Hydroxyapatite-coated external-fixation pins

Treatment of External Fixator Pin Tract Deep Infections With an Antibiotic "Sparkler"

Pin tract infections are virtually universal complications with the use of external fixation. While most are superficial and respond to oral antibiotics and local care, septic loosening may occur at the bone-pin interface, which may lead to instability of the fixator, catastrophic failure, fracture, and long-term osteomyelitis. Classification systems and prevention protocols have been developed to address this ubiquitous complication. Treatment of severe pin tract infections often requires debridement, parenteral antibiotics, and removal of the offending pin or the entire external fixator. In cases of osteomyelitic pin tracks, a sizable cavity is often present. We describe a simple technique for treatment of deep bone pin tract infection through the use of debridement, irrigation, and an antibiotic "sparkler," which is a specially prepared percutaneous implant of antibiotic laden bone cement.Levels of Evidence: Level 5.

Safety and Complication Rate of Ring External Fixation in the Foot and Ankle

External fixation is a powerful tool for foot and ankle surgeons. Currently, there is no consensus on true complication rate. The purpose of this study was to report our institution's complication rate of ring external fixation performed by a single surgeon. We retrospectively evaluated electronic medical record of 224 patients with 238 circular frames between 2009 and 2021 at a single institution. Minor complications were defined as a frame managed without early frame removal or return to operating room. Major complications were defined as early return to operative room or early removal defined by our institution as less than 2 months. We recorded over 1642 Ilizarov wires and 278 half pins; 10% (n = 163) of wires and 7% (n = 19) of half pins had a complication. We recorded 44% (n = 104) minor complications and 9% (n = 22) major complications. Minor complications average (mean) onset was 4 weeks, 89% (n = 93) involved wires, and 73% resolved without additional care. Major complications average (mean) onset was 3.7 weeks. Of these, 32% (n = 7) went on to successful revision. This revealed a significant correlation between minor complications and history of osteomyelitis (p < .05). While minor complications do appear high, this was due to wire irritation and local erythema which resolved without additional intervention. To better assess complications with external fixation the authors believe that wire irritation and pin site erythema should be recognized as an expected outcome. A better understanding of ring external fixation in foot and ankle surgery is vital to appropriate perioperative management and patient care.

Hydroxyapatite-coated compared with stainless steel external fixation pins did not show impact in the rate of pin track infection: a multicenter prospective study

PURPOSE

Infection at the pin site remains the most common complication of external fixators (EFs). It is known that hydroxyapatite (HA)-coated pins increase bone adhesion and may lead to reduced rates of reported infections. The present study compares the rates of pin track infection associated with stainless steel and HA-coated pins.

METHODS

This is a prospective, multicenter, nonrandomized, comparative intervention study among patients undergoing surgical treatment with EFs of any type between April 2018 and October 2021. Patients were followed up until the removal of the EF, or the end of the study period (ranging from 1 to 27.6 months). The definition of pin track infection was based upon the Maz-Oxford-Nuffield (MON) pin infection grading system.

RESULTS

Overall, 132 patients undergoing external fixation surgery were included. Of these, 94 (71.2%) were male, with a mean age of 36.9 years (SD ± 18.9). Infection of any type (score > 1) was observed in 63 (47.7%) patients. Coated and uncoated-pin track-infection occurred in 45.7% and 48.5% of patients, respectively (P= 0.0887). The probability of developing infection (defined as a score ≥ 2) adjusted for comorbidities and follow-up time was not statistically higher among those who received uncoated pins compared to those who received pins coated with HA (odds ratio (OR) = 1.56, 95% confidence interval (95% CI): 0.67-3.67, p <0.05).

CONCLUSION

In the present study, the external fixator pin infection rates were similar when using HA coating and standard steel pins.

Pin-site Infection: A Systematic Review of Prevention Strategies

Introduction

Circular frame fixation remains a key tool in the armamentarium of the limb reconstruction surgeon. One of the key drawbacks is the onset of pin-site infection (PSI). As a result of limited evidence and consensus of PSI prevention, a wide variation in practice remains.

Aim

The principal aim of this review is to synthesise primary research concerning all aspects of treatment regarded as relevant to PSI in frame constructs.

Materials and methods

Comparative studies until week 26, 2021, were included in the trial. Studies were included that concerned patients undergoing management of a musculoskeletal condition in which pin-site care is necessary for over 4 weeks.

Results

Eighteen studies over a 13-year period were captured using the search strategy. Sulphadiazine and hydrogen peroxide cleansing was found to reduce PSI, with the use of low-energy fine wires and hydroxyapatite (HA)-coated pins also associated with lower infection rate. The remainder of studies found no significant improvement across interventions.

Conclusion

There is no superiority between weekly and daily care. Low-energy pin-insertion technique had lower rates of infection. Sulphadiazine has positive results as a pin-care solution, but more research is necessary to determine the most effective care regime. Current literature is limited by absence of established definitions and by a lack of studies addressing all aspects of care relevant to PSI.

How to cite this article

Shields DW, Iliadis AD, Kelly E, et al. Pin-site Infection: A Systematic Review of Prevention Strategies. Strategies Trauma Limb Reconstr 2022;17(2):93–104.

Role of coatings and materials of external fixation pins on the rates of pin tract infection: A systematic review and meta-analysis

BACKGROUND

Infection at the pin tract is a frequent and feared complication of external fixators (EF). The type of pin material and coatings have been regarded as possibly influencing infection rates. Over the last 20 years, few prospective clinical studies and systematic reviews addressed the role of coated pins on the rate of pin site infection in human clinical studies.

AIM

To assess the EF literature over the past 20 years on the clinical benefits of pins manufactured from varied materials and coating systems and their possible role in pin tract infection rates.

METHODS

We performed a systematic review according to the PRISMA and PICOS guidelines using four scientific platforms: PubMed, LiLacs, SciELO, and Cochrane. We searched the literature for related publications over the past 20 years.

RESULTS

A literature search yielded 29 articles, among which seven met the inclusion criteria. These studies compared stainless-steel pins and pins coated with hydroxyapatite (HA), titanium and silver. The pin tract infection definitions were arbitrary and not standardized among studies. Most studies included a low number of patients in the analysis and used a short follow-up time. Three meta-analyses were carried out, comparing stainless steel vs silver pins, stainless steel vs HA-coated pins, and titanium vs HA-coated pins. None of this analysis resulted in statistically significant differences in pin tract infection rates.

