CT MEASUREMENT OF THE FEMORAL VALGUS ANGLE IN THE INDIAN POPULATION VAISHYA R VIJAY V NWAGBARA IC AGARWAL AK Department of Orthopaedics, Indraprastha Apollo Hospital, New Delhi, India

Vaishya R – There are no conflicts of interest to declare Vijay V – There are no conflicts of interest to declare Nwagbara IC – There are no conflicts of interest to declare Agarwal AK – There are no conflicts of interest to declare

BACKGROUND Importance of restoration of the mechanical alignment of the limb in TKA - 1. Reduce the incidence of loosening significantly 2. Improve the long-term survival of the prosthesis. Alignment restored by appropriately placed bone cuts augmented by soft tissue release. Distal femoral cut depends on femoral valgus angle (FVA) Can be achieved through: computer navigation, patient specific instrumentation or a fixed valgus angle.

MATERIALS AND METHODS AIM – to assess normal variability of the FVA in Indian population whether it is justifiable to use a fixed FVA in all patients. CT scans of patients undergoing pre-operative evaluation for patient specific instrumentation were used. Study involved: 134 knees in 59 females and 19 males Bilateral in 59 cases and unilateral in 16 cases Male to female ratio of 1:3 Average age of the patients was 63.84 years (range: 43-86 years) Values were subjected to Student’s t-test and Pearson correlation coefficient to evaluate the statistical correlation between the genders, the ages, and the sides.

Centre of femoral head Centre of knee The centre of the femoral head is determined using the centre of the geometrical sphere which replicates the femoral head. Centre of knee The centre of the knee corresponds to the trochlear notch which is 5-10 mm anterior to the roof of the intercondylar notch.

Anatomical axis Mechanical Axis FVA The angle between the mechanical and anatomical axes measured. The line joining the centre of the femoral head and the centre of the knee joint The line joining the centre of the knee and the centre of the femoral shaft.

Distal femoral valgus angle (DFVA) data by gender and Side Parameter n KVA(°) Average Range Total no. of knee 134 5.83 ± 0.64 4 - 7.5 Male 19 5.81 ± 0.59 4.5 - 7 Female 56 5.84 ± 0.67 Left 68 5.86 ± 0.68 Right 66 5.8 ± 0.61 Male-left 5.84 ± 0.65 Male-right 15 5.77 ± 0.53 5 - 7 Female-left 49 5.87 ± 0.7 Female-right 51 5.81 ± 0.64 * Average is expressed as mean±SD

Parameter t P-Value Left/right 0.512 0.609 Male/female   Right 0.287 0.775 Left 0.141 0.888 There was no statistically significant difference (p>0.05) between the DFVA on the left and right side or between the males and females on either side

Correlation of FVA with side

CONCLUSION Although there are variations between FVA of individuals, the difference was not statistically significant. A fixed valgus angle of 6 degrees can be safely used during TKA in the Indian population.

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