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Joint lavage, although its efficacy is still under debate,1–6 seems to be effective, mostly, in the treatment of gonarthritis associated or not with chondrocalcinosis (CC).2,3,7 Paradoxically, acute pseudogout is a complication of this technique.8 Our study aimed at evaluating the incidence of pseudogout in 73 patients with gonarthritis, associated or not with CC, who underwent arthroscopic lavage (AL).
METHODS AND RESULTS
In this retrospective study we assessed the incidence of pseudogout attacks that occurred 24 hours after surgery in 73 consecutive patients with gonarthritis (52 women (71%), 21 men (29%)), who underwent AL of the knee at our hospital. All the patients had medium-severe symptomatic osteoarthritis, according to Kellgren and Lawrence’s classification (II-III-IV degrees),9 and were unresponsive to drugs (that is non-steroidal anti-inflammatory drugs, analgesics, disease modifying osteoarthritis drugs) and rehabilitative treatment.
AL was carried out with an arthroscopic sheath 5.5 mm in diameter and 12 cm long, preceded by intra-articular carbocaine 2%. Twenty three patients had radiological or laboratory signs of CC, including x ray evidence of meniscal and cartilaginous opacities and/or birefringent positive intra- and extracellular calcium pyrophosphate crystals (CPPD) in the synovial fluid (group A). The remaining 50 patients had gonarthritis with no evidence of CC (group B) (table 1). They were followed up clinically 1 and 10 days after the AL.
The relative risk of the incidence of pseudogout in group A compared with group B patients was estimated from the analysis of contingency tables, by odds ratios (ORs); the 95% confidence interval (95% CI) was also calculated. The differences between the two groups were studied by the χ2 and Fisher tests applied to a 2×2 contingency table. The association of age, sex, and radiographic osteoarthritis grade with pseudogout incidence after lavage was evaluated, respectively, by unpaired t test, Fisher test, and χ2 test carried out on contingency tables. A value of p<0.05 was considered significant.
Of the 73 patients treated (mean (SD) age 59.4 (6.7)), nine (12%) had an arthritic episode within 24 hours after surgery. In each of these cases, wet sinovianalysis confirmed the inflammatory nature of the phenomenon (leucocyte counts between 5×109 and 30×109/l); polarising microscopy demonstrated the presence of CPPD. In all nine cases, culture and bacterioscopic examination of the synovial fluids were negative. The joint was injected with steroids, and the phenomenon resolved completely within 24 hours.
Six of the nine patients with pseudogout attack (26%) belonged to group A, while three (6%) belonged to group B. The OR of group A compared with group B was estimated to be 5.5 (95% CI 1.24 to 24.60; p<0.05) (table 1).
The results of this study underline the significant incidence (26%) of pseudogout as a possible complication of AL in patients with CC (table I).
Among the pathogenic hypotheses, mechanical-traumatic is the most likely; in fact, the lavage fluid could promote “crystal shedding”, due to the release of CPPD embedded in the joint tissues.8
Furthermore, it should be noted that this complication was also documented in three patients with gonarthritis without radiological or laboratory evidence of CC. This might be due to the fact that in a variable percentage of cases, microscopy for crystals in synovial fluid may yield false negative results.3,10 According to our data the age, sex, and radiographic grade of the patients had no significant association with the incidence of pseudogout after lavage.
In conclusion, pseudogout should be considered as a possible complication of AL, mainly in patients with CC, with about a fivefold risk compared with patients with osteoarthritis.
We are grateful to Professor G Cevenini, Department of Surgery and Bioengeneering, University of Siena, for statistical assistance.
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