Technical Variables in Lower Extremity Free Flap Reconstruction

BACKGROUND

 Lower extremity free flap failure rates are higher than in other areas of the body. While prior studies assessed the effect of intraoperative technical variables, these generally investigated individual variables and did not examine relationships between the many individual technical decisions made during free tissue reconstruction. Our purpose was to investigate the effect of variation in intraoperative microsurgical techniques on flap outcomes in a diverse cohort of patients requiring lower extremity free flap coverage.

METHODS

 Consecutive patients undergoing free flap reconstruction of the lower extremity at two level 1 trauma centers from January 2002 to January 2020 were identified using Current Procedural Terminology codes, followed by a review of medical records. Information regarding demographics and comorbidities, indications, intraoperative technical details, and complications was collected. Outcomes of interest included an unplanned return to the operating room, arterial thrombosis, venous thrombosis, partial flap failure, and total flap failure. Bivariate analysis was performed.

RESULTS

 In total, 410 patients underwent 420 free tissue transfers. The median follow-up time was 17 months (interquartile ranges: 8.0-37). Total flap failure occurred in 4.9% (n = 20), partial flap failure in 5.9% (n = 24), and unplanned reoperation in 9.0% (n = 37), with arterial thrombosis in 3.2% (n = 13) and venous thrombosis in 5.4% (n = 22). Overall complications were significantly associated with recipient artery choice, with arteries other than PT and AT/DP having a higher rate (p = 0.033), and with arterial revisions (p = 0.010). Total flap failure was also associated with revision of the arterial anastomosis (p = 0.035), and partial flap failure was associated with recipient artery choice (p = 0.032).

CONCLUSION

 Many interoperative options and techniques are available when performing microvascular lower extremity reconstruction that leads to equally high success rates. However, the use of arterial inflow outside of the posterior tibial and anterior tibial arteries leads to a higher overall complication rate and partial flap failure rate. Intraoperative revision of the arterial anastomosis portends poorly for ultimate flap survival.

Secondary Surgery after Lower Extremity Free Flap Reconstruction

BACKGROUND

Microsurgical free tissue transfer may be the only reconstructive option for lower extremity limb salvage. However, the functional and aesthetic results following free tissue transfer after initial salvage may be suboptimal, thus requiring secondary operations to facilitate definitive wound healing and/or refinement.

METHODS

A multi-institutional retrospective cohort study was performed including patients who underwent lower extremity free tissue transfer from January of 2002 to December of 2020. The authors' primary outcome variable was the presence of secondary surgery after free tissue transfer for lower extremity reconstruction. Independent variables (eg, wound cause, flap, donor type, recipient, comorbidities) were collected. Secondary surgery was categorized as (1) procedures for definitive wound closure and (2) refinement procedures. Multivariable logistic regression was performed to determine which variables were independently associated with the outcome.

RESULTS

A total of 420 free tissue transfers for lower extremity reconstruction were identified. Secondary surgery was performed in over half (57%) of the patients. Presence of diabetes (OR, 2.0; P = 0.01; 95% CI, 1.2 to 3.5) and use of a latissimus dorsi donor (OR, 2.4; P = 0.037; 95% CI, 1.1 to 5.4) were predictors of wound closure procedures. Fasciocutaneous (OR, 3.6; P < 0.001; 95% CI, 1.8 to 7.2) and myocutaneous (OR, 3.0; P = 0.005; 95% CI, 1.5 to 9.9) flaps were predictors of refinement procedures when compared with muscle-only flaps with skin grafts.

CONCLUSIONS

The majority of lower extremity free tissue reconstructions required secondary procedures to provide definitive wound closure and/or refinement. Overall, this study provides predictors of secondary surgery that will help formulate patients' expectations of lower extremity limb salvage.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, III.

