Abstract
Objective
To report preoperative planning using 3D printing to plan thumb reconstructions with second toe transplant.
Methods
Between December 2013 and October 2015, the thumbs of five patients with grade 3 thumb defects were reconstructed using a wrap‐around flap and second toe transplant aided by 3D printing technology. CT scans of hands and feet were analyzed using Boholo surgical simulator software (www.boholo.com). This allowed for the creation of a mirror image of the healthy thumb using the uninjured thumb. Using 3D images of the reconstructed thumb, a model of the big toe and the second toe was created to understand the dimensions of the donor site. This model was also used to repair the donor site defect by designing appropriate iliac bone and superficial circumflex iliac artery flaps. The polylactic acid model of the donor toes and reconstructed thumb was produced using 3D printing. Surgically, the wrap‐around flap of the first dorsal metatarsal artery and vein combined with the joint and bone of the second toe was based upon the model donor site. Sensation was reconstructed by anastomosing the dorsal nerve of the foot and the plantar digital nerve of the great toe. Patients commenced exercises 2 weeks after surgery.
Results
All reconstructed thumbs survived, although partial flap necrosis occurred in one case. This was managed with regular dressing changes. Patients were followed up for 3–15 months. The lengths of the reconstructed thumbs are 34–49 mm. The widths of the thumb nail beds are 16–19 mm, and the thickness of the digital pulp is 16–20 mm. The thumb opposition function was 0–1.5 cm; the extension angle was 5°–20° (mean, 16°), and the angle of flexion was 38°–55° (mean, 47°). Two‐point discrimination was 9–11 mm (mean, 9.6 mm). The reconstructed thumbs had good appearance, function and sensation. Based on the criteria set forth by the Standard on Approval of Reconstructed Thumb and Finger Functional Assessment of the Chinese Medical Association, the results were considered excellent for four cases and good for one case. The success rate was 100%.
Conclusions
When planning a wrap‐around flap and second toe transplant to reconstruct a thumb, both the donor and recipient sites can be modeled using 3D printing. This can shorten the operative time by supplying digital and accurate schematics for the operation. It can also optimize the function and appearance of the reconstructed thumb while minimizing damage to the donor site.
Keywords: 3D printing technology, Second toe, Thumb reconstruction, Wrap‐around flap
Introduction
The thumb accounts for 40% of the total function of the hand and 80% of the activity needed for holding1. Anthropologists have determined that the hands of humans are different from the hands of subhumans, because humans have three main actions, including lateral pinching, kneading with three fingers and griping with five fingers. The main actions depend on the thumb to complete them2. With thumb defects from the level of the interphalangeal joint, the basic function of the thumb can be retained, but the appearance and accurate movement can be affected. As a result, the thumb defect should be repaired by dissociating toe transplant and reconstruction. The main points for thumb reconstruction are feeling, opposing thumb function and appearance. The first element of thumb opposing function is to recover the length of the thumb. However, the main problem is determining how to recover feeling, function, and appearance of the reconstructed thumb and how to accurately measure the length of the reconstructed thumb.
The loss of a thumb can cause a critical deficit in hand function. For more than half a century, toe transplantation has been considered the best method for surgical thumb or finger reconstruction3. For third‐degree thumb defects, awrap‐around flap combined with the second toe is widely used in thumb reconstructions4. Conventionally, the postoperative function, sensation, and appearance of the thumb following reconstruction are directly dependent on the clinical experience of the surgeon. However, using the traditional method of surgery, many surgeons arbitrarily cut bone without utilizing any precise templates. The weaknesses of traditional operations include the following. First, cuts are made arbitrarily with no comparison. Second, there is higher chance of injury to the donor site of feet and the degree of emphasis on the donor site is not great enough. Third, without precise preoperative design, operations can be longer and risks are greater during surgery. Finally, with no template, patients cannot obtain a clear understanding of the surgery and the postoperative effects.
