Prompted by relatively high infection rates associated with surgical treatment of pediatric spinal conditions such as scoliosis and spinal-deformity surgery in immunocompromised adults, spine surgeons have led “deep dive” clinical research into the possible benefits of local, intrawound antibiotic therapy. Consequently, the administration of antibiotic powder around the spine’s posterior elements and internal-fixation devices has become fairly widespread. But are there possible downsides to this approach that can impact patient outcomes?
This important question is addressed in the basic-science study by Ishida et al. in the October 2, 2019 issue of The Journal. The authors analyzed the fusion-specific impact of varying concentrations of intrawound vancomycin and tobramycin in a well-characterized rat model of posterolateral fusion performed with syngeneic iliac-crest allograft plus clinical bone-graft substitute. Ishida et al. found that a high dose of vancomycin (71.5 mg/kg, about 5 times higher than spine surgeons typically use) but not tobramycin had detrimental effects on fusion-mass formation in this model, as demonstrated by micro-computed tomography and histological analysis.
We now need further clinical research from the spine community to determine the optimal doses and types of intrawound antibiotics in this setting. Based on the currently available data, power calculations should be performed when designing future trials focused on this question. There seems to be little remaining doubt that locally delivered antibiotics help limit surgical-site and deep infections in spinal surgery. The impact of antibiotics on fusion rates must now be investigated further.
Marc Swiontkowski, MD
Every month, JBJS publishes a review of the most pertinent and impactful studies published in the orthopaedic literature during the previous year in one of 13 subspecialties. Click here for a collection of all OrthoBuzz subspecialty summaries.
This month, Kelly L. VanderHave, MD, co-author of the February 20, 2019 “What’s New in Pediatric Orthopaedics,” selected the five most compelling findings from among the more than 50 noteworthy studies summarized in the article.
—A before-and-after comparison found that, after implementation of a dedicated, weekday operating room reserved for pediatric trauma, length of stay for 5 common pediatric orthopaedic fractures was reduced by >5 hours. In addition, cost was reduced by about $1,200 per patient; complication rates improved slightly; frequency of after-hours surgery decreased by 48%; and wait times for surgery were significantly reduced.
—Forty-two patients with a distal radial buckle fracture received a removable wrist brace during an initial clinic visit, along with instructions to wear it for 3 to 4 weeks. No follow-up was scheduled, but the family was contacted at 1 week and at 5 to 10 months following treatment. No complications or refractures occurred; 100% of respondents said they would select the same treatment.1
Pediatric Sports Medicine
—Among a continuous cohort of 85 patients (mean age 13.9 years) who underwent primary ACL reconstruction (77% with open physes at time of surgery) and who were followed for a minimum of 2 years, overall prevalence of a second ACL surgery was 32%, including 16 ACL graft ruptures and 11 contralateral ACL tears. A slower return to sport was found to be protective against a second ACL injury.
Infection and Scoliosis Surgery
—A preliminary study of 36 pediatric patients who underwent a total of 191 procedures for early-onset scoliosis found that the use of vancomycin powder during closure significantly decreased the rate of surgical site infection (13.8% per procedure in the control group versus 4.8% per procedure in the vancomycin group).
—A retrospective review of >1,100 clubfeet that were presumed to be idiopathic upon presentation found that the condition in 112 feet (8.9%) was later determined to be associated with neurological, syndromic, chromosomal, or spinal abnormalities—and therefore nonidiopathic.2 The nonidiopathic group was less likely to have a good result at the 2- and 5-year follow-up, and more likely to require surgery. The authors conclude, however, that surgery is avoidable for most patients with nonidiopathic clubfoot.
- Kuba MHM, Izuka BH. One brace: one visit: treatment of pediatric distal radius fractures with a removable wrist brace and no follow-up visit. J Pediatr Orthop.2018 Jul;38(6):e338-42.
- Richards BS, Faulks S. Clubfoot infants initially thought to be idiopathic, but later found not to be. How do they do with nonoperative treatment?J Pediatr Orthop. 2017 Apr 10. [Epub ahead of print].
When it comes to preventing infections associated with orthopaedic procedures, the question of which antibiotic to use is only one of several concerns. How and where to administer antibiotics is another relevant question, not only in terms of infection-fighting effectiveness but also in terms of combatting the proliferation of antibiotic-resistant microbes.
In the September 19, 2018 issue of The Journal of Bone & Joint Surgery, Sweet et al. report on findings from a study in rats that compared the infection-prevention efficacy of intravenous (IV) cefazolin (n = 20) and IV vancomycin (n = 20) with local application of 4 antimicrobials—vancomycin powder (n = 20), cefazolin powder (n = 20), tobramycin powder (n = 20), and dilute Betadine lavage (n = 20).
