Microsurgical Lower Extremity Reconstruction in the Subacute Period: A Safe Alternative.

BACKGROUND: Microsurgical reconstruction of the lower extremity is an integral part of the limb salvage algorithm. Success is defined by a pain-free functional extremity, with a healed fracture and sufficient durable soft tissue coverage. Although early flap coverage of lower extremity fractures is an important goal, it is not always feasible because of multiple factors. Between the years 2000 and 2010, approximately 50% of patients at Los Angeles County and University of Southern California Medical Center requiring microsurgical reconstruction did not receive soft tissue coverage until more than 15 days postinjury secondary to primary trauma, physiologic instability, patient comorbidities, or orthopedic and plastic surgery operative backlog. The objective of our study was to evaluate outcomes in patients who underwent microsurgical reconstruction of the lower extremity, in relation to the timing of reconstruction. METHODS: A retrospective chart review was performed for patients requiring immediate lower extremity reconstruction from January 2000 to December 2009 at LAC + USC. RESULTS: Fifty-one patients were identified in this study. The most common mechanisms of injury were motorcycle, motor vehicle, and fall accidents. Eighty-six percent of injuries were open and 74% were comminuted. The distal 1/3 of the tibia, including the tibial pilon, was the most common location of injury. When comparing patients reconstructed in less than 15 days versus greater than or equal to 15 days, there was no significant difference in rates of flap failure, osteomyelitis, bony union, or ambulation. CONCLUSION: Microsurgical reconstruction of the lower extremity in the subacute period is a safe alternative.

Study of nanostructural organization of ionic liquids by electron paramagnetic resonance spectroscopy.

The X-band electron paramagnetic resonance spectroscopy (EPR) of a stable, spherical nitroxide spin probe, perdeuterated 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (pDTO) has been used to study the nanostructural organization of a series of 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids (ILs) with alkyl chain lengths from two to eight carbons. By employing nonlinear least-squares fitting of the EPR spectra, we have obtained values of the rotational correlation time and hyperfine coupling splitting of pDTO to high precision. The rotational correlation time of pDTO in ILs and squalane, a viscous alkane, can be fit very well to a power law functionality with a singular temperature, which often describes a number of physical quantities measured in supercooled liquids. The viscosity of the ILs and squalane, taken from the literature, can also be fit to the same power law expression, which means that the rotational correlation times and the ionic liquid viscosities have similar functional dependence on temperature. The apparent activation energy of both the rotational correlation time of pDTO and the viscous flow of ILs and squalane increases with decreasing temperature; in other words, they exhibit strong non-Arrhenius behavior. The rotational correlation time of pDTO as a function of η/T, where η is the shear viscosity and T is the temperature, is well described by the Stokes-Einstein-Debye (SED) law, while the hydrodynamic probe radii are solvent dependent and are smaller than the geometric radius of the probe. The temperature dependence of hyperfine coupling splitting is the same in all four ionic liquids. The value of the hyperfine coupling splitting starts decreasing with increasing alkyl chain length in the ionic liquids in which the number of carbons in the alkyl chain is greater than four. This decrease together with the decrease in the hydrodynamic radius of the probe indicates a possible existence of nonpolar nanodomains.

Analysis of risk factors associated with microvascular free flap failure using a multi-institutional database.

BACKGROUND: There are numerous factors that may contribute to microvascular free flap failure. Although technical issues are dominant factors, patient and clinical characteristics are also contributory. The aim of this study was to investigate non-technical variables associated with microsurgical free flap failure using a multi-institutional dataset. METHODS: Utilizing the American College of Surgeons' National Surgical Quality Improvement Program (NSQIP) database, we identified all patients who underwent microvascular free tissue transfer from 2005 through 2009. Univariate analysis was performed to determine the association of flap failure with the following factors: age, gender, ethnicity, body mass index, intraoperative transfusion, diabetes, smoking, alcohol, American Society of Anesthesiologists classification, year of operation, operative time, number of flaps, and type of reconstruction. Factors with a significance of P < 0.2 in the univariate analysis were included in the multivariate logistic regression model to identify independent risk factors. RESULTS: A total of 639 patients underwent microsurgical free flap reconstruction with 778 flaps over the 4-year study period; 139 patients had two free flaps during the same operation. The overall incidence of flap failure was 4.4% (34/778) (95% confidence interval [CI]: 3.0%, 6.2%). Operative time was identified as an independent risk factor for free flap failure. After adjusting for other factors, those whose operative time was equal to or greater than the 75th percentile (625.5 min) were twice as likely to experience flap failure (AOR 2.09; 95% CI: 1.01-4.31; P = 0.045). None of the other risk factors studied were significant contributors. CONCLUSIONS: In this series, the overall flap loss rate of was 4.4%. Operative time was a significant independent risk factor for flap failure.