In recent years, 3D printing has been widely used in medical applications5. The first 3D printer was developed in the 1980s. However, the high cost of 3D printers initally placed them out of reach of many researchers. Now, lower‐cost printers are available to a much wider field. Surgeons can use 3D printing to produce bones, plan surgical procedures and repair or replace bones. 3D printing technology can not only help surgeons to design better preoperative operation plans and enable patients to have more intuitive understanding of the operation process, but also significantly shorten operation times, reduce the difficulty of operations, and lead to better therapeutic outcomes. At present, a frequently mentioned problem is precise treatment in clinical work. Thus, increasing the ability to provide precise treatment for surgery plays an important role in the field of surgical operation. 3D printing technology can be used as a guide for surgery, for preoperative simulation, and even to forecast postoperative clinical effects. It can help clinical doctors by enabling more accurate preoperative design for thumb reconstruction. The main purpose of this study is, first, to consider how the use of 3D printing can standardize thumb reconstruction surgery, and enable surgical procedures to be performed more accurately, and eliminate adverse factors during surgery that are associated with the subjective experience of surgeons. 3D printing technology can significantly shorten operation times and reduce the difficulty of operations. Furthermore, the use of 3D printing technology enables patients to better understand the whole operational process. In addition, to recover the function, feeling and appearance of thumbs, we use 3D printing technology to plan a wrap‐around flap combined with the second toe for third‐degree thumb defects.
Between December 2013 and October 2015, we used 3D printing to plan thumb bone and joint reconstructions for five patients who had third‐degree defects. All reconstructions achieved good clinical results. We report on our experiences managing these patients.
Materials and Methods
Inclusion and Exclusion Criteria
Inclusion criteria (Patients presenting with all of the following criteria were considered for study inclusion): (i) the metacarpophalangeal joint (MP) of thumb's stump was good; (ii) period of thumb defect was between 3 months and 2 years; (iii) third‐degree thumb defects. Exclusion criteria (patients with one or more of the following conditions were excluded from this study): (i) chronic osteomyelitis, synovitis, tuberculosis of bone and joint, and diabetes; (ii) injury to the first carpometacarpal joint of the injured thumb; and (iii) injury to the thumbs of both hands.
General Information
We treated five cases of third‐degree thumb defects. Third‐degree thumb defects (according to Gu YD)1 included: IIIa: beyond the middle of proximal phalanx is lost (one case); and IIIb: beyond the basilar part proximal phalanx is lost (four cases). Reasons for injury: machine crush injury in two cases; heavy crush injury in two cases; and rotated and avulsed injury in one case. Four patients were male and one was female. Their mean age was 28 years (range, 16–45 years). The right thumb was involved in three cases, and the left thumb in two cases. There were four case of injury of the dominant side, and one case of the non‐dominant side.
The causes of the thumb amputations were crush injuries from machines in two cases, crush injuries from heavy objects in two cases, and a rotating tear injury in one case. In addition to their defects (Fig. 1), three patients had thumb stumps combined with moderate stenosis of the first web (Table 1). Prior to surgery, we requested that these patients perform functional rehabilitation exercises with their thumb stumps, such as bending from 35° to 45°, stretching from 15° to 25°, extending from 80° to 90° and rotating 360°. The main exercise is the function of opposing thumb 2 h a day in 3 months. This study was approved by the Human Research Ethics Committee of Xijing Hospital, Fourth Military Medical University. Written informed consent was obtained from all patients.
Figure 1.
Preoperative appearance and 3D CT image of a 30‐year‐old male patient with right third‐degree thumb defects (IIIb).
Table 1.
