Due to the special characteristics of the development of the proximal femoral epiphyseal plate in children, the arterial blood flow to the femoral head is different at different ages, and in the age group of 3–4 years to 14–16 years, femoral neck fractures in children, especially displaced fractures, have a higher likelihood of developing complications such as AVN and osteochondromas than in adults, which seriously affects the prognosis of the children [8]. Complications can be minimized if the principles of early intervention, joint decompression, and anatomical reduction are followed, which can be minimized [9]. Hollow compression screws are the accepted method for surgically treating femoral neck fractures in patients of all ages. Performing good screw placement in youngsters is challenging due to the tiny diameter of the femoral neck in contrast to adults, and the traditional approach requires experienced orthopedic surgeons to perform the procedure empirically under fluoroscopy of a C-arm machine, even repeatedly adjusting the direction of insertion of the guide pins, which may decrease the stability of the proximal femur [10]. Meanwhile, repetitive exposure to X-ray radiation amplifies the occurrence of radiological harm to both patients and medical staff [11]. In order to improve the accuracy of hollow screw placement, prevent complications, and reduce radiological medical injuries, in recent years, because to advancements of orthopedic robots recently, the utilization of robot-assisted internal fixation insertion technology has become increasingly prevalent in surgical procedures for adult femoral neck fractures [12,13,14], which has been proven to be a more effective way of placing nails, and compared with the traditional bare-handed placement of nails, it has the ability to significantly decrease the amount of X-ray exposures during surgery and lessen the duration of the operation [15], and the postoperative screw parallelism and distribution are also better. Compared with traditional freehand nailing, it can significantly decrease the amount of X-ray exposure during surgery and lessen the duration of the operation [12], and the parallelism and distribution of the screws are better after the operation. Recently, there has been a growing trend in using robots to assist in the nailing method for treating femoral neck fractures in children [10], but there are still few reports on its long-term efficacy.
The optimal timing for surgical intervention in pediatric patients with fractures in the femoral neck is currently a subject of intense controversy, with most scholars believing that early 24-hour fixation should be performed. It has also been argued that in developing nations, where patients typically encounter problems such as delayed referrals and a lack of awareness, it is difficult to perform early fixation surgery within 24 h. However, early fixing within 24–72 h after the injury is critical in preventing complications [16]. Factors such as the extent of the original displacement, the presence or absence of comminution of the medial or posterior cortex, and the quality of the reduction have a role in the healing of fractures in children. These factors affect both the time it takes for the fracture to heal and the likelihood of nonunion occurring; and the probability of fracture healing progressively increases in a linear manner within the initial 6 months of the fracture healing period, and then levels off with an increase of less than 5% per month [17]. It has been noted that the incidence of complications (femoral head necrosis, premature epiphyseal closure, and acetabular dysplasia) is significantly higher in children with Delbet II femoral neck fractures in the presence of free fracture fragments than in those without free fracture fragments [18]. The occurrence of AVN in pediatric patients with femur neck fractures can be attributed to several factors, including age, fracture classification, level of displacement, operative time, and extent of reduction. However, there is a notable correlation between the degree of initial displacement and the likelihood of AVN [1, 19, 20].
Meta-analysis revealed that the overall occurrence of AVN following proximal femoral fracture in pediatric patients is about 22%, and age and fracture type are important factors affecting AVN [21]. The results of a multicenter study involving 239 pediatric femoral neck fractures showed a higher incidence of AVN in older children (12 years of age) and suggested that this phenomenon was mainly related to the intraosseous trophic vascular injury directly caused during femoral neck fractures in older children [22]. In pediatric femoral neck fractures, the mechanism of injury and fracture characteristics are age-related. Early reduction should be performed as early as possible according to the safety of the child, but trans-epiphyseal fixation should be avoided in younger children.AVN may be caused by the characteristics of the injury (Delbet typing) rather than by the choice of treatment modality [23]. However, a different point of view has been proposed by a study of Delbet type 2 fractures, which showed that factors pertaining to the treatment process, apart from the seriousness of the injury and the initial misalignment of the broken bone, did not have a notable impact on the occurrence of AVN, and it was concluded that age did not pose a risk for the development of AVN in those individuals [24].
