Intraoperative evaluation of blood flow for soft tissues in orthopaedic surgery using indocyanine green fluorescence angiography: A pilot study

Application of indocyanine green fluorescence angiography in evaluating blood flow in rotator cuff tears: a preliminary study

BACKGROUND

The relationship between the degree of vascularization at the edge of a torn rotator cuff tendon and cuff healing remains unclear. The purpose of this study was to employ indocyanine green (ICG) fluorescence angiography to evaluate the blood flow at the edge of a torn rotator cuff tendon under the subacromial view.

METHODS

Thirteen shoulders of 13 patients who underwent arthroscopic repair of full-thickness rotator cuff tears were included in this prospective study. Viewing from the posterolateral portal, ICG at 0.2 mg/kg body weight was intravenously administered, and the blood flow was recorded. After resecting the poorly vascularized torn edge of the tendon, ICG administration was repeated at the same volume. The fluorescence intensity and perfusion time of the tendon blood flow were evaluated using video analysis and modeling tools. Cuff integrity was evaluated using magnetic resonance imaging at 6 months postoperatively. Patients were divided into healed and retear groups, and the differences in the degree of blood flow were evaluated.

RESULTS

ICG fluorescence angiography could visualize the blood flow in the rotator cuff tendon, and the torn edge of the tendon with poor blood flow was resected. The overall retear rate was 23.1% (3/13). Based on quantitative analysis, the fluorescence intensity factors were significantly lower in the retear group than in the healed group before tendon débridement. The retear rate in the high blood flow group was 0% (0/7), while that in the low blood flow group was 50.0% (3/6).

CONCLUSIONS

ICG fluorescence angiography may play a role in the future of shoulder arthroscopy. Further study is needed to determine the effect of blood flow on tendon healing.

Blood Flow in the Meniscus Can Be Visualized Arthroscopically Using an Intravenous Indocyanine Green Solution Diluted 10× in a Pig Model

Purpose

To determine the optimal indocyanine green (ICG) dose required for assessing vascularity in the meniscus using ICG fluorescence-guided knee arthroscopy in a pig model.

Methods

A 3-month-old Japanese esculent female pig was used in this study. Intravenous injections of ICG (25 mg) were administered with 2.0 mL of 5×, 10×, 100×, and 1,000× diluted solutions. An additional experiment was conducted to assess the microvasculature within the meniscus considering the results of the optimal dilution setting. A radial tear was purposely induced in the middle-to-posterior section of the medial meniscus to observe vascularity in the cross-sectioned meniscus; the optimal ICG dilution was administered.

Results

No fluorescence was detected in the meniscus with solutions diluted by 1,000× and 100×. Fluorescence was visualized at the anterior portion of the synovium and the anterior cruciate ligament using ICG diluted by 10×. Diluting ICG by 5×, contrast enhancement was too intense for observation. Therefore, the 10× diluted solution was considered the optimal setting for knee arthroscopy and observation of the radial tear. No fluorescence was observed in the cross section of the medial meniscus. Arterial hemorrhage was observed by stimulating the fluorescence-dyed synovium adjacent to the tear site. Through the additional waiting time after stimulating the tear site, the hemorrhage inside the meniscus became more intense.

Conclusions

The optimal dilution and dose setting of ICG for knee arthroscopy was 10× in a 2.0-mL intravenous injection. The meniscus showed no active blood flow, even in the red-red zone. This finding might support the notion that blood flow cannot be initiated, without synovial stimulation, even in vascular areas.

Clinical Relevance

This study could determine an ICG solution suitable for ICG fluorescence-guided knee arthroscopy. This finding could be valuable in future research focusing on case-specific meniscal vascularization under arthroscopy, particularly applying these findings to human meniscal treatment.

