Evaluation of the Effect of Distal Femoral Elevation on Radiographic Measurement of the Anatomic Lateral Distal Femoral Angle

Abstract

To determine the effect of elevation of the distal femur on radiographic determination of the anatomic lateral distal femoral angle (aLDFA) in an in vitro canine model. In vitro study. Cadaveric canine femora (n = 7 pairs). Dissected femora were positioned in a custom-mounting frame. The distal end of the frame was elevated in 5° increments from 0° to 45°, with craniocaudal (CrCd) radiographs obtained at each position. The aLDFA was measured from the radiograph of each femur at each elevation. Statistical comparison of measured values was performed and radiographs were evaluated for radiographic indicators of positioning. There was significant increase in measured aLDFA at all elevations >5° when compared to 0° elevation. The mean value for aLDFA increased from 92.3° at 0° elevation to 95.0° at 45° elevation. The femoral trochlear ridges and walls of the intercondylar fossa were identified as the most useful radiographic landmarks. The fabellae, though extrafemoral and inconsistently retained in the current study, may also be beneficial. The lesser trochanter and nutrient foramen were less useful landmarks because of anatomic variability. Elevation of the distal femur had a significant effect on measured aLDFA at all elevations greater than 5°.