Causes and consequences of the postfire increase in deer mouse (Peromyscus maniculatus) abundance

Wildfire triggers an increase in deer mouse (Peromyscus maniculatus) abundance. Here, I describe this phenomenon, investigate its causes, and explore the consequences of the postfire increase in mice for conifer recruitment in burned forest. I documented a shift in small mammal communities away from more specialized species such as red-backed voles (Myodes gapperi) and shrews (Sorex spp.) and towards greater abundance of generalist deer mice after a wildfire in montane forest. I conducted a meta-analysis of published studies on the abundance of small mammals in disturbed versus undisturbed forests and established that the pattern of increased deer mouse abundance holds for both natural (wildfire) and anthropogenic (different forms of forest harvest) disturbances. However, the postfire increase is significantly stronger than the increase after logging. In another forest wildfire, I tested the four most commonly proposed explanations of this increase: (1) greater abundance of food resources in burned areas, (2) increased foraging efficiency of deer mice, (3), predatory release, and (4) source - sink dynamics, with burned areas acting as high abundance dispersal sink. However, none were supported by data. Thus, I concluded that the existing explanations of postfire increase in deer mouse abundance are unsatisfactory. Finally, I investigated the magnitude and impact of seed predation by deer mice in burned and unburned forest. In seed offerings experiments, overnight conifer seed removal associated with deer mice was more intense in burned than in unburned stands. In germination experiments, emergence of seedlings in cages with openings that allowed access by deer mice was extremely rare in burned and unburned forest. However, in closed cages (deer mice excluded), seedling emergence was low in unburned forest, but considerably higher in burned forest. Wildfire created favorable conditions for seedling recruitment but seed predation by deer mice appeared to remove this advantage

Extraarticular Knee Resection for Sarcomas with Preservation of the Extensor Mechanism: Surgical Technique and Review of Cases

Background: Sarcomas in or contaminating the knee are rare but extremely challenging to treat. Complete resection of the joint is necessary, and often the entire extensor mechanism is removed as well. Reconstruction of the knee is challenging, and the resulting function may be compromised. Description of technique: We describe a surgical technique of extraarticular resection of the knee while preserving the extensor mechanism combined with prosthetic reconstruction. The medial and lateral retinaculum is prepared such that it allows extraarticular placement of K-wires that are driven through the patella and the proximal tibia, serving as in situ guides for the osteotomies. Patients and Methods: We retrospectively reviewed 11 patients with sarcomas contaminating the knee. The minimum followup was 14months (mean, 38months; range, 14-80months). Results: At last followup patients had a mean flexion of 88° (range, 65°-120°). We observed no complications related to the extensor mechanism, and there was one local recurrence. Conclusions: We believe extraarticular resection of the knee with preservation of the extensor mechanism is a reasonable treatment option for intraarticular sarcomas with functional scores comparable to those for patients having intraarticular resections. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidenc

Extraarticular Knee Resection for Sarcomas with Preservation of the Extensor Mechanism: Surgical Technique and Review of Cases

BACKGROUND: Sarcomas in or contaminating the knee are rare but extremely challenging to treat. Complete resection of the joint is necessary, and often the entire extensor mechanism is removed as well. Reconstruction of the knee is challenging, and the resulting function may be compromised. DESCRIPTION OF TECHNIQUE: We describe a surgical technique of extraarticular resection of the knee while preserving the extensor mechanism combined with prosthetic reconstruction. The medial and lateral retinaculum is prepared such that it allows extraarticular placement of K-wires that are driven through the patella and the proximal tibia, serving as in situ guides for the osteotomies. PATIENTS AND METHODS: We retrospectively reviewed 11 patients with sarcomas contaminating the knee. The minimum followup was 14 months (mean, 38 months; range, 14-80 months). RESULTS: At last followup patients had a mean flexion of 88° (range, 65°-120°). We observed no complications related to the extensor mechanism, and there was one local recurrence. CONCLUSIONS: We believe extraarticular resection of the knee with preservation of the extensor mechanism is a reasonable treatment option for intraarticular sarcomas with functional scores comparable to those for patients having intraarticular resections. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence

Femoral and obturator nerves palsy caused by pelvic cement extrusion after hip arthroplasty.

