Heyman and Herndon measured the head and neck dimensions of the femurs to derive the head-neck index and quotient in a patient with Legg-Calve-Perthes disease.
Measurements:
(1) length of the femoral head and neck along the center of the neck to the intertrochanteric line in mm
(2) width of the neck at its narrowest diameter in mm
head-neck index on affected side =
= (length on the affected side) / (width of the affected side) * 100
head-neck index on normal side =
= (length on the normal side) / (width of the normal side) * 100
head-neck quotient =
= (head-neck index on affected side) / (head-neck index on the normal side) * 100
Interpretation:
• The normal range for the head-neck index is 150 to 190.
• The normal range for the head-neck quotient is around 100. The lower the value the greater the deformity on the affected side.
Limitations:
• One side needs to be unaffected/normal.
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