On-Bone Fixation of Free Gingival Graft Induces an Osteoinductive Effect in Human Alveolar Bone.

We examined alveolar bone samples in the area of on-bone fixation of a free gingival graft performed during surgery in patients aged 37-55 years with a diagnosis of secondary partial adentia of the upper and lower jaws. Six months after fixation of the graft in the alveolar bone, foci of neoosteogenesis were found in the contact zone. They were characterized by the appearance of appositional lines, cords of basophilic osteoblasts, and growing osteons. An immunohistochemical study revealed an increase in the number of CD44+, CD29+, and osteocalcin+ cells in the layer of the outer circumferential lamellae, primary osteons, and the lining of the Haversian canals. TGF-ß1+ cells were located in the intertrabecular reticular tissue and wall of microvessels. The results indicate activation of mesenchymal stem cells in the area of localization of the graft and differentiating osteoblasts. The observed osteoinductive effect of free gingival graft is associated with its participation in reorganization in MSC and induction of morphogenetic molecules.

Intraosseous microdialysis for bone free flap monitoring in head and neck reconstructive surgery: A prospective pilot study.

BACKGROUND: Although some researchers have positioned microdialysis catheters in the soft tissue surrounding bone, the results did not accurately reflect bone metabolism. The present study's objective was to establish the feasibility of microdialysis with a catheter positioned directly in bone. METHODS: Thirty-four patients (19 males, 15 females; median age: 59) were included in a prospective, nonrandomized clinical trial in the Department of Maxillofacial Surgery at Amiens-Picardie University Hospital (Amiens, France). Fibula or iliac crest free flaps were used in reconstructive head and neck surgery (for cancer, osteoradionecrosis, trauma, or ameloblastoma) and monitored with microdialysis catheters positioned in a hole drilled into the bone. Glucose, lactate, pyruvate, and glycerol concentrations were analyzed for 5 days. RESULTS: All catheters were positioned successfully, and thrombosis did not occur during the monitoring. In two patients, an increase in the lactate concentration and a glucose level close to 0 were associated with signs of flap necrosis, with removal on Days 9 and 50. In viable flaps, the mean glucose level was 2.02 mmol/L, the mean lactate level was 8.36 mmol/L, and the mean lactate/pyruvate ratio was 53. Forty percent of the glucose values were below 1 mmol/L, and 50% of the lactate/pyruvate ratio values were above 50-suggesting a specific metabolic pattern because these values would be considered as alert values in soft tissue. CONCLUSION: Monitoring bone free flaps with intraosseous microdialysis is feasible. This technique specifically assesses bone viability, and further studies are now necessary to define the alert values in bone.

Effect of Segment Length and Number of Osteotomy Sites on Cancellous Bone Perfusion in Free Fibula Flaps.

BACKGROUND: Indocyanine green (ICG) videoangiography is routinely used to evaluate skin and organ perfusion and to assess patency rates of microvascular anastomoses. This study uses ICG angiography as a novel approach to qualitatively and quantitatively evaluate bone perfusion of microvascular fibula grafts intraoperatively and to assess the effect of fibula segment length and number of osteotomies on bone perfusion. METHODS: All patients planned for mandible reconstruction using a microvascular fibula graft between January 2013 and May 2017 were considered for this study. ICG videoangiography of cancellous bone perfusion was performed using a handheld ICG camera. Videos were analyzed, and a perfusion curve was generated. Peak enhancement, time to peak, slope, and wash-in area under the curve were extracted; rise time, wash-in rate (WiR), and wash-in perfusion index were calculated. Results were statistically analyzed with regard to distal fibula segment length and number of osteotomy sites. RESULTS: Thirty-nine patients (age 59 ± 8 years) were included in the study. Mandible reconstruction was achieved with 1 (n = 15), 2 (n = 13), or 3 (n = 11) fibula segments. The WiR was 6.4 ± 2.3 and 4.4 ± 0.2 before and after proximal osteotomy, respectively. The wash-in perfusion index was 114.2 ± 48.4 before and 84.4 ± 20.0 after proximal osteotomy. Bone perfusion was significantly reduced after additional proximal osteotomies. Both the segment length and number of proximal osteotomies correlated with bone perfusion, with longer segments and fewer osteotomies showing higher perfusion. CONCLUSION: This study demonstrates the feasibility of cancellous bone perfusion analysis using ICG and can serve as a basis for future bone perfusion studies. Additional osteotomies and short segment length negatively affects cancellous bone perfusion of the distal fibula segment in free fibula flaps. The extent to which the observed decrease in arterial inflow to the distal fibula segment affects the further course of healing needs to be addressed in future studies.