Secondary amputation after lower extremity free-flap reconstruction

BACKGROUND

Microsurgical free-tissue transfer is often the definitive reconstructive option for lower extremity limb salvage. Despite an initial successful free-flap reconstruction, some patients ultimately undergo lower extremity amputation. The indications for secondary amputation include non- or malunion, infection, hardware failure, or chronic pain. This study aimed to identify the etiology and outcome of secondary amputation after lower extremity free-flap reconstruction.

METHODS

A retrospective cohort study was performed including patients who underwent lower extremity free-flap reconstruction from January 2002 to December 2020. Patients who underwent secondary amputation were identified. A survey based on the PROMIS® Pain Interference Scale and activities of daily living (ADLs) was then conducted to assess patient-reported outcomes. Fifteen (52%) patients who underwent amputation responded to the survey, with a median follow-up time of 4.4 years.

RESULTS

Of 410 patients who underwent lower extremity free-flap reconstruction, 40 (9.8%) patients underwent subsequent amputation. Of these, 10 patients had failed free-flap reconstruction and 30 patients had secondary amputation after an initially successful soft tissue coverage. The most common etiology for secondary amputation was infection (68%, n = 27). Eighty percent (n = 12) of survey respondents were able to use a prosthetic limb and ambulate.

CONCLUSIONS

The most common etiology of secondary amputation was infection. Most patients who ultimately underwent amputation were able to ambulate with a prosthetic, but the majority of patients reported chronic pain. This study could be used to guide potential free-flap candidates regarding the risks and outcomes of lower extremity free-flap reconstruction.

Massive Thymic Hyperplasia Masquerading as Cancer: A Case Report and Review of the Literature

A 34-year-old woman presenting with abdominal pain, chest pressure, weight loss, and tachycardia was found to have an 11.4-cm anterior mediastinal mass associated with intrathoracic lymphadenopathy on chest computed tomography (Fig. 1A). Core needle biopsy was concerning for a type B1 thymoma. During this patient's initial workup, she was found to have both clinical and laboratory evidence of Graves' thyroiditis, raising diagnostic suspicion for thymic hyperplasia rather than thymoma. The case discussed here highlights the unique challenges that arise in the evaluation and management of thymic masses and serves as a prudent reminder that both benign and malignant disorders may present with mass-like changes.

Vaccination of seronegative volunteers with a human immunodeficiency virus type 1 env/rev DNA vaccine induces antigen-specific proliferation and lymphocyte production of beta-chemokines

There is a pressing need to test novel vaccine concepts in an effort to develop an effective vaccine for human immunodeficiency virus (HIV) type 1. A phase I clinical study was done to test the immunogenicity of an HIV env/rev DNA vaccine, which was administered intramuscularly to HIV-1-seronegative persons. Subjects received 3 doses of vaccine at a single concentration (100 or 300 microgram) at 0, 4, 8, and 24 weeks. In at least 1 of multiple assays, the 6 subjects who received the 300-microgram dose had DNA vaccine-induced antigen-specific lymphocyte proliferative responses and antigen-specific production of both interferon-gamma and beta-chemokine. Furthermore, 4 of 5 subjects in the 300 microgram-dose group responded to both the rev and env components of the vaccine. The responses did not persist within inoculated individuals and scored in different individuals at different times in the trial. This study supports that HIV-1 DNA vaccine antigens can stimulate multiple immune responses in vaccine-naive individuals, and it warrants additional studies designed to enhance DNA vaccine immunogenicity.

HIV-1 DNA vaccines and chemokines

DNA vaccines have a demonstrated ability to induce humoral and cellular immune responses in animal models and humans. The technology, although it dates back to the 1950's, has had an insurgence of interest within the past few years following concurrent research papers. The basic technology is being applied broadly to viral, bacterial and parasitic infections. It has also been demonstrated that genes delivered via plasmid expression vectors result in expression of functional proteins in the inoculated host. Further, injection of plasmids encoding cytokine, chemokine or co-stimulatory molecules, also referred to as immunomodulatory plasmids can lead to the further expansion of this technology to include directed immunology. We have been developing DNA technology specifically with a focus as a vaccine against HIV-1 infection. We report that such vaccines can stimulate immune responses in a variety of relevant animal systems including humoral and cellular responses as well as the production of beta-chemokines. We describe that the beta-chemokines can both modulate the immune response induced by DNA vaccines and be modulated by the DNA vaccines in the murine and chimpanzee models as well as in humans.

