Device for helping to bend surgical rods
A method for helping to bend a rod that can be implanted in a patient, the method including the following steps: acquiring one or more measurements of distance and/or angle between elements of a vertebral column of the patient; determining a type of vertebral column of the patient, on the basis of the measurements, according to a classification; identifying one or more invariant parameters corresponding to the determined type of vertebral column; calculating one or more radii of curvature for bending a rod on the basis of the previously identified invariant parameters and the determined type of vertebral column; obtaining a representation of the rod bent according to the one or more radii of curvature; and displaying the representation.
1 . A method for helping with bending a rod that can be implanted in a patient, the method comprising, on the basis of a prior acquisition of one or more measurements of distance and/or of angle between elements of a spinal column of the patient, these measurements being taken from an image of the back of the patient, the following steps:
a) determining a type of spinal column of the patient according to a classification;
b) identifying one or more invariable geometrical parameters corresponding to the type of spinal column determined;
c) calculating one or more radii of curvature for the bending of a rod as a function of said measurements, of the type of spinal column determined and of said invariable geometrical parameters previously identified;
d) obtaining a representation of the rod bent to said one or more radii of curvature; and
e) displaying the representation at a scale of 1:1,
said method comprising an algorithm implementing a bending-calculation formula including invariable parameters of said invariable geometrical parameters associated with said types of spinal column and wherein a radius of curvature s for the bending of the rod is calculated according to the following formula:
s
=
B
(
q
i
)
·
(
1
-
A
(
q
i
)
·
x
2
)
1
2
where the coefficients A(q i ) and B(q i ) are determined on the basis of the measurements acquired, of the type of spinal column and of said invariable parameters, and x is the spatial coordinate of the rod curvature in the picture or the projection.
2 . The method as claimed in claim 1 , wherein said distance and/or angle measurements comprise at least the measurement of a distance between vertebrae L4 and S1 and/or the distance between vertebrae L1 and S1.
3 . The method as claimed in claim 1 , wherein the said invariable parameters comprise a pelvis parameter and an inter-vertebrae distance.
4 . The method as claimed in claim 1 , wherein said distance and/or angle measurements comprise a pelvic tilt measurement.
5 . The method as claimed in claim 1 , wherein the spinal column is classified according to a type selected from four types of spinal column (TY1, TY2, TY3, TY4) defining models of lumbar lordosis, thoracic kyphosis, cervical lordosis, cervical kyphosis and neutral.
6 . The method as claimed in claim 1 , wherein the calculation for determining a geometry(s) for the bending of the rod is of the form:
s
=
f
n
(
q
i
)
the parameters q i being dependent on the measurements, on the type of spinal column and on invariables according to the types of spinal column.
7 . The method as claimed in claim 6 , wherein the function ƒ n (q i ) is produced from equations of circles, of ellipses, or of combinations of splines.
8 . The method as claimed in claim 7 , wherein said equations are integrated into a memory of a device for helping with bending a rod that can be implanted in the spinal column of the patient.
9 . The method as claimed in claim 7 , wherein said equations are adapted by the surgeon or the practitioner using a specific formula.
10 . The method as claimed in claim 1 , comprising the calculation of several successive radii of curvature of the rod.
11 . The method as claimed in claim 1 , wherein said invariable parameters are identified on at least one image of the back of the patient in a sagittal plane.