Femur Length as a Predator of Femur Head Diameter in Nigerians

Introduction: The femur forms the skeleton of the thigh and its proximal segment is a component of the hip joint which is the largest mobile synovial joint of the human body. Although, the hip joint has a very remarkable stability, it may become dislocated with accompanying fracture of the femoral head and neck sequel to considerable trauma. Definitive management of intracapsular fracture neck of the femur in the elderly is surgical operation at which the fractured proximal end of the femur is replaced with an inert metallic implant.

Methodology: This study set to establish the length of the femur, diameter of the femur head and the relationship between these two parameters in Nigerians (Black Africans) using direct bone measurement technique.

Results: The sample size (human femur) was 266 with 51.1% (136) being right and 48.9% (130) being left. The respective mean length of the right, left and that of overall was similar (42.89±2.96; 42.78±2.86 2.83±2.90) cm. The median length of the femur irrespective of the side was the same (43.00 cm) and the range was 37-49 cm.

The diameter of the head of the femur along the sagittal (supero-inferior) plane ranged between 3.56 to 5.09 on the right, 3.49 to 4.88 on the left and 3.49 to 5.09 cm overall. The mean supero-inferior diameters were also very similar (Right- 4.28±0.30; Left- 4.26±0.36 and Overall-4.27±0.33 cm). The median supero-inferior diameter was 4.31 cm. The mean horizontal (medio-lateral) diameter was not significantly different along-side (Right- 4.48±0.33; Left- 4.46±0.33 and Overall-4.47±0.33 cm). Also the median horizontal diameters were very similar ie 4.46, 4.48 and 4.47 cm respectively. The medio-lateral diameter ranged from 3.67 to 5.37 cm and no side difference. The average diameters (i.e. supero-inferior + medio-lateral/2) of the femur were similar (Right- 4.38±0.30; Left- 4.36±0.33 and Overall-4.37±0.32 cm). The median value of the average diameter was similar side-wise (Right-4.46, Left-4.48, Overall-4.47 cm). The average diameter of the femur ranged between 3.62 to 5.17 cm.

There was no significant difference between the mean area of the femur head computed from the two diameters.

The ratio of the head diameter to the bone length was the same irrespective of the diameter or the side of the femur (0.1±0.01) also the median value was 0.1 cm. The correlation coefficient (r), of the ratio of the head diameter to bone length was positive for both the right and left side.

Conclusion: A linear relationship exists between the head diameter and the length of the femur. In essence the wider the diameter of the head, the longer the length of the femur.