Volume Of Nucleus Pulposus Research Articles

Comparison of three methods for nucleus pulposus volume measurement in rabbit lumbar spines: a preclinical model for measurement of the effectiveness of prophylactic intervertebral disk fenestration in dogs.

Compare 3 methods of nucleus pulposus (NP) volume measurement using the rabbit lumbar spines as a preclinical model to determine the effectiveness of prophylactic intervertebral disk fenestration in dogs. Twelve 9-month-old, skeletally mature female entire New Zealand White rabbits weighing between 3.5 to 4.5 kg. NP volume measurements of dissected rabbit lumber spines between L1 and L6 were made and compared using gross measurements, reconstructed MRI images, and water volumetry based on Archimedes' principle. Water volumetry was used as the true gold standard volume measurement in this study. The true volume (mean ± SD) of the nucleus pulposus NP as measured by water volumetry increased caudally from L1/L2 (16.26 ± 3.32 mm3) to L5/L6 (22.73 ± 6.09 mm3). Volume estimates made by MRI were significantly higher than those made using water volumetry at all sites (L1/L2 [P = .044], L2/L3 [P = .012], L3/L4 [P = .015], L4/L5 [P < .001], and L5/L6 [P < .001]). Gross measurements also significantly overestimated volume when compared to water volumetry at all sites; L1/L2 (P = .021), L2/L3 (P = .025), L3/L4 (P = .001), L4/L5 (P < .001), and L5/L6 (P < .001). MRI and gross volume estimates were significantly different at L4/L5 (P = .035) and L5/L6 (P = .030). The findings of this preclinical model might be relevant to veterinary surgeons who perform prophylactic fenestration for which there is no reliable method to determine the amount of NP to be removed. Preclinical ex vivo and in vivo fenestration studies with pre- and postoperative NP volume assessment are required.

Multimodal Applications of 3D-Navigation in Single-Level Minimally Invasive Transforaminal Lumbar Interbody Fusion: Impacts on Precision, Accuracy, Complications, and Radiation Exposure.

Three-dimensional (3D)-navigation in minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is an evolving procedure. It is used not only for its accuracy of pedicle screw fixation but also for other major steps in transforaminal lumbar interbody fusion. Multimodal outcomes of this procedure are very limited in the literature. The purpose of this study was to examine the application of 3D-navigation in minimally invasive transforaminal lumbar interbody fusion (MI-TLIF). Patients who underwent single-level MI-TLIF using 3D-navigation between January 2017 and July 2019 were evaluated for navigation setting time, radiation exposure, volume of nucleus pulposus excised, cage placement, accuracy of pedicle screw placement, and cranial facet-joint violation. One hundred and two patients with a mean age of 60.2 years met the inclusion criteria. The mean presetting time of navigation was 46.65 ± 9.45 minutes. Radiation exposure, fluoroscopy use, and fluoroscopy time were 15.54 ± 0.65 mGy, 4.43 ± 0.87 Gy.cm², and 97.6 ± 11.67 seconds, respectively. The mean amount of nucleus pulposus excised from all quadrants was quantified. The cage was centrally placed in 87 patients, with 95.4% showing a Grade 0 pedicle breach and 94.6% showing Grade 0 cranial facet-joint violation. Registration and setting up 3D-navigation takes additional time. The amount of exposure to the patient is much less compared to routine computed tomography, and, importantly, the operating team is protected from radiation. Navigated MI-TLIF has high rates of accuracy with regard to placement of percutaneous pedicle screws and cages with the added advantage of protection of the cranial facet-joint.

