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Bacterial Deoxyribonucleic Acid (DNA) is Often Present in Ruptured Graft Tissue at Time of Revision Anterior Cruciate Ligament (ACL) Reconstruction

      Introduction

      Graft failure after primary anterior cruciate ligament reconstruction (ACLR) has been attributed to multiple risk factors. Colonization of graft tissue with low virulence bacteria could cause graft attenuation and predispose patients to ACL graft failure. Polymerase chain reaction (PCR) is highly sensitive and can detect bacteria in low concentrations, including strains that cannot be cultured. We hypothesize that bacterial DNA will be detectable via PCR in torn graft tissue at time of revision ACLR at higher rates than in primary ACLR graft tissue.

      Methods

      Thirty-one consecutive first time revision ACLR cases (mean age 28±5.1 years) and 5 primary ACLR controls (all hamstring autograft; mean age 27±4.6 years) from one center were included. No patients had clinical signs of infection. Among revisions, autograft was used in 22/31 (71%) and allograft in 9/31 (29%) at time of primary ACLR. Mean time to failure was 15.8 months (range 6 months-7 years). Samples were obtained with a previously unused set of instruments from the tibial tunnel in revision cases and from excess tibial sided graft after passage and fixation in primary cases. PCR analysis was performed with a universal bacterial probe.

      Results

      Bacterial DNA was detectable in torn graft tissue in most revision cases 27/31 (87.0%) and less commonly 1/5 (20%) in primary ACLR controls (p=0.002). Median DNA concentration in torn grafts during revision ACLR was low at 17.5 ng/ml (range 0-101) with no difference found between revision patients with allograft (median 18.6 ng/ml range 0-45) vs. autograft tissue (median 17.1 ng/ml range 0-105; p=0.56).

      Conclusion

      Bacteria is often present in torn graft tissue at time of revision ACLR and at much higher rates than seen from similar graft tissue samples from primary ACLR. These findings suggest likely bacterial colonization of many failed ACL grafts though the causal relationship between graft colonization and failure remains unclear.