In this paper we report a markedly increased rate of joint infections in adults in Iceland from 1990 to 2002. During the study period there was a mean annual increase of 0.61 cases/100 000 adult inhabitants. The incidence of 4.2 cases/100 000 adults in 1990–1994 is similar to the reported number in other studies3–6 16
but the incidence of 9.4/100 000 adults during 1998–2002 is considerably higher and statistically different (p<0.01). This change is primarily due to increase in iatrogenic infections following joint arthroscopies and arthrocentesis. It coincides with marked increase in the registered number of joint arthroscopies in Iceland and increased use of intra-articular steroids and joint-viscous supplements in Iceland during these years. However, this increase in SA following joint injections was not due to a higher number of arthrocentesis procedures performed by rheumatologists and orthopaedists. However, the increased use of intra-articular steroids and joint-viscous supplements suggests that the number of arthrocentesis procedures did indeed increase during this observational period. That scenario could be explained by higher numbers of arthrocentesis procedures being performed by other doctors. This is however purely speculative, since computerised documentation of arthrocentesis in primary care is mostly unavailable. Septic arthritis due to open joint surgeries did not increase over this time period.
The frequency of post-arthroscopic SA has been reported 0.1–0.5% at specific medical centres9–12
but to our knowledge this frequency has not been previously estimated based on a nationwide analysis. The estimated frequency in Iceland of 0.14% is similar to these previous reports.
There is very limited data available in the medical literature about the actual risk of SA following arthrocentesis. In early reports this risk was estimated at 0.005 to 0.0002% per arthrocentesic procedure.13–15
These percentages are lower than can be estimated from our study. According to the SSI registry in Iceland the total number of documented ambulatory arthrocentesis in Iceland performed by rheumatologists and orthopaedists is 6900 per year (). Additionally, an estimated maximum of 1000 arthrocentesis procedures are performed annually by general practitioners (L. Ólafsson, the Center of Health Care in Reykjavik, Iceland personal communication). Accordingly, the estimated risk of septic arthritis following arthrocentesis in Iceland is 3 infections/7900 procedures, or 0.037% per injection. Compared to other commonly performed procedures, an incidence of 0.037% per injection is not high. However, given the significant morbidity and 10–15% mortality previously reported in SA3–6 16
it is of utmost importance to avoid unnecessary infectious complications and to perform arthrocentesis according to the best standard of practice.
In our study 17,9% of SA in adults occurred post-arthrocentesis, which is alarmingly high compared to the frequency of 1.9–3% in previous studies.4 6 7
It has been suggested that intra-articular steroid17
injection may increase the risk of joint infection. Thus, the generally increased use of steroids and hyaluronans in Iceland () may explain the increased incidence of SA in Iceland.
Presumably organisms frequently enter the joint during arthrocentesis. Skin fragments introduced into the joint during arthrocentesis contained bacterial genes (by polymerase chain reaction) one third of the time.19
and despite standard sterilisation of the skin surface, organisms could be cultured from needle tips in 14–28% of events.20
The best standard of practice for arthrocentesis has not been thoroughly studied and method of sterilisation varies considerably among doctors;21
alcohol swabs, pivodone iodine and chlorhexidine have been used in different reports, all apparently with satisfactory results, although chlorhexidine arguably has the edge over the other two methods. Chlorhexidine resulted in better sterilisation of needle tips compared to alcohol swabs20
and chlorhexidine use yielded significantly lower skin pathogen contamination of blood cultures compared with pivodone iodine.22
It may also be of practical importance in the clinical settings that full bacteriocidal effects from pivodone iodine takes over 1 min to develop.22
As far as we know, all three types of antiseptic techniques are in use in Iceland but no survey has been conducted to assess their prevalence among doctors. We were not able to correlate the type of antiseptic technique used to the rate of SA in this retrospective study. Irrespective of this, a panel of experts from the American College of Rheumatology emphasised that intra-articular corticosteroid injections are “safe and effective when administered by an experienced doctor”.23
This may indeed be the most important factor in avoiding iatrogenic SA following arthrocentesis.
The clinical characteristics of SA have been previously reported in children24–28
in the elderly;29–32
and numerous reviews have been published on septic arthritis.33–36
Most previous studies in adults have been derived from selected regions or populations, although one report represented a whole communal region.5
The current report is the first study reporting a nationwide survey. We screened all microbiology laboratories in Iceland for positive joint fluid cultures, and all hospitals in Iceland for ICD-9 and-10 discharge diagnoses of bacterial arthritis. Our study has numerous clinical and laboratory findings similar to previous reports. Thus, the sex ratio of 1.7 (male/female), risk factors (including advancing age, RA, osteoarthritis (OA), DM, iatrogenic illness), joint involvement and pathogens cultured are quite comparable to these reports. In our study, the frequency of polyarticular involvement among adults was quite low (3.3%) compared to 8.4–19.5% in other studies7 8
and mortality among adults was only 2.7%, considerably lower than reported in most studies,3–6 19
although similar to some.29
Our study agrees with previous findings that markers of systemic inflammation (fever, leukocytosis, elevated ESR or CRP) can be normal on presentation in SA. In fact normal temperature, WBC count, ESR and CRP were observed in 42%, 46%, 12% and 15%, respectively, in adults (). Furthermore, although SA is usually associated with high synovial leukocyte count we observed counts less than 20 000 in 15% of adult cases. Our study emphasises the importance of obtaining blood cultures as well as synovial fluid cultures, and highlights the potential for false negative results if the patient has received oral antibiotics prior to obtaining cultures. Thus, the diagnosis of SA in adults according to our study should primarily be derived from thorough medical history and physical examination, supported by joint fluid WBC analysis and confirmed by synovial/blood cultures in 88% cases. Antibiotic exposure prior to synovial culture may decrease the culture yield to 63%.
Surprisingly, 39% of children with clinical picture of septic arthritis had negative synovial fluid and blood cultures. The clinical and laboratory characteristics were similar in culture positive and negative children. These results are identical to numerous other reports24–28
and to date no reasonable explanation has been put forward.
In summary, the incidence of septic arthritis has markedly increased in recent years due to increased number of arthroscopies and therapeutic joint injections. Although the frequency of SA per procedure has not changed, these results emphasise the importance of sterile technique and firm indications for diagnostic and therapeutic joint procedures.