MR-compatible antibiotic interlocked nail fabrication for the management of long bone infections: first case report of a new technique

Successful management of intramedullary long bone osteomyelitis remains a challenge for surgeon and patient alike. Patients are often immune-compromised and may have endured multiple surgeries. Treatment principles initially described by Cierny in 1983 include antibiotic administration (systemically +/- locally), surgical debridement of the infection site and stabilization[1]. The Cierny classification includes an anatomic description of the infection and a description of the host’s resistance to infection[2]. The anatomic description is divided into four types (I-medullary, II-superficial, III-localized full-thickness, IV-diffuse). The description of host’s resistance is divided into three classes (A-healthy, B-locally or systemically impaired, C-major systemic disorder). Since their description in 2002[3], antibiotic coated nails have become part of the armamentarium for the treatment of osteomyelitis allowing both local elution of antibiotics and stabilization of a debrided long bone[3‐14]. Limitations to their utilization have remained due to the technical difficulty of their fabrication and presence of MRI artifacts. There is great variation in the techniques utilized to fabricate antibiotic nails. A guide wire, Enders rod or more recently an interlocked nail, provide stability to the construct. Utilization of interlocked nail has shown satisfactory results while allowing for rotational stability[12, 14]. A chest tube is often the best mold available to fabricate the cement nail. Cement nail extraction from the tubing system remains a frustrating exercise, complicated by the melting of plastic and subsequent adhesion to the cement. The technique that we describe is a rapid and reproducible exercise. In addition the utilization of a radiolucent carbon fiber interlocked nail (Carbo-Fix, Champlain, IL, U.S.A) allows for a solid, rotationally stable, MRI compatible fixation. Where inflammatory markers are not always reliable, this latter characteristic enables MRI monitoring of infection with an intramedullary implant in place.

In this manuscript, we present a novel surgical technique for the fabrication of antibiotic nails using a radiolucent antibiotic carbon fiber interlocked devise. The authors are unaware of any previous publication of this technique. In our opinion, the addition of mineral oil and dipping of the antibiotic nail in a cold saline bath ensure a rapid, easy and reproducible method of fabrication. Interlocking the nail provides excellent rotational stability. The carbon fiber nail allows a follow up of the treatment response with limited metal artifact on MRI scan and visualization of the lesion on X-ray. This is especially valuable in immune-compromised patients where inflammatory markers are rarely reliable to monitor treatment response.

The use of interlocked intramedullary nails for intramedullary infections is not a novel concept and has previously been published for infected nonunion and delayed union of the tibia[18]. Carbon fiber nail for this indication is novel. We were unable to find any literature regarding carbon fiber nail use in long bone osteomyelitis despite the fact that carbon fiber technology use has been increasing over the last few years in Orthopaedics. Literature on carbon fiber implants in spine fusion confirms less artifact and improved evaluation of fusion compared with traditional implants[19‐22]. It would logically follow that visualization would be improved in cases of bone infection.

Alternative implant options for treatment could have been a large wire coated in antibiotic cement. This method would certainly have decreased implant cost (the cost of the carbon fiber nail was $2,600) and perhaps limited the amount of exposed metallic surface for bacterial contamination. However, with our method of treatment, the patient is full weight bearing as opposed to partial weight bearing with a simple large pin and cement. In addition, the interlocking fixation minimizes the risk of migration of the construct proximally into the medullary canal and/or distally into the knee joint. Finally, although minimal, there would remain some MRI artifact created by the stainless steel pin. Given these disadvantages, this remains our preferred implant choice for this case scenario.

Our paper is by no means intended to recommend this methodology of treatment for all cases of long bone osteomyelitis or infected non-unions. The treatment of osteomyelitis is complex and needs to be individualized to each patient and problem[23]. We believe that this novel technique adds to the armamentarium to treat these difficult cases. Weakness of our manuscript includes the lack of long-term follow up. Our current research focus is to retrospectively evaluate a series of patients with long bone infection or infected non-unions treated using this technique. The use of mineral oil to coat the inner layer of the plastic tube may alter the elution properties of antibiotics loaded in the cement. In addition, mineral oil on the surface of the nail may create a localized inflammatory response (although the cured nail is copiously irrigated prior to its insertion). We could find no reports of this occurrence in the literature.

The presented use of antibiotic nail in general is ‘off- label’ according to current FDA indications. Our patients are informed during the shared decision making process. For research purposes our research division has contacted the FDA for suggestions on how to proceed with the prospective study of such implants.