[The short-term outcomes of non-contact low frequency ultrasonic debridement in treating periprosthetic joint infections:a prospective single-arm clinical study].

Objective: To evaluate the short-term outcomes of non-contact low-frequency ultrasonic debridement in treating periprosthetic joint infections(PJI). Methods: The clinical data of patients with PJI who met the eligibility criteria and were treated with non-contact low-frequency ultrasonic debridement from August 2021 to January 2022 at the Department of Orthopaedics,the First Affiliated Hospital of Xinjiang Medical University were prospectively analyzed. PJI was defined according to the modified Musculoskeletal Infection Society criteria in 2016. After mechanical debridement,an 8-mm handheld non-contact low-frequency ultrasound probe was used for ultrasonic debridement in the whole surgical area at a frequency of (25±5)kHz and power of 90% for 5 minutes. Each ultrasound lasted 10 seconds with 3-second intervals. The probe was repeatedly sonicated among all soft tissue,bone interface and metal prosthesis surface(patients underwent debridement,antibiotics and implant retention (DAIR)) in the surgical area. The femoral canal of the hip joint,the distal femoral canal and the posterior capsule of the knee were fully sonicated with a special right-angle probe. Before and after ultrasonic debridement,20 ml of liquid was extracted from each operation area and injected into aerobic and anaerobic culture bottles,respectively,for pathogen culture. Harris hip score and Hospital for Special Surgery (HSS) score were used to evaluate clinical function. Treatment failure was defined as the recurrence of infection in the same joint. The patients were routinely followed up in the outpatient clinic at 1,3,and 6 months postoperatively and then annually with a deadline of August 2022. The paired t-test,rank sum,Mann-Whitney U or χ2 test was used to compare the observed data,and rates among multiple groups were compared using the Bonferroni approach. Results: A total of 45 patients were included in the study,including 21 men and 24 women with age of (65.8±15.2)years(range: 20 to 80 years) and body mass index of (29.3±4.2)kg/m2(range: 20.2 to 38.5 kg/m2). Twenty-eight patients (18 hips and 10 knees) underwent one-stage revision,and 17 cases (5 hips and 12 knees) underwent DAIR. Three of the patients (6.7%) had recurrent infections during follow-up. There were no intraoperative complications related to ultrasonic debridement (neurovascular and muscle injury,poor wound healing and fat liquefaction). Seventeen patients who received DAIR were followed for a median(M(IQR)) of 9(3) months,and two relapsed 3 weeks and 3 months post-operation,respectively. In addition,28 patients who underwent one-stage revision were followed for a median of 9(2) months,and one of the patients (3.6%,1/28) had a recurrence 6 months post-operation. The culture-positive rate of preoperative aspiration was 47.6% (20/42). The data of intraoperative soft tissue culture was 86.7% (39/45). The culture-positive rate of wound liquid before ultrasonic debridement was 46.7% (21/45). And the culture-positive rate after ultrasonic debridement was (75.6% (34/45)). After sonication,the culture-positive rate of explanted prostheses was 88.9% (40/45). There was a significant difference in culture-positive rates among all five cultures (χ2=35.483,P<0.01). Further pairwise comparison showed that the culture-positive rate of wound liquid after ultrasonic debridement was higher than that before ultrasonic debridement (χ2=7.901,P=0.005) but was not significantly different from the positive rates of other cultures (all P>0.05). The median number of colonies 24 hours after ultrasonic debridement(2 240 (1 310) CFU/ml,range: 310 to 3 140 CFU/ml) was significantly higher than that before debridement(450 (550) CFU/ml,range: 10 to 910 CFU/ml) (U=43, P=0.017). The post-operative Harris ((78.6±4.2)points,range:70.5 to 85.3 points) and HSS scores((76.4±4.8)points,range: 68.5 to 84.3 points) were significantly higher than the preoperative scores((46.0±9.8)points,range: 27.5 to 64.3 points;and (45.5±10.3)points,range: 27.6 to 63.1 points) (t=-14.6,t=-12.7;both P<0.01). Conclusions: Non-contact low-frequency ultrasonic debridement can increase the culture-positive rate and lead to a favorable short-term outcome. In addition,no complications are associated with using this new technique to treat PJI.