A bovine stress syndrome associated with exercise-induced hyperthermia.

OBJECTIVE: To investigate an exercise-induced bovine stress syndrome under field and controlled experimental conditions. DESIGN AND PROCEDURE: In the field study, cattle affected with the stress syndrome were observed while they were grazing and during normal mustering using horses. This study served to define the clinical nature of the syndrome. The experimental study utilised three affected and five normal unaffected cattle. These animals were compared on the basis of their response to a defined exercise program, which consisted of walking 3.6 km in 2 h. Blood samples and measurements of respiratory rate, ambient temperature and rectal temperature were taken immediately before exercise, and at 0.5, 1.0, 1.5 and 2.0 h during the exercise and 24 h later. Clinical and blood constituent data were subjected to standard analysis of variance and repeated measures analysis. RESULTS: In the field study, affected cattle were observed to show abnormally anxious and hyperactive behaviour. This behaviour was exhibited by affected cattle during the experimental exercise program where it was shown to be accompanied by hyperthermia and hyperventilation. The experimental study showed that affected cattle developed metabolic acidosis and became hyperglycaemic. Their plasma creatine kinase activity remained markedly increased at 24 h after exercise but other clinical and blood constituent variables had returned to normal values. CONCLUSION: The clinical and biochemical changes detected in affected cattle were consistent with exercise-induced malignant hyperthermia.

Compensatory spinopelvic balance over the hip axis and better reliability in measuring lordosis to the pelvic radius on standing lateral radiographs of adult volunteers and patients.

STUDY DESIGN: Sagittal alignments, including lumbar lordosis and spinopelvic balance (measured from C7, S1, and hip axis reference points for the relative positions of the spine and sacropelvis over the hips), were studied on standing 36-in. lateral radiographs of adult volunteers (control subjects) and patients who had specific spinal disorders. OBJECTIVES: To determine the most reliable methods for measuring lumbopelvic lordosis and to define significant spinopelvic compensations for sagittal balance. SUMMARY OF BACKGROUND DATA: Measurements for standing sagittal balance, obtained using a C7 plumb line, and segmental angulations of the spinal vertebrae, including lordosis to the sacrum, have been reported. Absolute values, even for normative data, have had wide variation and limited clinical usefulness. Correlations of sagittal balance with the reported spinopelvic angulations (spinal vertebral and sacropelvic angulations) have not been well defined. In addition, determinates of balance (spinal and pelvic) have not been studied for reliability, and compensatory mechanisms for maintenance of balance have not been carefully evaluated. Better recognition of the correlations and more reliable methods to measure lordosis and balance and the spinopelvic compensations for its maintenance may be beneficial in treating patients who have spinal disorders. METHODS: Measurements on standing 36-in. lateral radiographs were made for sagittal alignments in adult volunteers (n = 50) and in adult patients who had symptomatic degenerative lumbar disc disease (n = 50), low grade L5-S1 isthmic (lytic) spondylolisthesis (n = 30), and idiopathic or degenerative scoliosis (n = 30). All participants exhibited clinical compensation for balance. Data were analyzed for significant correlations within each group to determine compensatory correlations of spinopelvic balance with the other sagittal alignments. Intraobserver and interobserver reliability for the parameters evaluated were calculated. This included two methods for determining lordosis (S1 end-plate and pelvic radius techniques). RESULTS: Plumb line measurements for balance from the S1 and hip axis reference points, as defined, were similar in all four groups. However, the groups appeared to adjust for balance by using common and distinctive spinopelvic compensations that resulted in significantly and characteristically different angular alignments among the four groups. Lordosis and balance measurements were closely correlated, and the correlation was characterized by pelvic rotation and translation around the hip axis. The subjects with less lordosis typically stood with the C7 plumb line anterior to and at a longer distance from the sacral reference point. This was primarily because of posterior sacropelvic translation around the hip axis and not because the sagittal plumb line initially moved anteriorly away from the sacrum. This was true in all four groups and gave the appearance that the sacropelvis was less well balanced over the hips in the subjects with less lordosis. Even small differences in lordosis appeared to be associated with considerable adjustments in the other spinopelvic alignments. Therefore, it was important to determine that lordosis was lumbopelvic more reliably measured by the pelvic radius technique. CONCLUSIONS: Lower lumbar lordosis, by the pelvic radius technique, and compensatory sacropelvic translation around a hip axis, in addition to measurements from this axis to the C7 plumb line, were the primary determinates and most reliable radiographic assessments for sagittal balance. Understanding the common and characteristically different compensations that occur with balance in these patients who had specific spinal disorders may help to improve their care.

The effect of operative position on lumbar lordosis. A radiographic study of patients under anesthesia in the prone and 90-90 positions.

