Infection resistance of unreamed solid, hollow slotted and cannulated intramedullary nails: an in-vivo experimental comparison

Treatment of Infected Tibia Non-union Using a Novel Solid Intramedullary Nail Custom-Made for Antibiotic-Impregnated Cement Coating

The chronic and incapacitating condition of infected non-union of the long bones continues to be a challenging issue for surgeons in terms of efficient and economical treatment. A number of variables, such as open fractures, soft tissue or bone loss, infection following internal fixation, persistent osteomyelitis with pathologic fractures, and surgical debridement of infected bone, can result in infected non-unions. An infected non-union is typically treated in two stages. To transform an infected non-union into an aseptic non-union, the initial step involves debridement, either with or without the insertion of antibiotic cement beads and systemic antibiotics. In order to ensure stability, external or internal fixation - with or without bone grafting - is carried out in the second stage. There is a wealth of literature supporting the use of antibiotic-impregnated cement-coated intramedullary (IM) nailing for infected non-union of tibia and femur fractures. In contrast to cement beads, the cement nail offers stability throughout the fracture site, and osseous stability is crucial for the treatment of an infected non-union. When using antibiotics for this purpose, they should possess unique qualities, including low allergenicity, heat stability, and a broad spectrum of activity. The most commonly utilised medication has been gentamicin, which is followed by vancomycin. Furthermore, it has been discovered that solid nails are more resistant to local infection than cannulated IM nails. In this case study, the patient was treated with a solid IM nail that had a specially designed slot on its exterior surface for the application of cement impregnated with antibiotics. In conclusion, an easy, affordable, and successful treatment for infected non-union of the tibia is antibiotic cement-impregnated nailing. It has strong patient compliance and removes the problems associated with external fixators, which makes it superior to them. A few benefits of this approach are early weight-bearing, stabilisation of the fracture, local antibiotic treatment, and the potential for accelerated rehabilitation. Additionally, lowering the requirement for continuous antibiotic medication may lessen the chance that antibiotic resistance may arise.

Biomechanical Principles of Intramedullary Nails in Veterinary and Human Medicine

Intramedullary nails are specialized metal rods inserted into the medullary cavity of a fractured bone and secured to reduce load on the fracture site, provide stability, and permit healing. The purpose of this review is to highlight the biomechanics of orthopaedic intramedullary nailing, as well as discuss the biomechanical considerations that have shaped implant design and fixation technique in veterinary and human medicine. Relevant studies were included from the PubMed database and Google Scholar for discussion on the basic science and nail design of intramedullary nails. Implant design and implementation continues to progress, with new innovative designs currently under investigation. A lack of consensus remains on the superior implant material. Recent studies, particularly in human populations, have supported the use of reaming based on reoperation rates, nonunion rates, and dynamization. Design modifications, such as the expandable intramedullary nails and angle-stable interlocking designs, have been investigated as methods of improving cortical contact and resisting torsional stress. Intramedullary nailing is a valuable stabilization technique for long bone fractures across a variety of species. The technology continues to undergo design improvements in both veterinary and human medicine.

Micro-CT analysis of osteomyelitis of rabbit tibial for model establishment and biomaterials application in tissue engineering

Osteomyelitis is one of the most difficult diseases to treat in orthopedics field. The construction of animal models of osteomyelitis is now more mature but still lacks a deeper criterion other than "successful infection". In this work, rabbit tibial osteomyelitis model with S. aureus infection was established. Whole tibia, cortical bone around bone window, and tibial condyle were characterized in considerable detail using micro-CT and other means at 2/4/6 weeks, respectively. The results show that in addition to the obvious inflammatory response and bone destruction, osteomyelitis caused some other effects on compact and cancellous bone, and in particular, changes in bone mineral density after infection were of interest. Although the modeling groups all exhibited osteolysis and bone loss, their overall bone mineral density averages and those of the control groups were mostly in the range of 870 mg/cm³ to 920 mg/cm³, without statistical difference. The results suggest that overall bone mineral density is determined by both bone destruction conditions and the amount of dead bone deposition. This work provides a reference basis for the selection of time points for the subsequent animal models establishment and some valuable reference indicators of the application of biomaterials in tissue engineering.

