The current concept of large-segment bone defect treatment is still to complete the replacement and fusion of bone tissue by means of autologous, allogeneic or artificial bone graft filling, that is, "bone-bone" interface fusion. The theory is deeply rooted, but the clinical effect is poor. A research team from research institutions such as Peking University Third Hospital used a custom-made 3D-printed titanium alloy porous implant to repair large-segment bone defects in a research work, realizing the patient's early limb function recovery and long-term "implant- Reliable fusion of the "bone" interface, with significantly improved efficacy.
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https://doi.org/10.1016/j.bioactmat.2021.03.030
This research work was supported by the National Key RD Program of the Ministry of Science and Technology of the People's Republic of China (2016YFB1101501).
block Traditional "bone-bone" fusion treatment concept
Store segmentelle knogledefekter på grund af traumer, infektion eller tumorresektion har altid været et udfordrende klinisk problem. Omkring 5 procent -10 procent af frakturerne oplever forsinket forening eller nonunion, og næsten alt segmentelt knogletab resulterer i manglende forening. På verdensplan udføres mere end 2,2 millioner knogletransplantationer årligt for at behandle knogledefekter inden for ortopædi, neurokirurgi og tandpleje.
Classical techniques for the treatment of large bone defects include the Ilizarov technique, the induction of bone regeneration through biofilms (Masquelet technique), autologous vascularized cortical bone grafting, and titanium mesh (filled with autologous or allogeneic bone) implantation techniques. The above treatments have their own characteristics depending on the technology, but they are essentially based on the concept of "bone-bone" fusion, that is, autologous bone, allogeneic bone or artificial bone is transplanted and filled in the defect area, and replaced by bone tissue repair. Complete the connection and fusion of the bones at both ends of the defect area.
Imidlertid viser klinisk praksis, at disse behandlinger ikke er ideelle og nogle gange endda upålidelige. Knogletransport gennem Ilizarov-proceduren tager typisk flere måneder at hele, hvor patienten ikke er i stand til at bevæge sig normalt. Denne metode er endnu mindre tilbøjelig til at blive brugt til behandling af multi-segmentelle skeletdefekter i rygsøjlen. Masquelet-teknikken og metoden med autolog vaskulariseret kortikal knogletransplantation hjælper med at forbedre knoglefusionen, men det er vanskeligt at opnå umiddelbar postoperativ stabilisering. På grund af behovet for en stor mængde allogen/autolog knogle som knogletransplantatmateriale er yderligere kirurgisk knoglefjernelse (såsom fjernelse af iliaca-knogle) ofte påkrævet. Metoden til at implantere titaniumnettet i knogledefektområdet giver bekvemmelighed for påføring af forskellige graftmaterialer til en vis grad, men dens fikseringseffekt er begrænset, og den har også manglerne ved let løsning, nedsynkning eller forskydning. Faktisk er teknikker som Ilizarov og Masquelet også vanskelige at anvende på visse dissociationssteder, såsom metafysen.
To sum up, various traditional techniques based on the concept and theory of "bone-bone" fusion have many shortcomings or defects in the treatment of large segmental bone defects: the treatment process is long, and the limbs of patients after surgery are not immediately, early, or surgically removed. After a long period of time can not bear weight.
blok 3D-printer porøse titaniumimplantater
"Implant-bone" interface fusion
Sammenlignet med de ovennævnte-metoder, der kræver en stor mængde allogen/autolog knoglefyldning, synes anvendelsen af 3D-printede porøse titanlegeringsimplantater til at reparere og rekonstruere knogledefekter at have indlysende fordele. For det første kan implantaterne tilpasses præcist efter formen på knogledefekten uden behov for knogletransplantation; desuden, ifølge fordelene ved metalproteser, kan en fikseringsanordning designes til at opnå øjeblikkelig stabilisering mellem implantatet og tilstødende knogler, så patienten kan komme tidligt ud af sengen efter operationen; Porøse strukturelle træk, der tiltrækker tilstødende knoglevæv til at vokse ind i det, og endelig opnå permanent fusion af implantatets-knoglegrænseflade.
Figur 1. Radiologisk og biomekanisk analyse af 3D-printede porøse Ti6A14V-implantater for at rekonstruere en 4 cm femoral defekt. (A) Røntgenbilleder 1, 3 og 6 måneder efter implantation (i-iii) Computertomografibilleder 1, 3 og 6 måneder efter implantation (iv-vi) . Blå pile angiver nydannet knogle på defektstedet eller på implantatets ydre overflade. (vii) Radiologisk score for hver gruppe. (n=4) (B) MicroCT 3D-rekonstruktionsbilleder (i-iii) af gruppe 1, 3 og 6 måneder efter ofring (grå angiver titanlegering, grøn angiver ny knogle). (iv) Kvantitative resultater af knoglevolumenfraktion i peri-implantat- og i-foram-regionerne i hver gruppe (n=4).
