• Jon A Lutz, Philippe Otten, and Gianluca Maestretti.
• Department of Orthopaedic Surgery, Cantonal Hospital, 1708 Fribourg, Switzerland.
• Eur Spine J. 2012 Dec 1;21(12):2573-9.

IntroductionDynamic stabilization of the spine was developed as an alternative to rigid fusion in chronic back pain to reduce the risk of adjacent segment degeneration. Dynamic neutralization system (Dynesys, Zimmer CH) is one of the most popular systems available, but some midterm studies show revision rates as high as 30 %. Some late infectious complications in our patients prompted us to review them systematically. Propionibacterium recently has been shown to cause subtle infections of prosthetic material.Materials And MethodsHere, we report on a consecutive series of 50 Dynesys implants. In a median follow-up of 51 months (range 0-91), we identified 12 infectious and 11 non-infectious complications necessitating reoperation or removal of the implant in 17 patients.ResultsMaterial infections occurred after a median of 52 months (2-77) and were due to Propionibacterium alone (n = 4) or in combination (n = 3) in seven out of 11 patients. Clinical presentation combines new or increasing pain associated with signs of screw loosening on conventional X-rays; however, as many as 73.5 % of patients present some degree of screw loosening without being at all symptomatic of infection.ConclusionThe high rate of late infections with low-grade germs and the frequency of screw loosening signs made us suspect a lack of integration at the bone-screw interface. Surgeons should be suspicious if the patient presents a combination of new or increasing pain and signs of screw loosening, and aggressive revision is recommended in these cases.

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