Ankylosing spondylitis (AS) is a chronic progressive inflammatory disease that primarily affects the spine and involves the sacroiliac and peripheral joints. ankylosing spondylitis was identified as a disease by the American College of Rheumatology (ARA) in 1963. The relationship between HLA-B27 and ankylosing spondylitis and spondyloarthropathies, discovered 25 years ago, is notable for the high incidence of mid-axis myelitis and synovitis, and ultimately for fibrosis and advanced bony ankylosis of the sacroiliac joints and spine. Almost all patients with ankylosing spondylitis have varying degrees of sacroiliac joint involvement, typically with prolonged fixation in a particular position or worsening symptoms upon awakening in the morning (“morning stiffness”), which can be improved by somatic activity or hot baths. Tendonitis, the main feature of spondyloarthropathies, is inflammation originating in the ligaments of the affected joint or in the area where the joint capsule attaches to the bone, near the articular ligaments, and in the synovial, cartilaginous, and subchondral bone.
Most patients first present with symptoms of sacroiliac joint involvement, but some patients may also first present with symptoms of higher spondylolisthesis, which manifests as lower back stiffness and pain, often radiating to one or both buttocks, occasionally to the thighs, and further to the dorsal aspect of the knee, or even below the knee. The lower extremity extension and elevation sign is usually negative due to local inflammation of the sacroiliac joint. Pain can be induced by direct pressure on the diseased joint or by straightening the affected lower extremity. Restriction of lower back motion and mild paravertebral muscle spasm of the sacroiliac joint can occur early in the course of the disease. Pain may also be induced by finger pressure on the pubic symphysis, iliac crest, and sciatic tuberosity. The sacroiliac joint is symmetrically involved, and the pubic symphysis can also be involved.
More than 1/3 of patients may have involvement of the shoulder and hip joints, which further aggravates the disabling consequences for the patient. The joint pain is often mild, but the joint motion limitation is obvious, such as the inability to comb hair or squat. As the disease progresses, cartilage degeneration and fibrosis of the periarticular structures may occur, leading to joint ankylosis. Early in the course of the disease, the limitation of joint motion is mainly due to spasm of the muscles surrounding the joint. Hip contracture and compensatory flexion of the knee joint may cause the patient to be in a forward bowing and flexing position, and a duck walk may occur. Due to extensive spinal joint lesions, flat chest and severe hunchback can also be caused. Some patients are affected outside the joints, such as the eyes, kidneys, and heart.
In the advanced stage of ankylosing spondylitis, the joints are painless because the inflammation has largely disappeared, and spinal fixation and ankylosis are the main manifestations. The cervical spine is fixed in an anterior tilt, the spine is kyphotic, the thorax is often fixed in an expiratory state, the lumbar spine loses its physiological curvature, the hip and knee joints are severely flexed and contracted, the eyes stare at the ground when standing, and the body weight shifts forward. Individual patients can be severely disabled, bedridden and unable to take care of themselves for long periods of time.
There are no diagnostic or specific tests for ankylosing spondylitis. HLA-B27 testing can be helpful in the diagnosis of ankylosing spondylitis, but the vast majority of patients can only be diagnosed by history, signs, and x-ray examination.
Pathological changes in the joints of ankylosing spondylitis.
(1) Synovitis: Synovitis is the earliest pathological change that occurs in joints involved in ankylosing spondylitis. Microscopically, inflamed synovial tissue can be seen as hyperplasia and hypertrophy, villi formation, and infiltration of plasma cells and lymphocytes around small vessels. This inflammatory synovial tissue can release inflammatory mediators, causing painful swelling of the joint; it can release a variety of enzymes, destroying joint cartilage and bone tissue and eventually causing joint destruction. The lesions mostly start from the sacroiliac joint and gradually invade upward to the lumbar, thoracic and cervical vertebrae. The shoulder joint, temporomandibular joint, transverse rib joint, cribriform joint, sternoclavicular joint, sternoclavicular stalk joint, and pubic symphysis are also often involved.
(2) Inflammation of ligaments and tendon bone attachment points
This is a characteristic pathological change in ankylosing spondylitis, in which aseptic inflammation occurs at the attachment sites of ligaments, tendons, and joint capsules, and the granulation tissue generated during the inflammatory process can destroy cancellous bone.
(3) Osteomalacia and osseous fusion
In the late stages of ankylosing spondylitis, osteophytes in the affected joints become increasingly evident, especially in the joint capsule and ligament calcification or ossification is very prominent, and eventually the affected joint space completely disappears, and bony ankylosis occurs, this bony ankylosis often occurs in the sacroiliac, spine and hip joints, less often in the knee and ankle joints, this change occurs in the spine that forms the pathological basis of the bamboo-like changes on X-ray.
The following picture shows the bamboo-like changes in the spine on X-ray
Diagnosis
Sacroiliac arthritis is the pathological hallmark of ankylosing spondylitis and is often one of its earliest pathological manifestations. Sacroiliac joint changes are the main basis for the diagnosis of the disease. It can be argued that a normal x-ray of the sacroiliac joint can almost exclude the diagnosis of this disease. Early radiographic changes of the sacroiliac joint are more characteristic and easier to recognize than those of the lumbar spine. Generally speaking, the sacroiliac joint can have three stages of changes.
(1) Early stage: joint margins are blurred and slightly dense, and the joint space is widened.
(2) Middle stage: the joint space is narrowed and the joint edges are jagged with bone erosion and dense hyperplasia.
③Late stage: joint gap disappears, with bone trabeculae passing through, showing bony fusion.
Diagnostic criteria
-Clinical indicators
C lumbar pain and lumbar stiffness for more than 3 months, improving with activity but not relieved by rest
C limited movement in the sagittal and coronal planes of the lumbar spine
C Restricted chest expansion compared to normal values for relevant age and gender
-Imaging indicators
C bilateral sacroiliac arthritis ≥ grade 2, or unilateral grade 3 to 4
-Compliance with imaging indications with at least 1 clinical indication confirms the diagnosis
Treatment
Because the pathogenesis of ankylosing spondylitis is not clear, the treatment of this disease is only symptomatic, and drug therapy is the most basic treatment, but most of the literature reports that simple drug therapy is not effective in controlling the progression of the disease, and many patients even develop serious drug side effects, such as gastric bleeding, severe allergies, etc. Tsinghua University Yuquan Hospital has proposed a “four-component systemic therapy” for ankylosing spondylitis pathology and imaging, namely: self-treatment, drug therapy, local joint minimally invasive treatment, and systemic autologous blood anti-inflammatory therapy. The following are introduced.
Self-treatment
In order to prevent spinal deformity, swimming is a better method, which requires daily adherence.