The Antibiotic Nail in the Treatment of Long Bone Infection




Antibiotic cement nails provide a useful and relatively simple technique to treat intramedullary osteomyelitis of the long bones. These devices provide stability as well as local, targeted antibiotics, which are both critical aspects of osteomyelitis management. Additionally, the use of a threaded core is a critical component of successful cement nail assembly. With adherence to the simple principles outlined in this review, surgeons can expect reliably good results using these drug-delivery implants.


Key points








  • Antibiotic nails are made primarily of polymethyl methacrylate and local antibiotics.



  • Antibiotic nails can provide fracture stability, manage intramedullary dead space, and allow delivery of local antibiotics.



  • Antibiotic nails have proven very successful in the treatment of intramedullary bone infection.






Introduction


Antibiotic cement nails are implants created to provide an intramedullary antibiotic delivery device that also provides fracture stability. Although techniques vary by individual surgeons, these antibiotic nails are typically fashioned from metal coated with antibiotic-impregnated polymethyl methacrylate in the shape of an intramedullary nail or antibiotic cement coating an existing intramedullary nail. Paley and Herzenberg were the first to describe the utility of this device for the treatment of intramedullary osteomyelitis.


Since then, the technique has become widely described in the literature with reported indications ranging from the treatment of diagnosed intramedullary osteomyelitis to prophylactic use in damage control situations whereby there is a high risk of intramedullary osteomyelitis. There are several relatively small case series documenting the utility of this device as a component of intramedullary osteomyelitis treatment in addition to adequate boney debridement and systemic antibiotics. Additionally, there are several articles describing modifications to the fabrication technique of these devices. The purpose of this article is to review the rationale, indications, techniques, and outcomes of antibiotic nail use in the treatment of long bone infections.




Introduction


Antibiotic cement nails are implants created to provide an intramedullary antibiotic delivery device that also provides fracture stability. Although techniques vary by individual surgeons, these antibiotic nails are typically fashioned from metal coated with antibiotic-impregnated polymethyl methacrylate in the shape of an intramedullary nail or antibiotic cement coating an existing intramedullary nail. Paley and Herzenberg were the first to describe the utility of this device for the treatment of intramedullary osteomyelitis.


Since then, the technique has become widely described in the literature with reported indications ranging from the treatment of diagnosed intramedullary osteomyelitis to prophylactic use in damage control situations whereby there is a high risk of intramedullary osteomyelitis. There are several relatively small case series documenting the utility of this device as a component of intramedullary osteomyelitis treatment in addition to adequate boney debridement and systemic antibiotics. Additionally, there are several articles describing modifications to the fabrication technique of these devices. The purpose of this article is to review the rationale, indications, techniques, and outcomes of antibiotic nail use in the treatment of long bone infections.




Rationale


The rationale for intramedullary antibiotic cement rods is an extension of the known utility of antibiotic-impregnated bone cement in the treatment of osteomyelitis. There are several studies describing the effective use of bone cement as a delivery device of antibiotics directly to an area of musculoskeletal infection. The importance of local antibiotics in the treatment of bone infection has been well accepted and become a standard component of current osteomyelitis management.


Cierny and colleagues described 4 key principles in the treatment of osteomyelitis:



  • 1.

    Debridement and dead space management


  • 2.

    Stabilization


  • 3.

    Soft tissue coverage


  • 4.

    Adequate antibiotic administration



The implementation of an antibiotic nail as part of long bone osteomyelitis management directly addresses 3 of these 4 principles. Clearly an antibiotic nail satisfies the need for local antibiotic administration to the intramedullary canal; however, the cement nail infused with antibiotics uniquely provides a method of filling the canal dead space as well as providing stability to the bone.


The antibiotic nail’s stability will vary depending on the amount of antibiotics placed in the cement, as this alters the integrity of the cement after curing, as well as the metal device on which the surgeon molds the cement. Although the strength of these different nail techniques has not been compared scientifically, it makes sense to hypothesize that a larger metal device at the center of the nail would provide greater stability. Coating an intramedullary nail in cement would likely create an antibiotic nail most resistant to deformity, which Thonse and Conway described; but an antibiotic implant with such stability is unnecessary in most chronic osteomyelitis cases.


In addition to the stability that antibiotic nails offer, there are several advantages provided by the nail. Antibiotic beads are a proven method of treating osteomyelitis. Problems cited with bead use within the intramedullary canal include lack of dead space filling as well as potential extraction difficulty if left in place for a long duration. In contrast, the antibiotic nail can be sized in a custom fashion to fill the patients’ canal, filling the dead space as well as maximizing the amount of antibiotic cement introduced into the canal. The duration of which the antibiotic nail can be left in place as well as the relative ease of extraction are further unique advantages of the nail over beads. Paley and Herzenberg described removal of a nail after 753 days with relative ease.