Free Flap Head and Neck Reconstruction with an Emphasis on Postoperative Care.

Microsurgical free tissue transfer represents the mainstay of care in both ablative locoregional management and the simultaneous reconstruction of a defect. Advances in microsurgical techniques have helped balance the restoration of both form and function-decreasing the significant morbidity once associated with large ablative, traumatic, or congenital defects-while providing immediate reconstruction enabling early aesthetic and functional rehabilitation. There are a multitude of perioperative measures and considerations that aim to maximize the success of free tissue transfer. These include nutritional support, tight glycemic control, acknowledgment of psychological and psychiatric factors, intraoperative surgical technique, and close postoperative monitoring of the patients' hemodynamic physiology. While the success rates of free tissue transfer in experienced hands are comparable to alternative options, the consequences of flap failure are catastrophic-with the potential for significant patient morbidity, prolonged hospital stay (and associated increased financial implications), and increasingly limited options for further reconstruction. Success is entirely dependent on a continuous arterial inflow and venous outflow until neovascularization occurs. Flap failure is multifactorial and represents a dynamic process from the potentially reversible failing flap to the necrotic irreversibly failed flap-necessitating debridement, prolonged wound care, and ultimately decisions concerned with future reconstruction. The overriding goal of free flap monitoring is therefore the detection of microvascular complications prior to permanent injury occurring-identifying and intervening within that critical period between the failing flap and the failed flap-maximizing the potential for salvage. With continued technique refinement, microvascular free flap reconstruction offers patients the chance for both reliable functional and aesthetic restoration in the face of significant ablative defects. The caveat to this optimism is the requirement for considered perioperative care and the optimization of those factors that may offer the difference between success and failure.

Critical time for neovascularization/angiogenesis to allow free flap survival after delayed postoperative anastomotic compromise without surgical intervention: A review of the literature.

BACKGROUND: The aim of this study is to determine the minimal postoperative time required that may allow free flap survival after occlusion or ligation of the microsurgical anastomosis without surgical intervention. METHODS: All reports describing free flap survival and failure after delayed postoperative vascular compromise (after postoperative day 3); including thrombosis and ligation, without revision of the microsurgical anastomoses were reviewed. The type of flap, recipient site, vessel of occlusion, postoperative compromise day, and nonsurgical treatment were analyzed. RESULTS: 22 reports (32 flaps) detailed 16 arterial, 6 venous, and 10 simultaneously arterial and venous (vascular pedicle) compromise in 16 head and neck, 10 lower extremity, 4 breast, and 2 upper extremity free tissue transfers. 12 flaps survived without any intervention, 6 survived with conservative therapy (anticoagulation or leeches), and 14 survived despite pedicle ligation. The range of critical day of occlusion did not differ significantly among vessel types. 75% of arterial compromise occurred between 6 and 15 days. 75% of vascular pedicle compromise occurred between 8.5 and 18 days. When compared to jejunal flaps, skin flaps survived after earlier postoperative occlusion (10.2 vs. 20.8 days; P = 0.01). CONCLUSION: This analysis suggests that free flaps compromised by vascular thrombosis or pedicle ligation may survive with only conservative therapy when the event occurs after a minimal critical time period. Flap survival is more probable when arterial occlusion or pedicle ligation occurs after postoperative day 12, but this minimal critical period may be as low as 6 days for arterial occlusion. © 2016 Wiley Periodicals, Inc. Microsurgery 36:604-612, 2016.

Impact of active thermoregulation on the microcirculation of free flaps.

