Components of a normal hip joint and a diseased hip joint
The hip joint is the largest weight-bearing joint in the body. It consists of two parts: the spherical femoral head at the proximal end of the femur and the acetabulum within which the femoral head is contained (Figure 1). The bony surfaces of both the femoral head and the acetabulum are covered with smooth articular cartilage as a cushion, allowing for more flexible movement between them. In addition, the normal hip capsule is lined with synovial tissue, which secretes a small amount of fluid that lubricates the hip joint and reduces wear between the femoral head and the acetabulum.
The surface of smooth hip cartilage is not innervated, so it is normally very flexible and does not cause pain. When the articular cartilage is severely damaged, the subchondral bone is exposed, which then wears away, hardens, and proliferates to form a bony mass (Figure 2). The subchondral bone has nerves and a rough surface, and the subchondral bone rubs against each other, resulting in constant and severe pain and swelling, which further worsens as the disease progresses and restricts movement. Eventually, various non-surgical methods failed and hip replacement was required.
Introduction to hip replacement
Hip joint replacement technology has become very mature, the artificial joint materials have developed greatly, more durable, the artificial joint design is more in line with human biomechanics, according to the different age groups, can choose a more reasonable type of prosthesis, the success rate of surgery is very high. The following figure shows the most commonly used biologic hip prosthesis (Figure 3).
1, acetabular prosthesis: often cobalt-chromium-molybdenum alloy acetabular cup and ultra-high polymer polyethylene or ceramic lining composition;
2. The femoral prosthesis (including the head and stem) is often a cobalt-chromium-molybdenum alloy, and a fixed stem is inserted into the femoral medullary cavity to stabilize the prosthesis. The joint surface of the artificial hip joint is smooth and flat, and the joint can move easily without causing pain.
Introduction to the routine total hip replacement operation.
1. Remove the femoral head neck (Figure 4);
2, grinding away the acetabular cartilage and subchondral bone (Figure 5);
3, implantation of acetabular prosthesis (Figure 6);
4.Expand the femoral medullary cavity;
5, implantation of femoral prosthesis (Figure 7);
6, joint repositioning (Figure 8).
Indications for hip joint replacement
1. Degenerative osteoarthritis;
2. Secondary osteoarthritis.
A. Aseptic necrosis of the femoral head;
B. Acetabular dysplasia;
C. Traumatic arthritis
3. Inflammatory arthritis
A. rheumatoid arthritis;
B. Ankylosing spondylitis;
C. tuberculous arthritis
4. Femoral neck fractures in the elderly (Garden type III or above).
Contraindications for hip replacement
1. Infectious lesions in the joint (osteomyelitis);
2. Infectious lesions in the soft tissues surrounding the joint;
3. Active tuberculosis of the joint;
4. Blood disorders.