Morphological changes of Intervertebral Disc detectable by T2-weighted MRI and its correlation with curve severity in Adolescent Idiopathic Scoliosis

BackgroundOur previous studies found disproportionate anteroposterior vertebral size is associated with severity of the scoliotic curves in adolescent idiopathic scoliosis (AIS) patients. Subsequent studies showed wedging of vertebral bodies (VB) had less contribution than intervertebral discs (IVD) to the anterior–posterior vertebral column length discrepancy in severe-AIS. However, the exact morphological changes of IVD were not clearly defined. This study aimed to evaluate the morphological and pathological changes of IVD and VB in AIS girls and healthy female controls.MethodsThis study included 33 age-matched female controls and 76 AIS girls with a right-sided thoracic curvature. Wedge angle, height ratio and distance ratio of VB and IVD were measured on the best midline coronal and sagittal planes from reformatted MRI spine. Volumes of VB, IVD and nucleus pulposus (NP) were also evaluated on volumetric images. One-way ANOVA with Bonferroni correction and Pearson correlation tests were used.ResultsThere was significant difference in wedge angle and height ratio of VB and IVD between AIS and controls. In severe-AIS, the position of NP was significantly shifted to the convexity when compared with non-severe AIS and controls. Whereas, the volume of IVD and NP in severe-AIS was found to be significantly smaller. In addition, Cobb angle was significantly correlated with wedge angle and height ratio, and inversely correlated with the volume of NP.ConclusionsIn addition to wedging of VB and IVD, there was significantly reduced volume of IVD and NP in AIS patients with severe curve, insinuating the mechanical effect of scoliosis leads to a compression on both IVD and NP before significant disc desiccation occurs. We postulate that the compression of IVD and NP can contribute to curve progression in severe-AIS, these patients are more prone to disc degeneration in adulthood if no operative treatment is offered. Further longitudinal study on these parameters is still warranted.

Morphological changes of intervertebral disc in relation with curve severity of patients with Adolescent Idiopathic Scoliosis - a T2-weighted MRI study.

The purpose of this study was to evaluate the morphological changes of intervertebral discs (IVD) and vertebral bodies (VB) in AIS girls according to the subgroups with different curve severity by magnetic resonance imaging (MRI). This study included 33 age-matched female controls and 76 AIS girls with a right-sided thoracic curvature. Wedge angle, height ratio and distance ratio of VB and IVD were measured on the best midline coronal and sagittal planes from reformatted MRI spine. Volumes of VB, IVD and nucleus pulposus (NP) were evaluated on volumetric images. One-way ANOVA with Bonferroni correction was used. There was significant difference in wedge angle and height ratio of VB and IVD between AIS and controls. In severe-AIS, the position of NP was significantly shifted to the convexity when compared with non-severe AIS and controls. Whereas, the volume of IVD and NP in severe-AIS was found to be significantly smaller. On top of coronal wedging of VB and IVD, there was significantly reduced volume of IVD and NP in severe-AIS patients, despite T2 signal of IVD was preserved. The current findings indicate that early mechanical effects on the discs and vertebrae in adolescent scoliotic spine is evident on quantitative imaging. Importantly, these patients may be vulnerable to disc degeneration if no operative treatment is prescribed.

Longitudinal characterization of intervertebral disc remodeling following acute annular injury in a rat model of degenerative disc disease

ABSTRACT Objective: Characterize 3D remodeling of the rat intervertebral disc (IVD) following acute annular injury via in vivo micro-computed tomography (µCT), ex vivo contrast-enhanced (CE)-µCT, and histology. Design: Female Lewis rats (N = 4/group) underwent either sham surgery or anterior annular puncture to L3-L4 and L5-L6 (n = 8 IVDs/group) to induce IVD degeneration. Rats were allowed ad libidum cage activity before and after surgery and underwent in vivo µCT scanning at baseline and every 2 weeks post-op for 12 weeks to characterize longitudinal changes in IVD height. At 12 weeks, lumbar spines were dissected and underwent CE-µCT scanning to characterize endpoint glycosaminoglycan distribution and nucleus pulposus (NP) volume ratio. Spines were processed for safranin-O-stained sagittal histology, and IVD degeneration was graded via the Rutges scale. Results: Puncture IVDs exhibited loss of IVD height at all time points from 4 weeks onward compared to Sham—the most severe height loss occurred posteriorly, with significant changes also occurring in the NP and laterally. Puncture IVDs exhibited higher CE-µCT attenuation, indicative of lower glycosaminoglycan content, and reduced NP volume ratio compared to Sham. Histologically, Puncture IVDs had higher Rutges damage scores and exhibited reduced NP cellularity and hydration, disorganized annulus fibrosus (AF) lamellae with evidence of the stab tract, and indistinct AF-NP border compared to Sham. Conclusions: Characterization of the complex, 3D alterations involved in the onset and early progression of IVD degeneration can foster greater understanding of the pathoetiology of IVD degeneration and may inform future studies assessing more sensitive diagnostic techniques or novel therapies.

