33rd Annual Scientific Meeting proceedings

Introduction
Open fractures are associated with an increased risk of complications such as infection and nonunion with the incidence of such complications being directly influenced by the emergency treatment approach. The goals of open fracture management are prevention of infection, fracture union and restoration of function. These goals are best achieved when a series of steps are followed; fracture classification, early administration of systemic antibiotics, thorough irrigation, surgical debridement, wound management, stable fracture fixation, thorough rehabilitation and adequate follow-up. While there is little debate regarding the importance of these steps, how time-sensitive each procedure is remains contentious.

In the human medical field, clinical guidelines for the management of open fractures provide evidence-based recommendations, offering a framework that optimises outcomes. Several guideline documents exist with extensive overlap between them; in fact, one group indicated that the overlap in recommendations was 89% between four frequently used schemes.¹ Due to this extensive agreement, for the purposes of this session we will refer to one – The British Orthopaedic Association Standards for Trauma and Orthopaedics on open fractures (BOAST-4).²

Unfortunately, in the veterinary field, no such guidelines have been developed and evidence in the small animal field regarding open fracture management is sparse. Most of the numbers referred to here stem from a recently completed retrospective study.³ In this session we will use the current small animal information available, in conjunction with data from the human medical literature to explore how time-sensitive each component of open fracture management is.  

Patient Evaluation and Stabilisation
Patients presenting with an open fracture must be carefully assessed. Open fractures are typically the result of high-energy trauma and therefore the potential for concomitant injuries should be investigated before addressing injuries to the limbs. Elaboration on this aspect of care is beyond the scope of this session but while this is ongoing, and until irrigation and debridement can be performed, a temporary sterile dressing should be placed to limit the risk for nosocomial infection.

Once stabilised, a full examination of the affected limb is performed. As a minimum, emergent management should include:

• Assessment and documentation of the neurovascular status of the injured limb
• Initial fracture classification
• Systemic antibiotic therapy
• Placement of sterile lubricant within the wound, wide clipping of hair and cleansing of the peri-wound area
• Application of a sterile dressing
• Gross realignment of the fractured limb and immobilisation if appropriate

Fracture Classification
Open fractures vary in severity depending on the mechanism and energy of injury and this can influence both management strategy and outcome. Classification systems have been developed to describe the injury, guide treatment, determine prognosis and compare treatment methods. The Gustilo-Anderson classification has been extensively used in both human and veterinary medicine,⁴ however significant limitations are recognised including poor inter-observer reliability and a tendency to underestimate damage to muscle and bone. An alternative system developed by the Orthopaedic Trauma Association in 2010 has been shown to be superior to the Gustilo-Anderson system in relation to the detail of description, prognostic value and interobserver reliability.

In the human field it is recognised that the severity of injury, and hence the fracture classification, will be better appreciated in the operating room following wound exploration and debridement, and that when fractures are classified in the emergency room, misclassification is possible. Similar concerns were raised in a recent veterinary study evaluating gunshot injuries.⁵ Despite the limitations of fracture classification in emergent situations this is considered a time-critical step as it will have implications for decision-making regarding several other time-sensitive aspects of management including antibiotic choice, volume of irrigation and timing of debridement.

Systemic Antibiotic Therapy
Infection is a dreaded sequela of open fractures and can be associated with serious consequences including multiple surgeries, amputation and even death. Preventing infection from developing is the cornerstone of acute care for patients with open fractures. Early antibiotic administration is key because most patients with open fractures have wounds contaminated with microorganisms and from a pragmatic approach, the earlier antibiotics are delivered, the slower bacterial growth occurs, thus reducing risks of developing infection. Systemic antibiotics should be administered in all patients with open fractures and local antibiotics may be considered in select cases. The role of antibiotics in reducing infection was demonstrated in a prospective randomised study;⁶ the infection rate when cephalothin was administered before debridement was 2.3% compared with 13.9% when no antibiotics were used.

