Research On Digital Medicine Technology Aided Surgery For The Reconstruction Of Thumb And Finger Defects

Research backgroundDue to the rapid development of social economy, industry and agriculture,complicated hand, thumb and finger defects caused by high energy damage andaccidents have increased.While toe-to-hand transplantation has been widely practiced, the qualityand effect of the operation has become the greater issue. Although thetechnology has had a lot of innovation, there are also many problems andunknown factors that we need to explore and resolve. Microsurgery is aspecialist subject involving the application of methodology for solving theproblem of function and morphology. The operation scheme is generally basedon traditional manual measurement, visual estimate and developed by trial anderror. The quality and effect of the operation is also greatly influenced by thedoctors’ personal experience, habits and his other subjective inclinations and thinking; and due to the fact that the blood supply of the donor site is immenselyvaried, making accurate understanding of the situation impossiblepre-operatively, the operation therefore carries some extent of randomness,blindness and risk.Presently, thumb and fingers reconstruction technology in our country hasachieved outstanding recognition throughout the world. However we have yet toprovide solutions for the following problems:(1) The lack of accurateassessment for the operation; manual measurement and visual estimate lackaccuracy; scientific and standard methods have their blindness and risk.(2)Injury at the donor site is relatively serious.(3) The appearance of thereconstructed finger is not ideal.(4) The function of the reconstructed finger isnot satisfactory. Therefore, it is very difficult to promote this kind of operation,and this in turn is causing bottleneck problems for the development of thetechnology. Although many thumb and fingers reconstruction cases had beenreported, more than90%of the thumb and finger defects were not very wellreconstructed. The lack of direct quantitative standards for the purpose ofpreoperative evaluation, planning and design; the difficulty of preoperativephysician-patient communication; the unpredictability relating to donor siteblood supply anatomy; the challenges facing the surgeon in this kind of surgery;the low learning rate and long learning curve and other factors affect thepromotion of this kind of operation. As such, it is critical to establish clinicalstandards and criterion for such operations in order to ensure greater safety,greater functionality and normalcy in the reconstructed thumb or finger, as wellas reduce injury to the blood supply donor site.Presently, digital medicine technology is growing at a tremendous pace,especially the multi-splice spiral CT which is ideal for examining tiny blood vessels; computer-aided design and3D printing which is very helpful inorthopedic surgery for the design of operation scheme and resolving difficultproblems; the changing development of medical science by leaps and boundsbrings about various kinds of new technology for solving and bridging clinicalproblems.ObjectiveTherefore in this project, through the optimized CTA technology, images ofblood supply donor sites and of living bone tissues can be obtainedpre-operatively, the blood supply situation of the donor site can be betterunderstood, the difficulty and blindness due to vascular variation can beresolved, damage due to random (blind) anatomical selection of donor site canbe lessened and tissues around the donor site can also be preserved in greatermeasure. All the above factors contribute to the success rate of the operation andalso shorten actual operation time. The design of the surgery scheme for thumband finger reconstruction using computer-aided digital design offers the highestchance for success. Combining the digitally designed operation plan with the3Dprinting technology adds accuracy, precision and standardization to theprocedure. The database of blood supply donor site on the feet, as well as CTimages and digital operation schemes can be used to establish a platform for footdisease diagnosis and research. Through the means of digital virtual applicationcombined with the actual operation, thumb and finger reconstruction surgery canthus be promoted. Clinical standards and criterion for numerous cases of thumband finger reconstruction which are presently carried out individually, withdifferent modus operandi can also be established, thereby making the proceduresafer, more effective, as well as making the appearance and function of the reconstructed thumb and finger more natural and normal.Method:This study is divided into3partsPart1:1.Using the64slice dual source CT (SOMATOM Definition Flash, Siemens,Germany), both feet of the patients are scanned; the patient is laid in a supineposition, feet entering first, in quiet breathing condition. Area to be scanned:both ankles, up to5cm deep. Parameter of CT scan: adult100kV (child70kV),with130mAs as the criterion, using automatic dosage control technique (CAREDose4D); thickness0.5mm; Interlamellar spacing0.5mm; Matrix512X512;FOV (field of view)320m2; Time of scan: adult8-10sec (child5-8sec);Injection at mid elbow vein with non-ionic contrast medium (iodine370mgI/ml):adult120ml-140ml (child2ml/kg); Rate of injection: adult5ml/s,(child3ml/s);Use contact scan method: place the contact scan surface about5cm above theankle;15sec after injecting the contrast medium (child10sec) begin to scancontinuously, watch out for tibial artery image development in this area; whenthe tibial artery image develop at the most dense period, adult delay time8-10sec (child