Role of internal fixation in infection of open fractures: studies with Staphylococcus aureus and Proteus mirabilis

Effect of mechanical stability of osteosynthesis on infection rates: Timing of temporary and definitive fixation

Fracture related infection (FRI) remains one of the most challenging complications of orthopaedic trauma surgery. Several factors contribute to FRI development but, among those, particularly interesting from the orthopaedic surgeon's perspective is the contribution of mechanical stability and timing of fracture fixation. These are indeed crucial factors both in prevention and treatment of FRI and are directly influenced by the surgeon's work. While the role of stability has been studied and discussed, the pathophysiological process regulating such role and how this influences surgeon's treatment decision making is still debated. The same applies to the ideal timing of temporary or definitive fixation which varies according to the clinical scenario considered. In the present narrative review, we described the influence of mechanical stability on both FRI pathophysiology and on the decision making of FRI treatment. In addition, we analysed the impact of the timing of fracture fixation on the risk of FRI development particularly in those clinical scenarios where it has been shown to be specifically relevant, such as fractures affecting segments with poor soft tissue envelope, open fractures, damage control orthopaedics, and the need for soft tissue coverage.

The surgical management of fracture-related infection. Surgical strategy selection and the need for early surgical intervention

The aim of this narrative review is to describe the various surgical management strategies employed in fracture-related infection (FRI), to explore how they are selected and discuss the rationale for early surgical intervention. Surgical treatment options in patients with FRI include debridement, antibiotics and implant retention (DAIR), revision (exchange) or removal. In selecting a treatment strategy, a variety of factors need to be considered, including the condition of the bone, soft tissues, host and causative microorganism. Irrespective of the selected treatment strategy, prompt surgical intervention should be considered in order to confirm the diagnosis of an FRI, to identify the causative organism, remove necrotic or non-viable tissue that can serve as a nidus for ongoing infection, ensure a healthy soft tissue envelope and to prevent the vicious cycle of infection associated with skeletal and/or implant instability. Ultimately, the objective is to prevent the establishment of a persistent infection. Urgent surgery may be indicated in case of active, progressive disease with systemic deterioration, local progression of infection, deterioration of soft tissues, or progressive fracture instability. In case of static disease, the patient should be monitored closely and surgery can be performed on an elective basis, allowing adequate time for optimisation of the host through risk factor modification, optimisation of the soft tissues and careful planning of the surgery.

The role of implant retention and conservative management in the management of fracture-related infection

Fracture-related infection (FRI) management has advanced considerably in recent years, offering new possibilities for predictable rates of infection eradication. Debridement, antibiotics, and implant retention (DAIR) procedures have shown promise in the treatment of early FRI. This article provides an overview of the principles and indications of DAIR, including the importance of meticulous debridement and the management of dead space. The outcomes of DAIR are discussed, highlighting the range of fracture union rates reported in the literature. The role of antimicrobial suppression in optimizing host biology and facilitating surgical intervention is also explored. While further research is needed to establish optimal treatment strategies, DAIR offers a valuable treatment approach for FRI when specific criteria are met.

LEVEL OF EVIDENCE

IV.

Functional and Radiographic Outcomes of Open Proximal Femoral Fractures Caused by Gunshot Wounds in Yemen: A Prospective Cohort Study

Background

Open proximal femoral fractures caused by gunshot wounds are rare but devastating injuries that pose considerable challenges for prognosis and management. The aim of this study was to evaluate the functional and radiographic outcomes of patients with open proximal femoral fractures caused by gunshot wounds treated at 3 Level-I trauma centers in Yemen and to identify the factors that influence them.

Methods

We prospectively enrolled 174 patients with open proximal femoral fractures caused by gunshot wounds. The fractures were classified according to the Gustilo-Anderson and OTA/AO systems. The primary outcome measures were fracture union, infection, and functional outcomes. The secondary outcome measures were the Harris hip score (HHS) and the Short Form-36 (SF-36) health survey score. We performed multivariable logistic regression modeling to identify the predictors of complications and poor functional outcomes.

Results

The overall rate of fracture union was 87%. The complication rates were 18% for infection, 13% for nonunion, 23% for reoperation, 12% for delayed union, 4% for osteonecrosis, 6% for heterotopic ossification, and 2% for amputation. The mean HHS at the final follow-up was 78.4, and the mean SF-36 score was 67.3.

Conclusions

Open proximal femoral fractures caused by gunshot wounds are associated with high rates of complications and poor functional outcomes in Yemen. Early debridement, appropriate fixation, infection control, and adequate soft-tissue coverage are essential for achieving satisfactory results. The type of wound, the type of fracture, and the type of definitive fixation are significant predictors of the outcomes. Future studies should compare different fixation methods and evaluate the long-term outcomes and complications of these injuries.

Level of Evidence

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

Treatment of Fracture-Related Infection after Pelvic Fracture

BACKGROUND

The management of pelvic fractures is a significant challenge. Surgical site infection can result in the need for revision surgery, cause functional impairment, and lead to a prolonged length of stay and increased treatment costs. Although reports on fracture-related infection (FRI) after pelvic fracture fixation are sparsely reported in the literature, it is a serious complication. This study analysed patients with FRIs after pelvic fracture regarding patient characteristics, treatment strategies, and an evaluation of risk factors for FRI.

METHODS

In this retrospective single-centre study, FRI was diagnosed based on clinical symptoms of infection and a positive culture of a bacterial infection. Depending on the severity and acuteness of the infection, osseous stabilization was restored either via implant retention (stable implant, no osteolysis), exchange (loose implant or bony defect), or external fixation (recurrence of infection after prior implant retaining revision). Healing of infection was defined as no sign of recurring infection upon clinical, radiological, and laboratory examination in the last follow-up visit.

RESULTS

The FRI rate in our patient population was 7.5% (24/316). In 8/24 patients, the FRI occurred within the first three weeks after initial surgery (early) and 16/24 presented with a late onset of symptoms of FRI. A strategy of debridement, antibiotics, and implant retention (DAIR) was successful in 9/24 patients with FRI after pelvic fracture. A total of 10 patients required an exchange of osteo-synthetic implants, whereof three were exchanged to an external fixator. In five patients, we removed the implant because the fracture had already consolidated at the time of revision for infection. A total of 17/24 patients had a poly-microbial infection after a pelvic fracture and 3/24 patients died from post-traumatic multi-organ failure within the first 6 months after trauma. There were no cases of persistent infection within the remaining 21 patients.