On the other hand, whether the closed or open reduction of the fracture is a risk cause for AVN is currently controversial. For example, several scholars have conducted research on the effectiveness of postponing surgery for femoral neck fractures in children for a 24-hour period. They have also examined the factors that influence the risk of complications. The findings indicate that delayed reduction and fixation of the femur neck yield better results compared to the open reduction group. Additionally, fractures located closer to the femoral head and older age are correlated with an increased occurrence of AVN [25]. However, more scholars have concluded that open reduction does not aggravate the disruption of the blood supply of the femoral head and denied that the method of reduction is a risk cause for AVN after studying a large sample size (more than 70 cases) [26, 27]. Further literature analysis has concluded that open reduction and internal fixation is more accurate in reducing and fixing the fracture, with better clinical and functional outcomes, and lower complication rate [2].
An analysis was conducted on a pair of 686 pediatric patients who had proximal femur fractures, as well as 203 patients with avascular necrosis (AVN) from 21 articles. The analysis focused on examining the clinical and radiological characteristics of these patients. The mean interval of progression to AVN was 13.7 ± 9.5 months. After being diagnosed with AVN, 59.1% of individuals had no symptoms, but 65.2% of cases eventually experienced collapse [28].
Although this study is a retrospective study, the baseline data such as the duration between the injury and the surgical procedure, the follow-up time, and the quality of fracture reduction in the two groups of children was examined, and the differences were found to be statistically insignificant and equivalent. The findings indicated that the observation group was able to significantly reduce the amount of X-ray exposures during surgery and the number of guide pin placements when nailing was performed under robotic navigation. In the observation group, the first postoperative X-ray showed a notable improvement in the parallelism and distribution of screws, in comparison to the control group. These differences were of statistical significance. The duration of the procedure in the observation group was somewhat longer than that in the control group, which was related to the time-consuming operations such as the debugging of the robotic navigation equipment, the acquisition of images, and the planning of screw placement paths, etc. In fact, the time consumed during the period from the insertion of the guide pin to the completion of the insertion of the hollow screws in the observation group was less than that of the control group, which was reflected by the number of exposures and the amount of times of insertion of the needles. Nevertheless, the disparity in total operation time between the two groups did not exhibit any statistically significant variation.
AVN is considered to be the most devastating and common postoperative complication that often follows femoral neck fractures in children. It typically arises as a result of additional issues, such as early closure of the growth plate, the use of hip implants, or the shortening of the limb. The most important factor contributing to AVN is the extent of vascular damage sustained during the traumatic event, which is directly linked to the extent of initial displacement of the fracture and the classification of fracture; on the other hand, it may be related to medical interventions such as the duration between the injury and the surgical procedure, surgical protocols, and methods of immobilization [10]. AVN in children can usually be detected within 1 year after surgery, but some studies have reported that it may appear two or more years after injury [29]. In this study, every patient was monitored for a duration exceeding two years, which is a long-term efficacy observation. The study results showed that the occurrence of complications in the observation group was 31.82%, which was lower than the 48.48% in the control group. Nevertheless, the difference between the two groups did not reach statistical significance. The authors suggest that the absence of a meaningful outcome may be ascribed to the study’s small sample size.
It is worth stating that premature epiphyseal closure is a unique complication of femoral neck fracture in children resulting from epiphyseal injury, but whether the hollow screws need to be fixed through the epiphysis in order to assure the stability of the fractured end of the femoral neck is a controversial topic, and it is generally believed that children under the age of 10 who wear epiphyseal fixation will increase the risk of premature epiphyseal closure [30]. In the present study, some patients aged 11–16 underwent intraoperative epiphyseal fixation with hollow screws to ensure solid fixation of the fracture ends, and no cases of premature epiphyseal closure or hip endosteolysis occurred during the follow-up period.
The recovery of hip function in children was correlated with whether the femoral neck fracture healed or not, whether complications occurred or not, and the severity of complications. In this study, at the last follow-up, the observation group had a considerably higher rate of excellent hip function according to the Ratlif criterion (90.91%) compared to the control group (78.79%), and the difference was statistically significant, indicating that robotic-guided nailing was favorable to the recovery of their hip function.
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