Long bone fracture reduction and deformity correction using the hexapod external fixator with a new method: a feasible study and preliminary results

Abstract

Background: The hexapod external fixator (HEF), such as the Taylor spatial frame (TSF), offering the ability of multidirectional deformities correction without changing the structure, whereas there are so many parameters for surgeons to measure and subjective errors will occur inevitably. The purpose of this study was to evaluate the effectiveness of a new method based on computer-assisted three-dimensional (3D) reconstruction and hexapod external fixator for long bone fracture reduction and deformity correction without calculating the parameters needed by the traditional usage.

Methods: This retrospective study consists of 25 patients with high-energy tibial diaphyseal fractures treated by the HEF at our institution from January 2016 to June 2018, including 22 males and 3 females with a mean age of 42 years (range 14-63 years). Hexapod external fixator treatments were conducted to manage the multiplanar posttraumatic deformities with/without poor soft-tissue that were not suitable for internal fixation. Computer-assisted 3D reconstruction and trajectory planning of the reduction by Mimics were applied to perform virtual fracture reduction and deformity correction. The electronic prescription derived from the length changes of the six struts were calculated by SolidWorks. Fracture reduction was conducted by adjusting the lengths of the six struts according to the electronic prescription. Effectiveness was evaluated by the standard anteroposterior (AP) and lateral X-rays after reduction.

Results: All patients acquired excellent functional reduction and achieved bone union in our study. After correction, the mean translation (1.0 ± 1.1 mm) and angulation (0.8 ± 1.2°) on the coronal plane, mean translation (0.8 ± 1.0 mm) and angulation (0.3 ± 0.8°) on the sagittal plane were all less than those (6.1 ± 4.9 mm, 5.2 ± 3.2°, 4.2 ± 3.5 mm, 4.0 ± 2.5°) before correction (P < 0.05).

Conclusions: The computer-assisted three-dimensional reconstruction and hexapod external fixator-based method allows surgeons to conduct long bone fracture reduction and deformity correction without calculating the parameters needed by the traditional usage. This method is suggested to apply in those unusually complex cases with extensive soft tissue damage and where internal fixation is impossible or inadvisable.

Keywords: Computer‐assisted; Fracture reduction; Hexapod external fixation; Taylor spatial frame; Three‐dimensional reconstruction.

Fig. 1

3D reconstruction and registration of the whole model. a 3D reconstruction of the bilateral tibia and the TSF. The green tibia is the mirror of the contralateral tibia. b Registration of the proximal bony fragment and mirrored image of the contralateral tibia. c, d Registration of the standard ring and the 3D model of the actual ring. e Merge of the bony fragment and the corresponding ring

Fig. 2

Flowchart of the trajectory planning for fracture reduction. a Original position of the whole model. b Extension of the distal part. c Rotation of the distal part. d Reduction of the distal part. e Schematic image of the whole planning

Fig. 3

Position changes of the distal ring before and after reduction. a AP view of the whole model. b Lateral view of the whole model. c Separation of the bony fragment and the corresponding ring from the two parts. d Calculate the length of the six struts in SolidWorks

Fig. 4

Images of a 54-year-old man with posttraumatic multidimensional deformities in tibia and fibula treated by the hexapod external fixation (HEF). a Posttraumatic AP and lateral views of X-rays. b Radiographs immediately after application of HEF. c Patient in HEF with an open wound and preoperative hemorrhagic fracture blisters seen. d Radiographs after final correction

Fig. 5

Follow-up images of the same patient after removing the HEF. a Radiographs one month later. b, c Clinical images of the patient, obtained at 13 months after HEF removal