CONCLUSIONS

Although poly-microbial infection is common in FRI after pelvic fracture, the recurrence rate of infection is relatively low. A complex pelvic trauma with significant soft tissue injury is a risk factor for recurrent infection and multiple revisions. A strategy of DAIR can be successful in patients with a stable implant. In cases with recurrent infection or an unstable fracture site, the exchange of implants should be considered.

A Hyaluronic Acid Hydrogel Loaded with Gentamicin and Vancomycin Successfully Eradicates Chronic Methicillin-Resistant Staphylococcus aureus Orthopedic Infection in a Sheep Model

Implantable orthopedic devices have had an enormously positive impact on human health; however, despite best practice, patients are prone to developing orthopedic device-related infections (ODRI) that have high treatment failure rates. One barrier to the development of improved treatment options is the lack of an animal model that may serve as a robust preclinical assessment of efficacy. We present a clinically relevant large animal model of chronic methicillin-resistant Staphylococcus aureus (MRSA) ODRI that persists despite current clinical practice in medical and surgical treatment at rates equivalent to clinical observations. Furthermore, we showed that an injectable, thermoresponsive, hyaluronic acid-based hydrogel loaded with gentamicin and vancomycin outperforms current clinical practice treatment in this model, eliminating bacteria from all animals. These results confirm that local antibiotic delivery with an injectable hydrogel can dramatically increase treatment success rates beyond current clinical practice, with efficacy proven in a robust animal model.

The influence of biomechanical stability on bone healing and fracture-related infection: the legacy of Stephan Perren

Bone healing is a complicated process of tissue regeneration that is influenced by multiple biological and biomechanical processes. In a minority of cases, these physiological processes are complicated by issues such as nonunion and/or fracture-related infection (FRI). Based on a select few in vivo experimental animal studies, construct stability is considered an important factor influencing both prevention and treatment of FRI. Stephan Perren played a pivotal role in the evolution of our current understanding of the critical relationship between biomechanics, fracture healing and infection. Furthermore, his concept of strain theory and the process of fracture healing is familiar to several generations of surgeons and has influenced implant development and design for the past 50 years. In this review we describe the role of biomechanical stability on fracture healing, and provide a detailed analysis of the preclinical studies addressing this in the context of FRI. Furthermore, we demonstrate how Perren's concepts of stability are still applied to current surgical techniques to aid in the prevention and treatment of FRI. Finally, we highlight the key knowledge gaps in the underlying basic research literature that need to be addressed as we continue to optimize patient care.

A systematic review on current osteosynthesis-associated infection animal fracture models

Objective

Osteosynthesis-associated infection is a challenging complication post fracture fixation, burdening the patients and the orthopaedic surgeons alike. A clinically relevant animal model is critical in devising new therapeutic strategies. Our aim was to perform a systematic review to evaluate existing preclinical models and identify their applications in aspects of animal selection, bacterial induction, fracture fixation and complications.

Methods

A systematic literature research was conducted in PubMed and Embase up to February 2020. A total of 31 studies were included. Information on the animal, bacterial induction, fracture fixation, healing result and complications were extracted.

Results

Animals selected included murine (23), rabbit (6), ewe (1) and goat (1). Larger animals had enabled the use of human-sized implant, however small animals were more economical and easier in handling. Staphylococcus aureus (S. aureus) was the most frequently chosen bacteria for induction. Bacterial inoculation dose ranged from 10^2-8 ​CFU. Consistent and replicable infections were observed from 10⁴ ​CFU in general. Methods of inoculation included injections of bacterial suspension (20), placement of foreign objects (8) and pretreatment of implants with established biofilm (3). Intramedullary implants (13), plates and screws (18) were used in most models. Radiological (29) and histological evaluations (24) in osseous healing were performed. Complications such as instability of fracture fixation (7), unexpected surgical death (5), sepsis (1) and persistent lameness (1) were encountered.

Conclusion

The most common animal model is the S. aureus infected open fracture internally fixated. Replicable infections were mainly from 10⁴ ​CFU of bacteria. However, with the increase in antibiotic resistance, future directions should explore polymicrobial and antibiotic resistant strains, as these will no doubt play a major role in bone infection. Currently, there is also a lack of osteoporotic bone infection models and the pathophysiology is unexplored, which would be important with our aging population.

The translational potential of this article

This systematic review provides an updated overview and compares the currently available animal models of osteosynthesis-associated infections. A discussion on future research directions and suggestion of animal model settings were made, which is expected to advance the research in this field.

Pathogenesis and management of fracture-related infection

BACKGROUND

Both fracture-related infections (FRIs) and periprosthetic joint infections (PJIs) include orthopaedic implant-associated infections. However, key aspects of management differ due to the bone and soft tissue damage in FRIs and the option of removing the implant after fracture healing. In contrast to PJIs, research and guidelines for diagnosis and treatment in FRIs are scarce.

OBJECTIVES

This narrative review aims to update clinical microbiologists, infectious disease specialists and surgeons on the management of FRIs.

SOURCES

A computerized search of PubMed was performed to identify relevant studies. Search terms included 'Fracture' and 'Infection'. The reference lists of all retrieved articles were checked for additional relevant references. In addition, when scientific evidence was lacking, recommendations are based on expert opinion.

CONTENT

Pathogenesis, prevention, diagnosis and treatment of FRIs are presented. Whenever available, specific data of patients with FRI are discussed.

IMPLICATIONS

Management of patients with FRI should take into account FRI-specific features. Treatment pathways should implement a multidisciplinary approach to achieve a good outcome. Recently, international consensus guidelines were developed to improve the quality of care for patients suffering from this severe complication, which are highlighted in this review.

Bacterial osteomyelitis in veterinary orthopaedics: Pathophysiology, clinical presentation and advances in treatment across multiple species

Bacterial osteomyelitis in veterinary patients can be challenging to diagnose and treat, given limited therapeutic options and reported success rates. Osteomyelitis is frequently associated with surgical implant devices, including those required to optimise stability and healing of fractures. However, management of osteomyelitis sometimes necessitates the removal of these surgical implant devices in order to eradicate infection or limit implant-related osteolysis. The goal of this article is to provide a general and species-specific review of bacterial osteomyelitis in a selection of domestic veterinary species, including cats, dogs, horses, cattle and camelids, with a focus on classification, clinical presentation, aetiologic agents, and common therapeutic interventions reported in the literature. New treatment options emerging from research and human medicine will be also discussed, as they also apply to current or future care of veterinary patients with osteomyelitis.