Indocyanine Green Fluorescence-Guided Knee Arthroscopy: A Technical Note for Investigating the Microvasculature Around the Meniscus

Vascularity of the meniscus is the most important key to meniscal tear healing. However, blood supply to the meniscus is limited to approximately the outer 10% to 25% of the meniscus, known as the "red-red zone." The cyanine dye indocyanine green (ICG) is commonly used as a contrast imaging agent for visualizing vascularity in several medical fields. Moreover, ICG fluorescence-guided surgery is a modern trend in the field of laparoscopic surgery in which the characteristic of fluorescence enhancement under a near-infrared light is used. However, ICG fluorescence-guided knee arthroscopy findings remain unknown. In this Technical Note, the author applied ICG fluorescence-guided surgery to knee arthroscopy to evaluate blood supply to the meniscus and intra-articular apparatus. Additionally, the arthroscopic findings of ICG fluorescence-guided knee arthroscopy for degenerative tears of the medial meniscus before and after meniscal repair are presented. Through the intravenous injection of ICG solution, real-time detection of fluorescence may contribute to investigating case-specific vascularization of the meniscus during arthroscopy in the next generation.

Current and Future Applications of Fluorescence Guidance in Orthopaedic Surgery

Fluorescence-guided surgery (FGS) is an evolving field that seeks to identify important anatomic structures or physiologic phenomena with helpful relevance to the execution of surgical procedures. Fluorescence labeling occurs generally via the administration of fluorescent reporters that may be molecularly targeted, enzyme-activated, or untargeted, vascular probes. Fluorescence guidance has substantially changed care strategies in numerous surgical fields; however, investigation and adoption in orthopaedic surgery have lagged. FGS shows the potential for improving patient care in orthopaedics via several applications including disease diagnosis, perfusion-based tissue healing capacity assessment, infection/tumor eradication, and anatomic structure identification. This review highlights current and future applications of fluorescence guidance in orthopaedics and identifies key challenges to translation and potential solutions.

Excessively High Repair Tension Decreases Microvascular Blood Flow Within the Rotator Cuff

BACKGROUND

Repair tension and microvascular blood flow within the rotator cuff has a critical impact on tendon healing after rotator cuff repair. However, the relationship between repair tension and microvascular blood flow within the rotator cuff remains unclear.

PURPOSE/HYPOTHESIS

The purpose of this study was to determine how much tension adversely affects microvascular blood flow within the rotator cuff. The hypothesis was that as the repair tension increases, the microvascular blood flow within the rotator cuff decreases.

STUDY DESIGN

Controlled laboratory study.

METHODS

Repair tension and microvascular blood flow within the rotator cuff of 30 patients with full-thickness rotator cuff tears were simultaneously measured using a digital tension meter and a contact-type laser Doppler flowmeter, respectively. Microvascular blood flow was measured under 4 levels of tension (0, 10, 20, and 30 N) at 5 points on the rotator cuff. The obtained values were statistically analyzed by a linear mixed-effects model to clarify the effect of tension on microvascular blood flow within the rotator cuff.

RESULTS

There was no statistically significant difference in microvascular blood flow (mL/min/100 g) within the rotator cuff between 0 N (mean, 3.51; 95% CI, 3.0-4.0) and 10 N (mean, 3.74; 95% CI, 3.2-4.3) of tension (P = .716). However, there were statistically significant differences in microvascular blood flow within the rotator cuff between 0 and 20 N of tension (mean, 2.84; 95% CI, 2.3-3.4) (P = .002) and between 0 and 30 N of tension (mean, 2.45; 95% CI, 1.9-3.0) (P < .001).

CONCLUSION/CLINICAL RELEVANCE

Our findings indicate that tension of ≥10 N during rotator cuff repair significantly decreases the microvascular blood flow within the rotator cuff. These data will contribute to determining the optimal repair tension during rotator cuff repair.

[Evaluation methods of postoperative healing of supraspinatus tendon tear]

Objective

To summarize the evaluation methods of postoperative healing of supraspinatus tendon tear in recent years, in order to provide reference for clinic.

