Calculation of the angle required during pedicle subtraction osteotomy for fixed sagittal deformity: a literature review

Abstract

Sagittal spinal deformity is one of the common reasons of sagittal disequilibrium which can cause torso forward, cardiopulmonary dysfunction, flat back syndrome, intractable low back pain and a series of cases, affecting the patients' life quality and increasing huge economic burden on society. The treatment of sagittal spinal deformity has been a hot spot in the field of clinical spinal surgery and its main purpose is to reconstruct the overall balance of the body, which would relieve pain and improve life quality. Pedicle subtraction osteotomy is considered to be one of the most effective and safe method for correcting spinal deformity with excellent reconstruction of sagittal plane balance. However, the calculation of the angle required during surgery is still a problem, because insufficient or excessive correction will lead to the secondary sagittal disequilibrium. Therefore, an accurate calculation of the angle required during pedicle subtraction osteotomy is particularly important. In recent years, scholars believe that the sagittal equilibrium depends on a fragile balance among spinal curvature, pelvic shape and position of the lower limbs. Scholars have developed a standard of sagittal equilibrium based on their own research, and proposed a variety of quantitative analysis methods to calculate the angle required during pedicle subtraction osteotomy: trigonometric method, exact angle calculation method, overall balance method, spine femoral angle measurement method, digital virtual method, graphic method, acoustic meati to hip axis method and hilus pulmonis to hip axis method, which provide important theoretical bases for the treatment of sagittal spinal deformity.