In the process of standing and walking, the human hip joint bears 2.3–2.8 times the weight of gravity [22]. The trabecular bone at the proximal femur is distributed regularly and orderly. Pressure trabecular bone and tension trabecula gradually formed, which are similar to a lever system. The medial wall, acting as a fulcrum, bears compressive stress [18]. In the management of intertrochanteric fractures, substantial literatures showed that effective medial buttress would make a valuable contribution towards reducing postoperative complication, for instance, implant failure and coxa vara [16]. According to the degree of stability, we divided the medial column into intact wall (M0), simple fracture (M1) and multi-fragmentary fracture (M2). For M1 fracture pattern, reduction with positive or neutral medial cortical support and fixation with cephalomedullary nails is acceptable. Limited sliding between head-neck fragment and femur shaft could benefit secondary stability. This process might be favorable to fracture healing [23]. M2 fracture pattern, regarded as unstable fracture, always appears to be fairly hard to achieve an ideal anatomic reduction to get rigid buttress. Delayed ambulation will be performed postoperatively, which may be associated with a higher incidence of postoperative complications. For augmentative stability of medial column, some new fixation systems, for instance, triangular support intramedullary nail (Double Medical Technology Inc, China) and medial sustainable nail (Weigao Medical Technology Inc, China) have been utilized [12, 16]. In our classification system, M2 is approximately relative to medial multi-fragmentary fracture pattern (31A3.3) by AO classification-2018. Subdivided classification of medial column may optimize fixation choice (Table 2).
On the contrary, lateral wall of proximal femur bears tensile stress. We defined lateral column as region of tension bone trabecular. With an increasing attention to the integrity and thickness of lateral wall, various complementary methods of reconstruction and fixation were described, while using extramedullary or intramedullary implants [24, 25]. Yet there is no consensus on implant choice corresponding to classification systems. Based on the positional relation between fracture line and femur neck fundus, we divided the lateral column into L0, L1, L2 and L3, with increasing instability. L1 fractures were considered as stable fracture and needed no extra fixation. L2 fractures were defined as transverse fractures or oblique fractures traditionally. The breakage of tensile structure may lead to overload on implants. High implant failure rate were reported frequently [24]. Long cephalomedullary nails were recommended with or without additional augmentation, for instance, cerclage, screw and plate. L3 fractures occur below femoral neck fundus in our classification. In order to improve working length of nails, long cephalomedullary nails and additional lateral column reconstruction might be contributory to balance the strong moment from hip [26]. Based on subtypes of lateral column, we can determine implant choice, fixation length, optimal augmentative device.
In our observation, the fracture line involving trochanter runs generally from the anterosuperior edge of the GT toward the LT. On the other hand, GT and LT fragments are frequently poor-reduced and fixed while using extramedullary or intramedullary implants [27]. This situation is mainly due to the attachment of gluteus medius, piriformis and iliopsoas muscle, which may produce specific fracture mechanism [19]. Thus, we defined the region involving superoposterior GT and LT as posterior column. GT fracture (P1) and LT fracture (P2) may occur isolately or simultaneously (P3). The management of fractures in posterior column remains ambiguous. In recent literatures, it was reported that poor reduction and fixation of LT fragment may be significantly associated with posterior sagging after operation [28]. Fixation with non-absorbable tape (Alfresa Pharma Co., Ltd., Japan), or twisted steel wires (Alfresa Pharma Co., Ltd., Japan) could be an effective procedure to improve early ambulatory ability [13, 27, 29]. Optimal management of posterior column fractures may need further research.
Based on 3DCT reconstruction of intertrochanteric fractures, medial, lateral and posterior column could be assessed respectively. The detailed fracture pattern in each column may attribute to making fixation strategy. Overall evaluation can be documented as M0/1/2L0/1/2/3P0/1/2/3. Therefore, treatment protocol involving implant type, working length, auxiliary device and rehabilitation plan are determined. In this study, 103 patients (39.9%) were classified as M1L0/1P2/3, representing the majority of intertrochanteric fractures. For these patterns, short cephalomedullary nails are proposed, with or without fixation of LT. Another fracture type, M2L3P3 in our classification system, indicating severe comminution of intertrochanteric fractures, may need long cephalomedullary nails and three column augmentation [8, 26, 30].
Our study has several limitations. The main limitation of the study is that the sample size was small. Thus, only few cases were classified into several less frequent fracture types (e.g. M0L1P0/1/2, M1L2P0/1). This may decrease clinical application value and promotion value. A further limitation is that the recommendation for fracture treatment were based on partial data in previous literatures. Conclusive surgical protocols require further study and systematic review. In addition, in these fracture images from 258 consecutive patients, we found that young adults tend to have more transverse fractures or oblique fractures from high-energy mechanisms. Thus, the difference between young and elder patients regarding bony condition, traumatic mechanism, fracture pattern and treatment strategy should be taken into consideration. In conclusion, we proposed this novel classification system for intertrochanteric fractures based on 3DCT findings with good agreement. It is comprehensive, reproducible and easy to grasp relative to other classification system. This method is based on proximal femur biomechanical characteristics and traumatic mechanism. We could formulate more reasonable treatment protocols involving various late-model internal fixation systems.