A Global View of Digital Replantation and Revascularization

Fingertip injuries and their reconstruction, focusing on nails

The fingertip is a complex anatomical structure that is frequently injured, especially in manual workers. Different classifications have been reported, considering injury orientation, level and geometry. To optimize treatment planning, the area of soft-tissue defect should be considered. Treatment aims to conserve as long a finger as possible, restore sensation (S3 + or more) and ensure a pleasant esthetic appearance. When amputation occurs, the best treatment is replantation when conditions allow. When this is not possible, the fingertip should be used as a composite graft or the nail complex can be grafted and soft tissue reconstructed, according to the preferred method. In defect without amputation or if the distal part of the finger is not present or not useful, many reconstructive techniques have been described. Depending on the injury, patient characteristics and requirements and the surgeon's skills and experience, the treatments vary from secondary healing to free flaps. In this paper, the various treatment options are described and discussed. Nowadays, considering most variables, the best treatment in fingertip injury is secondary healing with occlusive or non-occlusive dressing, even in case of bone exposure. This simple solution is able to restore a nearly normal fingertip with good sensation without further injuring the hand.

Success Rates of Finger Revascularization and Replantation

Background

Revascularization surgery has been reported to have a higher success rate than replantation due to sufficient venous return. However, in complex cases, success depends on a wide range of indications. This study aimed to investigate success rates in cohorts that included severe cases.

Methods

This single-center, noninterventional, retrospective cohort study included 292 patients (349 digits) who underwent revascularization or replantation at our institution between January 2000 and December 2022. Sex, age, smoking history, comorbidities, affected digit, amputation level, complete or incomplete amputation, type of fracture and mechanism, artery diameter, needle, vein anastomosis in the revascularization subgroup, vein grafting, warm ischemic time, and outcomes were investigated and compared between the revascularization and replantation subgroups of the distal and proximal amputation groups.

Results

In the distal amputation group, the arterial diameter in the revascularization subgroup was larger than that in the replantation subgroup (P < 0.05). In the proximal amputation group, the revascularization subgroup had a lower frequency of multiple amputations than the replantation subgroup (P < 0.05). Vein grafts were more frequently used in both revascularization subgroups than in the replantation subgroups (P < 0.05). However, the other injury severity indices were similar, and the success rates were not significantly different between the subgroups.

Conclusions

The revascularization success rate was similar to that of replantation. Vein anastomosis or vein grafting to the veins should be advocated for revascularization in severe cases where skin bridges may not have sufficient venous return.

Tamai zone -I and -II replantation versus reconstruction with local flaps: retrospective analysis for functional and cosmetic results

A retrospective study were presented to compare functional and cosmetic outcomes in relation to local flap reconstruction or fingertip replantation in cases of zones I and II amputation. Outcomes were evaluated using Semmens Weinstein monofilament, Weber DiskCriminator, total active motion (TAM) assessment and Michigan Hand Questionnaire after a 1-year follow-up.

Overview and management of complications after digital replantations

The main complications after digital replantation are discussed in this review article. These complications include vascular compromise, infection, partial necrosis, delayed union or nonunion, atrophy and so on. The countermeasures for these complications are reviewed and the authors' methods are also introduced and discussed.

Selection Bias in Avoiding Vein Graft in Replantation/Revascularization May Exist in Distal and Proximal Amputations, Respectively

No difference in the success rate has been reported between the vein graft and non-vein graft groups in replantation/revascularization. However, this depends on a wide range of indications in difficult cases. This study aimed to investigate the selection bias in avoiding vein grafts.

Methods

This is a single-center, noninterventional, retrospective cohort study comprising 229 patients (277 digits) who underwent replantation/revascularization between January 2000 and December 2020 at our institution. Sex, age, smoking history, comorbidities, affected side, level of amputation, complete or incomplete amputation, type of fracture and mechanism, diameter of the artery, needle, warm ischemic time, and results were investigated and compared between the subgroups with and without vein graft. Results were investigated between the subgroups with and without a vein graft in the distal and proximal groups.

Results

In the distal group, the mean arterial diameter of the vein graft subgroup was larger than that of the non-vein graft subgroup [0.7 (0.1) mm and 0.6 (0.2) mm, respectively, P < 0.05]. In the proximal group, the vein graft subgroup had higher severity than the non-vein graft subgroup (comminuted fracture, 31.1% versus 13.4%; and avulsion or crush amputation, 57.8% versus 37.1%, respectively, P < 0.05). However, the success rate was not significantly different between the aforementioned subgroups.

Conclusion

There was no significant difference between the vein graft and non-vein graft subgroups owing to the selection bias avoiding small arteries in the distal amputation and the absence of said bias in the proximal amputation.

