Correlation of the torsion values measured by rotational profile, kinematics, and CT study in CP patients

The purpose of study was to analyze correlations between bony torsions measured by Staheli's rotation profile, computed tomography (CT) torsional study, and gait analysis in patients with cerebral palsy (CP).

The study group comprised of 26 children with CP (spastic diplegia, Gross Motor Function Classification System (GMFCS) 1-2, mean age 12.6 years) with torsional deformities. All subjects were assessed by examining: 1) rotational profile [internal rotation (IR) and external rotation (ER)], 2) CT torsional profile [femoral anteversion (FAV) and tibial torsion (TT)], and 3) gait analysis [mean hip rotation (HR) and mean knee rotation (KR)]. Statistical analysis was performed using the Pearson correlation test.

In the femur, there was good correlation between FAV and Staheli's rotational profile of IR and ER (Pearson correlation coefficient (PC=0.69, 0.52, p<0.05)). ER correlated very strongly with mean HR during gait (PC=0.8, p<0.05). There was, however, poor correlation between HR and IR (p>0.05), and between HR and FAV (p>0.05). In the tibia, mean KR correlated well with thigh-foot angle (TFA) (PC=0.72) and CT tibia torsion (TT) (PC=0.62). TT also correlated with TFA (PC=0.62).

Gait analysis and Staheli's rotational profile reflect both static and dynamic factors of gait abnormalities. However, CT study reflect static factor primarily. Dynamic factors tend to influence the measurements of the femoral torsion only due to large rotational arc of hip joint. In surgical planning, it must be considered that HR sometimes does not correlate with CT anteversion angle. Similarly, it must also be considered that KR correlates well with TFA and CT TT angle.