Animal Models for Postoperative Implant‐Related Spinal Infection

Postoperative infections following implant‐related spinal surgery are severe and disastrous complications for both orthopaedic surgeons and patients worldwide. They can cause neurological damage, disability, and death. To better understand the mechanism of these destructive complications and intervene in the process, further research is needed. Therefore, there is an urgent need for efficient, accurate, and easily available animal models to study the pathogenesis of spinal infections and develop new and effective anti‐bacterial methods. In this paper, we provide a general review of the commonly used animal models of postoperative implant‐related spinal infections, describe their advantages and disadvantages, and highlight the significance of correctly choosing the model according to the infection aspect under investigation. These models are valuable tools contributing to the better understanding of postoperative spinal infections and will continue to facilitate the invention of novel preventative and treatment strategies for patients with postoperative spinal infections. However, although they are valid and reproducible in some respects, the current animal models present certain limitations. Future ideal spinal infection animal models may assess the bacterial load of the same animal in real‐time in vivo, and better mimic the human anatomy as well as surgical techniques. Strains other than Staphylococcus aureus account for a large proportion of postoperative spinal infections, and thus, the establishment of models to evaluate other types of microbial infections is expected in the future. Furthermore, novel transgenic models established on advancements in genome editing are also likely to be developed in the future.

Preclinical models of vertebral osteomyelitis and associated infections: Current models and recommendations for study design

Spine-related infections, such as vertebral osteomyelitis, discitis, or spondylitis, are rare diseases that mostly affect adults, and are usually of hematogenous origin. The incidence of this condition has gradually risen in recent years because of increases in spine-related surgery and hospital-acquired infections, an aging population, and intravenous (IV) drug use. Spine infections are most commonly caused by Staphylococcus aureus, while other systemic infections such as tuberculosis and brucellosis can also cause spondylitis. Various animal models of vertebral osteomyelitis and associated infections have been investigated in mouse, rat, chicken, rabbit, dog, and sheep models by hematogenous and direct inoculation in surgery, each with their strengths and limitations. This review is the first of its kind to concisely analyze the various existing animal models used to reproduce clinically relevant models of infection. Spine-related infection models must address the unique anatomy of the spine, the avascular nature of its structures and tissues and the consequences of tissue destruction such as spinal cord compression. Further investigation is necessary to elucidate the specific mechanisms of host-microbe response to inform antimicrobial therapy and administration techniques in a technically demanding body cavity. Small-animal models are not suitable for large instrumentation, and difficult IV access thwarts antibiotic administration. In contrast, large-animal models can be implanted with clinically relevant instrumentation and are resilient to repeat procedures to study postoperative infection. A canine model of infection offers a unique opportunity to design and investigate antimicrobial treatments through recruitment a rich population of canine patients, presenting with a natural disease that is suitable for randomized trials.

Functional outcome of patients of tibial fracture treated with solid nail (SIGN nail) versus conventional hollow nail - A randomized trial

BACKGROUND

Trauma related disabilities disproportionately affects low and middle income countries due to lack of resources, skills and optimal implants. Despite adequate animal studies, biomechanical studies, cohort studies and comparison studies we are not aware of any randomized trial to compare the functional outcome of SIGN (Surgical Implant Generation Network, US) solid nailing with a hollow nailing for tibial shaft fracture.

METHODS

Sixty patients (≥16 years) of closed and Gustilo grade I traumatic fractures of the leg were randomized into SIGN solid nailing or hollow nailing group. Cases with compromised soft tissue and grossly deformed medullary canal were excluded. Functional outcome and need for resurgery were the primary outcomes while the secondary outcomes were duration of surgery, intraoperative blood loss, overall pain (VAS), radiological union (RUST), surgery related complications (infection, malalignment, shortening, nonunion) and pain/range of motion (ROM) of knee/ankle. All SIGN surgery related data were entered and retrieved online from www.signsurgery.org.

