Pulsed Electromagnetic Fields Reduce Interleukin-6 Expression in Intervertebral Disc Cells Via Nuclear Factor-κß and Mitogen-Activated Protein Kinase p38 Pathways.

STUDY DESIGN: This is an in vitro study of bovine disc cells exposed to pulsed electromagnetic fields. OBJECTIVE: The purpose of the present study was to investigate whether pulsed electromagnetic fields (PEMF) effects on the expression of interleukin-6 (IL-6) expression is mediated by two known inflammation regulators, nuclear factor-κB (NF-κß) and phosphorylated mitogen-activated protein kinase p38 (p38-MAPK) signaling pathways SUMMARY OF BACKGROUND DATA.: Inflammatory cytokines play a dominant role in the pathogenesis of disc degeneration. Increasing evidence showed that PEMF, a noninvasive biophysical stimulation, can have physiologically beneficial effects on inflammation and tissue repair. Our previous research shows that PEMF treatment can reduce IL-6 expression by intervertebral disc cells. However, the underlying mechanisms of PEMF action are yet to be uncovered. METHODS: Intervertebral disc nuclear pulposus cells were challenged with interleukin-1α (IL-1α) (for mimicking inflammatory microenvironment) and treated with PEMF simultaneously up to 4 hours. Cells were then collected for NF-κß and phosphorylated p38-MAPK protein detection with Western blot. Additionally, the RelA (p65) subunit of NF-κß was examined with immunostaining for assessment of NF-κß activation. RESULTS: As expected, Western blot results showed that both NF-κß and phosphorylated p38 expression were significantly increased by IL-1α treatment. This induction was significantly inhibited to control condition levels by PEMF treatment. Immunostaining demonstrated similar trends, that PEMF treatment reduced the NF-κß activation induced by IL-1α exposure. CONCLUSION: Our data indicate that the previously-reported inhibitory effect of PEMF treatment on disc inflammation is mediated by NF-κß and phosphorylated p38-MAPK signaling pathways. These results further establish PEMFs anti-inflammatory activity, and may inform potential future clinical uses for management of inflammation associated with disc degeneration. LEVEL OF EVIDENCE: N/A.

Photobiomodulation of extracellular matrix enzymes in human nucleus pulposus cells as a potential treatment for intervertebral disk degeneration.

Intervertebral disc (IVD) degeneration is associated with imbalances between catabolic and anabolic responses, regulated by extracellular matrix (ECM)-modifying enzymes such as matrix metalloproteinases (MMPs) and their endogenous tissue inhibitors of metalloproteinases (TIMPs). Potential contributing factors, such as interleukin (IL)-1ß and tumor necrosis factor (TNF)-α, derived from infiltrated, activated macrophages within IVD tissues, can trigger abnormal production of ECM-modifying enzymes and progression of IVD degeneration. Novel therapies for regulating ECM-modifying enzymes can prevent or ameliorate IVD degeneration. Photobiomodulation (PBM), known to regulate wound repair, exhibits regenerative potential by modulating biological molecules. This study examined the effects of PBM, administered at various wavelengths (630, 525, and 465 nm) and energy densities (16, 32, and 64 J/cm2), on the production of ECM-modifying enzymes in replicated degenerative IVD. Our results showed that PBM selectively inhibited the production of ECM-modifying enzymes in a dose- and wavelength-dependent manner, suggesting that it could be a novel tool for treating symptomatic IVD degeneration.

Influences of different lower cervical bone graft heights on the size of the intervertebral foramen: multiple planar dynamic measurements with laser scanning.

The aim of this study is to evaluate the influences of different bone graft heights on the size of the intervertebral foramen, which will help determine the optimal graft height in clinical practice. Six fresh adult cadavers were used, with the C5-C6 vertebral column segment defined as the functional spinal unit (FSU). After discectomy, the C5/6 intervertebral height was set as the baseline height (normal disc height). We initially used spiral computed tomography (CT) to scan and measure the middle area of the intervertebral foramen when at the baseline height. Data regarding the spatial relationship of C5-C6 were subsequently collected with a laser scanner. Grafting with four different sized grafts, namely, grafts of 100, 130, 160, and 190% of the baseline height, was implanted. Moreover, we scanned to display the FSU in the four different states using Geomagic8.0 studio software. Multiple planar dynamic measurements (MPDM) were adopted to measure the intervertebral foramen volume, middle area, and areas of internal and external opening. MPDM with a laser scanner precisely measured the middle area of the intervertebral foramen as spiral CT, and it is easy to simulate the different grafts implanted. With the increase of the bone graft height, the size of the intervertebral foramen began to decrease after it increased to a certain point, when grafts of 160% of the baseline height implanted. MPDM of the intervertebral foramens with laser scanning three-dimensional (3D) reconstitution are relatively objective and accurate. The recommended optimal graft height of cervical spondylosis is 160% of the mean height of adjacent normal intervertebral spaces.

