Introduction: Intra-Discal Electrothermal Therapy (IDET) has been used to treat chronic discogenic low back pain. A novel intradiscal decompression catheter has been developed to reduce local disc bulging in cases of contained prolapse. This new catheter is inserted percutaneously into a disc and advanced under radiographic control into a postero-lateral position targeting the herniation. The decompression catheter uses more focused heating and higher temperatures than previous devices and is intended to provide a local decompression of the disc through a thermally mediated reduction in nuclear volume. The purpose of this study was to investigate changes in internal stress profiles following use of the new catheter.

Methods: Five cadaveric lumbar ‘motion segments’ were dissected from two spines (age 64–84 yrs). Each segment was compressed, normally to 1 kN, while a miniature pressure transducer was withdrawn from posterior to anterior across the mid-sagittal diameter of the disc producing a baseline stress profile. A decompression catheter was inserted into the disc and its position confirmed with plain radiography. The temperature of the catheter was increased to 90°C over a period of 14 minutes. Stress profiles were then repeated.

Results: Stress profiles in three of the five segments showed changes consistent with degenerative change. In these discs stress profiles following ‘treatment’ showed up to a 35% reduction in the magnitude of stress peaks in the posterior annulus. There was very little change in the distribution of stress in the two non-degenerate discs. Stress in the nucleus appeared unchanged in all discs.

Conclusions: Treatment of degenerate discs with the decompression catheter lead to a measurable alteration in annular stress peaks associated with degenerative discs, while non-degenerate discs were unaffected. These preliminary findings of an ongoing study suggest that the novel decompression catheter has a biomechanical effect in certain classes of disc.

Purposes of the study and background: This study tests the hypothesis that it is possible to visualise the cervical spine musculature using ultrasound. The use of diagnostic ultrasound is well established for assessing other anatomical regions; whereas the cervical spine has received little attention. Other available imaging procedures can be resource intensive with recognized risks and do not give an indication of structural detail. Ultrasound has the potential to resolve these inadequacies and would therefore be appealing.

Summary of the methods and the results: 10 healthy volunteers (age range: 21–36 years, 6 females, 4 males) were evaluated using a 8-16MHz linear array transducer (Diasus Dynamic Imaging, UK) and a 16MHz CL15-7 linear array scanhead transducer (Phillips ATL HDI 5000 SonoCT, Netherlands). Subjects were seated with their neck in a neutral position. The transducer was orientated transversely, and initially placed on the thyroid cartilage. Successive images were taken as the transducer was moved laterally across the anterior triangle, over the sternocleidomastoid, into the posterior triangle, ending in the posterior midline. Landmarks, with characteristic ultrasonic appearances, were identified to aid orientation e.g. carotid artery. Both machines produced images that clearly displayed the musculature of the cervical spine. Composite images were obtained of the anterior and posterior aspects of the neck (Figure 1) to provide information regarding the spatial orientation and relationship between the muscles.

Conclusion: This study concludes that modern ultrasound equipment provides cervical spine soft tissue images of a quality suitable for diagnostic applications. It also has the advantages of being a risk free, economic and portable procedure.

Purposes of the study and background: Diagnostic interventional procedures are often performed on patients who suffer from cervical facet joint pain and discogenic pain emanating from the cervical region. These procedures require radiographic imaging to confirm placement of instruments e.g. needles. However, these techniques are unable to provide real-time images hence prolonging the intervention. It would be of benefit to have an imaging tool that is capable of visualising needle insertion in real-time whilst preventing side effects. The purpose of this study was to determine the ultrasonic appearance of cervical facet joints in vivo and describe a standardized transducer position to visualise intervertebral discs and facet joints.

Summary of the methods and the results: 10 healthy volunteers (age range: 21–36 years, 6 females, 4 males) were evaluated using an 8-16MHz linear array transducer (Diasus Dynamic Imaging). Subjects were scanned in a prone, lateral position. The transducer was placed in the posterior triangle orientated longitudinally, initially along the posterior border of sternocleidomastoid and then moved in a cranial-caudal direction. By adjusting the angle (in the antero-posterior direction) of the transducer about a fixed position; facet joints and discs were located. The characteristic V shaped appearance of the facet joint emanates from the hyperechoic signal of the closely spaced transverse processes of adjacent vertebra (Figure1). Disc regions appeared as areas of high signal penetration into the spine with low amplitude signals returning from the disc.

Conclusion: The detail of facet joint and disc anatomy captured using ultrasound reveal it to be a viable imaging tool for interventional procedures. Noteworthy advantages of ultrasound include: its ability to provide real-time images economically, the option of portability and no known side effects.

Objective: To measure intradiscal pressures in scoliotic spines to further understand the role of mechanical forces in the development of scoliosis.

Design: Pressure readings were obtained in consented patients with ethical approval. A needle mounted pressure transducer was introduced into the disc during routine anterior scoliosis surgery.

Subjects: Ten human scoliotic discs from three patients.

Outcome measures: Intradiscal pressure profiles.

Results: Nuclear hydrostatic pressures varied from 0.2 to 0.6 MPa. The mean nuclear pressures for the three spines were 0.27+0.12, 0.35+0.06 and 0.47+0.12 MPa.

High stress, non- hydrostatic regions were consistently recorded in the concave annulus.

Conclusions: Nuclear pressures in these scoliotic patients were significantly higher than the 0.12 and 0.15 MPa recorded previously in non-scoliotic recumbent individuals^1;2 suggesting that spinal loading is abnormal in scoliosis.

Posterior fixation of intervertebral discs is used to treat, and occasionally diagnose, discogenic pain since it is thought that it will reduce the internal loading of the discs in vitro. We measured the internal loading of ten intervertebral discs using stress profilometry under simulated physiological loads and then after posterior fixation. Partial discectomies were performed to simulate advanced disc degeneration and the sequence repeated.

Posterior fixation had very little effect on the magnitude of the loads acting on the disc and none when disc degeneration was simulated. It did, however, reduce bulging of the anterior annulus under combined bending and compression (p < 0.03). Recent experiments in vivo have shown that discogenic pain is associated with abnormal bulging of the annulus which suggests that the clinical benefit of fixation may be due to this.

We investigated the distribution of compressive ‘stress’ within cadaver intervertebral discs, using a pressure transducer mounted in a 1.3 mm diameter needle. The needle was pulled along the midsagittal diameter of a lumbar disc with the face of the transducer either vertical or horizontal while the disc was subjected to a constant compressive force. The resulting ‘stress profiles’ were analysed in order to characterise the distribution of vertical and horizontal compressive stress within each disc. A total of 87 discs from subjects aged between 16 and 87 years was examined.

Our results showed that age-related degenerative changes reduced the diameter of the central hydrostatic region of each disc (the ‘functional nucleus’) by approximately 50%, and the pressure within this region fell by 30%. The width of the functional annulus increased by 80% and the height of compressive ‘stress peaks’ within it by 160%. The effects of age and degeneration were greater at L4/L5 than at L2/L3, and the posterior annulus was affected more than the anterior. Age and degeneration were themselves closely related, but the stage of degeneration had the greater effect on stress distributions.

We suggest that structural changes within the annulus and endplate lead to a transfer of load from the nucleus to the posterior annulus. High ‘stress’ concentrations within the annulus may cause pain, and lead to further disruption.