Early antibiotic administration is very important with delayed administration of the first dose of antibiotic prophylaxis increasing the risk of infection markedly. Patzakis and Wilkins⁷ initially reported that a delay longer than three hours from injury was associated with increased risk of infection. Penn-Barwell et al⁸ found that delaying antibiotics to six or 24 hours had a detrimental effect on the infection rate regardless of the timing of surgery. Lack and colleagues⁹ in a retrospective study of type III open tibial fractures demonstrated that administration of antibiotics beyond 66 minutes from injury was an independent risk factor for infection with an odds ratio of almost four. This led to a change in recommendations for humans with the latest BOAST-4 guidelines suggesting administration of intravenous antibiotics within one hour following injury.

The recent small animal retrospective study³ included 80 client-owned dogs and cats diagnosed with an open fracture that was stabilised using internal implants. In this study the median time from injury to first antibiotic administration was 4 hours and 15 minutes and increasing durations of time were not shown to increase the risk for implant-removal.

Irrigation
Irrigation serves to decrease bacterial load and remove foreign material from the wound and is a pivotal component of open fracture management. While most protocols recommend copious volumes of irrigation fluid, despite intensive research, no reliable data for the appropriate volume exists. In the human literature it is stated that enough fluid should be used until the wound is grossly clean. Basat et al¹⁰ showed that over 1000mls was required to achieve this in 70.5% of the open hand fractures that they investigated, however, the definition of “grossly clean” is highly subjective. In the human literature there are frequent references to the use of 3, 6 and 9 liters for Gustilo-Anderson Type I, II and III open fractures respectively but this practice appears to be related to the fact that saline solutions are available in 3L bags rather than any robust scientific data.

Evaluating whether the timing of irrigation is of importance is not straightforward from the existing literature. Specifically, the timing of irrigation has been evaluated less commonly as it is frequently considered along with debridement rather than as an independent entity. Irrigation after open fractures has long been considered an urgent procedure with a six-hour rule often being quoted, which originated from a 19^th century study.¹¹ Timely irrigation may remove bacteria sooner, mitigating bacterial replication within the site and hereby decreasing infection risk. Some studies do highlight the importance of urgent irrigation in reducing infection in open fractures. However, several studies have contradicted this notion of a six-hour rule, even finding that 24-hour delays in irrigation are not associated with significant increases in rates of infection.^12,13 Currently, there is little evidence supporting the six-hour rule, but more research is required.

Debridement
Thorough surgical debridement plays a critical role in the management of open fractures. Devitalised tissue and foreign material promote the growth of microorganisms and constitute a barrier for the host’s defense mechanisms.

Traditionally, debridement has been recommended within six hours of presentation. The rationale behind this figure is believed to date back to early studies on micro-organism load following contamination.¹¹ In the current literature, the six-hour window does not show a clear evidence base. Many studies do not show a significant difference in the incidence of infection regardless of whether debridement is performed early or is delayed, as long as antibiosis is attended to appropriately. Patzakis and Wilkins⁷ reported that the infection rate was similar in open fracture wounds debrided within 12 hours from injury (6.8%) and in those debrided after 12 hours from injury (7.1%) and concluded that elapsed time from injury to debridement is not a critical factor for development of infection in patients receiving antibiotic therapy. Although bacterial populations in an untreated contaminated wound do increase over time, it appears that early antibiotic administration and thorough surgical debridement can effectively reduce the contamination present. As a result, small delays in surgical management do not appear to translate to increased infection rates and may allow for stabilisation of the patient, as well as for treatment of the patient by experienced surgical teams. The most recent meta-analysis evaluating the effect of delayed surgical debridement in humans¹⁴ supports that delayed surgical debridement results in little to no difference in infection or non-union rates at various time thresholds of up to 24 hours. Based on this, there has been a progressive departure from the traditional emphasis of getting to surgery quickly, instead prioritising expertise, collaboration and performing debridement to a high level of proficiency. Instead of recommending debridement as soon as reasonably possible, the literature supports debridement once appropriate personnel and equipment are available, and ideally within 24 hours.

