A Study of Mechanical Axis and Anatomic Lateral Distal Femoral Angle (aLDFA) Deviations in Postoperative Distal Femur Fracture Fixation

Abstract

Background: Distal femur fractures are complex injuries associated with substantial functional impairment and a high risk of postoperative malalignment. Restoration of the mechanical axis and anatomical lateral distal femoral angle (aLDFA) is essential for achieving optimal clinical outcomes following surgical fixation. This study evaluated postoperative mechanical alignment, radiological parameters, and functional outcomes in patients undergoing distal femur fracture fixation.

Methods: A prospective observational study was conducted among 30 adult patients with distal femur fractures treated surgically at a tertiary care hospital between January 2025 and July 2026. Patients were followed for six months. Clinical evaluation included the Visual Analogue Scale (VAS) for pain and the modified Mize criteria for functional outcome. Radiological assessment comprised Mechanical Axis Deviation (MAD) and Anatomical Lateral Distal Femoral Angle (aLDFA), measured at the final follow-up and compared with the contralateral normal limb. Statistical analysis was performed using SPSS version 20.0, with a p-value <0.05 considered statistically significant.

Results: The majority of patients were males (70.0%) aged 46–60 years (43.3%), with closed fractures accounting for 86.7% of cases. Pain scores improved significantly during follow-up, with the mean VAS decreasing from 4.9 at one month to 0.87 at six months (p<0.001). Excellent and good functional outcomes were achieved in 80% of patients. The mean MAD (5.8 ± 2.6 mm vs. 6.7 ± 3.2 mm; p=0.237) and mean aLDFA (81.2 ± 1.8° vs. 80.4 ± 2.3°; p=0.356) did not differ significantly between the operated and contralateral limbs. Open fractures and complex Müller type C fractures were significantly associated with poorer functional outcomes.

Conclusion: Surgical fixation of distal femur fractures achieved satisfactory restoration of mechanical alignment and anatomical distal femoral geometry, resulting in favorable functional outcomes in most patients. Fracture severity, particularly open and complex fracture patterns, significantly influenced postoperative recovery, whereas minor deviations in MAD and aLDFA did not adversely affect short-term functional outcomes.