Bone healing is achievable despite extensive wound dehiscence and wide plate and screws exposure in children

BACKGROUND

Extensive wound dehiscence and wide plate and screw exposure in the early weeks following orthopaedic surgery in children is usually managed either by extensive debridement, lavage and secondary closure or hardware removal and external fixation.

PATIENTS

Three children with LCP plate and screws exposure were managed by simple repetitive debridement and local wound care without any IV antibiotics, nor secondary closure or hardware removal. All three cases occurred in the tibia, one following tibial osteotomy in lateral hemimelia with a long history of previous surgeries, one following wide excision of a tibial Ewing sarcoma with chemo- and radiotherapy, and the third following wide excision of a 12cm necrotic tibial segment due to chronic osteomyelitis. Bone healing was uneventful in 2 cases and was in progress in the case with the Ewing sarcoma. Plate and screws were removed in all cases, following an obvious bone healing in 2 cases, and forced by the need for chemotherapy due to the presence of lung metastases in the third case. Spontaneous soft tissue healing occurred thereafter.

CONCLUSION

A stable fixation may lead to a good bone healing despite an extensive wound dehiscence and a wide plate and screws exposure with just a proper local wound care and without any major additional surgery.

LEVEL OF EVIDENCE

Level IV.

Infection after fracture fixation: Current surgical and microbiological concepts

One of the most challenging complications in trauma surgery is infection after fracture fixation (IAFF). IAFF may result in permanent functional loss or even amputation of the affected limb in patients who may otherwise be expected to achieve complete, uneventful healing. Over the past decades, the problem of implant related bone infections has garnered increasing attention both in the clinical as well as preclinical arenas; however this has primarily been focused upon prosthetic joint infection (PJI), rather than on IAFF. Although IAFF shares many similarities with PJI, there are numerous critical differences in many facets including prevention, diagnosis and treatment. Admittedly, extrapolating data from PJI research to IAFF has been of value to the trauma surgeon, but we should also be aware of the unique challenges posed by IAFF that may not be accounted for in the PJI literature. This review summarizes the clinical approaches towards the diagnosis and treatment of IAFF with an emphasis on the unique aspects of fracture care that distinguish IAFF from PJI. Finally, recent developments in anti-infective technologies that may be particularly suitable or applicable for trauma patients in the future will be briefly discussed.

Can Normal Fracture Healing Be Achieved When the Implant Is Retained on the Basis of Infection? An Experimental Animal Model

BACKGROUND

Infection after open fractures is a common complication. Treatment options for infections developed after intramedullary nailing surgery remain a topic of controversy. We therefore used a rat fracture model to evaluate the effects of infection on osseous union when the implant was maintained.

QUESTIONS/PURPOSES

In a rat model, (1) does infection alter callus strength; (2) does infection alter the radiographic appearance of callus; and (3) does infection alter the histological properties of callus?

METHODS

An open femoral fracture was created and fixed with an intramedullary Kirschner wire in 72 adult male Sprague-Dawley rats, which were divided into two study groups. In the infection group, the fracture site was contaminated with Staphylococcus aureus (36 animals), whereas in the control group, there was no bacterial contamination (36 animals). No antibiotics were used either for prophylaxis or for treatment. We performed biomechanical (maximum torque causing failure and stiffness), radiographic (Lane and Sandhu scoring for callus formation), and histologic (scoring for callus maturity) assessments at 3 and 6 weeks. The number of bacteria colonies on the femur, wire, and soft tissue inside knee were compared to validate that we successfully created an infection model. The number of bacteria colonies in the soft tissue inside the knee was higher in the infection group after 6 weeks than after the third week, demonstrating the presence of locally aggressive infection.

RESULTS

Infection decreased callus strength at 6 weeks. Torque to failure (299.07 ± 65.53 Nmm versus 107.20 ± 88.81, mean difference with 95% confidence interval, 192 [43-340]; p = 0.007) and stiffness at 6 weeks (11.28 ± 2.67 Nmm versus 2.03 ± 1.68, mean difference with 95% confidence interval, 9 [3-16]; p = 0.004) both were greater in the control group than in the group with infection. Radiographic analysis at 6 weeks demonstrated the fracture line was less distinct (Lane and Sandhu score of 2-3) in the infection group and complete union was observed (Lane and Sandhu score of 3-4) in the control group (p = 0.001). Semiquantitative histology scores were not different between the noninfected controls and the rats with infection (score 10 versus 9).

CONCLUSIONS

Retaining an implant in the presence of an underlying infection without antibiotic treatment leads to weaker callus and impedes callus maturation compared with noninfected controls in a rat model. Future studies might evaluate whether antibiotic treatment would modify this result.

CLINICAL RELEVANCE

This model sets the stage for further investigations that might study the influence of different interventions on fracture healing in implant-associated osteomyelitis. Future observational studies might also evaluate the histological properties of callus in patients with osteomyelitis.

The value of 18-FDG PET/CT in the diagnosis and management of implant-related infections of the tibia: a case series

BACKGROUND

Positron emission tomography (PET) combined with Computerised Tomography (CT) is gaining ground in clinical settings due to its added value of combined metabolic and anatomical imaging. PET/CT has shown promising results in diagnosing both acute and chronic infection of the axial and appendicular skeleton. PET imaging has an advantage in patients with metallic implants because FDG uptake, in contrast to magnetic resonance imaging (MRI) and standard computed tomography (CT), is not hampered by metallic artifacts. The role of PET/CT in the evaluation of implant-related infections involving the tibia in particular has not been thoroughly studied.

PURPOSE

To investigate the usefulness of 18-FDG PET/CT in the diagnosis and treatment of implant-related infections of the tibia following osteosynthesis.

METHODS

We reviewed 10 patients who underwent internal fixation to the tibia following trauma (4 open fractures, 6 closed fractures) and presented later with clinical signs of a possible implant-related infection. In evaluating the patients we used standard work-up methods (standard radiographs, lab tests) as well as advanced imaging techniques (PET/CT) in order to confirm the diagnosis and decide upon the preferred treatment. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were then calculated for PET/CTs ability to predict presence of infection using intraoperative cultures as the gold standard.

RESULTS

PET/CT validated our working diagnosis 9 out of 10 patients. In particular, it helped distinguish between: infected nonunion (n=4), aseptic nonunion (n=1), soft tissue infection (n=2) and chronic osteomyelitis (n=3). The overall sensitivity and specificity of PET/CT for identifying an osseous infection were 85.7% and 100%, respectively. The PPV and NPV were 100% and 75%, respectively.