BACKGROUND: While it is a known fact that warming increases blood flow in healthy tissue, little is known about the impact of active thermoregulation on the altered microcirculation of free flaps. The objective of the study was to identify the impact of postoperative active thermoregulation on free flap microcirculation. METHODS: Tissue temperature was assessed in 25 free perforator flaps using an implanted probe. Active thermoregulation was achieved using a water circulation based system. Changes in microcirculation were evaluated at the day of surgery and throughout the first three postoperative days after passive cooling (room temperature), passive warming (wound dressing), active warming (38 °C) and active cooling (15 °C) using laser Doppler flowmetry and remission spectroscopy. RESULTS: Active warming increased flap temperature by 7.7% to 36.4 °C ± 0.5 °C in comparison to the initial values of flaps without dressing (P < 0.001). As a result, the blood flow increased by 77.7% of the base value (P < 0.001). A significant correlation between all microcirculation parameters and tissue temperature was observed with a 5.52 AU blood flow increase per degree temperature increase (r = 0.7; P < 0.001). All microcirculation parameters showed a statistically significant increase after both passive and active warming, whereby active warming showed significantly higher values than passive warming. CONCLUSIONS: Active thermoregulation using water-based circulation is an effective and safe procedure to improve microcirculation in free flaps and is superior to conventional passive warming strategies.

Evaluating visual perception for assessing reconstructed flap health.

BACKGROUND: Detecting failing tissue flaps before they are clinically apparent has the potential to improve postoperative flap management and salvage rates. This study demonstrates a model to quantitatively compare clinical appearance, as recorded via digital camera, with spatial frequency domain imaging (SFDI), a noninvasive imaging technique using patterned illumination to generate images of total hemoglobin and tissue oxygen saturation (stO2). METHODS: Using a swine pedicle model in which blood flow was carefully controlled with occlusion cuffs and monitored with ultrasound probes, throughput was reduced by 25%, 50%, 75%, and 100% of baseline values in either the artery or the vein of each of the flaps. The color changes recorded by a digital camera were quantified to predict which occlusion levels were visible to the human eye. SFDI was also used to quantify the changes in physiological parameters including total hemoglobin and oxygen saturation associated with each occlusion. RESULTS: There were no statistically significant changes in color above the noticeable perception levels associated with human vision during any of the occlusion levels. However, there were statistically significant changes in total hemoglobin and stO2 levels detected at the 50%, 75%, and 100% occlusion levels for arterial and venous occlusions. CONCLUSIONS: As demonstrated by the color imaging data, visual flap changes are difficult to detect until significant occlusion has occurred. SFDI is capable of detecting changes in total hemoglobin and stO2 as a result of partial occlusions before they are perceivable, thereby potentially improving response times and salvage rates.

The evaluation of flap growth and long-term results of pediatric mandible reconstructions using free fibular flaps.

Currently, the free fibular flap is well accepted as the first choice for mandibular reconstruction. Achieving functional results in pediatric patients requires a different approach than that employed for mature patients. Because the pediatric craniofacial skeleton continues to grow, reconstruction is more challenging, and the long-term results can be different from those of adult patients. In this study, we sought to measure flap growth objectively in our series. Ten pediatric patients who underwent reconstruction with free fibular flaps were retrospectively reviewed. Flap growth was evaluated by comparing the intraoperative photographs with photographs of the control panoramic mandibular radiographs taken using photo-anthropometric techniques. The measurements were converted to proportionality indices (PI), and these indices were compared. Subsequent complications and functional results were also evaluated. The mean patient age was 11.8 years, and the mean follow up was 57.7 months. The mean preoperative PI value was 10.74 ± 2.47. The mean postoperative PI value was 12.52 ± 2.34. The mean difference between the preoperative and postoperative PI values was -1.78 ± 0.53. These photo-anthropometric data clearly illustrated the growth of the fibular flaps (P = 0.001). None of these patients exhibited nonunion of the fractures; however, one patient experienced a delayed union, one had chronic temporomandibular joint pain, and one had chronic temporomandibular joint luxation. In two patients, the inter-incisive measurements were below the third percentile, and two additional patients had grade 2 eating abilities, which can be regarded as poor. All of the patients had symmetric mandibular contours. Free fibular flaps continue to grow in pediatric patients. This flap is a "workhorse" flap in children because it adapts to the craniofacial skeleton via its ability to grow, and this ability results in subsequent good cosmetic and functional results.

