This study aimed to verify the hypothesis that an antibiotic loaded hydrogel, defensive antimicrobial coating (DAC), reduces overall complication and infection rates when used for high-risk primary and revision total hip arthroplasty (THA).

This was a retrospective study matched cohort study of 238 patients, treated with cementless implants with and without DAC. A sub-group analysis of patients undergoing 2nd stage revision THA for prosthetic joint infection (PJI) was also conducted. Re-infection rates within 2 years, complications necessitating surgical intervention and radiographic analysis for aseptic loosening was assessed.

The mean age was 68.3±11.5 years, with 39 (32.8%) Macpherson class A, 64 (53.8%) class B and 16 (13.4%) class C patients. 4 (3.4%) patients in the DAC group developed complications including 1 PJI and 1 delayed wound healing, while 13 (10.9%) patients in the control group developed complications including 5 PJIs and 3 delayed wound healing (p=0.032). PJI rates (p=0.136) and delayed wound healing rates (p=0.337) were not statistically significant. For 2nd stage revision THA for PJI there were 86 patients in the DAC group and 45 in the control group. 1 (1.2%) patient in the DAC group developed complications with no recurrences of infection or delayed wound healing, while 10 (22.2%) patients in the control group developed complications including 4 recurrent PJI and 1 delayed wound healing (p=0.003). Recurrent PJI rates were statistically significant (p=0.005) while delayed wound healing rates were not (p=0.165). Patients treated with DAC also had lower rates of aseptic loosening (0% vs 6.7%; p=0.015).

Antibiotic impregnated hydrogel coatings on cementless implants showed decreased complication rates after complex primary or revision THA. In 2nd stage revision THA for PJI, it was associated with reduced risk of re-infection and aseptic loosening.

Stem loosening can be associated with a wide spectrum of bone loss and deformity that represent key factors for choosing the most appropriate revision implant. The aim of this study was to evaluate the clinical outcomes and the survivorship of a consecutive series of THA revisions using a taper rectangular cementless stem for primary implants (Alloclassic® Zweymuller®, Zimmer Warsaw US) at medium-term follow-up.

We retrospectively evaluated 113 patients (115 revisions) who underwent femoral revision with Zweymuller stem with a preoperative Paprosky I (86) or II (29) defects from January 2011 to December 2020. The mean follow up was 6 years (2–10). The median age at time of surgery was 71(41–93) with 60 males and 53 females. Osteolysis/radiolucency were observed in the following Gruen zones: I (91), II (3), III (2), VII (15), V (3), VI (1). Clinical assessment was performed by means of Harris Hip Score (HHS) and Visual Analogic Scale (VAS), whereas for the radiological analysis we used conventional x-rays of the hips. The statistical analysis was performed using Graphpad Prism v5.0 and data distribution was assessed by Shapiro-Wilk test, and Wilcoxon matched paired test was used to test the differences between preoperative and postoperative score.

9 patients were lost to fu (deceased or not available), 104 (106 hips) were evaluated. The mean HHS and VAS significantly improved at final follow-up, going from 33,84 and 5,78 preoperatively to 66,42 and 2,05 postoperatively, respectively. 28 patients (25%) showed unprogressive radiolucent lines in Gruen zones 1 and 7 with no other radiological nor clinical signs of loosening. One patient suffered from recurrence of the infection. The survivorship with stem revision as endpoint was 100%.

Alloclassic Zweymüller primary stem showed good medium-term results and survival rate in revision THA for aseptic loosening and second stages of two stage revisions.

Aims

Leucocyte esterase (LE) has been shown to be an accurate marker of prosthetic joint infection (PJI), and has been proposed as an alternative to frozen section (FS) histology for intraoperative diagnosis. In this study, the intraoperative assessment of LE was compared with FS histology for the diagnosis of prosthetic hip infection.

Leukocyte esterase (LE) has shown to be an accurate marker of prosthetic joint infections and has been proposed as an alternative to frozen section (FS) for intra-operative diagnosis. In this study, intra-operative determination of LE was compared with FS for the diagnosis of periprosthetic hip infections.

One hundred and nineteen patients undergoing hip revision surgery due to prosthetic joint failure from June 2015 to December 2017 were considered. Joint fluids were collected before the arthrotomy for determination of LE which was performed by using enzymatic colorimetric strips. Four to six samples were stained with hematoxylin eosin for FS and considered suggestive for infection when at least 5 polymorphonuclear leukocytes in 5 fields at high power fields were found.

Sensitivity and specificity of LE were 100% and 93.8 %, respectively. The positive predictive value was 79.3 %, while the negative predictive value was 100%. Time from collection to response was 20.1 ± 4.4 minutes.

Sensitivity and specificity of FS were 83.3 % and 92.1 %, respectively. The positive and negative predictive values were 84.6 % and 97.1%. Time from sample collection response was 27.2 ± 6.9 minutes.

