Post-operative monitoring of free muscle transfers by Laser Doppler Imaging: A prospective study

Flap Monitoring Techniques: A Review

Postoperative tissue flap vitality monitoring enables early detection of clinical complications, allowing for intervention. Timely re-operation can prevent the need for extensive correction procedures, thus reducing healthcare costs and hospitalization time. Statistics show that monitoring can increase the success rate of flap survival to 95% or higher. However, despite the significant progress in monitoring techniques, major and minor complications, leading to the loss of the flap, still occur. This clinical application review aims to provide a comprehensive overview of the recent advancements and findings in flap surgery reconstructions, transplants, and systems for their postoperative assessment. The literature from the years 1925 to 2024 has been reviewed to capture previous and current solutions for monitoring flap vitality. Clinically acclaimed methods and experimental techniques were classified and reviewed from a technical and clinical standpoint. Physical examination, metabolism change, ultrasound method, and electromagnetic (EM) radiation-based measurement methods were carefully evaluated from the perspective of their considered applications. Guidelines aiding engineers in the future design and development process of monitoring systems were proposed. This paper provides a comprehensive overview of the monitoring techniques used in postoperative flap vitality monitoring. It also gives an overview of each approach and potential ways for future development.

Application of supraclavicular island flap in oral and maxillofacial reconstruction

Several surgical modalities are available for maxillofacial reconstruction as locoregional or microvascular free flaps.

PURPOSE

(a) Evaluate the reliability of the supraclavicular flap in cervico-orofacial region; (b) investigate the role of computed tomography angiography (CTA) in predicting the post-operative viability of the flap; (c) assess the speech, feeding, and esthetics after reconstruction using this flap.

METHODS

Eleven patients included in this study underwent either conventional or delayed harvesting of the supraclavicular flap (SCF). All the patients had diagnostic computed tomography angiography (CTA) of the supraclavicular flap before the surgery.

RESULTS

The mean harvesting time of the flap was 45.45 ± 4.16 min. The average length of the flap was 22.64 ± 1.12 cm, whereas the mean width of the flap was 6.14 ± 1.14 cm. The flap survived in 9 patients, while two patients had complete flap loss. After the surgery, three patients complained of speech difficulties. Two patients had swallowing problems. After the surgery, three patients complained of speech difficulties. Two patients had swallowing problems. Only two patients complained of weakness in the donor site. None of the patients reported that the weakness or pain at the donor site affected their daily activities or quality of life.

CONCLUSION

The pedicled SCF represents a safe and feasible option that can be used to reconstruct a wide array of maxillofacial oncologic defects. However, a study with a larger sample size is recommended to achieve more reliable clinical results for the modified delayed technique modification in terms of their effect on the survival of the supraclavicular flap.

Postoperative free flap monitoring in reconstructive surgery-man or machine?

Free tissue transfer is widely used for the reconstruction of complex tissue defects. The survival of free flaps depends on the patency and integrity of the microvascular anastomosis. Accordingly, the early detection of vascular comprise and prompt intervention are indispensable to increase flap survival rates. Such monitoring strategies are commonly integrated into the perioperative algorithm, with clinical examination still being considered the gold standard for routine free flap monitoring. Despite its widespread acceptance as state of the art, the clinical examination also has its pitfalls, such as the limited applicability in buried flaps and the risk of poor interrater agreement due to inconsistent flap (failure) appearances. To compensate for these shortcomings, a plethora of alternative monitoring tools have been proposed in recent years, each of them with inherent strengths and limitations. Given the ongoing demographic change, the number of older patients requiring free flap reconstruction, e.g., after cancer resection, is rising. Yet, age-related morphologic changes may complicate the free flap evaluation in elderly patients and delay the prompt detection of clinical signs of flap compromise. In this review, we provide an overview of currently available and employed methods for free flap monitoring, with a special focus on elderly patients and how senescence may impact standard free flap monitoring strategies.

