MRI-based Decision Making of Implant Removal in Deep Wound Infection After Instrumented Lumbar Fusion.

STUDY DESIGN

A retrospective study.

OBJECTIVE

The aim of the study was to review the treatment of deep wound infection after posterior instrumented lumbar fusion, and thereby to optimize the decision-making process of implant removal or retention on the basis of magnetic resonance imaging (MRI) assessment.

SUMMARY OF BACKGROUND DATA

Biofilm formed on the surface of the spinal implant prevents infiltration of antibiotics and makes the infection treatment more complicated. The decision of implant removal, if necessary, should be made appropriately, but the problem is a lack of consensus for implant removal or retention.

METHODS

A total of 1445 consecutive patients who underwent posterior instrumented lumbar fusion were reviewed retrospectively. There were 23 deep wound infections (1.6%) requiring surgical treatment. MR images were used to evaluate the presence or absence of osteomyelitis of the instrumented vertebra and intervertebral abscess.

RESULTS

Six patients in the negative MRI group (n=7) were successfully treated by a single salvage surgery without implant removal; fusion occurred in 86% of the patients. However, in the positive MRI group (n=13), 4 patients required implant removal at the initial surgery and 5 patients eventually warranted implant removal after an average of 2.4 additional operations. Notably, 3 of the 4 patients who kept the implants ended up with a loss of fixation stability attributed to screw loosening with a progressive destruction of the instrumented vertebra. Therefore, the fusion rate was only 23% for the MRI-positive patients. Furthermore, making a wrong decision regarding implant removal increased the number of salvage surgeries and frequently resulted in progressive bone destruction and pseudarthrosis.

CONCLUSIONS

Once vertebral osteomyelitis and/or intervertebral abscess were evident in MR images, all the hardware should be removed. Failure to adhere to this recommendation resulted in multiple additional failed operations, and ultimately pseudarthrosis with further bony destruction.