For the stable reconstructions after fracture reduction and fixation, 5 influencing factors have been summarized, i.e. bone quality (osteoporosis), fragment geometry (comminution), fracture reduction quality, implant selection, and implant placement (TAD/Cal-TAD) [6]. Fracture reduction quality is the first pre-requisite for the treatment of the pertrochanteric fracture [7]. Insufficient fracture reduction can result into the incorrect position of the lag screw/helical blade and even the failure of the mechanical stability of the internal fixation system which may impair the patients’ functional outcomes [8].
Previously, a lot of fracture reduction quality criteria have been described in the literature. These criteria include two aspects which are Garden alignment and fragment displacement. The alignment is similar, and the Garden index is used. However, the displacement criteria are different among different authors. For example, greater than 5 mm by Sernbo [9](1988), 4 mm by Baumgaetner [10] (1995), and 20% by Fogagnolo [11] (2004). Fracture reduction quality is categorized as good (presence of both alignment and displacement criteria), acceptable (either one criterion) or poor (absence of both criteria). In practice, as the detached lesser trochanteric fragment in unstable fracture patterns is usually not reduced and secured clinically by most implants [12], it is hard to achieve “good” reduction quality. Most patients can only meet an “acceptable” quality according to Baumgaertner’s criteria.
In 2015, Chang et al. [5] put forward the new reduction quality criteria: (1) alignment (Garden index): normal or slight abduction of the neck-shaft angle in the AP view, and less than 20 °in the lateral view; (2) apposition: the medial cortices positive or neutral to each other in the AP view; and the anterior cortices smooth or neutral in contact to each other in the lateral view. The reduction quality could also be divided into three grades: good, acceptable and poor. In 2019, Mao et al. [13] explored the reliability of predicting mechanical complications by using Baumgaertner’s criteria and Chang’s criteria. The authors believed that the Chang’s criteria which emphasized anteromedial cortical contact was more reliable and effective than the Baumgaertner’s criteria in predicting postoperative mechanical complications and worthy of clinical applications. Biomechanical [14] and clinical [15] researches have confirmed that the anteromedial cortical contact can not only share stress load from the internal fixation device (mechanical role), but also can promote close contact and fracture healing at the fracture sites (biological role), both of which are benefit for maintaining the normal femoral neck length and the neck-shaft angle.
The anteromedial cortical contact is the key element in evaluation of fracture reduction quality. In 2018, Chang et al. [16] conducted a study on the medial and anterior cortical reduction quality by intraoperative AP and lateral fluoroscopic images and compared it with the post-operative 3D-CT reconstruction images to judge the accuracy of intraoperative fluoroscopic alignment of anteromedial cortex indirectly. The results showed that a positive AP position combined with a positive/neutral lateral position had a high predictive value of the cortical support as confirmed by 3D CT reconstruction images (15/17, 88.2%). While the negative lateral position observed on intra-operative fluoroscopy, regardless of the AP position, was predictive of the final loss of cortical support as demonstrated by 3D-CT reconstruction images (6/7, 85.7%).
Intraoperative flouroscopy allows the surgeon to do a live rotation arc across the fracture to verify reduction. It is ideal to see the AP, lateral and all the obliques to verify fracture reduction is maintained. However, full range view of 360 degrees is impossible in daily practice, and has a greater amount of radiation exposure.
It is apparent that the detection of an anteromedial tangential view without obstruction of other structures may probably enhance the accuracy in interpretation of the relationship between cortices of the head-neck and the shaft fragments. In this study, five anatomical landmarks on the proximal femur were marked with steel wires: the Greater trochanter, the Lesser trochanter, the Intertrochanteric line, the Anterolateral tubercle and the Anteromedial cortical tangent line. After obtaining the standard lateral view of the femoral neck by intra-operative fluoroscopy, we gradually rotated the machine internally to eliminate the overlapping structures on the anterior aspect. We found out that with 30°of rotation, a clear tangential projection of the anteromedial cortex can be obtained.
Clinically, the anteromedial oblique fluoroscopic view of 30° was used to evaluate the alignment of the antero-medial-inferior corner cortex. Compared with AP and lateral views, the oblique fluoroscopic view had a higher accuracy in evaluation of anteromedial apposition. The final loss of cortical contact in 3D-CT was seen in almost all in the negative groups (24/25,96%). This suggested that the negative reduction of the anteromedial cortices needs further re-correction during the operation. Postoperative 3D-CT images revealed that approximately 20%(10/51) of cases in neutral group (observed via oblique fluoroscopic view) did not attain the anteromedial cortical support in the final. In reality, the neutral group shown on intra-operative fluoroscopy may actually have three sub-patterns: 1) an exact anatomic position, 2) a slightly positive position and 3) a slightly negative position. However, as the intra-operative fluoroscopic image resolution is limited, 2-mm cortical steps may not be able to be distinguished clearly. Thus, it becomes unfavorable for a slightly negatively positioned pattern. As the head-neck fragment gets influenced by postoperative muscle contraction and weight-bearing, a slight negative position might become a true negative in postoperative period and finally leading to the loss of the cortical contact.
Several factors may affect the rotation of the head-neck fragment: (1) it is difficult to accurately reduce the anterior and medial cortices in closed reduction, which means exact anatomic reduction of the anteromedial cortices is rare. (2) the intra-operative fluoroscopic image resolution is limited with two dimensional image, which is difficult to observe the rotation of the head-neck fragment. (3) high speed driving of guide pin or reamer, wrenching in the lag screw, or hammering in the helical blade may cause rotation of the head-neck fragment. (4) post-operative axial telescoping may be interfered by head-neck rotation and tilting [17]. Our experience showed that a slightly flexed rotation of the head-neck fragment (less than 15 degrees) is preferable for anterolateral cortical support (46/62, 74.2%).
There are some limitations in this study: (1) this is a retrospective case series study. (2) The anteromedial cortical alignment was evaluated after the cephalomedullary nail insertion. At this point, further corrections of the fracture reduction were impossible. (3) this is only a radiographic comparison study and no clinical outcomes during follow-up periods were described.
