Are peak posterior annular and nuclear temperatures obtained during IDET within the temperature range normally associated with nociceptor destruction and contraction of collagen?

Pain relief following intradiscal electrothermal therapy (IDET) has been reported to result from coagulation of annular nociceptors and contraction of collagen. This requires temperatures respectfully of 45°C and 60°C. A cadaveric study using an intradiscal catheter (Spinecath, Oratec Interventions Inc., CA) reported sufficient temperatures for these events to occur. However a human study reported temperatures sufficient only to coagulate nociceptors. This study reports peak posterior annular and nuclear temperatures attained in-vivo with an intradiscal catheter in sheep.

Twenty sheep were anaesthetised and the lumbar spine exposed. In two non-adjacent discs a stab incision was made in the left postero-lateral annulus and the wound closed. Twelve weeks later the animals returned for a second operation. The spine was approached from the right. Under fluoroscopic control the intradiscal catheter was placed into a previously operated disc. One thermocouple sensor needle was placed 2mm posterior to the catheter to record the posterior annular temperature and a second was inserted 2mm anterior to record the nuclear temperature. The process was repeated for a non-operated control disc. Electrothermal energy was delivered according to the recommended heating protocol.

The target temperature of 90°C at the catheter tip was reached in all cases. Data were tabulated with the mean and standard deviation calculated for each site. There was no significant difference between temperatures reached in the ‘degenerate’ discs and those in the control discs. The mean maximum posterior annular temperature was 63.6°C (range 46.8 to 77.7) and the mean maximum nuclear temperature was 67.8°C (Range 51.1 to 81.2).

Intradiscal electrothermal therapy delivered at 90°C in the sheep consistently heats the posterior annulus and the nucleus to a temperature associated both with coagulation of nociceptors and collagen contraction. These findings may contribute to understanding the mechanism of pain relief following IDET.

To determine how long after injury a single photon emission computed tomography (SPECT) scan may remain positive in cases of symptomatic posterior element lumbar stress injuries.

SPECT scans can identify posterior element lumbar stress injuries earlier than other imaging modalities. As these lesions evolve and the spondylolysis becomes chronic, the SPECT scan tends to revert to normal even though healing of the defect has not occurred. The aim of this study was to determine how long after initial injury a SPECT scan might remain positive.

One hundred and sixty-five patients (85 male, 80 female) between the ages of 8 and 38 years with suspicion of lumbar spondylolysis or posterior element lumbar stress injuries were investigated. All patients underwent plain radiographs, planar bone scintigraphy and SPECT imaging. The duration of symptoms at clinical assessment was recorded. The age, sex, symptom reproduction on flexion or extension, level of sporting activity, and the Oswestry Disability Index both pre- and post-treatment were also recorded. SPECT positive images (hot scans) were depicted as cases and SPECT negative images as controls. Univariate and multivariate analysis was performed.

Eighty-five patients (63 male, 22 female) had positive SPECT scans (cases); eighty had negative scans (controls). The mean age at onset of symptoms was 20.2 years for cases and 17.4 years for controls. Bilateral increased uptake on SPECT scan was more common than unilateral. The commonest site for increased uptake was the posterior elements of the fifth lumbar vertebra. Low back pain in extension was more common in SPECT positive cases. The mean time from injury / onset of symptoms to a positive SPECT scan was 7.1 months (range 5.2–9.2 months) and to a negative SPECT scan was 22.5 months (range 16.8–28.4 months).

Intense scintigraphic activity in the posterior elements of the lumbar spine was associated with a more recent injury and was concordant with the patient’s history and physical examination. Chronic, un-united spondylolysis was often scintigraphically occult. There was a window of approximately six months from the onset of symptoms to investigation after which the sensitivity of SPECT imaging diminished.

The incidence of symptomatic pars defect varies between 15% and 47% in the young athletic population. We have analysed the outcome of direct repair spondylolysis on young professional athletes.

We have prospectively studied 22 young athletes with lumbar spondylolysis in whom conservative treatment has failed. Fifteen male and 7 female patients with a mean age of 20.2 years (range 15–34 years) were surgically treated for radiographically confirmed spondylolysis between 1994 and 1999. Eleven patients were professional footballers and four were professional cricketers. Pre-operative assessment included plain X rays, SPECT imaging with planar bone scan and reverse gantry CT scans. All patients had the Oswestry disability index (ODI) and 19 patients had Short Form 36 (SF-36) scores recorded pre-operatively and two years post operatively. Nineteen patients underwent Buck’s fusion and 3 underwent Scott’s fusion. At two-year follow-up nineteen patients had ODI and SF36 scores recorded. Return to the sporting activity at the previous level was regarded as a successful outcome.

