Flaps for closure of soft tissue defects in infected revision knee arthroplasty.

PURPOSE: Total knee arthroplasty revision has wound healing deficits of up to 20 %. Defects in the knee region of multimorbid patients are hard to treat as complete explantation and revision arthroplasty is often too burdensome for them. In this study, we present our results with flaps for the treatment of defects after knee replacement, arthrodesis or osteosynthesis. METHODS: Twenty-five patients (26 knees) with defects in the knee region were treated with flaps. Mean follow-up was 37 months (13-61) and the patients had a mean age of 72 years (49-85). A total of 39 flaps were performed (27 muscle flaps, seven fascio-cutaneous flaps and five free flaps). RESULTS: Patients with more than three comorbidities showed higher risk of complications after surgery. Fifteen patients showed no infection at last follow up. Five patients received an arthrodesis of the knee, two showed persistent infection of the implant with fistula, and three were amputated above the knee. CONCLUSIONS: Amputation could be avoided in 22 cases (85 %). The gastrocnemius muscle flap showed good results in the treatment of defects after arthroplasty or arthrodesis of the knee in multimorbid patients. This procedure can be used if further revision surgery is not indicated.

Posttraumatic and postoperative osteomyelitis: surgical revision strategy with persisting fistula.

INTRODUCTION: Posttraumatic and postoperative osteomyelitis (PPO) with bacteria colonisation during trauma and associated surgery is an increasing clinical problem. This study investigated the treatment of PPO by surgical revision including irrigation, debridement, and temporary hardware maintenance. In addition, a drainage was inserted as persisting fistula to control osteomyelitis until fracture healing was achieved. Trauma- and osteomyelitis-related factors that influenced the study outcome were determined. PATIENTS AND METHODS: 67 consecutive patients with PPO were included. At onset of PPO, patients had incomplete fracture healing. Patients were subdivided by time of PPO occurrence (acute, subacute or chronic), initial soft tissue trauma, anatomical location, and initial fracture type (AO classification). The study outcome measures included radiographic and clinical follow-up. RESULTS: 59 patients could be followed for an average of 23 months after revision surgery. A bone healing was achieved by 89% of patients after 14.7 ± 13.4 weeks. Fractures of the lower extremity, open fractures and comminuted C-type fractures took significantly longer to achieve bone healing (p < 0.05 each). Time of PPO occurrence did not influence bone healing. After fracture consolidation, no re-infection was found. CONCLUSIONS: This study showed high rates of bone healing, indicating that this strategy with persisting fistula should be considered as alternative treatment option in patients with PPO.

Human polymorphonuclear neutrophils express RANK and are activated by its ligand, RANKL.

The receptor activator of NF-κB (RANK) is especially well studied in the context of bone remodeling, and RANK and its ligand, RANKL, are key molecules in the induction of bone resorbing osteoclasts. We now report that polymorphonuclear neutrophils (PMNs) contain preformed RANK, stored in secretory vesicles and in specific granules. Upon stimulation of PMNs in vitro, RANK was translocated to the cell membrane. In patients with persistent bacterial infections, RANK surface expression was enhanced compared with that of healthy individuals. The functional activity of RANK was assessed by determining migration of PMNs toward RANKL. A time- and dose-dependent migration was seen, leading to the conclusion that RANK on PMNs is functional. We presume that regulated RANK expression contributes to the fine tuning of PMN migration, for example, on and through inflamed endothelium that is known to express RANKL.

Osteomyelitis.

INTRODUCTION: Osteomyelitis is a challenging diagnosis for every patient because of its protracted treatment process. Very experienced orthopaedic surgeons are needed to diagnose and treat this bacteria-related severe disorder in a right and proper way. MATERIALS AND METHODS: Different treatment options are possible for osteomyelitis at any stage: antibiotics in the acute and chronic stage for conservative treatment or radical debridement, bone fenestration, reaming, bone troughing, the Masquelet-technique, segmental resection with callus distraction, bone grafting and even amputation as surgical therapy. RESULTS: Depending on different stages of the disease, there are good results with every technique available-on condition that radical debridement was performed. The complication rate is remarkable so that soft tissue defects should be assessed by using flaps to close the wounds in early stages. CONCLUSIONS: The treatment of osteomyelitis should be done in centres with expertise in the treatment of this challenging disease. Different methods should be offered by surgeons and individual treatment concepts acquired together with the patient. The treatment of complications like soft tissue defects should be provided in the same centre and performed in short time lag to the prior surgery. The cooperation of the patient and surgeons of different specialities is mandatory in these cases.

