Occult Infections: A possible risk factor pseudoarthrosis?

Introduction: The root cause of pseudoarthrosis after spinal revision is rarely known. There are many hypotheses however, there has been little discussion regarding occult infections as a risk factor. The goal of this study was to examine the occurrence of bacterial infections in patients undergoing spinal revision due to pseudoarthrosis and its effect on patient outcomes.

Methods: This was a retrospective observational study. 106 patients diagnosed with pseudoarthrosis who underwent spinal fusion revision with one neurosurgeon at one institution between 2013-2021 were examined. Out of the 106 cases, 72.64% (77/106) of the patients had explanted hardware samples sent to pathology for further testing.

Results: Among the 77 patients who had samples of explanted hardware examined, evidence of infection was found in 11.6% (9/77) of the cases. A sub-analysis of the anatomical distribution of these 9 patients was explored. In the cervical region, infections were attributed to the presence of Propionibacterium Acnes and Klebsiella microorganisms, resulting in an infection rate of 22.22% (2/9). In lumbar surgeries, infections were associated with a combination of Methicillin-Resistant Staphylococcus aureus, Staphylococcus aureus, Proteus Mirabilis, and Anaerobic gram-negative rods, yielding an infection rate of 7.41% (2/27). Meanwhile, lumbosacral surgeries had infections caused by Staphylococcus Aureus and Staphylococcus Epidermidis, leading to an infection rate of 13.33% (2/15). The thoracic procedures exhibited an infection rate of 50.00% (3/6), attributed to Staphylococcus epidermidis, Corynebacterium growth, Proteus mirabilis, and Acinetobacter. Notably, the thoracolumbar, cervicothoracic, and sacroiliac regions reported an infection rate of 0.00%; 0/11, 0/6, and 0/2, respectively.

Conclusion : Although the data did not support a clear correlation between pseudoarthrosis and the presence of occult infection, further investigation is warranted. The data does however, suggest that thoracic spinal revision may be more prone to infection than other regions and further research could be done to determine its clinical significance.