Contamination occurs during ACL graft harvesting and manipulation, but it can be easily eradicated.

PURPOSE: Why anterior cruciate ligament (ACL) autograft soaking in a 5 mg/ml vancomycin solution decreases the rate of infection has not been well-explained. One hypothesis is that grafts can be contaminated during harvesting and vancomycin eradicates the bacteria. The purpose of the present study is to assess how the vancomycin solution acts against ACL graft contamination during graft harvesting and preparation. METHODS: The study was carried out in three university hospitals over a period of 6 months. After sample size calculation, 50 patients were included in the study. Three samples were taken from each ACL graft. Sample 1 was obtained immediately after graft harvesting. After graft manipulation and preparation, the remaining tissue was divided into two parts. The raw sample was denominated sample 2 and sample 3 consisted of the rest of the remaining tissue that had been soaked in the vancomycin solution. All the cultures were incubated at 37 °C with 5% CO2 in agar plates for 7 days (aerobically) or 14 days (anaerobically) and inspected daily for microbial growth. Any bacterial growth and the number of colony forming units were reported. RESULTS: In seven cases (14%), either sample 1 or sample 2 was positive. In five of the cases (10%), only the sample after graft preparation was positive (sample 2). In two cases (4%), sample 1 and sample 2 were positive for the same bacteria. Isolated microorganisms corresponded to coagulase-negative staphylococci (CNS) and Propionibacterium acnes. No bacterial growth was observed in sample 3 (p < 0.001). Thus, none of those seven positive cases (0%) were positive after vancomycin soaking (p < 0.001). CONCLUSION: In the series, ACL graft harvesting and manipulation leads to bacterial contamination in 14% of the cases. This contamination is fully eradicated after soaking in the vancomycin solution in this series. LEVEL OF EVIDENCE: Level II.

Presence of Bacteria in Spontaneous Achilles Tendon Ruptures.

BACKGROUND: The structural pathology of Achilles tendon (AT) ruptures resembles tendinopathy, but the causes remain unknown. Recently, a number of diseases were found to be attributed to bacterial infections, resulting in low-grade inflammation and progressive matrix disturbance. The authors speculate that spontaneous AT ruptures may also be influenced by the presence of bacteria. HYPOTHESIS: Bacteria are present in ruptured ATs but not in healthy tendons. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Patients with spontaneous AT ruptures and patients undergoing anterior cruciate ligament (ACL) reconstruction were recruited for this study. During AT surgical repair, excised tendinopathic tissue was collected, and healthy tendon samples were obtained as controls from hamstring tendon grafts used in ACL reconstruction. Half of every sample was reserved for DNA extraction and the other half for histology. Polymerase chain reaction (PCR) was conducted using 16S rRNA gene universal primers, and the PCR products were sequenced for the identification of bacterial species. A histological examination was performed to compare tendinopathic changes in the case and control samples. RESULTS: Five of 20 AT rupture samples were positive for the presence of bacterial DNA, while none of the 23 hamstring tendon samples were positive. Sterile operating and experimental conditions and tests on samples, controlling for harvesting and processing procedures, ruled out the chance of postoperative bacterial contamination. The species identified predominantly belonged to the Staphylococcus genus. AT rupture samples exhibited histopathological features characteristic of tendinopathy, and most healthy hamstring tendon samples displayed normal tendon features. There were no apparent differences in histopathology between the bacterial DNA-positive and bacterial DNA-negative AT rupture samples. CONCLUSION: The authors have demonstrated the presence of bacterial DNA in ruptured AT samples. It may suggest the potential involvement of bacteria in spontaneous AT ruptures.

Does sterilization with fractionated electron beam irradiation prevent ACL tendon allograft from tissue damage?

PURPOSE: Allografts are frequently used for anterior cruciate ligament (ACL) reconstruction. However, due to the inherent risk of infection, a method that achieves complete sterilization of grafts is warranted without impairing their biomechanical properties. Fractionation of electron beam (FEbeam) irradiation has been shown to maintain similar biomechanical properties compared to fresh-frozen allografts (FFA) in vitro. Therefore, aim of this study was to evaluate the biomechanical properties and early remodelling of grafts that were sterilized with fractionated high-dose electron beam irradiation in an in vivo sheep model. METHODS: ACL reconstruction was performed in 18 mature merino mix sheep. Sixteen were reconstructed with allografts sterilized with FEbeam irradiation (8 × 3.4 kGy) and two with FFA. Eight FFA from prior studies with identical surgical reconstruction and biomechanical and histological analyzes served as controls. Half of the animals were sacrificed at 6 and 12 weeks, and biomechanical testing was performed. Anterior-posterior laxity (APL) was assessed with an AP drawer test at 60° flexion, and load to failure testing was carried out. Histological evaluation of mid-substance samples was performed for descriptive analysis, cell count, crimp and vessel density. For statistical analysis a Kruskal-Wallis test was used for overall group comparison followed by a Mann-Whitney U test for pairwise comparison of the histological and biomechanical parameters. RESULTS: Biomechanical testing showed significantly decreased stiffness in FEbeam compared to FFA at both time points (p ≤ 0.004). APL was increased in FEbeam compared to FFA, which was significant at 6 weeks (p = 0.004). Median of failure loads was decreased in FEbeam grafts, with 12 reconstructions already failing during cyclic loading. Vessel density was decreased in FEbeam compared to FFA at both time points, with significant differences at 12 weeks (p = 0.015). Crimp length was significantly shorter in FEbeam compared to FFA at both time points (p ≤ 0.004) and decreased significantly in both groups from 6 to 12 weeks (p ≤ 0.025). CONCLUSION: ACL reconstruction with fractionated Ebeam sterilization significantly alters the biomechanical properties and the early remodelling process of treated grafts in vivo. Therefore, this sterilization method cannot be recommended for clinical application. As substantial changes in the remodelling are inherent in this study, care in the rehabilitation of even low-dose sterilized allografts, used for ACL reconstruction, is recommended.