The average duration of back pain prior to surgery was 8.9 months (range 1-36 months). The mean lysis defect determined by CT was 3.5 mm (range 1–8 mm). The mean pre-operative ODI was 39.5 (SD=8.7) and the mean post-operative ODI was 10.7 (SD=12.9). The mean scores of the physical health component of SF-36 improved from 27.1 (SD=5.1) to 47.8 (SD=7.7). The mean scores of the mental health component of SF-36 improved from 39.0 (SD=3.9) to 55.4 (SD=6.3) [P < 0.001].

The surgical repair of bilateral spondylolysis with modified Buck’s fusion in professional sportsmen and women results in a significant improvement in Oswestry Disability scores (p< 0.001) and in all domains of SF36 health questionnaire (p< 0.001). Ninety five percent of patients in this group return to active sport within seven months of surgery.

Routine use of Computed Tomography (CT) to evaluate discogram morphology is time consuming, costly and incurs additional radiation hazards. In our spinal unit, discography is routinely performed without the aid of CT. Discogram morphology for different stages of disc degeneration is evaluated using the modified Adam’s grading system on images obtained on fluoroscopy. Our aims were to assess the validity of the modified Adam’s grading system of discogram morphology, by assessing its inter- and intra-observer agreement.

We reviewed the discographic images (133 intervertebral levels) of 71 patients with chronic low back pain undergoing discography as part of a preoperative assessment between 1995 and 1997. Using the modified Adam’s grading system, three independent surgeon observers of three levels of experience (Senior Fellow, Senior and Junior residents) retrospectively evaluated the morphological appearance of each disc level in a randomized and blinded manner. Each observer was supplied with descriptions and illustrations of the 5 grades1, and each level was classified accordingly. The exercise was repeated three weeks later. The respective inter- and intra-observer agreements were calculated using the kappa statistic (Fleiss 1971) and generalized kappa statistic (Landis and Koch 1977).

The inter-observer agreement was excellent (kappa = 0.77; standard error = 0.054). The intra-observer agreement for each of the three observers was also excellent (kappa = 0.8, 0.8, and 0.85 with respective standard errors = 0.046, 0.049 and 0.042).

Significance and conclusions: The inter- and intra-observer agreement and therefore the reliability of the modified Adam’s grading system is excellent. This classification is easy to apply and has a high degree of reproducibility amongst observers with different levels of spinal experience. In view of the high reproducibility, we recommend the Adam’s classification for the grading of discogram morphology. The routine use of computed tomography with the concomitant radiation exposure and additional cost would seem not to be justified.

Objective: This study investigates whether the sequence of anterior and posterior procedure has any effect on the lordosis, disc height and stability in combined A-P fusion of the lumbar spine.

Design: A biomechanical study on cadaver lumbar spine.

Materials and Methods: Twelve motion segments (between L2–L5) from four cadaver lumbar spines were studied. Anterior and posterior stabilization were performed using a Syncage (Synthes, Switzerland) of appropriate sizes, and translaminar screws respectively. Load-deformation characteristics in flexion-extension, lateral bending, and torsion were tested in a material-testing machine (Dartec, Stourbridge, UK) with 7.5Nm cyclical load. Angular deformation of each motion segment was determined simultaneously, by 2-D optical reflex camera system (Pro-reflex, Qualysis, Sweden). Disc height, and angle of lordosis between the adjacent endplates were determined from lateral radiographs. These parameters were measured in the intact spine, after A-P fixation with front first, and after back procedure first.

Results: Compared to the intact spine, the disc height was significantly increased (p< 0.05) when Syncages were introduced before posterior fixation, but not when posterior fixation was done first (p = 0.12). The angle of lordosis was increased significantly with posterior stabilization first, but only marginally, with anterior stabilization first. The stability of the motion segments increased significantly with combined A-P fusion, compared to either anterior or posterior fixation alone. With posterior stabilization first, the stability in all directions were greater but not statistically significant, compared to anterior stabilization first (p> 0.05).

Conclusion: In combined A-P fusion of lumbar spine, the lordosis is better restored when posterior stabilization is done first, but disc height is better restored when the anterior stabilization is performed first. Stability of fixation is not significantly affected by altering the sequence.

Injury to the spinal cord without radiological abnormality often occurs in the skeletally immature cervical and thoracic spine. We describe four adult patients with this diagnosis involving the cervical spine with resultant quadriparesis. The relevant literature is reviewed. The implications for initial management of the injury, the role of MRI and the need for a high index of suspicion are highlighted.