Intertrochanteric femoral fracture is prevalent among the elderly population, and usually requires surgical treatments. To date, the ideal implant for the treatment of intertrochanteric fractures remains controversial [19]. PFNA-II has been considered a well-developed surgical technology in the treatment of intertrochanteric femoral fractures [13, 20]. Although this kind of surgery is relatively easy to accomplish for experienced surgeons, it is still challenging for beginners. When performed by young surgeons, operative failure and loss of self-confidence may occur because of insufficient assessment of bone fragments and inappropriate selection of implants. Therefore, accurate preoperative design at the early learning stage is particularly important. Because it could help lower the learning difficulty and increase self-confidence in beginners. This study was performed to validated whether CAPP could help reduce the learning difficulty of PFNA-II treatment of intertrochanteric femoral fractures of beginners.
In conventional preoperative planning, the 3D morphological characteristics of fractures are imagined by surgeons based on 2D images (radiographs, CT scans or magnetic resonance imaging (MRI) slices). This kind of preoperative planning relies on the clinical experience and subjective imagination of surgeons, which may be distorted and inaccurate. Many studies investigated novel preoperative planning methods in order to improve the efficiency and effectiveness. One of them was 3D printing technology. A 3D printing model can provide a direct and interactive display of fracture characteristics, and can be used to perform virtual procedures in vitro such as fracture reduction and simulation surgery [21]. However, this technology is available for only a few patients because it is expensive and time consuming, which limited its clinical applications. Okada et al. [22] described a method that extract fracture lines based on 3D curvature analysis. It was used for the repositioning and registration of bone fragments in proximal femoral fractures. This provided a new model of preoperative planning for computer-guided fracture reduction.
Our CAPP system could show the fracture characteristics of patients and pre-perform surgical procedures (including fracture reduction and implantation simulation) in a direct and virtual manner. Moreover, the system enables 3D morphological measurements of the femoral head, shaft, and diameter of femur after reduction, which could directly guide the selection of implants. The average CAPP time was < 1 h, which was not time-consuming. A previous study [23] has also demonstrated that CAPP based on virtual surgical technology has several advantages, including shorter preoperative planning time, shorter interval from injury to surgery, and shorter duration of hospital stay, in the treatment of proximal humeral fractures.
CT/3D CT data are necessary for reconstruction and assessment in the CAPP system. Plain radiographs have some limitations; for example, coronal fragments are difficult to identify on radiographs [24]. However, knowing the incidence and morphology of coronal fragments are important to avoid potential intraoperative pitfalls. Although plain radiographs may reveal fracture details with a relatively lower cost for patients, CT/3D CT examination was more reliable and helpful for preoperative assessment, especially for intramedullary fixation [25].
Learning curves are important for surgeons to understand and master a certain surgery with a specific device. Our hypothesis was that surgical experience has significant effects on the operative time. The results showed that with the accumulation of surgical experience, the operation time gradually decreased and the learning curve for intramedullary fixation with PNFA-II became acceptable. As shown in Fig. 3, the learning curve of CAPP group was steeper than that of the conventional group, indicating that the surgical procedure could be managed faster with less surgical volume with the assistance of CAPP. Such conclusions were consistent with those of other similar learning curve studies [26, 27]. The average operation time with a learning curve effect was about 40 min, consistent with other previous studies [20].
Observing and performing operations are important parts of surgical training in the orthopedic field [28]. PFNA treatment is a highly standardized procedure, and is often used for training younger surgeons. The common way of training is to allow residents to perform operative procedures under the supervision of senior surgeons. Cases involving patients with morbidity, osteoporosis and the trauma setting are often challenging problems for beginners. Thus, a direct and virtual way for simulating surgical procedures has great value. Previous studies revealed an increasingly important role of surgical simulators [29, 30] as well as virtual reality assistants [31] in the surgical training of orthopaedic resident. Although the CAPP system in this study only served as a useful tool for preoperative design, we believe that it might have the potential to become a routine part of resident education in orthopaedic surgery. Residents could learn surgical procedures by observing senior surgeons, performing surgical simulation with CAPP, and conducting actual operations step by step. Further studies investigating the organic integration of CAPP and virtual reality display could guide the path for more efficient and precise preoperative designs.