CONCLUSION

Currently, no clinical evidence supports the advantage of EF pins manufactured with materials other than stainless steel or coated over uncoated pins in reducing the rates of pin tract infections. A standardized definition of pin tract infection in external fixation is still lacking.

Prospective evaluation of pin site infections in 39 patients treated with external ring fixation

Introduction: Pin site infection is a common complication to external ring fixation. While the aetiology is well described, monitoring of onset, location, and the distribution of infection among the pin sites still needs further attention. The present pilot study evaluates the feasibility of a prospective registration procedure for reporting, evaluating, and monitoring of pin site infections in patients treated with external ring fixation. This may promote communication between team members and assist decision-making regarding treatment. Methods: A total of 39 trauma, limb deformity, and bone infection patients (15 female, 24 males; mean age 49 years (range: 12–88)) treated with external ring fixation were followed in the outpatient clinic using the pin site registration tool. Pin site infection (Checketts and Otterburn (CO) grade, onset, location), use of oral or intravenous antibiotics, and any unplanned procedures due to pin sites complications (wire removal and/or replacement, premature frame removal, amputation, etc.) were registered until frame removal. Results: The mean (SD) frame time was 164 (83) d (range: 44–499). We performed 3296 observations of 568 pin sites. Pin infection was registered in 171 of the 568 pin sites (30 %), of which 112 (65 %) were categorized as CO 1, 42 (25 %) as CO 2, 9 (5 %) as CO 3, and 8 (5 %) as CO 5. Neither CO 4 nor CO 6 was observed. A total of 35 patients (90 %) encountered CO 1–3 at least once during the observation time, while 1 patient (2.5 %) developed a major infection at eight pin sites (CO 5). Antibiotics were administered to 22/39 (56 %) of the patients. Conclusion: In an effort to monitor pin site infections in this complex patient group and to ensure the best clinical outcomes, our registration procedure in the outpatient clinic helped to recognize pin site infections early and eased communication between team members providing a concise overview of the treatment course.

Overview of methods for enhancing bone regeneration in distraction osteogenesis: Potential roles of biometals

BACKGROUND

Distraction osteogenesis (DO) is a functional tissue engineering approach that applies gradual mechanical traction on the bone tissues after osteotomy to stimulate bone regeneration. However, DO still has disadvantages that limit its clinical use, including long treatment duration.

METHODS

Review the current methods of promoting bone formation and consolidation in DO with particular interest on biometal.

RESULTS

Numerous approaches, including physical therapy, gene therapy, growth factor-based therapy, stem-cell-based therapy, and improved distraction devices, have been explored to reduce the DO treatment duration with some success. Nevertheless, no approach to date is widely accepted in clinical practice due to various reasons, such as high expense, short biologic half-life, and lack of effective delivery methods. Biometals, including calcium (Ca), magnesium (Mg), zinc (Zn), copper (Cu), manganese (Mn), and cobalt (Co) have attracted attention in bone regeneration attributed to their biodegradability and bioactive components released during in vivo degradation.

CONCLUSION

This review summarizes the current therapies accelerating bone formation in DO and the beneficial role of biometals in bone regeneration, particularly focusing on the use of biometal Mg and its alloy in promoting bone formation in DO. Translational potential: The potential clinical applications using Mg-based devices to accelerate DO are promising. Mg stimulates expression of multiple intrinsic biological factors and the development of Mg as an implantable component in DO may be used to argument bone formation and consolidation in DO.

Investigation of Ag/a-C:H Nanocomposite Coatings on Titanium for Orthopedic Applications

One of the leading causes of failure for any bone implant is implant-associated infections. The implant-bone interface is in fact the crucial site of infection where both the microorganisms and cells compete to populate the newly introduced implant surface. Most of the work dealing with this issue has focused on the design of implant coatings capable of preventing infection while ignoring cell proliferation or vice versa. The present study is therefore focused on investigating the antibacterial and biological properties of nanocomposite coatings based on an amorphous hydrocarbon (a-C:H) matrix containing silver nanoparticles (AgNPs). a-C:H coatings with varying silver concentrations were generated directly on medical grade titanium substrates using a combination of a gas aggregation source (GAS) and a plasma-enhanced chemical vapor deposition (PE-CVD) process. The obtained results revealed that the surface silver content increased from 1.3 at % to 5.3 at % by increasing the used DC magnetron current in the GAS from 200 to 500 mA. The in vitro antibacterial assays revealed that the nanocomposites with the highest number of silver content exhibited excellent antibacterial activities resulting in a 6-log reduction of Escherichia coli and a 4-log reduction of Staphylococcus aureus after 24 h of incubation. An MTT assay, fluorescence live/dead staining, and SEM microscopy observations of MC3T3 cells seeded on the uncoated and coated Ti substrates also showed that increasing the amount of AgNPs in the nanocomposites had no notable impact on their cytocompatibility, while improved cell proliferation was especially observed for the nanocomposites possessing a low amount of AgNPs. These controllable Ag/a-C:H nanocomposites on Ti substrates, which simultaneously provide an excellent antibacterial performance and good biocompatibility, could thus have promising applications in orthopedics and other biomedical implants.

Relevant advances in bone lengthening research: a bibliometric analysis of the 100 most-cited articles published from 2001 to 2017

This study aimed to assess the scientific production of bone lengthening research by identifying the most-cited papers. All articles including the term 'bone lengthening' published between 2001 and 2017 were retrieved through the Web of Science database. The 100 most-cited articles on bone lengthening included a total of 4244 citations, with 414 (9.7%) citations in 2017. There was an average of 249.6 citations per year. The articles predominantly addressed biomechanics and bone formation (38). Different surgical techniques, including intramedullary nail (14), Ilizarov (nine), intramedullary skeletal kinetic distractor (ISKD) (six), Taylor spatial frame (6), the PRECICE device (three), and lengthening and submuscular locking plate (three), were the second most-studied topic. Most studies were therapeutic (58), whereas 30 studies were experimental investigations using animal models. Among the clinical studies, case series were predominant (level of evidence IV) (57). This study presents the first bibliometric analysis of the most relevant articles on bone lengthening. The list is relatively comprehensive in terms of identifying the top issues in this field. However, the most influential clinical studies have a poor level of evidence, although a slight tendency toward a better level of evidence has been observed in more recent years.

