Research : Wisonsin Foot & Ankle Institute
Prevention and Management of Complications Arising from External Fixation Pin Sites
Tags: ankle replacement, diabetes, external fixation, infection, limb salvage, osteomyelitis, PRP, reconstruction,
Authors: Christopher Bibbo, DO, DPM, FACS, FACFAS, Jon Brueggeman, DPM
The use of external fixation devices to assist in the management of lower extremity trauma and reconstruction continues to rise. Despite the distinct advantages of external fixation, complications from external fixators continue to exist. The complicated external fixator-associated pin site may be a potential source of significant morbidity, especially in the at-risk patient, which may lead to soft tissue healing problems and infections, as well as osteomyelitis. This article describes both simple as well as more complex techniques that the authors use in the prevention and management of complications arising from external fixator pin sites, and solutions to the difficult task of incorporating external fixator wires into negative-pressure dressings.
The history of external fixation dates back to Hippocrates (circa 460-380 BC) as the first to describe a primitive, but brilliant, technique for achieving fracture reduction (1). The most familiar early modern concepts of external fixation are credited to Malgaigne of France in 1840 (1-3) and Parkhill of Denver, Colorado, in 1897 (1-3). The development of external fixation was historically associated with a reputation for infectious complications and mechanical instability, which evolved because of increased usage in the hands of surgeons often inexperienced with the use of external fixation use during WorldWar II. External fixation was even banned by the United States military because of these concerns (1-3). Modern external fixation techniques and education have ameliorated many of these technical problems. However, throughout time, one of the most common complications associated with external fixation has been pin-site irritation and infection. Although published studies vary widely in the reported rates of pin-site complications, it is still an observable event even in the most experienced hands. Recent reviews on external pinsite complications reveal that Parameswaran et al reported a rate of 11.2% in 285 fractures, whereas Ahlborg and Josefsson reported a 21% infection rate in distal radius fractures. A more recent study by Schalamon et al reported a 52% infection rate in pediatric fractures, with 94% of those infections resolving with either topical or systemic antibiotics (4-7). Pin-site irritation/infections have almost become an excepted certainty in the realm of external fixation, with physicians relying heavily on the majority of those complications resolving without consequence by using appropriate pin care and antibiotic therapy.
In an effort to prevent the morbidities associated with long-term immobility, internal fixation, and extensile incisions, which may pose a larger risk for wound-healing complications, it is becoming more common for at-risk patients to be treated with external fixation techniques. Despite the best of efforts with pin care, draining fine wire sites and half-pin sites in high-risk patients will still occur. Half pins have a propensity to create larger pin-site wounds, which in compromised hosts may result in a chronic nonhealing pin-site tract or, in the absence of a proactive interventional treatment, delayed wound healing. In particular, half pins of size 6.5 or larger, often used to help stabilize external fixation in trauma and reconstructive procedures of the lower extremity, especially in obese and heavy muscular patients, may be difficult to obtain wound closure.We have observed that a certain subset of patients are also at an increased risk for developing chronic nonhealing wounds after removal of half pins or even fine wires. In our experience, these patients include those with diabetes mellitus, chronic venous insufficiency, peripheral vascular disease, and a poor soft tissue envelope due to trauma. The size of a wound left by half pins leaves a tract with direct communication to the intramedullary cavity, creating the risk for the development of osteomyelitis, especially in at-risk patients (e.g., patients with diabetes). Over the past 8 years, in the course of applying numerous external fixators of various designs, usages, and manufacturers, we have found several techniques effective in preventing pinsite complications and reducing pin-tract morbidity by facilitating primary pin-site closure. We also describe strategies on how to treat actively infected osteomyelitic pin tracts, how to manage difficult-toheal pin sites, and how to safely insert external fixation wires that will be in close proximity to negative-pressure dressings.
Fig 1: Photograph of infected half pin (left panel). The VERSAJET to debride the pin site soft tissue and bone, and the ankle wound (right panel).
