Risk factors for septic arthritis of hip in neonates and infants

INTRODUCTION

Septic arthritis (SA) results from the presence of microbial agents in a joint space. Septic arthritis is an orthopedic emergency; delay in diagnosis and treatment is the single most important factor affecting prognosis of septic arthritis in children. The involved joint must be decompressed as soon as diagnosis is suspected.

SA was a life threatening condition in the pre-antibiotic era; the bacteria gain access across the synovial membrane, and incite an inflammatory reaction, manifested by the presence of plasma proteins and polymorph nuclear cells in the joint, producing an effusion. If left untreated, proteolytic enzymes initiate articular destruction.

SA is a challenging clinical problem because (1) signs and symptoms may be subtle and overlap with those found in other conditions, (2) screening laboratory studies and synovial fluid cultures are relatively insensitive, and (3) optimal management, including duration of antibiotics and surgical approach is not evidence based.

SA occurs among all age groups but is most common in infants, younger children, peaking in those younger than age 3 years. Timely diagnosis is the most important prognostic factor in septic arthritis (SA). Early institution of therapy helps to prevent degenerative arthritis. Delay in diagnosis leads to a poorer outcome mainly in infants.

Other poor prognostic factors include infection of the hip joint, which may lead to aseptic necrosis of the femoral head; infection with S. aureus; and a prolonged passage of time before the synovial fluid is sterilized. Because of the availability of antibiotics, children rarely die from septic arthritis or its complications. Although chronic arthritis is uncommon, the short-term morbidity and costs, in terms of prolonged antibiotic therapy and hospitalizations, may be substantial.¹

Due to lack of awareness about this entity in primary care physicians, there is delay in diagnosis and treatment which in turn leads to complications like subluxation, dislocation or destruction of femoral articular cartilage and growth plate which are vividly described in literature.^2,3

As per children health point of view, it is necessary to study important direct or indirect determinants like risk factors, clinical presentation and laboratory investigations among arthritis of hip among children.

METHODS

Study design

Prospective interventional study

Sample size

With convenient sampling method 34 patients with septic arthritis of hip under one year of age were selected at Department of Orthopedics of a tertiary care centre during August 2011 to December 2013.

Study population

Children 0 day to 1 year.

Data collection methods

The pretested, semi-structured questionnaire was used for data collection.

Data management and analysis

After the completion of data collection, data entry and analysis was done by Excel 3.0.

RESULTS

In our study about 63% patients were less than 3 months of age and 75% patients were up to 3 years of age.

In our study more than 70% patients presented after one week. 2 patients presented after one month.

We had total 34 children and neonates of that 24 (71%) presented after 1 week.

*Multiple risk factors

In our study left sided hip involvement was more common followed by right hip. We had two patients with bilateral involvement

In our study we had total 34 infants and neonates. Of that 32 (94%) had NICU admission. One infant who presented at age of 7 months had no previous hospitalization. These suggest that NICU admission increases risk of septic arthritis.

In our study septicemia was commonest associated condition. In many of our patients there were more than one risk factors like septicemia, low birth weight, jaundice and ventilator support. Due to one neonate having more than one risks factor the number of patients is more than actual.

In this study 88% patients were treated previously with antibiotics. This was responsible for negative blood culture.

Suspension test was performed in all infants and neonates. It was positive in all the infants and neonates. This makes it very useful to diagnose septic arthritis of hip.

In this study about 75% infants & neonates had normal leukocyte count (Ranging from 6800 – 12000 per ml). In older children 60% patients had elevated count (Ranging from 12,500 – 27,800 ml).

In our study average ESR was 45mm per hour with a range from 20 to 100mm per hour. About 91% patients were with high ESR. In our study about 25 patients had high CRP level on admission irrespective of age. Normal CRP was seen in 5 patients they were very late presented cases.

In our study we had sent blood culture of all patients in that seven were positive with most common growth of Staphylococcus aureus. Our 57% patients had growth of S. aureus.

DISCUSSION

The diagnosis of septic arthritis is usually difficult and tends to be delayed in young infants. It is particularly difficult in neonates because the early signs of hip infection are unclear.^3,4 Choi evaluated residual deformity after treatment for septic arthritis in 31 children younger than 1 year of age, and concluded that premature birth as well as delay in diagnosis and start of treatment were associated with poor clinical outcome.³

No case of septic shock was encountered in our series but we had 14 cases of bacteremia which were isolated by blood culture. In cases of septic arthritis of the hip, infection probably starts from the metaphysis and then spreads into the joint as well as bone. It can thus cause osteomyelitis of the femur.

In our study 75% of the patients were less than 3 years of age which is similar to a study conducted by Griffin which showed that 70% of their patients were less than 4 years of age.⁵ He also reported that infants and young children were more likely to have poor results because of delay in diagnosis. We had female predominance in our study which is contrary to study by Bennett and Namnyak where they found male predominance.⁶ In our study left sided hip involvement was more common followed by right hip. We had two patients with bilateral involvement. It is contrary to study by Bennett; where he found that right hip (57%) involvement was predominant.⁶

In our study average ESR was 45 mm per hour with a range from 20 to 100 mm per hour. About 91% patients were with high ESR. It was similar to study by Klein, where he found that 95% presented with ESR greater than 20 mm per hour.⁷ In our study about 25 patients had high CRP level on admission irrespective of age which was similar to study by Khachaturian’s which they found 88% had an elevated CRP on admission.⁸

In our study we had 57% of patients which showed growth of MRSA out of all the patients which tested positive in blood culture. This was similar to study by Lunseth⁹ where he found 60% of the infection caused by S. aureus.

CONCLUSION

Septic sequelae were more common in neonates & infants with late presentation. So patients with risk factors like prematurity, low birth weight, septicemia, and NICU admission should be daily screened with strict aseptic precaution. So that early correct diagnosis and aggressive treatment helps in improving clinical outcome. Slight swelling, erythema, warm skin on the thigh, pseudo paralysis of the leg, and positioning in slight flexion and external rotation are possible early signs of hip infection. It is of utmost importance that the treating pediatrician should be familiar with these sign and symptoms of septic arthritis and whenever encountered in clinical practice should urgently refer such patients to an orthopedic specialist. Aggressive approach must be undertaken by the orthopaedician and should start with puncture and drainage, identification of organisms, and corresponding antibiotic administration. Initial use of antibiotics effective against MRSA should be considered without waiting for culture reports in NICU or in the neonatal nursery where surveillance showed MRSA positive.¹⁰

We were not able to specify precise values of laboratory investigations that would indicate urgent arthrotomy because the protocol suggested that it should be performed only when response to medical management was not satisfactory.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the institutional ethics committee

REFERENCES

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