On-skin biosensors for noninvasive monitoring of postoperative free flaps and replanted digits

Severe soft tissue defects and amputated digits are clinically common injuries. Primary treatments include surgical free flap transfer and digit replantation, but these can fail because of vascular compromise. Postoperative monitoring is therefore crucial for timely detection of vessel obstruction and survival of replanted digits and free flaps. However, current postoperative clinical monitoring methods are labor intensive and highly dependent on the experience of nurses and surgeons. Here, we developed on-skin biosensors for noninvasive and wireless postoperative monitoring based on pulse oximetry. The on-skin biosensor was made of polydimethylsiloxane with gradient cross-linking to create a self-adhesive and mechanically robust substrate that interfaces with skin. The substrate was shown to exhibit appropriate adhesion on one side for both high-fidelity measurements of the sensor and low risk of peeling injury to delicate tissues. The other side demonstrated mechanical integrity to facilitate flexible hybrid integration of the sensor. Validation studies using a model of vascular obstruction in rats demonstrated the effectiveness of the sensor in vivo. Clinical studies indicated that the on-skin biosensor was accurate and more responsive than current clinical monitoring methods in identifying microvascular conditions. Comparisons with existing monitoring techniques, including laser Doppler flowmetry and micro-lightguide spectrophotometry, further verified the sensor's accuracy and ability to identify both arterial and venous insufficiency. These findings suggest that this on-skin biosensor may improve postoperative outcomes in free flap and replanted digit surgeries by providing sensitive and unbiased data directly from the surgical site that can be remotely monitored.

Clinical application of an expanded reverse-island flap with two dorsal metacarpal arteries and dorsal metacarpal nerves in index- and middle-finger-degloving injury repair and amputation reconstruction

The dorsal metacarpal artery flap (DMAF) is irrefutable as an effective way of repairing long finger defects, and hand surgeons might consider using it for long finger reconstruction or degloved injury repair. Unfortunately, the DMAF containing a single dorsal metacarpal artery (DMA) hinders the treatment effect. The sensory restoration of long fingers and the reconstruction of phalangeal joints and tendon grafts are unsolved challenges as well. We reported our experience in reconstructing the index and middle finger by a reverse-island flap with two DMAs and dorsal metacarpal nerves (DMNs) with blood supply. We reviewed ten patients with finger-crush injuries affecting eight index fingers and two middle fingers. Degloving injuries occurred in two patients, and finger amputations occurred in eight others. Two patients received simple flap reconstruction, and eight received finger reconstruction, including seven from abandoned phalangeal joints and tendon grafts of the severed finger and one from the iliac crest bone graft. All patients underwent finger reconstruction by an expanded reverse-island flap consisting of two DMAs and DMNs up to a maximal size of 9 × 8 cm². Postoperative follow-up evaluation showed a satisfactory appearance and functional recovery of the reconstructed fingers. We posit that the expanded reverse-island flap involving two DMAs and DMNs constitutes a feasible and safe option for restoring a severely damaged index or middle finger, particularly for patients who are unwilling to undergo toe-to-finger transplantation to reconstruct the injured long fingers.

First clinical applications for the NIR-II imaging with ICG in microsurgery

In microsurgery, it is always difficult to accurately identify the blood supply with ease, such as vascular anastomosis, digit replantation, skin avulsion reconstruction and flap transplantation. Near-infrared window I (NIR-I, 700—900 nm) imaging has many clinical applications, whereas near-infrared window II (NIR-II, 1,000–1700 nm) imaging has emerged as a highly promising novel optical imaging modality and used in a few clinical fields recently, especially its penetration distance and noninvasive characteristics coincide with the needs of microsurgery. Therefore, a portable NIR-II imaging instrument and the Food and Drug Administration (FDA) approved indocyanine green (ICG) were used to improve the operation efficiency in microsurgery of 39 patients in this study. The anastomotic vessels and the salvaged distal limbs were clearly visualized after intravenous injection of ICG. The technique enabled identification of perforator vessels and estimation of perforator areas prior to the flap obtention and made it easier to monitor the prognosis. Overall, this study highlights the use of the portable NIR- II imaging with ICG as an operative evaluation tool can enhance the safety and accuracy of microsurgery.

Conventional versus fibrin-glue-augmented arterial microanastomosis: An experimental study

The purpose of this experimental study was to develop an alternative technique of arterial microanastomosis using only 2 stay-sutures augmented with fibrin glue, and to compare it to the conventional technique in arteries of varying diameters mimicking hand arteries. Eight anastomoses were performed in 7 male rats, including 1 anastomosis each on the 2 femoral, iliac, and carotid arteries, and 2 on the subrenal aorta. The conventional technique was used on one side and on the first aorta anastomosis, while augmented anastomoses were performed on the other side and on the second aorta. Patency was tested 10 min after unclamping; clamping time, blood loss, anastomosis quality score (out of 15 points) and artery diameter were recorded. In arteries of diameter 0.5-2.2 mm, augmented anastomoses were on average 10.7 ± 3.2 min faster to perform (p &lt; 0.0001), with an average of 1.3 ± 0.9 g less blood loss (p &lt; 0.0001) and an average of 2.6 ± 2.5 points higher quality score (p &lt; 0.0001). There were no significant differences between the two techniques in terms of patency rate, regardless of artery size. However, 3 of the 7 augmented anastomoses were non-permeable in the femoral subgroup (i.e., submillimetric arteries). This straightforward technique appears to be time-saving and reliable, provided that the repaired artery is of sufficient size. Subject to clinical validation, this technique might help surgeons treating extensive hand wounds with multiple severed neurovascular bundles.