RESULT

The demographical parameters were symmetrically distributed between the groups (p > 0.05). 2 cases in SIGN nailing and 4 cases in hollow nailing needed open reduction. The functional outcome, as assessed by blinded physiotherapist using Johner and Wruh criteria, was excellent in 18 (62.06%), good in 6 (20.68%), fair in 3 (10.34%) and poor in 2 (6.89%) for SIGN nail whereas it was 16 (57.14%), 8 (28.57%), 3 (10.71%) and 1 (3.57%) respectively for hollow nail. There was 1 case of implant failure and 1 case of infection. Intraoperative blood loss (397 ± 94.47 ml versus 350 ± 75.43 ml, p = 0.037) and duration of surgery (94.8 ± 14.57 min versus 82.0 ± 12.36 min, p = 0.001) were significantly more in hollow nailing group. At final follow up, overall pain on weight bearing (VAS score) and radiological union (RUST score) were 2.1 and 11.7 for SIGN nailing while they were 2.7 and 11.3 respectively for hollow nailing.(p = 0.41 and 0.45 respectively) The malrotation (p = 1.000), shortening (p = 1.000), varus-valgus angulation (p = 0.511), AP angulation (p = 0.706), ROM ankle (p = 0.239) and ROM knee (p = 0.086) were similar.

CONCLUSION

Solid SIGN nailing gives comparable functional outcome as conventional hollow nailing for tibia shaft fracture. For developing world with limited resources, SIGN nail is useful which is supplied freely and is designed to be used without image intensifier and fracture table.

Current State of Bone Adhesives-Necessities and Hurdles

The vision of gluing two bone fragments with biodegradable and biocompatible adhesives remains highly fascinating and attractive to orthopedic surgeons. Possibly shorter operation times, better stabilization, lower infection rates, and unnecessary removal make this approach very appealing. After 30 years of research in this field, the first adhesive systems are now appearing in scientific reports that may fulfill the comprehensive requirements of bioadhesives for bone. For a successful introduction into clinical application, special requirements of the musculoskeletal system, challenges in the production of a bone adhesive, as well as regulatory hurdles still need to be overcome. In this article, we will give an overview of existing synthetic polymers, biomimetic, and bio-based adhesive approaches, review the regulatory hurdles they face, and discuss perspectives of how bone adhesives could be efficiently introduced into clinical application, including legal regulations.

[Comparative study of different concentrations of methicillin-resistant Staphylococcus aureus in the preparation of chronic femoral osteomyelitis models]

Objective

To investigate the appropriate concentration of methicillin-resistant Staphylococcus aureus (MRSA) in establishing chronic femoral osteomyelitis model in rabbits.

Methods

Forty-eight adult New Zealand white rabbits were randomly divided into 6 groups with 8 rabbits in each group. Animals in groups B, C, D, E, and F were injected 1×10 9, 1×10 8, 1×10 7, 1×10 6, 1×10 5 CFU/mL MRSA on the location of 2 cm of the femoral supracondyle, respectively, and group A was injected with aseptic saline as a control. The general observation were performed at 4 weeks after operation, and the wound secretions were taken for bacteriological examination. The serum C-reactive protein content was detected at preoperation and 2 weeks and 4 weeks after operation. The X-ray, CT scan, and Norden imaging scoring were performed at 4 weeks after operation. At 4 weeks after operation, the animals were sacrificed, and the specimens were observed and evaluated by general scores; and the HE staining and histological score were also performed.

Results

Five rabbits died of severe infection in group B, 2 died in group C, and no rabbit died in groups D, E, and F. General observation showed that the incision healed without soft tissue swelling in group A; most animals had visible incision swelling and sinus formation, femoral thickening, bone destruction, and damage decreased with the decreasing of the concentration of liquid bacterial in groups B-D; the infection signs were seen in groups E and F, and the degree of infection were less than that of group D. Bacteriological examination showed that fistula formation animal in groups B, C, D, and E were cultured with positive results, and with the decrease of concentration, the number of animal fistula formation decreased gradually; and bacteriological culture did not be performed in group F because of no sinus formation. There was no significant difference in the content of C-reactive protein between groups before operation ( P>0.05). The contents of C-reactive protein in groups B-F were significantly higher than those in group A at 2 and 4 weeks after operation ( P<0.05). At 4 weeks after operation, the content of C-reactive protein was in the order of groups B, C, D, E, F, and A in turn from high to low, showing significant differences between groups ( P<0.05). Imaging examination showed that there was no soft tissue swelling and bone destruction in group A; bone destruction, massive sequestrum formation, and soft tissue swelling were found in groups B and C; bone destruction was observed in groups D and E, and the degree of sequestrum formation was not as good as that in group C; and there was a small amount of bone infection in group F. The Norden scores in groups B-F were significantly higher than that in group A, and in groups B and C than those in groups D, E, and F, and in groups D and E than that in group F ( P<0.05); there was no significant difference between groups B and C, and between groups D and E ( P>0.05). The specimens general observation scores in groups B-F were significantly higher than that in group A, while in groups B and C than those in groups D, E, and F ( P<0.05); there was no significant difference between groups D, E, and F ( P>0.05). HE staining showed that the structure of bone trabecula in group A was clear and the structure was arranged neatly; in groups B-F, trabecular bone destruction and inflammatory cell infiltration were seen and the degree gradually decreased. The histological scores in groups B-F were significantly higher than that in group A, and in group B than those in groups C-F, in groups C and D than that in group F ( P<0.05); there was no significant difference between groups C, D, and E, and between groups E and F ( P>0.05).