Molecular and immunological analysis of genetic prostate specific antigen (PSA) vaccine

Nucleic acid immunization has been investigated as immunotherapy for infectious diseases as well as for treating specific types of cancers. In this approach, nucleic acid expression cassettes are directly inoculated into the host, whose transfected cells become the production source of novel and possibly immunologically foreign protein. We have developed a DNA vaccine construct which encodes for PSA by cloning a cDNA for PSA into a mammalian expression vector under control of a CMV promoter. We investigated and characterized the immunogenicity of PSA DNA expression cassettes in mice. PSA-specific immune responses induced in vivo by immunization were characterized by enzyme-linked immunosorbent assay (ELISA), T helper proliferation cytotoxic T lymphocyte (CTL), and flow cytometry assays. We observed a strong and persistent antibody response against PSA for at least 180 days following immunization. In addition, a significant T helper cell proliferation was observed against PSA protein. Using synthetic peptides spanning the PSA open frame, we identified four dominant T helper epitopes of PSA. Furthermore, immunization with PSA plasmid induced MHC Class I CD8+ T cell-restricted cytotoxic T lymphocyte response against tumor cell targets expressing PSA. The prostate represents a very specific functional organ critical for reproduction but not for the health and survival of the individual. Understanding the immunogenicity of PSA DNA immunization cassettes offers insight into the possible use of this tumor-associated antigen as a target for immunotherapy. These results demonstrate the ability of the genetic PSA to serve as a specific immune target capable of generating both humoral and cellular immune responses in vivo.

Neurocysticercosis in persons with epilepsy in Medellín, Colombia. The Neuroepidemiological Research Group of Antioquia

PURPOSE

A prospective series of 643 persons with epilepsy attending a reference neurologic center in Medellín, Colombia, was examined by computed tomography (CT scan) or serology or both with the enzyme-linked immunoelectrotransfer blot assay (EITB) to assess the prevalence of Taenia solium cysticercosis.

METHODS

All presenting patients were consecutively enrolled in the study. Five hundred forty-six persons underwent cerebral CT scans; 376 of them also had serum EITB performed.

RESULTS

Prevalence of neurocysticercosis by CT scan was 13.92%. Overall prevalence of T. solium antibodies with EITB was 9.82%, but for those with late-onset epilepsy (onset after age 30 years), prevalence increased to 17.5% and 19% for those who originated from outside urban Medellín. Seroprevalence in individuals with mixed lesions (cysts and calcifications) was 88.2% and 64.10% in those with live cysts. Conversely, only 2.72% of persons with CT findings not related to neurocysticercosis had positive EITB tests.

CONCLUSIONS

Our study shows that an important proportion of individuals with epilepsy have radiologic or serologic evidence of T. solium infection, suggesting that neurocysticercosis is an important etiology for epilepsy in Colombia.

Modulation of amplitude and direction of in vivo immune responses by co-administration of cytokine gene expression cassettes with DNA immunogens

