Effective Management of Methicillin-Resistant Shoulder Septic Arthritis Using Continuous Local Antibiotic Perfusion: A Case Study and Long-Term Follow-Up

Introduction

According to reports, 4–10 persons out of every 100 000 develop septic arthritis each year, with some areas experiencing higher incidences of up to 29 cases per 100 000 individuals, and the number is increasing annually [1]. Septic arthritis of the shoulder is rare compared to that of the knee and hip joints, accounting for 5–12% of all cases of septic arthritis [2,3]. Delayed or inadequate treatment may result in joint destruction and a fatality rate of approximately 11%. Furthermore, if the infection spreads to multiple joints, the fatality rate reaches approximately 50% [4]. Given the important role the shoulder joint plays in daily activities, inappropriate treatment of septic arthritis may lead to considerable functional impairment and a high mortality rate [5].

Septic arthritis of the shoulder requires early diagnosis and treatment. Invasive treatment within 2 weeks of onset of the infection has yielded favorable results [6]. Effective treatment methods include intravenous administration of antibiotics, curettage of localized foci of infection, and debridement and drainage [7]. However, it often becomes refractory in high-risk cases, such as in diabetes mellitus, in patients on long-term dialysis, and in cases caused by antibiotic-resistant bacteria. Recently, the efficacy of continuous local antibiotic perfusion (CLAP) for bone and soft tissue infections has been reported [8–14]. In this study, we present a case of a patient undergoing long-term hemodialysis for congenital anomalies of the kidney and urinary tract who developed methicillin-resistant coagulase-negative Staphylococcus epidermidis (MRCNS)-induced septic arthritis of the shoulder and the infection subsided after CLAP following arthroscopic debridement.

Case Report

INTRAOPERATIVE FINDINGS:

Immediately after the diagnosis, we performed irrigation and debridement of the joint using an arthroscope. Intraoperative findings revealed hemorrhage in both the glenohumeral joint and subacromial bursa, with marked hyperplasia and degeneration of the synovial membrane. For abscesses outside the joint, irrigation and debridement were performed under direct vision. After adequate irrigation and debridement, double-lumen drain with an anti-reflux valve (18Fr, 2 tubes in total) was placed for CLAP to allow for intra- and extra-articular antibiotic injection and drainage. A drain tube was inserted into the joint from the anterior portal made with skin incision for arthroscopic surgery. Also, due to the accumulation of an abscess from lateral to posterior of the humerus, the lateral deltoid muscle was split, and the other drain tube was placed at the posterior of the humerus (Figure 3). It has been reported that a minimal biofilm eradication concentration (MBEC), which is 100–1000 times the minimal inhibitory concentration (MIC), is needed to eradicate biofilms formed by bacteria [15]. Using CLAP, 2 mg/mL of aminoglycoside gentamicin, which is 1000 times the minimal inhibitory concentration (MIC <2 µg/mL), was administered at 2 mL/h. The risk of adverse effects, such as renal disorder and eighth cranial nerve disorder, increases when the minimum blood concentration of gentamicin exceeds 2 µg/mL. Also, it has recently been reported that the administration of high-concentration gentamicin affects the function of bone tissue-derived cells, although this was an in vitro study [16]. For these reasons, we performed therapeutic drug monitoring (TDM) after starting the administration of gentamicin, and the dosage was adjusted to maintain the blood concentration below 2 µg/mL. Vancomycin, which is sensitive to the bacterium, was intravenously administered systemically. The administration of vancomycin was initiated at 1 g/day, followed by alternate-day administration of 0.5 g. Thereafter, the dosage was adjusted while performing TDM of vancomycin.

