Septic arthritis

This chapter describes a rational approach to septic arthritis based on sound principles of pathology and therapeutics. Early diagnosis and prompt treatment are essential if normal function of the infected joint is to be restored. In any acute joint disease, infection must be suspected, and if present, detected. It is important to identify causative bacteria in order to administer the correct antibiotic. The clinical features are different in neonates, children and adults. Diagnosis is not usually difficult and may be aided by diagnostic ultrasound and arthrocentesis. Both antibiotics and joint lavage are essential parts of management. Successful outcome is based on effective treatment and results in normal joint function. Ineffective or delayed treatment may be crippling.     

Septic arthritis

This article presents a review of the current approach to diagnostic and therapeutic conditions of septic arthritis. Acute septic arthritis is an uncommon, but potentially fatal, emergency. Early diagnosis as well as prompt and effective treatment are essential to avoid either irreversible joint destruction or even death. The clinical features of this condition are different in neonates, children and adults. The definitive diagnosis of septic arthritis requires the direct demonstration of bacteria in synovial fluid or on positive culture of the pathogen. A combination of antibiotics and the prompt removal of purulent material from the affected joint constitutes the mainstay of successful treatment. In addition, this article discusses, in particular, prosthetic joint infection and gonococcal arthritis.     

Septic arthritis

Septic arthritis has increased in incidence in the United States in the past two decades, and increasingly affects an older population with a greater burden of chronic illness and a higher risk for drug-resistant organisms. Successful management depends on a high diagnostic suspicion, empiric antibiotic treatment, and joint drainage. A bacteriologic diagnosis is more likely with inoculation into blood culture bottles than plating on solid media. As MRSA increases in prevalence in the community, empiric anti-biotic regimens increasingly need to be active against MRSA.     

Septic arthritis.

Septic arthritis is a direct invasion of the joints by pathogenic micro-organisms. These micro-organisms and their products stimulate the release of pro-inflammatory cytokines and proteolytic enzymes that induce an inflammatory response and degradation of the cartilage. Staphylococcus aureus remains the most prevalent micro-organism, and the most important aetiological change has been the decreased incidence of gonorrhoea, which is related to changes in sexual behaviour as a result of the HIV epidemic. Diagnostic suspicion is based on clinical symptoms, imaging findings and examination of synovial fluid. Scintigraphy and magnetic resonance imaging are useful methods for localizing and defining the extent of infection. The definitive diagnosis is based on the isolation and culture of the pathogen from synovial fluid. Optimal cultures are obtained by inoculating the synovial fluid immediately into blood culture bottles. Treatment includes initial empirical antibiotics, which are modified according to the synovial fluid culture. It is recommended that 3-4 weeks of intravenous antibiotic therapy are followed by 2 or 3 more weeks of an oral regimen. Adequate drainage may be performed by means of repeated needle aspiration, arthroscopy or surgery. Recent studies on the pathogenic mechanisms of septic arthritis have led to the simultaneous use of intra-articular steroids and antibiotics in order to reduce articular damage.     

Septic arthritis in childhood

We studied retrospectively the pattern of septic arthritis in childhood at a major municipal hospital during a ten-year period. Hemophilus influenzae was the most common organism in septic arthritis in patients less than two years old and was associated with upper respiratory tract infections in nine of 12 patients (75%). Staphylococcus aureus was seen in seven of eight (87.5%) children above the age of five and was associated with history of trauma. All patients were black. Despite the high incidence of sickle cell disease in our hospital population, not one patient had sickle cell disease.     