Prevention of Pin-site Complications
Needless to say, prevention of pin-site morbidity is always worth the effort. The senior surgeon (C. B.) typically manages external fixation pin sites locally and regionally, both intraoperatively and postoperatively. Intraoperatively, care should be taken to ensure that during pin insertion, proper pin cooling and, in the case of half pins, predrilling, should be performed. If possible, muscle compartment should be placed on stretch during placement of fixation pins and wires. In addition to using the ''safe zones,'' if given a choice, pin placement is best in areas that possess thick subcutaneous tissue layers and are away from the thickest portions of cortical bone. To prevent thermal necrosis and skin irritation, cooling of wires with cool saline solution is extremely helpful, as well as the patient's attitude toward wire insertion. In the senior surgeon's observations, among proprietary fine wires, the Orthofix X-Wire (Orthofix, McKinney, TX) has demonstrated the least amount of thermal necrosis. The design of the tip of the X-Wire has been experimentally demonstrated to reduce heat generation during insertion (8). To prevent pin loosening with subsequent pin tract morbidity, such as loss of fixation, infection, and implant failure, half pins should interface with bone as efficiently as possible. To achieve maximum security between bone and half pins, predrilling (even with self-drilling pins) and the use of hydroxyapatite-coated half pins have proven to us to provide the most stable long-term fixation solution, even in at-risk patients.
Fig 2: VERSAJET being used to debride a half-pin site (left panel) and a fine-wire pin site (center panel). Final primary pin-site closure (right panel). In the high-risk patient (former patients with diabetes), primary pin-site closure after thorough debridement may assist with reduction of pin-tract morbidity.
Before the patient leaves the operating room, all pin sites (both fine wire and half pin) must be free of skin tenting and soft tissue impingent. Correction of these problems may simply require placing a small, relaxing incision extending from the pin outward into the area of contention. This skin of the relaxing incision may be partially closed, based on the new excursion of the skin around the pin. Failure to accomplish peri-pin skin relaxation may ultimately require replacement of the pin.
Postoperatively, local pin care strategies should be simple, easy to execute, and cost effective, and prevent bacterial colonization and skin irritation. The authors have found that under most circumstances, even in at-risk patients, once daily pin care performed with cleansing of the pin/skin interface with simple isopropyl alcohol and removing any crusted, weeping edema fluid provides adequate care. When patients transition to the responsibility of providing their own pin care, the daily application of isopropyl alcohol to multiple pin sites is simplified by the use of a handheld spray bottle to dispense the alcohol. The addition of daily bacitracin and an open-cell foam (''Ilizarov foam'') over the skin, applied for 5 to 7 days postoperatively, is beneficial in at-risk patients. Pin-site care needs to be performed only once daily; the routine use of more frequent pin-care regimens usually leads to skin irritation and increased pin-tract morbidity. In patients receiving anticoagulation, bleeding pin sites may be dressed with a dry, absorbent sponge as needed until bleeding subsides. The use of harsh chemicals, such as povidone-iodine or hydrogen peroxide, is strongly discouraged.We have found no advantage in the use of silver-impregnated pin-specific dressings over a simple, daily cleansing regimen with alcohol. Regional postoperative edema control is vital to ensuring that the peri-pin skin ''seals.'' Applying daily edema control wraps, elevating, and limiting the time that the limb is spent in a dependent position may help to hasten pin-site quiescence.
Pins that fail (break, loosen) must be replaced, with reinsertion just outside the zone of failure. Failure to recognize impending or immediate pin/wire failure may rapidly result in soft tissue and pinsite bone infections. The anterior cortex of the tibia (crest) should be avoided during wire insertion. Areas of soft, friable bone (in the elderly, smokers, steroid users, osteoporotic patients, those with Charcot bone) should also be evaluated and bypassed if possible. Proper technique during pin/wire reinsertion as well as appropriate wire-tensioning protocols must be reviewed and strictly followed after pin/wire failure. Rigidity of the external fixator construct should also be reevaluated. Weight-bearing protocols may need to be reevaluated and adjusted on a case-by-case basis.
Primary Debridement and Closure
Once the patient has been placed on the operating room table and anesthesia has been administered, the fine wires of the ex-fix are cut if present and the device removed, leaving the implanted wires and half pins in place. An alcohol preparation of the implanted fine wires and half pins is then performed before complete removal. All wires are then removed with a large needle driver or pliers, and the half pins are removed with the use of a universal T-handle chuck. Review of preoperative films to confirm the location of olive wires is always recommended. After removal of all pins and wires, a full surgical preparation and standard draping are performed. The senior author prefers a chlorhexidine-alcohol preparation rather than povidoneiodine because of the superior efficacy of a chlorhexidine skin preparation in clearing bacterial skin contamination (9).
