The clinical presentation of PSI is generally nonspecific and the most frequent symptom to be presented is that of pain, whereas other clinical signs of infection may be lacking. The existence of a sinus tract that connects with the prosthesis is definitive proof of PSI (Fig. 1). Another local sign that may be found is erythema, while systemic symptoms (fever, chills) are less common [19]. The Infectious Diseases Society of America recommend considering a periprosthetic infection in presence of “an acute onset of a painful prosthesis, or any chronic painful prosthesis at any time after prosthesis implantation, especially when there are no pain-free periods, in the first few years following implantation or if there is a history of prior wound healing problems” [27]. Treatment using nonsteroidal anti-inflammatory medications and oral antibiotics can impede a correct diagnosis [19].

Fig. (1). A draining sinus tract in the medial aspect of the deltopectoral surgical incision.

Laboratory tests, including analyisis of the C-reactive protein (CRP) level, erythrocyte sedimentation rate (ESR), and white bloodcell count (WBC) are significant signs of infection [16,17]. The WBC count in a deep infection is seldom abnormal, while the ESR and CRP level are frequently elevated [7,19,28]. Nevertheless, the ESR and CRP level are aspecific markers of inflammation and could be unremarkable in cases of Propionibacterium acnes infection [21]. Moreover, both markers are normally higher following an uncomplicated surgical operation. The ESR will fall gradually, while the CRP level will diminish faster, typically returning to normal levels inside two weeks after a routine operation. Topolski et al. [15] described the value of pre-operative studies and intra-operative histology in patients who underwent revision shoulder replacement and had positive intraoperative cultures. In a series of 75 shoulders without obvious signs of infection undergoing revision, the pre-operative WBC count was normal in 67 of 72, with normal polymorphonuclear cell distributions and a normal ESR in most patients. Among the 16 patients who had a CRP measured, it was normal in 12. The intra-operative histology showed no signs of acute inflammation in 67 of 73 patients. The authors concluded that there were no reliable intra- or pre-operative studies to forecast who was likely to have a positive intra-operative culture.

With early infection, radiographic findings are typically normal. In contrast, radiographs may provide important clues in subacute and chronic infections. Lucent lines, which develop within a few months, strongly signal an infection (Fig. 2). Other subtle radiological findings include the presence of medial calcar erosion and resorption of the tuberosities. Ultrasonography may be useful identifying localized fluid accumulation as some PSI could present with fluid collections which can be traced to remote locations from the glenohumeral joint [29]. Technetium Tc-99 bone scans and indium In-111–labeled white blood cell scintigraphy should be taken into account when the diagnosis of PSI continues to be in doubt. (Fig. 3) [7].

Fig. (2). Radiograph of a shoulder 1 year after hemiarthroplasty. Note a lucent periprosthetic line at the bone-prosthesis interface with signs of loosening.

Fig. (3). Labeled leukocyte scintigraphy revealing an increased uptake localized in the proximal periprosthetic zone of the humerus.

All patients with a suspected PSI should have a diagnostic arthrocentesis carried out except where the disgnosis is clinically obvious and surgery is planned. It is recommended that a synovial fluid analysis contains a total cell count and differential leukoyte count, along with culture for aerobic and anerobic organisms. A white blood cell count of >50,000 cells/mm3 with more than 75% polymorphonuclear cells or even direct germ visualization are suggestive of infection. Withholding antibiotic treatment for a minimum of two weeks before the arthrocentesis enhances the chances of retrieving an organism. Intraoperative histopathological examination of periprosthetic tissue samples is a well proven diagnostic test provided that a skilled pathologist specialized in the evaluation of periposthetic tissue is to hand. It should be carried out during the surgery, if the presence of infection is in question, based on the clinical judgement of the surgeon and the results will determine the choice of treatment. A minimum of four periprosthetic intraoperative tissue samples of the explanted prosthesis should be sent for aerobic and anaerobic culture during the surgery in order to increase the possibility of getting a microbiologic diagnosis: two specimens from the joint capsule, one from the prosthesis-bone interface and another from the medulary canal. More than five polymorphonuclear leukoytes per high-powered field signify infection when they are found in a minimum of two tissue specimens.. Withholding antibiotic treatment for a minimum of 2 weeks before collecting intraoperative culture enhances the chances of retrieving an organism. For the same reason, perioperative antibiotics should be withheld until tissue samples are obtained [27]. Implant sonication is a recent technique that involves the removal of the prosthesis and putting it into a solid container which is then vortexed and sonicated. The technique can be used to identify germs in the biofilm clinging to the prosthesis. Implant sonication has proven to be more sensitive than intraoperative tissue specimens for identification of bacteria, especially Propionibacterium acnes: although the test has yet to obtain extensive acceptance [30].

Antibiotic therapy was demonstrated to be ineffective in the management of PSI, confirming the results of antibiotic suppression for periprosthetic knee infections. Failure rates of 60% to 75% have been reported with this treatment modality [7,31]. Antibiotic treatment alone should only be contemplated for seriously ill patients or those who refuse to have surgery. [19].

Retention of a shoulder prosthesis can be feasible when an infection is identified acutely (after less than 30 days from implantation or after less than three weeks from the start of infectious symptoms), the implant is stable, the isolated germ is of low virulence, and complete debridement has been achieved [19]. In selected cases, debridement may also be performed arthroscopically [32]. However, Sperling et al. [13] reported a 50% failure rate with this treatment and Romanò et al. [20] in a multicentric study reported less satisfactory results with debridement in terms of infection eradication rate compared to the other treatments. Coste et al. [7] have carried out a retrospective review of 49 cases of PSI and concluded that antibiotics or debridement alone were not effective. They suggested to treat acute PSI with aggressive debridement and exchange of the implant associated with an appropriate intravenous antibiotic therapy.