Efficacy of Combined in-vivo Electroporation-Mediated Gene Transfer of VEGF, HGF, and IL-10 on Skin Flap Survival, Monitored by Label-Free Optical Imaging: A Feasibility Study

Preventing surgical flaps necrosis remains challenging. Laser Doppler imaging and ultrasound can monitor blood flow in flap regions, but they do not directly measure the cellular response to ischemia. The study aimed to investigate the efficacy of synergistic in-vivo electroporation-mediated gene transfer of interleukin 10 (IL-10) with either hepatocyte growth factor (HGF) or vascular endothelial growth factor (VEGF) on the survival of a modified McFarlane flap, and to evaluate the effect of the treatment on cell metabolism, using label-free fluorescence lifetime imaging. Fifteen male Wistar rats (290–320 g) were randomly divided in three groups: group-A (control group) underwent surgery and received no gene transfer. Group-B received electroporation mediated hIL-10 gene delivery 24 h before and VEGF gene delivery 24 h after surgery. Group-C received electroporation mediated hIL-10 gene delivery 24 h before and hHGF gene delivery 24 h after surgery. The animals were assessed clinically and histologically. In addition, label-free fluorescence lifetime imaging was performed on the flap. Synergistic electroporation mediated gene delivery significantly decreased flap necrosis (P = 0.0079) and increased mean vessel density (P = 0.0079) in treatment groups B and C compared to control group-A. NADH fluorescence lifetime analysis indicated an increase in oxidative phosphorylation in the epidermis of the group-B (P = 0.039) relative to controls. These findings suggested synergistic in-vivo electroporation-mediated gene transfer as a promising therapeutic approach to enhance viability and vascularity of skin flap. Furthermore, the study showed that combinational gene therapy promoted an increase in tissue perfusion and a relative increase in oxidative metabolism within the epithelium.

Effect of short-term ischemia on microcirculation and wound healing of adipocutaneous flaps in the rat

PURPOSE

Composite flaps used in reconstructive surgery may intra- and postoperatively suffer from hypoperfusion and/or ischemia-reperfusion influencing wound healing. We aimed to follow-up the effect of ischemia on adipocutaneous flaps' wound healing and microcirculation.

METHODS

In anesthetized rats groin flaps were formed bilaterally. In Control group the flaps were repositioned and sutured back. In Ischemia-Reperfusion (I/R) group before repositioning and suturing the flap pedicles were clamped for 60 minutes. Laser Doppler (LD) fluxmetry and temperature probes were applied on the cranial, central and caudal flap regions before/after preparation and ischemia, re-suturing, and on the 1st-3rd-5th-7th-14th postoperative days, before the final examinations and biopsies for histology.

RESULTS

Flaps' skin temperature quickly recovered after repositioning. LD values were lower in the I/R group, reaching a significant level by the 3rd postoperative day, and remained lowered till the 14th day. The magnitude of alterations differed in the flap regions. Histologically normal wound healing process was seen, except for some I/R flaps, where hypertrophized mammary glands were found.

CONCLUSIONS

Short-term ischemia could influence flap microcirculation and wound healing, and may result in hypertrophized mammary glands. Laser Doppler could be used to evaluate intra- and postoperative microcirculatory changes and may have significance in predicting complications.

Relative Tissue Oxygenation and Temperature Changes for Detecting Early Upper Extremity Skin Ischemia