Cement extrusion into the pelvis with subsequent palsy of the obturator and femoral nerves is a rare entity after hip replacement surgery. Cemented fixation of the acetabular cup has been considered as a safe and reliable standard procedure with very good long term results. We present a case of fifty year old female patient after hip arthroplasty procedure which suffered an obturator and femoral nerve palsy caused by extrusion of bone cement into the pelvis. Postoperative X-rays and CT-scan of the pelvis demonstrated a huge mass consisted of bone cement in close proximity of femoral and obturator nerves. The surgery charts reported shallow and weak bony substance in postero-superior aspect of the acetabulum. This weak bony acetabular substance may have caused extrusion of bone cement during press-fitting of the polyethylene cup into the acetabulum, and the following damage of the both nerves produced by polymerization of bone cement. The bone cement fragment has been surgically removed 3 weeks after arthroplasty. The female patient underwent intensive postoperative physical therapy and electro stimulation which resulted in full recovery of the patient to daily routine and almost normal electromyography results

Local effect of zoledronic acid on new bone formation in posterolateral spinal fusion with demineralized bone matrix in a murine model

BACKGROUND: Posterolateral spinal fusion is a common orthopaedic surgery performed to treat degenerative and traumatic deformities of the spinal column. In posteriolateral spinal fusion, different osteoinductive demineralized bone matrix products have been previously investigated. We evaluated the effect of locally applied zoledronic acid in combination with commercially available demineralized bone matrix putty on new bone formation in posterolateral spinal fusion in a murine in vivo model. METHODS: A posterolateral sacral spine fusion in murine model was used to evaluate the new bone formation. We used the sacral spine fusion model to model the clinical situation in which a bone graft or demineralized bone matrix is applied after dorsal instrumentation of the spine. In our study, group 1 received decortications only (n = 10), group 2 received decortication, and absorbable collagen sponge carrier, group 3 received decortication and absorbable collagen sponge carrier with zoledronic acid in dose 10 µg, group 4 received demineralized bone matrix putty (DBM putty) plus decortication (n = 10), and group 5 received DBM putty, decortication and locally applied zoledronic acid in dose 10 µg. Imaging was performed using MicroCT for new bone formation assessment. Also, murine spines were harvested for histopathological analysis 10 weeks after surgery. RESULTS: The surgery performed through midline posterior approach was reproducible. In group with decortication alone there was no new bone formation. Application of demineralized bone matrix putty alone produced new bone formation which bridged the S1-S4 laminae. Local application of zoledronic acid to demineralized bone matrix putty resulted in significant increase of new bone formation as compared to demineralized bone matrix putty group alone. CONCLUSIONS: A single local application of zoledronic acid with DBM putty during posterolateral fusion in sacral murine spine model increased significantly new bone formation in situ in our model. Therefore, our results justify further investigations to potentially use local application of zoledronic acid in future clinical studies

Risk factors for prolonged treatment and hospital readmission in 280 cases of negative-pressure wound therapy