The incidence of and clinical approach to positive allograft cultures in anterior cruciate ligament reconstruction.

OBJECTIVE: To define the incidence of positive allograft cultures in anterior cruciate ligament (ACL) reconstruction and to determine a clinical approach to a positive test. DESIGN: Retrospective chart review, cohort series. SETTING: Urban academic hospital. PATIENTS: All patients who underwent anterior cruciate ligament reconstruction using allograft between January 2003 and December 2008. One hundred fifteen patients met the inclusion criteria. INTERVENTIONS: Culture of allograft before surgical implantation. MAIN OUTCOME MEASURES: Positive allograft culture. RESULTS: Positive allograft cultures were obtained in 3 of 115 grafts (2.6%). Two cultures grew coagulase-negative Staphylococcus and 1 grew Escherichia coli, both from the broth only. CONCLUSIONS: Positive cultures in ACL allografts have a reported incidence of 5.7% to 13.25%. Our current series shows an incidence of 2.6%. No patients who had a culture-positive allograft developed a clinical infection postoperatively. Routine preimplantation culture of soft tissue allografts cannot be recommended given the low incidence of positive culture and lack of correlation with clinical infection. In the presence of a positive preimplantation allograft culture without signs of clinical infection, our series and the 4 other published series in the literature demonstrate that antibiotic treatment is not indicated. In contrast, signs and symptoms of septic arthritis should be aggressively treated with irrigation, debridement, and intravenous antibiotics.

Fractionation of high-dose electron beam irradiation of BPTB grafts provides significantly improved viscoelastic and structural properties compared to standard gamma irradiation.

PURPOSE: Irradiation >30 kGy is required to achieve sterility against bacterial and viral pathogens in ACL allograft sterilization. However, doses >20 kGy substantially reduce the structural properties of soft-tissue grafts. Fractionation of irradiation doses is a standard procedure in oncology to reduce tissue damage but has not been applied in tissue graft sterilization. METHODS: Forty-four human 10-mm wide bone-patellar-tendon-bone grafts were randomized into four groups of sterilization with (1) 34 kGy of ebeam (2) 34 kGy gamma (3) 34 kGy fractionated ebeam, and (4) non sterilized controls. Graft´s biomechanical properties were evaluated at time zero. Biomechanical properties were analyzed during cyclic and load-to-failure testing. RESULTS: Fractionation of ebeam irradiation resulted in significantly higher failure loads (1,327 ± 305) than with one-time ebeam irradiation (1,024 ± 204; P = 0.008). Compared to gamma irradiation, significantly lower strain (2.9 ± 1.5 vs. 4.6 ± 2.0; P = 0.008) and smaller cyclic elongation response (0.3 ± 0.2 vs. 0.6 ± 0.4; P = 0.05), as well as higher failure loads (1,327 ± 305 vs. 827 ± 209; P = 0.001), were found. Compared to non-irradiated BPTB grafts, no significant differences were found for any of the biomechanical parameters. Non-irradiated controls had significantly lower cyclic elongation response and higher failure loads than ebeam and gamma irradiation. CONCLUSIONS: In this study, it was found that fractionation of high-dose electron beam irradiation facilitated a significant improvement of viscoelastic and structural properties of BPTB grafts compared to ebeam and gamma irradiation alone, while maintaining levels of non-irradiated controls. Therefore, this technique might pose an important alternative to common methods for sterilization of soft-tissue allografts.

Effect of electron beam irradiation on biomechanical properties of patellar tendon allografts in anterior cruciate ligament reconstruction.