CONCLUSION

PET/CT is a promising imaging modality that can aid in the work up of patients with suspected implant-related infections of the tibia following osteosynthesis, and may be used as a supportive measure in clinical decision making.

Can we trust intraoperative culture results in nonunions?

OBJECTIVES

To identify the presence of bacterial biofilms in nonunions comparing molecular techniques (multiplex polymerase chain reaction and mass spectrometry, fluorescent in situ hybridization) with routine intraoperative cultures.

METHODS

Thirty-four patients with nonunions were scheduled for surgery and enrolled in this ongoing prospective study. Intraoperative specimens were collected from removed implants, surrounding tissue membrane, and local soft tissue followed by standard culture analysis, Ibis's second generation molecular diagnostics (Ibis Biosystems), and bacterial 16S rRNA-based fluorescence in situ hybridization (FISH). Confocal microscopy was used to visualize the tissue specimens reacted with the FISH probes, which were chosen based on the Ibis analysis.

RESULTS

Thirty-four patient encounters were analyzed. Eight were diagnosed as infected nonunions by positive intraoperative culture results. Ibis confirmed the presence of bacteria in all 8 samples. Ibis identified bacteria in a total of 30 of 34 encounters, and these data were confirmed by FISH. Twenty-two of 30 Ibis-positive samples were culture-negative. Four samples were negative by all methods of analysis. No samples were positive by culture, but negative by molecular techniques.

CONCLUSIONS

Our preliminary data indicate that molecular diagnostics are more sensitive for identifying bacteria than cultures in cases of bony nonunion. This is likely because of the inability of cultures to detect biofilms and bacteria previously exposed to antibiotic therapy.

LEVEL OF EVIDENCE

Diagnostic Level I. See Instructions for Authors for a complete description of levels of evidence.

A systematic review of animal models for Staphylococcus aureus osteomyelitis

Staphylococcus aureus (S. aureus) osteomyelitis is a significant complication for orthopaedic patients undergoing surgery, particularly with fracture fixation and arthroplasty. Given the difficulty in studying S. aureus infections in human subjects, animal models serve an integral role in exploring the pathogenesis of osteomyelitis, and aid in determining the efficacy of prophylactic and therapeutic treatments. Animal models should mimic the clinical scenarios seen in patients as closely as possible to permit the experimental results to be translated to the corresponding clinical care. To help understand existing animal models of S. aureus, we conducted a systematic search of PubMed and Ovid MEDLINE to identify in vivo animal experiments that have investigated the management of S. aureus osteomyelitis in the context of fractures and metallic implants. In this review, experimental studies are categorised by animal species and are further classified by the setting of the infection. Study methods are summarised and the relevant advantages and disadvantages of each species and model are discussed. While no ideal animal model exists, the understanding of a model's strengths and limitations should assist clinicians and researchers to appropriately select an animal model to translate the conclusions to the clinical setting.

Overview of concepts and treatments in open fractures

Open fractures are one of the few lower extremity surgical emergencies. These injuries require immediate treatment. If untreated, severe cases of open fracture can be limb threatening. This article is a review of the literature of open fractures and the current treatment guidelines.

Animal models of external traumatic wound infections

BACKGROUND

Despite advances in traumatic wound care and management, infections remain a leading cause of mortality,morbidity and economic disruption in millions of wound patients around the world. Animal models have become standard tools for studying a wide array of external traumatic wound infections and testing new antimicrobial strategies.

RESULTS

Animal models of external traumatic wound infections reported by different investigators vary in animal species used, microorganism strains, the number of microorganisms applied, the size of the wounds and for burn infections, the length of time the heated object or liquid is in contact with the skin.

METHODS

This review covers experimental infections in animal models of surgical wounds, skin abrasions, burns, lacerations,excisional wounds and open fractures.

CONCLUSIONS

As antibiotic resistance continues to increase,more new antimicrobial approaches are urgently needed.These should be tested using standard protocols for infections in external traumatic wounds in animal models.

Maintenance of hardware after early postoperative infection following fracture internal fixation

BACKGROUND

The development of a deep wound infection in the presence of hardware after open reduction and internal fixation presents a clinical dilemma, and there is scant literature to aid in decision-making. The purpose of the present study was to determine the prevalence of osseous union with maintenance of hardware after the development of postoperative infection within six weeks after internal fixation of a fracture.

METHODS

The present study included 121 patients from three level-I trauma centers, retrospectively identified from billing and trauma registries, in whom 123 postoperative wound infections with positive intraoperative cultures had developed within six weeks after internal fixation of acute fractures. The incidence of fracture union without hardware removal was calculated, and the parameters that predicted success or failure were evaluated.

RESULTS

Eighty-six patients (eighty-seven fractures; 71%) had fracture union with operative débridement, retention of hardware, and culture-specific antibiotic treatment and suppression. Predictors of treatment failure were open fracture (p = 0.03) and the presence of an intramedullary nail (p = 0.01). Several variables were not significant but trended toward an association with failure, including smoking, infection with Pseudomonas species, and involvement of the femur, tibia, ankle, or foot.

CONCLUSIONS

Deep infection after internal fixation of a fracture can be treated successfully with operative débridement, antibiotic suppression, and retention of hardware until fracture union occurs. These results may be improved by patient selection based on certain risk factors and the specific bacteria and implants involved.

Evolução clínica e funcional dos pacientes com infecção após artrodese de coluna lombar

OBJETIVOS: descrever a experiência dos autores no manejo da infecção após instrumentação da coluna lombar e suas consequências futuras. MÉTODOS: estudo de coorte prospectivo com pacientes portadores de infecção profunda pós-operatória, realizado entre janeiro de 1997 e janeiro de 2009. Todos os pacientes foram submetidos à revisão cirúrgica, coleta de material para exame microbiológico, lavagem exaustiva da região, debridamento dos tecidos desvitalizados, colocação de sistema de lavagem contínua, sutura primária e antibioticoterapia. Manteve-se a instrumentação em todos os pacientes. Os pacientes foram avaliados durante o seguimento por imagens radiográficas, estado clínico e funcional. Utilizaram-se a escala numérica da dor e o índice de incapacidade Oswestry. Os resultados numéricos foram submetidos a análises pareadas pelo teste de Wilcoxon. RESULTADOS: a incidência de infecção foi de 3,1% (15/485). O agente etiológico mais prevalente foi o Staphylococcus aureus. Todos os casos lograram consolidação. Em um seguimento médio de 47,6 meses, observaram-se mudanças nos escores da escala numérica da dor (p=0,001) e índice de incapacidade Oswestry (p=0,017). Na avaliação final, 64,2% dos pacientes (9/14) apresentaram incapacidade mínima e 35,8% (5/14), incapacidade moderada. CONCLUSÃO: o tratamento agressivo das infecções pós-operatórias de artrodese de coluna lombar permite evitar a retirada da instrumentação e manter a estabilidade vertebral. A despeito da complicação, os pacientes apresentaram melhoras em relação à dor e capacidade funcional pré-operatórias.