STUDY DESIGN: The effect of intraoperative positioning on lumbar lordosis was retrospectively studied by radiographic analysis of 40 patients under general anesthesia. OBJECTIVES: The aim of this study was to document changes in segmental and total lumbar lordosis between preoperative standing and intraoperative radiographs taken in the "90-90" and prone positions. SUMMARY OF BACKGROUND: Preservation of physiologic lordosis was an important consideration in reconstructive lumbar spine surgery. To avoid iatrogenic loss of lordosis when using spinal instrumentation and to facilitate decompressive procedures, it was necessary to understand how segmental alignments were affected by intraoperative positioning. Although many positioning techniques were used, the effect on lumbar lordosis was not well established. METHODS: Preoperative (standing 36" lateral spine) and intraoperative radiographs (lateral lumbar spine L1 to the sacrum) in either the "90-90" position on a Hastings frame (n = 20) or the prone position on a Jackson table (n = 20) were measured twice by two independent observers using Cobb methodology for total and segmental lordosis between L1 and S1. Data were analyzed for intra- and interobserver reliability and changes in segmental and total lordosis between standing and intraoperative radiographs. RESULTS: Analysis of intra- and interobserver reliability revealed measurements were accurate and reproducible. The "90-90" position produced significant loss (P < or = 0.01) of total and segmental lordosis at all levels except L1-L2, which showed no change. Segmental lordosis was reduced nearly 60% at L2-L3, L3-L4, and L4-L5, and total lordosis was reduced by more than 35%. The prone position on the Jackson table increased segmental lordosis at L5-S1 by 22% (P < or = 0.01) and preserved total and segmental standing lordosis at all other levels. CONCLUSIONS: The "90-90" position on the Hastings frame was associated with significant reduction of total and segmental lordosis in the middle and lower lumbar spine. Positioning prone on a Jackson table maintained standing lumbar lordosis and increased lumbosacral lordosis.

Radiographic analysis of sagittal plane alignment and balance in standing volunteers and patients with low back pain matched for age, sex, and size. A prospective controlled clinical study.

STUDY DESIGN: A global and segmental study on standing lateral radiographs of 100 volunteers and 100 patients who had low back pain was undertaken to further define sagittal plane alignment and balance. The volunteer control group and the patient group were matched for age, sex, and size. METHODS: Measurements and determinations made on the standing radiographs included the following: segmental and total lordosis L1-S1 (Cobb method); thoracic kyphosis; thoracic apex; plumbline dropped from the center of C7; and sacral inclination measured between the plumbline and a line drawn along the back of the proximal sacrum. RESULTS: Segmental lordoses were significantly different between each motion segment in both groups. Approximately two-thirds of total lordosis occurred at the bottom two discs, i.e., L4-5 and L5-S1. Total lordosis was significantly less in the patients and was not age- or sex-related in either group. Patients tended to stand with less distal segmental lordosis, but more proximal lumbar lordosis, a more vertical sacrum and, therefore, more hip extension. This may be related to compensation as C7 sagittal plumb lines were comparable in both groups. Both groups had similar thoracic kyphosis. A much higher percentage of smokers was found in the low back pain patient population studied. Because of the significant amount of angulation in the lower lumbar spine, measurement of lordosis should include the L5-S1 motion segment and be done standing to better assess balance. Sacral inclination is a determinate of both standing pelvic rotation and hip extension. It is strongly correlated with segmental and total lordosis in both volunteers and patients. CONCLUSIONS: Definitions of sagittal balance are provided as well as additional sagittal plane data by which to compare corrections and fusions for different spinal disorders.

The iliac buttress. A computed tomographic study of sacral anatomy.

Fifty randomly selected computed tomographic (CT) scans of the lumbosacral spine (25 males and 25 females) were studied to determine: 1) if the lateral sacral masses could safely accept a 7 mm diameter rod (i.e., intrasacral rod insertion) and 2) what percentage of patients, both males and females, demonstrated coverage of the posterolateral sacrum by the ilia (i.e., iliac buttressing). In all patients the lateral masses (i.e., the lateral intrasacral mass measurements) appeared wide enough on CT to allow for safe insertion of a 7 mm diameter rod, or other similar size implant, down to at least the level of S2. The smallest distance measured for the width between the posteromedial margin of the sacroiliac joint and the lateral cortex of the S1 neuroforamen (i.e., the lateral intrasacral mass measurement) at its location approximately midway (anteroposterior) through the sacrum on CT cuts was 17 mm (mean 28 mm). This would appear to give adequate room for a 7 mm diameter rod to be inserted at this level in the lateral sacrum (i.e., intrasacral rod insertion). Forty-six patients (24 males, 96%; and 22 females, 88%) appeared to have sufficient CT coverage of the sacrum to conceptually provide for so called "sacroiliac buttressing" of rods, if rods or other implants were to be inserted distally into the lateral masses. After a review of the sacral anatomy by CT it appears that: 1) insertion of rods into the lateral sacral masses (i.e. intrasacral rod insertions), or intrasacral fixation with other similar size implants, would be possible and apparently safe; and 2) the ilia along with the sacroiliac interosseous ligaments sufficiently surround the back and sides of the posterolateral sacrum in most patients (92%), at least by CT assessment, to conceptually offer an indirect "buttress" for implants so inserted. Theoretically, this could biomechanically help resist the flexural loads across the lumbosacral level and possibly provide a method for improved sacral fixation with spinal instrumentation in certain patients.