Background Spinal surgeries after traumatic thoracic or thoracolumbar spinal cord injuries (SCI) often involve extensive instrumentation, leading to an increased risk of surgical site infections (SSIs) and complications. This study investigates whether the number of spinal levels fused impacts functional recovery and the frequency of SSIs in individuals with vertebral fractures in the thoracic and/or lumbar spine and SCI. Methods In this retrospective analysis of 282 patients with traumatic thoracic or thoracolumbar SCI, data across two periods (2005 - 2009 vs. 2018 - 2022) were compared, including variables such as demographics, setting of the initial surgery (specialized SCI center or general trauma center), SCI severity, number of levels fused, fracture classification, the need for revision surgery, the presence of polytrauma and/or traumatic brain injury (TBI), and the occurrence of SSIs during hospitalization. Functional independence was assessed using the Spinal Cord Independence Measure (SCIM III). Unbiased recursive partitioning (URP-CTREE) was used to identify predictors of SSIs and functional outcomes. Results Patients undergoing longer fusions had a significantly higher rate of SSIs (median fusion length: 5 vs. 3 levels, p = 0.02). Revision surgery and age over 57 were identified as key predictors of SSIs. Shorter fusions (two spinal segments or less) were associated with better functional recovery, particularly in more severe SCI (AIS A, B, or C). Conclusion Longer fusion lengths increase the risk of SSIs and are linked to poorer functional outcomes in patients with thoracic and thoracolumbar SCI. Minimizing fusion length might optimize surgical outcomes and reduce complications. Future research should refine surgical strategies to balance stability with functional recovery.

The authors have declared no competing interest.

No funding was received for this study.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

All individuals provided written informed consent permitting the use of their medical data for research purposes as part of their participation in the European Multicenter Study about Spinal Cord Injury (EMSCI) registry. The EMSCI has been approved by the Ethics Committee of the University of Heidelberg (Vote no. S-188/2003, Amendment 9).

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

The deidentified participant data utilized in this study, as well as additional related documents (study protocol, statistical analysis plan) can be made available upon reasonable request to the corresponding author. Access to the data will be subject to approval by institutional and ethical considerations.