Review Question - QID 8780

This patient has external rotational malalignment on the left side. With external rotational malalignment, physical examination will reveal greater external than internal rotation (using the tibia as a gauge of rotation).

Rotational malalignment is described using the distal fragment (with respect to the proximal fragment). If the distal fragment is fixed in external rotation, the tibia and patella will appear externally rotated at rest. On examination with the hip and knee flexed to 90°, the leg will appear to externally rotate more than the contralateral (unaffected) side, and internally rotate less than the contralateral side. With internal rotation malalignment, the leg will appear to internally rotate more than the contralateral side and externally rotate less than the contralateral side.

Karaman et al. examined the effect of rotational malalignment on daily life. They found that 42% of patients had rotational malalignment of ≥ 10° on CT scan. Functional scores and stair climbing tolerance were significantly decreased compared to those without rotational malalignment. They concluded that femoral rotational malalignment ≥ 10° is symptomatic and one should be aware of rotational alignment during surgery.

Dimitriou et al. used 3D CT to examine side-to-side rotational differences in normal femora (without fractures or fixation). They found significant side-to-side differences in femoral anteversion, horizontal offset, and femoral head center location. They concluded that relying on anatomic landmarks of the contralateral femur during hip arthroplasty may not necessarily result in restoration of native anatomy and leg-length.

Figure A shows examination of hip rotation in the supine (or seated) position. Figure B is a composite axial CT cut of bilateral femoral necks and condyles in the supine position. Assuming the right side is normal, rotational malalignment is -19°-10° = -29° malrotation (negative implying external rotation malalignment). Illustration A is another example with the left (injured) side demonstrating 40-15 = 25° malrotation (positive implying internal rotation malalignment).

Incorrect Answers:
Answers 1,3,4,5: There is -19°-10° = -29° malrotation (external malrotation) on CT. Using the tibia as a gauge, during examination of hip rotation, the externally malrotated limb will have increased external rotation and diminished internal rotation.