Morphological characteristics of the kangaroo lumbar intervertebral discs and comparison with other animal models used in spine research.

Animal models are frequently used to elucidate pathomechanism and pathophysiology of various disorders of the human intervertebral disc (IVD) and also to develop therapeutic approaches. Here we report morphological characteristics of the kangaroo lumbar IVDs and compare them with other animal models used in spine research. Twenty-five fresh-frozen cadaveric lumbar spines (T12-S1) derived from kangaroo carcases (Macropus giganteus) of undetermined age were first scanned in a C-Arm X-ray machine. A photograph of the axial section of the disc including a calibrated metric scale was also acquired. The digital radiographs and photographs were processed in ImageJ to determine the axial and sagittal plane dimensions for the whole disc (WD) and the nucleus pulposus (NP) and the mid-sagittal disc height for all the lumbar levels. Our results suggest that the L6-S1 IVD in kangaroos is distinctly large compared with the upper lumbar IVDs. Based on previously published data, human lumbar IVDs are the largest of all the animal IVDs used in spine research, with camelid cervical IVDs being the closest relative in absolute dimensions (llamas: 78% in disc height, 40% in WD volume, and 38% in NP volume). Kangaroo L6-S1 IVD was approximately 51% in height, 20% in WD volume, and 20% in NP volume of the human lumbar IVD. We conclude that morphological similarities exist between a kangaroo and human lumbar IVD, especially with the lima bean shape in the axial plane, wedge shape in the sagittal plane, convexity at the cephalad endplates, and percentage volume occupied by the NP in the IVD. These slides can be retrieved under Electronic Supplementary Material.

Experimental study of annulus fibrosus suture on intervertebral disc biomechanical strength

Objective Applicate annulus fibrosus suture to investigate its effect on the biomechanical strength of intervertebral disc. Methods A total of 36 sheep were underwent retroperitoneal 3 levels exposure of the lumbar spine (L2/3, L3/4, L4/5). Three ways were used in these discs: (1) Did not penetrate into the annulus fibrosus in Group A. (2) Penetrate into the annulus fibrosus in Group B, and didn’t perform annulus fibrosus suture. (3) Penetrate into the annulus fibrosus and perform annulus fibrosus suture in Group C. At 48 weeks after surgery, MRI images were taken and these segments were underwent biomechanical testing to assess the strength of the disc and anulus. Histology was also conducted on these specimens. Results Compared with control group, the lost of intervertebral space height on annulus suture group was (0.90±0.25) mm, and non suture group was (2.41±0.85) mm, the difference was statistically significant (P=0.015). The strength of intervertebral disc on control group was (3.91±0.78) mPa, non suture group was (1.99±0.58) mPa, suture group was (3.07±0.67) mPa; the difference was statistically significant (P=0.004). The nucleus pulposus volume on control group was (0.83±0.60) cm3, suture group was (0.82±0.48) cm3, and non suture group was (0.85±0.42) cm3, the difference was not statistically significant (P=0.058). Conclusion Application of annulus fibrosus suture after resection of nucleus pulposus can effectively maintenance of biomechanical strength, it play a positive role in the repair of annulus fibrosus. Key words: Disc; Annulus fibrosus suture; Biomechanical strength; Annulus fibrous repair; Experimental study

Myelographic and low-field magnetic resonance imaging findings in dogs with presumptive acute hydrated non-compressive nucleus pulposus extrusion

MRI is considered gold standard for the diagnosis of presumptive acute hydrated non-compressive nucleus pulposus extrusions (AHNCNPE). This retrospective study describes the myelographic findings in dogs with AHNCNPE diagnosed by...