The authors' purpose was to determine whether there are reliable noninvasive methods of assessing upper extremity ischemia regardless of skin pigmentation. The authors conducted a study of healthy subjects classified based on skin pigmentation using the Fitzpatrick scale, the von Luschan color scale, and self-described race (two Hispanics, three Caucasians, and four African Americans). A surface temperature probe and a near-infrared spectroscopy monitor were placed on the posterior interosseous artery skin territory. Temporary upper limb ischemia was induced by tourniquet insufflation. Readings from both devices were taken at baseline and every 15 seconds for a total of 10 minutes of ischemia. During tourniquet insufflation, the authors found a reliable decrease in tissue oxygenation measured by near-infrared spectroscopy in all subjects and no significant change in temperature readings for any subjects. There was an average decrease of 19 percent in tissue oxygenation using near-infrared spectroscopy, with measurements on average starting at 77 percent and ending at 57 percent. There was no significant difference in the change in near-infrared spectroscopy oxygenation between participants with Fitzpatrick skin types 3, 4, and 5 or when participants were grouped into Fitzpatrick skin type less than or equal to 3 versus greater than 3, or when grouped into Fitzpatrick skin type less than or equal to 4 versus greater than 4. There was also no significant difference in participants grouped into von Luschan scores less than or equal to 20 versus greater than 20. In this healthy subjects study, near-infrared spectroscopy rapidly identified ischemia in all cases, whereas skin surface temperature did not. Near-infrared spectroscopy may be a reliable way of noninvasively monitoring for ischemia regardless of skin pigmentation degree. CLINICAL QUESTION/LEVEL OF EVIDENCE:: Diagnostic, IV.

Laser doppler imaging as additional monitoring after digital replanting: A prospective study

BACKGROUND

Despite various exisiting monitoring methods, there is still a need for new technologies to improve the quality of post-operative evaluation of digital replantation. The purpose of the study is using a laser Doppler imaging device (Easy-LDI) as an additional tool to assess perfusion. In this method, the changes in the frequency of the laser ligth provide information regarding perfusion of the monitored tissue.

PATIENTS AND METHODS

This study included seven patients (10 fingers; age of patients: 21-57 years) who suffered from a total (n = 6) or subtotal amputation (n = 4) due to accidents. In addition to hourly standard monitoring with clinical evaluation and skin thermometry, revascularized fingers were hourly monitored with Easy LDI for 48 h.

RESULTS

LDI measurement values ranged between 0.8 and 223 (mean 90.62 ± 21.42) arbitrary perfusion units (APU). The mean LDI values before and after revascularization were 7.1 ± 2.85 and 65.30 ± 30.83 APU, respectively. For the successful revascularized fingers (8 of 10 fingers) values from 19 to 223 APU (mean 98.52 ± 15.48) were demonstrated. All of the replants survived, but due to venous occlusion two digits required revision 12 and 35 h after revascularization, respectively. In the two cases, Easy-LDI also showed a constant and slow decline of the perfusion values. Furthermore, Pearson normalized correlation coefficient showed a positive significant correlation between temperatures of the replants and LDI-values (P < .001, r = +0.392) and a negative significant correlation between Δtemperature and LDI-values (P < .001, r = -0.474).

CONCLUSION

The LDI-device might be a promising additional monitoring technique in detection of perfusion disturbance in monitoring digital replantations.

The Effect of Skin Pigmentation on Determination of Limb Ischemia

PURPOSE

Timely identification of tissue ischemia is critical, both in the traumatized limb and following free tissue transfer. The purpose of this study was to determine if skin pigmentation affects the ability to detect limb ischemia.

METHODS

We conducted a study of healthy controls exposed to limb ischemia. The subjects were classified based on skin pigmentation using a defined skin type assessment tool, a visual color scale, and self-description of race. Participants were randomized by limb and tourniquet status; surgeons were blinded to both. Ischemia was induced by tourniquet insufflations, and board-certified orthopedic and plastic surgeons who had completed an accredited hand surgery fellowship conducted physical examinations. The surgeons monitored the forearms at 2, 6, and 10 minutes based on appearance of ischemia, capillary refill, and color in 3 locations on the limbs (posterior interosseous artery flap skin territory, radial forearm flap skin territory, and the digits).

RESULTS

We found a significant decrease in the ability to detect ischemia in participants with increased skin pigmentation, as documented by all metrics, when evaluating the posterior interosseous artery and radial forearm flap skin territories at all time points. For example, when monitoring the posterior interosseous artery flap with the tourniquet insufflated at time 10 minutes, 92.9% of Caucasians were correctly identified as being ischemic whereas only 23.3% of African Americans were correctly identified.