Evaluation of different laser wavelengths on ablation lesion and residual thermal injury in intervertebral discs of the lumbar spine.

Laser discectomy or nucleotomy is an increasingly important method for less invasive procedures of column, but the ideal kind of laser is still not established. As the wavelength is an important parameter for water absorption, this study was performed to investigate the action of the laser emission in the near infrared (808 to 1908 nm) region in the context of surgical procedures for percutaneous intervertebral disc decompression (nucleotomy). Forty intervertebral discs from pigs lumbar spines were irradiated with laser (λ = 808, 980, 1470 and 1908 nm), 1-s on/off time cycles, for 120 cycles and 10 W of power (808, 980, and 1470 nm) or 240 cycles and 5 W of power (1908 nm), with total power of 1200 J, and subjected to microscopic evaluation through hematoxylin-eosin (HE) staining in order to measure the ablation lesions and the residual thermal injury. Ten other discs were not irradiated and worked as controls. The ablation lesions were measured (in mm) at 1.08 ± 1.25, 1.70 ± 0.63, 2.23 ± 1.02, 1.37 ± 0.39, and 0.94 ± 0.41 (median ± SD) for the control, 808, 980, 1470, and 1908 nm groups, respectively. The difference between 1908 nm and all the other groups was statistically significant (p < 0.05). The residual thermal injury was less evident in 1908 nm laser and sharper in 980 nm laser wavelengths. The laser at a wavelength of 1908 nm was considered the most efficient for the vaporization of the nucleus pulposus, followed by the laser wavelengths of 1470, 808, and 980 nm, and proved to be useful for laser nucleotomy procedure.

Nanostructure changes in the intervertebral discs after experimental laser irradiation.

Laser-induced changes in the intervertebral discs were studied by the method of atomic force microscopy. Alteration of the proximal caudal intervertebral discs was modeled in rats: puncture and exposure to diode laser (2, 3, or 5 W) in constant or pulse regimens or only puncture (control). Nanostructure of disc surface was estimated by surface skewness, root mean square and average roughness, and coefficient of kurtosis. Maximum positive effect and signs of regenerative changes in the surface microstructure of the intervertebral discs were found after exposure to laser (2-3 W) in constant or pulse regimens.

Low level light therapy modulates inflammatory mediators secreted by human annulus fibrosus cells during intervertebral disc degeneration in vitro.

Intervertebral disc degeneration (IVD) is one of the important causes of low back pain and is associated with inflammation induced by interaction between macrophages and the human annulus fibrosus (AF) cells. Low-level light therapy (LLLT) has been widely known to regulate inflammatory reaction. However, the effect of LLLT on macrophage-mediated inflammation in the AF cells has not been studied till date. The aim of this study is to mimic the inflammatory microenvironment and to investigate the anti-inflammatory effect of LLLT at a range of wavelengths (405, 532 and 650 nm) on the AF treated with macrophage-like THP-1 cells conditioned medium (MCM) containing proinflammatory cytokines and chemokines (interleukin-1beta, tumor necrosis factor-alpha, interleukin-6 and 8). We observed that AF cells exposed to MCM secrete significantly higher concentrations of IL-6, IL-8, IL-1ß and TNF-α. LLLT markedly inhibited secretion of IL-6 at 405 nm in a time-dependent manner. Level of IL-8 was significantly decreased at all wavelengths in a time-dependent manner. We showed that MCM can induce the inflammatory microenvironment in AF cells and LLLT selectively suppressed IL-6 and 8 levels. The results indicate that LLLT is a potential method of IVD treatment and provide insights into further investigation of its anti-inflammation effect on IVD.

The effect of gamma irradiation on the biological properties of intervertebral disc allografts: in vitro and in vivo studies in a beagle model.

