Implant Survival After Deep Infection of an Instrumented Spinal Fusion

S. Nunez-Pereira, et al.

Spinal Unit, University of Barcelona, Spain

Bone and Joint 2013; 95-B: 1121-6

The authors evaluated the long-term survival of spinal implants after surgical site infection, in addition to the risk factors associated with treatment failure, analyzing 43 patients who had undergone an instrumented posterior spinal fusion and who developed an acute deep surgical site infection, all of whom were treated with surgical debridement and a specific antibiotic program based on cultures for a minimum of 8 weeks. 

The mean follow-up was 26 months.  Ten of the 43 patients, or 23% of the patients in this study, underwent implant removal and 1 died.  Four of the remaining 9 patients required re-instrumentation after implant removal and 2 of these 4 had a recurrent infection at the surgical site, and there was 1 recurrence of infection after implant removal without re-instrumentation.  The authors note that there is a significant risk factor for treatment failure in patients who develop sepsis (12.5%). 

The authors note that the rate of infection after posterior spinal fusion and instrumentation is reported to between 2 and 4%, and in certain specific populations, including patients with multiple injuries or neuromuscular disease, this can rise to 10%. 

They cite the standard accepted treatment for this type of complication is surgical debridement and prolonged administration of appropriate antibiotics, and the goals of treatment include elimination of infection and to retain the implants. 

Among the risks of removing the instrumentation is pseudarthrosis of the fusion, which can be as high as 37.9%.  They note the risk of uncontrolled or recurrent spinal infection, and they also note a 2 year probability of survival free of treatment failure of 71%. 

They have found that many patients require more than one surgical debridement, but noted that a second debridement was considered to be a treatment failure. 

They discuss the treatment for the different types of infections that occurred, including staphylococcal, MRSA, enterobacteriaceae, pseudomonas aeruginosa, E. coli, and proteus. 

A second debridement was performed when the wound continued to drain after the first debridement and washout and the inflammatory markers, white cell count and C-reactive protein, remained significantly elevated. 

Re-instrumentation after implant removal was indicated when there was progressive loss of correction after implant removal, second stage after removal of the implants, and 2 weeks of parenteral antibiotics in patients who had not fused at the time of the implant removal. 

They noted that of the 23% of patients who developed an infection and required re-instrumentation because of loss of correction, that half of these patients had a recurrent infection. 

They observed that the rate of implant removal does not stabilize until the end of the second year after the initial instrumented fusion.  They recommend 2 years of meticulous follow-up with repeated laboratory testing and imaging studies as appropriate for these patients who develop postoperative infections after posterior spinal instrumented fusions. 

The authors observed that the number of fused segments appear to be a predictor of treatment failure as these extensive procedures are associated with longer operating time and a greater requirement for transfusions.  They note that the 3 patients whose fusions included the sacrum all developed infection and had their implants removed.  They found that pelvic instrumentation requires an extensive surgical exposure and is associated with a high incidence of wound complications, including infection, which is partially explained by deficient soft tissue coverage and blood supply, which can interfere with wound healing and can lead to worse results when treating a postoperative infection. 

The authors noted that the presence of systemic sepsis and the need for additional debridement suggests the infection is more aggressive or that it is resistant to treatment. 

They strongly recommend early treatment and meticulous surveillance over 2 years.  They note that patients with long extensive surgical procedures on the spine are more inclined to develop relapse of their infection and more often than not will require removal of the implants and subsequent re-instrumentation. 

They recommend that this information should be provided to patients preoperatively. 

Editor’s Commentary:  The best and most effective preventative measure for postoperative spinal infection can be avoidance, if possible, of a spinal fusion. This paper provides a further red flag to physicians and surgeons to make a concerted effort in finding alternative or optional treatment methods for patients with chronic spinal conditions and especially those with degenerative conditions of the spine.  There are fewer options available obviously for many types of tumors, deformities, and traumatically induced instability. 

The failure rate of fusions for degenerative disease has been alarmingly high.  The process of finding alternative methods for surgery and particularly a fusion begins with a careful, thorough, and comprehensive examination of the patient, which includes a review of all available past medical records and a very careful interview or history of the patient.  You can never know too much about the patient’s relevant past medical history or their relevant present general medical condition.  Focusing on a specific area of the spine without assessing very carefully for all other risk factors that may be present could lead to a red flag situation.  

Sign-up for Email Updates