Pin tract infection prophylaxis and treatment

Pin tract infection in external fixation (ExFix) is a frequent finding which can eventually lead to loosening, osteomyelitis and loss of fixation. Its diagnosis is based on high empiricism and low validity, although it is possible to distinguish between minor and major infection. The first is limited to soft tissues, whereas the latter includes bone involvement. The rate of infection after conversion of external fixation to intramedullary nailing (IMN) is not well known. Unfortunately, papers referring to infection after the conversion of ExFix to intramedullary nailing (IMN) are of evidence level IV or V. It is suggested that conversion of ExFix to IMN should be carried out in a 2 step regimen. The time interval of 2 step regimen is uncertain although some authors have recommended to occur within 9 days. There is no consensus as to which prophylaxis protocol should be applied prior to conversion. In order to throw more light into this important issue, registries capturing important related parameters to the development of infection should be established.

Percutaneous pedestals in cochlear implantation

Percutaneous pedestals have been integral to the development of cochlear implants since 1969. By enabling direct electrical access to implanted electrodes or other devices, they allow optimization of control of stimulation strategies. Similarly, technology not validated for implantable use can be safely tested. These advantages have facilitated the development of cochlear implants and also resulted in their inclusion in trials investigating electronic implants developed for other organs. Surgery is straightforward, but post-operative care, in particular, skin-care is crucial to ensure complications are minimized. This review discusses the history of percutaneous pedestal use in cochlear implants and other electronic devices. Surgical technique, aftercare, and complications of surgery are discussed along with possibilities for future development.

[Application of Orthofix unilateral external fixator in the treatment of musculoskeletal tumors]

Objective

To investigate the surgical characteristics and preliminary effectiveness of Orthofix unilateral external fixator in the treatment of musculoskeletal tumors.

Methods

Twenty-two patients received Orthofix unilateral external fixator treatment for bone defect after tumor excision or complications after limb salvage surgery between June 2011 and March 2016. There were 11 males and 11 females with a median age of 23.5 years (range, 4-57 years). The bone defect or limb length discrepancy after tumor resection was at proximal femur in 6 cases, distal femur in 8 cases, diaphysis of femur in 3 cases, proximal tibia in 2 cases, and diaphysis of tibia in 3 cases. The external fixation was used for temporary fixation after reconstruction of bone defect in 10 cases [the length of bone defect was 6-19 cm (mean, 12.3 cm); using vascularized fibular graft in 2 cases, allograft bone and free fibular graft in 2 cases, allograft bone and autogenous bone graft in 5 cases, allograft bone reconstruction in 1 case]; bone distraction lengthening for limb length discrepancy in 5 cases [the length of shortening was 6.5-8.5 cm (mean, 7.5 cm)]; temporary fixation after open biopsy in 3 cases; bone transportation over locking plate in 1 case (the length of bone defect was 7.5 cm); fixation for preoperatively pathology fracture in 1 case; and joint distraction for dislocation after tumor ablation in 2 cases.

Results

All the patients were followed up 12-72 months (mean, 36 months). In 10 patients with bone defect reconstruction, the wearing external fixator time was 3-8 months (mean, 4.8 months); all got bone union with the healing time of 3-16 months (mean, 6.4 months); the Musculoskeletal Tumor Society 93 (MSTS 93) score was 73.3-93.3 (mean, 87.2); and no complication occurred during wearing external fixator. In 5 patients with bone distraction lengthening for limb length discrepancy, the wearing external fixator time was 7-15 months; 2 patients had axial deviation during distraction and2 had greenstick fracture after apparatus removal; pin site infection was observed in 2 cases with grade 1 and 1 case with grade 2 according to Checketts-Otterburn classification system; the MSTS 93 score was 80.0-96.7 (mean, 89.2). The remaining patients had no complications, the knee and ankle joint movement was normal.

Conclusion

Orthofix unilateral external fixator can be used in fixation for complex bone defect after tumor resection and to correct limb length discrepancy after limb salvage surgery.

Segmental Bone Loss Reconstruction Using Ring Fixation

Ring fixation is a powerful tool in the treatment of bone defects. The ability to create high-quality, biologically normal new bone of even massive proportions using distraction osteogenesis is a major reason for its success. In addition, ring fixation provides the ability to limit the risk of deep infection, improves flexibility in limb length control and alignment, and increases soft tissue coverage options. The drawbacks of ring fixation include long frame times, pin problems, risk of joint contractures, and difficult usage in areas with a large soft tissue envelope such as the thigh. Significant advancements such as hydroxyapatite coated pins, internal cable transport, multifocal transport, and combined techniques with internal fixation have helped increase the effectiveness of ring fixator use by minimizing many of the drawbacks. At present, ring fixation provides the most effective means of treatment for large bone defects in many clinic situations.

Ankle Distraction Arthroplasty: Indications, Technique, and Outcomes

Ankle distraction is an alternative to ankle arthrodesis or total ankle arthroplasty in younger patients with arthritis. Ankle distraction involves the use of external fixation to mechanically unload the ankle joint, which allows for stable, congruent range of motion in the setting of decreased mechanical loading, potentially promoting cartilage repair. Adjunct surgical procedures are frequently done to address lower-extremity malalignment, ankle equinus contractures, and impinging tibiotalar osteophytes. Patients can bear full weight during the treatment course. The distraction frame frequently uses a hinge, and patients are encouraged to do daily range-of-motion exercises. Although the initial goal of the procedure is to delay arthrodesis, many patients achieve lasting clinical benefits, obviating the need for total ankle arthroplasty or fusion. Complications associated with external fixation are common, and patients should be counseled that clinical improvements occur slowly and often are not achieved until at least 1 year after frame removal.

From prevention of pin-tract infection to treatment of osteomyelitis during paediatric external fixation

Pin-tract infection (PTI) is the most commonly expected problem, or even an almost inevitable complication, when using external fixation. Left unteated, PTI will progress unavoidably, lead to mechanical pin loosening, and ultimately cause instability of the external fixator pin-bone construct. Thus, PTI remains a clinical challenge, specifically in cases of limb lengthening or deformity correction. Standardised pin site protocols which encompass an understanding of external fixator biomechanics and meticulous surgical technique during pin and wire insertion, postoperative pin site care and pin removal could limit the incidence of major infections and treatment failures. Here we discuss concepts regarding the epidemiology, physiopathology and microbiology of PTI in paediatric populations, as well as the clinical presentations, diagnosis, classification and treatment of these infections.

