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To preoperatively plan skin incision in the case of the first Dutch bilateral hand-arm transplantation.
A bilateral hand-arm transplantation has been performed for the first time in the Netherlands in 2019. In the context of preparation for this surgical procedure, the optimal patient-specific skin flap was determined. Skin flaps should be properly matched between donor and recipient to ensure sufficient tissue for the approximation of skin over the tendon anastomosis, adequate distal tip perfusion, and esthetics.
Preoperatively, stereophotogrammetry was obtained from the upper extremities of the patient and a volunteer with similar body physique. Skin flap dimensions were determined for each extremity, which resulted in patient-specific incision patterns. Combining this digital information yielded practical skin incision guides for both the donor and acceptor arms. Finally, the computer-aided designs were 3D printed.
The 3D prints were convenient to utilize in both shaping the donor flaps as in preparing the acceptor extremities, taking only a few seconds during precious ischemia time. There was sufficient skin flap perfusion, and the wound-healing followed an uncomplicated course. No corrections were made to the initial skin incisions.
Three-dimensional printed templates were successfully utilized in the first Dutch bilateral hand-arm transplantation. We believe its usage increased time efficiency, improved the match of skin flaps in donor and recipient arms, and allowed us to control the amount of skin surplus without skin flap tip necrosis. In these procedures where time is of the essence, we believe preoperative planning is imperative for its success.
Until 2019, this complex procedure had not yet been performed in the Netherlands. However, after the presentation of a suitable recipient candidate for a bilateral hand-arm transplantation, a multidisciplinary platform was installed in Radboudumc (Nijmegen, the Netherlands) to facilitate this procedure. Our patient was a highly motivated and physically strong 44-year-old, who suffered severe sepsis in 2014. She developed acute kidney failure and diffuse intravascular coagulation and required amputation of both legs below the knee; her left hand was at the radiocarpal level and her dominant right hand was at the metacarpal level due to necrosis. She recovered well with the restoration of her kidney function.
Preoperative preparation is imperative for success of the procedure. During the 18-month waiting period for a suitable donor, the surgical team prepared the procedure extensively and practiced cadaveric graft procurement and replantation. Ischemia times should be kept to a minimum to improve patient outcome. Therefore, an extensive protocol with a predefined order of operative steps was developed to ensure all involved healthcare professionals achieved maximum surgical efficiency while patient safety was maintained.
Among these steps is the marking of skin flap incisions. Although seemingly simple, the proper planning of skin flaps is imperative for postoperative success. Skin flaps should be properly matched between donor and recipient to ensure sufficient tissue for the approximation of skin over the often bulky tendon anastomoses, adequate distal tip perfusion should be ensured, and esthetics should also be kept in mind by placing the incisions at the right location. Failure to do so could lead to insufficient skin surplus, which requires full-thickness skin grafts. Furthermore, our patient has seen examples (on the internet) with bulky adaptation of skin at the transplantation site and requested us to prevent bulky transitions of the soft tissues from transplant to recipient arm if possible. To facilitate this, one patient-specific and one generic donor 3D-printed skin incision guide was created per arm.
In this article, we describe the process of creating 3D-printed skin incision guides for both donor and acceptor, utilizing readily available methods of imaging and printing available in most academic hospitals nowadays. These created 3D-printed guides were successfully used during the first Dutch bilateral hand-arm transplantation.
Materials and methods
Obtaining 3D information
Three-dimensional stereophotogrammetry (3dMD Body 5-pod set-up, Atlanta, USA) was used to capture a 3D image of both forearms of the patient (Figure 1). To design a generic donor template, both arms of a healthy volunteer with similar body physique to the patient were photographed to act as a 3D design baseline. Informed consent of the patient, healthy volunteer, and approval from the medical ethical committee and institutional review board were obtained.
Design of the skin flaps
A unique V-shaped incision pattern was created per arm using the computer-aided design software FreeCAD (open-source). Based on magnetic resonance imaging and clinical findings, the amputation level of the recipient arms was determined preoperatively taking fibrous/scar tissue and vascularization of the recipient arms into account. Healthy skin was present at 6 and 4 cm from the wrist crease on the left and right sides, respectively. However, to anticipate for postoperative swelling due to edema, the donor incision patterns were created with a 4-cm margin: a decision based on clinical assessment in the dissecting theater during practice sessions. This resulted in incisions at 10 cm from the left wrist and 8 cm from the right wrist crease. A horizontal groove was incorporated in the 3D-planned design to be placed over the patient's wrist crease, allowing for visual placement and confirmation prior to marking. Finally, the angle of the skin flaps was set at 80° to ensure proper tip perfusion.
Creation of 3D skin incision template
The 3D template for the recipient was created by loading the 3D photo into the Meshmixer (Autodesk, San Rafael, USA) where the imported data were cleaned up to form a hollow 3D shell (mesh) of the forearm. The obtained mesh of the arm was duplicated, where one mesh remains textured with the skin, which served for visual inspection during the creation of the template. The other, duplicate mesh was enlarged (extraction, direction of normals, and 3 mm) to form the base of the 3D print; a 3-mm-thick solid shell following the original contours of the arm. By importing and overlaying the previously designed incision pattern onto the mesh, a Boolean intersection operation with the enlarged shell resulted in an imprinted incision pattern into the 3-mm solid shell. Text for side verification is added, the mesh is split horizontally, and hinges were added to be able to clamp the template around the arm, which aided the operator in correct placement (Figure 2: arms B and C).
