Xipeng Wang1, Kiyokazu Fukui2, Ayumi Kaneuji3, Kenichi Hirosaki4, Hiroyasu Miyakawa4, Norio Kawahara3. 1. Department of Orthopedic Surgery, Liyuan Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430007, China. 2. Department of Orthopedic Surgery, Kanazawa Medical University, 1-1 Daigaku, Uchinada-machi, Kahoku-gun, Ishikawa, 920-0293, Japan. 66406kf@kanazawa-med.ac.jp. 3. Department of Orthopedic Surgery, Kanazawa Medical University, 1-1 Daigaku, Uchinada-machi, Kahoku-gun, Ishikawa, 920-0293, Japan. 4. Department of Machinery and Metal, Industrial Research Institute of Ishikawa, 2-1, Kuratsuki, Kanazawa, Ishikawa, 920-8203, Japan.
Abstract
PURPOSE: Although studies suggest that subchondral insufficiency fracture of the femoral head may cause rapidly progressive osteoarthritis of the hip, the mechanism of that relationship remains unclear. Our biomechanical study aimed to provide more data in this area by quantifying pressure distribution on the femoral head for normal and inverted hips and by determining the effects of labral inversion on pressure distribution across the joint, focusing on types of fracture under load. METHODS: We tested mid-sized fourth-generation composite femurs at 15° of adduction, and applied 1 mm/min of axial compressive force to the femoral heads until failure. Additionally, single loads (3000 N) were applied using Prescale film to investigate pressure distribution on the femoral head, with or without silicone rubber representing entrapment of an inverted acetabular labrum. RESULTS: In tests with an external load of 3000 N, the mean pressure for 10 × 5 mm of silicone rubber was 11.09 MPa, significantly greater (about 5.7-fold) than 1.94 MPa without silicone rubber. Different fracture patterns were observed with and without the 10 × 5 mm silicone rubber; when the 10 × 5 mm silicone rubber specimens were used, all eight cases showed fractures in the anterior femoral head. CONCLUSIONS: When silicone rubber representing an inverted acetabular labrum was placed between a hemispherical metallic platen and a composite bone model, the silicone rubber areas were subjected to extreme concentration of stress. The fractures that developed at the silicone rubber areas clearly represented subchondral fractures of the femoral head, rather than fractures of the femoral neck.
PURPOSE: Although studies suggest that subchondral insufficiency fracture of the femoral head may cause rapidly progressive osteoarthritis of the hip, the mechanism of that relationship remains unclear. Our biomechanical study aimed to provide more data in this area by quantifying pressure distribution on the femoral head for normal and inverted hips and by determining the effects of labral inversion on pressure distribution across the joint, focusing on types of fracture under load. METHODS: We tested mid-sized fourth-generation composite femurs at 15° of adduction, and applied 1 mm/min of axial compressive force to the femoral heads until failure. Additionally, single loads (3000 N) were applied using Prescale film to investigate pressure distribution on the femoral head, with or without silicone rubber representing entrapment of an inverted acetabular labrum. RESULTS: In tests with an external load of 3000 N, the mean pressure for 10 × 5 mm of silicone rubber was 11.09 MPa, significantly greater (about 5.7-fold) than 1.94 MPa without silicone rubber. Different fracture patterns were observed with and without the 10 × 5 mm silicone rubber; when the 10 × 5 mm silicone rubber specimens were used, all eight cases showed fractures in the anterior femoral head. CONCLUSIONS: When silicone rubber representing an inverted acetabular labrum was placed between a hemispherical metallic platen and a composite bone model, the silicone rubber areas were subjected to extreme concentration of stress. The fractures that developed at the silicone rubber areas clearly represented subchondral fractures of the femoral head, rather than fractures of the femoral neck.
Entities:
Keywords:
Biomechanical study; Contact pressure; Inverted acetabular labrum; Rapidly progressive osteoarthritis of the hip; Subchondral fracture of the femoral head