Abstract

Background: 25-hydroxy Vitamin D (25[OH]D) level has been shown to have antimicrobial and wound healing effects in animal models. Low preoperative 25(OH)D has been shown to correlate with surgical site infection (SSI) in thoracolumbar spine surgery.

Methods: This study involved 545 patients undergoing thoracolumbar spine surgery from 2012 to 2019 at an academic medical center. We evaluated the serum 25(OH)D level (i.e., adequate level = level 30–60 ng/dL), along with SSI, body mass index, and smoking status. Statistical analysis was done using bivariate analysis with Fisher’s exact, Wilcoxon rank-sum test and multivarible logisitic regression analyses.

Results: We included 545 patients in the study, and there were no statistical differences in the average preoperative 25(OH)D between SSI and non-SSI groups. The average 25(OH)D in the non-SSI group was 31.6 ng/dL ± 13.6, and the SSI group was 35.7 ng/dL ± 20.2 (P = 0.63).

Conclusion: SSI rates following thoracolumbar spine surgery were not affected by preoperative 25(OH)D levels.

Keywords: Fusion, Laminectomy, Spine, Surgical site infection, Vitamin D

INTRODUCTION

Surgical site infection (SSI) following spine surgery can range from 0.2% to 16.7%.[ 6 , 7 ] Despite the importance of this topic, the current understanding of risk factors still needs to be improved.[ 8 ] In adult orthopedic surgery patients, the prevalence of Vitamin D hypovitaminosis has been noted to be 43%, likely increasing the rate of SSI.[ 1 , 4 ] SSI was defined as a deep SSI needing irrigation and debridement.[ 10 ] This study investigated whether low preoperative 25-hydroxy Vitamin D (25[OH]D) levels increased the risk of postoperative SSI following thoracolumbar spine surgery.

MATERIALS AND METHODS

With IRB approval, we evaluated Vitamin D levels in 545 patients undergoing thoracolumbar spine surgery (2012–2019) surgical procedures performed by one fellowship-trained orthopedic spine surgeon at a single academic center. The primary outcome of the study was the presence of SSI within 12 months of surgery (SSI group and non-SSI group).

Antibiotic protocol

All patients received preincisional antibiotics (cephalexin without penicillin allergy). During surgery, we utilized a solution containing povidone-iodine and normal saline irrigation of the wound while, followed by placement of intrawound vancomycin powder (i.e., above/below fascia lumbar/thoracic fusions 2 g, 1 g for lumbar laminectomies, and 250 mg for microdiscectomies).[ 4 , 5 , 9 ]

Most preoperative 25(OH)D levels were obtained within 30 days of surgery [ Table 1 ]. In our institution an adequate 25(OH)D was identified as 30-60 ng/dL. Greater than 60 ng/dL was identified as potentially harmful. Low 25(OH)D or deficiency (<20 ng/dL) and insufficient (21–29 ng/dL) levels were also defined.[ 3 ] Multiple other variables were studied [ Tables 2 and 3 ].

Table 1:

Bivariate analysis of Vitamin D data in non-SSI and SSI groups.

Table 2:

Multivariate logistic regression model using EOM guidelines.

Table 3:

Multivariate logistic regression model using IOM guidelines.

Statistical analysis

Bivariate analysis (i.e., using Fisher’s exact test and Wilcoxon rank-sum test) compared characteristics between nonSSI and SSI cohorts. We also utilized multivariable logistic regression analyses [ Tables 2 and 4 ].

Table 4:

Multivariate logistic regression model using Vitamin D as a continuous variable.

RESULTS

The average 25(OH)D in the non-SSI group was 31.6 ng/dL ± 13.6, and 35.7 ng/dL ± 20.2 in SSI group (p=0.63) [ Table 1 ].

Of 545 patients who met the inclusion criteria, the SSI rate was 1.65% (nine patients) [ Table 5 ].

Table 5:

Bivariate analysis of patient characteristics in non-SSI and SSI cohorts.

The SSI group had a higher proportion of smokers, 33.3%, versus 20.9% in the non-SSI group (P = 0.29) [ Table 5 ]. Most of the SSI group was identified as the American Society of Anesthesiologists (ASA) class 3 or 4 (62.5%), whereas most of the non-SSI group was identified as ASA 1 or 2 (53.6%, P = 0.29) [ Table 5 ]. There was no statistical significance in infection rates for revision compared to nonrevision surgeries (P = 0.61) [ Table 5 ].

Culture data

Six patients’ cultures grew single Gram positives (i.e., Bacillus species or Methicillin-sensitive Staphylococcus aureus [MSSA]) or Gram-negatives (i.e., Enterococcus faecalis, Proteus mirabilis) or two Pseudomonas species. Three patients’ cultures were polymicrobial and included Staphylococcus epidermis, Bacillus species, Micrococcus species; Enterococcus faecium, Escherichia coli, Klebsiella pneumoniae; P. mirabilis, diphtheroid species.

