Multiflora and Gram-Negative Microorganisms Predominate in Infections Affecting Pelvic Endoprostheses Following Tumor Resection

Surgical site infections after sarcoma resections in the peripelvic region: do we need perioperative antibiotic prophylaxis?

Introduction

Surgical site infections (SSI) are one of the most common complications after extensive sarcoma resections and represent a daily challenge. SSI occur in up to 50% of cases particularly in the peripelvic area. One possible approach to reduce infection rate is perioperative antibiotic prophylaxis. The aim of this study therefore was to investigate the influence of perioperative antibiotic prophylaxis on the infection rate and the possible influence of location-specific antibiotic prophylaxis with ampicillin/sulbactam.

Methods

This monocentric retrospective study included 366 patients who underwent sarcoma resections in the groin, proximal thigh, or gluteal region. All patients were operated on by 2 surgeons after neoadjuvant pretreatment if necessary. 3 groups of patients were defined. Group 1: In 60.4% of all cases, antibiotic prophylaxis was administered with cephalosporins (also clindamycin in case of penicillin allergy). Group2: In 9.8% of cases, ampicillin/sulbactam was used. Group 3: 29.8% of patients did not receive any antibiotic prophylaxis.

Results

In 31.1% of treated cases, antibiotic therapy was prolonged due to extended tumor resections. Postoperative infections occurred in 23.2% (85 cases), in 77 cases within the first 90 days (on average after 20 days). The median operating time, blood loss was higher, and tumor size were significantly larger in cases with infections, compared to patients without infection. In group 1 and 2 with perioperative single-shot prophylaxis, infection occurred in 24.1% of cases, compared to 13.5% of cases without prophylaxis (group 3) (p= 0.032). In the patients with prolonged antibiotic therapy, infection occurred in 31.6% of cases, compared to 16.3% of cases without prolongation (p< 0.001). In the group 2, infection occurred in 19.4% of cases compared to 24.9% of cases in the group 1 (p= 0.479). In the multivariate analysis, surgery time longer 80 min, blood substitution, neoadjuvant radio- and chemotherapy proved to be a risk factor for SSI.

Discussion

Region adapted perioperative antibiotic prophylaxis may reduce the risk of infection after extended sarcoma resection in the peripelvic area. However, the particular bacterial spectrum of this anatomic region should be taken into account when deciding which antibiotics to use.

Composite Reconstruction With Irradiated Autograft Plus Total Hip Replacement After Type II Pelvic Resections for Tumors Is Feasible but Fraught With Complications

BACKGROUND

Malignancies involving the pelvic ring present numerous challenges, especially in the periacetabular area. Extensive resection of the pelvic region without reconstruction can lead to severe functional impairment. Numerous reconstructive options exist, but all have drawbacks. Extracorporeally irradiated autografts are one option for reconstruction after periacetabular resections; they offer the potential advantages of eliminating the risk of allogeneic reactions associated with allografts and preserving local anatomy. However, little is known about the durability and risks of this approach in pelvic reconstruction.

QUESTIONS/PURPOSES

(1) What are the survival rates of the autograft used, and if there is graft loss, what is the extent of this loss? (2) What are the functional outcomes after the implementation of this method? (3) What is the rate and nature of complications associated with this approach?