Indications and contraindications


Given the numerous advantages of the antibiotic cement nail and relative ease of implementation as well as extraction, there is expanding use of this technique. The original description of its use entailed treatment of intramedullary osteomyelitis. Most of these patients required a long duration of external fixation for deformity correction with subsequent infection of the intramedullary canal. Since that time, additional case series have documented utilization of the antibiotic nail in other circumstances, which include treatment of chronic osteomyelitis and infected nonunions of the diaphysis. Moreover, other surgeons advocate the use of an antibiotic nail as a prophylactic modality in the setting of prolonged external fixation either in the face of severe trauma requiring staged fixation or in lengthy deformity correction.


There are no absolute contraindications to the use of an antibiotic nail in the treatment of long bone infection. Open physes in children may limit the use of antibiotic nails because of the potential harm caused to the growth plate by insertion of the nail. Nonetheless, Bar-On and colleagues were able to use antibiotic rods in the intramedullary canal without disrupting the physes in children as young as 4.5 years of age. Shyam and colleagues reported concern with bone defects greater than 6 cm because of a lack of stability provided by antibiotic nails in their study. It is unclear that this is valid for all antibiotic nail constructs, and it does not seem to be reason for not using the antibiotic nail as much as it is reason to augment the nail with another form of stabilization.




Treatment methodology


Effective utilization of antibiotic nails for the treatment of long bone infection consists of several important treatment steps. These steps are consistently described throughout the literature reporting antibiotic-infused cement nail use. The sequence of appropriate infection treatment with antibiotic nails includes infection diagnosis, debridement, antibiotic nail placement, and antibiotic nail removal with or without definitive hardware placement.


Diagnosis


To begin, patients must have an accurate diagnosis, which includes culture identification of the infectious agent as well as sensitivities and susceptibilities. Thorough patient history is important to identify any factors that will affect treatment, such as immune-compromise, or aid in treatment, such as surgical and infection history. In particular, the history of an intramedullary device is an important factor in diagnosing long bone infection. Laboratory evaluation should include white blood cell count, erythrocyte sedimentation rate, C- reactive protein, and blood cultures. These studies will potentially aid in diagnosing infection and will certainly help with monitoring the effectiveness of treatment.


Imaging is an important part of diagnosing intramedullary osteomyelitis. Radiographic signs are not present in an acute infection but in chronic osteomyelitis include diffuse demineralization, soft tissue swelling, periosteal reaction, involucrum formation, and trabecular destruction with a change in bony architecture. Of note, these findings may be minimal if an intramedullary device is in place from previous surgery. Advanced imaging, such as MRI, computed tomography (CT), and bone scans, are useful to identify areas affected by infection.


Signs of osteomyelitis on CT scan include cortical bone destruction, new bone formation, and soft tissue swelling or abscess formation. In addition, signs of increased bone marrow density and gas in the medullary canal are highly specific for osteomyelitis. An additional finding that can be seen with CT in the chronic setting is sequestrum. The CT results will also provide important information about the suspected stability of the bone, which may require the intramedullary stability of a cement Intramedullary Nail (IMN).


MRI will show the soft tissue extent of the infection and importantly the spread of infection within the intramedullary canal. The presence of an intramedullary device obviates this step, as intramedullary infection is present along the length of the implant and the metal will obstruct the image quality. Studies have demonstrated up to 95% sensitivity and 91% specificity in the diagnosis of osteomyelitis with MRI. Because MRI delineates the proximal and distal bone marrow involvement, it provides the best overall impression of the extent of the infection.


Because treatment to eradicate the infection can occur only after knowing the offending bacteria, biopsy and culture are part of the diagnostic process. Culturing should consist of sampling from multiple areas within the location of concern in a sterile, operating room setting. Aerobic and anaerobic tissue culture bottles with an agar medium are ideal as they increase the culture yield. With an IMN in place, the interlocking screw sites are important locations to culture, as they provide information about the extent of infection spread along the nail.


Debridement


Debridement is performed at the same operating room trip as biopsy and culture. The goal of debridement is to remove infected tissue as well as dead tissue, which is a nidus for further bacterial colonization. The debridement must decrease the bacterial load to less than 10 5 colonies so that antibiotic therapy and host defenses can complete the eradication of infection. Once the area of infected bone is identified, debridement of the bone should continue until healthy bleeding bone is encountered. Instruments such as burrs, rongeurs, and curettes are useful tools to achieve a sufficient debridement. Often 1 debridement is inadequate, as Patzakis and colleagues demonstrated that 26% of patients with chronic osteomyelitis of the tibia had positive intraoperative cultures during their second debridement. When there is gross purulence or a significant amount of necrotic tissue present, additional debridement should be performed.


