Infection Rates and Risk Factors with Magnetic Intramedullary Lengthening Nails

INTRODUCTION Surgical site infection (SSI) related to magnetic intramedullary lengthening nails (MILNs) can lead to delayed consolidation or loss of limb function, resulting in deleterious effects to a patient’s quality of life. With the rise of MILNs, we sought to determine the incidence rate and risk factors for infection during limb lengthening with MILNs. METHODS We reviewed a consecutive series of patients who underwent femoral and/or tibial lengthening with an MILN at a single institution between 2012 and 2020 (n=420). SSI was defined according to CDC-NHSN criteria (including superficial and deep infections) with postoperative surveillance time of 12 months. Demographic, health metrics, comorbidities, limb- and surgery-related factors, were assessed as potential risk mediators of SSI. RESULTS Incidence of SSI was 3.3% (14/420). This was divided into superficial (.5%,2/420) and deep (2.9%, 12/420) infections. Of deep infections, 75% (9/12) were osteomyelitis. Of the 14 limbs that developed SSI, 57% (8/14) had a history of prior external fixation in the same limb and 38% (5/14) had a previous infection of the same limb. A subanalysis of patients with a history of prior external fixation in the same bone was associated with SSI, as compared to those without previous external fixation. None of the surgery-related infection risk factors reached statistical significance. DISCUSSION AND CONCLUSION The total incidence of infection with MILNs was 3.3% at 24 months follow-up. The risk of deep infection was 2.9%. Patients with a history of previous external fixation and prior infection show an independent association with increased rate of infection recurrence in the same bone. These patients could be considered a high-risk group for developing deep tissue infection. Potential algorithms include prolonged oral antibiotics after MILN insertion or simultaneous injection of absorbable antibiotic at the time of the nail insertion.