Definitive Management of Distal Tibia and Simple Plafond Fractures With Circular External Fixation

Obtaining optimal results in the treatment of extraarticular distal tibia fractures can be challenging. Plate and screw and intramedullary fixation have proven to be effective treatments, but are associated with significant complication rates when used for open fractures and patient with severe medical comorbidities. External fixation is a third alternative that is less often employed, but provides a very effective means of treatment. Circular external fixation offers great flexibility in obtaining anatomic alignment and stable fixation for even the most challenging distal tibia fractures. In addition, it provides advantages in limiting the risk of deep infection, dealing with bone loss, and obtaining soft tissue coverage. The greater ease of treatment and potential economic advantage in patient cohorts with low complication rates, such as closed fractures, supports the preferential use of internal fixation. However, circular external fixation may be the preferred treatment for patients with higher-grade open fractures, a poor soft tissue envelope with limited fixation options distally, and major comorbidities (diabetes, immune deficiency) with an associated high risk of complications.

Hexapod External Fixation of Tibia Fractures in Children

Most tibia fractures in children can be treated nonoperatively. For fractures that do require surgery, however, the most common methods of management include plating or flexible nail insertion. Some fracture patterns, such as periphyseal fractures, fractures with bone and/or soft tissue loss, or fractures with delayed presentation, are not easily amenable to these techniques. Hexapod external fixators are especially helpful in these difficult cases. The purpose of this review is to discuss the principles of performing hexapod circular external fixation applied to pediatric tibia fractures. Some of the additional capabilities of the hexapod external fixator will also be highlighted.

Standards of external fixation in prolonged applications to allow safe conversion to definitive extremity surgery: the Aachen algorithm for acute ex fix conversion

External fixation has become an important tool in orthopedic surgery. Technology has improved the design and material as well as the construct of the fixator. As most patients are converted from external fixation to definite stabilization during later clinical course, prevention of complications such as infection is of high importance. Based on the current literature, principles of temporary external fixation were summarized. We focused on minimizing the risk of infection and introduce a standardized algorithm how to proceed when converting from external to internal fixation, which also was examined for effectiveness.

Pin-site care: can we reduce the incidence of infections?

BACKGROUND

This study was conducted to determine the pin-site care protocols currently in use and to analyse their effectiveness and outcomes.

METHODS

PubMed, the Cochrane Library and Embase databases were screened for manuscripts that described comparative studies of different methods of pin-site care and referred to complications related to any kind of external fixator application.

RESULTS

A total of 369 manuscripts were screened and only 13 of these met the inclusion criteria evaluating different protocols of pin-site care. This review is based on a total of 574 patients. Infection rates were very variable depending on the type of implant used and the protocol of pin-site care applied.

CONCLUSIONS

None of the different protocols of pin-site care that were evaluated in this study were associated with a 0% infection rate. There is currently no consensus in the international literature about which protocol should be applied universally. Meticulous surgical technique during pin insertion and implementation of one of the existing protocols of pin-site care are the mainstay of prevention and/or reduction of the incidence of pin-site infections.

"Ilizarov" external fixation: what the radiologist needs to know

Circular external fixation, including the Ilizarov method, is a complex and often long-term treatment used for various orthopedic conditions. Due to the complexity of the hardware, frequent postoperative complications, and the potential for significant radiographic changes between visits, it is important for the radiologist to have a basic understanding of ring fixators. This publication reviews indications for external fixation versus internal fixation and whether to use a circular or uniplanar construct if external fixation is elected. Indications for and characteristics of static circular frames, intercalary and non-intercalary transport frames, and deformity circular frames will also be discussed. While general similarities exist between frame types, each has unique components of which the radiologist must be aware. An emphasis is placed on the important features and complications that arise during treatment.

The effect of HIV infection on the incidence and severity of circular external fixator pin track sepsis: a retrospective comparative study of 229 patients

Pin track sepsis is a common complication of circular external fixation. HIV status has been implicated as an independent risk factor for the development of pin track infection and has been cited as a reason not to attempt complex limb reconstruction in HIV-positive patients. This retrospective review of patients treated with circular external fixators looked at the incidence of pin track sepsis in HIV-positive, HIV-negative and patients whose HIV status was unknown. The records of 229 patients, 40 of whom were HIV-positive, were reviewed. The overall incidence of pin track sepsis was 22.7 %. HIV infection did not affect the incidence of pin track sepsis (p = 0.9). The severity of pin track sepsis was not influenced by HIV status (p = 0.9) or CD4 count (p = 0.2). With the employment of meticulous pin insertion techniques and an effective postoperative pin track care protocol, circular external fixation can be used safely in HIV-positive individuals.

Prevention of infection in external fixator pin sites

Infection in external fixator pins is known to be a significant problem, with incidences between 3% and 80% reported in the literature. An infection occurs when planktonic bacteria adhere to external fixator pins and subsequently produce a biofilm which protects the bacteria from host defences. The most commonly implicated organisms are Staphylococcus aureus and Staphylococcus epidermidis. Once an infection occurs, treatment is difficult. Systemic antibiotics have limited benefits and considerable side-effects. The only definitive management is removal of the pin. This review will consider the current and potential future strategies for reducing pin site infection. Techniques to prevent infection must prevent bacterial adhesion, allow good osteointegration and have a low toxicity. Current areas of interest reviewed are titanium-copper alloys, nanosilver coatings, nitric oxide coatings, chitosan coatings, chlorhexidine and iodine, hydroxyapatite and antibiotic coatings. At present there is no consensus on the prevention of pin site infection, and there is a paucity of randomized controlled trials on which to draw a conclusion. Whilst a number of these strategies have potential future use, many of the above strategies need further studies in animal models to ensure no cytotoxicity and prevention of osteointegration. Following this, well-designed randomized controlled clinical trials are required to give future ways to prevent external fixator pin site infections.