Debridement of the half-pin sites is then performed with the use of VERSAJET Hydrosurgery System (Smith & Nephew, Memphis, TN) (Figures 1, 2). The VERSAJET system incorporates a high-pressure jet of sterile saline solution that travels parallel to the wound surface. This high-speed jet creates a Venturi effect that, when coupled with wall suction, allows the surgeon to sharply debride and remove fine layers of tissue with a single handheld instrument. The surgeon can select varying power settings, allowing differentiation between tissue types, sparing viable tissue while precisely targeting and removing debris and damaged tissue. The size of the VERSAJET hand piece is chosen via surgeon preference and/or size of the defect. Different angulations of the hand piece are also available, which may help facilitate debridement. The senior author prefers a power setting of 4 to 6 for this procedure because of the small nature of the involved wounds and a straighter hand piece to avoid obscuring the view of the hand piece tip, as well as providing the ability to enter and debride the cortical defect created by the half pin.
After debridement of the soft tissue cuff, if pin sites have appeared grossly contaminated/infected or demonstrate indirect evidence of infection/osteonecrosis such as nonpurchase of half-pin thread in bone, it is particularly important to provide bone tract debridement. This is accomplished by placing the VERSAJET tip directly into the bone tunnel, with debridement performed in a circular motion, going as deep as the hand piece allows. Using a lower-angled hand piece is helpful in this setting. Occasionally, a gentle bend can be placed on the tip of the hand piece to allow a straighter path. In the instance of pinsite skin cut-out, after VERSAJET debridement, wound edges are then freshened via sharp dissection and primary closure performed with standard closure techniques. For wounds too large for simple closure, after bone debridement, elliptical excision of the wound and the undermining of surrounding tissue may also be required to allow closure. The authors recommend either nylon or polypropylene suture for closure. If, under unusual circumstances, healing by secondary intention is deemed necessary (e.g., pin sites associated with copious purulent drainage from osteomyelitis and associated soft tissue infection requiring repeat irrigation and debridements), the VERSAJET is useful to debride all local tissues and assist with repeat operative debridements, thereby promoting a healthy local tissue bed.
Recalcitrant Nonhealing Pin Sites
When large pin tracts prove to be recalcitrant to debridement followed by primary closure, small, local rotation flaps may be useful. In patients who have pins in place on a long-term basis, fibrous rinds may form around their pins/wires. This may occur in at-risk patients such as smokers, those with a poor soft tissue envelope from trauma, those with venous stasis dermatitis, as well as those who exhibit severe, fluctuating, brawny edema, those with Charcot, and those with bone transports. In the setting in which longstanding pin wires are recalcitrant to debridement and primary closure, it is mandatory to rule out and treat an underlying osteomyelitis versus simple thermal bone necrosis (vide infra). A small, local, random-pattern fasciocutaneous flap is raised, choosing the flap based on inflow region as well as the condition of adjacent tissue available for transposition. Local debridement with the VERSAJET is performed (vide supra), followed by creation and insetting of the local flap, in accordance with standard plastic surgical principles (Figure 3).
Treatment of Thermal Bone Necrosis and Osteomyelitic Pin Tracts
We have observed that thermal osteonecrosis of bone most commonly occurs when fine wires are inserted too anterior on the tibia and placed into the thick anterior crest of the tibia. Half-pin thermal osteonecrosis may also occur in thick cortical bone when predrilling is not performed. Wire cut from bone, frank wire failure, half-pin loosening, and even fracture of bone adjacent to the half pin may ensue. The overlying soft tissues may become irritated. Immediate wire removal will usually suffice, but, if left untreated, continued soft tissue irritation may result in bacterial colonization, and a simple osteonecrosis may then progress on to become an osteomyelitis. In the rare event that an area of osteonecrosis is painful, bone debridement may be required. Very rarely, the skin and soft tissue overlying a zone of osteonecrosis may require reconstruction (vide infra). When osteomyelitis is suspected, adequate cultures should be taken to direct antibiotic therapy. The successful treatment of osteomyelitis in at-risk patients can be a daunting task, thus as much information as possible from the suspect site is acquired. The senior author routinely sends tissue specimens (not swabs) for aerobic, anaerobic, acid-fast, and fungal cultures. If cultures are negative, the laboratory is instructed to perform bacterial 16S-polymerase chain reaction and fungal 18S-polymerase chain reaction, searching for the presence of bacterial and fungal genetic material, respectively. When available, bone tissue is also sent to pathology for evaluation. This information will greatly assist the infectious disease team in selecting antibiotic therapy. Debridement of the infected pin tract is mandatory. This may be accomplished with the VERSAJET, curettes, or overdrilling. If overdrilling is selected, it must be used with caution, so as to not induce additional thermal osteonecrosis or remove excessive bone that may result in a stress-riser-induced fracture. Suspected and known areas of osteomyelitic pin tracts may be back-filled with antibiotic-impregnated, absorbable calcium-sulfate pellets (OsteoSet, Wright Medical, Memphis, TN). To cover the most usual pathogen suspects, these absorbable antibiotic delivery devices are loaded with antibiotics separately: one batch of pellets with vancomcyin and another batch with tobramycin. The pellets are placed deep into the bone pin tunnel and medullary cavity, alternating vancomycin with tobramycin pellets (Figure 3). Special attention to closure is important to prevent ''spitting'' of calcium sulfate pellets from a noncontained defect. Closure over OsteoSet pellets is performed with an absorbable running deep fascial stitch that continues into a deep running subcutaneous and then dermal suture line. The epidermis is then closed with a running nylon suture (Figure 3). Skin glue may also be applied over the epidermal suture.