Patient information
| Case | Age (years) | Degree of thumb defect | Defect of the first web | Length of required thumb (mm) | Width of healthy nail (mm) | Thickness of healthy digital pulp (mm) |
|---|---|---|---|---|---|---|
| 1 | 23 | IIIa | No | 35 | 17 | 16 |
| 2 | 16 | IIIb | Yes | 44 | 15 | 15 |
| 3 | 27 | IIIb | Yes | 40 | 18 | 18 |
| 4 | 45 | IIIb | No | 39 | 18 | 14 |
| 5 | 30 | IIIb | No | 49 | 20 | 18 |
3D Reconstruction and Printing of the Thumb and Toe
To model the bone and joint of the thumb, patients’ injured and healthy hands and feet were scanned using a 64‐row helical CT machine with 0.625‐mm slice thickness. The scan data was output according to the Digital Imaging and Communication in Medicine standard format, and burned onto a CD. CT data were read using Boholo surgical simulator software (Boholo Medical Science, Shanghai, China), and then a 3D image of the patient's injured thumb was rebuilt. The thumb defect was reconstructed using mirroring technology to compare the digitized analog and cut bone to create a 3D image of the thumb stump. The donor toe was then added to the 3D image, recreating the projected outcome and comparing it with a 3D image of the injured thumbs to simulate and confirm the dimensions of the great toe and second toe donor site. This information was then used to recreate a 3D image of the bone and joint of the thumb (Fig. 2A,B). We then 3D‐printed a polylactic acid (PLA) model of the bone and joint of the injured thumb and the second toe donor site (Fig. 2C–F).
Figure 2.
Preoperative digital simulation and the 3D printed model. (A) Bottle green is the required length of the reconstructed thumb; (B) 3D digital model of the donor foot; (C, D) polylactic acid model of hand and foot; and (E, F) the required length of the reconstructed thumb is 49.84 mm by the use of 3D printing technology.
Surgical Technique
The patients were operated upon while under general anesthesia. We used a curved incision to cut the dorsal foot (Fig. 3). This exposed the first dorsal metatarsal artery, vein, and dorsal nerve, allowing us to proximally dissociate them over the required length of the vascular pedicle. We separated the first dorsal metatarsal artery to the fork of the first plantar metatarsal artery to confirm a normal blood supply to the lateral aspect of the big toe and the medial aspect of the second toe6. The wrap‐around flap was raised based upon the dimensions of the 3D printed donor toe. The interphalangeal joint of the second toe and bone of the big toe under its nail bed were used as donors7. The wrap‐around flap and interphalangeal joint of the second toe were completely dissociated. We then relaxed the tourniquet to confirm that the blood supply to the transplant was adequate (Fig. 4A,B). A new thumb was created using the bone and interphalangeal joint of the second toe and wrapped around the flap using a “nesting” approach (Fig. 4C). Based on the preoperative 3D design, the created thumb was transferred to the recipient site, and then placed into abduction and pronation. The transplant was then fixed with Kirschner wires (Fig. 4D). After confirming adequate fracture fixation according to X‐rays, we repaired the flexor digitorum profundus and flexor digitorum longus tendons. The first dorsal metatarsal artery, saphenous vein and dorsal cutaneous nerve of the foot were connected with the dorsal carpal branch of the radial artery, the cephalic vein, and the superficial radial nerve of the hand, respectfully. The plantar nerves in the wrap‐around flap were anastomosed with the nerves of the thumb stump to complete the thumb reconstruction. An iliac bone and iliac artery flap were used to rebuild the donor site. The iliac bone flap was placed on the second toe and fixed with a Kirschner wire. The pedicle of the flap was anastomosed with the first dorsal metatarsal artery and the saphenous vein.
Figure 3.
Preoperative donor site planning. The required length of the cutting second toe should be 49.84 mm.
Figure 4.
Intraoperative images of toe harvesting and assembly of the flap construct. (A) Free flap for repairing the donor area; (B) cutting the wrap‐around flap and joints from the second toe; (C) compound flap from the great toe and joints from the second toe; and (D) appearance of reconstructed thumb.
Postoperative Treatment
Routine postoperative treatment included anticoagulation, anti‐spasmodics, antibiotics, and detumescence. The circulation of the flap and reconstructed thumb was observed closely during the perioperative period. The temperature of the patients’ rooms was maintained at 25 °C and the injured limbs were elevated. Sutures were removed 2 weeks after surgery. Partial rehabilitation activities were permitted 3 weeks after surgery. Final X‐rays were obtained 6 weeks after reconstruction, at which time full rehabilitation activities were permitted.