Hydroxyapatite-coated external fixation pins

The aim of this review is to report on studies of hydroxyapatite-coated external fixation pins as a solution to enhance pin fixation. In a highly loaded animal study, three tapered pin types were compared: Type A uncoated, Type B coated with hydroxyapatite and Type C coated with titanium. There was a 13-fold increase in the extraction torque of Type B pins compared with Type A, and a twofold increase compared with Type C pins. Extraction torque was significantly lower compared with the corresponding insertion torque in both Types A (p < 0.001) and C (p = 0.003). Conversely, with the hydroxyapatite-coated pins there was no difference between extraction and insertion torque. In a clinical study of 76 external fixation pins in 19 patients treated with hemicallotasis for osteoarthritis on the medial side of the knee, pin insertion and extraction torque forces were measured. The patients were randomized to be treated with either standard tapered pins or tapered pins coated with hydroxyapatite. Extraction torque of the hydroxyapatite-coated pins was higher than the extraction torque of the standard pins in both cancellous and cortical bone (p < 0.005). In a prospective, randomized clinical study of osteoporotic wrist fractures, extraction torque of the coated pins was higher than with standard pins (p < 0.0001). These studies demonstrate that with the use of hydroxyapatite-coated pins, no deterioration of pin fixation occurs, and that there is no significant pin loosening and infection, regardless of bone type and loading conditions.

Improved bonding of partially osteomyelitic bone to titanium pins owing to biomimetic coating of apatite

Increased fixation strength of the bone-pin interface is important for inhibiting pin loosening after external fixation. In a previous study, an apatite (Ap) layer was formed on anodically oxidized titanium (Ti) pins by immersing them in an infusion fluid-based supersaturated calcium phosphate solution at 37 °C for 48 h. In the present study, an Ap layer was also successfully formed using a one-step method at 25 °C for 24 h in an infusion fluid-based supersaturated calcium phosphate solution, which is clinically useful due to the immersion temperature [corrected]. After percutaneous implantation in a proximal tibial metaphysis for four weeks in rabbits (n = 20), the Ti pin coated with the Ap layer showed significantly increased extraction torque compared with that of an uncoated Ti screw even with partial osteomyelitis present, owing to dense bone formation on the Ap layer in the cortical and medullary cavity regions. When the infection status was changed from "no osteomyelitis" to "partial osteomyelitis," the extraction torque in the Ap group with "partial osteomyelitis" was almost identical to that for "no osteomyelitis" cases. These results suggest that the Ap layer formed by the room temperature process could effectively improve the fixation strength of the Ti pin for external fixation clinically even with partial osteomyelitis present.

Prevention and management of external fixator pin track sepsis

Pin track-associated complications are almost universal findings with the use of external fixation. These complications are catastrophic if it leads to the failure of the bone–pin interface and could lead to pin loosening, fracture non-union and chronic osteomyelitis. Strategies proposed for the prevention and management of pin track complications are diverse and constantly changing. Prevention of external fixation pin track infection is a complex and ongoing task that requires attention to detail, meticulous surgical technique and constant vigilance.

Stability with unilateral external fixation in the tibia

Unilateral external fixation can be used in the provisional or definitive treatment of tibial fractures. A properly applied fixator allows bony and soft tissue stability, whereas an improperly applied fixator achieves neither and can be a hindrance. The principles for the successful application of monolateral external fixation, including the rationale for choosing this type of device, the assembly of its components and deciding on planes of application, are discussed in this article.

Decreasing bacterial colonization of external fixation pins through nitric oxide release coatings

OBJECTIVE

Bacterial infection of the pin tract represents the most common complication associated with external fixation. This study was designed to evaluate the antibacterial activity of nitric oxide (NO)-releasing xerogel films applied to commercially pure titanium pins in a rat model.

METHODS

Pins were coated with xerogel solution through a dip-coating procedure. Half of the xerogel-coated implant pins were modified into NO donors and served as the NO-releasing group, whereas the remaining pins were left unmodified to serve as non-NO-releasing xerogel-coated controls. Acid-etched pins served as uncoated controls. Animal selection was randomized and every rat had one pin from each of the three groups randomly allocated to the third, fourth, or fifth tail vertebrae. Quantification of bacterial infection was performed 48 days postoperatively and the tissue-implant interface was inspected for clinical signs of infection on Days 14 and 28 postimplantation.

RESULTS

Pin tract bacterial colony counts of the NO-releasing group (170,000 ± 181,000) were significantly lower than both the xerogel-coated group (677,000 ± 675,000) and the control group (1,181,000 ± 2,717,000) 48 days postoperatively (P < 0.05). No significant difference in colony counts was observed between the xerogel-coated group and the control group. The NO-releasing group also had significantly fewer clinical signs of infection than both the coated and the control groups on postoperative Day 28 (P < 0.05).

CONCLUSION

The application of NO-releasing xerogel coatings can inhibit bacterial colonization of external fixation pins both during the initial postsurgical period and up to 48 days postimplantation.

Effects of Ti2448 half-pin with low elastic modulus on pin loosening in unilateral external fixation

The objective of this study was to compare the benefits of titanium 2448 (Ti2448) half-pin and titanium-6 aluminium-4 vanadium (TAV) half-pin on reducing pin loosening during external fracture fixation. Although having similar strength, Ti2448 half-pin had even lower elastic modules (33 GPa) when compared with TAV half-pin (110 GPa), which was similar to that of cortical bone (20 GPa). In the external fixation of tibial model fractures and canine cadaveric tibia fractures, Ti2448 half-pin had greater recoverable deformation and less stress concentration at the pin-bone interface in compression, torsion, and four-points bending test. Then, tibial fractures were created in 24 dogs and stabilized with four half-pins of either Ti2448 or TAV in each animal. At 4 and 8 weeks postoperatively, fracture healing and pin loosening was assessed by radiographic grading scale. The scores of Ti2448 group were significantly higher than those of TAV group. Micro-CT analysis also indicated larger quantity and higher quality of newly formed bone at pin-bone interface in Ti2448 group. Histology observation showed the newly formed bone integrated well into the threads of Ti2448 half-pins. In contrast, there was a layer of necrotic tissue between the bone tissue and TAV half-pin at pin-bone interface in TAV group. The extraction torque values of Ti2448 half-pins near the fracture line were significantly higher than those TAV pins. In conclusion, the Ti2448 half-pin with low elastic modulus could enhance osseointegration and reduce pin loosening when compared with TAV half-pin. It is a promising biomaterial for constructing external fixation system in clinical application.

