IL-1beta sensitizes intervertebral disc annulus cells to fluid-induced shear stress.

Chronic inflammation and altered mechanical loading are implicated as contributors to intervertebral disc degeneration. Biomechanical and biochemical factors play a role in disc degeneration but have received limited study. Mechanically, intervertebral discs are sheared during bending or twisting of the trunk. Biochemically, IL-1beta, detected in degenerative discs, promotes metalloproteinase expression. We hypothesized that disc cells might respond to shear stress and IL-1beta in a calcium signaling response. We measured the effect of single and combined stimuli on intracellular calcium concentration ([Ca2+]ic) and signaling. Cells were isolated from annulus tissue, cultured to quiescence, plated on collagen-bonded Culture Slips and incubated with Fura-2AM. Cells then were incubated in IL-1beta. Cell response to the effects of fluid flow was tested using FlexFlo, a laminar flow device. Human annulus (hAN) cells responded to laminar fluid flow with a one to three-fold increase in [Ca2+]ic. IL-1beta alone produced a small, transient stimulation. hAN cells pretreated with IL-1beta responded to shear with a more dramatic and sustained increase in [Ca2+]ic, six to ten-fold over basal level, when compared to shear then IL-1beta or shear and IL-1beta alone (P<0.001 for all comparisons). This is the first study documenting synergism of a signaling response to biomechanical and biochemical stimuli in human disc cells. IL-1beta treatment appeared to "sensitize" annulus cells to mechanical load. This increased responsiveness to mechanical load in the face of inflammatory cytokines may imply that the sensitivity of annulus cells to shear increases during inflammation and may affect initiation and progression of disc degeneration.

MR parameters for imaging titanium spinal instrumentation.

The presence of stainless steel implants along a spinal column causes extreme distortion of data collected by magnetic resonance (MR) imaging. The recent availability of titanium alloy spinal instrumentation systems suggests that MR imaging evaluation of the instrumented spine may now be feasible. The objective of this study was to perform MR imaging examinations on spines implanted with titanium alloy instrumentation and to determine the parameters that yield the highest quality images with the least amount of artifact. A titanium pedicle screw construct was implanted into the lumbar spine of two fresh human cadaveric specimens. Sequential spin echo MR scans were performed using various TE and TR ratios on each intact specimen. The resultant images were quantitatively graded for clarity of adjacent soft tissue and osseous structures. Excellent T1- and T2-weighted images with well-defined neural structures were obtained with minimal artifact. The optimal T1-weighted image was obtained with TE = 16 and TR = 500-600, whereas the optimal T2-weighted image was obtained with TE = 60 and TR = 1,300-1,600. By using appropriate settings, high-quality MR scans in both the T1- and T2-weighted modes can be obtained with minimal metal artifact.

Hyponatremia and syndrome of inappropriate antidiuretic hormone secretion in adult spinal surgery.

STUDY DESIGN: Patients undergoing spinal surgery were monitored for sodium balance, fluid type, and volume input and output during surgery and for the first 3 postoperative days. OBJECTIVE: To prospectively document the true incidence of the syndrome of inappropriate antidiuretic hormone secretion and hyponatremia, and identify risk and protective factors for the development of the syndrome of inappropriate antidiuretic hormone secretion after spinal surgery. METHODS: Data on medical history, surgical procedure, estimated blood loss, and volumes and types of intraoperative and postoperative fluids were collected on 116 consecutive spinal surgery patients during March to July 1992. RESULTS: One hundred one spinal operations in 96 patients were evaluated. There were 48 males and 48 females, with a mean age of 52 years (range, 16 to 90 years). Hyponatremia developed in 45 (44.6%) patients. The etiology of hyponatremia was the syndrome of inappropriate antidiuretic hormone secretion in seven patients (6.9%), hypovolemia in 19 patients (18%), and other causes in six patients. CONCLUSIONS: Spine patients are at risk for hyponatremia and the syndrome of inappropriate antidiuretic hormone secretion. The incidence of the syndrome of inappropriate antidiuretic hormone secretion was 6.9%. Serum sodium should be monitored postoperatively. Patients who undergo a revision operation have an approximately two to four times greater risk of being affected by the syndrome of inappropriate antidiuretic hormone secretion than those who have primary surgery.