Implant-Associated Spinal Infections in Children

Perioperative and early complications of extended instrumental fixation for spinal deformity in children: what does the application of the Clavien – Dindo classification reveal and what questions does it raise?

Objective. To analyze complications of extended posterior instrumental fixation for spinal deformity in children in accordance with the Clavien – Dindo classification and to assess its information content and limitations.

Material and Methods. A retrospective single-center cohort study included 136 patients aged from 1 year to 17 years 11 months consecutively operated in 2020–2023 for thoracic and lumbar spine deformities associated with congenital, neuromuscular, syndromic, idiopathic scoliosis and Scheuermann’s kyphosis. At least four spinal motion segments were included in the zone of posterior instrumental fixation. All perioperative events and postoperative complications noted in the medical records were registered in accordance with the Clavien – Dindo classification. An analysis of factors influencing the development of complications of grade IIIB and higher was carried out.

Results. With a total apparent high number of complications/events (55 or 40.4 % of the number of operations), the vast majority of them correspond to grade I–II (41; 30.1 %) and do not affect the tactics and outcome of treatment. Complications of grade III and IV were noted in 13 (9.6 %) cases, and of grade V – in 1 (0.7 %) case. The influence of deformity etiology, gender, age or underweight on the risk of grade IIIB and IVA complications was not revealed, which may be due to the limited number of observations. The installation of more than 18 transpedicular screws, which correlated with surgery duration and blood loss volume, was significant for the development of such complications. The results obtained were compared with those presented in the literature, the information content and limitations of the use of the Clavien – Dindo classification in spine surgery were discussed.

Conclusion. A significant part of the complications of spinal deformity correction in children is conventionally not taken into account in domestic practice and, accordingly, cannot be prevented. The use of the Clavien – Dindo classification allows estimating the frequency of complications that potentially do not affect (grade I–II) and affect (grade III–IV) the tactics of postoperative treatment and outcomes. The installation of 18 or more supporting elements of instrumentation is directly related to surgery duration, intraoperative blood loss volume and the risk of developing grade IIIB and IVA complications. Larger data sets are needed for a more objective analysis of the risk of severe complications for each nosology.

A novel rodent model of chronic spinal implant-associated infection

BACKGROUND CONTEXT

Bacterial infection of spinal instrumentation is a significant challenge in spinal fusion surgery. Although the intraoperative local application of powdered vancomycin is common practice for mitigating infection, the antimicrobial effects of this route of administration are short-lived. Therefore, novel antibiotic-loaded bone grafts as well as a reliable animal model to permit the testing of such therapies are needed to improve the efficacy of infection reduction practices in spinal fusion surgery.

PURPOSE

This study aims to establish a clinically relevant rat model of spinal implant-associated infection to permit the evaluation of antimicrobial bone graft materials used in spinal fusion.

STUDY DESIGN

Rodent study of chronic spinal implant-associated infection.

METHODS

Instrumentation anchored in and spanning the vertebral bodies of L4 and L5 was inoculated with bioluminescent methicillin-resistant Staphylococcus aureus bacteria (MRSA). Infection was monitored using an in vivo imaging system (IVIS) for 8 weeks. Spines were harvested and evaluated histologically, and colony-forming units (CFUs) were quantified in harvested implants and spinal tissue.

RESULTS

Postsurgical analysis of bacterial infection in vivo demonstrated stratification between MRSA and phosphate-buffered saline (PBS) control groups during the first 4 weeks of the 8-week infection period, indicating the successful establishment of acute infection. Over the 8-week chronic infection period, groups inoculated with 1 × 105 MRSA CFU and 1 × 106 MRSA CFU demonstrated significantly higher bioluminescence than groups inoculated with PBS control (p = 0.009 and p = 0.041 respectively). Histological examination at 8 weeks postimplantation revealed the presence of abscesses localized to implant placement in all MRSA inoculation groups, with the most pervasive abscess formation in samples inoculated with 1 × 105 MRSA CFU and 1 × 106 MRSA CFU. Quantification of CFU plated from harvested spinal tissue at 8 weeks post-implantation revealed the 1 × 105 MRSA CFU inoculation group as the only group with a significantly greater average CFU count compared to PBS control (p = 0.017). Further, CFU quantification from harvested spinal tissue was greater than CFU quantification from harvested implants across all inoculation groups.

CONCLUSION

Our model demonstrated that the inoculation dosage of 1 × 105 MRSA CFU exhibited the most robust chronic infection within instrumented vertebral bodies. This dosage had the greatest difference in bioluminescence signal from control (p < 0.01), the lowest mortality (0% compared to 50% for samples inoculated with 1 × 106 MRSA CFU), and a significantly higher amount of CFUs from harvested spine samples than CFUs from control harvested spine samples. Further, histological analysis confirmed the reliability of this novel rodent model of implanted-associated infection to establish infection and biofilm formation of MRSA for all inoculation groups.

CLINICAL SIGNIFICANCE

This model is intended to simulate the infection of instrumentation used in spinal fusion surgeries concerning implant locality and material. This model may evaluate potential antimicrobial and osteogenic biomaterials and investigate the relationship between implant-associated infection and failed fusion.