External fixation for stable and unstable intertrochanteric fractures in patients older than 75 years of age: a prospective comparative study

OBJECTIVE

External fixation has been advocated as an alternative treatment method of intertrochanteric fractures in elderly and high-risk patients. However, the efficacy of the technique in all fracture types has not been clearly defined. The null hypothesis of this study was that external fixation showed equal results in either stable or unstable intertrochanteric fractures in patients older than 75 years of age.

DESIGN

Prospective comparative study.

SETTING

Level I trauma center.

PATIENTS

Between July 2006 and June 2007, 100 patients older than 75 years of age (mean, 82.3 ± 5.2 years) and American Society of Anesthesiologists 3 or 4 who sustained an isolated intertrochanteric fracture met the inclusion criteria for the study. The patients were followed up at regular intervals until 1 year postoperatively.

INTERVENTION

All fractures were stabilized with external fixation under epidural anaesthesia. The patients were divided in two groups according to the Orthopaedic Trauma Association classification system for intertrochanteric fractures. Types A1.1, A1.2, A1.3, and A2.1 fractures were considered stable (Group A) and Types A2.2, A2.3, A3.1, A.3.2, and A.3.3 unstable (Group B). Fifty patients were collected in each group.

MAIN OUTCOME MEASUREMENTS

Operation and hospitalization time, union time, complication rate, Harris hip score, and patients' walking status were evaluated.

RESULTS

The median operative time was 17 minutes (range, 15-50 minutes) in Group A and 21.5 minutes (range, 15-60 minutes) in Group B (P < 0.001). The median hospitalization time was 5 days (range, 2-11 days) in Group A and 7 days (range, 4-17 days) in Group B (P < 0.001). The average union time was 11.24 ± 1.66 weeks (range, 9-16 weeks) for Group A and 14.1 ± 1.63 weeks (range, 10-17 weeks) for Group B (P < 0.001). The overall complication rate was 8% for the stable fractures and 26% for the unstable fractures (P = 0.03). The rate of varus collapse in unstable fractures was 11%. The median Harris hip score was 75 points (range, 28-100) in Group A and 68 points (range, 25-99) in Group B (P = 0.006). No difference was found between groups in terms of mortality (P = 0.913) or walking status (P = 0.736).

CONCLUSION

External fixation for the treatment of Orthopaedic Trauma Association Types A2.2, A2.3, A3.1, A.3.2, and A.3.3 intertrochanteric fractures in the elderly was associated with prolonged union time, increased incidence of varus position of the fracture site, and inferior functional outcome. Therefore, it should be used with caution in the geriatric population with an unstable intertrochanteric fracture.

Clinical benefit of hydroxyapatite-coated pins compared with stainless steel pins in external fixation at the wrist: a randomised prospective study

BACKGROUND

The purpose of this study was to determine the clinical benefit of hydroxyapatite (HA)-coated pins compared with standard stainless steel pins in external fixators applied for unstable fractures of the distal radius.

METHODS

A total of 40 patients (160 pins) with unstable wrist fractures were randomised for uniplanar fixator treatment with the use of identically designed, commercially available pins either composed of stainless steel (steel group) (n = 20) or coated by hydroxyapatite (HA group) (n = 20). Each pin site was clinically evaluated concerning erythema and grade of drainage as well as pain intensity (numeric rating scale (NRS) 0–10) and, additionally, radiological assessment was performed concerning pin-loosening/infection as well as fracture healing at T1 (Ø18 days), T2 (Ø44 days) and T3 (Ø65 days). In case of pintrack complication, the patient was followed continuously. The need for intensified pin-site care, oral or intravenous antibiotic medication, re-admission for additional surgery and premature fixator removal was documented. Bone mineral density (BMD) was determined by dual energy X-ray absorptiometry. At fixator removal (T2), the pin-extraction strength was measured by the use of an electronic torque wrench.

RESULTS

Two pin-track infections requiring daily pin-site care and oral antibiotics occurred in the HA group (2.6%) compared with four in the steel group (5.3%) (p = 0.601) and although a trend towards a superior performance of HA pins was detectable, the majority of clinical pin-site-parameters were comparable in both groups. At the end of the fixator therapy, the HA group showed a non-significant lower rate of loose pins (n(steel group) = 9; n(HA group) = 6; p = 0.864) and both hydroxyapatite-coated pins showed at the radius a significantly stronger pin-bone bonding measured by the torque wrench (p(proximal radius pin) = 0.007; p(distal radius pin) = 0.031). Except for elderly patients of the steel group (p = 0.018), all demographic-, health- and injury-related data including BMD were not correlated to any type of pin-site complication in both groups (p > 0.05). Since all fracture healed uneventfully without any type of additional surgery, the number of patients suffering clinically relevant pin-related complications showed no significant difference between both groups (p = 0.707).

CONCLUSIONS

The use of HA-coated pins compared with standard stainless-steel pins in external fixation for unstable wrist fractures yields only a trend towards a superior clinical outcome.

Nanotextured titanium surfaces for enhancing skin growth on transcutaneous osseointegrated devices

A major problem with transcutaneous osseointegrated implants is infection, mainly due to improper closure of the implant-skin interface. Therefore, the design of transcutaneous osseointegrated devices that better promote skin growth around these exit sites needs to be examined and, if successful, would clearly limit infection. Due to the success already demonstrated for orthopedic implants, developing surfaces with biologically inspired nanometer features is a design criterion that needs to be investigated for transcutaneous devices. This study therefore examined the influence of nanotextured titanium (Ti) created through electron beam evaporation and anodization on keratinocyte (skin-forming cell) function. Electron beam evaporation created Ti surfaces with nanometer features while anodization created Ti surfaces with nanotubes. Conventional Ti surfaces were largely micron rough, with few nanometer surface features. Results revealed increased keratinocyte adhesion in addition to increased keratinocyte spreading and differences in keratinocyte filopodia extension on the nanotextured Ti surfaces prepared by either electron beam evaporation or anodization compared to their conventional, unmodified counterparts after 4h. Results further revealed increased keratinocyte proliferation and cell spreading over 3 and 5days only on the nanorough Ti surfaces prepared by electron beam evaporation compared to both the anodized nanotubular and unmodified Ti surfaces. Therefore, the results from this in vitro study provided the first evidence that nano-modification techniques should be further researched as a means to possibly improve skin growth, thereby improving transcutaneous osseointegrated orthopedic implant longevity.

