Abstract
To the Editor:
We have read with great interest the article entitled “Continuous epidural irrigation and drainage combined with posterior debridement and posterior lumbar inter-body fusion for the management of single-segment lumbar pyogenic spondylodiscitis” published recently in Surgical Infections [1]. In this study, Zhou et al [1] demonstrated inter-body fusion with instrumentation combined with continuous irrigation and drainage could be an effective management option for lumbar pyogenic spondylodiscitis with mild or moderate vertebral bony destruction. We may have several concerns about this study, however.
First, pre-operative biopsy of affected segments has not been performed. This is considered as an initial and mandatory step for potential pathogen identification and antimicrobial susceptibility testing before pre-operative antibiotic administration, especially for blood culture-negative cases. Moreover, the post-operative antibacterial regimen adjustment seems to be kind of unreasonable and non-targeted because of undetected pathogenic micro-organisms in eight of 18 consecutive patients.
It is noteworthy that spinal tuberculosis should be excluded either by pre- and post-operative tuberculosis-related assay or pathologic findings. It would be beneficial for better understanding of the prognosis of post-operative infection elimination, provided that more antibiotic regimen adjustment details of these patients could be revealed. In addition, streptomycin particles have been employed with bone grafting rather than commonly used vancomycin, which may hardly play a role under the circumstance of post-operative immediate continuous irrigation.
Second, the proposed surgical option for those patients with mild or moderate symptoms is still controversial. Aggravated neurologic deficit is the absolute indication for surgical management [2]. Among study participants, only five of 18 patients had neurologic deficits; the remaining patients complained of low back pain. Generally, it has been suggested the low back pain could be relieved rapidly by proper analgesic agents and bed rest, then cured subsequently by conservative rational antibiotic therapy [3].
The description of visual analog scale scoring for low back pain in this study is lacking standard error, which may compromise the reliability of the evaluation. Even if conservative treatment failed, instrumentation with posterolateral fusion could be performed alternatively instead of lumbar inter-body fusion.
Thorough and excessive debridement by the posterior approach mentioned in this article may destroy further the normal structure of the spinal column, devastating to potential stability. The clearance of paravertebral abscess via this approach will increase the risk of vessel injury. Besides, the non-structural bone allografting is also considered a risk factor for post-operative disc height loss and poor fusion rate, which may lead to final instrumentation failure.
The change of rod length beyond the upper pedicle screw profile in the representative case in anterior-posterior and lateral radiography images may indicate early loosening of the instrumentation (Fig. 2A, 2B, and Fig. 3A, 3B), assuming that the raw figures have been checked carefully and verified from the same patient.
Finally, the continuous irrigation for at least two weeks could increase the duration of hospitalization and bed rest time, which may raise the risk of peri-operative complications, especially for elderly patients with co-morbidities [4]. Notably, cerebrospinal fluid is a contraindication for continuous irrigation, which has not been mentioned in this study. Further, how to avoid the possible obstruction of the outflow drainage tube by necrosis tissue and clot would be interesting. Sending the outflow drainage for further germiculture detection would have contributed to underlying pathogen identification.
In summary, we believe that this study will lead to further investigations concerning surgical management options for pyogenic spondylodiscitis. It should be kept in mind, however, that proper decisions are much more important than incisions.