Clinical observation and finite element analysis of cannulated screw internal fixation in the treatment of femoral neck fracture based on different reduction quality

Abstract

Objective Femoral neck fracture is one of the most common bone types. The effect of reduction quality on hip joint function and complications after screw internal fixation is not fully understood. To investigate the clinical efficacy and mechanical mechanism of positive buttress, anatomical reduction, and negative buttress in the treatment of femoral neck fracture after cannulated screw fixation. Methods Retrospective analysis of patients with femoral neck fracture treated with three cannulated screws internal fixation in our hospital from January 2013 to December 2018. According to the quality of fracture reduction, the patients were divided into positive buttress group, anatomical reduction group, and negative buttress group. Basic information such as injury mechanism, time from injury to surgery, Garden classification and Pauwels classification was collected, Harris scores were performed at 3 months, 6 months, and 12 months after surgery, and postoperative complications (femoral head necrosis, femoral neck shortening, and femoral neck nonunion) were collected. At the same time, three groups of finite element models with different reduction quality were established for stress analysis, their stress clouds were observed and the average displacement and stress of the three groups of models were compared. P < 0.05 was used to represent a statistically significant difference. Results A total of 225 cases of unilateral femoral neck fractures were included and followed up for an average of 4.12 ± 0.69 years. There was no significant difference in age, gender, side, injury mechanism, time from injury to surgery, BMI, Garden classification, Pauwels classification, and follow-up time among the three groups (P > 0.05). However, there was significant difference in Harris score at 6 and 12 months after operation among the three groups (P < 0.05), which was higher in the positive buttress group and anatomical reduction group than in the negative buttress group. In addition, the incidence of osteonecrosis of the femoral head in the negative buttress group (32.2%) was greater than that in the anatomical reduction group (13.4%) and the positive buttress group (5.4%) (P < 0.05). In addition, the incidence of femoral neck nonunion and femoral neck shortening in the negative buttress group was also higher than that in the anatomical reduction positive buttress group (P < 0.05). The finite element results showed that the stress and fracture end displacement in the negative buttress group were greater than those in the positive buttress group (P < 0.05). Conclusion Both positive buttress and anatomical reduction in the treatment of femoral neck fracture with cannulated screw internal fixation can obtain better clinical effect and lower postoperative complications. Positive brace support and anatomic reduction can limit the restoration of femoral stress conduction. Therefore, it is not necessary to pursue anatomical reduction too deliberately during surgery, while negative buttress reduction should be avoided.

Biomechanical effects of internal fixation with self-lock compression anti-rotation blade for Pauwels type III femoral neck fractures: a comparative finite element analysis

“…The traditional fixation of 3CS in an inverted triangle configuration has always been controversial in the treatment of unstable FNFs due to poor mechanical stability [35]. Previous studies have shown a high incidence of hip varus deformity and femoral neck shortening after 3CS fixation [23,36,37], increasing the risk of internal fixation failure and revision via arthroplasty [38]. The results of our study support previous findings.…”

“…Firstly, the finite element analysis assumes that the object of study is a homogeneous material and sets material properties using uniform modulus of elasticity and Poisson's ratio, which can be somewhat different from the actual condition. In addition, the prognosis of femoral neck fractures treated by internal fixation is closely related to the quality of reduction [23], but our study simulated a fully anatomically repositioned Pauwels type III FNF, which is not always the case in clinical practice. As mentioned above, there are various configurations of 3CS and only traditional inverted triangle configuration included in this study.…”

“…According to the literature [23], three cannulated screws parallel to each other were arranged in an inverted triangle configuration and placed in the femoral neck. The angles of the screws with the longitude axis of the femur were 135°, and the screw tip was 5 mm below the bone cortex of femoral head.…”

Clinical Outcome and Biomechanical Analysis of Dynamic Hip Screw Combined with Derotation Screw in Treating Displaced Femoral Neck Fractures Based on Different Reduction Qualities in Young Patients (≤65 Years of Age)

“…Multiple attempts of closed reduction or open reduction with the aim of anatomical reduction can damage the blood supply of the femoral head and increase the incidence of fracture nonunion or necrosis of the femoral head [ 12 ]. Recently, nonanatomical reductions of FNF, which include positive buttress reduction and negative buttress reduction, have attracted wide attention [ 13 – 15 ]. The definition of the former is that the distal fracture segments is positioned medially to the lower-medial edge of the proximal segment, while the latter is that the proximal fracture segment is positioned medially to the upper medial edge of the distal segment [ 16 ].…”

“…The definition of the former is that the distal fracture segments is positioned medially to the lower-medial edge of the proximal segment, while the latter is that the proximal fracture segment is positioned medially to the upper medial edge of the distal segment [ 16 ]. Since Gotfried et al first proposed the concept of nonanatomical reduction in 2013, numerous studies have compared the effect of nonanatomical reduction and anatomical reduction in FNF [ 10 , 13 – 15 ]. However, all of these studies focused on internal fixation with CCS.…”