The goal of ideal corrective surgery for DDH in children is to achieve concentric reduction of the hip and avoid avascular necrosis (AVN), which is a technical challenge for orthopaedic surgeons [15,16,17,18]. It is now well accepted that one of the most effective strategies for the management of DDH is proximal femoral varus osteotomy with LCP-PHP [19]. However, it is more challenging to perform the surgery into the narrow proximal femur for DDH patients. Therefore, preoperative planning for proximal femoral varus osteotomy is very crucial. The main finding of this study was that the VSS can greatly decrease surgery time and radiation exposure for proximal femoral varus osteotomy. In a word, this is the first study to assess the preoperative planning of VSS and clinical outcomes for proximal femoral varus osteotomy of DDH.
With the development of orthopaedic instruments, LCP-PHP has become widely used to reach a more precise angular correction with locking screws [20]. However, implantation of LCP-PHP requires a long learning curve. Firstly, individual differences in proximal femoral size, the neck-shaft angle, and the femoral anteversion add to the difficulty of the implantation of LCP-PHP, and thus preoperative calculation and measurement of these angles for individualized surgical design are essential. In the conventional group, the neck-shaft angle was assessed on pelvic X-ray while femoral anteversion was measured via spiral CT scan and three-dimensional reconstruction of the femur using specific scan parameters (120 kV; 120 mAs; 1-mm-thick slices, 0.5 mm interlamellar spacing). Besides, the pin angle and depth of LCP-PHP intra-operatively need to be adjusted several times to achieve ideal position, which may prolong the operative time and increase the risk of iatrogenic vascular and nerve injury. Finally, X-ray or CT was not sufficient to provide accurate information for preoperative simulation or intra-operative design of DDH. Therefore, new techniques for implanting LCP-PHP are urgently needed, which must be practical, precise, and easy to promote.
Various navigation templates using 3D printing technology have been applied for the treatment of DDH in children, however, more bone markers are needed to increase the degree of fitting and the stability of the plate [3, 6, 7, 21]. Currently, the virtual surgical protocol formulation for preoperative planning of DDH was few reported [8]. Therefore, in the present study, we used VSS to improve the efficacy and precision of proximal femoral varus osteotomy with LCP-PHP in DDH. Based on CAD and 3D reconstruction, the advantages of VSS for proximal femoral varus osteotomy with LCP-PHP are as follows: (1) The orthopaedics surgeon can observe the pathological conditions of the proximal femur clearly in every direction and measure the excessive neck-shaft angle and femoral anteversion accurately before surgery. Meanwhile, the preoperative surgical plans and proximal femoral varus osteotomy with LCP-PHP can be simulated and modified. (2) The virtual surgical protocol formulation can help the orthopaedics surgeon perform the surgical operation process proficiently and make the intra-operative design appropriately, which can not only reduce the radiation exposure and operation time, but also improve the accuracy and safety of the surgery. (3) Fully understanding proximal femoral varus osteotomy with LCP-PHP via VSS can help parents understand their children’s medical condition while promoting doctor-patient communication. Moreover, it could also be a tool to train young doctors to improve surgical skills and academic communication for proximal femoral varus osteotomy.
Nevertheless, there were some limitations in the present study. First, more cases are required to evaluate the accuracy and efficacy of VSS for DDH because no significant difference was demonstrated for clinical outcomes or correction angle between the VSS and conventional groups. Besides, simulated operation on the 3D printing model or patient-specific instrument should be performed in future studies, which could increase its clinical value in orthopaedics surgery. Second, discrepancy in the collection angles between the preoperative planning and postoperative CT measurement and comparison of the epiphyseal growth plate violation rate between the groups should be included in the comparative analysis. Third, the femoral anteversion angle was also crucial for proximal femoral varus osteotomy and it would be better to present the data of the femoral anteversion angle before and after surgery during the VSS surgery. Meanwhile, the VSS could not be only used for proximal femoral varus osteotomy, the pelvic osteotomy or other pediatric hip diseases will also be taken into account to assess the VSS’s effect in our following study.