The protective effect of medial wall integrity on ventral blade insertion in PFNA: Clinical and biomechanical evidence.

BackgroundThe impact of screw trajectory on the stability of internal fixation devices has been widely investigated. Previous studies indicate that ventrally directed blade insertion may compromise fixation stability and exacerbate femoral head varus in proximal femoral nail anti-rotation (PFNA) models of unstable intertrochanteric fractures with combined medial and lateral wall defects (AO/OTA 31-A2.3). According to the AO/OTA classification, the unstable fracture type involving an isolated lateral wall defect (AO/OTA 31-A2.2) is also commonly encountered in clinical practice. Preservation of medial support has been suggested to mitigate instability-related complications; however, whether such preservation can counteract the adverse biomechanical effects of ventral blade insertion remains insufficiently explored in the existing literature.MethodsIn the clinical component, a series of patients with A2.2-type unstable intertrochanteric fractures (isolated lateral wall defect) treated with PFNA fixation were enrolled. The influence of blade trajectory on femoral head varus at nearly 6 months postoperatively was evaluated using both comparative and regression analyses. Additionally, the biomechanical consequences of blade orientation were assessed using a simulated A2.2 unstable fracture model.ResultsConsistent trends were observed across clinical and biomechanical analyses. Specifically, no significant difference in femoral head varus angle was detected between ventral and dorsal blade orientations (Ventral blade: 3.86±4.14°; Dorsal blade: 3.14±5.13°, p=0.565). Blade trajectory was not identified as an independent predictor of varus severity in this patient cohort with isolated lateral wall defects (p=0.565). Biomechanically, variations in blade direction resulted in only minimal differences in stress distribution and displacement of both the blade and femoral head under compressive and physiological loading conditions.ConclusionsThe preservation of medial support appears to mitigate the detrimental effect of ventral blade insertion on fixation stability in patients with PFNA-treated intertrochanteric fractures. This study substantiates, from a novel perspective, the biomechanical importance of medial support in maintaining stable fixation.