Value of a smartphone‐compatible thermal imaging camera in the detection of peroneal artery perforators: Comparative study with computed tomography angiography

An overview of current assessment techniques for evaluating cutaneous perfusion in reconstructive surgery

This article provides a comprehensive analysis of modern techniques used in the assessment of cutaneous flaps in reconstructive surgery. It emphasizes the importance of preoperative planning and intra- and perioperative assessment of flap perfusion to ensure successful outcomes. Despite technological advancements, direct clinical assessment remains the gold standard. We categorized assessment techniques into non-invasive and invasive modalities, discussing their strengths and weaknesses. Non-invasive methods, such as acoustic Doppler sonography, near-infrared spectroscopy, hyperspectral imaging thermal imaging, and remote-photoplethysmography, offer accessibility and safety but may sacrifice specificity. Invasive techniques, including contrast-enhanced ultrasound, computed tomography angiography, near-infrared fluorescence angiography with indocyanine green, and implantable Doppler probe, provide high accuracy but introduce additional risks. We emphasize the need for a tailored decision-making process based on specific clinical scenarios, patient characteristics, procedural requirements, and surgeon expertise. It also discusses potential future advancements in flap assessment, including the integration of artificial intelligence and emerging technologies.

Smartphone-based thermography in flap surgery: A systematic review and meta-analysis of perforator identification

Background

Thermography can be used in pre-operative planning of free perforator flap surgeries. Thermography assesses skin temperature by measuring the quantity of infrared radiation observed. In this meta-analysis, authors assess the sensitivity of smartphone-based thermal imaging (SBTI) in the detection of perforators and analyze the difference between static and dynamic imaging.

Materials and methods

Authors followed the PRISMA guidelines for systematic reviews and meta-analyses. The meta package in R was used to conduct the meta-analysis. The "metaprop" function was used to calculate the overall sensitivity estimate and 95% confidence interval. The "metaprop.one" function was used to calculate subgroup estimates for static and dynamic study types. The "metareg" function was used to conduct meta-regression analyses to explore sources of heterogeneity.

Results

This study includes seven articles with 1429 perforators being evaluated. The overall proportion of the sensitivities was estimated to be 0.8754 (95% CI: 0.7542; 0.9414) using a random effects model. The heterogeneity of the studies was high, as indicated by the tau^2 value of 1.2500 (95% CI: 0.4497; 8.4060) and the I^2 value of 92.6% (95% CI: 88.1%; 95.4%). The pooled sensitivity for static imaging was 0.8636 (95%CI: 0.6238-0.9603) with a tau^2 of 2.0661 and a tau of 1.4374, while the pooled sensitivity for dynamic imaging was slightly higher (p = 0.7016) at 0.8993 (95%CI: 0.7412-0.9653) with a smaller tau^2 of 0.8403 and a tau of 0.9167.

Conclusion

Further studies need to confirm that SBTI is a reliable and convenient technique for detecting perforators for the pre-operative planning of free perforator flap surgeries.

Value of the combination of a smartphone-compatible infrared camera and a hand-held doppler ultrasound in preoperative localization of perforators in flaps

This study was conducted to evaluate the effectiveness of the FLIR ONE PRO, a thermal imaging camera for smartphones, combined with handheld Doppler (HHD) in the localization of perforator arteries and to assess the efficacy of the FLIR ONE PRO in distinguishing perforators of the descending branch of the lateral circumflex femoral artery (LCFA) from other perforators of the anterolateral thigh perforator (ALTP) flap. We enrolled 29 free perforator flaps from 22 patients in our study. Before surgery, dynamic infrared thermography was performed using a FLIR ONE PRO to visualize hotspots on the flaps. Subsequently, HHD was used to further determine the perforators under the hotspots, which were ultimately identified and confirmed through intraoperative findings. Additionally, infrared images of the ALTP flap were analyzed using FLIR Tools. The performances of the FLIR ONE PRO and FLIR ONE PRO + HHD groups were evaluated by comparing the intraoperative findings. Using FLIR ONE PRO + HHD, 119 hotspots and 106 perforators were identified during surgery. Using FLIR ONE PRO + HHD, sensitivity and positive predictive value were 97.87% and 88.46%, respectively, in the young (age≤45 years). In the elderly group (age>45 years), these percentages were 93.22% and 82.09%, respectively. In addition, we found that the FLIR ONE PRO could be useful for differentiating perforators in the descending branch of the LCFA from other perforators within 5 min. The results showed a sensitivity of 96.15%, a specificity of 98.9%, a positive predictive value of 96.15%, and a negative predictive value of 98.9%. Compared to using FLIR ONE PRO alone, the combined application of HHD and FLIR ONE PRO had a higher value in perforator localization by increasing the positive predictive value. The FLIR ONE PRO may have significance in the rapid prediction of perforators deriving from the descending branch of the LCFA.