Conclusion

The optimal MRSA concentration of rabbit model of chronic osteomyelitis of femur is between 1×10 6 and 1×10 7 CFU/mL.

Animal Models of Osteomyelitis

There are numerous reports in the literature using animal models of osteomyelitis for investigating pathogenesis, diagnosis, and treatment of bone infections. Rabbits, rats, and dogs are commonly used animals, and, less frequently, chickens, guinea pigs, miniature pigs, goats, and sheep. Commonly used bones for creating local osteomyelitis include tibia, femur, and radius, and, less frequently, mandible and spine. When designing a specific model, one should consider which animal and which bone will be used, which route for inoculation (either local injection or systemically through vascular injection), which bacterial species and how many bacteria should be applied, if and what sclerosing agent, foreign body or implant should be employed, and if local trauma is needed. Basic methods of evaluation include clinical observation, radiography, microbiology, and histology.

Influence of Material and Microtopography on the Development of Local Infection in vivo: Experimental Investigation in Rabbits

Polishing the surface of internal fracture fixation (IFF) implant materials can ease implant removal and reduce irritation to gliding tissues by reducing soft tissue adhesion and bony overgrowth. Thus, polishing the surface of these implants is expected to have significant clinical benefit in certain situations. The aim of the present study was to determine if polishing the surface of an IFF device influences susceptibility to infection.

The local infection rate associated with 4-hole 2.0 mm Synthes® locking compression plates (LCPs) composed of clinically available commercially pure titanium (cpTi) and titanium aluminium niobium (TAN) in their standard microrough form was compared with that of their test polished equivalents and also to clinically available electropolished stainless steel (EPSS). The LCPs were fixed in locking mode onto the tibia of mature, female New Zealand White rabbits and a clinical strain of Staphylococcus aureus was added to the implantation site. Twenty eight days after surgery the rabbits were euthanized and assessed for infection. The rank order based on descending ID50 was; polished TAN, standard TAN, standard cpTi, EPSS and finally polished cpTi, however, the ID50 values did not differ greatly between the groups with the same material. Using the LCP model in locking mode, polishing the surface of both cpTi and TAN was not found to influence the susceptibility to infection in our animal model.

Influence of implant properties and local delivery systems on the outcome in operative fracture care

Fracture fixation devices are implanted into a growing number of patients each year. This may be attributed to an increase in the popularity of operative fracture care and the development of ever more sophisticated implants, which may be used in even the most difficult clinical cases. Furthermore, as the general population ages, fragility fractures become more frequent. With the increase in number of surgical interventions, the absolute number of complications of these surgical treatments will inevitably rise. Implant-related infection and compromised fracture healing remain the most challenging and prevalent complications in operative fracture care. Any strategy that can help to reduce these complications will not only lead to a faster and more complete resumption of activities, but will also help to reduce the socio-economic impact. In this review we describe the influence of implant design and material choice on complication rates in trauma patients. Furthermore, we discuss the importance of local delivery systems, such as implant coatings and bone cement, and how these systems may have an impact on the prevalence, prevention and treatment outcome of these complications.

