## 4 Discussion  
External fixators are widely used in orthopedics and allow for gradual correction, based on distraction osteogenesis (DO), for fracture reduction and deformity correction [19; 20]. In terms of the configuration of the external fixator, the Ilicarov external fixator is the most mature ring fixator in clinical applications. It is a modular reconfigurable medical device in the mechanical sense. One of its main characteristics is that it can assemble a frame configuration that meets clinical needs through component assembly and configuration design according to different indications, which makes the Ilicarov frame have the advantages of flexible component assembly and diverse configuration designs. However, due to the complexity of the structure and the diversity of bone deformities, the Ilicarov frame technology requires a high level of clinical experience and medical skills, which makes the clinicians' learning curve for the use of the external fixator longer [5; 21]. The external fixator is suitable for single-plane deformity correction, not multi-plane correction, and has achieved good clinical results, especially in limb lengthening [22; 23]. The TSF (Taylor Spatial Frame) external fixator based on the Stewart platform can achieve spatial six-axis correction and can maintain continuous stability during the correction [5; 8]. It has high transverse stiffness and accurately repeated positioning accuracy, which is conducive to bone growth. Besides, it has strong posture manipulation capabilities and a closed kinematic solution, which has been widely promoted and applied in the field of orthopedic deformity correction. The main advantage of TSF is that it has universal applicability to deformity and can be used for single-plane deformity correction as well as multi-plane complex deformity correction. In addition to TSF, which is widely used in clinical applications and research, Ortho-SUV Frame (OSF) [24; 25], PoliHex [12], TL-Hex [26], etc. are also well known. Traditionally, the rods' lengths are operated manually by the patient several times a day during the healing process. This involvement of the patient will ensure the patient's compliance and accumulative adjustment error. To reduce the patient's daily compliance with the external fixator caused by manual adjustment, [PERSON] et al. [12] developed an \"intelligent\" external fixator for fracture reduction, which allows movements of the bone fragments in all six degrees of freedom. [PERSON] et al. [27] reclassified fracture types using a stereolithography model and developed a teleoperation robot system based on visual servos to verify the effectiveness of the preoperative reduction path with fracture reduction experiments. [PERSON] et al. [14] used an infrared tracking system to measure the positioning accuracy of a Hexapod(r) fixator and verified that the external fixator has high accuracy. Several researchers have described the advantages and precision of similar mechanisms [13; 14; 15]. [PERSON] et al. [28]. investigated the effect of external fixator configurations on the dynamic compression load through an experiment and numerical study. The accuracy of the external fixator during the implementation of the preset correction trajectory is also the main problem to be solved at present. The developed electromotor driven parallel external fixator allows the deformity correction of any multi-planar deformity. In terms of mechanical structure, the lead screw is adopted with a single thread T thread (\(p=1\) mm), which has a good self-locking function. To increase the flexibility of the structure and avoid joint abrasion during correction, rolling bearings are used at screw nuts, Hooke hinges, and spherical joints. The control system adopts the distributed control mode of upper computer + lower computer, which makes it possible to automatically adjust the external fixator according to the correction strategy.