Diagnostic points】
1.Clinical characteristics
(1) The age of onset is mostly 15~20 years old, and it is rare to see the onset after 40 years old.
(2) The pain and stiffness of the lower back and lumbar region with insidious onset is especially obvious when waking up in the middle of the night, rising in the morning and standing up after sitting for a long time, and can be relieved by a little activity.
(3) The spine gradually becomes restricted in movement from the lumbosacral region downward (including forward flexion, lateral flexion and back extension in all directions) and deformed, and may involve the spinal ribs and sternoclavicular joints. Positive tests include Schober’s test <5cm, occipital wall test >1cm, and chest expansion <2.5cm;
(4) Peripheral arthritis mainly involves the shoulder, hip, knee and ankle, mostly asymmetrically.
(5) Heel pain and tendon telangiectasia are one of the characteristics of the disease, especially in the young onset.
(6) Systemic symptoms include weakness, weight loss, fever and anemia. In some cases, there are extra-articular manifestations such as iritis, cardiac conduction disorders, aortic atresia, bilateral upper lung fibrosis, cauda equina syndrome and amyloidosis.
(7) X-rays show unilateral or bilateral sacroiliac arthritis, blurring of the spinal vertebral tuberosities, squared-off vertebral body changes, calcification of the paravertebral ligaments and bamboo-like spine.
(8) HLA-B27 positive rate >90%, rheumatoid factor negative.
(9) The disease may overlap with Wright’s syndrome, psoriatic arthritis or enteropathic arthritis.
2. Diagnostic criteria Referring to the 1984 revised AS New York classification criteria.
(1)Lower back pain: lasting for at least 3 months, relieved by activity and not relieved by rest;
(2) Restricted lumbar anterior flexion, lateral flexion and posterior extension activities.
(3) Decreased expansion.
Bilateral sacroiliac arthritis grade 2~3, unilateral 3~4 stringing plus any one of 1~3 is definite AS.
Sacroiliac joint x-ray grading.
Grade 0: normal ;
Grade 1: suspicious changes;
Grade 2: minor abnormality, limited erosion, sclerosis, no change in joint space;
Grade 3: Definite abnormality, moderate or progressive sacroiliac arthritis with one (or more) of the following changes: erosion, sclerosis, widening/stenosis or partial ankylosis;
Grade 4: severe abnormality, complete joint ankylosis.
Differential diagnosis
1. Differentiation of AS from disc herniation The latter is of acute onset; mostly limited to lumbar pain, aggravated by activity and relieved by rest; often lateral flexion on standing; palpation with one to two tender trigger points in the spinal bony prominence, sciatic nerve pressure at the hip, straight leg raise test (+); normal ESR and CRP; lumbar X-ray intervertebral space stenosis or anterior narrowing and posterior widening or anterior and posterior equal width; posterior superior or inferior angular labral hyperplasia of the vertebral body margin or with free small bone mass; CT can be confirmed.
2. Etiology and differential diagnosis of lower back pain a. Mechanical: OA, spinal stenosis, lumbar disc herniation, etc.; b. Rheumatic: SpA, myofibrositis, vertebral chondritis, lumbar disc hypertrophy, Whipple’s disease, rheumatic polymyalgia, dense osteitis; c. Endocrine: osteoporosis, osteochondrosis, parathyroid disease; microcrystallization; d. Neuropsychiatric diseases: psychogenic rheumatism; depression, etc.; e. Paget’s disease (deformational osteitis), spinal tuberculosis; f. Infections: inflammation of the articular disc, Lyme disease, herpes zoster; g. Tumors: lipoma, osteochondroma, metastatic carcinoma of bone, chondrosarcoma, lymphoma; h. Hematological system: giant cell tumor; i. Radiological pain: abdominal/thoracic aorta, intestinal, pancreatic, biliary diseases; g. Subacute endocarditis; k. Retroperitoneal fibrosis inflammation; l. pelvic inflammatory disease.
3. common causes of chronic low back pain osteophytes; herniated discs; degenerative disc disease; dense osteitis; fracture dislocation; spinal tuberculosis; primary osteoporosis; metastatic cancer; abdominal and pelvic inflammation; ankylosing spondylitis; myofibrositis; occult spina bifida; sacralization of the lumbar spine (Table 1).
[Treatment overview].
Principles of management of AS.
1, Disease education helps to improve patient compliance.
2, NSAIDs can be used for pain relief and inflammation control, indomethacin suppositories are preferred; salazosulfapyridine 2.0/d and/or methotrexate 7.5~10 mg/week may help to slow down the disease process.
3. Early detection and management of acute iritis and other serious extra-articular complications is as important as early diagnosis.
4. Regular daily physical therapy to maintain good posture, reduce deformity, and maintain chest expansion.
5.Surgery may help to correct spinal deformity and improve joint function.
6.Family history investigation and, if necessary, physical examination of the patient’s relatives can reveal significant family aggregation to detect undiagnosed or misdiagnosed cases.