Variables affecting postoperative tissue perfusion monitoring in free flap breast reconstruction.

Postoperative flap monitoring is a key component for successful free tissue transfer. Tissue oxygen saturation measurement (TOx) with near-infrared spectrophotometry (NIRS) is a method used for this purpose. The aim of this study was to identify external variables that can affect TOx. Patients who had breast reconstruction with free flaps were monitored prospectively and intra-operative details were recorded. Flap TOx was recorded with NIRS pre-extubation, postextubation, and then every four hours for 36 hours. At each of these time points, blood oxygen saturation (SO2), amount of supplemental oxygen, and blood pressure were recorded. Thirty flaps were monitored. Initially, a significant trend over time was detected such that for every increase of 24 hours, TOx decreased on average by 2.1% (P = 0.025). However, when accounting for SO2 levels, this decrease was no longer significant (P = 0.19). An increase by 1% in SO2 produced an increase in TOx reading of 0.36 (P = 0.007). The amount of supplemental O2, systolic blood pressure, and diastolic blood pressure did not have a significant impact on TOx (P > 0.05). The TOx values were highest in the free TRAM flaps and were lower in decreasing order in the muscle-sparing TRAM, DIEP, and SIEA flaps (P > 0.05). The TOx values did not significantly correlate with vessel size, perforator number, or perforator row. Postoperative flap TOx was found to correlate with SO2 and was not significantly dependent on blood pressure, supplemental O2, or surgical variables. Careful interpretation of oximetry values is essential in decision making during postoperative flap monitoring.

Analysis of morphological and histologic changes in intraoral fasciocutaneous free flaps used for oropharyngeal reconstruction.

The fasciocutaneous flap transplanted into the oral cavity often acquires a gross appearance resembling that of intraoral mucosa. The purpose of this study was to analyze the histologic and morphological changes of the fasciocutaneous free flap in oropharyngeal reconstruction and attempt to determine the related causes. A study was done from January 2006 to February 2010. Study subjects included 67 of 239 patients who had undergone reconstructive surgery after oropharyngeal tumor resection. Histologic evaluation of biopsy specimens was also performed in 20 patients. The correlation of the morphological changes with various factors was analyzed. The histologic examination revealed that numerous histologic changes occurred although the overall structure of the skin was maintained. Analysis of the associated factors showed that the primary defect site was highly correlated with this morphological change in the intraoral flaps.Analysis of the associated factors showed that the primary defect site was highly correlated with this morphological change in the intraoral flaps. Histologic analysis reveals that fasciocutaneous free flaps maintain their feature as cutaneous skin yet undergo changes because of the characteristic oral cavity environment, which resulted in an intermediate-stage morphology.

Force recovery assessment of functioning free muscle transfers using ultrasonography.

PURPOSE: To evaluate the usefulness of ultrasonography for measurement of functioning free muscle transfer strength and estimate the capacity and potential of ultrasonography measurement. METHODS: Twenty-five patients underwent functioning free muscle transfer for brachial plexus injury. The cross-sectional areas (CSAs) of the transferred muscle and the contralateral gracilis (control) were measured using ultrasonography. First, the reliability and reproducibility of the ultrasonography measurements of the muscle CSA was investigated. Next, force recovery was evaluated by calculating the contraction ratio (CR), which was defined as the value equal to the CSA of the transferred muscle under maximum isometric contraction divided by the CSA value in a complete rest position. The CR of the contralateral gracilis was calculated in the same manner. The CR of the transferred muscle and the control were compared statistically. We also analyzed the correlation between the CR of the transferred muscle and other measurements of muscle strength. The follow-up duration was 24 to 87 months after surgery. RESULTS: The reliability and reproducibility of the ultrasonography measurements was determined statistically. The CR of the transferred muscle (1.30 ± 0.12) was significantly greater than that of the contralateral gracilis (1.22 ± 0.13). Furthermore, the CR of the transferred muscle showed significant correlations with both manual muscle testing and elbow arc of motion. CONCLUSIONS: Ultrasonography measurement of transferred muscle can easily indicate the recovery process of rehabilitation in a quantitative and dynamic manner. This study demonstrated that ultrasonography has the capacity to evaluate force recovery objectively. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Direct pulse oximetry within the esophagus, on the surface of abdominal viscera, and on free flaps.

