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The 3 dimensional analysis of the common mechanism of spinal deformities

Spine deformities are the most common orthopedic diseases in childhood. Scoliosis is a multifactorial three-dimensional (3D) spinal deformity that always involves elemental deformities in the three main planes: lateral curvature in the frontal, anteroposterior (mainly lordotic) deviation in the sagittal, and (very characteristically) vertebral axial rotation in the horizontal plane. Neither the beginning nor the nature of the progression of the structural scoliosis is known. The study of three-dimensional deformity components showed that there is a direct, but non-linear relationship between the deformities occurred in different planes, of which the nature is not fully understood. However, it is generally accepted that the primary alteration is the vertebral rotation in the horizontal plane resulting in the instability of the spine followed by the development of the scoliosis. It is generally accepted that after the initial appearance of the deformity, the idiopathic scoliosis progresses automatically.

Despite obvious evidence of the three-dimensional nature of scoliosis, the visualization of the horizontal plane, the most important element of the development of a spinal deformity – in the absence of appropriate technical capabilities – was not available.

Symptoms related to adult scoliosis are mostly due to degeneration of structures that support the spine. These changes, which are often called “arthritis of the spine”, can occur at all levels of the back. With aging and arthritis, a gradual narrowing of the disc spaces between vertebrae, wearing out of the joints, as well as narrowing of the space available for the nerves (lumbar stenosis) can develop.
Although degeneration of the spine is part of the normal aging process in all people, it appears that in most cases the spine becomes stiffer with age but does not develop a lot of abnormal curvatures and causes only minimal or no pain. In other cases the spine loses its structural stability with aging and gradually develops abnormal curvatures that can be painful and lead to symptoms including back pain, stooped posture, leg problems (numbness, heaviness, tingling, pain and weakness) and progressive difficulty in walking which requires frequent rests and activity limitation.

The degenerative changes of the lumbar spine associated with the instability causing degenerative scoliosis don’t have a reasonable hypothesis regarding the cause of the disease.

Stokes and the Scoliosis Research Society Working Group on 3D Terminology of Spinal Deformities made the fol¬lowing assertion: "Visualization of anything three-dimen¬sional is a great challenge. The approach we adopted attempts to accommodate this human limitation by mak¬ing extensive use of the "auxiliary" planes on to which the spine is projected. Such measurements are not truly 3D, but this approach of using "quasi-3D" measurements rep¬resents a reasonable compromise between mathematical purity and conceptual and practical limitations". (Stokes IA Three-dimensional terminology of spinal deformity. A report presented to the Scoliosis Research Society by the Scoliosis Research Society Working Group on 3-D terminology of spinal deformity. Spine 1994 Jan 15; 19(2): 236-48).

In view of the lack of a definitive and reproducible measurement method for 3D characterization of spine deformities, we introduced the concept of vertebra vectors. The vertebra vector appears as a line starting at the midpoint of the interpedicular line forming the axis of the vertebra body in the sagittal median axis of the vertebra. The initial point is positioned inside the spinal canal, symmetrically dividing the interpedicular distance. Following the creation, the vectors were placed in a coordinate system in order to determine the x, y, and z coordinates of their initial and terminal points. Once the vertebra vectors are in this calibrated coordinate system, the coordinates of each vector points can be determined in all three planes by using basic geometric and vector algebraic methods. Based on the vector’s coordinates, mathematical description and analysis of the scoliotic spine deformity could be performed. The usefulness of vertebra vectors in the description of 3D spine deformities were already published several times (Illés T, Tunyogi-Csapo M, Somoskeo¨y Sz, Breakthrough in Three-Dimensional Scoliosis Diagnosis - Significance of Horizontal Plane View and Vertebra Vectors, Eur. Spine J. 2011; 20:(1) pp. 135-143; Somoskeo¨y Sz, Tunyogi-Csapo M, Bogyo Cs, Illés T, Clinical validation of coronal and sagittal spinal curve measurements based on three-dimensional vertebra vector parameters. Spine Journal. 2012; 12:(10) pp. 960-968; Somoskeo¨y Sz, Tunyogi-Csapo M, Bogyo Cs, Illés T, Accuracy and reliability of coronal and sagittal spinal curvature data based on patient-specific three-dimensional models created by the EOS 2D/3D imaging system. Spine Journal. 2012; 12:(11) pp. 1052-1059; Illés T, Somoskeo¨y Sz, Comparison of scoliosis measurements based on three-dimensional vertebra vectors and conventional two- dimensional measurements: advantages in evaluation of prognosis and surgical results. Eur. Spine J. 2011; 22:1255–1263).

The vertebra vectors afford simple, intelligible means of visualizing and describing the essential features of the complex 3D information of the scoliotic spine. The analysis of vertebra vector data – of which we want to use during our research on the 3 dimensional spinal deformities – may lead to a better understanding of the pathomechanism of the idiopathic and degenerative scoliosis and promote the development of a basis for new concepts in therapeutic procedures.

The accurate understanding of the pathogenesis of 3 dimensional spinal deformities could be very important not only in order to improve the quality of life of patients, but also to the reduction of health economic costs because the indirect cost of the disability caused by degenerative spine diseases is considerable and significantly higher than the direct costs of diagnosis and treatment.
The 3 dimensional analysis of the common mechanism of spinal deformities