The Importance of the Lateral Femoral Wall Thickness in Intertrochanteric Fracture: Educational Corner

An intertrochanteric (IT) fracture is the most common reason for an elderly person to be admitted to an acute orthopedic ward. It continues to cause significant decision-making challenges among orthopedic surgeons. The stability of IT fractures is usually investigated based on the medial and posteromedial fragments (1). The lateral wall integrity has been proved to be an essential determinant of fracture stability in IT fractures. Recently, there was a view that lateral femoral wall thickness has a significant role in IT fractures, including providing rotational stability, preventing excessive collapse, preventing excess medialization of the shaft, decreasing the reoperation rate, and providing a better functional outcome (2). In general, it can prevent the collapse of the proximal fragment like a lateral buttress. The lateral wall thickness concept was recently utilized by the AO Foundation/Orthopaedic Trauma Association (AO/OTA) classification of fractures (3). They differentiated stable and unstable IT fractures based on the thickness of the lateral wall. There are few studies which investigated the importance of the lateral wall in IT fractures and their benchmark thickness in the evaluation of fracture stability. In this educational note, we review studies that worked on this concept and the importance of the lateral wall thickness in IT fractures. The Importance of Lateral Wall Thickness The most crucial factor in successful outcomes in dynamic hip screw (DHS) fixation was formerly thought to be the integrity of the posteromedial femoral section. Lately, it was shifted to the lateral wall. According to the biomechanical data, there is an increased chance of preserving the structure against negative forces with a higher cortical bone thickness (4-7). An unstable IT fracture happens when the integrity of the lateral wall is violated, as in OTA types A2.2 and A2.3. In other words, when the lateral wall has fracture, a simple IT fracture (OTA 31-A1/A2) will change into a reverse oblique fracture (OTA 31-A3). Therefore, it is a critical factor for decision-making and the successful treatment of unstable IT fractures. Stable IT fractures have a lower incidence of lateral wall fracture when fixing by DHS. These patients often have intact calcar or non-displaced lesser trochanteric fracture (1). Lateral wall thickness is considered as a predictor of lateral wall fracture after a DHS implantation. Based on the study by Hsu et al., a thickness of < 20.5 mm is a risk factor for the prediction of secondary lateral wall fracture (sensitivity of 82.7%, specificity of 77.8%) and should not be fixed with DHS alone (8). Thus, for a better outcome, it is essential to know the fracture characteristics to predict its behavior after fixation. Lateral wall measurement method Hsu et al. analyzed 225 patients with IT fracture and 25 patients who had failed IT fixation by receiver operating characteristic (ROC) curve to estimate a threshold value that could predict lateral wall fracture (8). They defined the lateral wall thickness on anteroposterior (AP) radiograph as the distance between a reference point (3 cm below the vastus ridge of the greater trochanter) to the proximal of the fracture line with a 135° angle (Figure 1).