Propionibacterium acnes and Staphylococcus lugdunensis cause pyogenic osteomyelitis in an intramedullary nail model in rabbits.

Propionibacterium acnes and coagulase-negative staphylococci (CoNS) are opportunistic pathogens implicated in prosthetic joint and fracture fixation device-related infections. The purpose of this study was to determine whether P. acnes and the CoNS species Staphylococcus lugdunensis, isolated from an "aseptically failed" prosthetic hip joint and a united intramedullary nail-fixed tibial fracture, respectively, could cause osteomyelitis in an established implant-related osteomyelitis model in rabbits in the absence of wear debris from the implant material. The histological features of P. acnes infection in the in vivo rabbit model were consistent with localized pyogenic osteomyelitis, and a biofilm was present on all explanted intramedullary (IM) nails. The animals displayed no outward signs of infection, such as swelling, lameness, weight loss, or elevated white blood cell count. In contrast, infection with S. lugdunensis resulted in histological features consistent with both pyogenic osteomyelitis and septic arthritis, and all S. lugdunensis-infected animals displayed weight loss and an elevated white blood cell count despite biofilm detection in only two out of six rabbits. The differences in the histological and bacteriological profiles of the two species in this rabbit model of infection are reflective of their different clinical presentations: low-grade infection in the case of P. acnes and acute infection for S. lugdunensis. These results are especially important in light of the growing recognition of chronic P. acnes biofilm infections in prosthetic joint failure and nonunion of fracture fixations, which may be currently reported as "aseptic" failure.

Burkholderia pseudomallei osteomyelitis of the metatarsal in an infant.

Burkoholderia pseudomallei is an emerging cause of localized musculoskeletal infections. We report the case of a 9-month-old infant with isolated primary chronic osteomyelitis of the fifth metatarsal. Radiographs showed expansion and thickening of the cortex. The metatarsal had lytic lesions with scalloped margins; no periosteal reaction or sequestration was seen. Surgical debridement provided removal of infected material and adequate drainage by saucerization. B. pseudomallei was isolated from purulent material, and histologic examination revealed granulomatous inflammation. The child responded rapidly to a 2-week intravenous course of ceftazidime. The present case highlights the need for an awareness of melioidosis as a new differential diagnosis for a nontuberculous, granulomatous inflammation in those living in or visiting tropical regions.

Intra-operative femoral head vascularity assessment: An innovative and simple technique.

BACKGROUND: Documentation of femoral head blood flow before, during and after head preserving surgery is important for safeguarding vascularity to the femoral head and for documentation in patients in whom the blood flow is compromised. Laser Doppler flowmetry and microsensor intracranial pressure (ICP) transducers have been used to satisfactorily depict such changes. However, these devices are expensive and not universally available in orthopedic operating rooms. We describe a new technique for the assessment of intra-operative blood flow to the femoral head. This is a technical description of a simple system utilized in eight patients to assess the femoral head vascularity using equipment available with the anesthetist. MATERIALS AND METHODS: A standard epidural catheter attached to an arterial pressure transducer is introduced into the femoral head from the margin of the articular surface via a small hole drilled with a K wire. The pressure wave within the epiphysis is detected on the anesthesia monitor. Pressure within the femoral head is used as a surrogate for blood flow. The pressure and the wave form are correlated with the electrocardiogram (ECG) wave on the anesthetic machine. The technique was used in eight children with hip pathology requiring hip dislocation for documenting the hip vascularity status. RESULT: There was good correlation between the pressure wave and the ECG for a patient with presumed normal femoral head vascularity, whereas the pressure measurements were greatly reduced and the wave form was absent in a femoral head wih radiographic or bone scan evidence of avascular necrosis. CONCLUSION: This new technique is a cheap and readily accessible alternative to Laser Doppler flowmetery and ICPs monitoring probes for the assessment of blood flow to the femoral head.