The treatment of unattached femoral neck fractures has always been a great challenge for trauma orthopedic surgeons. Although femoral neck fractures mostly occur in elderly patients with osteoporosis in low-energy injuries, and hip replacement can achieve good clinical results, when they occur in young patients with normal bone quality, the cause of injury is mostly high-energy injuries (e.g. motor vehicle accidents, etc.) and prone to fracture comminution, often with significant displacement, and insufficient post-injury repositioning/fixation of the fracture can easily lead to fracture nonunion. Although internal fixation techniques and materials have developed considerably in recent years, the incidence of displaced fracture nonunion is still as high as 10%-30% (more than 6 times higher than that of nondisplaced fractures). Once a fracture of the femoral neck is disconnected, it can be very difficult to treat and can lead to a series of serious complications, which can be a “nightmare” for both physicians and patients. The former includes inter-rotor abduction osteotomy and hollow nailing or inverted minimally invasive internal fixation system (LISS) combined with an anastomotic free fibula graft, while the latter is hip replacement. Inter-rotator abduction osteotomies include the McMurry osteotomy and the Schanz osteotomy, first introduced by Pauwels in 1927. Since then, it has been reported as an effective treatment to cure some hip diseases and is particularly effective in avoiding or delaying hip replacement in young hip patients. The principle of inter-rotor abduction osteotomy is to increase the neck stem angle by inter-rotor osteotomy, which changes the shear force to pressure at the unconnected part of the femoral neck fracture; at the same time, the force arm of the gluteus medius muscle grows and the contraction force increases, which produces pressure on the unconnected part of the fracture. This procedure is in accordance with the principles of mechanics, is relatively simple in surgical technique, allows lengthening of the shortened limb by approximately 50 px, and also has a relatively high success rate, and is still the standard procedure for the treatment of unconnected femoral neck fractures in many countries, including North America. However, its disadvantages are also obvious, mainly in the following 4 aspects. First, inter-rotor abduction osteotomy may lead to premature degeneration or ischemic necrosis of the normal femoral head for three reasons: (1) abduction osteotomy leads to a shorter force arm between the femoral head and the greater trochanter, and the abductor muscle must increase traction to balance the body’s downward gravity during walking, when the weight-bearing area of the hip joint becomes the fulcrum of the lever, resulting in a significant increase in pressure on the femoral head; (2) abduction osteotomy leads to an increase in the distance between the acetabulum and the greater trochanter, resulting in a significant increase in the distance between the abductor muscle and the femoral head. (2) the distance between the acetabulum and the greater trochanter is increased due to the abduction osteotomy, resulting in tension of the abductor muscle and hip capsule, which further aggravates the ischemia of the already poor blood flow to the joint capsule/femoral head. Secondly, the inter-rotor abduction osteotomy will bring difficulties to the later hip replacement: the abduction osteotomy causes the anatomical structure of the proximal femur to change, which brings technical difficulties to some of the patients who failed the surgery to have their hip replaced later, especially the difficulties to deal with the lateral femoral expansion of the marrow and the placement of the prosthesis. Third, inter-rotor abduction osteotomy can lead to lateral osteoarthritis of the knee joint: the abduction osteotomy causes the distal femur to be internalized, thus reducing the lateral joint space of the knee joint, which will lead to osteoarthritis in the long run. Fourth, gait change (claudication): The main reason for this is also due to the change of the gluteus medius force arm after the abduction osteotomy. Despite the above disadvantages, it is a better treatment for young patients with non-necrotic femoral head to preserve their own hip joint, even if there is shortening and resorption of the femoral neck. Although inter-rotor abduction osteotomy perfectly solves the mechanical problem of femoral neck fracture disjunction, it is a parafocal osteotomy, which does not solve the biological problem of the “focal point” (bone disjunction), and more importantly, femoral neck fracture disjunction is not only a mechanical problem, but a complex mechanical and biological problem. Therefore, neither mechanical (internal fixation) nor biological (bone grafting) methods are sufficient to solve the problem, and a combination of both must be used. The hollow nail or inverted LISS combined with anastomotic vascular free fibula graft is an effective method to solve this complex mechanical and biological problem, and it also overcomes the four major disadvantages of inter-rotor abduction osteotomy. In 2010, we reported a modified version of this procedure for the treatment of femoral neck osteonecrosis, and after more than 2 years of follow-up, the healing rate of osteonecrosis reached 92.3% and the rate of femoral head necrosis was 3.8%, which shows that this procedure has good clinical efficacy in the treatment of femoral neck fracture nonunion in young adults. The main advantages include: first, the hollow nail or LISS can provide a reliable fixation for the nonunion, and three hollow nails can be used for the first revision patients, and inverted LISS is also a reliable fixation for patients with multiple surgical history or poor position of the first nail; in addition, the grafted fibula provides a reliable anti-rotation effect for the nonunion. Secondly, anastomotic free fibula graft can restore the femoral neck length to the maximum extent, but most of them need to be combined with iliac bone/artificial bone graft, because after the fracture disjunction is repositioned and the femoral neck length is restored as much as possible, there is mostly a large bone defect at the fracture disjunction; in addition, the vascularized fibula graft can improve the local blood circulation at the fracture disjunction. Thirdly, it can prevent femoral head necrosis. The anastomotic vascularized free fibula graft itself is a recommended procedure for the treatment of femoral head necrosis, and the anterolateral incision within the joint capsule reduces the intra-articular capsule pressure, while the vascularized fibula inserted into the femoral head provides a good blood supply to the femoral head while reducing the intra-femoral head pressure. Despite these advantages, Urbaniak believes that our modified approach has disadvantages compared with his method, such as the disruption of blood flow to the femoral head by the capsule dissection and the resulting joint adhesions, and the removal of some important cortical bone by the anterior grooving of the femoral neck, which did not occur in our clinical practice. On the contrary, we believe that the modified approach has more advantages: the debridement and repositioning of the disjointed bone can be performed under direct vision, which is more thorough and precise; the anterior hip incision can be made under direct vision to anastomose the vessels and avoid compression of the vascular anastomosis; and the anterior femoral neck notch avoids the influence of soft tissue on bone healing. The disadvantages of this procedure are mainly the high technical requirements and the complexity of the surgical approach. Therefore, hollow nail or inverted LISS combined with anastomotic vascular free fibula graft is currently the most effective method to solve the complex mechanical a biological problem of unconnected femoral neck fracture, especially for young adult patients with unconnected femoral neck fracture, this procedure can effectively avoid or delay hip replacement. In addition to the method of preserving the own hip joint, a method that does not preserve the own hip joint is hip arthroplasty. Although hip replacement has achieved fairly good clinical results in older patients, it is not recommended for adolescent patients with unattached femoral neck fractures, even with surface replacement. For patients over 55 years of age with unattached femoral neck fractures and patients with severe femoral neck shortening who cannot tolerate prolonged weight bearing, total hip replacement is generally recommended; however, for patients under 60 years of age and over 55 years of age with unattached femoral neck fractures, if there is a desire to preserve their own hip joint and no manifestation of osteoarthritis of the hip joint, hollow nailing or inverted LISS combined with anastomotic vascular free fibula graft can be attempted treatment. Overall, hip replacement can achieve good results and is an ideal treatment in older patients with unconnected femoral neck fractures. In conclusion, hollow nailing or inverted LISS combined with anastomotic vascularized free fibula graft can be used to treat adolescent patients with unattached femoral neck fractures in order to preserve the patient’s own, painless, functional hip joint as much as possible; while in older patients, hip replacement is the surgical approach to obtain good clinical results.