METHODS

This is a retrospective case series from one subspecialty tumor unit that evaluated patients treated between January 2005 to January 2022. During that time, three surgeons treated 48 patients with Type II resections (defined as resection of periacetabular area). Patients treated with isolated Type II resections were eligible, as were those treated either with Type I+II resections, Type II+III resections, Type I+II+III resections, and Type I+II+III+IV resections. Of those, 21% (10 of 48) were treated primarily with a cone prosthesis, 13% (6 of 48) were treated without femoral reconstruction, 10% (5 of 48) were treated with resection without reconstruction, and 6% (3 of 48) had a THA on the sacrum, leaving 50% (24 of 48) of patients who were treated with femoral and acetabular reconstruction using extracorporeally irradiated autograft and total hip replacement; those patients were potentially eligible for this study. During that time span, we used this approach in all Type II pelvic resection procedures, when a part of the hemipelvis could be preserved without resection (other than Type I+II+III+IV) and where we predicted that there would be sufficient bone stock after tumor removal. Of those, 21% (5 of 24) were lost to follow-up before 2 years, and 13% (3 of 24) died within 2 years with the reconstruction intact and without any reoperation or graft loss, leaving 67% (16 of 24) for analysis here. Demographic characteristics, type of tumor, tumor origin site, type of applied resection, and extent of applied surgical procedure were noted. Of 16 patients, 12 were male, with a mean age of 38 ± 21 years. Tumor types included chondrosarcoma in eight patients, malignant mesenchymal tumor in four patients, osteosarcoma in two patients, and Ewing sarcoma in two patients. Among these, 10 patients had tumors originating from the pelvis, whereas six patients had tumors originating from the proximal femur. We used a Kaplan-Meier estimator to calculate survivorship free from total or partial graft removal at 72 months. To measure functional results, the Musculoskeletal Tumor Society (MSTS) scoring system was utilized at most recent follow-up so as to be able to evaluate the impact of complications (if any) on the ultimate result. The MSTS score ranges from a minimum of 0 points to a maximum of 30 points, where a higher score reflects lower pain and higher functional and emotional capacity. Related complications, time of complications, secondary interventions, and mortality rates were also ascertained from chart review.

RESULTS

Graft survival rate at 72 months after initial reconstruction, free from partial or total graft removal, was 50% (95% CI 26% to 75%). Kaplan-Meier analyses revealed estimated mean time of graft removal as 43 months (95% CI 28 to 58). The graft was protected in eight patients on their final follow-up radiographs. The median (range) MSTS score was 18 (6 to 25) of 30 points at most-recent follow-up (these scores include patients who have had their grafts removed). In all, 15 of 16 patients had 17 complications; 16 were major complications (defined as those substantial enough to result in further surgery or a life- or limb-threatening event). A total of 14 of those 15 patients underwent one or more secondary procedures (a total of 21 unplanned additional procedures were performed in those patients). Deep infection was the most common complication, occurring in eight patients. Prosthesis dislocation occurred in four patients. Three patients developed aseptic acetabular component loosening, two had graft fractures, and one patient developed heterotopic ossification.

CONCLUSION

Composite reconstruction with extracorporeal irradiated autografts plus total hip replacement is a feasible reconstruction technique after Type II pelvic resections, although complications and reoperations were common. Although no reconstruction technique has been proven superior to other alternatives, the high risk of complications and reoperations associated with this technique should be considered when selecting from among possible alternative reconstruction methods.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Spectrum of Pathogens in Surgical Site Infections after Sarcoma Resection in the Peri-Pelvic and Pelvic Region. Distinct Location, Distinct Infection?

Background: Soft tissue sarcomas (STS) often occur in the peri-pelvic region (proximal thigh, groin, gluteal region). A common complication following resection of STS is surgical site infection (SSI). The peri-pelvic site appears to be particularly problematic. Surgical site infections are associated with a high proportion of gram-negative and anaerobic micro-organisms. To date, there are no published recommendations for peri-operative antibiotic prophylaxis in pelvic STS resection. Therefore, the aim of this study was to determine the rate of SSI and the spectrum of micro-organisms detected in this region. Methods: In this monocentric study, 366 patients were retrospectively evaluated. All of these patients had undergone surgery for STS in the peri-pelvic and pelvic regions. Surgical site infections were recorded, and the microbial spectrum was analyzed. Results: There were 85 (23.2%) patients with SSI, and 188 revisions were required in these patients (2.21 per case). Swabs were sterile in 20% of clinically infected cases. In total, 36.5% of infections were polymicrobial. The most common bacteria were coagulase-negative staphylococci in 31.5%, followed by Enterococcus species in 13.3% and Escherichia coli in 7.7%. In total, 30.8% of the bacteria were gram-negative and 25.9% were anaerobic. Conclusions: Our results demonstrate the uniqueness of the bacterial spectrum of SSI after STS resection in the peri-pelvic region. In the authors' opinion, recommendations regarding the peri-operative antibiotic prophylaxis need to be adapted for the typical microbial spectrum at this site.

Microbiology, Treatment, and Postoperative Outcomes of Gram-Negative Prosthetic Joint Infections-A Systematic Review of the Literature

INTRODUCTION

Gram-negative prosthetic joint infections (PJIs) represent 10% to 25% of all PJIs and are associated with worse outcomes than gram-positive infections. We sought to assess the microbiology, surgical treatment, and outcomes of patients with gram-negative PJIs.

