Recalcitrant Periprosthetic Joint Infection With Iliac Fossa Abscess After Total Hip Arthroplasty


 Background: Total hip arthroplasty (THA) is a widely used and successfully performed orthopedic procedure for treating severe hip osteoarthritis, rheumatoid arthritis, and avascular necrosis. However, periprosthetic joint infection (PJI) after THA is a devastating complication for patients and orthopedic surgeons. Although surgical technology has been advanced and antibiotic-loaded cemented spacers or beads have developed, the treatment failure rate of one- or two-stage exchange arthroplasty for PJI is reported to be high, with >10% rate of incidence. Therefore, determining the possible pathogenesis and increasing the treatment success rate is a clinically important and urgent issue. Methods: A total of 256 patients with PJI who had undergone THA from 2005 to 2015 were included in this retrospective review. Seven patients required combined ilioinguinal and anterlateoal approach for debridement of iliac fossa abscess and infected hip lesion, included five patients with intraoperative pus leakage from the acetabular inner wall and the other two patients who underwent pre-operative pelvic computed tomography (CT) because of repeat PJI treatment failure. All available data from the medical records from all patients were retrospectively analyzed.Results: Of the 256 patients, seven (3.1%) patients was combined iliac fossa abscess in our cohort. For the microbiologic analysis, a total of thirteen pathogens were isolated from seven recurrent PJI patients with iliac fossa abscess, and Staphylococus aureus was the most commomly pathogen (4 out of 7 cases). The serum white blood cell (WBC) count was decreased significantly two weeks after debridement with combined the ilioinguinal and anterolateral approach compared to the day before surgery (11840/μL vs. 7370/μL; p<0.01), and level of C-reactive protein (CRP) was decreased at postoperative one week (107 mg/dL vs. 47.31 mg/dL; p=0.03). Furthermore, no recurrent infection was found in six revision THA patient in a follow up of 7.1 year. Conclusion: This result suggests that pre-operative pelvic CT and cautious identification of uncertain pus leakage from the inner wall of the acetabulum is essential for the diagnosis of recurrent PJI. Radical debridement with combined ilioinguinal and anterlateoal approach may aviod treatment failure in recurrent PJI with iliac fossa abscess.


Background
Total hip arthroplasty (THA) is one of the most frequently performed adult orthopedic procedures, with nearly one million patients undergoing THA annually [1]. The number of THAs performed annually is increasing [2]. A statistical report revealed that 332,000 THAs were performed in the United States in 2010 [3], and it was predicted that this number will increase to 527,000 (137%) by 2030 [2]. In addition, a recent study suggested that patients undergoing THA have a higher survival rate (10 years after surgery) than the general population [4]. This implies that the expected lifespan of patients with THA is increasing.
However, periprosthetic joint infection (PJI) in THA patients is a devastating complication that has challenged patients, orthopedists, and the global health care industry because an increasing number of THA procedures are being performed [3,[5][6][7]. The incidence of PJIs after primary THA is 0.5-3% and after revision joint arthroplasty is 4-6% [8].
Generally, several clinical treatment strategies are applied-radical debridement with retention of the implant and long-term antibiotic administration, exchange arthroplasty, which includes one-or two-stage (immediate or delayed) revisions, and excision arthroplasty [9,10]. The treatment failure rate for PJI at follow-up has been reported to be high (one-or two-stage surgical treatment: >10% and surgical debridement: 30-50%) [11][12][13][14][15][16]. The two-stage surgical method has a better success rate (91%) than the one-stage (82%) [17]. Although several novel therapeutic methods and agents have been suggested, the pathogenesis and > 10% incidence of recurrent PJI are unclear and di cult to overcome. Hence, reducing the treatment failure rate of PJI is a concern and urgent requirement to be resolved. Hence, this retrospective study evaluated the incidence and management of PJIs with iliac fossa abscess to aviod treatment failure.

Hospital setting
This study was conducted at the Chang Gung Memorial Hospital in Taiwan and was approved by the Institutional Review Board (IRB number: 201900832B0) and Ethics Committee.

De nitions of PJI
All patients were diagnosed with PJI based on the Musculoskeletal Infection Society (MSIS) criteria and McPherson staging system [18,19]. A diagnosis of PJI was made if at least one of followed criteria was ful lled: (1) presence of sinus tract communication with the prosthesis, (2) a pathogen was isolated from the culture of at least two separate tissue or uid samples obtained from the affected prosthetic joint, repeat PJIs. The mean age of these seven patients was 67 years (range: 42-83 years) and the mean follow-up period was 7.1 years (range: 3-13 years).

Measurement of biomarkers
The levels of white blood cell (WBC) count, CRP, and ESR were measured before and one week, two weeks, and 4 weeks after debridement with combined the ilioinguinal and anterolateral approach.

Statistical analysis
All data were analyzed using one-way analysis of variance, and a Tukey post hoc test was performed for multiple comparisons (p < 0.05). All statistical calculations were performed using GraphPad Prism version 7.0 (GraphPad Software Inc., San Diego, CA), and all values were reported as mean ± standard deviation.

