Definition of the Angle-Signs:

In the following sign definition examples, the green bone represents the sane tibia (right side of the body). The white left side of the body tibia is bent according to the example of sangeorzan Sangeorzan (Biomech) 1989 Fig. 3.

:

Coronal Front sign definitions

Sagittal Front sign definitions

Transverse sign definitions

The application of the calculation results must follow these guidelines:

Sign rule for angle Phi

• Start from the coronal plane (0°). From there the positive rotation is defined in lateral direction.

As a consequence of this rule, the sign of Phi of the calculation result is correct for the left side of the body bones and changes for the right side of the body bones.

Left side of the body bone:

For the rotation of the cutting plane, the sign rule for angle Phi (Rotation Z) a positive result leads to a positive rotation around the Z-axis in the plane of no deformity coordinate system (C1) which is chosen according to Sangeorzan (Biomech) 1989 Fig. 3.

Right side of the body bone:

For the rotation of the cutting plane, the sign rule for angle Phi a positive result leads to a negative rotation around the Z-axis in the plane of no deformity coordinate system (C1) which is chosen according to Sangeorzan (Biomech) 1989 Fig. 3. Therefore the calculation result value for angle Phi must be entered with inverse sign to determine the position of the rotation axis of the cutting plane for right side of the body bones.

References

ref 1

Sangeorzan BJ, Sangeorzan BP, Hansen ST, et al: Mathematically Directed Single-Cut Osteotomy for Correction of Tibial Malunion. J Orthop Trauma 3:267-275, 1989.

ref 2

Sangeorzan BJ, Judd RP, Sangeorzan BJ: Mathematical Analysis of Single-cut Osteotomy of Complex Long Bone Deformity. J Biomech 22:1271-1278, 1989.

ref 3

Dobbe JG, Pre KJ, Kloen P, et al: Computer-assisted and patient-specific 3-D planning and evaluation of a single-cut rotational Osteotomy for complex long-bone deformities. Med Biol Eng Comput 49:1363-1370, 2011.

ref 4

J. G. G. Dobbe, K. J. du Pre´, L. Blankevoort, G. J. Streekstra, P. Kloen: Computer-assisted oblique single-cut rotation osteotomy to reduce a multidirectional tibia deformity: case report Strat Traum Limb Recon (2017) 12:115-120