METHODS

A systematic review using the PubMed and Embase databases was conducted. Our study was conducted following the PRISMA guidelines. Included studies were assessed for quality using the STROBE checklist. The primary outcome of analysis was treatment failure.

RESULTS

A total of 593 patients with gram-negative PJIs were included. Two-year survival free of treatment failure for hip and knee PJIs was 66% and 68% for acute infections, 39% and 78% for acute hematogenous infections, and 75% and 63% for chronic infections, respectively. Two-year survival free of treatment failure for acute infections treated with débridement, antibiotics, and implant retention was 65% and 67% for hip and knee PJIs, respectively. Exchange of the polyethylene during débridement, antibiotics, and implant retention was associated with higher treatment success (P = 0.045). Chronic PJIs treated with two-stage revision had a two-year treatment success rate of 87% and 65% for the hip and knee, respectively. Risk factors of treatment failure were chronic obstructive pulmonary disease and C-reactive protein ≥30 mg/L in acute PJIs and female sex, knee infection, and previously revised implant in chronic PJIs. Acute PJIs caused by Pseudomonas spp. were associated with lower treatment failure rates.

CONCLUSION

Gram-negative PJIs are associated with a high treatment failure rate. Patient comorbidities, preoperative biochemical tests, microorganism etiology, and PJI characteristics affected the treatment success rate.

LUMiC Endoprosthetic Reconstruction of Periacetabular Tumor Defects: A Multicenter Follow-up Study

UPDATE

This article was updated on July 17, 2024 because of a previous error, which was discovered after the preliminary version of the article was posted online. The byline that had read "Richard E. Evenhuis, MD 1 , Michiel A.J. van de Sande, MD, PhD 1,2 , Marta Fiocco, PhD 2,3,4 , Demien Broekhuis, MD 1 , Michaël P.A. Bus, MD, PhD 1 , and the LUMiC® Study Group*" now reads "Richard E. Evenhuis, MD 1 , Michiel A.J. van de Sande, MD, PhD 1,2 , Marta Fiocco, PhD 2,3,4 , Edwin F. Dierselhuis, MD, PhD 5 , Demien Broekhuis, MD 1 , Michaël P.A. Bus, MD, PhD 1 , and the LUMiC® Study Group*". The Department of Orthopaedic Surgery, Radboudumc, Nijmegen, The Netherlands, has been added as the affiliation for Edwin F. Dierselhuis, MD, PhD.

BACKGROUND

We previously reported promising early results for periacetabular tumor reconstructions using the LUMiC prosthesis. The current study evaluates mid-term complications, revision rates, cumulative incidence of implant revision, and risk factors for complications in a multicenter cohort.

METHODS

We assessed patients in whom a tumor defect after type P1b+2, P2, P2+3, or P1b+2+3 internal hemipelvectomy was reconstructed with a LUMiC prosthesis during the period of 2008 to 2022. Complications were reported according to the Henderson classification. Competing risks models were used to estimate the cumulative incidence of implant revision for mechanical and nonmechanical reasons, and reoperations for any complication. Cox models were used to study the effect of risk factors on dislocation and infection.

RESULTS

One hundred and sixty-six patients (median follow-up, 4.2 years [interquartile range, 2.6 to 7.6 years]) were included. A total of 114 (69%) were treated for a primary malignant tumor, 46 (28%) for metastatic carcinoma, 5 (3%) for a benign aggressive lesion, and 1 (1%) for another reason. One hundred and sixty-five reoperations were performed in 82 (49%) of the patients; 104 (63%) of the reoperations were within 6 months. Thirty-two (19%) of 166 implants were revised: 13 (8%) for mechanical reasons, mainly dislocation (n = 5, 3%), and 19 (11%) for nonmechanical reasons, mainly periprosthetic joint infection (PJI) (n = 15, 9%). The cumulative incidences of revision for mechanical reasons and PJI (Henderson 1 to 4) at 2, 5, and 10 years were 11% (95% confidence interval [CI], 7% to 17%), 18% (12% to 25%), and 24% (16% to 33%), respectively. Previous surgery at the same site was associated with an increased dislocation risk (cause-specific hazard ratio [HR CS ], 3.0 [95% CI, 1.5 to 6.4]; p < 0.01), and resections involving the P3 region were associated with an increased infection risk (HR CS , 2.5 [95% CI, 1.4 to 4.7]; p < 0.01).