CONCLUSIONS

Skin pigmentation significantly affects the identification of an ischemic limb/skin flaps on physical examination. Whereas the standard treatment for monitoring of free tissue transfer is clinical examination, that may not be sufficient for patients with increased skin pigmentation. Surgeons should exercise particular vigilance during physical examination of a potentially ischemic limb/skin flaps with greater skin pigmentation.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

Improvement of Flap Necrosis in a Rat Random Skin Flap Model by In Vivo Electroporation-Mediated HGF Gene Transfer

BACKGROUND

Despite great understanding of underlying mechanisms for flap necrosis and advances in surgical techniques, flap necrosis remains a critical issue. In the present study, the authors investigated the efficacy of electroporation-mediated hepatocyte growth factor (HGF) gene delivery to random dorsal skin flaps (McFarlane) to accelerate wound healing and reduce flap necrosis.

METHODS

Fifteen male Wistar rats (290 to 320 g) were divided randomly into three groups. Group a, the control group (n = 5), underwent surgery and received no gene transfer. Group b received electroporation-mediated HGF gene delivery 24 hours after surgery as a treatment. Group c received electroporation-mediated HGF gene delivery 24 hours before surgery as prophylaxis (n = 5). Planimetry, laser Doppler imaging, and immunohistochemistry were used to assess the efficacy of HGF gene therapy among the groups.

RESULTS

Electroporation-mediated HGF gene delivery significantly decreased flap necrosis percentage compared with the control group in prophylactic and treatment groups (p = 0.0317 and p = 0.0079, respectively) and significantly increased cutaneous perfusion compared with the control group (p = 0.0317 and p = 0.0159, respectively). Moreover, Spearman rank correlation showed a significant negative correlation between flap necrosis percentage and laser index (p = 0.0213 and r = -0.5964, respectively). Furthermore, significantly higher mean CD31 vessel density was detected in treatment and prophylactic groups (p = 0.0079 and p = 0.0159, respectively). In addition, quantitative image analysis revealed significantly higher HGF protein expression in groups b and c (p = 0.0079 and p = 0.0079, respectively).

CONCLUSION

These findings suggested in vivo electroporation-mediated HGF gene delivery enhanced viability and vascularity of the ischemic skin flap.

Efficacy of In Vivo Electroporation-Mediated IL-10 Gene Delivery on Survival of Skin Flaps

Despite advances in understanding the underlying mechanisms of flap necrosis and improvement in surgical techniques, skin flap necrosis after reconstructive surgery remains a crucial issue. We investigated the efficacy of electroporation-mediated IL-10 gene transfer to random skin flap with an aim to accelerate wound healing and improve skin flap survival. Nine male Wistar rats (300-330 g) were divided in two groups (a) control group (n = 5), only surgery no gene transfer, and (b) experimental group, received electroporation-mediated IL-10 gene transfer 24 h before the surgery as prophylaxis (n = 4). Random skin flap (McFarlane) was performed in both groups. Planimetry, Laser Doppler imaging, and immunohistochemistry were used to evaluate the effect of IL-10 gene transfer between study groups at day 7. Electroporation-mediated IL-10 gene transfer decreased percentage of flap necrosis (p value = 0.0159) and increased cutaneous perfusion compared to the control group (p value = 0.0159). In addition, Spearman's rank correlation showed a significant negative correlation between percentage of flap necrosis and Laser Index (p value = 0.0083, r -0.83, respectively). Furthermore, significantly higher mean CD31⁺ vessel density was detected in the experimental group compared to the control group (p value = 0.0159). Additionally, semi-quantitative image analysis showed lower inflammatory cell count in experimental group compared to control group (p value = 0.0317). In vivo electroporation-mediated IL-10 gene transfer reduced necrosis, enhanced survival and vascularity in the ischemic skin flap.