Open Intramedullary Nailing for Segmental Long Bone Fractures: An Effective Alternative in a Resource-restricted Environment

Background:

Closed, locked intramedullary nailing has been accepted as the gold standard in the care of femoral fractures, with reported union rates as high as 98–100%. Closed, locked intramedullary nailing often requires expensive equipment which is a challenge in developing countries. Segmental long bone fractures are often a result of high-energy trauma and hence often associated with a lot of injuries to the surrounding soft tissues. This consequently results in higher rates of delayed or nonunion. This study was proposed to review the outcome of management of segmental fractures with locked intramedullary nails, using an open method of reduction.

Methods:

A retrospective analysis was made of data obtained from all segmental long bone fractures treated with intramedullary nailing over a 1-year period. Records were retrieved from the folders of patients operated on from January 2011 to December 2011. Patients were followed up for a minimum of 1 year after the surgery.

Results:

We managed a total of 12 segmental long bone fractures in 11 patients. Eight of the 12 fractures were femoral fractures and 10 of the fractures were closed fractures. All but one fracture (91.7%) achieved union within 4 months with no major complications.

Conclusions:

Open method of locked intramedullary nailing achieves satisfactory results when used for the management of long bone fractures. The method can be used for segmental fractures of the humerus, femur, and tibia, with high union rates. This is particularly useful in low-income societies where the use of intraoperative imaging may be unavailable or unaffordable. It gives patients in such societies, a chance for comparable outcomes in terms of union rates as well as avoidance of major complications. Larger prospective studies will be necessary to conclusively validate the efficacy of this fixation method in this environment.

The use of gentamicin-coated nails in complex open tibia fracture and revision cases: A retrospective analysis of a single centre case series and review of the literature

INTRODUCTION

Despite modern advances in fracture care, deep (implant-related) infection remains a problem in the treatment of tibia fractures. There is some evidence that antibiotic-coated implants are beneficial in the prevention of this sometimes devastating complication. In the following study we describe our results using a gentamicin-coated intramedullary tibia nail (Expert Tibia Nail (ETN) PROtect™) for the surgical treatment of complex open tibia fracture and revision cases.

MATERIALS AND METHODS

We describe the outcome of patients treated between January 2012 and September 2013, using a gentamicin-coated intramedullary tibia nail. Treatment indications included acute, Gustilo grade II-III, open tibia fractures or closed tibia fractures with long-term external fixation prior to intramedullary nailing and complex tibia fracture revision cases with a mean of three prior surgical interventions. Outcome parameters in this study were deep infection and nonunion.

RESULTS

In total, 16 consecutive patients with 16 tibia fractures were treated with a gentamicin-coated intramedullary nail. The overall patient population was subdivided into two groups. The first group consisted of 11 patients (68.8%) with acute fractures who were treated with a gentamicin-coated intramedullary nail. The second group consisted of 5 complex revision cases (31.2%). In our patient population no deep infections could be noted after the treatment with a gentamicin-coated tibia nail. Nonunion was diagnosed in 4 patients (25.0%), 1 of these was a revision case.

CONCLUSIONS

Musculoskeletal complications place a cost burden on total healthcare expenditure. Better understanding of the epidemiology and pathogenesis is essential because this can lead to prevention rather than treatment strategies. The purpose of the study was to evaluate a gentamicin-coated tibia nail in the prevention of deep (implant-related) infection. In our patient population no deep infections occurred after placement of the gentamicin-coated nail. Following this study and literature data, antibiotic-coated implants seem a potential option for prevention of deep infection in trauma patients. In the future this statement needs to be confirmed by large randomised clinical trials.

Risk factors for nonunion after intramedullary nailing of femoral shaft fractures: Remaining controversies

INTRODUCTION

Intramedullary nailing (IMN) is the preferred treatment for femoral shaft fractures in adults. Although previous studies published good outcomes, some controversies remain. The purpose of this retrospective study was to identify factors that influence outcome after IMN for femoral shaft fractures.

MATERIALS AND METHODS

Between July 1998 and July 2013, we treated 230 patients with 248 femoral shaft fractures. Statistical analyses were performed to determine predictors of nonunion. The following set of variables was selected based on the speculation that they would contribute to the outcome: sex (male or female), smoking, obesity, polytrauma, fracture type, open fractures, Gustilo type, primary external fixation (EF) and reaming.

