Accurate Preoperative Digital Planning: The First Mandatory Step to Success in Complex and Unusual Total Hip Arthroplasties

Commentary Total hip arthroplasty (THA) in a young population with abnormal proximal femoral morphology, such as due to Legg-Calvé Perthes disease, is always challenging. The young age, the femoral deformity, the small size of the femoral shaft, the potential severe leg length discrepancy, etc., explain the difficulties with the surgery and the substantial risk of early or delayed complications1,2. Several implants and surgical techniques have been developed to manage these complex hips, such as a customized stem, shortening femoral osteotomy, or trochanteric osteotomy. Even if these surgical techniques are very interesting and attractive for severe hip deformities, they can lead to dramatic complications and residual disability3. They should be used only as a last resort. Most of the time, difficulties with complex surgery should be solved with standard implants and surgical techniques that the surgeon can better control. Kayani et al. reported a high rate of long-term survival of the Wagner Cone Prosthesis for abnormal proximal femoral morphology. Their patients had no stem-related aseptic loosening or mechanical complications except for 1 case of hip dislocation. Only 3.8% of patients had stem subsidence of 5 mm or more during the first 12 months, which was asymptomatic in all cases, and 1.25% had a nondisplaced intraoperative femoral fracture during bone preparation, requiring cerclage wires and partial weight-bearing. These excellent results demonstrate the relevance of the indication and the type of implant used. The femoral stem used in this series was not standard, but a monoblock conical prosthesis for which femoral preparation was close to that for a standard stem. The strength of this study is the high number of included patients with long-term follow-up for an uncommon pathological condition. Even without a control group, the results in this large series with complex THA were interesting and reliable and validate the relevance of the surgical strategy, with a monoblock conical stem and without osteotomy. Kayani et al. determined the required implant and surgical technique before the surgery, although they did not explain the preoperative templating. The main question is how to determine which procedure and implant you need for these complex, unusual hip deformities. Specific implants, particularly customized ones, require time to be produced; the decision cannot be made in the operating room on the morning of the surgery. The principle is the same for the surgical technique; hip osteotomies are not always easy and intuitive and should be planned before the surgery. Preoperative planning is thus crucial to anticipate the required implant, the potential femoral osteotomies and their localization, and the degree and axis of correction. But when and how do you perform reliable surgical planning before the surgery? Preoperative planning must be systematic before every THA, including simple ones. We do well what we do often. Plan for every hip so that you will be ready when you need to plan for a complex and unusual hip. Several preoperative planning software programs have been developed in 2D with calibrated radiographs or in 3D with preoperative computed tomography (CT); 3D planning is more attractive and reliable thanks to the assessment of the 3 planes4,5. Nevertheless, surgeons are less accustomed to 3D planning and can sometimes be less accurate than when they use traditional radiography. Therefore, the learning of 3D planning must be combined initially with radiograph-based planning. The current software allowing 3D planning is that used for robotic-assisted systems or software for customized implants or cutting guides, but not all implants can be used with these systems. The scale of the preoperative image (radiograph or CT scan) must be known and precise to perform reliable scaled planning. The surgeon can perform several types of surgical planning for these complex cases of abnormal proximal femoral morphology to determine the best option to position the hip rotation center well, restore an adjusted femoral offset, and correct leg length discrepancy as well as possible with an appropriate size of femoral stem. Kayani et al. probably planned their surgical procedures well, because they had very few perioperative complications. However, we do not know if they needed to make some changes during the surgery such as an unplanned osteotomy or implant. This robust study brings to light 2 primary points. First, preoperative surgical planning is essential for complex surgery, particularly THA on abnormal proximal femoral morphology, to anticipate the required implants and surgical technique. Second, simple surgery and typical implants must always be preferred, if possible, to avoid unnecessary complications.