Mechanism
Functional anatomy
The hip joint is a ball-and-socket joint. The femur connects at the acetabulum of the pelvis and projects laterally before angling medially and inferiorly to form the knee. Although this joint has three degrees of freedom, it is still stable due to the interaction of ligaments and cartilage. The labrum lines the circumference of the acetabulum to provide stability and shock absorption. Articular cartilage covers the concave area of acetabulum, providing more stability and shock absorption. Surrounding the entire joint itself is a capsule secured by the tendon of the psoas muscle and three ligaments. The iliofemoral, or Y, ligament is located anteriorly and serves to prevent hip hyperextension. The pubofemoral ligament is located anteriorly just underneath the iliofemoral ligament and serves primarily to resist abduction, extension, and some external rotation. Finally the ischiofemoral ligament on the posterior side of the capsule resists extension, adduction, and internal rotation. When considering the biomechanics of hip fractures, it is important to examine the mechanical loads the hip experiences during low energy falls. Biomechanics
The hip joint is unique in that it experiences combined mechanical loads. An axial load along the shaft of the femur results in compressive stress. Bending load at the neck of the femur causes tensile stress along the upper part of the neck and compressive stress along the lower part of the neck. While osteoarthritis and osteoporosis are associated with bone fracture as we age, these diseases are not the cause of the fracture alone.
At one year after fracture, this may reach 30%. If the condition is untreated the pain and immobility imposed on the patient increase that risk. Problems such as pressure sores and chest infections are all increased by immobility. The prognosis of untreated hip fractures is very poor. Post operation
Among those affected over the age of 65, 40% are transferred directly to long-term care facilities, long-term rehabilitation facilities, or nursing homes; most of those affected require some sort of living assistance from family or home-care providers. 50% permanently require walkers, canes, or crutches for mobility; all require some sort of mobility assistance throughout the healing process. Most of the recovery of walking ability and activities of daily living occurs within 6 months of the fracture. After the fracture about half of older people recover their pre-fracture level of mobility and ability to perform instrumental activities of daily living, while 40–70% regain their level of independence for basic activities of daily living.Among those affected over the age of 50, approximately 25% die within the next year due to complications such as blood clots (deep venous thrombosis, pulmonary embolism), infections, and pneumonia.Patients with hip fractures are at high risk for future fractures including hip, wrist, shoulder, and spine. After treatment of the acute fracture, the risk of future fractures should be addressed. Currently, only 1 in 4 patients after a hip fracture receives treatment and work up for osteoporosis, the underlying cause of most of the fractures.