated. RESULTS: Demographics were not different among patient populations. The average age of the patients was 51.0 years (range: 27 to 77 y). Mean follow-up period was 20.6 months (range: 12 to 41 mo). Slotted-hole dynamic plates were used for 29 patients (ABC plate, 17; C-tek plate, 12) and fixed-hole dynamic plates for 27 patients. Clinical outcomes and pseudoarthrosis rates were similar for both types of plates. Radiographic measurements showed a statistically significant increased incidence of graft subsidence and implant translation with the slotted-hole dynamic plates. Loss of lordosis was also greater in the slotted-hole dynamic plated group, although the difference was not statistically significant. CONCLUSIONS: The use of a fixed-hole dynamic plate is more favorable in regards to graft subsidence and implant translation in the follow-up period, although clinical outcome and fusion rates are similar in patients with either the fixed-hole or slotted-hole dynamic plates.

Reliability of a magnetic resonance imaging-based grading system for cervical intervertebral disc degeneration.

STUDY DESIGN: This was a radiographic reliability study of a novel grading system for cervical intervertebral disc degeneration. OBJECTIVES: This study aimed to develop and test the reliability of a reproducible grading system for cervical intervertebral disc degeneration on the basis of the routine magnetic resonance imaging (MRI). SUMMARY OF BACKGROUND DATA: Cervical disc degeneration is common after middle age, and the morphology of cervical disc degenerative disease has often been studied using MRI. There are few specific MRI-based grading systems for cervical intervertebral disc degeneration despite the clinical importance of this problem. This study proposes a novel reproducible grading system for cervical disc degeneration and demonstrates the reliability of this classification scheme. METHODS: A grading system for cervical intervertebral disc degeneration was developed based on relevant previous literature. MRI grading of 300 cervical intervertebral discs using T2-weighted sagittal images was performed by 4 spinal surgeons (observers) in a blinded fashion. Intraobserver and interobserver reliabilities were assessed by calculating kappa statistics. RESULTS: Grade I degeneration was observed in 27 discs (9.0%); grade II, in 56 (18.7%); grade III, in 124 (41.3%); grade IV, in 67 (22.3%); and grade V, in 26 (8.7%) discs. Kappa coefficients for intraobserver and interobserver agreements ranged from substantial to excellent (intraobserver, 0.907 to 0.950 and interobserver, 0.730 to 0.826). Complete agreement was obtained, on an average, in 72.1% of the discs. A difference of 1, 2, and 3 grades was observed in 22.4%, 3.3%, and 0.2% discs, respectively. CONCLUSIONS: This grading system is comprehensive and easily applicable with sufficient reproducibility. It can be used as a common nomenclature for research and discussions.

A porcine model of intervertebral disc degeneration induced by annular injury characterized with magnetic resonance imaging and histopathological findings. Laboratory investigation.

OBJECT: Appropriate animal models of disc degeneration are critical for the study of proposed interventions as well as to further delineate the degenerative process. The purpose of this study was to characterize a porcine model for disc degeneration confirmed on magnetic resonance (MR) imaging studies and histological analysis. METHODS: Twelve miniature pigs were used (weight 48-65 kg) to study degeneration in the lumbar spine. Under fluoroscopic guidance, the disc was percutaneously punctured with a 3.2-mm-diameter trephine to a 5-mm depth into the annulus fibrosus. Control and experimental levels were randomized among 6 levels in the lumbar spine. The unlesioned spinal levels were used as controls and were compared with lesioned levels. Magnetic resonance imaging grading and disc height were serially recorded preoperatively, and at 5, 8, 19, 32, and 39 weeks postoperatively. The animals were killed in groups of 3 at 7, 18, 32, and 41 weeks postinjury, and the discs were examined histopathologically. RESULTS: Consistent, sequential, and progressive degeneration of the annular injury was observed on MR imaging and histopathological studies from the time of injury to the final time point. The disc height and the disc height index also sequentially decreased from the time of the injury in a consistent manner. The uninjured control levels did not show any progressive degeneration and maintained their normal state. CONCLUSIONS: Based on MR imaging and histopathological findings, the authors demonstrated and characterized a reliable model of sequential disc degeneration in miniature pigs with percutaneous injury to the annulus fibrosus. In the early stages, as soon as 5 weeks after injury, significant disc degeneration was seen on MR imaging grading with decreases in disc height. This degeneration did not improve by the final time point of 39 weeks.