Methods

CNKI, Wanfang, PubMed, and Foreign Medical Literature Retrieval Service (FMRS) databases were used to search the literatures between 2005 and 2022. The literature related to the diagnosis and postoperative healing of supraspinatus tendon tear was included. Finally, 50 articles were reviewed.

Results

Supraspinatus tendon tear is a common shoulder disease. Physical examination, clinical score, and imaging examination are used to predict and evaluate the postoperative healing. Among them, physical examination and clinical score are non-invasive and the most economical methods, but their accuracy and sensitivity are lower than imaging examination, so they can only be used as auxiliary methods. The acromio-humeral distance (AHD) and upward migration index (UMI) measured by X-ray films can directly reflect the change of supraspinatus tendon thickness, but they are impossible to distinguish whether there is tear or not. Ultrasound and MRI are the main methods for the clinical diagnosis of supraspinatus tendon tear, but the commonly used MRI sequence can not accurately judge the internal healing of the tendon. Shear wave elastrography (SWE) and ultrashort-echo-time (UTE) techniques are the latest research directions in recent years, but different studies have shown opposite conclusions on the application of SWE technique. This conclusion shows that the principle of SWE technique and its relationship with tendons need to be further studied. UTE technique has good clinical effect, and the T2* value obtained by UTE technique is more accurate than that of traditional Sugaya typing, but there are still few research samples.

Conclusion

AHD and UMI measured by X-ray film and T2* value measured by UTE technique can be used as effective methods for evaluating the healing of supraspinatus tendon tear after repairing, and can be used as a follow-up evaluation method combined with physical examination and clinical score for patients with supraspinatus tendon tear.

Intra-operative assessment of the vascularisation of a cross section of the meniscus using near-infrared fluorescence imaging

PURPOSE

The purpose of this study was to assess whether the vascularisation of the meniscus could be visualised intra-operatively using near-infrared fluorescence (NIRF) imaging with indocyanine green (ICG) in patients undergoing total knee arthroplasty (TKA).

METHODS

The anterior horn (i.e., Cooper classification: zones C and D) of the meniscus that was least affected (i.e., least degenerative) was removed during TKA surgery in ten patients to obtain a cross section of the inside of the meniscus. Thereafter, 10 mg of ICG was injected intravenously, and vascularisation of the cross section of the meniscus was assessed using the Quest spectrum NIRF camera system. We calculated the percentage of patients in whom vascularisation was observed intra-operatively using NIRF imaging compared to immunohistochemistry.

RESULTS

Meniscal vascularisation using NIRF imaging was observed in six out of eight (75%) patients in whom vascularisation was demonstrated with immunohistochemistry. The median extent of vascularisation was 13% (interquartile range (IQR) 3-28%) using NIRF imaging and 15% (IQR 11-23%) using immunohistochemistry.

CONCLUSION

This study shows the potential of NIRF imaging to visualise vascularisation of the meniscus, as vascularisation was observed in six out of eight patients with histologically proven meniscal vascularisation.

LEVEL OF EVIDENCE

IV.

[Research progress of interfacial tissue engineering in rotator cuff repair]

Objective

To summarize the research progress of interfacial tissue engineering in rotator cuff repair.

Methods

The recent literature at home and abroad concerning interfacial tissue engineering in rotator cuff repair was analysed and summarized.

Results

Interfacial tissue engineering is to reconstruct complex and hierarchical interfacial tissues through a variety of methods to repair or regenerate damaged joints of different tissues. Interfacial tissue engineering in rotator cuff repair mainly includes seed cells, growth factors, biomaterials, oxygen concentration, and mechanical stimulation.

Conclusion

The best strategy for rotator cuff healing and regeneration requires not only the use of biomaterials with gradient changes, but also the combination of seed cells, growth factors, and specific culture conditions (such as oxygen concentration and mechanical stimulation). However, the clinical transformation of the relevant treatment is still a very slow process.