RESULTS

Initial fracture stabilization was performed by IMN in 161 (64.9%) and by EF in 87 (35.1%) fractures. There were no documented cases of deep infection. Nonunion was diagnosed in 27 patients with 28 fractures (11.3%). Factors affecting nonunion in the univariate analysis were Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association (AO/OTA) fracture type (odds ratio [OR] 25.0; p<0.0001), Gustilo type (OR 0.64; p=0.0358), and EF (OR 0.42; p=0.0401). Multiple logistic regression analysis only identified AO/OTA fracture type (OR 22.0; p<0.0001) as a risk factor for nonunion. Fracture reaming did not change the outcome (OR 0.80; p=0.6073). A separate analysis showed that damage control EF was not a risk factor in polytrauma patients (OR 0.76; p=0.5825).

CONCLUSIONS

Fracture stabilisation with IMN is a good treatment option for femoral shaft fractures in adults. The purpose of this study was to evaluate risk factors of poor outcome after IMN of femoral shaft fractures. The present analysis revealed that there was no difference in the outcome whether the fracture was reamed or not. Univariate and multivariate analysis could only correlate AO/OTA fracture type with the occurrence of nonunion. Therefore, in this study, unreamed nailing and damage control EF were not associated with a negative outcome.

Modelling for conflict: the legacy of ballistic research and current extremity in vivo modelling

Extremity ballistic injury is unique and the literature intended to guide its management is commonly misinterpreted. In order to care for those injured in conflict and conduct appropriate research, clinicians must be able to identify key in vivo studies, understand their weaknesses and desist the propagation of miscited and misunderstood ballistic dogma. This review provides the only inclusive critical overview of key studies of relevance to military extremity injury. In addition, the non-ballistic studies of limb injury, stabilisation and contamination that will form the basis from which future small animal extremity studies are constructed are presented. With an awareness of the legacy of military wound models and an insight into available generic models of extremity injury and contamination, research teams are well placed to optimise future military extremity injury management.

The use of gentamicin-coated nails in the tibia: preliminary results of a prospective study

BACKGROUND

The use of antibiotic-coated implants may reduce the rate of infection and facilitate fracture healing after surgical treatment of tibial shaft fractures. A new biodegradable gentamicin-loaded coating of an implant (UTN PROtect) was CE-certified in August 2005. In this prospective, non-randomized case series, we investigated the clinical, laboratory and radiological outcomes of 21 patients who underwent surgical treatment in closed or open tibial fractures, as well as revisions with the UTN PROtect gentamicin-coated intramedullary nail.

METHODS

Of 21 patients (13 men, 8 women), 19 completed the 6-month follow-up. The study population included patients with complex tibial fractures and late revision cases. Clinical outcomes comprised adverse events, including infections and the SF-36 physical score. Laboratory outcomes, including C-reactive protein and leukocyte count as inflammatory markers, haemoglobin and serum gentamicin, were measured at baseline and up to 6 months post operatively. Radiographic assessments of fracture healing and weight-bearing capacity were determined at 5 weeks, 3 and 6 months after surgery.

RESULTS

No implant-related infections occurred; one patient had superficial wound healing problems. Mean C-reactive protein levels remained below 5 mg/L throughout the study, with a peak at 4-7 days after surgery (4.4 mg/L; range 0.5-16.1 mg/L). Leukocyte counts and haemoglobin levels did not vary over time during the study. The mean SF-36 physical score at 6 months was 42.6 (range 19.4-56.7). Radiographic union defined as three or four bridged cortices was achieved in 11 patients (58%) after 6 months. The remaining eight patients showed partial fracture healing with one or two bridged cortices. Additionally, 13 patients (68%) demonstrated full weight-bearing capacity after 6 months.

CONCLUSIONS

The use of the UTN PROtect intramedullary nail was associated with good clinical, laboratory and radiological outcomes after 6 months. These preliminary results support the use of gentamicin-coated implants as a new potential treatment option for the prevention of infection in trauma patients and in revision cases.

LEVEL OF EVIDENCE

Level II.

