Bacterial colonization of VEPTR implants under repeated expansions in children with severe early onset spinal deformities.

PURPOSE: Historically, severe spinal and thoracic deformities in children were treated with early long spinal fusions. This prevented further growth of the spine and thorax and often led to small stiff thoraces. Therefore, growth-retaining implants, like vertical expandable titanium ribs (VEPTR), were developed to stimulate thoracic and spinal growth. To accommodate growth, these implants have to be expanded every 6 months. Infection rates of up to 2 % per procedure are reported. Exchange of implant parts allows analyzing the development of implant-related infections and subclinical colonizations.

METHODS: In this prospective study, all patients undergoing repeat VEPTR expansion procedures at our institution were included. Preoperatively, clinical signs of infection were documented, and blood samples were taken. The removed implants were treated by sonication and microbiologically analyzed. The clinical follow-up was documented.

RESULTS: From January 2009 to May 2012, 39 children with 163 re-operations were included. Four of the 39 patients (10 %) developed clinical apparent infections and had implant removal. These were excluded and analyzed separately. Of 144 procedures, implant parts were eligible for analysis. Implant colonization was detected by sonication in 24 of 144 (16 %) operations in 18 out of 39 (46 %) patients. Repeated detection occurred in 5 (14 %) patients. No risk factors for colonization could be identified.

CONCLUSION: The rate of implant colonization is 4.5 times higher than the rate of manifest infections in VEPTR patients. Colonization may lead to a manifest infection over time. The knowledge of persistent implant colonization may change the treatment algorithm in patients with growth-retaining implants.