Mechanics of femoral head osteonecrosis using three-dimensional finite element method.
A three-dimensional finite element model of a femoral head was developed using a surface modeling technique. The distribution of the stress index S (S = effective stress / yield strength, sigma/sigmaY) in various sizes of segmental osteonecrosis was assessed. The stress index of the femoral head was within physiological limits when the necrotic angle was less than 110 degrees. Within both the subchondral region and the deep necrotic region adjacent to the necrotic-viable interface, values of the stress index significantly higher than the normal physiological level (>0.1) appeared when the necrotic angle was 110 degrees or more. In the analysis of 28 osteonecrotic femoral head specimens, fracture appeared in two major locations: the deep necrotic region near the underlying necrotic-viable interface (19 femoral heads) and the subchondral region (7 femoral heads). In 2 femoral heads, the fracture involved both regions. Both sites of fracture coincided with the region of stress index greater than 0.1 in the finite element model study. These results may provide baseline information for predicting the collapse of the femoral head and determining the treatment modality of early stage osteonecrosis.
Yang
Jin-Won
JW
Department of Orthopaedic Surgery, Gyeong-Sang National University School of Medicine, 90 Chilam-dong, Chinju 660-702, South Korea.
Koo
Kyung-Hoi
KH
Lee
Min-Cheol
MC
Yang
Philip
P
Noh
Myunggyu D
MD
Kim
Shin-Yoon
SY
Kim
Kang-Il
KI
Ha
Yong-Chan
YC
Joun
Man-Soo
MS
D001696:Biomechanical Phenomena; D003198:Computer Simulation; D005265:Femoral Neck Fractures / Q000503:physiopathology* / Q000601:surgery; D005271:Femur Head Necrosis / Q000503:physiopathology* / Q000601:surgery; D005592:Fracture Fixation / Q000379:methods; D006801:Humans; D008953:Models, Anatomic; D011237:Predictive Value of Tests; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical