Accurate operative procedures of DDH are technically challenging for surgeons. It is well accepted that derotational femoral shortening osteotomy is always necessary to facilitate the open reduction of DDH, especially in high dislocations and older children, correct unnormal femoral anteversion angle, reduce excessive pressure on the femoral head, and decrease the intraoperative instability of the hip . In the guide-pins method one pin was inserted into proximal and the other distal to the osteotomy position [10, 11]. When the distal pin lies parallel to the proximal pin, the desired derotation of the femur was achieved. The rate for overcorrection of affected legs was 44% and and 15% for undercorrection, respectively. In the present study, we achieved satisfactory results in 15 cases by using 3D navigational template.
In order to complete the operation safely and achieve the desired effect of DDH, it is crucial to acquire as much deformity information in various situations as possible. Radiography, 2D or 3D CT images alone cannot provide sufficiently accurate information about complex hip deformities [12, 13]. Individual differences in femoral size and shape are also affect the accuracy of osteotomy. Furthermore, due to limited exposure of lateral cortex of the proximal femur, performing derotational femoral shortening osteotomy accurately remains challenging . Computer-aided navigation is an effective and useful tool to improve the accuracy of operation [15, 16]. However, they are expensive equipment, time-consuming procedures and have a significant learning curve.
Recently, many 3D navigation templates have been introduced in the trauma, joint and spine fields [17–19], but only a few researchers have reported their applications in the pediatric orthopedic disorders. Previously, different personalized templates have been designed for cubitus varus deformity and achieved wonderful clinical outcome [20–22]. Lu et al.  developed a novel patient-specific template in congenital scoliosis and validated the accuracy and safety. More recently, Otsuki et al.  constructed 3D custom cutting guide for curved peri-acetabular osteotomy. With its accurate guide, this template was considered to avoid serious complications associated with osteotomy. Compared with other templates, the present study had applied a novel personalized navigation template in proximal femoral corrective osteotomy for the treatment of DDH and validated the efficacy and safety in clinical settings. Neither redislocation nor avascular necrosis were detected in the navigation template group, which had more accurate osteotomy degrees, less radiation exposure, and shorter operation time when compared with the conventional group (P < 0.05). Moreover, there was significant difference according to the McKay criteria between the two groups (P = 0.0362).
The advantage of the 3D navigation template is that it is simple and easy to apply which can be performed without much expertise and special training. Moreover, the template can be used during surgery to assist surgical navigation and accurate osteotomy. Lastly, we can check the accuracy of individual template with the aid of 3D printing model before surgery, thereby eliminating the need for repeated manipulates and shortening the surgical time. Besides, fewer radiographs are needed and continual fluoroscopic monitoring can be avoided intraoperatively.
Nevertheless, because the 3D navigation template is developed based on a preliminary series, it has several limitations in the present study. On the one hand, muscle and fat tissue on the bone can affect the position of the template. So an exact preparation of the bone surface was essential and the template should fit tightly to the corresponding lateral femur to allow accurate drill trajectories. Furthermore, more cases and multi-center prospective studies in future are needed to evaluate the accuracy and efficacy of the 3D navigation template. In addition, it is necessary to further prolong the follow-up time because the patients in our study were still at the stage of skeletal immaturity.