Immunization with nucleic acids has been shown to induce both antigen-specific cellular and humoral immune responses in vivo. We hypothesize that immunization with DNA could be enhanced by directing specific immune responses induced by the vaccine based on the differential correlates of protection known for a particular pathogen. Recently we and others reported that specific immune responses generated by DNA vaccine could be modulated by co-delivery of gene expression cassettes encoding for IL-12, granulocyte-macrophage colony-stimulating factor and the co-stimulatory molecule CD86. To further engineer the immune response in vivo, we investigated the induction and regulation of immune responses following the co-delivery of pro-inflammatory cytokine (IL-1 alpha, TNF-alpha, and TNF-beta), Th1 cytokine (IL-2, IL-12, IL-15, and IL-18), and Th2 cytokine (IL-4, IL-5 and IL-10) genes. We observed enhancement of antigen-specific humoral response with the co-delivery of Th2 cytokine genes IL-4, IL-5, and IL-10 as well as those of IL-2 and IL-18. A dramatic increase in antigen-specific T helper cell proliferation was seen with IL-2 and TNF-alpha gene co-injections. In addition, we observed a significant enhancement of the cytotoxic response with the co-administration of TNF-alpha and IL-15 genes with HIV-1 DNA immunogens. These increases in CTL response were both MHC class I restricted and CD8+ T cell dependent. Together with earlier reports on the utility of co-immunizing using immunologically important molecules together with DNA immunogens, we demonstrate the potential of this strategy as an important tool for the development of more rationally designed vaccines.

Modulation of amplitude and direction of in vivo immune responses by co-administration of cytokine gene expression cassettes with DNA immunogens

Immunization with nucleic acids has been shown to induce both antigen-specific cellular and humoral immune responses in vivo. We hypothesize that immunization with DNA could be enhanced by directing specific immune responses induced by the vaccine based on the differential correlates of protection known for a particular pathogen. Recently we and others reported that specific immune responses generated by DNA vaccine could be modulated by co-delivery of gene expression cassettes encoding for IL-12, granulocyte-macrophage colony-stimulating factor and the co-stimulatory molecule CD86. To further engineer the immune response in vivo, we investigated the induction and regulation of immune responses following the co-delivery of pro-inflammatory cytokine (IL-1 alpha, TNF-alpha, and TNF-beta), Th1 cytokine (IL-2, IL-12, IL-15, and IL-18), and Th2 cytokine (IL-4, IL-5 and IL-10) genes. We observed enhancement of antigen-specific humoral response with the co-delivery of Th2 cytokine genes IL-4, IL-5, and IL-10 as well as those of IL-2 and IL-18. A dramatic increase in antigen-specific T helper cell proliferation was seen with IL-2 and TNF-alpha gene co-injections. In addition, we observed a significant enhancement of the cytotoxic response with the co-administration of TNF-alpha and IL-15 genes with HIV-1 DNA immunogens. These increases in CTL response were both MHC class I restricted and CD8+ T cell dependent. Together with earlier reports on the utility of co-immunizing using immunologically important molecules together with DNA immunogens, we demonstrate the potential of this strategy as an important tool for the development of more rationally designed vaccines.

[Prevalence of neurocysticercosis in individuals affected by epilepsy]

INTRODUCTION

In this investigations, was carried out a neurocysticercosis (NC) prevalence study during seven months in the Instituto Neurológico de Antioquia with the purpose of known neurocysticercosis frequency as cause of epilepsy in patients older than ten years that we attended in our institute.

MATERIAL AND METHODS

Computerized tomographies (CT) were made to 503 patients, with epilepsy, 24.7% of them were CT positive for NC. Cysticercosis enzyme linked immunoelectrotransfer blot (EITB) and enzyme linked immunoabsorbent assay (ELISA) test were made to 178 patients, 19.6% were EITB positive for NC and 5% ELISA positive for NC. Results. From this result it is possible to infer that about 8% of the 503 patients with epilepsy had cysticercosis, according to EITB that is the golden assay for NC. The CT and ELISA test had 94.3% and 27.7% sensitivity, respectively, according to EITB. The specificity of the CT for NC was 49.2% and specificity for ELISA test was 100% as compared to EITB. The multivariate analysis with logistic regression allowed to establish association of positive EITB with factors such as male sex, eating pork, headaches and multiple lesions in CT.

CONCLUSIONS

Prevention and education actions are necessary for the interruption of the neurocysticercosis transmission chain in order to diminish the high prevalence of epilepsy in the country and its complication and consequences.