Breast reconstruction satisfaction rates at a large county hospital.

BACKGROUND: It has been previously reported that the indigent patient population is less likely to seek breast reconstruction. It has also been reported that lower income women who do chose to undergo reconstruction are less satisfied with the results. This study assesses the level of breast reconstruction satisfaction in women treated at Los Angeles County Medical Center (LAC). For those women with lower satisfaction, we seek to identify the root source of this dissatisfaction. METHODS: Patients who underwent breast reconstruction at LAC from 2007 to 2012 were identified by Current Procedural Terminology codes. Eligible participants were administered the BREAST-Q postreconstruction module. Demographic data were obtained from the patient and/or their medical records. RESULTS: A total of 65 patients completed the surveys. The satisfaction scores for the appearance of the breast were 61 (24) and satisfaction with overall outcome was 80 (26). The occurrence of major complications was associated with lower satisfaction scores with respect to the appearance of the breast (P<0.0001) and overall outcome (P=0.02). In addition, patients with delayed reconstruction were also noted to be more satisfied with respect to appearance of the breast (P=0.03). CONCLUSIONS: Despite suggestions that the indigent and the underserved patient population are less satisfied with the results of their breast reconstruction procedures, patients at LAC demonstrated comparable satisfaction levels to other published reports. The occurrence of major complications and immediate reconstruction were significantly associated with lower levels of satisfaction.

Urinary bladder matrix for the treatment of recalcitrant nonhealing radiation wounds.

Chronic wounds in previously radiated tissue are challenging to treat. In this article, the authors describe 3 such wounds that failed to heal despite multiple treatments with traditional wound healing methods. Treatment with porcine urinary bladder matrix, an extracellular matrix material, was initiated to facilitate epithelialization and promote wound healing. MatriStem powder (ACell, Inc, Columbia, Maryland), MatriStem (ACell, Inc) sheet, and DuoDerm (ConvaTec, Skillman, New Jersey) were applied biweekly and resulted in complete wound closure within 3 weeks of initial application for all 3 cases. All wounds remained closed 9 months following treatment, suggesting a role for urinary bladder matrix in the management of chronic wounds in the setting of irradiated tissue.

Incidence of surgical-site infection is not affected by method of immediate breast reconstruction.

BACKGROUND: To date, few large-scale studies have reported the incidence of surgical-site infection in women undergoing mastectomy with respect to the various methods of immediate breast reconstruction. This study assessed whether the reconstruction method was associated with the risk of surgical-site infection in these patients. METHODS: Using the National Surgical Quality Improvement Program database, 9230 female patients undergoing mastectomy with immediate reconstruction from 2005 to 2009 were identified. Reconstruction was classified as autologous, prosthetic, or hybrid. The primary outcome was the incidence of surgical-site infection within 30 days of operation. Univariate and multivariate analyses were performed to derive the unadjusted and adjusted risk of surgical-site infection according to reconstruction method. RESULTS: The overall rate of surgical-site infection was 3.53 percent (95 percent CI, 3.15 to 3.94 percent), with individual rates of 3.33 percent (95 percent CI, 2.93 to 3.76 percent) for prosthetic reconstruction, 4.88 percent (95 percent CI, 3.48 to 6.11 percent) for autologous reconstruction, and 2.19 percent (95 percent CI, 0.88 to 4.45 percent) for hybrid reconstruction. The adjusted odds ratio of surgical-site infection was 1.14 (95 percent CI, 0.83 to 1.58; p = 0.42) for autologous versus prosthetic methods and 0.59 (95 percent CI, 0.27 to 1.27; p = 0.18) for hybrid versus prosthetic methods. CONCLUSIONS: Although the risk of surgical-site infection in patients undergoing immediate reconstruction is highest with autologous and lowest with hybrid methods of reconstruction, the difference in infection risk was not statistically significant after adjustment for confounding factors. Thus, all methods of reconstruction are viable options with regard to risk for surgical-site infection. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.

Identifying risk factors for surgical site infections in mastectomy patients using the National Surgical Quality Improvement Program database.

