Surgical wound infection after lumbar spine surgery is one of the most feared complications in orthopedics. It can prolong hospitalization, drive ninety-day readmissions, force revision operations, and leave patients with lasting pain and disability, all while imposing a substantial financial burden on health systems. Because these infections can be catastrophic when missed, surgeons have long searched for simple laboratory signals that could flag trouble early. White blood cell count and the neutrophil-to-lymphocyte ratio, a calculated measure obtained by dividing the absolute neutrophil count by the absolute lymphocyte count on a standard complete blood count, are attractive candidates because they are cheap, universally available, and already ordered for most surgical patients.

The problem, as prior studies have hinted, is that the first twenty-four hours after major surgery are biologically noisy. Tissue trauma, perioperative medications, hemodilution from intravenous fluids, physiologic stress responses, and obesity can all drive leukocytosis and shift the differential toward neutrophils, producing elevations that mimic infection without any infectious biology at all. Body mass index, the extent of tissue dissection, the number of operative levels, and the duration of the operation all leave fingerprints on the early inflammatory response. The research team, led by corresponding author Jay Chung of Albert Einstein College of Medicine, set out to test whether the early markers could still say something meaningful about wound infection once those confounding factors were taken into account.

The study was a retrospective cohort analysis of prospectively collected data from adults who underwent elective one- to three-level lumbar fusion between 2022 and 2024 at a single academic medical center. Of 462 cases screened from a source registry, 380 patients formed the outcome-eligible analytic cohort. The researchers excluded surgeries performed for cancer or infection and all emergency procedures, and they required ninety-day outcome follow-up and at least one complete postoperative blood count. Laboratory analyses used complete-case denominators: day-one values were available in 368 patients, day-three values in 336, and paired day-one and day-three values in 327 patients.

The primary outcome, termed surgical wound infection, was defined pragmatically from the electronic health record as a documented clinical wound infection or wound-related infectious complication requiring antibiotic therapy, wound intervention, or reoperation within ninety days of surgery. The authors are explicit that this endpoint is not equivalent to a uniformly culture-confirmed deep infection, an implant-associated infection, or the standardized surveillance definitions used by the CDC’s National Healthcare Safety Network or the American College of Surgeons NSQIP program. Among the eighteen patients classified as having a wound infection, nine returned to the operating room for washout or wound management, seven had nonoperative wound complications or interventions documented, and two were treated clinically with antibiotics alone.

When the researchers compared patients who developed wound infections with those who did not, two factors stood out immediately: infected patients had higher body mass index, more frequent morbid obesity, and longer operative duration. On the laboratory side, day-one white blood cell count and day-one neutrophil-to-lymphocyte ratio were associated with wound infection in simple univariable models, but those associations faded after adjustment for body mass index and operative time. In other words, the apparent signal on the first postoperative day was largely explained by the patient’s body habitus and the scale of the operation, not by infection-specific biology.

Day three told a more interesting story. By that point, the acute inflammatory response typically begins to settle, and in this cohort both white blood cell count and neutrophil-to-lymphocyte ratio declined significantly from day one to day three across the paired cohort. After adjustment for body mass index and operative duration, day-three white blood cell count remained associated with wound infection with an odds ratio of 1.17 per unit increase, and day-three neutrophil-to-lymphocyte ratio showed an odds ratio of 1.12. Patients who developed infections also had a higher median day-three ratio, 5.1 compared with 3.7 among uninfected patients. Yet the picture grew murkier in sensitivity analyses: when the corresponding day-one value was added to the models, the day-three associations weakened, and neither the absolute nor the percentage change from day one to day three differed significantly between infected and uninfected patients.

The authors are careful to frame these results as exploratory rather than practice-changing. With only eighteen infection events, the regression models were deliberately kept parsimonious to avoid overfitting, and a planned sensitivity analysis restricted to the nine patients who required return to the operating room was abandoned because the estimates would have been unstable. The study did not develop diagnostic thresholds, receiver operating characteristic curves, sensitivity or specificity estimates, or any validated prediction model. The researchers also compared patients with complete paired laboratory values against those without, finding that the paired-lab group had longer operations, greater blood loss, longer hospital stays, and more open procedures, a form of selection bias that may limit how broadly the trajectory findings generalize, particularly to patients discharged before day-three testing.

Several additional limitations shape the interpretation. Detailed microbiologic data were not consistently available, so culture status, causative organisms, and infection depth could not be reported uniformly. C-reactive protein, erythrocyte sedimentation rate, procalcitonin, and albumin, markers commonly tracked after spine surgery in prior studies, were not measured, limiting comparison with earlier work such as studies identifying day-four lymphocyte count and day-seven C-reactive protein as markers less affected by operative variables. White blood cell count and the neutrophil-to-lymphocyte ratio are also nonspecific and can rise with urinary tract infections, pulmonary complications, or other systemic illness that the study did not fully adjudicate. Residual confounding by factors such as ASA class, drain use, and immunosuppressive therapy remains possible.

What the study does offer is a disciplined reminder about surgical context. Immediate postoperative inflammatory markers are strongly influenced by who the patient is and what the operation entailed, and an isolated day-one elevation may simply reflect the trauma of surgery rather than early infection. Day-three values, particularly the neutrophil-to-lymphocyte ratio, may retain a residual exploratory association with wound complications, but even that signal attenuates once the day-one baseline is considered. The authors call for larger, prospective, multicenter studies to determine whether any clinically useful thresholds can be established, and they caution that their findings should not guide clinical protocols until such validation is complete. For now, the message to clinicians is one of restraint: interpret the early postoperative blood count through the lens of the patient and the operation, and resist the temptation to treat a single number as a diagnosis.

Subject of Research: Postoperative inflammatory blood markers and surgical wound infection after elective short-segment lumbar fusion

Article Title: Postoperative inflammatory markers and surgical wound infection after elective short-segment lumbar fusion: the importance of surgical context

Article References: Chung, J., Rocker, T., Golding, R., Mehta, S., McFarland, M., Gupta, A., Yang, X., Singh, P., Olsen, E., Balusu, S., Lo, Y., Zuckerman, P., Shaw, J. D., & Fourman, M. S. (2026). Postoperative inflammatory markers and surgical wound infection after elective short-segment lumbar fusion: the importance of surgical context. Journal of Bone and Joint Infection, 11(4), 503-511. https://doi.org/10.5194/jbji-11-503-2026

Image Credits: AI Generated

DOI: 10.5194/jbji-11-503-2026

Keywords: lumbar fusion, surgical wound infection, white blood cell count, neutrophil-to-lymphocyte ratio, postoperative inflammation, spine surgery, surgical site infection, retrospective cohort, inflammatory markers, operative duration, body mass index, electronic health record