Prevention of biofilm formation with a coating of 2-methacryloyloxyethyl phosphorylcholine polymer

Device-associated infections are serious complications, and their prevention is an issue of considerable importance. Since biofilms are responsible for these refractory infections, effective methods to inhibit biofilm formation are required. In this investigation, stainless steel plates with and without 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer, i.e., poly (MPC-co-n-butyl methacrylate) (PMB) coating, were incubated in a medium containing bacteria. In the course of incubation, half of the specimens received antibiotics. The specimens were stained for nucleic acid and polysaccharides, and then examined with a confocal laser scanning microscope. The numbers of bacteria on the specimen surfaces were evaluated by an ATP assay. On the surfaces of the specimens without PMB coating, the formation of a biofilm enveloping bacteria was confirmed. The addition of antibiotics did not effectively decrease the number of bacteria. On the other hand, on the surfaces of the specimens with PMB coating, no biofilm formation was observed, and the number of bacteria was significantly decreased. The addition of potent antibiotics further decreased the number of bacteria by 1/100 to 1/1000 times. The PMB coating combined with the validated use of antibiotics might provide a method for the simultaneous achievement of biocompatible surfaces of devices and the prevention of device-associated infections.

[Management of deep wound infections in spinal lumbar fusions]

The rate of deep wound infections in spinal lumbar fusions is around 0.7% to 11.6%, being one of the causes of morbidity in acute phase. The aim of this study was to evaluate the management of spinal infection after internal lumbar fusions. Two hundred and sixty patients, who underwent to spinal surgery with lumbar fusion and iliac bone grafting, were analized, from January 1997 to January 2005. Wound infection was observed in eight (3%) cases. The average of age was 56 years, with a higher prevalence in males (5 patients). Most prevalent was Staphylococcus aureus in 6 patients. The treatment was done by intravenous antibiotic therapy folowed by oral therapy and local irrigation. The average time of hospitalization was 35.8 days. It was possible to erradicate infection without removal of instrumentation in all patients.

Treatment principles in the management of open fractures

The management of open fractures continues to provide challenges for the orthopedic surgeon. Despite the improvements in technology and surgical techniques, rates of infection and nonunion are still troublesome. Principles important in the treatment of open fractures are reviewed in this article. Early antibiotic administration is of paramount importance in these cases, and when coupled with early and meticulous irrigation and debridement, the rates of infection can be dramatically decreased. Initial surgical intervention should be conducted as soon as possible, but the classic 6 h rule does not seem to be supported in the literature. All open fractures should be addressed for the risk of contamination from Clostridium tetani. When possible, early closure of open fracture wounds, either by primary means or by flaps, can also decrease the rate of infection, especially from nosocomial organisms. Early skeletal stabilization is necessary, which can be accomplished easily with temporary external fixation. Adhering to these principles can help surgeons provide optimal care to their patients and assist them in an early return to function.

Union of a chronically infected internally stabilized segmental defect in the rat femur after debridement and application of rhBMP-2 and systemic antibiotic

OBJECTIVES

The goal of this study was to determine whether recombinant human bone morphogenetic protein-2 (rhBMP-2) would induce new bone formation in an internally stabilized segmental defect with a chronic bacterial infection in the rat femur and whether treatment with systemic antibiotic would enhance this effect.

METHODS

A 6-mm unilateral femoral segmental defect was surgically created in 120 Sprague-Dawley rats, internally stabilized with a polyacetyl plate and 6 Kirschner wires, and contaminated with 10(4) colony-forming units of Staphylococcus aureus. After 2 weeks, all defects were surgically debrided and implanted with 0, 20, or 200 microg of rhBMP-2 in a type 1 bovine collagen sponge. Half of the animals in each treatment group received 4 weeks of systemic antibiotic, and half did not. Animals were euthanized at 4 or 12 weeks after debridement. Bone formation within and adjacent to the defect was assessed using microcomputed tomography, torsional failure testing and undecalcified histology.

RESULTS

No substantial callus formed in the infected defects without rhBMP-2. Significantly more mineralized callus was induced with the higher dose of rhBMP-2 than with the lower dose (P = 0.001), with systemic antibiotic therapy than without (P < 0.001), and at 12 weeks after debridement compared with 4 weeks (P < 0.001).

CONCLUSIONS

Recombinant human bone morphogenetic protein-2 maintained its osteoinductive capability in the presence of a chronic infection, and this property was enhanced by systemic antibiotic. This study presents an intervention that may potentially accelerate fracture healing in the presence of infection and colonized hardware, thereby permitting earlier removal of the hardware, and more timely and effective treatment of infection.

Staphylococci and implant surfaces: a review

Surfaces of internal fracture fixation implants are generally designed to encourage soft- and/or hard-tissue adherence, eventually leading to tissue or osseo integration. Unfortunately, this feature may also encourage bacterial adhesion. About half of the two million cases of nosocomial infections per year in the US are associated with indwelling devices. In the UK, implant-associated infections are estimated to cost pound 7-11 million per year, and with the rise in antibiotic-resistant bacteria, are an important issue. Soft-tissue infections and osteomyelitis are serious complications associated with implants, particularly open fractures, external fixation devices, and intramedullary nailing. Consequences of implant-associated infections include prolonged hospitalization with systemic antibiotic therapy, several revision procedures, possible amputation, and even death. This review discusses the issue of implant-associated infections and some of the methods used to prevent bacterial adhesion to osteosynthesis implants.