BACKGROUND: Pulse oximetry is a noninvasive photometric technique that provides information about arterial blood oxygen saturation (SpO2) and heart rate and has widespread clinical applications. This is accomplished via peripheral pulse oximetry probes mainly attached to the finger, toe, or earlobe. The direct application of pulse oximetry to an organ, such as the esophagus, liver, bowel, stomach or free flap, might provide an indication of how well perfused an organ or a free flap is. Also, the placement of a pulse oximetry probe at a more central site, such as the esophagus, might be more reliable at a time when conventional peripheral pulse oximetry fails. METHODS: The focus of this article is the development and in vivo applications of new custom-made photoplethysmographic (PPG) and pulse oximetry optical and fiberoptic probes and instrumentation in an effort to investigate their suitability for the estimation of arterial blood oxygen saturation at different organs and tissues. The article will cover examples of application areas including real-time PPG and SpO2 monitoring for the esophagus and solid organs, including free flaps, using custom-made probes. RESULTS: Clinical studies have successfully demonstrated the feasibility of acquiring PPGs and estimating arterial blood oxygen saturation values from a variety of organs and tissues. CONCLUSIONS: The technological developments and the measurements presented in this work pave the way to a new era of pulse oximetry where direct and continuous monitoring of blood oxygen saturation of internal organs and tissues (esophagus, bowel, liver, stomach, free flaps) could be possible.

Colorimetric examination of typical free flap donor sites and comparison to recipient sites in the extremities.

Results after free flap reconstruction in the extremities are often impaired by missing color match of the transferred flap and the recipient site. But pre-existing color match is the precondition for satisfying aesthetic results. To obtain suitable free flap donor sites in terms of color for extremity reconstruction and to understand frequent color mismatch, we performed a colorimetric study including 60 healthy volunteers. Ten free flap donor sites were compared with ten recipient sites in the extremities. The results of our study showed that lower extremity sites are markedly lighter than upper extremity sites with the exception of the palmar forearm. We encountered an excellent color match of the radial forearm flap to the back of the hand (4.10 ± 1.91) and the palm of the hand (5.62 ± 2.21), and significantly relevant color match to the palmar aspect of the forearm (2.52 ± 1.23). Additionally, the lateral arm flap showed a remarkable color match to the dorsal aspect of the forearm (3.13 ± 2.06). Furthermore we encountered significantly relevant color match of the fibula flap to the anterior aspect of the lower leg (2.01 ± 1.08) and excellent color match of the anterolateral thigh flap (ALT) to the palmar aspect of the forearm (3.66 ± 2.10). No further significantly relevant color differences between the other donor sites and recipient regions were found. Colorimetric measurements are a helpful tool in reconstructive surgery to compare skin color of different anatomic sites.

[Comparative assessment of the reparative process of wounds of the liver and kidneys depending on the kind of plastic material in experiment].

In 52 rabbits a morphological assessment was made of regeneration of wounds of the liver and kidneys after their plasty with a seromuscle flap of the stomach on the vascular pedicle (26 rabbits), of hepatorhaphy and omentonephroplasty (26 rabbits) within the period from 1 to 360 days and was compared with literature data concerning reparation of the liver and kidney of the rabbit with the application of bio- and polymer materials for covering their wounds. The influence of plastic properties of the materials used on the productivity of the inflammatory-reparative process was established. In suturing the wounds of parenchymatous organs it is necessary to use plastic materials stimulating regeneration. The application of seromuscle flap of the stomach for these purposes improves the inflammatory-reparative process making it more productive as compared with bio- and polymer materials.

[Microneurovascular facial reanimation via the masseteric nerve: reconstruction alternative for long-standing facial palsy]. / Mikroneurovaskuläre Gesichtsreanimation über den N. massetericus : Rekonstruktionsalternative bei lang bestehender Fazialisparese.