The effects of the degenerative changes in the functional spinal unit on the kinematics of the cervical spine.

STUDY DESIGN: The sagittal kinematics of the cervical spine was evaluated using kinematic magnetic resonance imaging (kMRI). OBJECTIVE: To investigate the effect of degenerative changes in the functional spinal unit on cervical kinematics by using kMRI. SUMMARY OF BACKGROUND DATA: Few studies have, thus far, by using MR images, described the contribution of degenerative changes in the functional spinal unit to cervical kinematics; however, the exact cervical kinematics remains uncertain. METHODS: A total of 289 consecutive symptomatic patients underwent dynamic cervical MRI in flexion, neutral, and extension postures. All digital measurements and calculations of the variations in segmental angular motion were automatically performed by an MR analyzer using true MR images with 77 predetermined points marked on each image. Each segment was assessed based on the extent of intervertebral disc degeneration (Grades 1-3) and cervical cord compression (groups A-C) observed on T2-weighted MR images. RESULTS: The segmental mobility of the segments with severe cord compression and moderate disc degeneration tended to be lower than that of the segments with severe cord compression and severe disc degeneration, and a significant difference was observed in the segmental mobility of the C5-C6 segment. Moreover, in all segments with moderate disc degeneration, the segmental mobility was significantly reduced in the presence of severe cord compression, as compared with no compression. However, in segments with severe disc degeneration, no significant differences were observed between the segmental mobility of the cord compression groups. CONCLUSION: Our results suggest that cervical cord compression may cause deterioration of cervical cord function and kinematic changes in the cervical spine. We hypothesize that the spinal cord may potentially protect its functions from dynamic mechanical cord compression by restricting segmental motion, and these mechanisms may be closely related to the intervertebral discs.

A minimally invasive technique for L5-S1 intraforaminal disc herniations: microdiscectomy with a tubular retractor via a contralateral approach.

Surgical treatment of intraforaminal disc herniations at the L5-S1 level is technically demanding. The 2 most commonly used procedures involve either a medial or lateral ipsilateral approach and often require a partial or even complete facet resection, which may in turn result in vertebral instability and/or back pain, as well as, in some cases, a fusion or stabilization procedure. In this report, the authors present a new minimally invasive technique for the treatment of L5-S1 intraforaminal disc herniations. Using this technique, which involves tubular retractors and an operative microscope to approach the neural foramen from the contralateral side, the authors could easily visualize and remove the herniated disc material and perform a thorough microdiscectomy with minimal resection of osseous and ligamentous structures. To illustrate this new minimally invasive technique for the treatment of intraforaminal disc herniations at L5-S1, they describe the cases of 2 patients who underwent the procedure and in whom successful results were achieved.

Kinematic analysis of the relationship between the grade of disc degeneration and motion unit of the cervical spine.

STUDY DESIGN: Kinetic MRIs of cervical spines were obtained and analyzed according to the amount of motion and the degenerative grade of the intervertebral disc. OBJECTIVE: To define the relationship between the grade of disc degeneration and the motion unit of the cervical spine and elucidate changes in the role of each cervical spine unit during flexion-extension motion caused by degeneration. SUMMARY OF BACKGROUND DATA: Degenerative changes in the cervical disc occur with age. The correlation between the degree of cervical disc degeneration and extent of cervical spine mobility has not yet been determined. The effect of degeneration on the overall motion of the functional spinal unit also remains undefined. METHODS: We studied 164 patients with symptomatic neck pain. The cervical intervertebral discs were graded by spine surgeons according to the degenerative grading system (Grades I to V). All radiologic data from kinetic MRIs were recorded on a computer for subsequent measurements. All measurements and calculations for translational motion and angular variation of each segment were automatically performed by a computer analyzer. RESULTS: The translational motion in discs with Grade II degeneration (mild degeneration) increased to Grade III degeneration (higher degeneration). However, the translational motion and angular variation significantly decreased for the Grade V (severe degeneration). For patients with relatively low grades of degeneration, Grades I and II discs, the C4-C5 and C5-C6 segmental units contributed the majority of total angular mobility of the spine. However, for the severely degenerated segments, Grade V discs, the contributions of the C4-C5 and C5-C6 U significantly decreased. CONCLUSION: The changes that occur with disc degeneration progress from the normal state to an unstable phase with higher mobility and subsequently to an ankylosed stage. This study evaluated the contribution of different levels to the changes in overall motion that occur with degeneration.