Sacrum

Abstract: Study design A prospective radiographic study of 160 volunteers without symptoms of spinal disease was conducted. Objectives The objective of this study was to describe, quantify, and classify common variations in the sagittal alignment of the spine, sacrum, and pelvis. Summary of background data Previous publications have documented the high degree of variability in the sagittal alignment of the spine. Other studies have suggested that specific changes in alignment and the characteristics of the lumbar lordosis are responsible for degenerative changes and symptomatic back pain. Methods In the course of this study, anteroposterior and lateral radiographs of 160 volunteers in a standardized standing position were taken. A custom computer application was used to analyze the alignment of the spine and pelvis on the lateral radiographs. A four-part classification scheme of sagittal morphology was used to classify each patient. Results Reciprocal relationships between the orientation of the sacrum, the sacral slope, the pelvic incidence, and the characteristics of the lumbar lordosis were evident. The global lordotic curvature, lordosis tilt angle, position of the apex, and number or lordotic vertebrae were determined by the angle of the superior endplate of S1 with respect to the horizontal axis. Conclusions Understanding the patterns of variation in sagittal alignment may help to discover the association between spinal balance and the development of degenerative changes in the spine.

Abstract: From the material and data reviewed in our study of 405 patients, it appears that postoperative correction of the thoracic spine approximately equals the correction noted on preoperative side-bending roentgenograms. Selective thoracic fusion can be safely performed on a Type-II curve of less than 80 degrees, but care must be taken to use the vertebra that is neutral and stable so that the lower level of the fusion is centered over the sacrum. The lumbar curve spontaneously corrects to balance the thoracic curve when selective thoracic fusion is performed and the lower level of fusion is properly selected. In Type-III, IV, and V thoracic curves the lower level of fusion should be centered over the sacrum to achieve a balanced, stable spine.

Abstract: The standing posture of 17 young men and women were studied using Barycentremeter measurements and full spine radiograph with a single referential system. These procedures provide in vivo measurements of the weight and center of weight supported by each vertebra and the coxofemoral joints. The relationship between the vertebra, the sacrum or the coxofemoral rotation axis and the center of weight they support, is displayed. The moment of the corresponding force may also be assessed. Mean values were computed and the relation with spine sagittal curves and pelvic parameters were studied. The position of the center of weight, in front of or behind the vertebra or the coxofemoral joints, requires an opposing muscle force to ensure mechanical stability. The load exerted on the vertebra cannot be precisely evaluated, but we can describe the way in which these loads vary when the spinal curves and the pelvic slope change. This study provides basic data suggesting that there is a tendency to maintain the body in the most economical position in terms of muscle fatigue and vertebral strain. Individual anatomical shapes and pelvic parameters of the pelvis induce corresponding specific sagittal curves of the spine. This concept is very useful for analysing pathological situations and devising appropriate treatment.

Abstract: Sacral fractures, often undiagnosed and untreated, frequently result in neurologic symptoms and deficits to the lower extremities and urinary, rectal, and sexual dysfunctions. These same neurologic problems often remain the major chronic sequelae after the more obvious pelvic trauma lesion has healed. Specific treatments aimed at neurologic problems are available and may allow the patient functional recovery. This is illustrated by anatomic observations on the sacrum in 39 cadavers showing the relationship among sacral nerve roots within their foramina. These observations were valuable for a retrospective study of 236 consecutive patients with sacral fractures in a series of 776 patients with pelvic injuries. A new classification of sacral fractures evolved from this study and provided a better understanding of the mechanisms responsible for the associated neurologic symptoms. The classification is based on the direction, location, and level of sacral fractures. Three different zones were identified as having characteristic clinical presentations: Zone I, the region of the ala, was occasionally associated with partial damage to the fifth lumbar root. Zone II, the region of the sacral foramina, is frequently associated with sciatica but rarely with bladder dysfunction. Zone III, the region of the central sacral canal, is frequently associated with saddle anesthesia and loss of sphincter function. Routine pelvic roentgenograms were almost useless in identifying the pathologic process in sacral injuries with neurologic symptoms. Ferguson views, tomograms, and particularly computed tomography scans were crucial for understanding these injuries. Cystometrography was most helpful in positively identifying fractures causing neurogenic bladders. Cystometrograms should be ordered routinely in Zone III injuries. Preliminary observations suggest that surgical decompression permitted significantly better neurologic recovery than nonsurgical methods.