The Quadriceps Vector in the Lower Extremity of Indian Patients Is Similar in Caucasian and Japanese Patients.

Background: Correct alignment of knee components contributes to the longevity and function of total knee arthroplasty. The accuracy and reliability of calculating the three-dimensional quadriceps vector (QV) using computed tomography (CT) scans in Caucasian and Japanese study participants have been established in previous studies. In all cases, the QV was directed from the top of the patella to the middle of the femoral neck. The literature describes considerable differences in the morphology of bone in the lower extremities of Indian people compared with that of Caucasian and Japanese people.

Methods: An imaging study was conducted using CT scans to determine the QV in a cohort of 36 patients from India (18 women [mean age 59 years], 18 men [mean age 61 years]). The same measurement methods were used for this cohort as in previous studies. The QV and all measured axes were compared within the cohort.

Results: The QV for the Indian cohort was found to be directed from the top of the patella toward the femoral neck, as in Caucasian and Japanese CT scans. In the Indian knees, the passing point of the vector was found to be lateral 30.8 mm (range, 25.2 to 36.4) and anterior 31.2 mm (range, 28.4 to 33.9) to the femoral head. When projected to the coronal plane, the QV was closest to that of the spherical axis, 1.2 ± 0.8° (P < 0.05).

Conclusions: As in previous studies, the QV crosses the femoral neck lateral to the femoral head and is most parallel to the spherical axis (center femoral head to center spherical medial condyle) projected onto the coronal plane in the native Indian knee. These data suggest that using the QV for alignment may be applied to most human knees regardless of morphology.