STUDY DESIGN: An animal experiment about intervertebral disc allograft. OBJECTIVE: To explore the feasibility to decellularize disc allografts treated by 6°Co Gamma Irradiation, and simultaneously, to assess the possibility to make use of the decellularized natural disc scaffold for disc degeneration biotherapy. SUMMARY OF BACKGROUND DATA: Studies of both animal and human disc allograft transplantation indicated that the disc allograft may serve as a scaffold to undertake the physiological responsibility of the segment. METHODS: Experiment in vitro: 48 discs of beagles were harvested and divided randomly into four groups including a control group and three irradiated groups. Immediate cell viability and biomechanical properties of the discs were checked and comparisons were made among these groups. Experiment in vivo: 24 beagles accepted single-level allografted disc treated with different doses of gamma irradiation. Plain X-rays and MRIs were taken before and after surgery. Then, the spinal columns were harvested en bloc from the sacrificed beagles and were examined morphologically. RESULTS: There were significant differences of both the annulus fibrosus and nucleus pulposus immediate cell viabilities among the various groups. There were no obvious differences of the biomechanical properties among the four groups. The disc height and range of motion decreased significantly in all groups as time went on. The observed indexes in irradiated groups were much smaller than those in the control group, but the indexes in 18-kGy group were larger than those in 25-kGy and 50-kGy groups. Both MRI and macroscopic findings showed that the segmental degeneration in the control and 18-kGy group was less severe than that in 25-kGy and 50-kGy groups. CONCLUSION: Gamma Irradiation can decellularize disc allograft successfully to provide natural scaffold for the study of degenerative disc disease therapy, and also can be used as an effective method to produce adjustable animal models.

Effects of pulsed electromagnetic field on intervertebral disc cell apoptosis in rats.

Despite numerous studies on pulsed electromagnetic field (PEMF) application, its effects of PEMF on intervertebral disc (IVD) have not yet been investigated in vivo. Accordingly, the effects of PEMF upon IVD in rats were evaluated through molecular surveys. Rats were divided into six groups: Group I and II were exposed to low and high frequency of PEMF (LF and HF, respectively). Group III and IV underwent induced disc degeneration and were exposed to low and high frequency of PEMF (LF/IDD and HF/IDD, respectively). Group V underwent induced disc degeneration (IDD), and group VI was control. The values of caspase 3, Bax, Bcl-2 and ß-actin band density, as cell apoptotic markers, were obtained from band densitometry. Our results showed that the value of cleaved caspase-3 of cells and Bax/Bcl-2 ratio in IDD group increased significantly compared to the control group (p < 0.001). The value of cleaved caspase-3 and Bax/Bcl-2 ratio decreased significantly in LF/IDD and HF/IDD groups compared to IDD group (p < 0.05). No significant increase was seen in the cell apoptotic markers in the groups just exposed to PEMF compared to the control group. There was also no significant decrease in the Bax/Bcl-2 ratio in HF/IDD and LF/IDD groups compared to the control group. These data suggest that PEMF attenuates degenerative processes in rat's intervertebral discs and has no effect on normal discs. Regulations of the expression of apoptotic proteins may be one of the mechanisms by which PEMF is effective in reduce disc degeneration.

Development of the lumbar lordotic curvature in children from age 2 to 20 years.

STUDY DESIGN: Cross-sectional retrospective study. OBJECTIVE: The purpose of this study was to provide data for the normal values of the lumbar lordotic curvature and segmental angles throughout childhood and to explore the relative contribution of the vertebral bodies and intervertebral discs to the developing lordosis during childhood. SUMMARY OF BACKGROUND DATA: Although early detection of spinal abnormalities such as hyper lordosis or scoliosis is important for preventative intervention, published data regarding normal lordosis development is sparse. The lumbar lordotic curvature is formed by the wedging of the lumbar vertebral bodies and of the intervertebral discs, but there are no data to indicate how these 2 components changes during childhood development. METHODS: Spinal angle parameters were measured on midsagittal reformatted images from 210 abdominal computed tomographic scans of children aged 2 to 20 years. Four different angles were measured: the lordosis angle, the body wedge angle (B), the total segmental angle (S), and the intervertebral disc angle (D). Measurements B, S, and D were taken for each of the 5 lumbar segments. Measurements B and D were used to calculate ΣB, the sum of the lumbar L1-L5 body angles; and ΣD, the sum of the lumbar L1-L5 intervertebral disc angles. Computed tomographic scans were divided into 6 groups according to patients' ages. RESULTS.: The lordosis angle increased from 30° ± 6° in the 2- to 4-year-old group to 44° ± 9° in the 17- to 20-year-old group. The ΣB slightly decreased (less lordotic wedging) with age, whereas the ΣD increased significantly with age. CONCLUSION: Our results indicate that the lordosis angle continues to develop at least until 14 to 16 years of age and that this increase is the result of the increased lordotic wedging of the intervertebral discs. LEVEL OF EVIDENCE: N/A.