Results
The five thumb reconstructions were all succesful. After 3–15 months of follow‐up (Table 2, Figs 5, 6, 7), we found that all patients were satisfied with the appearance of their thumb, which also recovered good function. Function of opposing thumb was 0–1.5 cm, the angle of extension was 5°–20° (mean, 16°), and the angle of flexion was 38°–55° (mean, 47°). Two‐point discrimination was 9–11 mm for all patients (mean, 9.6 mm).
Table 2.
Post‐surgical outcomes of five thumb reconstructions
| Case | Age (years) | Time of operation (h) | Length of reconstructed thumb (mm) | Width of nail (mm) | Thickness of digital pulp (mm) | Satisfaction |
|---|---|---|---|---|---|---|
| 1 | 23 | 6.1 | 34 | 16 | 18 | Excellent |
| 2 | 16 | 6.6 | 45 | 16 | 18 | Excellent |
| 3 | 27 | 6.0 | 40 | 19 | 20 | Excellent |
| 4 | 45 | 7.0 | 38 | 17 | 16 | Good |
| 5 | 30 | 6.9 | 48 | 19.5 | 19 | Excellent |
Figure 5.
Images of the reconstructed thumb 6 months after surgery, compared with the healthy thumb.
Figure 6.
Clinical images of the reconstructed thumb and foot 12 months after surgery, compared with the contralateral thumb. (A) The width of the reconstructed thumb nail bed is 19.5 mm. The healthy thumb is 20 mm; (B) the thickness of the reconstructed digital pulp is 19 mm. The healthy thumb is 18 mm and (C) the length of the reconstructed thumb is 48 mm. (D) Appearance of repaired donor area.
Figure 7.
Postoperative X‐ray imaging of reconstructed thumb: X‐ray taken postoperatively revealed healed bones. Metacarpophalangeal joint and interphalangeal joint is good and close to the healthy thumb.
Postoperative Data and Appearance of the Reconstructed Thumb
The required length of the reconstructed thumb was 35–49 mm. The width of the healthy thumb nail beds was 15–20 mm, and the thickness of healthy digital pulp was 14–18 mm. During surgery, the length of the bone and joint of second toes was 25–40 mm and the length of the bone of the big toe was 10 mm. According to the 3D simulation data, we modified the length of the cutting bone and joint. After surgery, the length of the reconstructed thumbs was 34–48 mm. The width of the thumb nail bed was 16–19.5 mm, the thickness of the digital pulp was 16–20 mm, and the operation time was 6–7 h. The reconstructed thumbs had good appearance, function, and sensation, and were close in these respects to the healthy thumbs.
Functional Assessment Standard
The function and appearance of the reconstructed thumbs were graded according to the Standard on Approval of Reconstructed Thumb and Finger Functional Assessment of the Chinese Medical Association8: four were deemed excellent and one good, resulting in a success rate of 100% (Tables 2 and 3).
Table 3.
Post‐surgical functioning of five thumb reconstructions
| Case | Age (years) | Gilbert's classification of FDMA | Function of thumb opposing (cm) | Mobility of MP (angle of extension and flexion) | Two‐point discrimination (mm) | Condition of using hand |
|---|---|---|---|---|---|---|
| 1 | 23 | Ia | 0.9 (<1.0) | Extension 30°, flexion 55° | 9 | Excellent |
| 2 | 16 | Ib | 1.5 (1.0–2.0) | Extension 25°, flexion 50° | 9 | Excellent |
| 3 | 27 | IIa | 0.8 (<1.0) | Extension 10°, flexion 46° | 10 | Good |
| 4 | 45 | IIb | 0.0 (<1.0) | Extension 5°, flexion 48° | 11 | Good |
| 5 | 30 | IIb | 1.1 (1.0–2.0) | Extension 11°, flexion 38° | 9 | Good |
FDMA, first dorsal metatarsal artery; MP, metacarpophalangeal.