BACKGROUND: Sterilization of anterior cruciate ligament (ACL) allografts is an important prerequisite to prevent disease transmission. However, mechanical tissue properties are compromised by most current sterilization procedures, so that uncompromised sterilization of allografts is difficult to achieve. Hypothesis/ PURPOSE: The aim of this study was to evaluate the effect of the novel electron beam sterilization procedure on the biomechanical properties of human patellar tendon allografts at various irradiation dosages. Electron beam sterilization may be an appropriate alternative to gamma sterilization. STUDY DESIGN: Controlled laboratory study. METHODS: Thirty-two human 10-mm wide bone-patellar tendon-bone grafts were randomized into 4 groups of sterilization with 15, 25, or 34 kGy of electron beam irradiation, respectively. The grafts' biomechanical properties were evaluated at time zero. Unsterilized grafts functioned as controls. Biomechanical properties were analyzed during cyclic and load-to-failure testing. RESULTS: Strain and cyclic elongation response showed no significant differences between the groups. Electron beam irradiation had no significant effect on stiffness and failure load with the exception of 34 kGy, which resulted in a significant decrease in failure load (1300.6 +/- 229.2 N) compared with unsterilized grafts (1630.5 +/- 331.1 N). CONCLUSION: This study showed that electron beam might be an appropriate alternative in sterilization of patellar tendon allografts with minimal effect on mechanical properties of tendon grafts in vitro. Future studies will have to evaluate the effect of the process on the biological properties of allografts in vitro and in vivo. CLINICAL RELEVANCE: Terminal sterilization of patellar tendon allografts with electron beam irradiation can ensure higher safety of transplanted grafts and hence improve patient safety and acceptance.

Mycobacterium fortuitum infection after anterior cruciate ligament reconstruction using a polylactic acid bioabsorbable screw: Case report.

We report a case of pretibial sinus and abscess after anterior cruciate ligament reconstruction using a polylactic acid tricalcium phosphate bioabsorbable screw for tibial fixation. Mycobacterium fortuitum was identified as the pathogen after specific mycobacterial cultures were obtained from operative specimens. M. fortuitum is a known but rare cause of periprosthetic infection. Diagnosis is often delayed as routine microbiological cultures do not utilise specific culture requirements for mycobacterial growth. There have been several reports in the literature of sterile abscesses associated with bioabsorbable screws. To our knowledge, this is the first case report of a non-tuberculous mycobacterial infection associated with a bioabsorbable implant. This case illustrates that post-operative Mycobacterium infection can occur as a complication of ACL reconstruction with bioabsorbable screw fixation and should be considered in the differential diagnosis of post-operative periprosthetic infection.

Do anterior cruciate ligament allograft culture results correlate with clinical infections?

PURPOSE: In 1998, four cases of contaminated allografts for anterior cruciate ligament (ACL) reconstruction resulted in Clostridium infection, and a patient with Clostridium infection from a femoral condylar allograft died. It was subsequently published that implanting surgeons should culture ACL allografts so that action could be taken should highly pathogenic bacteria be encountered. The purpose of this study is to test the hypothesis that ACL allograft cultures correlate with clinical infections. METHODS: Since October 2003, a single surgeon performing ACL reconstruction prospectively cultured all allografts in the operating room before implantation. After culture, grafts were thawed in warm saline mixed with bacitracin. All patients received a single dose of preoperative antibiotics. Final culture results were obtained in all patients, and all patients were followed for a minimum of 90 days to evaluate for postoperative infection. The cost of cultures was determined by multiplying hospital charges by the hospital cost-to-charges ratio. RESULTS: Two hundred and ten cases were included. Ten allografts (4.8%) had positive culture results (6 coagulase-negative Staphylococci, 1 alpha-Streptococcus-not-group-B, 1 Enterobacter, 1 Clostridium, and 1 polymicrobial [Klebsiella, Escherichia coli, and Enterococcus]). None of these patients had signs of infection; the three positive highly pathogenic bacteria (Enterobacter, Clostridium, and polymicrobial) graft recipients were treated with antibiotics. The others were observed. One patient with negative cultures developed Staphylococcus aureus infection. Mean culture cost was $127 (USD). CONCLUSIONS: Our results demonstrate that ACL allograft cultures do not correlate with clinical infections. LEVEL OF EVIDENCE: Level I, diagnostic study (testing of previously developed diagnostic criteria [culture]) in a series of consecutive patients (with universally applied reference gold standard [clinical evaluation for knee sepsis]).

Intraoperative anterior cruciate ligament graft contamination.

Intraoperative anterior cruciate ligament graft contamination is a rare but potentially devastating occurrence for any surgeon to encounter. Most instances in our experience have happened when a surgeon first enters practice or is operating in a new environment with new staff. Based on the currently available literature and the senior author's personal experience with 3 cases, intraoperative cleansing of the graft followed by implantation is a reasonable option. The protocol used successfully in these 3 cases includes getting the graft off of the floor immediately, removing any suture material in the graft, cleansing the graft for 15 to 30 minutes each in chlorohexidine and triple antibiotic solution, followed by a normal saline rinse. All graft sutures should then be replaced. The graft should then be resized and the tibial and femoral tunnels adjusted if needed. After implantation of the graft, additional intraoperative and postoperative intravenous antibiotic and/or oral antibiotic administration is also recommended for the first 1 to 2 weeks. Close clinical follow-up is also very important the first 6 weeks postoperatively and should include candid communication with the patient and family.