Journal of Orthopaedic Trauma, Vol. 18, No. 10, 2004
Author: Joseph J. Gugenheim, MD, Robert A. Probe, MD, and Mark R. Brinker, MD
Click here to read the entire published article by Dr Brinker
Objective: To determine how axial rotation around the anatomic
axis of the femur, as would occur with malrotation of a femoral fracture,
affects frontal and sagittal plane alignment and knee joint orientation.
Design: Computer-generated models of the lower extremity were
constructed using standardized dimensions. To simulate a malrotated
fracture, these models were rotated in the shaft around the anatomic
axis in 15° increments from 60° internal to 60° external rotation. Rotation
was performed at the proximal fourth, mid-shaft, and distal
fourth.
Main Outcome Measurements: At each rotational position, the
mechanical axis deviation in millimeters and the changes in mechanical
lateral distal femoral angle in degrees were measured to quantify
frontal plane malalignment and malorientation, respectively. The mechanical
axis deviation in millimeters in the sagittal plane was also
measured at each rotatory position.
Results: Femoral shaft malrotation greater than 30° internal rotation
of a subtrochanteric fracture or more than 45° of a midshaft fracture or
external rotation of 30° or greater of a supracondylar fracture resulted
in frontal plane malalignment. External rotation of a supracondylar
fracture of 45° or more results in knee joint malorientation. Any external
rotation at all 3 fracture levels caused posterior displacement of
the weight-bearing axis in the sagittal plane.
Conclusions: Malrotation of a femoral shaft fracture is not just a
cosmetic problem. Internal and external rotation causes malalignment
and malorientation in the frontal plane, depending on the level of the
fracture and the magnitude of malrotation. External rotation of any
degree at the proximal fourth, mid-shaft, and distal fourth causes a
posterior shift of the weight-bearing axis in the sagittal plane.
Key Words: malrotation, femur fracture, intramedullary nailing,
malunion |
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