Feasibility of Bone Perfusion Evaluation in Cadavers Using Indocyanine Green Fluorescence Angiography

Does indocyanine green fluorescence angiography impact the intraoperative choice of procedure in free vascularized medial femoral condyle grafting for scaphoid nonunions?

Background

Free vascularized medial femoral condyle (MFC) bone grafts can lead to increased vascularity of the proximal pole and restore scaphoid architecture in scaphoid nonunions. The intraoperative perfusion assessment of the bone graft is challenging because the conventional clinical examination is difficult. Indocyanine green (ICG) angiography has previously been shown to provide a real-time intraoperative evaluation of soft tissue perfusion in reconstructive surgery. The present study investigated the utility of ICG angiography in patients treated with a free medial femoral condyle graft for scaphoid nonunions.

Methods

We performed a retrospective analysis of patients with scaphoid nonunions, in which ICG angiography was used intraoperatively for perfusion assessment. The medical records, radiographs, intraoperative imaging, and operative reports of all patients were reviewed. Intraoperative ICG dye was administered intravenously, and laser angiography was performed to assess bone perfusion. The scaphoid union was examined using postoperative CT scans.

Results

Two patients had documented osteonecrosis of the proximal pole at the time of surgery. Four patients received a nonvascularized prior bone graft procedure, and a prior spongiosa graft procedure was performed in one patient. The mean time from injury to the MFC bone graft surgery was 52.7 months, and the mean time from prior failed surgery was 10.4 months. Perfusion of the vascular pedicle of the MFC and the periosteum could be detected in all patients. In two patients, even perfusion of the cancellous bone could be demonstrated by ICG angiography. Following transplantation of the bone graft, patency of the vascular anastomosis and perfusion of the periost were confirmed by ICG angiography in the assessed cases. No additional surgery regarding a salvage procedure for a scaphoid nonunion advanced collapse was necessary for the further course.

Conclusion

ICG-angiography has shown to be a promising tool in the treatment of scaphoid nonunion with medial femoral condyle bone grafts. It enables intraoperative decision making by assessment of the microvascular blood supply of the periosteum and the vascular pedicle of the MFC bone graft. Further studies need to evaluate the impact on union rates in a long-term follow-up.

Near-Infrared Fluorescence with Indocyanine Green to Assess Bone Perfusion: A Systematic Review

Background: Adequate perfusion of a bone flap is essential for successful reconstruction of osseous defects. Unfortunately, complications related to inadequate bone perfusion are common. Near-infrared fluorescence (NIRF) imaging enables intraoperative visualization of perfusion. NIRF has been investigated in reconstructive surgery to aid the surgeon in clinical perioperative assessment of soft tissue perfusion. However, little is known on the beneficial use of NIRF to assess bone perfusion. Therefore, the aim of this review was to search for studies evaluating NIRF to assess bone perfusion. Methods: A systematic review, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline, was performed. Studies up to October 2021 were included. We extracted data regarding the study population, size and design, reported objective fluorescence parameters and the methodology used for fluorescence imaging and processing. Results: Ten articles were included. Studies reported unevenly on the protocol used for NIRF imaging. Five studies reported objective parameters. Absolute and relative perfusion parameters and parameters derived from maximum fluorescence were reported. The clinical significance of these parameters has not been evaluated in humans. Conclusion: The evidence on bone perfusion as measured with NIRF is limited. More clinical studies are required.

Indocyanine Green Fluorescence Angiography of the Transverse Cervical Arterial Supply to Clavicle Flaps: An Anatomical Study

OBJECTIVE

To describe the anatomy of the transverse cervical artery and to prove its perfusion to the clavicle using indocyanine green fluorescence angiography as an alternative vascularized bone for head and neck reconstruction.

STUDY DESIGN

Cadaveric dissection.

SETTING

Anatomy lab.

METHODS

Twenty-two necks and shoulders from 11 fresh-frozen cadavers were dissected. The transverse cervical artery diameter, length, emerging point, and the length of clavicle segment harvested were described. Photographic and near-infrared video recordings of the bone's medial and longitudinal cut surfaces were taken prior to, during, and after indocyanine green injection.

RESULTS

The transverse cervical artery originated from the thyrocervical trunk and emerged at the level of the medial one-third of the clavicle in 22 of 22 (100%) specimens. The average length of the pedicle was 3.6 cm (range, 2.2-4.4 cm), and the mean diameter was 2.5 mm (range, 1.8-3.4 mm). The harvested bone had a mean length of 5.1 cm (range, 4.3-5.8 cm). After injecting the indocyanine green, 22 of 22 (100%) specimens showed enhancement in the periosteum, bony cortex, and medulla.

CONCLUSION

The middle third of the clavicle can be reliably harvested as a vascularized bone with its perfusion solely from the transverse cervical artery pedicle, as shown by the near-infrared fluorescence imaging. The pedicle was sizable and constant in origin.

Comparison of photoacoustic and fluorescence tomography for the in vivo imaging of ICG-labelled liposomes in the medullary cavity in mice

Few reports quantitatively compare the performance of photoacoustic tomography (PAT) versus fluorescence molecular tomography (FMT) in vivo. We compared both modalities for the detection of signals from injected ICG liposomes in the tibial medullary space of 10 BALB/c mice in vivo and ex vivo. Signals significantly correlated between modalities (R² = 0.69) and within each modality in vivo versus ex vivo (PAT: R² = 0.70, FMT: R² = 0.76). Phantom studies showed that signals at 4 mm depth are detected down to 3.3 ng ICG by PAT and 33 ng by FMT, with a nominal spatial resolution below 0.5 mm in PAT and limited to 1 mm in FMT. Our study demonstrates comparable in vivo sensitivity, but superior ex vivo sensitivity and in vivo resolution for our ICG liposomes of the VevoLAZR versus the FMT2500. PAT provides a useful new tool for the high-resolution imaging of bone marrow signals, for example for monitoring drug delivery.

Multi-Wavelength Fluorescence in Image-Guided Surgery, Clinical Feasibility and Future Perspectives

With the rise of fluorescence-guided surgery, it has become evident that different types of fluorescence signals can provide value in the surgical setting. Hereby a different range of targets have been pursued in a great variety of surgical indications. One of the future challenges lies in combining complementary fluorescent readouts during one and the same surgical procedure, so-called multi-wavelength fluorescence guidance. In this review we summarize the current clinical state-of-the-art in multi-wavelength fluorescence guidance, basic technical concepts, possible future extensions of existing clinical indications and impact that the technology can bring to clinical care.