Introduction:
The presence of microbial agents in joint space leads to infection of the joint tissues and fluid, resulting in septic arthritis. It is a rare condition, commonly seen in children under the age of four years, and involves mainly the hip and knee joints. Males are known to be more affected than females. The leading cause for the same is bacterial infection presenting as an orthopedic emergency requiring immediate attention.
What Are the Causes of Hip Septic Arthritis?
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Septic arthritis is mainly caused by bacterial infection. The causative organism is Staphylococcus aureus (S.aureus), which affects children above three years of age. Other bacteria include Streptococci, Enterobacter species, Haemophilus influenzae, Gram-negative bacteria like Neisseria gonorrhoeae, Escherichia coli (affects neonates and infants), Kingella kingae (known to affect infants and toddlers).
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These bacteria enter the body in various ways, such as an infected wound, skin infections, genital infections, fractures or injuries, foreign object penetration, intravenous injections, or surgery.
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The bacteria gets deposited following an injury or spreads from other parts of the body through the bloodstream, called hematogenous spread leading to inflammation and release of proteolytic enzymes. This causes the destruction of the joint components by necrosis of the epiphyseal bone.
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It can be due to direct penetration into the joints by trauma or due to pre-existing conditions like an abscess, septic bursitis, osteomyelitis, poor immunity, etc.
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It can also be caused by viral, fungal, or parasitic infections.
What Are the Signs and Symptoms of Hip Septic Arthritis?
Signs and symptoms include:
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Large joints like the hip or knee joints are affected. The joint appears red and swollen and is associated with severe pain.
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Decreased movements of the joint.
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Fever, headache, irritability, associated with weakness.
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In infants, the baby seems irritated and refuses to feed.
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Other symptoms like vomiting, sore throat, and loss of appetite are present.
What Are the Risk Factors Associated With Hip Septic Arthritis?
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Some of the risk factors that can be associated with hip septic arthritis include osteomyelitis, juvenile rheumatoid arthritis, and renal osteodystrophy.
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Immunosuppressive medications, HIV (Human immunodeficiency virus) infections, open wounds, and low immunity.
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Hematological disorders, sickle cell disease, purpura, skin infections, etc.
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Recent joint surgeries, blood-borne diseases, lung diseases, kidney diseases, etc.
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In neonates and infants, risk factors include delivery through cesarean section, neonates or infants in NICU (neonatal intensive care unit), or umbilical or venous catheterization procedures.
How Is Hip Septic Arthritis Diagnosed?
Hip septic arthritis requires immediate care and treatment, or it can lead to damage to the joints. The doctors initially take a complete history of the patient and perform a physical examination to check the movements of the legs. Pain and tenderness are seen on examination, and the patient resists weight bearing and movement in the joint. The following tests are advised:
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Blood tests to check the levels of White blood cells (WBC), erythrocyte sedimentation rate (ESR), and serum C-reactive protein (CRP). Blood cultures are usually positive in septic arthritis with elevated WBC, ESR more significant than 20 mm/hour, and CRP is more than 2.0 mg/L. (milligram per liter)
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Synovial fluid tests or hip aspiration for the presence of bacteria (gram stain) in the joint space show high lactic acid levels and increased WBC count.
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Phlegm and urine tests to determine the source of infection.
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X-ray is recommended to visualize the joint and the surrounding structures for any subluxation and dislocation of bones. In infants, prior to ossification of the femur (thigh) bone, widening of the joint space is seen, which is a sign of pus in the joint.
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Magnetic resonance imaging (MRI) to check the bone marrow and soft tissues surrounding the joints
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Ultrasound to detect and monitor effusion at the level of the hip joint.
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In children, septic arthritis should be differentiated from transient synovitis, which is done by following Kocher criteria. It includes the following criteria: Presence of fever more than 101.3F, ESR value more than 40 mm/hour (millimeter per hour), and WBC count of more than 12,000 cells/microlitre of serum, associated with the inability to bear weight on the affected side.
How Is Hip Septic Arthritis Managed?
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Treatment for hip septic arthritis depends on the symptoms and severity of the disease, age, and general health of the patient. Empiric antibiotic treatment is started immediately.
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Intravenous antibiotic therapy is started for two to four days, followed by oral antibiotics for three weeks is recommended.
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Analgesics like NSAIDs are prescribed to treat pain and fever. Dexamethasone may be administered to reduce the swelling.
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Incision and drainage of the pus are done in cases of late presentation or absence of response to antibiotics. Arthrotomy or arthroscopic drainage is the treatment of choice; however, open incision and drainage.
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In some cases, which do not respond to repeated aspirations, an open arthrotomy is carried out, wherein an incision is made below the anterior superior iliac spine, muscles are separated, and the hip capsule is exposed. The pus is then evacuated, necrotic tissues are debrided, and the joint is irrigated. The capsule is left open, but the skin is closed loosely over the drains. A spica cast is supported to prevent dislocation following surgery.
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Ultrasound or fluoroscopy-guided aspiration technique is followed, during which an 18 gauge needle is inserted, and the purulent fluid is aspirated, followed by irrigation. The procedure is done daily, approximately for four to five days, followed by antibiotic therapy. This procedure can treat small children and is usually done under local anesthesia.
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In infants, less than three months, first-generation cephalosporins or Clindamycin is prescribed. Above the age of three months up to five years, 2nd or 3rd generation cephalosporins like Ceftriaxone and Ceftazidime are prescribed.
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Following surgical incision and drainage, range of motion exercises to the affected joint may be started.
What Are the Complications of Hip Septic Arthritis?
Septic arthritis requires immediate management, or it can lead to severe complications like necrosis of the bone, called osteonecrosis leading to joint damage and long-term disability. It can restrict the growth of the leg if the growth plate gets affected, or it can also lead to femoral neck deformity.
Conclusion:
Hip septic arthritis is mainly caused by Staphylococcus aureus and is associated with severe pain, swelling, and fever. It is commonly seen in infants and children. It is usually treated with surgical incision, drainage, and antibiotic therapy. The condition is said to have a good prognosis by early diagnosis and appropriate treatment.