The researchers induced infection by surgically implanting a polytetrafluoroethylene vascular graft near each rat’s thoracic spine and inoculating it with methicillin-sensitive Staphylococcus aureus (MSSA). After 7 days, all of the rats in each of the IV cefazolin, IV vancomycin, and Betadine lavage groups had grossly positive cultures for MSSA, “with bacterial colonies too numerous to count.” Ninety percent of the rats in the local cefazolin-powder group also had positive cultures, but the infection rates with vancomycin and tobramycin powder were much lower than those with the other four approaches (p <0.000001).
In addition to the main “disclaimer” about this study (namely, that its findings cannot be extrapolated to clinical practice in humans), the authors caution that “the effect of locally applied antibiotics on the emergence of resistant organisms is unknown,” while citing evidence that systemic administration of antibiotics is “associated with the emergence of resistant organisms at an alarming rate.”
Sweet et al. say they plan to follow up this study with a similar model to investigate the efficacy of local antimicrobials against the more problematic methicillin-resistant Staphylococcus aureus (MRSA)—and they suggest further that “clinical studies should be considered to determine the relative clinical efficacy of local versus systemic antibiotics for surgical infection prophylaxis in humans.”
When >10% of patients undergoing procedures to correct a spinal deformity develop one or more surgical-site infections, investigations into how to mitigate such infections seem warranted. This is especially true when a single such infection can cost nearly $1 million to treat—not to mention the physical and psychological burdens.
In the March 21, 2018 edition of JBJS, Thompson et al. report important findings from a retrospective study that sought to evaluate the efficacy of adding topical vancomycin powder to the wounds of patients undergoing growing-spine surgeries to address early-onset scoliosis. The mean patient age at the beginning of the study was 7.1 years.
Cases in which topical vancomycin powder was placed into the wounds at the time of fascial closure (n = 104 cases) had a significantly lower surgical-site infection rate (4.8%), compared with the rate in the 87 cases in which no vancomycin was used (13.8%). Furthermore, the “number needed to treat” found in this study was 11, meaning that for every 11 cases in which vancomycin powder was used, a surgical-site infection was prevented. The authors found no complications related to the use of topical vancomycin and note that their study provides the first evidence supporting the efficacy of vancomycin powder in pediatric spine patients.
Because this study was retrospective and based out of one center, further multicenter, prospective studies are needed to verify these results and to address open questions such as appropriate vancomycin dosages. Still, considering the extremely high costs (economic, physical, social, and psychological) associated with surgical-site infections in these complex patients, it appears that a vial of vancomycin powder costing between $10 and $40 may deliver outstanding value in these scenarios.
Chad A. Krueger, MD
JBJS Deputy editor for Social Media
Despite advances in sterile techniques and evidence-based use of perioperative antibiotics, periprosthetic joint infections still occur in 1% of primary and 3% to 7% of revision total joint arthroplasties. But a “smart” antimicrobial polymer coating, described in the July 20, 2016 Journal of Bone & Joint Surgery, has great potential to cut those percentages.
Stavrakis et al. devised a nontoxic, biodegradable polymer coating (called PEG-PPS for short) that locally delivers antibiotics (vancomycin and tigecycline in this study) both passively and actively, with the active release initiated by the presence of bacteria.
The authors tested the efficacy of the coating both in vitro and in vivo. In vitro, the release of antibiotics from the coating was enhanced in the presence of an oxidative environment, as would occur during a periprosthetic joint infection, demonstrating the coating’s “smartness.”
In vivo, using a mouse model of post-arthroplasty infection caused by Staphylococcus aureus, the authors showed radiographically that implants coated with PEG-PPS alone had a dramatic degree of periprosthetic osteolysis by postoperative day 7, compared with antibiotic-encapsulated PEG-PPS implants, which showed no detectable osteolysis. Similarly, the number of colony forming units of S. aureus cultured from implants on postoperative day 21 was significantly lower in the antibiotic-encapsulated implants than in the PEG-PPS-alone implants. (Interestingly, the tigecycline coating was more effective than the vancomycin coating in preventing bacterial colonization.)
While acknowledging that this proof-of-concept study needs to be replicated with other infectious organisms and in larger animals and humans, the authors conclude that PEG-PPS delivery of antibiotics has “great potential to minimize the incidence of postoperative infection following arthroplasty.”
A recent case-control study in Foot & Ankle International found that high-risk diabetic patients (mean age of 60) undergoing reconstructive foot and/or ankle surgery were 80% less likely to develop a deep surgical-site infection when surgeons applied vancomycin powder to the surgical wound than when they didn’t. The overall likelihood of any surgical-site infection (deep or superficial) was decreased by 73% in patients who received powdered vancomycin. The cost of vancomycin and the risk of complications associated with it are both low, the study noted.
The authors concluded that “based on this study, orthopaedic foot and ankle surgeons may consider applying 500 mg to 1,000 mg of vancomycin powder prior to skin closure in diabetic patients who are not allergic to vancomycin.”