Data of optimal management of infections after internal fixation (IIF) is scarce and long-term follow-up results often lack. We analyzed characteristics of infections after intramedullary (IIIF) and extramedullary long bone fixation (IEIF) and evaluated their infection and functional outcome. Consecutive patients with IIF diagnosed at our institution from 01/2010-10/2017 were retrospectively included. Infection was defined as visible purulence, sinus tract, microbial growth in ≥2 independent samples or positive histopathology. The outcome was compared before and after implementation of a comprehensive surgical and antimicrobial treatment algorithm in 04/2013.Aim
Method
To assess the analytical performance and to establish the cut-off of synovial fluid D-lactate concentration for the diagnosis of prosthetic joint infection (PJI) and septic arthritis (SA) using commercial kits provided by two manufacturers (A and B). We prospectively included patients with native or prosthetic joints undergoing synovial fluid aspiration as routine diagnostic procedure. Among 224 patients with prosthetic joints, 137 patients had aseptic loosening (AL) and 87 were diagnosed with PJI. Among 71 patients with native joints, 39 were diagnosed with osteoarthrosis (OA) and 32 with SA.Aim
Method
The incidence of hematogenous periprosthetic joint infections (hPJI) is unknown and the cases probably largely underreported. Unrecognized and untreated primary infectious foci may cause continuous bacteremia, further spread of microorganisms and thus treatment failure or relapse of infection. This study aimed at improving knowledge about primary foci and microbiological characteristics of this entity to establish preventive measures and improve diagnostic and therapeutic strategies to counteract hPJI. We retrospectively analysed all consecutive patients with hPJI, who were treated at our institution from January 2010 until December 2016. Diagnosis of PJI was established if 1 of the following criteria applied:(i) macroscopic purulence, (ii) presence of sinus tract, (iii) positive cytology of joint aspirate (>2000 leukocytes/μl or >70% granulocytes), (iv) significant microbial growth in synovial fluid, periprosthetic tissue or sonication culture of retrieved prosthesis components, (v) positive histopathology. PJI was classified as hematogenous if the following criteria were fulfilled additionally: (1) onset of symptoms more than 1 month after arthroplasty AND (2) i) isolation of the same organism in blood cultures OR ii) evidence of a distant infectious focus consistent with the pathogen.Aim
Method
Bilateral mandibular lengthening is widely accepted during mandibular distraction osteogenesis. However, distraction osteogenesis are sometimes associated with clinical complications such as open bite deformity, lateral displacement of temporo-mandibular joint, premature consolidation and pin loosening. Although distraction osteogenesis aims to develop pure tensile strain on the regenerate tissue however, in real life situation due to differences in device orientation, materials and misalignment it is often subjected to complex stress and strain regimes. The objective of this study was to characterise the mechanical environment (stress and strain) in the Finite Element Models (FEM) of regenerate tissue during two different device orientations:
(a) device placed parallel to the mandibular body (b) device placed parallel to the axis of distraction. Furthermore, the influence of misalignment from above two idealised orientations was also investigated. The distraction protocol in this study was similar to previous study of Loboa et al (2005). FE models were developed at four stages: end of latency, distraction day two, distraction day five and distraction day eight. At each time period a distraction of 1mm was applied to the model as it is most widely used distraction rate. In these models two primary distraction vectors were simulated; first when the device is parallel to the body of the mandible and second when the device is parallel to the axis of distraction. Results indicate that when the device is placed parallel to the mandible the effect of distraction vector variation due to misalignment in transverse plane (±150 at an interval of 50 ; + indicate lateral and indicates medial) is symmetric and variation in the stress and strain regimes on regenerative tissue are less than 3%. However, when the device is placed parallel to axis of distraction the corresponding change is asymmetric and almost double in magnitude. The greatest differences were seen when misalignment is towards lateral side (+150). Similarly in the sagittal plane variations up to 17% were developed due to 0- 400 change in the distraction vector orientation. Thus the orientation of device which determines the distraction vector plays an important role in determining the mechanical environment around regenerative tissue. The results suggest that implications of misalignment of the device and its sensitivity from the ideal situation should be well understood during clinical planning.
Bone fluid flow transports nutrients to, and carries waste from, the bone cells embedded in the bony matrix. In long bones, it is driven by the blood pressure differentials between the medullary cavity and the periosteal surface and it is enhanced by mechanical loading. Loading of bone tissue deforms the bone matrix and changes the volume of the medullary cavity. Both mechanisms alter the interstitial fluid flow in the bone cortex. The former changes the volume of the fluid cavities in the cortex, while the latter modifies the intramedullary pressure (IMP). This study aims to investigate and compare, for the first time, the effects of these two mechanisms combined on the interstitial fluid flow in the bone cortex. A hydraulic-fluid method is proposed to investigate the enhancement of IMP induced by the external loading. An intact sheep tibia is represented by a hollow cylinder, with the bone marrow being completely constrained in the cavity and assumed to behave as an icompressible liquid. The cortex is supposed to be a purely elastic material, and its permeability is ignored at this stage. The numerical results show that an axial compressive load of 500 N increases the IMP from 4000 Pa to 48900 Pa. The influence of the enhanced IMP on the interstitial fluid flow is examined in a subsequent poroelastic analysis. At this stage, the cortex is assumed to be a biphasic material that permits fluid perfusion. The poroelastic analyses were conducted for both initial and enhanced IMPs. The results of the simulations demonstrate that the external load induces very high interstitial pressure. The highest pressure could be 25 times higher than the initial marrow pressure, but its magnitude decreases quickly. Furthermore, the influence of the IMP on the interstitial pressure is limited to the inner half of the cortical wall adjacent to the endosteal surface. However, the influence becomes more significant with decreasing load-induced interstitial pressure. In conclusion, these simulations suggest that the increase in IMP during mechanical loading further enhances interstitial fluid movements in cortical bone, which highlights the importance of mechanical loading for the maintenance of healthy bones.