Intraoperative subcutaneous wound closing culture sample: a predicting factor for periprosthetic infection after hip- and knee-replacement?

INTRODUCTION: It is unknown whether intraoperative subcutaneous wound closing culture samples (WCCS) are useful to predict periprosthetic joint infection (PJI). METHOD: Here we prospectively followed 167 out of a total of 175 consecutive patients with primary total hip (THR) or knee replacement (TKR) between 01/2002 and 12/2002 for a mean follow-up period of 5 years; of those patients, n = 159 (96.8%) underwent WCCS. RESULTS: The results showed a positive WCCS in n = 9 cases (5.8%). Nine patients developed postoperative wound complication and required revision surgery. Two patients developed signs of a deep periprosthetic infection; however, only one out of nine patients had initial positive WCCS. CONCLUSION: Our results thus indicate that WCCS during primary joint replacement is not an appropriate predictive method to identify patients at risk for periprosthetic joint infections.

Vascularised and modified lower-leg rotationplasty for the treatment of severe infection and bone loss of the proximal femur: a case report.

CASE DESCRIPTION: We report a reconstructive case in a paraplegic patient, who suffers from a severe proximal femur infection. Aiming at the preservation of the capacity to remain in a seated position to operate a wheelchair, lower leg rotationplasty was considered suitable for reconstruction. Due to severe infection and subclinical femoral artery stenosis, rotationplasty was supercharged by the inferior epigastric artery. Furthermore, extensor tendons of the foot were attached to the acetabulum to facilitate stability of the neo-hip joint. RESULTS: Follow-up examination 1 year after surgery revealed no complications and a satisfied patient. CONCLUSIONS: Especially in paraplegic patients, lower leg rotationplasty is a possible treatment option for severe femoral infection. Supercharging provides well-vascularised tissue to the former infection site and improves wound healing.

T lymphocytes in implant-associated posttraumatic osteomyelitis: Identification of cytotoxic T effector cells at the site of infection.

In implant-associated posttraumatic osteomyelitis, a massive infiltration of leukocytes into the infected site is seen. As described previously, the most infiltrated cells were highly activated polymorphonuclear neutrophils. In addition, a considerable T-cell infiltrate was noted. Whereas our previous work was mainly concerned with the phenotypical and functional characterization of the polymorphonuclear neutrophils, we now analyzed T lymphocytes of 32 patients with implant-associated posttraumatic osteomyelitis. We found evidence for an expansion of CD8 T cells in the peripheral blood of the patients and for an infiltration of these cells into the infected site. Further analysis of the surface-receptor pattern by three-color cytofluorometry revealed that the majority of these cells belonged to the cytotoxic-effector phenotype. Of note is that cytotoxic T cells are generally associated with virus infection. Thus, the detection of those cells in patients with bacterial infection was rather unexpected and points to a novel, not yet appreciated, role of CD8 T cells also in the defense of bacterial infections.

Expression of elastase on polymorphonuclear neutrophils in vitro and in vivo: identification of CD11b as ligand for the surface-bound elastase.

Elastase is a major serine protease of polymorphonuclear neutrophils (PMN). On activation of PMN, the preformed protein is mobilized from intracellular stores and, depending on the activating conditions, is either released into the supernatant or is bound to the cell surface. By a variety of methods, including uptake and crosslink studies, as well as confocal laser scan microscopy, we now provide evidence that elastase binds to the beta(2)-integrin CD11b and induces a conformational alteration of CD11b, apparent as expression of a neodeterminant. Similarly to the in vitro data, elastase surface expression and conformational alterations of CD11b were seen on PMN of patients with Staphylococcus aureus-induced localized infection, particularly on PMNs recovered from the infected site. The presence of elastase at the site of inflammation is in keeping with its presumed role in leukocyte trafficking and host defense. On the other hand, because of its potential for degrading extracellular matrix proteins, elastase could participate in localized tissue damage as it occurs in severe S. aureus infection.