Ilizarov principles of deformity correction

Ilizarov frames provide a versatile fixation system for the management of bony deformities, fractures and their complications. The frames give stability, soft tissue preservation, adjustability and functionality allowing bone to realise its full osteogenic potential. It is important that we have a clear and concise understanding of the Ilizarov principles of deformity correction to best make use of this fixation system. In this review article, the history of Ilizarov frame, the basic sciences behind it, the mechanical principles governing its use and the clinical use of the fixation system are discussed.

A single dose zoledronic acid enhances pin fixation in high tibial osteotomy using the hemicallotasis technique. A double-blind placebo controlled randomized study in 46 patients

INTRODUCTION

Bisphosphonates have been shown to reduce osteoclastic activity and enhance pin fixation in both experimental and clinical studies. In this prospective, randomized study of high tibial osteotomy using the hemicallotasis (HCO) technique, we evaluate whether treatment by one single infusion of zoledronic acid can enhance the pin fixation.

MATERIALS AND METHODS

46 consecutive patients (35-65 years) were operated on for knee osteoarthritis by the HCO technique. After the osteotomy, two hydroxyapatite-coated pins were inserted in the metaphyseal bone and two non-coated pins in the diaphyseal bone. The insertion torque was measured by a torque force screw driver. Four weeks postoperatively, the patients were randomized to either one infusion of zoledronic acid or sodium chloride intravenously. At time for removal of the pins, the extraction torque forces of the pins were measured.

RESULTS

All osteotomies healed and no difference was found in time to healing. The mean extraction torque force in the non-coated pins in the diaphyseal bone was doubled in the zoledronic treated group (4.5 Nm, SD 2.1) compared to the placebo group (2.4 (SD 1.0, p<0.0001). The mean extraction torque forces of the hydroxyapatite-coated pins in the metaphyseal bone were similar in the zoledronic acid group (4.7 Nm, SD 1.3) and in the placebo group (4.0 Nm, SD 1.3).

DISCUSSION

A single infusion of zoledronic acid improved twofold the fixation of non-coated pins in diaphyseal bone. Bisphosphonates might be an alternative to hydroxyapatite-coated pins in nonosteoporotic bone.

The influence of hydroxyapatite coating of external fixator pins on pin loosening and pin track infection: a systematic review

OBJECTIVE

The primary objective of this systematic review of published randomised controlled trials was to evaluate whether there was a clinical benefit in terms of pin loosening and pin track infection, or deep infection, associated with hydroxyapatite coating of external fixator pins. The secondary objective was to evaluate whether there was a clinical benefit in terms of loss of alignment or malunion associated with hydroxyapatite coating of external fixator pins.

METHODS

Studies included were identified by a PubMed search for relevant randomised controlled trials on the 20th of December 2007. A systematic review was performed.

RESULTS

All of the studies concluded that there was significantly less pin loosening in the HA-coated groups although the definition of loosening was based on different criteria. However, there was insufficient evidence to properly evaluate the clinical benefit in terms of the numbers needed to treat to avoid premature pin removal. There was also insufficient evidence to evaluate whether any clinical benefit is gained by using HA-coated pins with respect to deep infection and malunion.

CONCLUSION

A well designed large randomised controlled trial is required to determine the numbers needed to treat with HA-coated pins to reduce the incidence of clinically relevant pin loosening, axial deformity and pin track or deep infection.

Can we improve fixation and outcomes? Use of bone substitutes

Hip fractures secondary to osteoporosis are common in the elderly. Stabilizing these fractures until union is achieved is a challenge due to poor bone stock and insufficient purchase of the implant to the bone. The reported high rate of complications has prompted extensive research in the development of fixation techniques. Furthermore, manipulation of both the local fracture environment in terms of application of growth factors, scaffolds, and mesenchymal cells and the systemic administration of agents promoting bone formation and bone strength has been considered as a treatment option with promising results. There are only a few evidence-based studies reporting on fixation augmentation techniques. This article reports on the efficacy of bone graft substitutes for the fixation of hip fractures, in particular calcium phosphates, which have been used as granules, cements, and implant coatings.

Chitosan-coated stainless steel screws for fixation in contaminated fractures

Stainless steel screws and other internal fixation devices are used routinely to stabilize bacteria-contaminated bone fractures from multiple injury mechanisms. In this preliminary study, we hypothesize that a chitosan coating either unloaded or loaded with an antibiotic, gentamicin, could lessen or prevent these devices from becoming an initial nidus for infection. The questions investigated for this hypothesis were: (1) how much of the sterilized coating remains on the screw with simulated functional use; (2) is the unloaded or loaded chitosan coating bacteriostatic and biocompatible; and (3) what amount and rate does an antibiotic elute from the coating? In this study, the gentamicin eluted from the coating at a detectable level during 72 to 96 hours. The coating was retained at the 90% level in simulated bone screw fixation and the unloaded and loaded chitosan coatings had encouraging in vitro biocompatibility with fibroblasts and stem cells and were bacteriostatic against at least one strain of Staphylococcus aureus. The use of an antibiotic-loaded chitosan coating on stainless steel bone screws and internal fixation devices in contaminated bone fracture fixation may be considered after optimization of antibiotic loading and elution and more expanded in vitro and in vivo investigations with other organisms and antibiotics.

Titanium alloy pins versus stainless steel pins in external fixation at the wrist: a randomized prospective study

BACKGROUND

Pin-track complications remain the most troublesome disadvantages of external fixation. The purpose of this study was to compare pin-related complications and pain levels after the use of external fixation for the stabilization of distal radial fractures with pins composed of two different materials.

METHODS

In a prospective trail 80 patients (320 pins) with unstable distal radial fracture were randomized for standard small AO-external fixator treatment with the use of identical pin geometry either composed of stainless-steel (Ss) (n = 40) or titanium alloy (Ti6Al4V) (n = 40). The patients were followed at biweekly intervals until the external fixators were removed (44 days after surgery). The patients were evaluated with regard to erythema, drainage, cellulitis, occurrence of pain at each pin-site, clinical or radiographic evidence of pin-loosening, the need for antibiotics, and the need for pin removal before fracture-healing due to infection.