[Application of infrared thermography technique to assist peroneal artery perforator flap in the repair of oral and maxillofacial defects]

Objective

To explore the application value of infrared thermography (IRT) technique assisted peroneal artery perforator flap in repairing oral and maxillofacial defects.

Methods

The clinical data of 20 patients with oral and maxillofacial malignant tumors treated with peroneal artery perforator flap between October 2020 and December 2021 were retrospectively analysed. There were 13 males and 7 females, with an average age of 56.5 years (range, 32-76 years). There were 8 cases of tongue cancer, 5 cases of parotid gland cancer, 4 cases of buccal cancer, and 3 cases of mandibular gingival cancer; and 12 cases of squamous cell carcinoma, 3 cases of adenoid cystic carcinoma, and 5 cases of mucoepidermoid carcinoma. Color Doppler ultrasound (CDU) and IRT technique were performed before operation to locate the peroneal artery perforator and assist in the design of the flap. The sensitivity, specificity, positive predictive value, and negative predictive value of CDU and IRT technique were compared with the actual exploration during operation. The accuracy of CDU and IRT technique in detecting the number of peroneal artery perforator and the most viable perforating points was compared. The patients were followed up regularly to observe the recovery of donor and recipient sites, the occurrence of complications, and the recurrence and metastasis of tumors.

Results

The sensitivity, specificity, positive predictive value, and negative predictive value of peroneal artery perforators detected by IRT technique before operation were 72.22%, 50.00%, 92.86%, and 16.67% respectively, which were higher than those by CDU (64.17%, 33.33%, 84.62%, and 14.29% respectively). Forty-five peroneal artery perforators were found by CDU before operation, and 35 were confirmed during operation, with an accuracy rate of 77.8%; 43 "hot spots" were found by IRT technique, and 32 peroneal artery perforators were confirmed within the "hot spots" range during operation, with an accuracy rate of 74.4%; there was no significant difference between the two methods ( χ²=0.096, P=0.757). The accuracy rates of the most viable perforating points found by CDU and IRT technique were 80.95% (17/21) and 94.74% (18/19), respectively, and there was no significant difference between them ( χ²=0.115, P=0.734). The localization errors of CDU and IRT technique were (5.12±2.10) and (4.23±1.87) mm, respectively, and there was no significant difference between them ( t=1.416, P=0.165). All the perforator flaps survived, and the incisions of donor and recipient sites healed by first intention. All patients were followed up 5-18 months, with an average of 11 months. The skin flap was soft and had good blood supply, and the lower limb scar was concealed and the lower limb had good function. No lower limb swelling, pain, numbness, ankle instability, or other complications occurred, and no tumor recurrence and metastasis were found during the follow-up.

Conclusion

Compared with the CDU, using the IRT technique to assist the preoperative peroneal artery perforator flap design to repair the oral and maxillofacial defects has a high clinical application value.

Application of an L-shaped anterolateral thigh flap in reconstruction after hemiglossectomy

Objective

Tongue defect reconstruction is one of the key components of tongue cancer surgery. In this study, we used an L-shaped flap design adopted as a simple and efficient method to repair tongue defects after hemiglossectomy. Furthermore, we evaluated and contrasted the clinical effects of two methods, the L-shaped and traditional methods.

Study design

Fifteen patients in the L-shaped group and 20 patients in the traditional group were evaluated and compared in terms of postoperative complications, dysphagia, language function and appearance satisfaction.

Results

The results (Table 1) showed that there were 2 cases of donor area invalid traumas, and 2 patients had scar hyperplasia in the traditional group. The degree of global and functional dysphagia of the L-shaped group (2.60 ± 0.29 and 11.47 ± 1.38) was lower than that of the traditional group (3.55 ± 0.29 and 15.75 ± 1.22) (P < 0.05). In the language evaluation, the traditional group (3.20 ± 0.26) had lower scores than the L-shaped group (4.13 ± 0.30) (P < 0.05).

Conclusion

The L-shaped ALTP flap is a simple and efficient modification of ALTP, that can be used for half-tongue repair after radical operations for tongue cancer. It has better performance in the recovery of dysphagia and language function than the traditional ALTP flap.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12893-022-01473-7.

Perforator Detection by Thermographic Imaging Augmented With Tourniquet-Reperfusion: A Modified Approach and Preliminary Report in Distal Lower Leg Reconstruction

BACKGROUND

Dynamic infrared thermography provides a new imaging method of perforator detection. This study introduces an augmented technique to improve its accuracy by tourniquet-reperfusion and reports its preliminary use in the distal lower leg reconstruction.

METHODS

A tourniquet (450 mm Hg) was applied for 3 minutes on proximal thighs. After the tourniquet release, the rewarming rate and pattern of hotspots were observed by thermography to delineate the location and quality of perforators. The results were compared with those detected by computed tomographic angiography. Clinically, the local transferred posterior tibial artery or peroneal artery propeller perforator flap was performed in 9 patients for the distal lower leg reconstruction.

