mNGS Trial Examines Hidden Bacterial Burden in Primary Cervical Fusion
Hospital for Special Surgery is launching a diagnostic study that asks a narrow but clinically important question: what bacteria are present at the surgical site during primary anterior cervical discectomy and fusion, and how much does standard culture miss? The protocol, Assessing Microbiome in Primary Anterior Cervical Fusion Patients (NCT07877766), will enroll an estimated 76 adults undergoing primary ACDF involving one to three contiguous cervical levels. Investigators will compare traditional aerobic and anaerobic microbiology with metagenomic next-generation sequencing, or mNGS, using intraoperative swab samples collected during surgery.
The logic is straightforward. Instrumentation creates a surface where bacteria can adhere, persist, and organize into biofilm, a protected microbial community that is far harder to eradicate than free-floating organisms. Once biofilm establishes itself on hardware, the clinical stakes rise quickly: persistent inflammation, impaired fusion, loosening, and hard-to-interpret postoperative symptoms can follow. By sampling the operative field directly and comparing two laboratory approaches, the study is designed to determine whether contemporary microbiology fully captures the bacterial flora present around cervical implants.
One sentence captures the central uncertainty: standard culture may be too blunt for the microbial ecology of spine surgery.
Swab Sampling Will Compare Culture With Metagenomic Sequencing
The study is interventional, open label, and single-group, but the intervention is procedural rather than pharmacologic. During primary anterior cervical discectomy procedures, clinical swabs will be taken from the surgical site and analyzed by routine culture methods as well as metagenomic sequencing. The primary purpose is diagnostic, not therapeutic, and the investigators are not randomizing participants to alternate operations or implant strategies.
This design matters because the biologic question sits at the interface of microbiology and surgical outcomes. Standard culture can identify organisms that grow under aerobic or anaerobic conditions, yet it does not necessarily recover the full community of bacteria present in low-burden or fastidious states. mNGS can broaden that view by detecting microbial genetic material directly, potentially revealing organisms that would otherwise remain invisible. In a field where implant colonization can seed biofilm formation, identifying a broader bacterial signal could influence how surgeons think about contamination, postoperative surveillance, and the biology of fusion failure.
The study population is tightly defined. Eligible participants are adults between 18 and 80 years old who are medically cleared for surgery and able to provide written informed consent. All must be scheduled for primary anterior cervical discectomy and fusion at one to three contiguous levels. Patients with active systemic infection, infection at the operative site, prior cervical surgery at the operative level, prior cervical fusion at any level, major congenital spinal abnormalities, or prior cervical trauma with significant injury are excluded. The protocol also excludes pregnancy, breastfeeding, active malignancy, autoimmune musculoskeletal disease, substantial osteoporosis risk, and several other conditions that could complicate healing or interpretation of postoperative findings.
Fusion, Loosening, and Pain Outcomes Extend the Diagnostic Lens
Although the primary endpoint centers on bacterial detection, the follow-up window reaches well beyond the operating room. Secondary outcomes include visual analog scale scores for neck pain and arm pain, Neck Disability Index scores, radiographic fusion, radiographic screw lucency or loosening, and surgery-related adverse events through one year postoperatively. Those outcomes give the study clinical context. Bacterial detection is not just an academic exercise when the downstream questions involve fusion biology, implant stability, and patient-reported recovery.
The choice of radiographic fusion and screw loosening as outcomes is particularly relevant in the setting of possible occult microbial burden. Biofilm-associated organisms can create a low-grade inflammatory environment that may interfere with osseointegration and tissue healing long before a frank infection becomes obvious. Even when patients do not present with classic signs of infection, subtle microbial persistence could still shape the mechanical and symptomatic course after fusion. Neck pain, arm pain, and disability scores will therefore serve as practical readouts of whether surgical recovery tracks with the microbiologic findings.
One unusual feature of the protocol is its emphasis on occult infection rather than overt sepsis or wound infection. That focus reflects a growing recognition in spine surgery that conventional clinical screening can miss microbial activity at the time hardware is implanted. The record also lists a related publication from the same investigative group on the prevalence of occult infections in posterior instrumented spinal fusion. While the current study is confined to the cervical spine and uses an anterior approach, the conceptual bridge is obvious: hidden organisms may be more common, and more clinically relevant, than surface-level postoperative assessments suggest.
Cervical Spine Surgery Faces a Persistent Microbiology Problem
Primary ACDF is a common operation for cervical stenosis, myelopathy, cervical spondylosis with myelopathy, degenerative disc disease, and radiculopathy. When surgery involves instrumentation, the microbial environment around the implant becomes part of the biologic story of recovery. Standard perioperative practice has long relied on cultures when infection is suspected, but low-burden organisms and biofilm-associated bacteria can elude routine methods. mNGS offers a different lens, one that could expose a more complex microbial signature at the moment of implantation.
That possibility has practical consequences. If mNGS detects bacterial DNA where culture is negative, surgeons may eventually need to rethink how they interpret a “clean” operative field, especially in patients who later develop pain, lucency, or delayed fusion. If the two methods largely agree, conventional microbiology may remain sufficient for this setting. Either result would inform how the field approaches cervical hardware, postoperative surveillance, and the search for biologic explanations when fusion does not proceed as expected.
The study began on October 14, 2025, with primary completion estimated for May 20, 2027 and final completion for July 1, 2027. Until then, the protocol remains a diagnostic probe into a familiar operation with an unresolved microbial dimension. The central issue is not whether ACDF can be performed, but whether current microbiology can actually see the bacteria that matter once implants enter the cervical spine.