BACKGROUND: The aim of the study was to retrospectively analyze the functional outcomes of microneurovascular facial reanimation using the masseteric innervation. PATIENTS AND METHODS: Seventeen patients with irreparable facial paralyses resulting from benign lesions involving the facial nuclei (n=14) or Möbius syndrome (n=3) were treated with free muscle flaps for oral commissural reanimation using ipsilateral masseteric innervation and using temporalis muscle transfer for eyelid reanimation. The results were analyzed by a commissural excursion (CE) index and a patient self-evaluation score. The presence of synkinesis was documented. Follow-up ranged from 8 to 48 months (mean 26.4 months). RESULTS: Normalization of the CE index could be observed in 8 out of 17 patients (47%), an improvement in 7 out of 17 (41%) and failure in 2 out of 17 (12%). A natural smiling response was observed in 10 out of 17 (59%) patients. Patient self-evaluation scores were a level higher than objective indices. CONCLUSIONS: Innervation of free muscle flaps with the masseteric nerve for oral commissure reanimation might play an important role in patients with long-standing facial palsy (as in Möbius syndrome). Synkinesis persists for long periods after surgery. However, most of the patients had learned to express their emotions by overcoming this phenomenon. Despite hypercorrection or inadequate correction, patients evaluate themselves favorably.

Near-infrared spectroscopy for monitoring free jejunal flap.

BACKGROUND: Although the free jejunal graft is commonly used for reconstruction after resection of a tumor of the pharynx or cervical esophagus, adequate monitoring for detecting graft failure is not available. We employed near-infrared spectroscopy to measure regional oxygen saturation (rSO2) in the graft. METHODS: In 25 consecutive cases who underwent reconstructive surgery using a free jejunal graft, the feasibility of postoperative rSO2 monitoring was examined along with the changes in rSO2 values following vascular clamping or reperfusion. RESULTS: No operative mortality occurred, and except for one case of subcutaneous hematoma that necessitated evacuation surgery, no complications related to surgery or graft failure occurred. Postoperative rSO2 monitoring was feasible for >50 hours in most cases. It mostly remained >55% with a stable hemoglobin index (HbI) which reflects tissue hemoglobin density. A marked increase in the HbI was noted in a patient with hematoma. Intraoperatively, the rSO2 of intact jejunal tissue was >60% in every case but dropped within a few minutes after arterial clamping because of decreased oxygenated hemoglobin concentration. With venous clamping, the HbI was elevated while the rSO2 remained unchanged or was slightly decreased. Upon graft reperfusion, the rSO2 rapidly recovered in all 18 cases because of the recovery of oxygenated hemoglobin concentrations. CONCLUSIONS: The near-infrared spectroscopic assessment sensitively and accurately reflected the condition of the jejunal graft. It appears to be a promising postoperative method for monitoring graft perfusion. An rSO2 value of 55% appears to be an adequate criterion for ischemia.

Measurement of optical reflection and temperature changes after blood occlusion using a wearable device.

Early detection of compromised circulation is essential for postoperative monitoring of free flap. Hourly clinical check-ups such as inspection and palpation still result in a delay in detection. Conversely, optical reflection and temperature measurement are useful alternatives for detecting blood circulation. However, conventional methods that verify ischemia and congestion within a short period have not been reported. In this study, we measured short-term changes in optical reflection and temperature in a rat flap using a wearable flexible sensor probe previously developed in our laboratory. Five ischemia and five congestion groin flap models were measured using a sensor probe and reference devices. Curve fitting was performed on transition signals to evaluate changes in signals and their time constants. The optical reflection signal decreased after venous ligation and increased after arterial ligation. The parameters of the fitted curves indicate a significant difference between congestion and ischemia at p < 0.01 (probability value), which was detected within a few minutes after ligation. However, insufficient significance was observed in the temperature signal. Our method gives supporting information to verify ischemia and congestion, and has the potential to rapidly detect compromised circulation.

Correlation between blood flow, tissue volume and microvessel density in the flap.