Formed mainly from the experiences gained in hip and knee surgery, one-stage prosthesis exchange is not as popular as two-stage prosthesis exchange. Sperling et al. [13] reported failure in one of two shoulders treated for subacute PSI with direct prosthesis exchange. On the contrary, Coste et al. [7] detected improvement in Constant scores and no recurrence of infection, in 3 patients treated with one-stage prosthesis exchange. Ince et al. [33] also reported no recurrence of infection in 16 patients managed with one-stage revision using an antibiotic-impregnated cement. Despite the fact that two-stage exchange is generally regarded as the gold standard, Cuff et al. [34] in a retrospective analysis of 22 cases reported that, as regards outcome and the eradication of infection, a single-stage revision was statistically no different from a two-stage procedure. The one-stage reimplantation guarantees better functional outcome but carries a higher risk of infection recurrence. Other benefits of one-stage exchange over a two-stage exchange involve lower cost and the requirement for only one procedure. Nontheless, failure to eradicate the infection during the one-stage reimplantation, will require additional procedures. More investigation is needed to establish guidelines and identify the appropriate conditions for using a one-stage exchange [19].

Two-stage exchange involves removal of the infected implant, extensive debridement of periprosthetic tissues, placement of a temporary antibiotic spacer (Fig. 5a-c) and antibiotic treatment prior to reimplantation of new prosthetic components. Different authors have suggested to discontinue antibiotics and monitorize the level of CRP and ESR prior to going ahead with revision surgery [19]. One-stage and two-stage reimplantation show high rates of infection control, although the most reproducible results have been gotten from two-stage revision surgery [8,26]. Moreover, the two-stage reimplantation appears to be able to compromise the best between dependable eradication of the infection and functionality after surgery. Sperling et al. [13] examined 32 PSI cases: group I (21 cases) underwent resection arthroplasty; group II (6 cases), underwent debridement and retention of the implant; group III (2 cases) was treated with one-stage exchange; and group IV (3 cases), with two-stage exchange. Reinfection occurred in 6 patients treated with resection arthroplasty, in 3 patients with the retained implant, in 1 patient treated with one-stage reimplantation, and in none of the patients treated with two-stage reimplantation. At the time of final follow-up, the authors concluded that two-stage exchange gives the best results in terms of eradication of infection, pain relief, and shoulder function, particularly if compared to resection arthroplasty. Sabesan et al. [26] also reported a low recurrence rate after a two-stage reimplantation procedure associated with a substantial improvement in function and pain. Strickland et al. [35] describes less successful outcomes with two-stage exchange. In their group of 19 patients, the eradication of infection was obtained in only 63% of cases (12), and in 13 cases the outcomes were unsatisfactory. Antibiotic-impregnated cement spacers have proven to be of use in staged reimplantation [36,37]. The spacer maintains soft-tissue tension, reduces pain, enhances the patients functional status and enables the patient to do physical therapy prior to reimplantation of a prosthesis. The spacer permits local antibiotic administration and induces the development of a pseudocapsule that can be mobilized with the cuff during ensuing surgeries. In a recent study, 9 of 11 patients who had a spacer implanted for sepsis or PSI were satisfied and put off the remotion of the spacer. Also other authors support prolonged or even permanent retention of the spacer as a possible substitute to reimplantation in complicated patients who are at increased surgical risk. Finally, a viable option for patients with cuff-tear arthropathy and a working deltoid, is the reverse shoulder arthroplasty. Reverse shoulder arthroplasty could permit improved function in patients who have undergone debridement of periprosthetic tissues. In the case of infection, the quality of debridement is deemed a crucial factor for the eradication of infection. An aggressive debridement of suspicious soft and bone tissue can be carried out with less apprehension for decreased functionality when a reverse shoulder replacement is going to be implanted [26,34].

Fig. (5). Intraoperative images of an infected shoulder arthroplasty (a) before the removal of the prosthesis, (b) after performing irrigation and debridement and (c) after the implantation of an antibiotic-impregnated cement spacer.

One-stage and two-stage reimplantation does give the greatest chance of restoring function, but in some cases this may not be possible. In the elderly, debilitated patients, with high-virulence germs, significant loss of soft tissue, or poor health, a reimplantation may be unwise. In these conditions, resection arthroplasty represents an acceptable solution. It offers the opportunity to obtain the eradication of infection and good pain relief with just one surgical procedure with the only downside being limited function [38]. Many studies have indicated that resection arthroplasty provides excellent eradication rates, although, often at the price of significant functional deficits [14]. In particular it is the loss of internal and external rotation that hinder the patients during activities of daily living. [36,39]. It is therefore generally accepted to be a treatment for older, low demand patients. Codd et al. [40] compared the treatment results with infected shoulder prostheses after resection arthroplasty and prosthesis reimplantation. Pain reduction was achieved with approximately the same efficacy with both joint resection and prosthesis revision. The patients who had resection arthroplasty, however, had significantly reduced shoulder motion and difficulties with every-day activities. Rispoli et al. [41] reported substantial functional impairments in spite of good pain relief in 18 patients treated with resection arthroplasty for PSI or failed shoulder replacement.