Moreover, the application of CAPP enables preventing lateral femoral wall fracture during the operation. The lateral femoral wall, firstly introduced by Gotfried [32], has gain its recognition by orthopaedic surgeons in the treatment of intertrochanteric fractures. Im et al. [33] used dynamic hip screws (DHS) to treat 66 patients with intertrochanteric fractures classified as AO/OTA type 31-A1. Nine patients had comminution of the lateral cortex either during the operation or postoperatively. Palm et al. [34] reported about the integrity of the lateral femoral wall as a main predictor of reoperation. Hsu et al. [35] demonstrated that lateral femoral wall thickness is a reliable predictor of postoperative lateral wall fracture in intertrochanteric fractures. And intertrochanteric fractures with a lateral wall thickness < 20.5 mm should not be treated with DHS alone. The intact lateral wall has played a key role in preoperative reduction, implants selection and postoperative stability of internal fixation in unstable intertrochanteric fractures. Therefore, maintaining the integrity of the lateral wall should be an important objective in all stabilization procedures for unstable trochanteric fractures. Compared with the conventional preoperative planning, CAPP has shown excellent effects in terms of maintaining the integrity of the lateral femoral wall during the preoperative designs processes. In the CAPP group, there were no lateral wall fractures during the operation and postoperatively.
Patients in the CAPP and conventional group all performed functional exercises after surgery. The Harris score at 1-year follow-up showed satisfactory clinical effects (88.64 ± 2.79 and 87.60 ± 3.02 in the CAPP and conventional groups, respectively). Especially, the Harris score in AO/OTA type 31-A2 intertrochanteric fractures of the CAPP group was significantly higher than that in the conventional group. CAPP has the potential to improve the clinical outcomes of PFNA-II treatment of intertrochanteric fractures, especially in comminuted fractures with separated greater and lesser trochanters, and varus deformity. However, according to the AO/OTA-2018 classification, type 31-A2 fracture (trochanteric region fracture) are defined as multi-fragmentary per-trochanteric lateral wall incompetent (≤ 20.5 mm) fracture [36]. This might lead to bias because the type 31-A2 fracture in AO/OTA-2007is totally different from that in the new classification. AO/OTA-2018 stressed the importance of the lateral wall by using the involvement of lateral wall as classification basis not the lesser trochanter fragments.
Previous studies have demonstrated that extended and progressive exercise can significantly promote the rehabilitation of limb function and improve the quality of life [37]. Postoperative rehabilitation exercise in elderly patients are important for the limb function recovery. In addition, postoperative complications showed no significant differences between the two groups. The complication rates were similar with those reported in previous studies [20, 38].
This study has some limitations. First, many factors could influence the operation time, including the complexity of fractures. Because complicated fracture would increase the operation time, surgeons at the early stages of the learning curve usually choose relatively simple and typical cases, which is conducive to mastering the surgical technique and improving self-confidence. This may lead to bias because complex cases are rare. Randomized studies are needed to reduce the selection bias. However, as this was a retrospective study, the bias was difficult to eliminate. This will inevitably affect the evaluation of the learning curve. Second, potential bias due to difference in the skill level of surgeons could exist, because we could not expect the two surgeons to be “identical clones”. However, this was an inherent limitation of this kind of study to investigate an impact on the learning curves regardless of prospective or not, like investigating the impact of training level on the learning [39]. Considering the non-divergent characteristics of included patients, as well as the same medical background and surgical exposure of the two surgeons, we still believe that the current study is qualified to clarify the topic. Third, the follow-up evaluations were performed in the outpatient setting and, some patients in both groups were lost to follow-up. This may have affected the evaluation of the postoperative patient-reported outcomes. In addition, the follow-up time is not sufficient for the long-term evaluation of function. Lastly, the CAPP system is not popular, and our results could only represent the improvement of clinical skills at our institution. Potential bias may also exist in this regard. Further multi-center prospective and randomized studies are needed to evaluate the importance of CAPP in improving the learning curves of PFNA-II treatment of intertrochanteric fracture patients.