Comparison of Adjacent Segment Degeneration After Nonrigid Fixation System and Posterior Lumbar Interbody Fusion for Single-Level Lumbar Disc Herniation: A New Method of MRI Analysis of Lumbar Nucleus Pulposus Volume

ABSTRACTPurpose: To evaluate the influence of a nonrigid fixation system and posterior lumbar interbody fusion on adjacent intervertebral disc degeneration by using MRI analysis of lumbar nucleus pulposus volume for single-level lumbar disc herniation. Materials and Methods: We selected 112 patients who underwent nonrigid fixation (17 men and 44 women) or posterior lumbar interbody fusion (13 men and 38 women) for this retrospective study. Based on the T2-weighted magnetic resonance imaging (MRI) scans taken preoperatively, and 6, 12, and 24 months after surgery, the nucleus pulposus in the upper segments of the operated level was considered an ellipsoid, and their volumes were measured respectively and then compared between the two groups. Results: The posterior lumbar interbody fusion group had significantly lower lumbar nucleus pulposus volume than the nonrigid fixation group at 12 (4.04 ± 1.42 vs. 5.25 ± 1.47 mm3) and 24 months (4.16 ± 0.89 vs. 5.06 ± 1.23 mm3), and had the highest nucleus pulposus. Meanwhile, the h value in the posterior lumbar interbody fusion group was notably smaller than the preoperative level at 12 (0.46 ± 0.03 vs. 0.55 ± 0.05 mm) and 24 months (0.44 ± 0.03 vs. 0.55 ± 0.05 mm). Conclusions: MRI analysis of lumbar nucleus pulposus volume is a new and quantitative method of analysis, which is a considerable method and contributes to the detection of severe intervertebral disc degeneration. Based on this new method, nonrigid fixation demonstrates excellent outcomes on the adjacent segment in comparison with posterior lumbar interbody fusion.

Influence of isobar ttl dynamic internal fixation system on adjacent segment degeneration by mri measurement of lumbar nucleus pulposus volume

?To investigate the influence of ISOBAR TTL dynamic internal fixation system on degeneration of adjacent intervertebral disc by MRI measurement of lumbar nucleus pulposus volume in treating lumbar degenerative disease after operation. ?Between March 2010 and October 2011, 34 patients with lumbar intervertebral disc herniation (23 cases of paracentral type and 11 cases of lateral type) underwent operation with ISOBAR TTL dynamic internal fixation system for fixation of single segment, and the clinical data were analyzed retrospectively. There were 20 males and 14 females, aged 39-62 years (mean, 47.5 years). The disease duration was 6-18 months (mean, 14 months). Involved segments included L4, 5 in 21 cases and L5, S1 in 13 cases. The X-ray films and MRI images were taken at 6, 12, 18, 24, 36, and 48 months after surgery. Based on X-ray films, the height of intervertebral space was measured using angle bisectrix method. The nucleus pulposus volume was measured based on the MRI scan. The postoperative change of nucleus pulposus volume and intervertebral disc height were used to evaluate the influence of ISOBAR TTL system on degeneration of adjacent intervertebral disc nucleus pulposus. ?Thirty patients were followed up 48 months. The height of intervertebral space showed no significant difference between at pre-and post-operation (P>0.05). The nucleus pulposus volume increased after operation, showing no significant difference at 6, 12, and 18 months when compared with preoperative value (P>0.05), but significant difference was found at 24, 36, and 48 months when compared with preoperative value (P<0.05). The height of nucleus pulposus increased after operation but the width was decreased; the values showed no significant difference at 6, 12, and 18 months when compared with preoperative ones, but showed significant difference at 24, 36, and 48 months when compared with preoperative ones (P<0.05). The diameter of nucleus pulposus at 18, 24, 36, and 48 months after operation was significantly langer than that at preoperation (P<0.05). ?ISOBAR TTL dynamic internal fixation system can prevent or delay the degeneration of intervertebral discs.

