You are an intern in the emergency department in Broken Hill.
Ricky Eggerton is a 5-year-old boy who is a keen AFL player. He presents with a 1-day history of increasing pain and swelling in his left knee. He refuses to walk and is miserable. His mother informs you that he has had a temperature for 2 days and he has not been his usual active self since yesterday.
History of presenting symptom:
Other history:
General Appearance:
Vital signs:
Examination of the knee:
Systems review:
Septic Arthritis:
Local features include:
General features include:
Osteomyelitis:
The patient usually presents with pain, malaise and a fever and in neglected cases toxaemia may be marked. Sometimes a history of preceding skin lesion, an injury or sore throat may be obtained, the limb is held still and there is acute tenderness near the largest joint. Even gentle manipulation is painful and joint movement is restricted. Local bone tenderness, swelling, warmth and oedema are later signs and signify the presence of pus.
Acute Haemarthrosis:
Usually follows an injury of a joint and presents with a swollen and tense joint. The patient resists any attempt in moving it.
Transient Synovitis:
Transient synovitis, or Irritable hip, is a common disorder of childhood which presents with the acute onset of hip pain and a limp that gradually resolves.
The history is one of an acute onset of hip pain and a limp, followed by knee pain and inability to weight bear. Boys are affected more often than girls by about 2:1. The mean age at presentation is about 6 years with a range from two to twelve years. Both hips are affected equally but it is rare for more than one hip to be involved.
On examination, the affected leg tends to be held in the position of greatest ease, typically, one of flexion, abduction and slight external rotation. The child is otherwise well. Symptoms usually persist for 1-2 weeks then resolve spontaneously. Months may elapse between episodes.
Aetiology:
In all age groups, the most common infecting organism for septic arthritis is Staphylococcus aureus. Other common pathogens include Streptococcus species, Pseudomonas aeruginosa, pneumococci, Neisseria meningitidis (with or without an associated meningitis), Escherichia coli, Klebsiella species, and Enterobacter species. Newborns can acquire Neisseria gonorrhoeae from an infected birth canal. Gonococcal arthritis is more common in sexually active teenagers, and it may be seen in younger children in association with sexual abuse.
A neonate aged 5 weeks or younger is susceptible to infection as a result of a wide range of organisms that are unlikely pathogens in children with more developed immune systems. S aureus is still the most common pathogen in this age group; group B streptococcus is the next most common pathogen. Gram-negative organisms may be seen in as many as 15% of joint infections affecting neonates in a neonatal intensive care setting. Candida albicans may also be present in these patients, as well as in patients who have received prolonged antibiotic therapy.
Pathogenesis:
Although it is uncommon, a penetrating wound may result in septic arthritis. It also may develop by contiguous spread from an adjacent cellulitis. Most commonly, however, the pathogenesis of septic arthritis is haematogenous. Transient episodic bacteraemia is common, even in healthy individuals. It may occur with something as simple as tooth brushing. In almost all cases, the body's defence mechanisms rapidly eliminate the threat; occasionally, bone or joint infection may result.
Hematogenous septic arthritis may develop directly through the synovial blood vessels. Another common route is from an adjacent hematogenous metaphyseal osteomyelitis. Just under the metaphyseal side of the growth plate in a growing child, vascular loops nourish the bone that forms in association with enchondral ossification. Blood flow in these loops is thought to be relatively slow, and this region is somewhat poorly defended by the reticuloendothelial system. These loops form the site of origin for hematogenous osteomyelitis in infancy and childhood.
Whatever the mechanism, once bacteria enter the joint; the space effectively becomes a closed abscess. A variety of enzymes capable of degrading articular cartilage are released by leukocytes and by certain bacteria, such as S aureus and some gram-negative organisms. Significant articular damage can occur in as little as 8 hours. Increased pressure within the joint can interrupt the blood supply to the epiphysis, causing bone destruction and loss of the adjacent growth plate. If the infection remains untreated, the ligaments of the capsule will be destroyed and the joint may dislocate. For example, the extreme result in a septic hip would be complete destruction of the femoral head, dislocation of the proximal femur from the acetabulum, and loss of 30% of all future growth of the affected femur.
Important investigations in infective arthritis include:
Patients with suspected septic arthritis should be referred urgently and immediately for hospital specialist review.
Equipment:
Location:
The most important landmark for aspirating the knee is the lateral edge of the patella.
Post op advice for patients:
Avoid strenuous activity for the following 24 hours.
Contraindications:
Patients with suspected septic arthritis should be referred urgently and immediately for hospital specialist review.
Synovial fluid should be obtained - for gram-staining, culture and crystal analysis.
Following joint aspiration, empirical IV antibacterial therapy should be commenced - coverage should be for staphylococci and streptococci in adults, and, additionally, Haemophilus in children; the regimen can be modified in the light of culture and sensitivity results. Treatment should be given for several weeks but the optimal duration of therapy is unknown.
Where the joint is accessible - needle aspiration should be used to decompress the joint. Surgical drainage is indicated, using either arthroscopy (particularly useful for the knee) or arthrotomy (particularly useful for the shoulder or hip) if aspiration is required more than 3 times per day, or if adjacent soft tissue is affected, or if there is no response to 5 days of aspiration plus antibacterial therapy, or if the joint is difficult to aspirate.