Impact of infrared laser light-induced ablation at different wavelengths on bovine intervertebral disc ex vivo: evaluation with magnetic resonance imaging and histology.

BACKGROUND AND OBJECTIVE: Percutaneous laser disc decompression is commonly used to lower high pressure in the nucleus pulposus in degenerative disc diseases. The aim of this study was to investigate the impact of diode laser disc decompression at different wavelengths (980-nm vs. 1,470-nm, i.e., different water absorption characteristics). MATERIALS AND METHODS: To model decompression, a flexible laser quartz fiber inserted into the nucleus pulposus of ex vivo bovine spines using computer-assisted surgical navigation was utilized to vaporize tissue. The same energy (500 J) was delivered using both 980-nm and 1,470-nm wavelength lasers. To determine the different impact of the wavelengths before and after the procedure we evaluated the discs with MRI (T(1), T(2), diffusion maps) and with histopathology. RESULTS: There were no visible changes on T(1) and T(2) maps after 1,470-nm wavelength laser irradiation; however, the 980-nm wavelength caused significant changes on T(1) (decrease) and T(2) (increase) in the vaporization zone at the site of the quartz fiber. Pathological findings showed carbonization and steam-bubble formation in addition to the T(1) and T(2) changes. No significant changes were detected in the value of apparent diffusion coefficient (ADC) measurements in intervertebral disc with the 980-nm wavelength, but significant ADC and T(1) signal increase was detected with the 1,470-nm wavelength when the whole nucleus pulposus was considered. CONCLUSION: The 1,470-nm laser light had an effect in the whole nucleus pulposus and not only at the site of the quartz fiber, whereas with the 980-nm laser irradiation, significant changes were demonstrated only at the application site.

Intradiscal pulsed radiofrequency application following provocative discography for the management of degenerative disc disease and concordant pain: a pilot study.

The development of diagnostic criteria and the use of provocative discography allow identifying the degenerative disc as causative structure for chronic low-back pain. Unfortunately, none of the available interventional treatment options have been demonstrated to be effective over a prolonged period of time for a considerable number of patients. Pathophysiological studies indicate sprouting of sensory nerves and inflammatory processes as underlying pain mechanisms. Pulsed radiofrequency (PRF) treatment in small and larger joints was described to reduce pain and improve healing by stimulating the immunology. Earlier findings of PRF applied in the disc annulus were promising. It is assumed that PRF applied in the nucleus would change the conductivity of nerve endings and provide a clinically relevant pain reduction. The application of the electric field of PRF in the disc may also activate the immune system, thus reducing the inflammation process of chronic pain. Pulsed radiofrequency in the nucleus was studied in 76 patients with discogenic pain confirmed by magnetic resonance imaging and provocative discography. At 3-month follow-up, 38% of the patients had > 50% pain reduction, at 12 month the effect is maintained in 29%. In patients with unsatisfactory pain relief 3 months after the intervention, secondary pain sources may have been revealed. The latter were treated accordingly. Of all patients, 56% had > 50% pain reduction 1 year after first treatment. Our findings suggest that PRF in the nucleus may be considered for patients with proven discogenic pain. A randomized controlled trial to confirm our findings is justified.▪

The influence of Ho:YAG laser irradiation on intervertebral disc cells.

BACKGROUND AND OBJECTIVE: Various types of laser have been reported for percutaneous laser disc decompression (PLDD). The aim of this study was to understand the effects on intervertebral disc cells following Ho:YAG laser irradiation, using a three-dimensional culture model, and consider appropriate irradiation conditions. STUDY DESIGN/MATERIALS AND METHODS: Intervertebral discs from the lumbar spine were obtained from 36 female Japanese white rabbits and processed to obtain isolated cells in three-dimensional cultures. Photoacoustic and photothermal effects were investigated by irradiating three-dimensional cultures with Ho:YAG laser at 27 or 54 J. Residual cell counts after irradiation were estimated based on DNA content according to fluorometric assay. Lactate dehydrogenase levels were also investigated as a marker of damage to cell plasma membranes. Finally, proteoglycan synthesis was measured by rapid filtration assay of (35) S incorporation, as an index of matrix synthesis. RESULTS: Residual cell count tended to be higher in the 27-J group. Plasma membrane damage was higher and remained high longer after irradiation in the 54-J group. Proteoglycan synthesis was higher in the 27-J group than in the 54-J group, with some conditions (e.g., 90 mJ/pulse condition) showing marked activation of proteoglycan synthesis maintained for a long time after irradiation. CONCLUSIONS: Three-dimensional culture models of intervertebral disc cells are useful for clarifying relationships between cell reactions and photoacoustic and photothermal effects after laser irradiation. Total energy is closely related to optimization of irradiation conditions, which may allow optimization of cytoprotection and promotion of matrix synthesis in clinical practice.