delay time5-8sec), begin the scan.2.Use CT image workstation to analyze bilateral foot axial images and MPR,MIP and VR (volume rendering), and evaluate the first dorsal metatarsal arterytype, the first dorsal metatarsal artery origin, course and anatomic relationship.Image evaluation standard: A+: Vascular displays clear, continuous, thick; A:Vascular displays light, discontinuous, slender or vascular portion displayed; B:Blood vessels do not display. Compare the3D reconstructed virtual bloodsupply vessels with the actual entity to explore whether the virtual structure canfully replace the actual entity, whether there are differences between the two, consider the advantages and limitations of both, and through multi-angle3Dimages, determine the3D relationship of adjacent tissues surrounding the bloodsupply donor sitePart2:Draft a simulated operation scheme in a virtual software environment accordingto the specific injury condition by using the computer-aided design plan for thethumb and finger reconstruction so as to obtain the highest optimal operationscheme. In this way, the operation problems that were previously experienced,such as inaccuracy due to manual measurement, lack of precise assessment,scientific and design shortcomings, etc, can be resolved.Before the operation, use the64slice dual source spiral CT to obtain the originalDICOM data of the patient’s injured finger, the same corresponding contralateralfinger and the toe of donor site; select suitable threshold value to obtain the3Dmodels for the reconstruction of the soft tissue, bone, joint and vascular bundles.Because the human hand and foot have the characteristic of symmetry,according to the measurement results, determine the operation scheme and afterthat, incorporate the model into the operation simulation system of virtualoperation; following that, use a virtual cutting tool or Boolean operation to cutthe healthy contralateral finger in virtual simulation, separate and create a mirrorimage. Use Move, Rotate, Rescale and other tools to move the finger position.The necessary overlap can be accurately matched and measured by comparingthe pre-injury defect size and shape. Again using the virtual cutting tool orBoolean operation and according to the comparison result of the virtualoperation, make the cut on the mirror image; the tissue which is cut out from themirror image will then be actual extent of injury on the injured finger. Accordingto the preoperatively obtained first dorsal metatarsal artery type, move along the superficial vein on the dorsal foot to create the virtual3D simulation for the lineof incision and then design the operation based on the revealed vascular pedicle.Similarly, according to the extent of vascular damage on the injured finger,measure the free tissue vascular length that will be required for transplant in theoperation. The preoperative digital-aided design on the3D virtual model and theactual data can then be used to guide clinical operation.Before operation, through the CT3D reconstruction technology, reconstruct themodel of the damage of the finger with the digitally simulated design donepreoperatively. Convert the simulated model to.stl format, through MakeWaresoftware convert to.x3g format, through MakerBot Replicator23D printer,print out the injured finger and the toe or tissue that is used for the repair, createthe model for the transplant or repair procedure. Before and during the operation,the model can be used for dealing with the specific and individual condition ofthe patient and also for precise pre-operation design and standard. The result is amore precise, standard operation, enabling the appearance and function of thereconstructed finger to be closer to normalPart3Clinically, according to different thumb and finger defects, with the help ofdigital medical technology, we can apply different surgical methods, such aspartial finger reconstruction, plastic reconstruction, total reconstruction, multipletoes transplant reconstruction, reconstruction with removed finger tissues, etc.The technology is also applicable for doing research studies.From1Dec2010to31Mar2014, there were79in-patient cases with differentthumb and finger defect in our orthopedic department. Every5of them weredivided into2groups randomly according to their time admitted to thedepartment. They are divided into digital medical reconstruction group and traditional reconstruction group. In the digital medical reconstruction group are47cases with57fingers, male29cases with39fingers, female18cases with18fingers, aged35.2±10.5. In the traditional reconstruction group are32caseswith32fingers, male22cases with22fingers, female10cases with10fingers,aged37.4±13.8.In digital medical assisted reconstruction group, the vascular type, course, anddonor site is obtained by using CTA and the required arteries and veins at thedonor site can be marked precisely. By using computer-aided design and3Dprintout, the shape, size and condition of cutaneous soft tissue of finger to bereconstructed can be projected precisely on the donor site. Based on the size ofthe donor site, it should be enlarged5-10%. Use the bone length in accordanceto the3D printout as the precise length to be cut in the donor site. The operationis performed with the assistance of CTA, computer-aided design and3Dtechnology. The traditional reconstruction group uses the traditional way ofoperation.Thumb defect:1. Degree I defect–choose distal big toe for reconstruction;Degree II defect–choose distal big toe or toe flap for reconstruction, Degree IIIdefect–choose toe flap or second toe for reconstruction.2. Thumb pulp defect–choose fibular pulp flap of the big toe for