Fig 3: Chronic drainage from a tibial half-pin site with culture-confirmed osteomyelitis (left panel). After debridement of pin tract soft tissue and bone, OsteoSet pellets loaded with vancomycin and tobramycin are inserted into the bone tunnel and medullary cavity (center panel). A local fasciocutaneous flap was used to cover the chronic draining area; a multiplelayer running closure is used to prevent ''spitting pellets'' (right panel).
Fig 4: Anteroposterior and lateral radiographs of tibial shaft fracture secondary to half-pin loosening followed by local trauma. Removal of the half pin resulted in bone loss in a critical area of the tibial shaft. Similarly, bone loss after half-pin removal may also result in fracture.
Fig 5: A Bilateral transarticular external fixators placed to facilitate both fracture fixation and wound coverage in a right-sided 3B distal femur/3C proximal tibia and a left-sided traumatic subtotal amputation, requiring multiple muscle rotation and fasciocutaneous rotation flaps, negative-pressure dressings, neodermal grafting, and skin grafting. Polytrauma patients such as this one can expect to have a long recovery, accompanied by long-term external fixation devices and the attendant possibility of pin-site morbidity. B After successful soft tissue reconstructions, the removal of the external fixator is accomplished with VERSAJET debridement and primary closure. Note the ability to debride the bone tunnels with the VERSAJET, which is useful in routine debridements as well as in cases of suspected osteomyelitic pin tracts. C Backfilling of the half-pin sites with PRO-DENSE to augment strength and diminish the potential for stress riser-induced fracture. Excess PRO-DENSE that has extravasated into the soft tissues should be removed, but any small amount that remains in the soft tissues will be absorbed over a few weeks.
Bone Loss After Pin Removal
In situations in which the removal of a large half pin (e.g., calcaneus, tibia) potentially creates a stress riser and potential area for fracture (Figure 4), after debridement of the pin site, the senior author will back-fill the pin site with a strong, slow in-growth biomaterial, such as PRO-DENSE (Wright Medical) (Figure 5A-C). In this manner, the compressive and cantilever forces that could result in stress concentration and, ultimately, propagation of a fracture may be lessened. Thus, the risk of fracture through the site of a half-pin removal may be reduced. However, to safely use this technique, the area must be free of osteomyelitis.
Pin Tracts Around Negative Pressure Dressings
A proper ''seal'' on a negative-pressure dressing sytem (e.g., VAC; KCI, San Antonio, TX) is paramount to the success of the closed-system application. The close proximity of fine wires and half pins to a VAC dressing lends for difficulty in maintaining appropriate negative pressure, especially in difficult trauma and patients with diabetes (Charcot, infection). In these instances, rather than apply the VAC last, we have found it useful to first lay down and apply either thin Duo- Derm (ConvaTec, Skillman, NJ) or a VAC drape over the peri-wound area, then pass the fine wires or half pins that will land in a ''hot landing zone'' near the area that requires the VAC. The exit/entrance point of the pin through either drape or DuoDerm is facilitated with a minute stab incision into the material. Upon exiting a fine wire from the opposite side of a VAC, it is best to tap the wire into position with a mallet, which will prevent the drape material from becoming wrapped up on a spinning wire. The VAC is then assembled and covered with the final drape. The system is tested, and usually any residual leaks are very small and easily patched. Pins in the area under the VAC drape/DuoDerm are cared for at the time of VAC change in a similar manner to daily care, but only isopropyl alcohol is used. When pin sites must be cared for more frequently than at VAC changes, or, if a large, persistent leak occurs because of pins traversing the VAC zone, then the VAC system is simply hooked up to a low wall or portable gastrointestinal suction unit.
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