Modic vertebral body changes: the natural history as assessed by consecutive magnetic resonance imaging.

STUDY DESIGN: Changes in the vertebral body adjacent to the end plate may be associated with degenerative disc disease. These changes can be separated on magnetic resonance imaging (MRI) and have been described by Modic. It is assumed that these end plate changes represent a process that is progressive. OBJECTIVE: We have retrospectively reviewed patients who had sequential MRI of the lumbar spine to investigate the natural history of Modic vertebral body MRI changes. SUMMARY OF BACKGROUND DATA: Of 36 end plates with Modic type 1 changes in a first MRI, 18 remained the same, 13 progressed to Modic type 2 change, 3 progressed to Modic type 3 changes, and 2 end plates were found to be normal (type 0) on a subsequent MRI. Of the 22 end plates initially reported as Modic type 2 in a first MRI, 18 remained unchanged, none converted to Modic type 3, and 4 converted from Modic type 2 to Modic type 1 on a subsequent MRI. METHODS: Magnetic resonance (MR) images of the lumbar spine of 49 subjects were assessed by a senior spinal surgeon. The lumbar vertebral body adjacent to the end plate was classified by using the Modic system from L1 to S1 inclusive. RESULTS: Of the 36 end plates with Modic 1 changes in the first data set, 18 remained the same; 13 progressed to Modic 2; 3 progressed to Modic 3 changes, and, interestingly, 2 end plates were found to be normal on the repeat scan. Of the 22 end plates initially reported as Modic 2, 18 remained unchanged; none converted to Modic 3 and 4 converted back from Modic 2 to Modic 1. CONCLUSION: Our findings reflect the dynamic nature of pathological changes in the spine and have demonstrated that Modic changes are reversible. They also raise further doubt that these MRI changes should be used as an indicator of clinical symptoms or of surgical outcome.

Pulsed electromagnetic field stimulates cellular proliferation in human intervertebral disc cells.

PURPOSE: The purpose of this study is to investigate the mechanism of cellular proliferation of electromagnetic field (EMF) on human intervertebral disc (IVD) cells. MATERIALS AND METHODS: Human IVD cells were cultured three-dimensionally in alginate beads. EMF was exposed to IVD cells with 650 Ω, 1.8 millitesla magnetic flux density, 60 Hz sinusoidal wave. Cultures were divided into a control and EMF group. Cytotoxicity, DNA synthesis and proteoglycan synthesis were measured by MTT assay, [(3)H]-thymidine, and [(35)S]-sulfate incorporation. To detect phenotypical expression, reverse transcription-polymerase chain reactions (RT-PCR) were performed for aggrecan, collagen type I, and type II mRNA expression. To assess action mechanism of EMF, IVD cells were exposed to EMF with N(G)-Monomethyl-L-arginine (NMMA) and acetylsalicylic acid (ASA). RESULTS: There was no cytotoxicity in IVD cells with the EMF group in MTT assay. Cellular proliferation was observed in the EMF group (p < 0.05). There was no difference in newly synthesized proteoglycan normalized by DNA synthesis between the EMF group and the control. Cultures with EMF showed no significant change in the expression of aggrecan, type I, and type II collagen mRNA compared to the control group. Cultures with NMMA (blocker of nitric oxide) or ASA (blocker of prostaglandin E2) exposed to EMF demonstrated decreased DNA synthesis compared to control cultures without NMMA or ASA (p < 0.05). CONCLUSION: EMF stimulated DNA synthesis in human IVD cells while no significant effect on proteoglycan synthesis and chondrogenic phenotype expressions. DNA synthesis was partially mediated by nitric oxide and prostaglandin E2. EMF can be utilized to stimulate proliferation of IVD cells, which may provide efficient cell amplification in cell therapy to degenerative disc disease.

Effect of 980-nm diode laser and 1064-nm Nd:YAG laser on the intervertebral disc--in vitro and in vivo studies.