Staphylococcus aureus adhesion to titanium oxide surfaces coated with non-functionalized and peptide-functionalized poly(L-lysine)-grafted-poly(ethylene glycol) copolymers

Implanted biomaterials are coated immediately with host plasma constituents, including extracellular matrix (ECM); this reaction may be undesirable in some cases. Poly(L-lysine)-grafted-poly(ethylene glycol) (PLL-g-PEG) has been shown to spontaneously adsorb from aqueous solution onto metal oxide surfaces, effectively reducing the degree of non-specific adsorption of blood and ECM proteins, and decreasing the adhesion of fibroblastic and osteoblastic cells to the coated surfaces. Cell adhesion through specific peptide-integrin receptors could be restored on surfaces coated with PLL-g-PEG functionalized with peptides of the RGD (Arg-Asp-Gly) type. To date, no study has examined the effect of surface modifications by PLL-g-PEG-based polymers on bacterial adhesion. The ability of Staphylococcus aureus to adhere to the ECM and plasma proteins deposited on biomaterials is a significant factor in the pathogenesis of medical-device-related infections. This study describes methods for visualizing and quantifying the adhesion of S. aureus to smooth and rough (chemically etched) titanium surfaces without and with monomolecular coatings of PLL-g-PEG, PLL-g-PEG/PEG-RGD and PLL-g-PEG/PEG-RDG. The different surfaces were exposed to S. aureus cultures for 1-24h and bacteria surface density was evaluated using scanning electron microscopy and fluorescence microscopy. Coating titanium surfaces with any of the three types of copolymers significantly decreased the adhesion of S. aureus to the surfaces by 89-93% for PLL-g-PEG, and 69% for PLL-g-PEG/PEG-RGD. Therefore, surfaces coated with PLL-g-PEG/PEG-RGD have the ability to attach cells such as fibroblasts and osteoblasts while showing reduced S. aureus adhesion, resulting in a selective biointeraction pattern that may be useful for applications in the area of osteosynthesis, orthopaedic and dental implantology.

Eradication by surfactant irrigation of Staphylococcus aureus from infected complex wounds

Treatment of infected orthopaedic hardware usually requires the removal of the appliance. When the device is removed and immediately replaced, persistent infection frequently complicates this exchange procedure. We modeled the exchange procedure in rats by passing a wire suture through a posterior spinous process and then contaminating the wound with Staphylococcus aureus. We then investigated whether a sequence of surfactant enriched irrigation solutions (Castile soap followed by benzalkonium chloride, sequential surfactant irrigation) had a greater capacity to eradicate Staphylococcus aureus from the experimental wound than did the standard wound irrigant, normal saline. When we left the wire in place through the 2-week course of the study, sequential surfactant irrigation showed only a modest advantage over normal saline (staphylococci recovered from 39% versus 58% of wound cultures respectively). Simple removal of the wire 24 hours after implantation and bacterial contamination prevented wound infection in most animals (with the wire removed, 38% of the animals remained infected versus 85% with the wire left in place), without regard to the irrigation solution. Alternatively, when we removed the wire after 24 hours, irrigated the wound, and then placed a fresh wire back into the wound, sequential surfactant irrigation showed a significant advantage over NS (54% of the animals irrigated with sequential surfactants remained infected versus 100% of the animals irrigated with normal saline). Our findings confirm the importance of a contaminated medical device for promoting foreign body infection; our findings also show that sequential surfactant irrigation has therapeutic value in a rat model of orthopaedic device infection; this irrigation protocol should be studied further as a potential agent for the treatment of infected orthopaedic wounds.

Fracture fixation in the mutilated hand

Early anatomic (or near anatomic; lingers do not impinge or overlap during flexion or extension) stable fracture fixation provides the foundation for successful wound management and for the repair, reconstruction, and healing of all damaged tissues in a mutilating hand injury. It also plays an instrumental role in pain control and affords an optimal opportunity for timely and favorable rehabilitation of and recovery from mutilating injuries of the hand. Kirschner or other wiring systems or mini external fixators may be used for simple fractures, in children, when rapid fracture fixation is necessary, and for provisional fracture fixation. Mini plates should be considered for fractures with comminution or loss and in instances of multiple fractures. Fingers with segmental injury of three or more tissues should be considered for early amputation to avoid prolonged and impaired recovery of the hand. Every effort should be made to preserve the thumb and its function by repair or reconstruction.

Surfactant wound irrigation for the treatment of staphylococcal clinical isolates

Deep wound infection involving an implanted biomaterial is a devastating complication in orthopaedic surgery. Two-thirds of such infections are monomicrobial and the most commonly isolated bacteria in human osteomyelitis and orthopaedic device infection are Staphylococcus aureus and Staphylococcus epidermidis. The purpose of the current study was to examine the effectiveness of the previously reported sequential surfactant irrigation protocol against human-isolated clinical strains of Staphylococcus aureus and Staphylococcus epidermidis in the rat model of orthopaedic implant contamination. The infectivity rate of human-isolated clinical strains of Staphylococcus aureus in a contaminated complex orthopaedic wound was reduced effectively by a sequential surfactant irrigation protocol. Also, in this model, the infectivity of Staphylococcus epidermidis was reduced by normal saline irrigation alone when compared with no irrigation. Therefore, the sequential surfactant irrigation protocol may represent an effective method of wound irrigation in monomicrobial Staphylococcus aureus orthopaedic implant contamination, and normal saline irrigation may suffice in cases of monomicrobial Staphylococcus epidermidis contamination. Additional studies are necessary to determine the clinical use of surfactant irrigation.

Foot and ankle infections after surgery

Infection after foot and ankle surgery or trauma can range from the common superficial cellulitis to the less common deep soft tissue or bone infections that can have disastrous consequences. The emergence of antibiotic-resistant organisms has made treatment of infection more difficult, even though promising new antibiotics are being developed. Prevention of infection, through proper patient selection and meticulous surgical technique, is essential to satisfactory outcomes.

Synergy between Staphylococcus aureus and Pseudomonas aeruginosa in a rat model of complex orthopaedic wounds

BACKGROUND

We observed an interaction in animals inoculated concomitantly with Staphylococcus aureus and Pseudomonas aeruginosa during a study of the efficacy of surfactants for disinfection of orthopaedic wounds. This led us to investigate whether synergy could be demonstrated between Staphylococcus aureus and Pseudomonas aeruginosa in a rat model of complex orthopaedic wounds.

METHODS

A wire was implanted into the spinous process of a lumbar vertebra of Sprague-Dawley rats through a dorsal incision. Animals were divided into two groups: group one was inoculated with either Staphylococcus aureus or Pseudomonas aeruginosa, and group two received a polymicrobial inoculation with both test organisms in varying concentrations. After inoculation, the wounds were irrigated and closed. On postoperative day 14, all animals were killed and specimens from the wounds were cultured. The number of colony-forming units (CFU) of Staphylococcus aureus or Pseudomonas aeruginosa needed to cause infection in 50% of the animals (ID50) was determined with use of the Reed-Muench method. The infection rate associated with each inoculum combination was calculated, and the two groups were compared.