In vivo evaluation of the effect of intramedullary nail microtopography on the development of local infection in rabbits

BACKGROUND AND AIM

Fractures of the tibia and femoral diaphysis are commonly repaired by intramedullary (IM) nails, which are currently composed of either electropolished stainless steel (EPSS) or standard, non-polished titanium-aluminum-niobium (TAN). Once the fracture has fully healed, removal of IM nails is common, but the strong adhesion of bone to standard TAN complicates removal. Polishing the surface of TAN IM nails has been shown to reduce bony adhesion and ease implant removal without compromising fixation. Polished TAN nails are, therefore, expected to have significant clinical benefit in situations where the device is to be removed. The aim of the present study was to determine the effect of polishing TAN IM nails on susceptibility to infection in an animal model.

MATERIALS AND METHODS

Solid IM nails (Synthes, Betlach, Switzerland) composed of standard TAN were compared with polished equivalents and also to clinically available EPSS nails. The surface chemical and topographical properties of the materials were assessed by X-ray photon spectroscopy (XPS), white light profilometry, and scanning electron microscopy (SEM). An in vivo infection study was performed using a clinical isolate of Staphylococcus aureus that was characterized with respect to various virulence factors.

RESULTS

Polishing TAN IM nails caused no significant change to the chemistry of the nails, but the topography of the polished TAN nails was significantly smoother than standard TAN nails. In the infection study, the rank order based on descending infectious dose 50 (ID(50)) was: standard TAN, polished TAN, and finally EPSS. The ID(50) values did not differ greatly between any of the groups.

CONCLUSIONS

Polishing the surface TAN IM nails was not found to influence the susceptibility to infection in our animal model.

Influence of bacteria on spinal implant-centered infection: an in vitro and in vivo experimental comparison between Staphylococcus aureus and mycobacterium tuberculosis

STUDY DESIGN

an in vitro and in vivo experimental study.

OBJECTIVE

this study was undertaken to evaluate differences in the capability of inducing an implant-centered infection between Staphylococcus aureus and Mycobacterium tuberculosis.

SUMMARY OF BACKGROUND DATA

bacterial infection is still one of the most serious and devastating complications after orthopedic implant surgery despite the advent of new antibiotics and treatment methods.

METHODS

S. aureus and M. tuberculosis were separately cultured with titanium plates. The bacteria colonized on the plates were isolated and cultured on culture medium. They were evaluated and compared by colony-forming units enumeration. Scanning electron microscopy was used to evaluate the difference in the colonization features of the 2 pathogens. In the in vivo experiment, 22 dogs were used to assess the susceptibility to infection after a local bacterial challenge with either S. aureus or M. tuberculosis.

RESULTS

S. aureus showed heavy adhesion and multiplication on the surface of titanium plates in vitro, whereas M. tuberculosis rarely adhered to the surface of the plates. Under scanning electron microscopy, S. aureus colonization was observed: the coccoid was widespread on the surface of the plates but only a few M. tuberculosis cells scattered on the surface of the plates. In in vivo test, the infection rateforthe S. aureus inoculation was higher than that for the M. tuberculosis challenge. The infection rate for the entire test population (n = 44 sites) was 39.58% (19/48). The infection rates were 54.17% (13/24) for the S. aureus challenge and 25% (6/24) for the M. tuberculosis challenge, respectively (P < 0.05).

CONCLUSION

it is less likely for M. tuberculosis to adhere and form a biofilm on an implant surface than S. aureus. Under otherwise identical conditions, M. tuberculosis contamination following instrumented spine surgery might lead to less occurrence of infection than S. aureus contamination.

Infection in fracture fixation: can we influence infection rates through implant design?

Musculoskeletal infection is one of the most common complications associated with surgical fixation of bones fractured during trauma. These infections usually involve bacterial colonisation and biofilm formation on the fracture fixation device itself, as well as infection of the surrounding tissues. Antibiotic prophylaxis, wound debridement and postsurgical care can reduce the incidence of, but do not prevent, these infections. Much research and development has been focussed on ways to further reduce the incidence of infection and in the following short review we describe our experiences investigating the contribution of the basic design of fracture fixation devices on the susceptibility to infection. It has been shown in animal studies that device size, shape, mode of action and material and topography play an interrelated role in the susceptibility to infection. Although direct extrapolation from animal studies to the clinical setting is difficult, close consideration of the design factors that can reduce the incidence of infection in animal models is expected to help minimise the incidence of infection associated with any clinically implemented fracture fixation device.