reconstruction.3. Skin avulsion of thefinger–choose distal big toe flap with the ungula for reconstruction.4. DegreeIV defect–choose fibular side of the rudder-like dorsal foot skin flap and thesecond metatarsus or use the second metatarsus with tendon flap forreconstruction.5. Degree V and VI–choose diamond-shaped dorsal foot skinflap and the metatarsal joint of the contralateral second toe or the second toewith metatarsophalangeal joints and tendon flap for reconstruction.Finger defects:1.2-4fingertip defect–choose the tip of the second toe for reconstruction.2.2-4distal finger defect–choose the second or the third distaltoe for reconstruction.3. Degree II-III defect–choose the second toe forreconstruction.4. Proximal finger defect–choose the second toe forreconstruction.5. Purely finger pulp defect with bone and tendon exposure–choose tibial toe pulp flap of the second toe.For purely thumb and finger joint defect choose the second toe composite tissuefor reconstruction.For de-pulping injury of five fingers of one hand, choose tibia pulp flap of thethird toe to repair the pulp defect of the thumb, fibular toe flap and dorsalis pedisflap of the second toe to repair little finger. Contralateral fibular skin flap of thebig toe and the second toe flap with dorsalis pedis to repair left forefinger andmiddle finger. Free lower medial leg fasciocutaneous flap and anterolateralfemoral skin flap of the bone to repair the wound of the donor site to save thetoes as much as possible and minimize damage.Results1. CT Angiography can display individualized and three-dimensional vision ofdonor tissue blood supply. It can help to display the vascular tissues fromdifferent angles, clearly display angio-architecture, blood course and arterialbifurcation of different parts and measure the length and diameter of the vesselsas necessary. It can help solve the problems and blindness caused by bloodvessel variations, reduce the injury on the donor site by blind dissection topreserve the tissue as much as possible. In this way, operation time is shortenedand success rate is increased.2. Under the virtual software condition, depending on the patient’s defect, thebest operative plan is available by computer assisted design and virtualoperation process. This can avoid problems arising from manual evaluation based on experience and from lack of preciseness and scientific design.3.3D printing technology builds the bridge between CTA three-dimensionaldigital image and specific individualized operation process. It can print skin andbone model similar to the finger to be reconstructed and mark precisely the sizeof skin and length of bone needed in the donor site to make the operation morestandard, and make the appearance and function of the reconstructed fingercloser to normal.4. In the digital medical technology group, all of79cases with89fingerssurvived,81of which healed in the first period. Three of them were slightlyinfected but healed after dressing change. Two of them had necrosis in part oftissue of tibia toe flap. By debriding necrotic tissue and shortening part of thetoe, they healed in the second period. One case showed signs of arterial danger8hours after transplantation of the second toe. Through operation method, arterythrombosis was discovered and after removing thrombosis and suturing, itsurvived. Two cases showed recurring signs of venous blockage after8hoursand24hours of the operation respectively. They survived by using chemicalleech therapy for draining of blood after3days. After the operation, all of79cases with89fingers were followed up for6to24months. The fitness rate ofdigital medical technology assisted group is96.5%while the fitness rate of thetraditional group is81.3%. Comparing the two operation methods using thechi-square test (x2=4.105, P=0.043), the difference is statistically significant,proving that the digital medical technology-aided operation design scheme isbetter than traditional one.Conclusion1. Pre-operatively, CTA help give the surgeon better understanding through thethree-dimensional display of blood course and type in the donor site and obtain individualized anatomical map. By marking the arteries and veins precisely onthe surface of the skin in the donor site, it can greatly help to reduce theblindness and risks in the operation, reduce injuries of the donor site and shortenoperation time. The traditional open-observation-operation mode has now beenchanged to observation-open-operation mode.2. By applying digital virtual operation design, the operation plan is moreeffective.3.3D printing enables the building of the model of the injured hand and finger,as well as the model of hand and finger to be reconstructed. These modelssimulate and cover the skin and bone of the donor site precisely, helping to cutthe donor site more precisely and making the reconstructed model more similarto the original ones. Moreover, it also helps to avoid unnecessary injury in donorsite, reduce complications of the operation and increase the effective rate as wellas survival rate. Therefore, a complete, standard and normalized operationmethod can be built and promoted.4. Virtual operation rehearsal, step-by-step, standardized, and vivid design andvirtual practice combined with operation explanation carried out pre-operativelyare advantageous for teaching and doctor-patient communication.5. According to the idea of translational medicine,the application of the digitalmedical technology is the effective solutions for the problems of the toe-to-handreconstruction,such as the donor foot morbidity,the appearance of thereconstructed fingers is not ideal and the funtions of the reconstructed fingerswere dissatisfied.