BACKGROUND There is evidence of certain beneficial effects and increasing understanding of the mechanisms of action of negative-pressure wound therapy (NPWT). However, it is known that prolonged duration of NPWT is associated with increased bacterial growth and efforts should be made to decrease the duration of NPWT. It was the aim of this study to evaluate potential risk factors for the duration, from first application of NPWT to secondary wound closure and to identify factors that increase the rate of hospital readmission. METHODS In a retrospective cohort study, 261 patients (46 ± 19 years, 70 female) who underwent 280 treatments with NPWT were analysed. Patient-specific and demographic characteristics and the presence of several risk factors were documented. The duration of treatment from first application of NPWT to secondary wound closure, the number of interventions, the duration of hospital stay and the incidence of readmissions due to complications of the wound treated by NPWT were recorded and a risk factor analysis was performed. RESULTS The median number of NPWT procedures was 2.0 ± 2.0, the duration of NPWT was 6.0 ± 14.7 days and the length of hospital stay was 16.0 ± 27.9 days. Presence of an open fracture (p = .002) and increased age (p = .004) were identified as independent risk factors for a prolonged duration of NPWT. Patients who smoked (p = .001) or patients with alcohol/drug abuse (p = .015) were more likely to return to hospital (smoking: 18 out of 58 cases; alcohol/drug abuse: 7 out of 19 cases). No such association was seen for diabetes (p = .702), peripheral vascular disease (PVD) (p = .052), immunosuppressive medication (p = .187), immunodeficiency (p = .404), trauma (p = .358), infection (p = .298) and open fracture (p = .061). CONCLUSIONS Patient age and presence of an open fracture are independent predictors of a prolonged duration from first application of NPWT to secondary wound closure. These results should be taken into account for the calculation of average costs and anticipated hospital stay associated with this therapy

Therapy of acute and delayed spinal infections after spinal surgery treated with negative pressure wound therapy in adult patients

We present the results of the treatment of infected primary or delayed spine wounds after spinal surgery using negative pressure wound therapy. In our institution (University Hospital Zurich, Switzerland) nine patients (three women and six men; mean age 68.6, range 43- 87 years) were treated in the period between January to December 2011 for non-healing spinal wounds. The treatment consisted of repeated debridements, irrigation and temporary closure with negative pressure wound therapy system. Three patients were admitted with a spinal epidural abscess; two with osteoporotic lumbar fracture; two with pathologic vertebra fracture and spinal cord compression, and two with vertebra fracture after trauma. All nine patients have been treated with antibiotic therapy. In one case the hardware has been removed, in three patients laminectomy was performed without instrumentation, in five patients there was no need to remove the hardware. The average hospital stay was 16.6 days (range 11-30). The average follow-up was 3.8, range 0.5-14 months. The average number of negative pressure wound therapy procedures was three, with the range 1-11. Our retrospective study focuses on the clinical problems faced by the spinal surgeon, clinical outcomes after spinal surgery followed by wound infection, and negative pressure wound therapy. Moreover, we would like to emphasize the importance for the patients and their relatives to be fully informed about the increased complications of surgery and about the limitations of treatment of these wounds with negative pressure wound therapy

Bacterial reduction and shift with NPWT after surgical debridements: a retrospective cohort study

BACKGROUND Surgical debridement, negative-pressure wound therapy (NPWT) and antibiotics are used for the treatment of open wounds. However, it remains unclear whether this treatment regimen is successful in the reduction and shift of the bacterial load. METHODS After debridement in the operating room, NPWT, and antibiotic treatment, primary and secondary consecutive microbiological samples of 115 patients with 120 open wounds with bacterial or yeast growth in ≥1 swab or tissue microbiological sample(s) were compared for bacterial growth, Gram staining and oxygen use at a level one trauma center in 2011. RESULTS Secondary samples had significantly less bacterial growth (32 vs. 89%, p < .001, OR 17), Gram-positive bacteria (56 vs. 78%, p = .013), facultative anaerobic bacteria (64 vs. 85%, p = .011) and Staphylococcus aureus (10 vs. 46%, p = .002). They also tended to include relatively more Coagulase-negative Staphylococci (CoNS) (44 vs. 18%) and Pseudomonas species (spp.) (31 vs. 7%). Most (98%) wounds were successfully closed within 11 days, while wound revision was needed in 4%. CONCLUSIONS The treatment regimen of combined use of repetitive debridement, irrigation and NPWT in an operating room with antibiotics significantly reduced the bacterial load and led to a shift away from Gram-positive bacteria, facultative anaerobic bacteria, and S. aureus, as well as questionably toward CoNS and Pseudomonas spp. in this patient cohort. High rates of wound closure were achieved in a relatively short time with low revision rates. Whether each modality played a role for these findings remains unknown