LE showed a higher sensitivity and a slightly lower specificity and the same diagnostic accuracy of intraoperative FS. The faster turnaround time (about 20 minutes from receiving of sample by the laboratory), its ease of use and the low costs make this test a valuable alternative to frozen sections and is going to replace FS in our clinical practice.

Previous studies showed that a fast-resorbable antibacterial hydrogel coating (DAC®, Novagenit Srl, Mezzolombardo, TN, Italy) composed of covalently linked hyaluronan and poly-D, L-lactide, is able to reduce early post-surgical infection both after joint replacement and osteosynthesis. Aim of the present report is to investigate medium-term safety and efficacy of the coating in patients undergoing primary and revision cementless total hip replacement (THR).

We designed a two-phases study. In both phases, DAC was prepared according to manufacturer's instructions. In brief, the syringe prefilled with 300 mg of sterile DAC powder was mixed, at the time of surgery, with a solution of 5 mL of sterile water and with the tailored antibiotics, at a concentration ranging from 25 mg/mL to 50 mg/mL. The resulting antibacterial hydrogel was then spread on the outer surface of the prosthesis just before implantation.

In the first phase, safety was assessed. Forty-six patients (13 primary and 33 revision THR) were treated with DAC between 2013 and 2015 and evaluated at a 2.8 ± 0.7 years follow up (FU). Antibiotics used for DAC reconstruction were Vancomycin in 33 cases, Vancomycin + Meropenem in 10, Vancomycin + Rifampicin, Teicoplanin or Ceftazidime in 1 case, respectively. Patients were evaluated at 3, 6, 12 months and yearly after with a clinical and radiographic FU. No evidence of infection and no failure/loosening of the prosthesis were observed. No adverse events were reported.

The second phase was designed to evaluate efficacy of DAC in preventing infection recurrences after a two stage revision for infected THR. Twenty-seven patients, treated with DAC coating, were compared with a control group of 32, treated in the same time period, without the coating. Demographics, host type and and identified bacteria were similar in the two groups (18.6% of MRSA in DAC group vs 18.5% MRSA in no-DAC group). Patients were evaluated clinically and radiographically at 3, 6, 12 months and yearly thereafter. At a minimum 2 years FU (mean 2.7), we observed 1 dislocation in each group and 2 cases of loosening in the no-DAC group. 4 cases (11%) of recurrence of infection in the no-DAC group (1 MRSA and 3 St. Epidermidis) and no infection recurrences in the DAC group. Due to the small cohort of patients this difference is not statistically significant (Fisher's exact test, p=0.18).

This is, to our knowledge, the longest observation concerning the safety and efficacy of the DAC antibacterial coating, applied to hip replacement. The results are in line with those previously reported and point out the absence of side effects of the antibacterial coating in this application and the tendency to reduce re-infection in second stage. This finding needs to be confirmed by a larger dataset.

Reliability of microbiological diagnosis of prosthetic joint infection [PJI] strongly depends on the ability to dislodge microorganisms from biofilm and on the rate of contaminating samples during collection in the operating room and processing. The aim of a correct protocol is to avoid false negative and false positive results in order to adapt the correct therapy for each patient.

The object of the present study was to evaluate the impact of a novel closed bag system designed for samples collection and processing based on dithiothreitol (DTT), which is a sulfydryl compound able to remove bacteria from biofilm (MicroDTTect, 4i, Italy), on isolation of contaminant microorganisms in hip prostheses.

Specimens (prostheses, spacers, periprosthetic tissues) were aseptically collected according to a standard protocol into the device, which was transported to the laboratory for culture. Three different models of the system were prospectively evaluated, each being a development of the previous one. The first generation device consisted in an “open” system (DTT eluate was collected with a syringe and dispensed into sterile tubes), the second generation device in a “partially closed” system (DTT eluate collected directly in sterile vacuum tubes) and the third generation device in a “completely closed system” (DTT reservoir directly connected with sealed tubes inside the device). PJI was diagnosed following criteria established by MSIS.

The overall contamination rate, sensitivity and specificity of the first generation “open” system MicroDTTect were respectively 2.6% (1/39), 82.3% and 95.4% in 39 hips. The second generation “partially closed” device was characterized by a contamination rate of 1.96% (1/51), a sensitivity of 84% and a specificity of 96.1% in 51 hips. Contamination rate further decreased in the third generation “closed” system (1.89%, 2/106), while sensitivity (91.3%) and specificity (96.7%) improved in 106 hips. Differences have been also observed in hips (106) when compared to knees (70 cases) prosthetic infections (sensitivity 91.3% vs 89.3% and specificity 96.7% vs 100%).

Our data show as, thanks to its ease of use, low contamination rate and high sensitivity, MicroDTTect can represent a useful tool for improving the microbiological diagnosis of PJIs in hip revisions and has replaced sonication in our practice.