This study defines a basicervical intertrochanteric fracture as when more than 50% of the fracture line is located proximal to the intertrochanteric crest where the anterior capsule of the hip joint is attached. This study evaluated the incidence and characteristics to determine the factors associated with surgical failures. A total of 58 of 226 patients (25.7%) with intertrochanteric fracture enrolled in this study showed basicervical intertrochanteric fracture. Among eleven surgical failures, six (10.3%) were identified in the basicervical intertrochanteric fracture group, and the basicervical type was a significant predictor for surgical failure in all patients with intertrochanteric fractures. Postoperative unacceptable reduction was the only significant predictor for surgical failure in 58 basicervical intertrochanteric fractures and no significant association between an intact anterior capsule and surgical failure was identified. However, five out of six surgical failures, excluding one case of osteonecrosis of the femoral head, showed unacceptable reduction and an intact anterior capsule including two incarcerated capsules. When we excluded 11 patients with non-displaced fractures (A11) out of the 58 patients with basicervical intertrochanteric fractures, an intact anterior capsule was statistically correlated with surgical failure and posterior reduction.
This study showed that a basicervical fracture type is one of the significant risk factors for surgical failure of an intertrochanteric fracture. Previous studies have suggested the high susceptibility of basicervical intertrochanteric fractures to surgical failure. Su et al.  suggested that basicervical fractures may have increased biomechanical instability and a higher tendency to collapse compared with other types of intertrochanteric fractures. Bojan et al.  reported 9% of screw cutout rate in patients with basicervical fracture compared with 1% of screw cutout rate overall in a large series of more than 3,000 fractures in the trochanteric regions. Watson et al.  suggested the inherent instability of basicervical proximal femoral fractures makes treatment more difficult based on the surgical result when treated with a cephalomedullary fixation. Kwak et al.  mentioned that the inherent instability of basicervical proximal femoral fractures was associated with the anatomical vulnerability of this fracture, including the narrow cortical base of the proximal fragment and the subsequent narrow contact area at the main fracture site, along with insufficient cancellous interdigitation compared with other types of intertrochanteric fractures. Furthermore, the short proximal fragment of this fracture can cause rotational instability during bone healing regardless of fixation devices. For these reasons, achieving anteromedial cortical buttressing around the fracture site of the basicervical intertrochanteric fracture postoperatively may be a vital aspect of surgery. Anteromedial cortical buttressing has been previously emphasized in unstable intertrochanteric fractures [2, 20]. However, to the best of our knowledge, the importance of anterior medial cortical buttressing in basicervical intertrochanteric fracture has not yet been elucidated. We believe that the biomechanical understanding of the proximal femur from previous studies and the surgical results of our study might offer enough theoretical evidence to support the importance of anteromedial cortical buttressing in these fractures.
We focused on the fact that 4 out of 6 surgical failures in the basicervical intertrochanteric fracture group were associated with displaced two-part fracture corresponding to A12 fracture based on the AO classification. The incidence of unacceptable reduction in this group was 32.8% (19 out of 58) despite efforts to achieve acceptable reduction under fluoroscopic guidance. In particular, among 35 A12 fractures, 13 patients (37.1%) showed unacceptable reduction, which was a higher incidence than that shown in all patients with intertrochanteric fractures enrolled in this study (22.6%). This result indicates that achieving an acceptable reduction in an A12 type of basicervical intertrochanteric fracture can be more difficult than in other types of intertrochanteric fractures.
High incidences of postoperative unacceptable reduction in A12 fractures may be attributed to the radiologic misunderstanding of fluoroscopic trans-axial images during surgery. When there is distraction of fracture site, even though intraoperative reduction seems anatomical, it can become an unacceptable reduction during follow-up. This is because the sliding of the proximal fragment occurs from the anterior to the posterior, along the direction of the helical blade. In this study, four out of five patients with non-union in the basicervical intertrochanteric group showed unacceptable reduction in the follow-up radiographs, even though they showed anatomical reduction on intraoperative fluoroscopy and postoperative radiographs. Due to the distraction of the fracture site regarding excessive traction or intentional valgus reduction during the surgery, the intraoperative fluoroscopic images and postoperative radiographs may be misconstrued as anatomical reduction. The fracture gap can lead to the failure of anteromedial cortical buttressing and intramedullary reduction during follow-up, because the sliding direction of the proximal fragment is consistent with the direction of the helical blade. Thus, slight over-reduction should be considered for the surgical treatment of basicervical intertrochanteric fracture when the distraction of fracture site is expected.
We attempted to prove our hypothesis that the anterior capsule of the hip joint is a potential inherent vulnerability that may make it difficult to achieve acceptable reduction. The anterior capsule of a basicervical intertrochanteric fracture can be intactly attached distally to the fracture site because this fracture shows the characteristics of a partially or totally intra-capsular fracture. If the fracture occurred without detachment of the anterior capsule from its distal insertion, it may be a considerable hindrance to the accurate reduction or proper sliding of the proximal fragment. We identified five cases with an intact anterior capsule out of six surgical failures in the basicervical intertrochanteric fracture group. When we excluded one case with osteonecrosis of the femoral head, all patients with non-union had an intact anterior capsule, and two cases showed incarceration of the anterior capsule in the fracture site. Based on these results, we believe that the anterior capsule of the hip joint can be a major hindrance that negatively affects fracture reduction during surgery.
The present study has several limitations. First, this is a retrospective study with relatively few enrolled cases of surgical failures, which might have affected the reliability of the logistic regression analysis. Second, despite high inter-observer reliability achieved, radiologic evaluation for the anterior capsule using 3D CT has not been previously validated. Furthermore, although the anterior capsule of the hip joint and surgical failure of the basicervical intertrochanteric fracture may be correlated, studies offering clinical evidence on the biomechanical effect of the anterior capsule on the surgical outcome are needed. Third, although we defined basicervical intertrochanteric fractures using a modified concept, this definition might be ambiguous. In addition, although the inter-class correlation coefficient of this fracture was 0.856 in this study, which can be interpreted as almost perfect agreement, identifying the insertion site of the anterior capsule and setting the boundary between the femoral neck and the basicervical intertrochanteric fracture can be subjective. Finally, this study did not suggest a surgical solution to overcome the inherent vulnerability of basicervical intertrochanteric fractures. Based on the results of the present study, anterior capsulectomy might contribute to achieving proper anteromedial cortical buttressing. However, additional studies are need to determine if this surgical technique can improve surgical outcomes or if it may take a toll on the soft tissue around the hip joint with additional blood loss.