RESULTS

There was a 20- to 140-second "perforator observing window" after the tourniquet release. Tourniquet-reperfusion augmented thermal imaging method (TRATIM) had a sensitivity of 90.3% and a positive predictive value of 93.3%. The TRATIM and computed tomographic angiography had an excellent concordance with a kappa index value of 0.839 (P < 0.001). Based on the TRATIM, 9 propeller perforator flaps were successfully designed and raised for the distal lower leg resurfacing. All flaps survived entirely, except one with size of 1.0 cm × 2.0 cm that had terminal necrosis.

CONCLUSIONS

The TRATIM is a quick, easy, cheap, and reliable approach for perforator detection in the lower leg. With the aid of TRATIM, a customized propeller perforator flap could be raised efficiently for the distal lower leg reconstruction.

Performance of infrared thermography and thermal stress test in perforator mapping and flap monitoring: A meta-analysis of diagnostic accuracy

BACKGROUND

Accurate mapping of perforators prior to flap reconstruction and early detection of poor flap perfusion reduces the risk of flap failure. Infrared thermography (IRT) has recently regained popularity within reconstructive surgery to aid flap design, reduce operative time and assess flap viability based on surface temperature changes. The aim of this review is to quantify the diagnostic ability of IRT in perforator mapping preoperatively and monitor flap perfusion perioperatively.

METHODS

We conducted a systematic review of literature and included all studies that evaluated the use of IRT for perforator mapping and flap perfusion monitoring. We used a mixed-effects logistic regression bivariate model to estimate the summary sensitivity and specificity and constructed hierarchical summary receiver operative characteristic (HSROC) curves.

OUTCOME

We identified 18 studies and observed IRT to have sensitivities of 99.6% and 89.6% with specificities of 99.9% and 96.0% for perforator mapping and flap monitoring, respectively. Moreover, IRT recognises patterns of perfusion within interperforator zones through visualisation of angiosomal rewarming and may improve flap outcomes.

Correlation between ankle-brachial index and thermography measurements in patients with peripheral arterial disease

OBJECTIVES

To correlate the ankle-brachial index and photographic thermography findings in patients with peripheral arterial disease.

METHODS

Photographic thermography was performed at the foot level, and ankle-brachial index was measured in 72 lower limbs of 53 patients with peripheral arterial disease who were divided into calcified artery, patients with an ankle-brachial index greater than 1.4; and non-calcified artery classified as asymptomatic, mild, moderate, and severe on the basis of peripheral arterial disease severity. Fisher's exact test was used for categorical data, and Wilcoxon test was used for numerical data.

RESULTS

Spearman's correlation analysis showed a strong correlation (R = 0.7) between the ankle-brachial index and the mean plantar temperature in patients without lower limb artery calcification. Linear regression yielded the predictor equation Y = 3.296 × X + 29.75, wherein ankle-brachial index (X) can be predicted on the basis of temperature values. Spearman's correlation test showed no significance (p = 0.2174) in patients with arterial calcification. Kruskal-Wallis test with post hoc analysis using Dunn's test for multiple comparisons showed that the mean plantar temperature was lower in patients with arterial calcification.

CONCLUSION

Photographic thermography findings show a strong correlation with ankle-brachial index in patients with non-calcified arteries.

Accuracy of infrared thermography for perforator mapping: A systematic review and meta-analysis of diagnostic studies

INTRODUCTION

Infrared thermography allows the detection of infrared radiation which can be reliably associated with skin temperature. Modern portable thermography devices have been used to identify the location of skin perforators by detecting subtle differences in skin temperature. The aim of this study is to conduct a diagnostic accuracy systematic review to determine the specificity and sensitivity of infrared thermography.

MATERIALS AND METHODS

A PRISMA-compliant systematic review and meta-analysis was conducted, scrutinising PUBMED and EMBASE databases for diagnostic studies measuring the accuracy of infrared thermography for perforator identification. Article screening, review and data gathering was conducted in parallel by two independent authors. Eligible studies were subject to a formal risk of bias was assessment using the QUADAS2 instrument.

RESULTS

A total of 254 entries were obtained, of which 7 satisfied our pre-established inclusion criteria. These studies reported a total of 435 perforators in 133 individuals. The most commonly investigated locations were the antero-lateral thigh and abdominal wall. Reported sensitivity values ranged from 73.7% to 100%. A meta-analysis demonstrated a cumulative sensitivity of 95%. Specificity was not routinely reported. All studies presented a moderate to high risk of bias according to QUADAS2.

DISCUSSION

Affordable infrared thermography devices are an interesting alternative to traditional preoperative investigations for perforator mapping. They are sensitive enough to reliably identify a large proportion of perforators as "hot-spots". However, there is limited evidence to estimate the specificity of this technology, as studies have failed to report true negative values associated with "cold-spots".