CONCLUSIONS

Despite a substantial reoperation risk, the LUMiC prosthesis demonstrated its durability in the mid-term, with a low mechanical revision rate and most patients retaining their primary implant. Most complications occur in the first postoperative months. Patients with previous surgery at the same site had an increased dislocation risk and might benefit from more conservative rehabilitation and aftercare. Measures should be aimed at reducing the PJI risk, especially in resections involving the P3 region.

LEVEL OF EVIDENCE

Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Risk Factors and Management of Prosthetic Joint Infections in Megaprostheses-A Review of the Literature

Prosthetic joint infection (PJI) is the most common mode of failure of megaprostheses, yet the literature on the topic is scarce, and studies report conflicting data regarding the optimal treatment strategy. Patients with megaprostheses PJI are often immunosuppressed, and surgeons must balance the trade-off between treatment efficacy and morbidity associated with the surgery aiming for infection eradication. Our review on megaprostheses PJI focuses on two axes: (1) risk factors and preventative strategies; and (2) surgical strategies to manage this condition. Risk factors were classified as either unmodifiable or modifiable. Attempts to decrease the risk of PJI should target the latter group. Strategies to prevent PJI include the use of silver-coated implants, timely discontinuation of perioperative antibiotic prophylaxis, and adequate soft tissue coverage to diminish the amount of dead space. Regarding surgical treatment, main strategies include debridement, antibiotics, implant retention (DAIR), DAIR with modular component exchange, stem retention (DAIR plus), one-stage, and two-stage revision. Two-stage revision is the "gold standard" for PJI in conventional implants; however, its success hinges on adequate soft tissue coverage and willingness of patients to tolerate a spacer for a minimum of 6 weeks. DAIR plus and one-stage revisions may be appropriate for a select group of patients who cannot endure the morbidity of two surgeries. Moreover, whenever DAIR is considered, exchange of the modular components should be performed (DAIR plus). Due to the low volume of megaprostheses implanted, studies assessing PJI should be conducted in a multi-institutional fashion. This would allow for more meaningful comparison of groups, with sufficient statistical power. Level of evidence: IV.

The role of patient advocates and sarcoma community initiatives in musculoskeletal oncology. Moving towards Evidence-Based Advocacy to empower Evidence-Based Medicine

Musculoskeletal sarcomas are rare cancers that as the whole family of sarcomas pose several challenges at different levels, ranging from medical knowledge to clinical research and policymaking. Addressing these challenges, necessarily calls for the inclusion of patient perspective inside the decision-making processes of every area that contributes to treatment improvement, from the provision of high-quality services by healthcare organisations to research issues. Without patient-provided inputs to inform decisions, the current paradigm of patient-centred care makes no sense and sounds at the least irrational if not unethical. Putting PROMs on "centre stage" in cancer research and care, could allow to build a truly Evidence Based Advocacy (EBA) and therefore to empower Evidence Based Medicine (EBM).

Pelvic endoprosthesis in tumor lesions: experience of N.N. Petrov National Medical Research Center of Oncology

Introduction. Oncological endoprosthesis for tumors of the pelvic bones is rare. It is associated with certain difficulties and is insufficiently investigated.The study objective is to evaluate the results of surgical treatment of patients with tumors of the pelvis performed between 2012 and 2021 at the N.N. Petrov National Medical Research Center of Oncology, Ministry of Health of Russia.Materials and methods. The study included 23 patients with primary and secondary tumors of the pelvic bones who underwent limb-saving surgeries with substitution of the postresection defect with an endoprosthesis between 2012 and 2021. Mean follow-up duration was 19 months.Results. The most common postoperative complication was infection of the postoperative wound (n = 8; 35 %). Mechanical complications associated with the installed metallic prosthesis were observed in 4 (17 %) patients. Function al results were evaluated after 6 months using the Musculoskeletal Tumor Society Score (MSTS). Mean score per this scale was 53 % which corresponds to satisfactory outcome.Conclusion. Patients with malignant tumors of the pelvic bones should undergo treatment only in specialized medical facilities. Patients for organ-saving therapy should be carefully selected.