The selection of appropriate bacterial strains in preclinical evaluation of infection-resistant biomaterials

Implant-related infections are broadly recognized as one of the most serious and devastating complications associated with the use of biomaterials in medical practice. The growing interest and need for the development of implant materials with reduced susceptibility to microbial colonization and biofilm formation has necessitated the development of a series of in vitro and in vivo models for evaluation and preclinical testing. Current technologies provide these investigations with an ample choice of qualitative and quantitative techniques for an accurate assessment of the bioactivity and anti-infective efficacy of any new compound or device. These tests are typically performed using a reference bacterial strain designated as the test or reference strain. Recent molecular epidemiological studies have identified the complex clonal nature of most prevalent etiological agents implicated in implant-associated infections. New information which is continually emerging on the identity and the characteristics of both sporadic and epidemic clones must be considered when selecting a reference. A new emerging requirement is that the strain should be representative of the clones causing clinically relevant infections; they should, therefore, belong to the most prevalent epidemic clones rather than to sporadic ones, which may occur in only 1 out of 200 infections or even fewer. The correct choice of reference strain for preclinical tests is of crucial importance for the clinical significance of the achieved results. In this paper we report our experience and recommendations regarding this issue.

Weak effect of metal type and ica genes on staphylococcal infection of titanium and stainless steel implants

Currently, ica is considered to be the major operon responsible for staphylococcal biofilm. The effect of biofilm on susceptibility to staphylococcal infection of different implant materials in vivo is unclear. The interaction of ica-positive (wild-type (WT)) and ica-negative (ica(-)) Staphylococcus aureus and Staphylococcus epidermidis strains with titanium and both smooth and rough stainless steel surfaces was studied by scanning electron microscopy in vitro and in a mouse tissue cage model during 2 weeks following perioperative or postoperative inoculation in vivo. In vitro, WT S. epidermidis adhered equally and more strongly than did WT S. aureus to all materials. Both WT strains, but not ica(-) strains, showed multilayered biofilm. In vivo, 300 CFUs of WT and ica(-)S. aureus led, in all metal cages, to an infection with a high level of planktonic CFUs and only 0.89% adherent CFUs after 8 days. In contrast, 10(6) CFUs of the WT and ica(-) strains were required for postoperative infection with S. epidermidis. In all metal types, planktonic numbers of S. epidermidis dropped to <100 WT, and adherent CFUs were low in WT-infected cages and absent in ica(-)-infected cages after 14 days. Perioperative S. epidermidis inoculation resulted in slower clearance than postoperative inoculation, and in titanium cages adherent WT bacteria survived in higher numbers than ica(-) bacteria. In conclusion, the metal played a minor role in susceptibility to and persistence of staphylococcal infection; the presence of ica genes had a strong effect on biofilm in vitro and a weak effect in vivo; and S. epidermidis was more pathogenic when introduced during implantation than after implantation.

Intramedullary nailing in femoral shaft fractures. Evaluation of a group of 101 cases

The Authors analyse the results of intramedullary nailing in a group of 101 femoral shaft fractures. Used nails: Universal Synthes (62 cases), Russel-Taylor (14), Gamma long (10), uncannulated femoral nail (9), cannulated femoral nail (4) and proximal femoral nail (2). Stabilisation of the femoral shaft fracture was possible using a reamed technique in 91 cases, unreamed in 10. All nails were locked. Dynamisation was performed in 35 cases and was not in 66. The fracture heal was faster with the reaming and dynamisation technique. Ten fractures were open (5 Gustilo I, 5 Gustilo II) and stabilisation with Universal Synthes nail (8 cases), Russel-Taylor nail (1) and Gamma long nail (1) was performed. No infection was detected. Lung embolism (6) and deep vein thrombosis (3) occurred only in the case of reamed nails. All results confirm the locking nail system as the best treatment in the shaft fractures, especially with new-generation nails.

Surgical aspects of infection involving osteosynthesis implants: implant design and resistance to local infection

Infection is still a major complication associated with surgery in orthopedics and traumatology. The implant design, the implant material, and the implantation technique may play essential roles in preventing infection. The goal of this paper is to discuss a series of experiments evaluating different aspects of both surgical procedures and implants. For this purpose, standardized local application of the human pathogen Staphylococcus aureus was performed in an animal model. Although these experimental results may be clinically relevant, direct extrapolation to clinical infection rates should be avoided.