RESULTS

The ID50 was 2.8 x 10(4) CFU for Staphylococcus aureus and 4.8 x 10(5) CFU for Pseudomonas aeruginosa. The combination of 10(3) CFU of Staphylococcus aureus with low concentrations (10(2), 10(3), or 10(4) CFU) of Pseudomonas aeruginosa yielded infection rates that were higher than those found with either organism alone at the same concentrations. The combination of 10(3) CFU of Staphylococcus aureus and 10(3) CFU of Pseudomonas aeruginosa yielded a 75% infection rate, which was significantly higher (p = 0.004) than that associated with 10(3) CFU of either organism alone. As the Pseudomonas aeruginosa concentration was increased (to 10(5), 10(6), and 10(7) CFU), this trend reversed, and the infection rate decreased to 33% (p = 0.004). Low concentrations of Pseudomonas aeruginosa (0 to 10(5) CFU) combined with 10(6) CFU of Staphylococcus aureus yielded infection rates ranging from 83% to 100%. At the higher concentrations of Pseudomonas aeruginosa (10(6) and 10(7) CFU), however, the infection rate again decreased, to 33% (p = 0.005). Only Staphylococcus aureus was isolated from the cultures of the specimens from the animals that had received a polymicrobial inoculum.

CONCLUSIONS

Synergy between Staphylococcus aureus and Pseudomonas aeruginosa was demonstrated when low levels of each organism were present in the wound. As the Pseudomonas aeruginosa concentration was increased, the infection rates fell well below what would be anticipated, suggesting that low concentrations of Pseudomonas aeruginosa enhance the ability of Staphylococcus aureus to cause infection in this orthopaedic wound model. At the same time, the presence of Staphylococcus aureus in the ratios tested decreased the rate of infection by Pseudomonas aeruginosa.

CLINICAL RELEVANCE

Staphylococcus aureus is a pathogen commonly seen in orthopaedic patients. The pathogenicity of Staphylococcus aureus was shown to be increased in the presence of anaerobic bacteria. This study is the first one that we are aware of that demonstrated synergy between Staphylococcus aureus and Pseudomonas aeruginosa, at low concentrations, in a wound model while at the same time showing that Staphylococcus aureus lowers the rate of Pseudomonas aeruginosa infection.

Pathophysiology of infections after internal fixation of fractures

Infection complicating internal fixation of fractures is a serious complication that is difficult to treat. Whenever metallic devices are implanted in vivo, successful biointegration requires that host cells colonize the highly reactive implant surface. Bacteria such as staphylococci can also become adherent to metallic or polymeric implants and will compete with host cells for colonization of the implant surface. Once adherent, these bacteria form a biofilm and undergo phenotypic changes that make them resistant to the normal host immune response as well as to antibiotics. Furthermore, metallic implants themselves cause specific deficits in the function of the local immune system that may render the host response to infection inadequate. Any associated soft-tissue injury causes even greater impairment of local immune function. Despite the potentially detrimental impact of internal fixation, fracture stability is of paramount importance in achieving fracture union and in preventing infection. It has been demonstrated in animal models that contaminated fractures without internal fixation develop clinical infection more commonly than similar fractures treated with internal fixation at the time of colonization. Because of the potential for infection whenever internal fixation is utilized, appropriate prophylactic antibiotic coverage for staphylococci and Gram-negative organisms should be provided. Open wounds and severely damaged soft tissues require aggressive management so that a viable soft-tissue envelope is maintained around the implant. Host factors such as smoking and malnourishment should be corrected. Early diagnosis and aggressive treatment of implant-related infection with antibiotics, debridement, and maintenance of stable internal fixation are essential to successful treatment.

Delayed infection after elective spinal instrumentation and fusion. A retrospective analysis of eight cases

STUDY DESIGN

A retrospective analysis of eight cases of delayed spinal infection after elective posterior or combined anterior and posterior spinal instrumentation and fusion.

OBJECTIVES

These cases are reviewed to identify risk factors for delayed spinal infection after elective instrumentation and to describe the treatment of this complication.

SUMMARY OF BACKGROUND DATA

Delayed spinal infection after elective spinal instrumentation and fusion is uncommon. This diagnosis is frequently difficult.

METHODS

Five cases seen in the senior author's practice and three referral cases are reviewed.

RESULTS

Of these eight cases, the organisms were Staphylococcus epidermidis in six cases, Propionibacterium acnes in one cases, and in the final patient, all intraoperative cultures were negative. Clinical presentations were variable; however, all patients reported back pain. Seven patients had elevated erythrocyte sedimentation rates, averaging 57 mm/hour. Only two had elevated white blood cell counts. No distant foci of infection were identified in any patient. Five-patients were found to have at least one pseudarthrosis. All patients were treated with debridement, instrumentation removal, and primary wound closure over drains followed by a minimum 6-week course of culture-directed postoperative antibiotics. At an average follow-up of 18 months, no patient has evidence of infection.

CONCLUSIONS

The diagnosis of delayed infection after elective spinal instrumentation and fusion requires a high index of suspicion. These infections may have been caused by intraoperative inoculation. All patients were successfully treated with debridement, instrumentation removal, and culture-directed postoperative antibiotics.

Influence of bacterial strains on bone infection

Experiments were performed on 120 rabbits to compare the probability of infection after bone surgery without an implant, with polymethylmethacrylate, and with autografts. Staphylococcus aureus phage type 94/96, isolated from a human osteomyelitis, was instilled into the intramedullar cavity after reaming of the femoral canal and before insertion of the implant. The different 50% infective doses were determined for each of the groups for comparative purposes. The bacterial concentrations required to produce infection in femora without an implant were two times less than those necessary in femora implanted with polymethylmethacrylate. The bone graft required bacterial concentrations nine times less than those necessary to infect femora containing polymethylmethacrylate and four times less than those required to infect femora without an implant. The results presented here confirm that the susceptibility to infection in orthopaedic surgery is not only material dependent but also bacteria dependent.

Management of penetrating joint injuries

A classification scheme for penetrating joint injuries is presented. Diagnostic techniques and treatment recommendations for managing penetrating joint injuries in small animals are described. Techniques used in human and equine patients are discussed for comparison.