What's new in musculoskeletal oncology

We reviewed the recent literature related to primary musculoskeletal tumors and metastatic bone tumors. With regard to primary bone tumors, computer navigation systems and three-dimensional-printed prostheses seem to be new treatment options, especially in challenging anatomical locations, such as the sacrum and pelvis. Regarding the treatment of giant cell tumor of bone, recent studies have suggested that denosumab administration is related to a higher local recurrence rate following curettage, but a lower local recurrence rate following en bloc resection. In addition, there was no difference in the local recurrence rate at five years after surgery between short-term and long-term denosumab therapy. With regard to soft tissue tumors, percutaneous cryoablation appears to be a new treatment option for extra-abdominal desmoid tumors, with encouraging results. Regarding soft tissue sarcomas, a negative surgical margin of < 1 mm is sufficient to control local recurrence. Pexidartinib seems to be a promising systemic therapy for the treatment of tenosynovial giant cell tumors for which surgery is not expected to improve the function of the affected limb. Finally, the life expectancy of patients is the most important factor in determining the optimal surgical procedure for patients with impending or pathological fractures of the long bone due to metastatic bone tumors. Elevated C-reactive protein level was found to be an independent poor prognostic factor at 1 year after surgery for long bone metastases.

Imaging following surgery for primary appendicular bone tumours

Primary bone tumours are uncommon, with sarcomas accounting for < 0.2% of all malignancies. The survival rate of primary bone sarcomas has significantly improved due to (neo)adjuvant therapy, while improved surgical techniques and development of new prostheses have shifted the surgical focus from amputation to limb preservation in the vast majority of patients. A wide variety of surgical options are available for the treatment of primary bone tumours which depend upon histological diagnosis, their appearance at the time of presentation and response to any (neo)adjuvant therapy as required. This review is intended to help radiologists familiarise themselves with the management of primary appendicular bone tumours and expected normal postoperative appearances for the various surgical techniques, and to recognise potential complications.

A Short-Course Antibiotic Prophylaxis Is Associated with Limited Antibiotic Resistance Emergence in Post-Operative Infection of Pelvic Primary Bone Tumor Resection

Resections of primary pelvic bone tumors are frequently complicated by surgical site infections (SSIs), thereby impairing the functional prognosis of patients, especially in case of implant removal. Although prophylactic antibiotics play an essential role in preventing SSIs, there are presently no recommendations that support their appropriate use. This study aimed to assess the impact of a 24 h prophylactic protocol on the bacterial ecology, the resistance pattern, and the SSI healing rate. We hypothesized that this protocol not only limits the emergence of resistance but also results in a good cure rate with implant retention in case of SSI. A retrospective study was performed that included all patients with an SSI following a pelvic bone tumoral resection between 2005 and 2017 who received a 24 h antibiotic prophylaxis protocol. Twenty-nine patients with an SSI were included. We observed a 75.9% rate of polymicrobial infection, with a high prevalence of digestive flora microorganisms and a majority of wild-type phenotypes. We confirmed that there was no significant emergence of resistant flora. After first-line debridement, antibiotics (DA) if any implant was used, or debridement, antibiotics, and implant retention (DAIR) whenever possible, we obtained a 79.3% cure rate, with implant removal in 20% of cases. The absence of an implant was significantly associated with SSI healing. Early infection management and low resistance profiles may also have a positive effect, but this needs to be confirmed in a larger cohort. In light of this, the use of a 24 h prophylactic protocol in primary pelvic bone tumor resections is associated with a favorable infection cure rate and implant retention in case of SSI, and minimal selection of resistant microorganisms.

3D-Printed Modular Hemipelvic Endoprosthetic Reconstruction Following Periacetabular Tumor Resection: Early Results of 80 Consecutive Cases

BACKGROUND

Reconstruction with an endoprosthesis following pelvic tumor resection has increased over the years. However, the long-term results reflect a disappointing frequency of mechanical complications and failures. In an attempt to enhance implant fixation, an electron beam melting (EBM)-based modular hemipelvic endoprosthesis was introduced. Our aim was to explore the preliminary clinical outcomes for patients who have been managed with this prosthesis.