The purpose of this study was to assess the correlation between tissue volume and blood flow of the flap in an animal model. Using animal model, tissue volume can be attenuated, and precise change of blood flow could be evaluated. We further investigate the relationship between blood flow and vascular density in the tissue. In this study, we assessed flap conductance (ml/min/mm Hg) as to evaluate the conductivity of blood flow into the flap. Japanese white rabbit was used (n = 7) for this study. The amount of blood flow of jejunal and latissimus dorsi muscle (LD) flaps was measured while removing the distal portion of the flap sequentially. Conductance at each time was calculated from blood pressure and blood flow volume. The tissue volume at each time was also measured. The correlation between conductance and volume was analyzed using a linear mixed model. Immunohistochemical evaluation of microvessel densities (MVD) in these tissues was also performed for CD31/PECAM1 positive area. Conductance and tissue volume were significantly correlated in both jejunal and LD flaps. As the volume increases by 1 cm3, the conductance increased significantly by 0.012 ml/min/mm Hg in jejunum, and by 0.0047 ml/min/mm Hg in LD. Mean MVD was 1.15 ± 0.52% in the jejunum and 0.37 ± 0.29% in the LD muscle. In this study, we revealed that flap conductance is proportional to volume and proportional constant is different between the type of tissue. It suggests that the difference of MVD creates the unique conductance of each tissue.

Morphological analysis of ischemia-reperfusion injury in a cold ischemia model of jejunal free flap for hypopharyngeal reconstruction.

BACKGROUND: Jejunal free flap (JFF) reconstruction is a popular treatment option for advanced hypopharyngeal cancer. Several factors including ischemia-reperfusion injury (IRI) can cause mucosal damage and progressive flap necrosis. We investigated the development and time-related progression of morphological and cellular changes in patients with JFF reconstruction including cold preservation of the graft. METHODS: Eleven patients were enrolled. Biopsies were taken during surgery from normally perfused tissue, before loop isolation (T0), at the end of back-table surgery (T1), immediately before reperfusion (T2), 15' after reperfusion (T3), and at the end of the digestive anastomoses (T4) and from the external monitor daily from the 1st to the 5th postoperative day (M1-M5). Histomorphological and immunohistochemical parameters in the intraoperative and postoperative samples were evaluated and compared. RESULTS: Delayed flap necrosis was observed in 2 patients. The cold ischemia phase did not negatively affect mucosal regeneration after reperfusion; morphological and cellular damage parameters returned to normal by the end of surgery or along the early postoperative period. Significant enterocyte replication activity was observed at the end of revascularization, which continued in the postoperative phase, leading to recovery of the epithelial morphological integrity and disappearance of apoptotic cells. An inflammatory infiltrate persisted in the M samples, and in a significant proportion of samples, mucosal fibrosis developed by the end of the postoperative observation. CONCLUSION: Cold perfusion and preservation of the JFF can effectively limit the negative effects of IRI and to prevent short- and medium-term complications that can compromise the final outcome.

Free Flap Transfer for Pediatric Head and Neck Reconstruction: What Factors Influence Flap Survival?

OBJECTIVES: The objective of this study was to identify the factors that influence free flap survival after head and neck reconstructive surgery in pediatric patients. METHODS: One hundred thirty consecutive cases of head and neck reconstruction with free flaps in pediatric patients at the Department of Oral and Maxillofacial Surgery at Peking University School and Hospital of Stomatology, Beijing, People's Republic of China, between 1999 and 2017 were reviewed. A single head and neck surgical team performed all the included surgeries. Demographic and surgical patient data with possible associations with free flap survival were recorded. Relevant influencing factors were determined using the χ2 test and logistic regression analysis. RESULTS: There were 135 free flap transfers performed in the patients, with an overall success rate of 95.6%. Free flap failure occurred in six flaps (4.4%). Arterial crisis was the main cause of flap failure. The overall complication rate was 7.0%. Patient age (5-9 years old; odds ratio, 13.397; 95% confidence interval, 1.167-153.838; P = 0.037) was a statistically significant risk factor influencing free flap survival. Donor site, defect region, recipient vessel, and surgery time were not associated with free flap outcome. CONCLUSION: Free flap transfer for head and neck reconstruction in pediatric patients is safe and reliable. However, special attention should be paid to pediatric patients under 9 years of age when performing head and neck reconstruction. LEVEL OF EVIDENCE: 4 Laryngoscope, 129:1915-1921, 2019.