A recent meta-analysis described the complications of femoral neck fractures in young adult patients; the reoperation rate was approximately 18%, the nonunion rate was approximately 9%, the avascular necrosis rate was approximately 14%, and the implant failure rate was nearly 10%. Although surgical techniques, instruments and imaging methods have improved, complications such as nonunion (10–30%) and AVN are still evident in 15–33% of patients[10, 11]. Most reports of nondisplaced fractures (Garden classification stage I and stage II) show high rates of union and few complications, with nonunion and AVN rates of less than 6%[12, 13]. We found that open reduction and triangle cannulated screw fixation via DAA results in an 81.1% of excellent and good outcomes rate in a series of irreducible femoral neck fractures, with a nonunion rate of approximately 5.4%, an avascular necrosis rate of 16.2%, and an implant failure rate of nearly 8.1%.
Open Reduction and Internal Fixation (ORIF) or Closed Reduction and Internal Fixation (CRIF)
Whether closed reduction or open reduction is ideal for femoral neck fractures is still controversial. A total of 17 case-control studies with 2065 patients were reviewed, and it was revealed that AVN after the operation presented no association with the patient’s age, injury-operation interval, fracture reduction mode, preoperative traction or mechanism of injury. During the operation, it is difficult to anatomically reduce a displaced femoral neck fracture in a closed reduction pattern. If closed reduction is used repeatedly, the blood supply of the femoral head will be damaged. Therefore, we agree that to reduce the risk of complications such as AVN, nonunion, implant failure, anatomical reduction and stable internal fixation, only anatomical reduction should be performed. Normally, a varus angulation of less than 160° in the AP view and a posterior angulation of more than 5° in the lateral view indicate an unsatisfactory reduction. If anatomical reduction cannot be achieved after 2–3 closed reductions, open reduction and internal fixation should be performed. Open reduction allows direct and controlled treatment of fractured fragments. Stone JD et al.  treated fully displaced femoral neck fractures in pediatric patients with open reduction and internal fixation (ORIF), and the authors observed a significantly higher quality of reduction than that with closed reduction and internal fixation (CRIF) and subsequently fewer complications, including AVN of the femoral head.
In addition, intracapsular hematomas, which may lead to a high intra-articular pressure, block the blood supply of the femoral head in the acute stage after injury, and eventually lead to avascular necrosis of the femoral head, can be removed with the open surgical approach.
Bonnaire Fet al. measured the intraarticular pressure of 55 patients with intracapsular femoral neck fractures and found that hemarthrosis caused increased intraarticular pressure in 75% of the patients. Moreover, no significant difference was found between nondisplaced and displaced fracture types. There is sufficient evidence in the literature showing a correlation between increased intraarticular pressure following femoral neck fractures and reduced perfusion of the femoral head[18, 19]. Based on the data available, we supposed that capsular decompression by capsulotomy can compromise circulation in the femoral head.
Femoral neck fractures with good fracture reduction heal more quickly than those with poor reduction. Moreover, the anatomical reduction of fractures is easier to achieve when a larger area at the fracture site is exposed.
The anterolateral (Watson-Jones approach) and Smith-Petersen approaches are the two most frequently used approaches for femoral neck fractures. Smith-Petersen is a commonly used approach for deep circumflex iliac artery bone grafting . However, this incision leads to a large amount of damage, so it is not suitable for patients who do not need bone flap transplantation. The modified Smith-Petersen approach, also known as DAA, is widely used in anterior hip arthroplasties. Ye Ye et al. suggested that this is an internervous approach between the femoral nerve and superior gluteal nerve, and it can provide an excellent visualization of the whole femoral neck fracture and placement for a medial buttress plate.
A study of exposure measurements of fresh-frozen human pelvises that underwent both the modified Smith-Petersen and Watson-Jones approaches revealed that the modified Smith-Petersen approach provided much better visualization and palpation of the medial femoral neck and articular surface than did the Watson-Jones approach.
One of the advantages of the Watson-Jones approach is that the fracture can be exposed under direct vision and the surgeon can directly reach the femoral site through the incision made with this approach. This approach is suitable for most basal neck fractures and transcervical fractures, and it is also recommended that an implant is placed in the lateral femur. Other authors believe that the Watson-Jones approach has limited efficacy in treating femoral neck fractures, but the use of a single incision for fracture reduction and implant placement is attractive to surgeons.
The Approach And The Blood Supply
One question is whether this treatment will damage the blood supply to the femoral head. Stephen C. Stacey et al.  argue that surgeons should identify and protect the ascending branch of the lateral femoral circumflex artery (LFCA) because it is very important to the blood supply of the femoral head. However, Ganz's well-accepted study shows that the deep branches of the medial femoral circumflex artery (MFCA) mainly supply blood to the femoral head. Based on this theory, the LFCA and its branch should be located in the middle of the DAA, and ligation of these vessels will not jeopardize the blood supply to the femoral head. Therefore, we agree that the vessel damaged in the DAA approach is the LFCA, which has been shown to have only a weak relationship with the femoral head blood supply. However, it should be noted that a "T" capsule incision is performed through the anterior capsule, and the capsule incision along the acetabulum edge should be sufficiently distant from the posterior edge to avoid damaging the entry point of the MFCA.
Similarly, the repeated implantation of K-wires into the posterior superior area of the femoral neck also leads to a risk of damage to the blood supply of the femoral head because of the proximity of the wires to the MFCA.
Cannulated screw fixation is a widely accepted technique for femoral neck fracture fixation because it is simple and minimally invasive.
The divergent type or parallel type is better than the convergent type regarding the resulting biomechanics. Three cannulated screws are arranged in an inverted triangle, which can also reduce the risk of fracture under the trochanter after fixation. Previous biomechanical studies have shown that in cases of comminuted posterior femoral neck fractures, additionally using a fourth screw can improve the fixation strength.
Similarly, in fractures with high-risk patterns (i.e., Pauwels type III), utilizing a trochanteric lag screw has been shown to be biomechanically superior than using an inverted triangle pattern. Zhuang L et al.  reported that the use of an anteromedial femoral neck plate and two cannulated compression screws is associated with a low incidence of complications, including nonunion and avascular necrosis. Pauwels type III femoral neck fractures are subjected to increased varus displacement moments, leading to nonunion rates ranging from 16–59% and AVN rates ranging from 11–86%. In a study by Ye Ye et al. , fixation with buttress plate augmentation of three cannulated screws resulted in an 89% union rate in a series of Pauwels type III femoral neck fractures, which was higher than those in previous studies using cannulated screws alone.
Our study found that although DAA can provide good exposure, the incidence of nonunion, implant failure and AVN is relatively higher than that of other studies[6, 7]. Therefore, using only three cannulated screws may not be the best method to fix femoral neck fractures in young adults.