Percutaneous Disc Decompression with Nucleoplasty–Volumetry of the Nucleus Pulposus Using Ultrahigh-Field MRI

PurposeTo evaluate changes in nucleus pulposus volume as a potential parameter for the effects of disc decompression.MethodsFifty-two discs (T8 to L1) were extracted from 26 pigs and separated into thoracic (T8 to T11) and thoracolumbar discs (T12 to L1). The discs were imaged using 7.1 Tesla ultrahigh-field magnetic resonance imaging (MRI) with acquisition of axial T2-weighted turbo spin-echo sequences for determination of baseline and postinterventional nucleus pulposus volumes. Volumes were calculated using OsiriX® (http://www.osirix-viewer.com). After randomization, one group was treated with nucleoplasty, while the placebo group was treated with an identical procedure but without coblation current. The readers analyzing the MR images were blinded to the kind of procedure performed. Baseline and postinterventional volumes were compared between the nucleoplasty and placebo group.ResultsAverage preinterventional nucleus volume was 0.799 (SD: 0.212) ml. Postinterventional volume reduction in the nucleoplasty group was significant at 0.052 (SD: 0.035) ml or 6.30% (p<0.0001) (thoracic discs) and 0.082 (SD: 0.042) ml or 7.25% (p = 0.0078) (thoracolumbar discs). Nucleoplasty achieved volume reductions of 0.114 (SD: 0.054) ml or 14.72% (thoracic) and 0.093 (SD: 0.081) ml or 11.61% (thoracolumbar) compared with the placebo group.ConclusionsNucleoplasty significantly reduces thoracic and thoracolumbar nucleus pulposus volumes in porcine discs.

Preparing the Lumbar Intervertebral Disk Space for Interbody Procedures

Cadaveric laboratory study. To quantify and compare automated disk-space preparation with traditional methods. Removal of nucleus pulposus to prepare a disk space for interbody fusion is performed with various techniques. Our aim was to determine the safety and effectiveness of an automated technique in comparison to traditional methods and gauge its expected clinical application. This study was conducted in 2 phases. In the phase 1 safety trial, ''maximal'' force was applied to an automated shaver against cadaveric annulus and endplates until flexion of the shaft caused the blades to bind. This simulated the risk of creating an incidental cortical or annular defect. In phase 2, 27 cadaveric lumbar disk spaces were randomized to traditional or automated preparation techniques through a standard transforaminal lumbar interbody fusion approach. Traditional method comprised the use of paddle shavers, pituitary rongeurs, and curettes. Automated technique involved insertion of an 8-mm paddle shaver, followed by straight and angled hand pieces to remove nucleus pulposus and endplate cartilage. Unintended cortical and annular breaches, preparation time, instrument insertions, percentage area of exposed endplate underlying the nucleus pulposus, and percentage volume of nuclear space cleared were measured and compared. In phase 1, ''maximal'' force applied for 10 seconds produced no full-thickness annular or cortical defects. In phase 2, automated technique produced fewer endplate cortical defects (3 vs. 7) and full-thickness annular breaches (0 vs. 1), required fewer instrument insertions (29 vs. 6; P<0.001), exposed more endplate (65% vs. 52%; P=0.037), and removed more nucleus pulposus volume (83% vs. 59%; P=0.01). Automated shaving decreased instrument insertions and prepared the disk space more effectively, with fewer cortical or annular defects. This technique holds promise for improved outcomes in spinal fusion surgery.