BACKGROUND: The Centers for Disease Control and Prevention reported that surgical site infections (SSIs) create a significant hospital burden. To date, few multi-institutional studies have been performed to evaluate the risk factors for SSIs in mastectomy patients. METHODS: By using the American College of Surgeons' National Surgical Quality Improvement Program database, all patients undergoing mastectomy from 2005 to 2009 were identified. The outcome was to determine the incidence rate and identify significant independent risk factors of SSIs. RESULTS: The incidence of SSI was 2.3% (891 of 38,739; 95% confidence interval, 2.2%-2.5%) in patients undergoing mastectomy without reconstruction. Significant (P < .05) risk factors for SSI included a body mass index greater than 25, American Society of Anesthesiology classification of 3 or higher, diabetes mellitus, surgical time of 2 hours or longer (75th percentile), and current smoking status. CONCLUSIONS: Before this study, there was wide variation in the incidence rate of surgical site infections in this patient population. This was a large-scale study to address these inconsistencies.

The variation in the absence of the palmaris longus in a multiethnic population of the United States: an epidemiological study.

The absence of the palmaris longus (PL) has been shown to vary based on body side, gender, and ethnicity. In prior studies, homogenous ethnic populations have been shown to have differences in rates of absence. However, no study thus far has analyzed the differences in palmaris longus prevalence in a multiethnic population. We prospectively collected data on 516 patients visiting the outpatient hand clinics at LAC+USC Medical Center and Keck Medical Center. Analysis of the data was then performed for variables including ethnicity, laterality, and gender. There were no differences in the absence of the PL based on laterality or gender. Ethnically, there was no difference between white (non-Hispanic) and white (Hispanic) patients, with prevalence of 14.9% and 13.1%, respectively. However, African American (4.5%) and Asian (2.9%) patients had significantly fewer absences of the PL than the Caucasian, Hispanic reference group (P = 0.005 and P = 0.008, resp.). African Americans and Asians have a decreased prevalence of an absent PL. The Caucasian population has a relatively greater prevalence of an absence of the PL. This epidemiological study demonstrates the anatomic variation in this tendon and may be taken into account when planning an operation using tendon grafts.

Effect of immediate reconstruction on postmastectomy surgical site infection.

INTRODUCTION: Surgical site infections (SSI) are a source of significant postoperative morbidity and cost. Although immediate breast reconstruction after mastectomy has become routine, the data regarding the incidence of SSI in immediate breast reconstruction is highly variable and series dependent. METHODS: Using the National Surgical Quality Improvement Program database, all female patients undergoing mastectomy, with or without immediate reconstruction, from 2005 to 2009 were identified. Only "clean" procedures were included. The primary outcome was incidence of SSI within 30 days of operation. Stepwise logistic regression analysis was used to identify risk factors associated with SSI. RESULTS: A total of 48,393 mastectomies were performed during the study period, of which 9315 (19.2%) had immediate breast reconstruction. The incidence of SSI was 3.5% (330/9315) (95% CI [confidence interval]: 3.2%-4%) in patients undergoing mastectomy with reconstruction and 2.5% (966/39,078) (95% CI: 2.3%-2.6%) in patients undergoing mastectomy without reconstruction (P < 0.001). Independent risk factors for SSI include increased preoperative body mass index (BMI), heavy alcohol use, ASA (American Society of Anesthesiologists) score greater than 2, flap failure, and operative time of 6 hours or longer. CONCLUSIONS: Immediate breast reconstruction is associated with a statistically significant increase in risk of SSI in patients undergoing mastectomy (3.5% vs 2.5%). However, this difference was not considered to be clinically significant. In this large series, increased BMI, alcohol use, ASA class greater than 2, flap failure, and prolonged operative time were associated with increased risk of SSI.

Electron paramagnetic resonance line shifts and line shape changes due to heisenberg spin exchange and dipole-dipole interactions of nitroxide free radicals in liquids 8. Further experimental and theoretical efforts to separate the effects of the two interactions.