Postoperative Complications
After surgery, there was no vascular crisis in any of the five cases. The five reconstructed thumbs all survived. Partial flap necrosis was noted in one case. The patient returned for dressing changes.
Discussion
In 1966, Yang et al. began to establish the basis for toe‐to‐thumb reconstructions, particularly focusing on removing the second toe to reconstruct the thumb. Since then, the surgical techniques for this reconstruction have been continuously improved9. These advances include Cobbett designing the toe transplantation in 196910 and Morrison designing the wrap‐around flap transplantation in 198011. In 1984, Yu et al. demonstrated the ability to wrap a flap around the second toe to reconstruct the thumb. This advance improved the cosmesis and function of the reconstructed thumb12. Wrapping the flap around the second toe became one of the best ways to reconstruct the thumb because the donor sites were both supplied by the first dorsal metatarsal artery, and, therefore, required only one vascular pedicle anastomosis.
Using digital surgical procedures and operative simulation with 3D printing13, it is possible to accurately model the results of a reconstructive surgery. Our study showed that using 3D printing to print a model of the bone and joint is a good choice for achieving individualized and detailed thumb reconstructions.
Reconstructing the bone and joint of the thumb using 3D printing greatly improves the efficiency and outcomes of the procedure. Traditionally, the surgeon plans thumb reconstructions using subjective observations and rough measurements made prior to the surgery. Surgeons design their grafts based roughly on the required length of donor bone necessary. This increases the risk of a mismatch between the healthy thumb and the position and length of the reconstructed thumb. Combining CT scan data of the patients’ hands and feet with 3D printing and preoperative surgical simulations, we were able to use the structure of the healthy thumb to recreate a 3D model of the donor bone and joint needed to accurately recreate the injured thumb. Based on the 3D models we created of the second toes, we printed out new models of the bones and joints of the reconstructed thumb. Our goal was to match each part of the length and angle of the bones, especially in the wrap‐around flap, second toe, and ilium components. 3D printing enabled our operations to be performed smoothly, and allowed us to create reconstructed thumbs that were as similar as possible to their pre‐injury forms. Furthermore, preoperative simulation allowed us to assemble and fix each part of the bone and joint only once without repeated comparisons, thereby shortening the total surgical and tourniquet time. This not only reduced the difficulties of thumb reconstruction, but also increased patient satisfaction. The average operative time for thumb reconstruction is 6.0–7.0 h, with conventional surgical methods taking at least 8 h14. The average operative time for Gilbert's classification of first dorsal metatarsal artery (FDMA) types Ia and Ib was reported to be 6.35 h, with 6.63 h for types IIa and IIb; these are the most common FDMA types, and no cases of type III were previously identified in the five patients15. 3D printing technology can reduce operating times, although the experience of the surgeon is more important for a good outcome.
Until now, the intraoperative use of 3D printing technology in thumb reconstruction has been rarely reported16. Using 3D printing technology, the compound flap from the great toe and vascularized joints from the second toe can be used to obtain better clinical effects in posttraumatic thumb reconstruction17. As healthy skin is rich in elastic fibers, it possesses great flexibility without the malleable characteristics of printing material. Xu et al. report that 3D printing technology for thumb reconstructions is limited because of biomechanical mismatches18. The PLA material printed by our 3D technology is also dissimilar to human skin, so it is not possible to directly translate our simulation into the actual surgical procedure. However, modeling the bone and joint using PLA constructs has several advantages. It can improve the accuracy of surgical planning and reduce operative time. Although the cost of preoperative examinations increases, preoperative 3D simulative design and high‐precision individualized surgical planning has resulted in improved patient satisfaction with the function and appearance of their reconstructed thumb. With the continual improvement and development of 3D printing technology, we anticipate that 3D printing technology will play an increasingly important role in hand reconstruction surgery.
Disclosure: The authors have no conflicts of interest to declare.
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