A New Porcine In Vivo Animal Model of Disc Degeneration

In vivo animal study. To describe a new porcine disc degeneration model, and to analyze disc remodeling and degeneration after nucleotomy with special view to the different nucleus pulposus (NP) cell types. Thus far, predominantly smaller animals were used for disc degeneration models; however, such small discs were inappropriate to investigate cell implementation therapies. Though notochordal cells (NCs) are important for disc formation and maintenance, differences in the amount of NCs between human and animal discs have often been neglected. Twenty-four Goettingen minipigs underwent partial nucleotomy with a 16G biopsy cannula, to remove approximately 10% of total NP volume. Animals were followed up for 3, or 24 weeks and analyzed by radiographs, MRIs, (immuno)histology, gene expression analysis, and biomechanical testing. Three weeks after nucleotomy disc height was reduced by 26%, and magnetic resonance imaging signal intensity by 40%. At 24 weeks disc height was decreased by 32%. Increased degenerative changes were found in a histodegeneration score 3 and 24 weeks after nucleotomy, as well as considerable NP scarification after 3 weeks. In controls, cytokeratin-8 immunohistochemistry identified NCs in proximity to chondrocyte-like NP cells at approximately equal ratio. After nucleotomy, NCs were considerably reduced to <10% of total NP cells. Matrix genes were upregulated, except for aggrecan that decreased to 35% of initial values 3 weeks after nucleotomy. Matrix degrading factors (matrix metalloproteinases 13 and 3) were continuously upregulated, whereas transcripts of their inhibitors (tissue inhibitors of matrix metalloproteinase 2 and 3) were downregulated. No significant changes in segmental spinal flexibility or bone density were found after nucleotomy. We introduced a new disc degeneration model with relatively large discs that could be used for cell therapeutic approaches. The study gives further information about disc remodeling after nucleotomy and indicates the relevance of an altered cellular composition for the development of disc degeneration.

Influence of surgical approach on the efficacy of the intervertebral disk fenestration: a cadaveric study

To investigate the influence of different approach angles on the amount of nucleus pulposus removed during intervertebral disc fenestration in dogs. Twenty cadavers of beagle dogs were randomly divided into four groups: a control group and three treatment groups in which intervertebral fenestration was performed using either a dorsal, dorsolateral or lateral approach between the 12th thoracic and second lumbar spaces. The volume of nucleus pulposus, the weight of the residual nucleus pulposus and the angle of the working sector were measured. The ratio of the residual nucleus pulposus weight to the nucleus pulposus volume was used to evaluate the efficacy of the performed fenestration. Data were analysed with Kruskal-Wallis analysis of variance between groups on ranks with correction for ties and Bonferroni correction for multiple comparisons. Correlation between ratio and working angle was calculated using a Spearman's rank test (P<0.05). The calculated ratio of nuclear weight to volume was significantly less in the lateral approach group than that in the other groups. The working sector was widest in the dorsolateral approach group, but this did not correlate with efficient fenestration. Using the lateral approach for intervertebral disc fenestration may increase the efficiency of the fenestration procedure.

The Study of the Regeneration of Nucleus Pulposususing Nanofiber-based Scaffold: In Vitro and Animal Study

Purpose : To investigate the potential of nucleus pulposus (NP) regeneration with a nanofiber-based scaffold inserted in the degenerative disc. Materials and Methods : A nanofiber scaffold was fabricated using an electrospinning technique. In the in-vitro study, a total 18 discs with endplates on both sides were obtained from six New Zealand White (NZW) rabbits. A small volume of NP was removed through the hole from the endplate. The specimens were classified into three groups, intact (normal), inserting nanofiber scaffold (nanofiber), and defect (defect) group. The discs were analyzed by MRI scan and histological analysis. Six NZW rabbits were used in the in-vivo study. An annulotomy was performed through the dorsal approach L2-3 and L3-4 disc. A nanofibrous sheet type scaffold was inserted at L3-4. X-ray, MRI and histology analysis were carried out at 4, 8, 12 weeks after surgery. Results : In the in-vitro study, the Nanofiber groups showed higher signal intensity and cell proliferation than the defect groups. In the in-vivo study, the Nanofiber and defect groups showed significant degeneration but there was no significant difference between these groups. Conclusion : Nanofiber scaffold might provide a favorable environment for regenerating disc cells. However, a defect in the annulus fibrosus (AF) might delay the regeneration of the disc cell at the nanofiber group. Therefore, NP regeneration using any scaffold should be examined along with AF regeneration for effective clinical applications.