Wound Closure
As well as timing of initial surgical debridement, so timing of wound closure remains controversial. Historically, concerns about deep infection by anaerobic organisms led to the practice that wounds in open fractures were left open. Delayed wound closure prevents anaerobic conditions in the wound, permits drainage, allows for repeat debridement at 24 -48 hours and gives time for tissues of questionable viability to declare themselves.

However, in recent years, primary wound closure has been evidenced to be beneficial, resulting in lower deep infection and nonunion rates. Scharfenberger¹⁵ demonstrated fewer deep infections (4% vs. 9%) and nonunions (13% vs. 29%) in Gustilo-Anderson type I-IIIa fractures when comparing immediate wound closure to delayed soft tissue coverage. Jenkinson¹⁶ described similar results with an infection rate of 4.1% in fractures treated with immediate closure compared to 17.8% in cases treated with delayed primary closure. Multiple other studies have also confirmed reduced rates of infection associated with earlier definitive soft-tissue coverage and recurring findings amongst these studies include that earlier soft tissue coverage results in not only lower infection rates but also more rapid return to weight-bearing and fewer future unplanned surgeries. The requirement for definitive, early soft tissue coverage appears to be particularly relevant when internal fixation is performed.

In the retrospective study evaluating 80 open fractures in dogs and cats,³ primary closure of the open fracture wound at the time of fracture stabilisation was performed in 85% of cases and there was no evidence that method of wound management had an effect on the risk of explantation.

Based on recent literature, primary closure of open fracture wounds is recommended in carefully selected cases, provided there is no severe tissue damage or contamination, early administration of antibiotics has taken place, meticulous debridement has been executed and the wound edges can be approximated without tension.

Fracture Stabilisation
Definitive skeletal stabilisation is carried out as soon as possible after debridement, however, if not feasible then spanning temporary external skeletal fixators can be used. Stability at the fracture site prevents further injury to the soft tissues and enhances the host response to contaminating organisms. In addition, fracture stability facilitates wound and patient care and allows early motion and functional rehabilitation of the extremity.

It is a common misconception that an open fracture precludes the use of internal fixation, while in fact, all forms of internal fixation remain options in most open fractures. In humans, intramedullary nailing is used widely for stabilisation of open diaphyseal fractures of the lower extremity. Prospective, randomised studies have been performed comparing intramedullary nailing and external fixation for open tibial diaphyseal fractures in people and there were no differences in fracture-site infection or bone healing rates between the two methods. A meta-analysis of the management of open tibial fractures in people also demonstrated that intramedullary nailing reduced the risks of reoperation, malunion and superficial infection compared with the risks associated with external fixators.¹⁷ The severity of the soft-tissue injury rather than the choice of implant appears to be the main factor influencing infection and bone-healing and external fixators likely remain useful for patients with extensive soft-tissue damage and contamination.

In the aforementioned small animal retrospective study,³ the most common stabilisation method used was isolated plate fixation in 52.5% cases. Angle-stable interlocking nails were used in 23.75%, plate-rod technique in 15.0%, Kirschner wires in 3.75% and other internal fixation methods in 5.0% cases. There was no evidence that stabilisation method impacted upon the risk for implant-removal.   

Summary
In summary, based on current evidence, while certain aspects of open fracture management warrant an emergent approach, it appears that many can be delayed up to 24 hours without any negative impact on complication rates or patient outcomes. Initial patient stabilisation, preliminary fracture classification and commencement of systemic antibiosis remain time-critical, with systemic antibiotic treatment ideally being started within one hour of injury. Irrigation and debridement should be performed once appropriate personnel and equipment are available, ideally within 24 hours. Definitive fracture fixation should be performed as soon as possible after debridement, with primary wound closure at the time of fracture fixation being preferred where possible, particularly when internal implants are selected.    

References

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