Post-traumatic osteomyelitis: analysis of inflammatory cells recruited into the site of infection.

Device-associated infections after implants or endoprostheses inflict local inflammation and ultimately osteolysis, a clinical entity referred to as posttraumatic osteomyelitis. The underlying molecular mechanisms are not yet known; formation of bacterial biofilms on the implant is presumed, conferring resistance to antibiotics and to host defense mechanisms as well. To gain insight into the pathogenesis of post-traumatic osteomyelitis, the infected site was analyzed for the presence of immunocompetent cells. In 18 patients, the infected site was rinsed intraoperatively. This so-called lavage contained 1-2 x 107 leukocytes, predominantly highly activated polymorphonuclear neutrophils (PMNs), as characterized by low expression of CD62L (selectin), and high expression of the adhesion protein CD18, of the high-affinity immunoglobulin (IgG) receptor CD64, and of the LPS-receptor CD14. CD16, the low-affinity IgG receptor, was affected in some patients only. Because the majority of infections were caused by staphylococci species, the effect of bacteria-derived lipoteichoic acid on PMN of healthy donors was tested in vitro. A similar activation pattern was found: rapid down-regulation of CD62L, a slower loss of CD16, and upregulation of CD18, CD64, and CD14. Lipoteichoic acid signaling required p38 mitogen-activated protein kinase and resulted in induction of CD14-specific mRNA and de novo protein synthesis. We conclude that PMNs infiltrate the infected site, but despite local activation they are unable to clear the bacteria, presumably because of biofilm formation. Our data are consistent with the hypothesis that during the ineffective "frustrated" attempt to phagocytose, PMNs release cytotoxic and proteolytic entities that in turn contribute to the progression of tissue injury and ultimately to osteolysis.

Polymorphonuclear neutrophils in posttraumatic osteomyelitis: cells recovered from the inflamed site lack chemotactic activity but generate superoxides.

The pathogenesis of posttraumatic osteomyelitis, one of the major complications after orthopedic surgery, is not yet understood. Formation of bacterial biofilms on the implant is presumed, conferring resistance to antibiotic therapy and probably also to the host defense mechanisms. In that context, the polymorphonuclear neutrophils (PMN) having infiltrated the infected site were recovered and characterized phenotypically and functionally. Loss of CD62L and upregulation of CD14 were seen, as was expression of CD83. Expression of the latter is dependent on de novo protein synthesis and thus is indicative of an extended life span and a transdifferentiation of the PMN at the infected site. The infiltrated PMN had lost their chemotactic activity, whereas the capacity to produce superoxides was preserved and in some patients even enhanced. In vitro experiments done in parallel showed that long-term culture with interferon-gamma resulted in similar alterations of PMN: loss of chemotactic activity, whereas other functions of PMN, such generation of superoxides and phagocytosis of opsonized bacteria, were preserved or even enhanced. The loss of the migratory capacity of PMN having already emigrated from the blood vessel to the infected site is not expected to affect the host defense negatively. Assuming, however, that bacteria are organized as a biofilm and that infiltration into this biofilm is required for phagocytosis of the bacteria, our data could to some extent explain why despite being activated, the PMN are not able to control the infection. By releasing their cytotoxic, proteolytic, and collagenolytic potential, PMN might instead contribute to tissue destruction and eventually to osteolysis.

Activation of T Lymphocytes in Response to Persistent Bacterial Infection: Induction of CD11b and of Toll-Like Receptors on T Cells.

T cell activation is invariably associated with virus infections, but activation of T cells is also noted, for example, in patients with persistent bacterial infections with intracellular pathogens or localised bacterial biofilms. The latter is characterised by a destructive inflammatory process. Massive infiltration of leukocytes, predominantly of polymorphonuclear neutrophils (PMNs) and of T lymphocytes, is seen. While PMN influx into sites of bacterial infection is in line with their role as "first-line defence" a role of T cells in bacterial infection has not yet been delineated. We now found evidence for activation and expansion of peripheral blood T cells and an upregulation of Toll-like receptors 1, 2, and 4 on small portions of T cells. T cells recovered from the infected site were terminally differentiated and produced interferon gamma, a cytokine known to enhance functions of phagocytic cells, leading to the conclusion that infiltrated T cells support the local immuner defence.