A method to investigate intervertebral disc morphology from MRI in early idiopathic scoliosis: a preliminary evaluation in a group of 14 patients

The aim of the study was to implement a methodology to quantify in vivo and from magnetic resonance imaging (MRI) the 3D geometrical properties of intervertebral discs (IVDs) in early idiopathic scoliosis with small curves. MRI data were posttreated using a custom-made image processing software to semiautomatically determine the location of disc centres, the location of the nucleus pulposus (NP) and the ratio between the NP volume and the disc volume. MRI was performed in a clinical protocol involving 14 patients having an early idiopathic scoliosis. First, the 3D reconstruction errors were quantified using a reproducibility test (intraoperator and interoperator) in one IVD (L5-S1). The maximal errors in location were 0.79 mm in the frontal plane, 1.84 mm in the sagittal plane and 0.76 mm in the vertical plane. The maximal error in relative volume was 42%. Second, the nucleus migration and relative volume were quantified in discs T5-T6 to L5-S1. No significant relative volume variation was detected. Concerning the disc migration, no significant differences were found in the sagittal and axial planes. In the frontal plane, significant differences were observed at the apex of the scoliotic curvature when the Cobb angle was > or =20 degrees . This innovative study in early scoliosis showed reproducible preliminary results, and its application to improve diagnosis and follow-up will be established in an enlarged patient database.

Torsional Injury Resulting in Disc Degeneration

Torsional injuries may be a precursor to intervertebral disc degeneration, but published rabbit models indicate a latent time of 6 months. We describe a rabbit model in which instability and disc degeneration appear within 3 months. Sixty-five male New Zealand rabbits underwent presurgical irradiation to inhibit heterotopic bone formation. Control animals then underwent either a soft-tissue release or facetectomy and capsulotomy, whereas experimental animals received surgery and an acute 30 degrees torsional lumbar injury. Capsulotomy, as well as facetectomy without torsion, failed to effect disc degeneration. However, the rabbits that received torsion exhibited clear indications of degenerative disc changes (thinning, increased PLA2 levels, and decreased nucleus pulposus volume) within 60-90 days. The observations associate disc degeneration with a destabilizing acute torsional injury.

Use of the holmium yttrium aluminum garnet laser for percutaneous thoracolumbar intervertebral disk ablation in dogs

Objective To evaluate a laser ablation technique for treatment of thoracolumbar intervertebral disk disease in dogs. Design Prospective case series. Animals 33 dogs with signs of recurrent back pain associated with intervertebral disk disease after the initial episode had been managed conservatively for a minimum of 2 weeks. Procedure Spinal needles were placed percutaneously through the annulus fibroses to permit delivery of an optical fiber into the nucleus pulposes of thoracolumbar intervertebral disks T10-11 through L3-4. Fluoroscopy was used to guide needle placement. Holmium yttrium aluminum garnet laser energy then was used to ablate the contents of each selected intervertebral disk. Intervals from time of treatment to time of assessment ranged from 3 to 114 weeks. Results All dogs recovered without complication. Results of follow-up radiography and histologic evaluation indicated that percutaneous holmium yttrium aluminum garnet laser ablation reduces the volume of nucleus pulposus in treated disks. Clinical Implications Used as a clinical treatment and prophylactically, this minimally invasive procedure should prevent further extrusion of partially herniated disks and should reduce the chances of subsequent herniation of disks at other treatment sites. (J Am Vet Med Assoc 1996;208:1263–1267)