Aims

Fracture-related infection (FRI) is commonly classified based on the time of onset of symptoms. Early infections (< two weeks) are treated with debridement, antibiotics, and implant retention (DAIR). For late infections (> ten weeks), guidelines recommend implant removal due to tolerant biofilms. For delayed infections (two to ten weeks), recommendations are unclear. In this study we compared infection clearance and bone healing in early and delayed FRI treated with DAIR in a rabbit model.

Propionibacterium acnes infection of the shoulder after arthroplasty is a common complication. Current detection methodologies for P. acnes involve prolonged anaerobic cultures that can take up to three weeks before findings can be reported. Our aim was to develop a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) approach that is both sensitive and specific to P. acnes that would enable a 24-hour turnaround between biopsy and results.

Comparisons between the 16S ribosomal sequences of P. acnes and closely related bacteria identified two unique regions in P.acnes to which PCR primers were designed. Additionally, two unique restriction enzyme cut sites for HaeIII were identified within this amplicon. To test the PCR method, arthroscopic surgical biopsies were mechanically homogenised and boiled for 20 minutes to lyse the cellular membranes. PCR was performed using standard conditions followed by a one hour HaeIII enzymatic digest of the PCR product. Resultant fragments were visualised on polyacrylamide gels stained with ethidium bromide. All experiments included no-template controls to rule out reagent contamination and independently confirmed P. acnes DNA as a positive control. Serial dilutions of P. acnes cultures in Robertson's cooked-meat broth and spectrophotometric analysis of cellular concentration were used to assess the sensitivity of the PCR reaction.

A unique 564 base-pair PCR amplicon was derived from different strains of P. acnes. This amplicon was confirmed as P. acnes DNA by gel excision and DNA sequencing. HaeIII digests of the amplicon yielded 3 restriction fragments at the sizes predicted by in silico analyses. Sensitivity testing confirmed that as few as 10 P. acnes cells in a 50µl reaction volume could be detected using this assay. P. acnes was also detected in surgical biopsy samples.

P. acnes infections following shoulder arthroplasty are a serious complication placing a burden on the healthcare system and the patient due to the lengthy surgical revision process that follows. The infections are also difficult to diagnose. This unique assay combines the sensitivity of PCR with the specificity of RFLP mapping to specifically identify P. acnes in surgical isolates. We anticipate that this assay will allow us to determine if a biopsy is P. acnes positive within 24-hours of sampling, allowing for more aggressive antibiotic therapy and monitoring to avoid implant failure and revision surgery. Additionally, this PCR-RFLP method may decrease the false positive rate of extended length cultures due to P. acnes contamination.

Background: There is no consensus on the best treatment of complex intraarticular fractures and high energy diaphyseal fractures of the long bones. The Locking Compression Plate (LCP) and the Less Invasive Stabilization System (LISS) are the new implants with angular stability developed by the AO/ASIF. The new screw-plate systems seem to offer an excellent alternative for the operative fixation in these cases.

Patients and methods: In a prospective study the new system was used to treat 20 patients (8 women, 12 men; average age 39.3 yrs) with 23 high – energy injuries (multifragmentary shaft fractures or complex intraarticular) from december 2001. During a mean period of 20 (13–30) months, complications, clinical and radiographic findings were followed prospectively. One patient was lost to follow-up. 19 patients underwent a standardized follow-up examination. According to the AO classification, 6 were proximal tibial fractures 41-C; 4 distal tibial 43-C; 6 distal femoral 33-C; 3 humerus 12-C and 4 distal radius 23-C. Ten of the fractures were open, 6 grade II, and 4 grade III. Because of severe concomitant injuries, 4 fractures were first treated with an external fixator and definitively stabilized more than two weeks after the injury. 2 patients were operated on after failure of others implants and non-union.

Results: The outcome correlated with the severity of the fracture, anatomic reduction, exact positioning of the plate and concomitant injuries. Despite the large number of open and comminuted fractures no serious complications as deep infections, vascular lesions, DVT or non-unions were presented.

Conclusions: We found the new internal fixator system to be a safe and reliable procedure. The new system offers numerous fixation possibilities and has proven its worth in complex fracture situations and in revision operation. A good knowledge of biomechanics is essential as well as precise preoperative planning.