The work in part 6 of this series (J. Phys. Chem. A 2009, 113, 4930), addressing the task of separating the effects of Heisenberg spin exchange (HSE) and dipole-dipole interactions (DD) on electron paramagnetic resonance (EPR) spectra of nitroxide spin probes in solution, is extended experimentally and theoretically. Comprehensive measurements of perdeuterated 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (pDT) in squalane, a viscous alkane, paying special attention to lower temperatures and lower concentrations, were carried out in an attempt to focus on DD, the lesser understood of the two interactions. Theoretically, the analysis has been extended to include the recent comprehensive treatment by Salikhov (Appl. Magn. Reson. 2010, 38, 237). In dilute solutions, both interactions (1) introduce a dispersion component, (2) broaden the lines, and (3) shift the lines. DD introduces a dispersion component proportional to the concentration and of opposite sign to that of HSE. Equations relating the EPR spectral parameters to the rate constants due to HSE and DD have been derived. By employing nonlinear least-squares fitting of theoretical spectra to a simple analytical function and the proposed equations, the contributions of the two interactions to items 1-3 may be quantified and compared with the same parameters obtained by fitting experimental spectra. This comparison supports the theory in its broad predictions; however, at low temperatures, the DD contribution to the experimental dispersion amplitude does not increase linearly with concentration. We are unable to deduce whether this discrepancy is due to inadequate analysis of the experimental data or an incomplete theory. A new key aspect of the more comprehensive theory is that there is enough information in the experimental spectra to find items 1-3 due to both interactions; however, in principle, appeal must be made to a model of molecular diffusion to separate the two. The permanent diffusion model is used to illustrate the separation in this work. In practice, because the effects of DD are dominated by HSE, negligible error is incurred by using the model-independent extreme DD limit of the spectral density functions, which means that DD and HSE may be separated without appealing to a particular model.

Experimental method to measure the effect of charge on bimolecular collision rates in electrolyte solutions.

A stable, monoprotic nitroxide spin probe is utilized as a model to study molecular collisions in aqueous electrolyte solutions. The rate constants of bimolecular collisions, K(col) for 2,2,5,5-tetramethylpyrrolidin-1-oxyl-3-carboxylic acid (CP) when it is uncharged (at low pH) and K(col)⁻ when it is charged (CP⁻; at high pH), are measured as functions of temperature and ionic strength. The ratio f* ≡ K(col)⁻/K(col) is a direct measure of the effect of charge on the collision rate. Neglecting the small differences in size and diffusion coefficients of CP and CP⁻, f* is the fractional change in collision rate due to Coulomb repulsion which was treated theoretically in Debye's classic paper [Trans. Electr. Chem. Soc. 1942, 82, 265]. K(col) and K(col)⁻ are determined from EPR spectral changes due to spin-spin interactions which are dominated by Heisenberg spin exchange under the conditions of these experiments. Values of f* vary linearly with values of κ · d in the range 0.4 < κ · d < 1.8, where κ and d are the inverse Debye screening length and the distance at closest approach, respectively. Values of d obtained in two independent ways, (1) from rotational correlation times measured by EPR and (2) by insisting that the experimental results be consistent with the Debye theory at infinite dilution, yield similar results. As the ionic strength is increased (κ increased), the screening effect reduces the effect of the Coulomb barrier more slowly than predicted by the Debye theory. While values of K(col) and K(col)⁻ vary substantially with T, approximately following the Stokes-Einstein-Smoluchowski equation, values of f* depend only slightly on temperature at a given value of κ · d, as is predicted by Debye's theory.

Electron paramagnetic resonance line shifts and line shape changes due to spin exchange of nitroxide free radicals in liquids. 7. Singly charged surfactant nitroxide.

EPR spectra of aqueous solutions of the singly charged surfactant nitroxide 4-[N,N-dimethyl-N-(ndodecyl) ammonium]-2,2,6,6-tetramethylpiperidinyl-N-oxy bromide-d16 (DCAT12) are studied as functions of the molar concentration, c = 0.1-8 mM, and the temperature from 273 to 353 K. This concentration range is below the critical micelle concentration, cmc, at which DCAT12 forms micelles. Spin-spin broadening of the EPR lines averaged over the three lines is separated into contributions due to spin exchange, , and dipolar, , interactions yielding values of the fractional broadening by spin exchange, Omega(T), that vary from near unity at 353 K to approximately 50% at 273 K. This compares with a variation from unity to approximately 77% for a neutral spin probe perdeuterated 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (PDT) over the same range. Unlike PDT and the Stokes-Einstein prediction, the broadening constant by spin exchange, d/dc, is not linear with T/eta, where eta is the shear viscosity, instead following a quadratic dependence. Nevertheless, d/dc is remarkably close to a hydrodynamic prediction using the Stokes-Einstein equation modified to take the spin probe charge into account. Compared with PDT, values of d/dc are decreased and d/dc increased at all temperatures, while the values of the re-encounter rate, tau(RE)(-1), deduced from line shifts, are reduced. Interestingly, values of d/dc, Omega(T), and tau(RE)(-1) are comparable for PDT and DCAT12 when compared at the same rotational diffusion rates.