A3 Structural Bone Failure

Title

Structural failures in the musculoskeletal system include bone fractures (acute or stress), articular cartilage injuries, and structural damage to supporting connective tissue. Stress fractures occur when repeated cyclic loading exceeds the capacity for bone remodeling: microscopic damage accumulates faster than it can be repaired, ultimately leading to macroscopic fracture. They follow the Wöhler fatigue model: the lower the cyclic stress amplitude, the greater the number of cycles until fracture. Articular cartilage, lacking vascularization, has very limited repair capacity; Its degradation follows Archard's equation for wear. Acute fracture occurs when the instantaneous stress exceeds the ultimate strength of the bone (170 MPa in compression). The risk of fracture is evaluated with the safety factor FS = _ult/_applied. Avulsion fractures (tearing of the bone by the tendon) occur when tendon force exceeds the resistance of the bone insertion.

ID:234