POSTOPERATIVE COURSE:

Among the 10 cases of septic arthritis of the shoulder with open drainage treated at our hospital (Table 1), remission was achieved in 9 cases. However, in 1 patient who was undergoing long-term dialysis and underwent reoperation, a relapse of septic arthritis of the shoulder caused by methicillin-resistant Staphylococcus aureus (MRSA) occurred. Therefore, CLAP was administered to this patient, who was at high risk of recurrence. Approximately 3 weeks after surgery, the CRP level decreased to 0.26 mg/dl. Thereafter, CLAP was discontinued 4 weeks after the operation because the blood CRP level was maintained at ≤0.3 mg/dL, and oral antibiotics (sulfamethoxazole trimethoprim) were subsequently administered 5 weeks after the operation. Infectious symptoms disappeared after CLAP, and bacterial culture was negative. There were no recurrent symptoms during follow-up and no complications such as acute renal failure, ototoxicity, or allergic or hypersensitivity reactions. In this case, no bone destruction was observed and there was no relapse 2 years after the infection subsided. Moreover, although the patient originally had a rotator cuff tear, no remarkable limitations on the range of motion were oserved. Therefore, the range of motion returned to that before the onset of infection, and there were no impediments to activities of daily life.

Discussion

In patients with septic arthritis of the shoulder, intravenously administered antibiotics are not easily transferred to the focus of infection due to poor blood flow at the focus. Furthermore, bacteria in the focus of bone infections tend to form biofilms, and it is particularly difficult for antibiotics to reach the bacteria that grow in the focus. CLAP can continuously inject and perfuse antibiotics directly into the focus, making it possible to locally transfer high concentrations of antibiotics that are effective in suppressing biofilms [13,14]. The present case was a compromised host with an MRCNS infection, indicating a high possibility of infection recurrence. However, the disease subsided as a result of irrigation debridement and CLAP, with no recurrence for at least 2 years after the surgery.

Early diagnosis and treatment are crucial in septic arthritis. In this case, the patient had a rotator cuff tear, and was a compromised host with localized swelling and fluid accumulation. Therefore, puncture was performed as soon as possible, and MRCNS was observed in the aspirate culture, enabling early diagnosis. Septic arthritis of the shoulder is often associated with a rotator cuff tear. Therefore, vigilance is required because the infection may be overlooked as a symptom associated with a rotator cuff tear, particularly if the infection is mild [17]. In addition to visual inspection and palpation, when joint fluid accumulation is observed, it is necessary to perform joint fluid tests in addition to blood tests.

Treatment of septic arthritis is based on early debridement of the infected focus and intravenous administration of antibiotics [3,6,18,19]. In recent years, although arthroscopic surgery has been reported [20], both direct arthrotomy and arthroscopic surgery have been reported to achieve favorable results [7,21]. There is currently no consensus regarding which treatment method is better [18]. Postoperative drainage methods include continuous perfusion, closed drainage, and open drainage using a Penrose drain. Of these, open drainage after arthroscopic irrigation debridement has been reported to have a favorable functional prognosis because of the advantage that rehabilitation can be started from the early postoperative period [22]. However, when the infection is caused by an antibiotic-resistant bacterium such as MRSA, the recurrence rate of infection is high, with approximately 60% being considered refractory [23].

In recent years, CLAP demonstrated efficacy against infected foci and can also be effective against resistant bacteria when high concentrations of antibacterial agents are administered. Furthermore, high-concentration antibiotics at 100–1000 times the MIC are required to eliminate bacteria within biofilms [15]. For injectable antibiotics, genes for aminoglycoside-inactivating enzymes have been identified [24]. It is recommended to select a high concentration of aminoglycosides because it can suppress infection regardless of drug susceptibility by achieving localized concentrations that exceed the resistance function of the inactivating enzyme [13]. Similarly, the use of high-concentration gentamicin, an aminoglycoside antibiotic, in this case, resulted in early remission of the infection.

Currently, open drainage after irrigation and debridement of the lesion is performed for septic arthritis. Open drainage is believed to reduce functional impairment because it facilitates early initiation of rehabilitation [22]. On the other hand, for CLAP, which was performed in the current case, range of motion training was not performed for a while after surgery. In septic arthritis of the shoulder complicated with a rotator cuff tear, as in this case, strong functional impairment may remain after the infection subsides because of the spread of infection to surrounding tissues, degeneration and functional decline, as well as the expansion of rupture area due to combined debridement [2]. However, in the current case, the infection subsided soon after CLAP. Subsequent rehabilitation proceeded smoothly; hence, no serious functional impairments remained, and no impediments to activities of daily life persisted 2 years after the surgery.

Conclusions

CLAP may be considered as an effective therapeutic option for septic arthritis of the shoulder that can alleviate the infection at an early stage, enable early rehabilitation, and thereby reduce the risk of functional deficits.