A Two-Step Approach for 3D-Guided Patient-Specific Corrective Limb Osteotomies

Abstract

Background: Corrective osteotomy surgery for long bone anomalies can be very challenging since deformation of the bone is often present in three dimensions. We developed a two-step approach for 3D-planned corrective osteotomies which consists of a cutting and reposition guide in combination with a conventional osteosynthesis plate. This study aimed to assess accuracy of the achieved corrections using this two-step technique. Methods: All patients (≥12 years) treated for post-traumatic malunion with a two-step 3D-planned corrective osteotomy within our center in 2021 were prospectively included. Three-dimensional virtual models of the planned outcome and the clinically achieved outcome were obtained and aligned. Postoperative evaluation of the accuracy of performed corrections was assessed by measuring the preoperative and postoperative alignment error in terms of angulation, rotation and translation. Results: A total of 10 patients were included. All corrective osteotomies were performed according to the predetermined surgical plan without any complications. The preoperative deformities ranged from 7.1 to 27.5° in terms of angulation and 5.3 to 26.1° in terms of rotation. The achieved alignment deviated on average 2.1 ± 1.0 and 3.4 ± 1.6 degrees from the planning for the angulation and rotation, respectively. Conclusions: A two-step approach for 3D-guided patient-specific corrective limb osteotomies is reliable, feasible and accurate.

Keywords: 3D printing; 3D technology; corrective osteotomy; malunion; osteotomies; patient-specific; patient-specific instruments; surgical guide; three-dimensional; virtual surgical planning.

Figure 1

Workflow of a 3D-guided patient-specific corrective osteotomy using a two-step approach. (1) First, a 3D reconstruction is made from a bilateral CT scan. (2) By mirroring and aligning the contralateral (healthy) side on the malunited bone (orange), the deviation is measured. (3) Based on the deviation, the osteotomy and the correction are planned. (4) An osteosynthesis plate is chosen and positioned on the bone after correction. (5) K-wires are positioned parallel on the planned correction. (6) K-wires are placed parallel on the corrected bone, duplicated and moved to the corresponding position on the malunited bone before the correction is performed. (7) Patient-specific cutting and reposition guides are designed. (8) 3D-guided osteotomy is performed using the patient-specific cutting guide. Subsequently, the cutting guide is removed and the reposition guide (including the plate) is slid over the K-wires to achieve the intended correction.

Figure 2

3D-guided patient-specific corrective osteotomy of a malunited distal radius that was initially treated conservatively in a cast (Case 6). (a) Frontal and lateral view of the designed cutting guide (pink) with the -wires (red); (b) frontal and lateral view of the designed reposition guide (purple) with the parallel K-wires (red); (c) operative usage of the cutting guide; (d) operative usage of the reposition guide. The specific design of the reposition guide allowed for at least two screws to be drilled and placed both distal and proximal to the osteotomy level. Note the convergent K-wires in the cutting guide (c), and the parallel K-wires as reduction aids in the reposition guide (d).

Figure 3

3D-guided patient-specific corrective osteotomy of a proximal tibia (Case 8). (a) Frontal view of the designed cutting guide (pink) with the K-wires; (b) lateral view of the designed reposition guide (purple) with the parallel K-wires and insertion of the planned wedge; (c) operative usage of the cutting guide; (d) operative usage of the reposition guide.

Figure 4

Evaluation of the achieved correction in terms of angulation and rotation. (a) First, the inertia axes were determined; (b) the angulation was then determined by measuring the angle between the z-axis of the preoperative (yellow) and planned (green) position of the bone, and between the planned and the postoperative (red) position; (c) the rotation was determined by measuring the angle between the x-axis of the preoperative and planned position, and the planned and postoperative position.