The donor template was created in a similar way. However, the donor physique remains unknown until a match is found and the surgical procedure is initiated. Immediate adjustment and printing of the 3D model to the specific donor is logistically challenging. Therefore, the template was designed to be flexible in both width and height, while the correct skin incision length was maintained. Instead of a hinged design, four plastic rings and rods guided the top and bottom halves of the mold to ensure correct placement and allow for body physique differences (Figure 2; arms A and D).
Two different colors were used during printing to easily identify either side of the incision templates. For the left side of the donor and acceptor, a dark blue color was chosen; where the right hand-arm was, apart from the imprinted text, also recognizable by a light blue color. It is of note that the designed hinges worked immediately after printing, owing to minor spacing between leaf, pin, and knuckle of the hinge. During quality control after printing, it was ensured that no sharp edges or mechanically weak components were present in the 3D print.
The patient-specific 3D-printed skin incision templates were test-fitted on the patient during a routine outpatient clinic visit. On both arms, the 3D print fitted snugly, and no alternations to the 3D-planned design had to be made. The open design allowed to visualize the majority of the skin, which is important to verify correct placement over the extremity.
In complex procedures such as a bilateral hand transplantation, an extensive preoperative plan is important for fluent intraoperative progress. The surgeons reported that the 3D models were self-explanatory and convenient in their usage. The text imprinted in the 3D template was used for side verification, the hinged design allowed for quick placement over the recipient arms, and the donor templates sliding design provided sufficient room for correct template positioning (Figure 3). Because of the use of 3D printed skin incision guides, only seconds of precious surgery time was spent on skin marking, and the markings were directly placed in the correct anatomical positions that minimize ischemia time. There was an appropriate closure of skin on both sides without the need to make any adjustments to the initial skin incisions. Postoperatively, the wound healing followed an uncomplicated course. Figure 4 shows the 12-month follow-up photos without any tissue surplus. In total, the costs of the four high-quality 3D prints were below 200 euros.
In this manuscript, we showed how 3D technology can improve a complex procedure. Although skin markings are only a minor part of a surgical procedure, it is of high importance with regard to wound closure and final appearance. In training sessions, many discussions were held on the exact skin incisions; therefore, needing a safe and nondebatable marking of the incisions. By combining stereophotogrammetry, computer-aided design, and 3D printing, we were able to standardize one critical step in the extensive process of a bilateral hand-arm transplantation at very little cost.
3D printing and 3D stereophotogrammetry are increasingly utilized during surgical procedures and find their way toward allotransplantation. This form of reconstruction is extensively planned due to its complexity ideally suited for the adaptation of these techniques. During the case of the first pediatric bilateral hand-arm transplantation, Momeni et al. and Gálvez et al. describe how 3D-printed hand-arms facilitated the decision-making with regard to the appropriateness of donor limb dimensions and were useful in preoperative patients and parent education. Furthermore, prosthetic hands were created to restore the donor's physique.
In these modern day times, departments that are less experienced in 3D technology could initiate similar 3D modeling reasonably easily. In cases where no 3D-stereophotogrammetry system or 3D-scanner is available, one could resort to the use of a CT or MRI scan to obtain the outer shell through the computer segmentation of the skin. The soft tissue of the lower arm should not be compressed during positioning into the imaging modality, e.g., by fixating only upper arms mid-air in the gantry.
The modeling software as presented in this manuscript is available to download free of charge, and tutorials on how to interact with 3D models is readily available online. However, one must be mindful that these licenses of the proposed software and possibly the 3D print are not intended for medical usage. Consultation with the industrial 3D printing facility is recommended to ensure that the material and finish are suitable for intended use. If one wishes to sterilize the 3D print for intraoperative usage, consultation with the central sterilization department is necessary to warrant an adequate level of hygiene. Be attentive of jagged edges that remain from the printing process as these may harm the patient and can lead to an inadequate sterilization process. After production of the 3D models, it is imperative that the responsible healthcare provider measures and verifies that the printed object has the correct virtually planned intended dimensions.
The field of plastic surgery continues to evolve, which stretches the limits to obtain the best patient care. The reconstructive ladder has another tread added to its total length in the form of vascularized composite tissue transplantation. The number of procedures following this form of reconstruction is annually increasing. Because of the complex nature of the procedure, it is imperative for patient safety and procedural success that each surgical step is contemplated upon. We demonstrated how the latest technical opportunities available have been deployed into clinical practice in the form of skin-flap incision guides and aspire other surgical allotransplantation teams to consider elaborating on this step during their preoperative planning.
Conflict of Interest: None.
Hand and upper extremity transplantation: an update of outcomes in the worldwide experience.