METHODS

We reviewed the records of 80 consecutive patients who had been managed at a single center between June 2015 and September 2017. Chondrosarcoma was the predominant diagnosis (31.3%). Osseous metastases were diagnosed in 16 patients (20.0%). The position of the reconstructed metallic acetabulum was measured on an anteroposterior pelvic radiograph. Bone ingrowth was evaluated in 2 samples harvested from patients with tumor recurrence.

RESULTS

After a median duration of follow-up of 32.5 months (range, 9 to 52 months), no acetabular component instability was detected on radiographs. Histological sectioning of specimens harvested from 2 patients with tumor recurrence showed bone trabeculae extending toward the implant and bone ingrowth within the porous network. At the time of the latest follow-up, 59 patients (73.8%) were alive with no evidence of disease, 5 patients (6.3%) were alive with disease, and 16 patients (20.0%) had died of disease. Local recurrence occurred in 9 patients (11.3%). The mean Musculoskeletal Tumor Society score at the time of the latest follow-up was 83.9% (range, 43% to 100%). Complications occurred in 16 patients (20%), with wound dehiscence being the most common complication (8 patients; 10%). No aseptic loosening was found. Five patients (6.3%) had deep infection, and 2 patients (2.5%) had dislocation.

CONCLUSIONS

The use of a 3-dimensional (3D)-printed modular hemipelvic endoprosthesis with a highly porous metal interface represents a potential choice as a pelvic endoprosthesis after internal hemipelvectomy for the treatment of a primary or metastatic tumor. These preliminary results demonstrate stable fixation with acceptable early functional and radiographic outcomes.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Treatment Outcomes and Attrition in Gram-Negative Periprosthetic Joint Infection

BACKGROUND

While the prevailing belief is that periprosthetic joint infection (PJI) caused by Gram-negative (GN) organisms confers a poorer prognosis than Gram-positive (GP) cases, the current literature is sparse and inconsistent. The purpose of this study is to compare the treatment outcomes for GN PJI vs GP PJI and Gram-mixed (GM) PJI.

METHODS

A retrospective review of 1189 PJI cases between 2007 and 2017 was performed using our institutional PJI database. Treatment failure defined by international consensus criteria was compared between PJI caused by GN organisms (n = 45), GP organisms (n = 663), and GM (n = 28) cases. Multivariate regression was used to predict time to failure.

RESULTS

GM status, but not GN, had significantly higher rates of treatment failure compared to GP PJI (67.9% vs 33.2% failure; hazards ratio [HR] = 2.243, P = .004) in the multivariate analysis. In a subanalysis of only the 2-stage exchange procedures, both GN and GM cases were significantly less likely to reach reimplantation than GP cases (HR = .344, P < .0001; HR = .404, P = .013).

CONCLUSION

Although there was no observed difference in the overall international consensus failure rates between GN (31.1% failure) and GP (33.2%) PJI cases, there was significant attrition in the 2-stage exchange GN cohort, and these patients were significantly less likely to reach reimplantation. Our findings corroborate the prevailing notion that GN PJI is associated with poorer overall outcomes vs GP PJI. These data add to the current body of literature, which may currently underestimate the overall failure rates of GN PJI treated via 2-stage exchange and fail to identify pre-reimplantation morbidity.

Antimicrobial Prophylaxis for the Prevention of Surgical Site Infections in Orthopaedic Oncology - A Narrative Review of Current Concepts

The incidence of surgical site infections (SSIs) after elective tumour orthopaedic surgery in adults is higher than non-oncologic orthopaedic surgery. Their causative microorganisms and antibiotic susceptibilities are also different from the non-oncologic cases; with no apparent predictable microbiological patterns. Clinicians continue to struggle to tailor the optimal prophylactic regimen for the very heterogeneous group of tumour patients. Many clinicians thus prolong the first-and second-generation cephalosporin agents, while a minority chooses to broaden the antimicrobial spectrum by combination prophylaxis. The variability in current practices and surgical techniques is enormous, even within the same setting. The scientific literature lacks adequate retrospective case-studies and there is currently only one prospective randomized trial. In this narrative review, we discuss various perioperative antibiotic concepts in oncologic orthopaedic surgery, including a summary of the state-to-the-art, opinions and difficulties related to the different prophylactic strategies.