When considering long bone infection, there is often extensive intramedullary canal involvement. Intramedullary reaming provides an effective option to debride the canal without creating extensive incisions. Standard reaming may be performed; but a vent hole must be used to avoid increasing intramedullary canal pressures, which can drive infectious material into the circulatory system. Intramedullary reaming and irrigation device allows for simultaneous reaming, irrigation, and aspiration of the medullary canal that can be sent for culture. The use of irrigation and suction while reaming decreases the amount of heat generation, which in turn decreases the risk of endosteal thermal necrosis. A study by Goplen and colleagues demonstrated that RIA produced pressures less than atmospheric pressure, making the RIA less likely to force bacteria into the blood stream than standard reaming.


Antibiotic Nail Placement


As discussed previously, the antibiotic rod provides both stability and local antibiotics to the canal. Stabilization of the bone is a vital component in eradicating infection, as it stabilizes bone and soft tissue for healing, which decreases the likelihood of persistent infection. Many studies support the use of local antibiotics to decrease infection when used in conjunction with systemic antibiotics.


There are several techniques for antibiotic nail formation, but the basic principles are the same for all nails described in the literature. The nail typically consists of antibiotic-impregnated cement coating a rigid object with a method for extraction built into the design. The greatest variation seems to be in the object used for the core of the nail, with investigators reporting use of ender nails, Ilizarov threaded rods, intramedullary nails, carbon fiber nails, as well as cut guidewires.


Antibiotic Nail Removal and Definitive Hardware Placement


Nail removal occurs after a period of adequate treatment with the local antibiotics as well as systemic antibiotics based on culture results. During this time, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are monitored to ensure downward to normal values indicating sufficient treatment of the infection. If the initial treatment is found to be inadequate based on these values, then the authors repeat debridement and insert a new antibiotic nail. Once the treatment is adequate and ESR and CRP values remain normal off of systemic antibiotics, then nail removal and definitive bone fixation can occur as needed. In the review of case series, there is minimal difficulty reported when attempting to remove these antibiotic implants ( Table 1 ).



Table 1

Summary of case reports and case series for using antibiotic nails in the treatment of intramedullary bone infection








































































































































Article, Year N Resolved Mean Age (y) Location F/U (mo) Equipment Antibiotics in Cement (per Bag of Cement) Length of Antibiotic Nail Treatment Length of Systemic Antibiotics (wk) Complications
Kanakaris et al, 2014 24 23 45 (17–75) 14 Femurs
10 Tibias
21 (8–36) Not specified 0.5 g Gentamicin in cement
2 g Vancomycin
Antifungal as needed
2.6 (1–5) mo 3–18 4% Recurrence leading to amputation
Wasko & Borens, 2013 10 10 42 (20–59) 10 Tibias 72 (60–84) K wire
Chest tube
2 g Gentamicin 6 wk 6–8 None
Selhi et al, 2011 16 14 39 (18–54) 8 Femurs
7 Tibias
1 Humerus
39 (18–54) Kuntscher nail
Steel wire
Interlocking nail
0.5 g Gentamicin in cement
4 g Vancomycin
12–18 12% Infected nonunion
Bar-On et al, 2010 4 4 9 (5.5–14.6) 2 Tibias
2 Femurs
41 (36–46) 1.2-mm K wire
28-G Chest tube
Gentamicin (amount not specified) 16–62 d 16 50% Wound complication
Bhadra & Roberts, 2009 30 47 (20–79) 24 Tibias
6 Femurs
26 (4–40) Ender nail
Chest tube
1.2 g Tobramycin
1 g Vancomycin
42 d Average 5–8 Unknown
Shyam et al, 2009 25 20 33 (21–58) 23 Femurs
2 Tibias
29 (18–40) 6 or 7 mm Nail 2 g Vancomycin
2 g Gentamicin
8 (6–12) wk 20% Recurrence
Sancineto & Barla, 2008 19 17 37 (18–52) 4 Femurs
14 Tibias
37 (10–54) Chest tube
Ender nail
4 g Vancomycin,
+/− Gentamicin, tobramycin, imipenem
6–76 wk Unknown 5% Septic knee
5% abx vancomycin hypersensitivity
Qiang et al, 2007 19 18 38 (22–78) 6 Femurs
13 Tibias
16 (6–28) Chest tube
3-mm Guidewire
2 g Vancomycin 35–123 d 6–8 32% Partial union
5% Nonunion
5% Rod fracture
5% Septic knee
Thonse & Conway, 2007 20 18 47 (15–79) 7 Femur
3 Tibia
5 Knee arthrodesis
5 Ankle arthrodesis
16 (7–40) Custom molds coating nail 1 g Vancomycin
3.6 g Tobramycin
Unknown Unknown 5% Nonunion
10% Nails debonded
5% Amputation
Paley & Herzenberg, 2002 9 9 30 (8–70) 6 Femur
2 Tibia
1 Humerus
41 (32–48) Chest tube
3-mm Beaded guidewire
2.4 g Tobramycin
2 g Vancomycin
29–753 d Unknown 33% Nonunions
11% Rod fracture

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Oct 6, 2017 | Posted by in ORTHOPEDIC | Comments Off on The Antibiotic Nail in the Treatment of Long Bone Infection
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