Results
In our study population, the incidence of PJIs combined with iliac fossa abscess was 3.1% (7/256). The mean number of repeated debridements performed in PJI patients with iliac fossa abscess was 4.8 (range, 1-13 times). Accroding to the medical records, the numbers of male and woman PJI patients with iliac fossa abscess were 4 (57%) and 3 (43%), respectively, and these patients had average age was 67 years (range from 42 to 83). Comparison of Musculoskeletal Infection Society (MSIS) classi cation, there was no signi cant difference between PJI patients and PJI patients with iliac fossa abscess. (Table 1)

MSIS, Musculoskeletal Infection Society
A total of thirteen pathogens were isolated from seven recurrent PJI patients with iliac fossa abscess in the microbiologic ndings, and Staphylococus aureus was the most commomly pathogen. (4 out of 7 cases ,57%). Particulaly, we noticed that diabetes mellitus (DM) was most occurred in PJI patients with iliac fossa abscess (2 out of 7 cases), and other comorbidity disease was occurred in one case, including chronic hepatitis and cirrhosis and cancer. Our data showed no signi cant linkage in these patients with regard to sex, age, hip location and underlying comorbidity ( Table 2). Figure 1 and Fig. 2 showed preoperative pelvic CT images of patients with recurrent PJI and iliac fossa abscess, and operative wound had healed well two weeks after the combied ilioinguinal incision procedure. However, no signi cant difference was found in mean ESR level over time (Fig. 3). A notable decrease in the level of PJI biomarkers indicates that the infection is controlled. Six of seven patients were shifted to revision total hip replacement after infection was controlled. One patient denied the revision operation because of personal reasons. At end of follow up, no recurrent PJI was found in this study group.

Discussion
PJIs are an important medical challenge, considering the number of THAs and lifetime spent on treatment are increasing [2][3][4][5]. Several risk factors that have been indicated to be associated with the development of PJI are high body mass index (BMI; >30), diabetes mellitus, rheumatoid arthritis, revision surgery, tobacco or steroid use, methicillin-resistant Staphylococcus aureus colonization, infection, and history of bone cancer [20]. Furthermore, PJI is the key factor of mortality and morbidity of THA patients [21]. The major characteristic of PJI pathogenesis is that it is associated with the bacterial invasion of the surface of prosthetic implants and production of bio lms [22]. The bio lm formation could create a barrier against the antibiotic effects and subsequently, increase the treatment failure rate. However, although the knowledge regarding metabolic processes and bacterial communication in bio lms have been improved recently [23], successful PJI eradication PJI through revision surgery in the clinic remains poor and requirement improvement. Several enhanced methods and novel agents such as antibiotic combination therapy, antibiotic delivery through nanoparticles, photodynamic therapy, and nanoparticles with bactericidal effects have been suggested for treating PJI to increase the treatment success rate [24].
However, some di ucult treatment of PJIs may not be due to the bio lm formation or antibiotic-resistant bacterial strain colonization. The other risk factors associated with treatment failure of PJI include longer duration of symptoms prior to treatment with debridement, the soft tissue intergrity and Staphylococcus aureus infection [25][26][27]. In the current study, we provided an another possible reason-a non-visible abscess in the iliac fossa or pyomyositis during debridement in acetabular wall. In our study, 3.1% of patients developed PJI with iliac fossa abscess or iliacus muscle pyomyositis. In addition, we provided a treatment strategy for patients with PJI and iliac fossa abscess or iliacus muscle pyomyositis. The combination of two approaches included the ilioinguinal and anterolateral incision for debridement is necessary to eradicate iliac fossa pus and infected tissue. Through the two approaches debridement, the values of infection biomarkers were reduced and also indicated that the prognosis of patients was signi cantly improved. Furthermore, no recurrent infection was found in six revision THA patient in a follow up of 7.1 year. In this retrospective review, Staphylococus aureus was the most commomly pathogen isolated from recurrent PJI patients with iliac fossa abscess (4 out of 7 cases). Our funding support the conclusion of previous studies that Staphylococcus aureus infection was the major clinical risk for treatment failure [26]. Moreover, The presence of liver disease had been associated with the development of PJIs failure treatment in previous study. But only one case with chronic hepatitis and cirrhosis was found in our study and no signi cant linkage was showed in PJI patients with iliac fossa abscess. There were other comorbidity factors for PJI treatment failure, including history of myocardial infarction, presence of sinus tract, smoking and obesity [28][29][30]. However, our study did not nd these risk factors in PJI patients with iliac fossa abscess.
We acknowledge that our study has some limitations. First because this was a retrospective study, the occurrence time and source of iliac fossa abscess or pyomyositis are not fully con rmed. Second, all patients did not undergo pre-operative pelvic CT examination. Third, our study population was small.

Conclusion
This study intended to provide a possible pathogenesis of recurrent PJI. The iliac fossa abscess or pyomyositis in patients with PJI may be ignored during the surgical procedure because they are not visible or di cult to nd. However, undestroyed abscess in the iliac fossa or pyomyositis are risk factors for reinduction of PJI. Hence, we strongly recommend that pre-operative pelvic CT should be performed for the diagnosis iliac fossa abscess or pyomyositis in patients with recurrent PJI and further, suggest that ilioinguinal incision should be performed for the removal of intrapelvic abscess.

Declarations
Ethics approval This study was conducted at the Chang Gung Memorial Hospital of Taiwan and was approved by the Institutional Review Board of Chang Gung Medical Foundation (IRB number: 201900832B0). All methods were carried out in accordance with relevant guidelines and regulations, and the requirement for informed consent was waived due to this a retrospective study by the Institutional Review Board of Chang Gung Medical Foundation.

Consent for publication
Not applicable Availability of data and materials All data and materials supporting the conclusions of this article are contained within the manuscript.

Competing interests
The authors declare that they have no competing interests.
Author's contribution