Contaminated fractures of the tibia: a comparison of treatment modalities in an animal model

External fixation is the current standard treatment for skeletal stabilization of open tibial fractures, but intramedullary fixation techniques have become increasingly popular. The aim of this study was to compare, in an animal model, the susceptibility to infection of contaminated fractures stabilized with external fixation with that of contaminated fractures fixed with intramedullary locking nails with or without reaming. A unilateral osteotomy of the tibia was performed in 15 goats under general anesthesia. Each osteotomy was stabilized with either (a) a unilateral biplanar external fixator, (b) an 8 mm diameter intramedullary rod inserted without reaming of the medullary cavity, or (c) a 10 mm diameter rod inserted after reaming. A standardized inoculum of Staphylococcus aureus, 10(3) colony forming units per milliliter, was placed at each osteotomy site on a piece of absorbable gelatin sponge, to simulate contamination of an open fracture. Antibiotics were not administered. The animals were allowed full activity after the procedure. Fourteen days postoperatively, the animals were killed, radiographs of the tibiae were taken, and the tibiae were harvested in a sterile manner. Multiple specimens for quantitative microbiological analysis were taken from the fracture site and from sites 3 cm distal and 6 cm proximal to the fracture. Additional specimens of bone were taken for histological study. Clinical, radiographic, and microbiological analysis demonstrated that, in this animal model, there were significantly fewer and less severe infections in fractures fixed with external fixation than in those fixed with an intramedullary nail with or without reaming. There was marked cortical necrosis in tibiae that had been fixed with nailing and reaming.

Infection at the site of implanted materials with and without preadhered bacteria

A study was undertaken to examine the role of bacterial adherence in the development of infection at the site of an implant. The amount of in vitro adherence of Staphylococcus epidermidis was greatest for stainless steel, followed by polymethylmethacrylate and commercially pure titanium, and was least for polymethylmethacrylate with gentamicin. These materials then were preincubated with S. epidermidis and implanted. The number of organisms that were isolated and the rate of infection followed the same pattern as that in the in vitro studies. Materials that were not preincubated with bacteria also were implanted and bacteria were injected into the site. The number of organisms isolated from the site and the rate of infection were lower than those for the preincubated materials, but the trend was the same as in both the in vitro and the in vivo studies. The rates of infection and colonization correlated with the propensity for the organisms to adhere to a given material. Materials colonized with S. epidermidis at the time of implantation caused a high rate of infection. The ability of organisms to adhere to a material in vitro is correlated with their propensity to cause biomaterial-based infection.

Regional limb perfusion with antibiotics in three horses

Antibiotics were delivered to chronically infected tissues by regional limb perfusion in three horses with osteomyelitis associated with orthopedic implants. Two infections were resolved with implants in place; in one, a sequestrum was resorbed. In one horse, regional antibiotic perfusion was applied to treat progressively worsening bone infection after initial implants loosened and were removed.

Microbial adherence on poly(methyl methacrylate) (PMMA) surfaces

Infection remains a major complication following the use of implanted biomaterials. Often these infections are caused by low-virulence organisms or by a mixture of organisms (polymicrobial). In this study two methods were used to quantitate the bacteria which had adhered to poly(methyl methacrylate) (PMMA) samples. The bacteria were eluted from the sample using an ultrasonic cleaner. The number eluted was then counted by colony counts, which determines viable organisms and by particle counting which counts both viable and nonviable organisms. A known adherent strain of Staphylococcus epidermidis and a strain of Proteus mirabilis were used. In general the adherence of S. epidermidis was greater than that of Proteus. When the two organisms were used together, there was an alteration in the adherence pattern which generally increased the adherence of Proteus and had no effect or decreased the adherence of S. epidermidis. The use of both quantitation techniques provided important information on the adherence of organisms to PMMA to which gentamicin had been added. It was evident that organisms did adhere to the PMMA plus gentamicin samples but were not viable when eluted. The amount of adherence to PMMA plus gentamicin was similar to that of PMMA alone at 30 min but was markedly decreased at 24 h. There was a considerable dead biofilm mass on the PMMA plus gentamicin samples which might be a significant promoter of late infections by providing a surface attractive to other strains of bacteria.

Effect of Staphylococcus epidermidis on adherence of Pseudomonas aeruginosa and Proteus mirabilis to polymethyl methacrylate (PMMA) and gentamicin-containing PMMA

The goals of this study were to determine 1) effect of Staphylococcus epidermidis adherence and biofilm production on adherence of the opportunistic pathogens Proteus mirabilis and Pseudomonas aeruginosa to polymethyl methacrylate (PMMA); 2) if the biofilm killed by autoclaving altered adherence of other organisms; 3) if adherence of S. epidermidis to gentamicin-containing PMMA altered adherence of the opportunistic pathogens P. mirabilis and P. aeruginosa to gentamicin-containing PMMA. Results show that biofilms formed by S. epidermidis, whether alive or dead, significantly increased adherence of Pseudomonas. Adherence of Proteus was significantly increased on dead biofilms and increased, but not significantly (p = less than 0.1), on live ones. Greatest adherence seen in the study was to autoclaved biofilms. Significant adherence of Proteus and Pseudomonas was found on gentamicin-containing PMMA specimens, which were preincubated with S. epidermidis for formation on the biofilm. These results indicate that a biofilm is formed on PMMA-gentamicin specimens and this may impair the ability of gentamicin to kill other organisms.

Factors influencing bacterial adherence to biomaterials

The adherence of bacteria to implanted medical devices is believed to be important in the development of implant associated infections. Measures which reduce bacterial adherence should reduce the incidence of these infections. However, in order to assess the importance of adherence, the effectiveness of methods to reduce adherence, and compare data from different laboratories, the conditions of the in vitro studies on adherence need to be specified. There are currently no correct and incorrect methods, however, methods used need to be carefully described. The studies reported here indicate that the definition of adherence needs to be established, with the use of polystyrene as the reference material recommended. Since the adherent organisms lose adherence traits with culture, cultures must be selected for adherence regularly. It is important to control the number of organisms/ml but the volume used is not important. The medium used to grow the organisms and the use of stationary, rocking or flow conditions will alter adherence and need to be specified and be consistent within a set of experiments. Culture conditions, methods of rinsing the material, methods of elution and counting, or direct counting of organisms on the material need to be specified. Finally, as much information as possible on the bulk and surface properties of the material should be provided. The handling of the material for the experiments should be careful and defined. Fingerprints, contact with protein, wet surfaces vs dry surfaces, etc., will all affect the subsequent adherence. The materials should not be re-used since the removal of the adherent proteins or the biofilm is very difficult. Progress can be made in this important area if the details of procedures are specified.