Owing to the anatomical structure and biomechanical characteristics of the femoral neck, complications such as fracture nonunion and femoral head necrosis are prone to occur after fracture and result in significant morbidity and mortality . For young adults and select active older individuals, the treatment of choice can be closed reduction and internal fixation with hollow screw, which has the advantages of minimal tissue invasion, less blood loss, shorter operation time and quicker return to daily activities [4, 9]. Previous researches have suggested that three hollow screws inserted in an inverted triangular configuration into the femoral neck can provide an adequate mechanical stability to resist the increased shear forces generated [5, 10]. The quality of fracture reduction and internal fixation is considered to be the most important prognostic factor, which has an obvious correlation with the incidence of complication such as fracture nonunion and avascular femoral head necrosis .
In a routine surgery of femoral neck fracture with internal fixation, the first step is to insert the lowest guide pin and hollow screw, which requires a highly accuracy because the remaining two guide pin and hollow screws are inserted taking the first screw as reference. Because of the thick muscle in hip, there is no obvious landmark to help a surgeon locating the insertion point of the first screw. Previously, the insertion of first screw referred to a Kirschner wire placed on the skin in front of the hip joint, and an interoperative fluoroscopy was used to adjust the direction of Kirschner wire until it consists with the preoperative plan . In clinical practice, due to the different soft tissue thickness, the above procedure always requires repeated fluoroscopic confirmations and guide pin adjustments, which is time-consuming. In addition, due to the instability of the fracture and continuous intraoperative traction, although a good reduction of the fracture was previously achieved, a fracture displacement and rotation may occur , resulting in another closed reduction procedure, even an open reduction, which is frustrated during the surgery.
Although navigation-assisted techniques and surgical robots may perfectly solve the problem [13, 14], because of the high equipment and technique requirements, they are difficult to be utilized in an ordinary medical institution. Therefore, it is necessary to develop a convenient and accurate approach to help a surgeon locate the first guide pin’s insertion. Previous studies of biomechanics of the femoral neck fracture with internal fixation have suggested that, to achieve an optimal support and fixation, the first screw should be located at the lower margin of the lesser trochanter of the femur, passing through the Ward’s triangle and clinging to the femoral calcar, finally entry the femoral head (Fig. 1) [15, 16]. According to the anatomy of gluteus maximus muscle , the lower edge of the lesser trochanter of the femur is generally close to the upper edge of attachment point of gluteus maximus (bony landmarks: the superior edge of gluteal tuberosity), moreover, the authors found in clinical practice that the above two structures locate at the same level (Fig. 2). Therefore, using the attachment point of gluteus maximus as a reference to insert guide pin is theoretically feasible.
In order to verify this theoretical approach in clinical practice, we performed the femoral neck fracture with closed reduction and internal fixation surgery in both traditional approach and this new approach. To control the bias between operators, 4 different surgeons were asked to perform surgery using the above two approaches according to the grouping of patients, and the operation time, the number of adjustments for the first guide pin, the frequency of intraoperative perspective were recorded to make a comparison. The results showed that for all 4 surgeons, using the attachment point of gluteus maximus as a reference to insert guide pin can significantly shorten the operation time, reduce the numbers of guide pin adjustments and the frequency of intraoperative perspective, moreover, no difference was found in prognosis the patients between the two group. In a word, the new approach is not only theoretically feasible but also clinically efficient.
The simplified insertion procedure is as follows: making a 2cm longitudinal incision in the proximal lateral thigh, starting from about 5 cm below the tip of the greater trochanter of the femur. After separating the deep fascia and splitting the vastus lateralis from posterior margin, the attachment point of gluteus maximus will be accessible. The middle point of the anterior and posterior edges of the femoral shaft is the insertion point. The first guide pin is inserted in the direction of the femoral head with an anteversion angle of about 15°. Compared to the traditional approach, the above new approach requires a longitudinal straight incision of femur, the necessity lies in: (a) it is beneficial to exposure and operation. The muscles and soft tissues in the hip are thick, and the anterior and posterior edges of the femur cannot be located without an incision, nor to insert a guide pin or hollow screw; (b) the incision is made in order to avoid the muscles and soft tissues attachment or wrapping around the guide pin during the insertion process, which will contribute to protect the tissue in surgical area; (c) when the fracture union, the incision can be utilized for the removal of internal fixation.
The finding of this study showed that compared with the control group in which Kirschner wire was placed on the body as a reference to insert guide pins and hollow screws, the observation group could significantly shorten the operation time, reduce the numbers of guide pin adjustments and the frequency of intraoperative perspective, in turn reduce the risk of fracture displacement caused by repeated operation. In conclusion, this study described an accurate inserting location for closed reduction and internal fixation of femoral neck fracture, which will contribute to improve the operation quality and reduce the risk of complications, and has comparatively higher practical value.