Generalization of the relationships between sagittal balance geometric parameters

Sagittal balance of the spine characterizes its physiological alignment by muscular forces in the most effective way. Optimal spinal-pelvic relationships form a biomechanically efficient and optimal sagittal profile of the spine, which reduces energy consumption for an equilibrium state maintaining and also decrease the risk of degenerative damage to the intervertebral discs. Sagittal balance is described using the main angular parameters: pelvic incidence, lumbar lordosis, pelvic tilt and sacral slope. To form optimal spinal-pelvic relationships during surgical treatment surgeons measure the actual balance parameters of the patient and use empirical formulas to calculate their theoretical values at preoperative planning stage. To calculate the optimal parameters of the sagittal balance of a particular patient, various scientific groups have developed a number of empirical dependencies. However, there is no consensus in the scientific community on what specific formulas to use when planning treatment. This paper attempts to generalize the data available in the scientific literature on the parameters of the sagittal balance and to develop new generalizing regression dependencies that allow one to link the parameters of the sagittal balance. For this purpose, the source data used for constructing such dependencies were collected from the literature. The results of the sagittal balance measurement of Saratov State Medical University patients were also used in this study. We selected the initial numerical data linking the main parameters of the sagittal balance from the literature. The data was digitized and processed using statistics methods. Regression dependencies were obtained that allow calculating lumbar lordosis, pelvic tilt, and sacral slope through the pelvic incidence of a particular patient. Generalizing dependences make it possible to systematize the clinical experience accumulated in the literature and were used in the development of the world's first system for preoperative planning of surgical treatment of the consequences and diseases of the spine-pelvic complex with biomechanical support of the doctor's decision.