Multivariable analysis

We did not find a significant association between preoperative 25(OH)D levels and an increased risk for postoperative SSIs.

However, the odds of SSIs were lower among those with higher 25(OH)D levels (except for the potentially harmful group) [ Table 1 ]. We did not identify a statistical difference in SSI rates based on gender, age, surgery, smoking status revision surgery, diagnosis, diabetes mellitus, rheumatoid arthritis and 25(OH)D, and other factors identified in multivariable logistic regression analyses [ Tables 2 - 4 ].

DISCUSSION

We evaluated the role of preoperative 25(OH)D levels regarding the incidence of SSI following 545 thoracolumbar operations; 9 (1.65%) patients developed deep SSIs needing irrigation and debridement. There was no statistically significant difference in average preoperative 25(OH)D between non-SSI and SSI groups (P = 0.63), including multivariable analyses. We did not identify a higher risk of SSI in patients with higher body mass index, smoking, diabetes mellitus, rheumatoid arthritis, or ASA class. Donnally et al. performed a single-center retrospective study of 150 patients to investigate the relationship between 25(OH)D deficiency and outcome after lumbar spinal fusions.[ 2 ] They found no correlation between 25(OH)D and postoperative pseudarthrosis, revision, and instrumentation complications at 1 year [ Table 6 ].

Table 6:

Studies relating to SSI in the orthopedic surgery patient population and their outcome measures.

In contrast, Ravindra et al. examined the association between perioperative 25(OH)D and nonunion rates in elective spine surgery patients. They demonstrated that insufficient 25(OH)D was associated with prolonged time to fusion and a lower fusion rate.[ 6 ] Stoker et al. analyzed the prevalence of 25(OH)D in 313 patients undergoing spinal fusion at a single institution; 57% of the patients had 25(OH)D <30 ng/dL and 27% with levels <20 ng/dL [ Table 6 ].[ 8 ] In our study, the SSI group had a higher deficiency distribution <20 ng/dL than the non-SSI group (P = 0.041). Although our study did not identify a statistically significant correlation between 25(OH) D level and surgical infection rate, the odds of SSIs were lower among those with higher 25(OH)D (except for the potentially harmful group).

CONCLUSION

Our study showed no significant differences in preoperative 25(OH)D levels between non-SSI and SSI groups undergoing 545 patients with thoracolumbar surgery.

Ethical approval

The research/study was approved by the Institutional Review Board at the University of Rochester, number STUDY00000497, dated 2015.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship

Nil.

Conflicts of interest

Addisu Mesfin MD: Speaker fees Depuy, Grant Nuvasive, Lodging/travel Medtronic.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

References

1. Bogunovic L, Kim AD, Beamer BS, Nguyen J, Lane JM. Hypovitaminosis D in patients scheduled to undergo orthopaedic surgery: A single-center analysis. J Bone Joint Surg Am. 2010. 92: 2300-4

2. Donnally CJ, Sheu JI, Bondar KJ, Mouhanna JN, Li DJ, Butler AJ. Is there a correlation between preoperative or postoperative vitamin D levels with pseudarthrosis, hardware failure, and revisions after lumbar spine fusion?. World Neurosurg. 2019. 130: e431-7

3. Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney RP. Evaluation, treatment, and prevention of vitamin D deficiency: An endocrine society clinical practice guideline. J Clin Endocrinol Metab. 2011. 96: 1911-30

4. Mesfin A, Baldwin A, Bernstein DN, Emanski E, Molinari R, Menga E. Reducing surgical site infections in spine tumor surgery: A comparison of three methods. Spine. 2019. 44: E1428-35

5. Onishi Y, Masuda K, Tozawa K, Karita T. Outcomes of an intraoperative povidone-iodine irrigation protocol in spinal surgery for surgical site infection prevention. Clin Spine Surg. 2019. 32: E449-52

6. Ravindra VM, Godzik J, Dailey AT, Schmidt MH, Bisson EF, Hood RS. Vitamin D levels and 1-year fusion outcomes in elective spine surgery: A prospective observational study. Spine. 2015. 40: 1536-41

7. Schimmel JJ, Horsting PP, De Kleuver M, Wonders G, Van Limbeek J. Risk factors for deep surgical site infections after spinal fusion. Eur Spine J. 2010. 19: 1711-9

8. Stoker GE, Buchowski JM, Bridwell KH, Lenke LG, Riew KD, Zebala LP. Preoperative vitamin D status of adults undergoing surgical spinal fusion. Spine. 2013. 38: 507-15

9. Ter Gunne AF, Cohen DB. Incidence, prevalence, and analysis of risk factors for surgical site infection following adult spinal surgery. Spine (Phila Pa 1976). 2009. 34: 1422-8

10. Zajonz D, Prager F, Edel M, Möbius R, Daikos A, Fakler JK. The significance of the vitamin D metabolism in the development of periprosthetic infections after THA and TKA: A prospective matched-pair analysis of 240 patients. Clin Interv Aging. 2018. 13: 1429-35