Synovitis of the hip joint is also called temporary synovitis. It occurs most often in winter and spring and at the turn of autumn and winter, and is more common in children aged 5 to 10 years, more often in boys. It is the most common cause of acute hip pain in children. It is more common in males, and most children have an abrupt onset. The peak of onset is between 3 and 6 years old, with more right-sided than left-sided, and bilateral hip onset accounts for 5% of cases.
The cause of the disease is unclear and may be related to viral infections, trauma, bacterial infections and allergic reactions.
Clinical manifestations
Unilateral hip or groin pain is the most common clinical symptom, and some patients may present with mid-thigh or knee pain. In very young children, nocturnal cries may be present, and careful examination may reveal painful claudication.
A recent history of upper respiratory tract infection, pharyngitis, bronchitis, and otitis media should also be noted, as these can be present in nearly half of patients with hip synovitis.
Children with hip synovitis usually have no fever or a mildly elevated temperature, and hyperthermia is very rare.
Physical examination.
The affected limb is flexed at the hip with mild abduction and external rotation. In 1/3 of patients with hip synovitis, there is no obstruction to hip movement, but mild resistance to movement can be felt, especially during abduction and internal rotation of the hip.
Pain occurs with passive movement of the hip joint.
Keeping the patient in a lying position, the examiner rolls the patient’s lower extremity and can feel involuntary protective contractions of the affected muscles.
In patients with symptoms in the knee joint, the knee joint should be examined to exclude other diseases.
Imaging examinations
(1) X-ray examination There is usually no abnormal bone manifestation, sometimes it may show mild pelvic tilt, swelling of the hip capsule, widening of the joint space, without bone destruction.
(2) MRI examination Magnetic resonance examination shows widening of the hip joint gap and fluid in the joint cavity on the affected side, and it shows more clearly than the line plain film. MRI shows that the synovial tissue between the acetabulum and the femoral cartilage has a medium signal in T1W1 and a high signal in T2W1.
(3) B-mode ultrasonography The anterior femoral neck neck gap of the affected hip is significantly wider than that of the healthy side, with a bilateral difference of >1 mm. the anterior femoral neck neck gap, i.e. the maximum distance between the periosteal surface of the femoral neck and the outer edge of the joint capsule (the line dividing the joint capsule and the iliopsoas muscle).
Laboratory tests
Total blood leukocyte count is normal, or slightly elevated.
Blood sedimentation is normal or slightly elevated. Infectious arthritis is indicated if the blood sedimentation is significantly elevated, exceeding 20 mm/h, combined with an elevated body temperature exceeding 37.5°C and an elevated white blood cell count.
Significant elevation of C-reactive protein (CRP) is a sign of infectious arthritis.
Diseases that need to be differentiated are.
1. Perthes disease (femoral head epiphysitis)
Although this disease has claudication and hip pain, it has a long history, and the deformation and compression of the femoral epiphysis is visible on x-ray.
2. Rheumatic joint and rheumatic fever in children
This disease is also common in children, also has hip pain, muscle spasm, limp and other symptoms, but its condition is often progressive progressive development, the laboratory examination of white blood cell count and blood sedimentation may be elevated, and the disease more involved in multiple joints.
3.Septic arthritis
This disease also has hip pain, limp and pelvic tilt, but its body temperature is higher than normal, and its blood count is also higher than normal, and its condition is more serious, and pus can be extracted by hip aspiration.
4.Tuberculosis of the hip joint
It is a chronic disease with a long history and can show the systemic symptoms of tuberculosis at the same time.
5.Pediatric congenital hip dislocation
The limp is obvious, the “4” test is positive, if it is unilateral onset, both lower limbs are unequal, but there is no obvious hip pain, muscle tension, positive pressure pain, and the X-ray film has special performance.
Treatment.
1.Traction therapy
Applicable to all children with the disease. Patients lying supine, the affected limbs abducted 30 °, neutral position, continuous horizontal skin traction of the affected limbs, traction weight generally does not exceed 5 kg, traction time 7-10 days, in the traction at the same time asked patients to make quadriceps muscle static contraction exercises to prevent muscle atrophy. If the symptoms are mild, bed rest is feasible, avoiding weight-bearing treatment.
2.Manipulation therapy
It is suitable for patients with severe hip pain and hip synovial impingement.
3.Medication
Application of non-steroidal anti-inflammatory drugs can shorten the duration of symptoms.
4.Physiotherapy
It is often applied after the end of manipulation treatment, and it is appropriate to feel warm without burning sensation.
5.Surgical treatment
When conservative treatment is ineffective, surgery can be taken in time to remove the synovial membrane embedded in the joint to avoid delaying the disease.