OBJECTIVE: Our aim was to histologically evaluate the thermal changes in bovine intervertebral discs caused by 980-nm diode and 1064-nm Nd:YAG lasers. Further aims were to standardize the technique for in vivo animal research and to study its efficacy for clinical practice. BACKGROUND: When conservative methods fail, surgery has so far been the only measure for severe back pain due to disc prolapse and herniation. Recently, the minimally invasive technique of laser disc decompression has become more popular because it has advantages over open surgery in properly selected cases. METHODS: In vitro studies were done with Nd:YAG and diode lasers (1064 and 980 nm, respectively) on bovine intervertebral discs using a bare fiber tip or a focusing lens attached to a fiber tip. These studies were followed by in vivo studies in a canine model using a Nd:YAG laser with a bare fiber tip. Autopsies were done immediately and at 3, 6, 9, and 12 mo after ablation and the histopathology of excised discs was evaluated. RESULTS: Depending upon the depth of ablation and the intensity of charring and carbonization, a standardized energy density and pulse duration were identified. CONCLUSION: Nd:YAG laser with initial delivery of 40-W laser power and a reduced power of 10-15 W thereafter, delivering a total energy density of 1500-2000 J/cm(2) using a bare fiber tip, is recommended for clinical applications.

Effects of laser irradiation on collagen organization in chemically induced degenerative annulus fibrosus of lumbar intervertebral disc.

BACKGROUND AND OBJECTIVE: The number of in vitro experimental studies was carried out with the use of intact tissues to establish a mechanism of laser-tissue interaction. However, in the process of degeneration, both biochemical composition and behavior of the disc were altered drastically. The objective of this study was to evaluate the role of the main matrix components in laser modification of annulus fibrosus (AF) under IR laser irradiation. STUDY DESIGNS/MATERIALS AND METHODS: The samples of AF in a motion segment after hyaluronidase treatment, trypsin digestion and glycation by glyceraldehyde were heated in hydrothermal bath (95 degrees C, 2 min) or irradiated by laser at 1.56 microm. Specimens were imaged by cross-polarization optical coherence tomography (CP-OCT), and then analyzed by differential scanning calorimery (DSC). RESULTS AND DISCUSSION: According to CP-OCT and DSC data non-significant alteration was revealed in AF after hyaluronidase treatment, glycation led to stabilization of annulus collagen and trypsin digestion resulted in a noticeable impairment of collagen fibrils. Laser treatment induced subsequent damages of AF matrix but these damages cannot be explained by laser heating only. The specificity of chemical modification of AF matrix has an influence on a character of collagen network alteration due to IR laser effect. Minimal and maximal alterations are observed for hyaluronidase and trypsin treated samples respectively. Glyceraldehyde fixed samples showed failure of the collagen structure after moderate laser treatment; at the same time thermal denaturation of collagen macromolecules was negligible. We assume that a mechanical effect of laser irradiation plays an important role in laser-induced annulus collagen modification and propose the scheme of physico-chemical process occurring under non-uniform IR laser treatment in AF tissue. CONCLUSION: CP-OCT and DSC techniques allow us to record the alteration of collagen network organization as a result of chemical modification. There were detected significant and specific effects of the biochemical composition and material properties on the response of AF collagen network on laser irradiation. The results go in accordance with our hypothesis that the primary effect of laser influence on collagen network under tension is the mechanical damage of collagen fiber.

IR laser and heat-induced changes in annulus fibrosus collagen structure.

The purpose of this study was to characterize essential changes in the structure of annulus fibrosus (AF) after hydrothermal and infrared (IR) laser treatment and to correlate these results with alterations in tissue state. Polarization-sensitive optical coherence tomography imaging was used to measure collagen birefringence in AF. Differential scanning calorimetry was used as a complementary technique, providing detailed information on thermodynamic processes in the tissue. Birefringence, peak of the denaturation endotherm, and the enthalpy of denaturation (DeltaHm) were determined before and after hydrothermal heat treatment (85 degrees C for 15 min) and non-ablative Er:glass fiber laser exposures on AF in the whole disk (vertebrae-disk-vertebrae complex). Our data have demonstrated quantitative differences between results of laser and hydrothermal heating. Birefringence did not disappear and DeltaHm did not change after treatment in the water bath, but loss of birefringence and a decrease in the enthalpy did occur after laser exposure. These results could be explained by the photomechanical effect of laser irradiation. We suggest that thermo-mechanical stress played a dominant role in the disruption of the collagen network of AF under non-homogeneous laser heating.