Septic arthritis in sickle-cell thalassemia

The knee of a boy with sickle-cell thalassemia became infected with Salmonella enteritidis, sensitive to ampicillin. Doses of ampicillin that achieved antibacterial titers of 32 in synovial fluid failed to eradicate the organism. The synovial fluid exhibited severe hypoxia, hypercapnia, and lactic acidosis. Methods were developed to estimate the oxygen saturation of blood in regional venous capillaries, the degree of periarticular sickling, changes in the viscosity of local blood, and the articular ratio of blood flow to oxygen utilization. The results suggest that local vascular insufficiency associated with sickling may affect host response to infection and efficacy of antibiotics. The Salmonella C₁ readily transformed to an L form on hypertonic medium, thus acquiring resistance to ampicillin and other cell-wall inhibitors.     

Septic arthritis in the elderly

The clinical and microbiologic features of septic arthritis in 23 elderly patients are reviewed. Fifteen patients had pre-existing joint diseases, predominantly osteoarthritis and rheumatoid arthritis. Eight patients had underlying systemic illnesses, and eight patients were receiving systemic corticosteroid therapy prior to the development of septic arthritis. The knee was the joint most commonly infected. Although Staphylococcus aureus was the major pathogen (52.2 per cent of patients), enteric gram-negative bacilli were found in seven of 23 patients (30.4 per cent). Five patients died (21.7 per cent mortality), two as a result of their infection and three of nosocomial Pseudomonas sepsis. Eight of the 18 survivors (44.4 per cent) developed osteomyelitis in the contiguous bone. Return of joint function was slow in all patients. Septic arthritis in the elderly is difficult to treat and has a poor outcome, possibly because pre-existing joint disease is very common and enteric gram-negative bacilli are often the causative organisms.     

Septic arthritis of the glenohumeral joint

Seven patients (eight shoulders) with sepsis of the glenohumeral joint were studied clinically and radio-graphically. Despite the advanced age of the patients, the presence of gram-negative organisms, and multiple risk factors in each patient (including serious chronic underlying diseases), needle drainage and parenteral antibiotics were all that were required for successful management, provided early diagnosis with prompt institution of antibiotics and drainage occurred. Contrast arthrography safely guided therapy and revealed rotator cuff tears in four of six shoulders as well as frequent extra-articular extensions of the disease. A nonleukemic patient with Aero-monas hydrophilia sepsis and arthritis is reported who survived with eradication of infection and preservation of joint function. A poor prognosis for shoulder sepsis is not substantiated.     

Septic arthritis in heroin addicts.

Over a 6-year period (1982 to 1988), 36 episodes of septic arthritis were diagnosed in 35 heroin addicts from Barcelona, Spain. Thirty (86%) were men and five (14%) were women, with a mean age of 24 years (range, 14 to 39). Twenty-nine episodes (80%) were monoarticular and seven (20%) were oligoarticular. The sacroiliac (16 cases), sternoclavicular (8), hip (5), and shoulder (4) joints were most frequently infected. Staphylococcus aureus and Pseudomonas aeruginosa were the etiological agents in 75% and 11% of episodes, respectively. Response to antibiotic treatment was good in 32 cases (90%), eight patients needed surgical drainage, and none died. We conclude that septic arthritis in heroin addicts localizes predominantly in axial joints. In our geographic area, infection with S aureus is more frequent than with gram-negative rods such as P aeruginosa or Serratia marcescens, which are most frequently found in reports from the United States.     

Septic arthritis due to Aerococcus viridans

A 20-year-old woman was found to have septic arthritis of the hip due to Aerococcus viridans. This organism closely resembles Streptococcus viridans, but forms gram positive tetrads rather than chains in broth media. The organism has been reported rarely to cause endocarditis and one case of osteomyelitis has been observed. To our knowledge septic arthritis due to Aerococcus viridans has not been previously reported.     

Septic arthritis of the pubic symphysis

Septic arthritis of the pubic symphysis developed in a previously healthy 13-year-old boy. Blood cultures and the culture of material taken by joint aspiration of the pubic symphysis under radioscopic control yielded Staphilococcus aureus. Early treatment with parenteral antibiotics prevented the development of osteomyelitis of the pubic rami in our patient. Open debridement was not necessary.