OBJECTIVE To determine by use of an in vitro model the potential for translocating sufficient numbers of bacteria into a joint during arthrocentesis through cellulitic tissue to cause sepsis.
SAMPLE Culture media containing 4 concentrations of Staphylococcus aureus and needles of 3 sizes.
PROCEDURES Needles (22, 20, and 19 gauge) were inserted through Mueller-Hinton agar that contained known concentrations of S aureus (103,104,105, and 106 CFUs/mL). After a needle exited through the medium, any agar plug within the needle bore was ejected into a sterile syringe and the contaminated portion of the needle was harvested. Sterile saline (0.9% NaCl) solution was used to emulsify the agar plug and wash the contaminated portion of the needle. The resulting solution was cultured to determine the number of bacterial CFUs that could be deposited into a joint during arthrocentesis through contaminated tissue.
RESULTS Needle gauge and bacterial concentration were both associated with the number of bacterial CFUs deposited after insertion through contaminated agar. Although all needle sizes were capable of bacterial translocation sufficient to cause septic arthritis, ORs for 20- and 22-gauge needles translocating > 33 CFUs of S aureus were significantly higher than the OR for a 19-gauge needle. The ORs for 20- or 22-gauge needles translocating > 33 CFUs of S aureus (the minimum population of S aureus known to cause joint sepsis) were 0.22.
CONCLUSIONS AND CLINICAL RELEVANCE Results for this in vitro model indicated that caution should be used when performing arthrocentesis through cellulitic tissue.
To describe histologic changes in the temporomandibular joints (TMJs) of horses of various ages.
22 TMJs from cadavers of 11 horses.
Horses were categorized into 3 age groups (group 1, 2 to 10 years old [n = 3]; group 2, 11 to 20 years old ; and group 3, > 20 years old ). Each TMJ was sectioned into 5-mm slices, preserved in formalin, decalcified in formic acid, and routinely processed for histologic analysis. Joints were systematically assessed by use of previously described methods. Multilevel mixed-effects models were used to examine the data.
The number of changes was significantly fewer and degree of changes was significantly less within the TMJs of group 1 horses, compared with those of group 3 horses. Comparison among groups revealed that the combination of temporal and mandibular scores for group 1 was significantly lower than for groups 2 or 3. Disk score did not differ significantly between groups 1 and 2, but disk scores of groups 1 and 2 were significantly lower than the disk score of group 3.
CONCLUSIONS AND CLINICAL RELEVANCE
The assessed lesions were associated with osteoarthritis, and they accumulated in the TMJs as horses aged. In the absence of signs of pain manifested as changes in mastication, behavior, or performance, it would be difficult to determine the point at which accrued pathological changes represented the onset of clinically important osteoarthritis of the TMJs.