SOLARIO: Short Antibiotics Noninferior After Orthopedic Infection

Key Takeaways

• Among adults who underwent surgery for orthopedic infection and received a local-antibiotic carrier, short postoperative systemic antibiotics were reported as noninferior to longer therapy for definite treatment failure at 12 months.
• Definite treatment failure was numerically lower with the shorter regimen than with longer treatment, in a comparison that met the trial's noninferiority threshold.
• Sensitivity analyses in the included-population and per-protocol cohorts were consistent with the primary finding.
• Symptoms potentially related to treatment by 6 weeks were less frequent with the shorter postoperative regimen.

Prolonged postoperative systemic antibiotics remain common after surgery for orthopedic infection, even when local antibiotics are implanted at the infection site. In adults treated with surgery plus a local-antibiotic carrier, the unresolved question was whether systemic therapy could be shortened without increasing later treatment failure. Investigators tested that question in a randomized comparison.

Investigators conducted the multicenter, open-label, randomized noninferiority Short or Long Antibiotic Regimens in Orthopedics (SOLARIO) trial in adults who had undergone surgery for orthopedic infection and implantation of a local-antibiotic carrier. Patients were assigned in a 1:1 ratio to short postoperative systemic antibiotic therapy, defined as 7 days or less, or long therapy, defined as 4 weeks or more.

A total of 500 patients underwent randomization, and 475 were assessed in the primary analysis. The primary outcome was definite treatment failure by 12 months, assessed with protocol-defined criteria by a clinical end-point committee unaware of treatment assignment, and the prespecified noninferiority margin was 10 percentage points.

Definite treatment failure occurred in 34 of 241 patients (14.1%) in the long-duration group and 26 of 234 patients (11.1%) in the short-duration group, for a risk difference of -3.0 percentage points (95% confidence interval, -9.0 to 3.0), which met the prespecified noninferiority margin. Sensitivity analyses in the included-population and per-protocol cohorts were consistent with the primary analysis.

By week 6 after surgery, symptoms potentially related to treatment had occurred in 45.2% of the long-duration group and 17.2% of the short-duration group, for a risk difference of -28.0 percentage points (95% confidence interval, -36.4 to -19.6).

According to the investigators, among patients who had undergone orthopedic surgery and received local antibiotics, short-course systemic therapy was noninferior to longer therapy with respect to definite treatment failure by 12 months.

Clinician Questions

Which patients does the SOLARIO trial apply to after orthopedic infection surgery?

The randomized comparison involved adults who had undergone surgery for orthopedic infection and received implantation of a local-antibiotic carrier, with postoperative systemic antibiotics assigned to short or long duration. The findings are therefore bounded to that postoperative surgical setting with local antibiotic implantation rather than to all orthopedic infections.

How was definite treatment failure assessed in the SOLARIO trial?

Definite treatment failure was the primary outcome at 12 months and was assessed according to protocol-defined criteria by a clinical end-point committee whose members were unaware of treatment assignment. That adjudication process defined how the main outcome comparison was determined in this postoperative population.