Den kliniske terapeutiske effekt af at bruge 3D-printede porøse implantater til at reparere knogledefekter (især store-segmentknogledefekter) kræver ikke kun bekræftelse af observationsresultaterne fra opfølgningstilfælde, men også resultater af relevante dyreforsøg som bevis. Til dette formål gennemførte forskerteamet en-dybdegående og systematisk udforskning og forskning.
Figure 2. Biomechanical analysis of 3D printed porous Ti6A14V implants for reconstruction of 4 cm femoral defects. (A) Three-point flexural strength of each group of samples (n = 4) (B) Stress distribution of the "implant-bone" complex at (ii) 1000 N, (iv) 2000 N and (vi) 3000 N. Displacement distribution of the "implant-bone" complex at (i) 1000N, (iii) 2000N and (v) 3000N. (p<0.01,><>
In view of the shortcomings of the traditional "bone-bone" fusion method in the treatment of large-segment bone defects, and based on the experience of exploratory treatment of large-segment bone defects and the results of relevant animal experiments, the research team proposed a new large-segment bone defect. The technology and concept of bone defect repair and reconstruction: "implant-bone" interface fusion.
Figure 3. Histological analysis of 3D-printed porous Ti6A14V implants for reconstruction and repair of 4 cm long femoral defects. (A) Goldner's trichrome staining (i-iii) of 1, 3 and 6 month groups. (iv) Quantitative results of implant-bone growth and implant-bone contact rates in the three groups. (v) The ratio of mineralized bone to osteoid in each group (n = 10). (B) Fluorescent labeling of new bone around the implant and in the pores. (White arrows indicate titanium columns, green and yellow bands indicate calcein- and tetracycline-labeled new bone, respectively). (i) Osseointegration around the implant in the 1-, (iii) 3- and (v) 6-month groups. (ii) 1-, (iv) 3-, (vi) osseointegration in plant pores in 6-month groups.
The basic idea is: a. The 3D printed porous titanium alloy prosthesis is implanted into the bone defect area, and the two ends of the implanted prosthesis are connected and fixed with the adjacent host bone, so as to realize the immediate (or early) functional recovery of the patient's limb; b . The implanted prosthesis is designed as a porous structure to attract adjacent bone tissue to grow into it and surround it to achieve "implant-bone" interface fusion.
Figure 4. 3D printing of porous Ti6Al4V implants to reconstruct spinal bone defects (case 1). (A) (i-vi) 1 month (i), 3 months (ii), 7 (months iii), 12 months (iv), 24 months (v) and 32 (vi) postoperatively "Implant-bone" X-ray image of Moon. Blue arrows indicate the implant-bone interface or new bone on the outer surface of the implant. (B) CT images at 3 months (i), 7 months (ii), 12 months (iii), 28 months (iv), 32 months (v) and 36 months (vi) after surgery. Blue arrows indicate the implant-bone interface or newly formed bone on the outside of the implant.
Of course, if the porous structure of the implant grows through the bone tissue, it is ideal to form a "bone-bone" fusion, but it is difficult to become a reality. However, when the two ends of the implant prosthesis are effectively fused with the host bone at a distance of several millimeters, it can already meet the needs of the patient to restore the motor function of the limb. The research team applied the 3D-printed porous titanium alloy implants made by electron beam melting (EBM) technology to the clinical treatment of a group of large-segment bone defects, and achieved better than expected results. At the same time, the research team used the small-tailed Han sheep to create a long-segment femoral defect model to study the osseointegration characteristics of this method, and to provide a supporting basis for the treatment effect of clinical cases.
Figur 5. 3D-printet porøst Ti6Al4V-implantat til at rekonstruere femoral defekt (tilfælde 2). X af den rekonstruerede 11 cm lårbensdefekt umiddelbart efter den sidste operation (A) og 2 (B), 5 måneder (C), 8 måneder (D), 14 måneder (E) og 20 måneder (F) efter implantationslinjebillede. Blå pile indikerer osseointegration mellem implantat og værtsknogle.
Figure 6. 3D-printed porous Ti6Al4V implant to reconstruct pelvic bone defect (case 3). Photographs of the actual "implant-bone" complex specimen taken from (A) lateral and (B) anteroposterior views. The location of the "implant-bone" interface area indicated by the blue arrow (C) Histological image of the "implant-bone" interface, showing new bone growing into the porous implant pores. Micro-CT images of the "implant-bone" contact area in (D) midsagittal plane, (E) coronal plane and (F) transverse plane.
In this study, the research team successfully treated large segmental bone defects caused by various etiologies by 3D printing porous titanium alloy implants without using autologous/allogeneic bone grafts or any osteoinductive agents. immediate and long-term biomechanical stability. Animal experiments have shown that bone can grow into the pores to a certain extent and gradually remodel, so that the "implant-bone" complex can achieve long-term mechanical stability. In addition, this study also proposes a new "implant-bone" interface fusion concept for the treatment of large segmental bone defects, which is different from the traditional "bone-bone" fusion concept.
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