RESULTS

The complication rate was 21%, and age was found to be significantly associated with an increased risk of pin-loosening (p = 0.003). There were no significant differences among the two groups with regard to the prevalence of pin-site complications. However, the rate of premature removal of fixator because of severe pin-track infection (5% vs. 0%) and the rate of pin-loosening (10% vs. 5%) was higher in the Ss-pin group. Furthermore, pain values were significantly reduced in the Ti6Al4V-pin group.

CONCLUSIONS

The use of Ti6Al4V-pin external fixator in distal radial fractures yields a trend of reduced pin-related complications and significantly reduced pain levels than does the Ss-pin fixator.

Use of chlorhexidine-impregnated patch at pin site to reduce local morbidity: the ChIPPS Pilot Trial

Pin tract infection is one of the most common complications associated with the use of external fixation. While some studies have identified the potential benefit of chlorhexidine gluconate-impregnated polyurethane dressings to reduce the incidence of catheter-related bloodstream infections, we are unaware of any published studies that evaluate the effectiveness of similar technologies in reducing the risk for external-fixation-related pin tract infections. Therefore, the purpose of this study was to evaluate the effectiveness of chlorhexidine gluconate-impregnated polyurethane dressing in reducing percutaneous-device-related skin colonisation and local infections. In this initial retrospective cohort, data were abstracted for two groups of consecutive patients undergoing surgery involving external fixation at an interdisciplinary foot and ankle surgical unit. All patients received surgical treatment of their foot/ankle pathology along with application of a hybrid external fixator. Twenty patients (45% male, age 54.5 +/- 3.69 years) received chlorhexidine gluconate-impregnated polyurethane dressing and twenty (55% male, age 55.8 +/- 3.22 years) received standard pin care. There was a significantly higher rate of pin tract infection in patients who received standard pin care compared with those who received chlorhexidine gluconate-impregnated polyurethane dressings (25% versus 0%, P = 0.047). There was no significant difference in any of the descriptive study characteristics (age, gender, diabetes and presence of neuropathy). The results of this initial study suggest that chlorhexidine gluconate-impregnated polyurethane dressing may be effective to reduce the incidence of pin tract infections and help decrease morbidity associated with external fixation.

Fixation of HA-coated unicortical locking screws in a sheep gap model: a comparative biomechanical study

OBJECTIVES

To evaluate whether fixing a locking compression plate (LCP) with hydroxyapatite (HA)-coated screws provides improved biomechanical fixation and healing compared with standard screws under loaded conditions.

METHODS

Ten sheep were randomly divided into 2 groups. A resection osteotomy of 8 mm was performed in the sheep's right tibiae. Five tibiae were fixed with a 9-hole LCP and 8 standard unicortical locking screws (Group Non-HA), and 5 tibiae were fixed with a 9-hole LCP and 8 HA-coated unicortical locking screws (Group HA). All screws were implanted at the same insertion torque of 4000 Nmm. Three months after surgery, all the sheep were euthanized. Bone segments after screw removal were randomly chosen from each group for histologic analysis (Group Non-HA=5, Group HA=5).

RESULTS

Mean screw extraction torque was 438+/-288 Nmm in Group Non-HA (n=40) and 2317+/-657 Nmm in Group HA (n=40) (P<0.0005). The tibial torque resistance of the resected tibiae was 24+/-8 Nm in Group Non-HA (n=5) and 31+/-3 in Group HA (n=5) (P=0.045). In Group Non-HA, histology showed bone resorption and fibrous tissue encapsulation in all the samples, but this was not found in any of the Group HA samples.

CONCLUSIONS

This study shows that an LCP with HA-coated screws provides improved biomechanical fixation than an LCP with similar standard screws as shown by a 5-fold greater screw extraction torque (P<0.0005). Furthermore, the higher tibial torque resistance is potentially beneficial for improved gap healing, as shown by higher tibial torque resistance.

Comparison of insertion characteristics of two types of hydroxyapatite-coated and uncoated positive profile transfixation pins in the third metacarpal bone of horses

OBJECTIVE

To determine the effect of 2 hydroxyapatite pin coatings on heat generated at the bone-pin interface and torque required for insertion of transfixation pins into cadaveric equine third metacarpal bone.

SAMPLE POPULATION

Third metacarpal bone pairs from 27 cadavers of adult horses.

PROCEDURES

Peak temperature of the bone at the cis-cortex and the hardware and pin at the trans-cortex was measured during insertion of a plasma-sprayed hydroxyapatite (PSHA)-coated, biomimetic hydroxyapatite (BMHA)-coated, or uncoated large animal transfixation pin. End-insertional torque was measured for each pin. The bone-pin interface was examined grossly and histologically for damage to the bone and coating.

RESULTS

The BMHA-coated transfixation pins had similar insertion characteristics to uncoated pins. The PSHA-coated pins had greater mean peak bone temperature at the cis-cortex and greater peak temperature at the trans-cortex (70.9 +/- 6.4(o)C) than the uncoated pins (38.7 +/- 8.4(o)C). The PSHA-coated pins required more insertional torque (10,380 +/- 5,387.8 Nmm) than the BMHA-coated pins (5,123.3 +/- 2,296.9 Nmm). Four of the PSHA-coated pins became immovable after full insertion, and 1 gross fracture occurred during insertion of this type of pin.

CONCLUSIONS AND CLINICAL RELEVANCE

The PSHA coating was not feasible for use without modification of presently available pin hardware. The BMHA-coated pins performed similarly to uncoated pins. Further testing is required in an in vivo model to determine the extent of osteointegration associated with the BMHA-coated pins in equine bone.

The mechanics of external fixation

External fixation has evolved from being used primarily as a last resort fixation method to becoming a main stream technique used to treat a myriad of bone and soft tissue pathologies. Techniques in limb reconstruction continue to advance largely as a result of the use of these external devices. A thorough understanding of the biomechanical principles of external fixation is useful for all orthopedic surgeons as most will have to occasionally mount a fixator throughout their career. In this review, various types of external fixators and their common clinical applications are described with a focus on unilateral and circular frames. The biomechanical principles that govern bony and fixator stability are reviewed as well as the recommended techniques for applying external fixators to maximize stability. Additionally, we have illustrated methods for managing patients while they are in the external frames to facilitate function and shorten treatment duration.