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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Povezani istraživački radovi objavljeni u časopisu Bioactive Materials
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
Veliki defekti segmentnih kostiju zbog traume, infekcije ili resekcije tumora oduvijek su bili izazovan klinički problem. Oko 5 posto -10 posto prijeloma ima odgođeno spajanje ili nezarastanje, a gotovo sav segmentni gubitak kosti rezultira nezarastanjem. U cijelom svijetu godišnje se radi više od 2,2 milijuna koštanih transplantata za liječenje koštanih defekata u ortopediji, neurokirurgiji i stomatologiji.
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.
Međutim, klinička praksa pokazuje da ti tretmani nisu idealni, a ponekad čak i nepouzdani. Prijevoz kostiju kroz Ilizarov postupak obično traje nekoliko mjeseci da se zacijeli, a za to vrijeme pacijent se ne može normalno kretati. Još je manje vjerojatno da će se ova metoda koristiti za liječenje više-segmentnih skeletnih defekata kralježnice. Masquelet tehnika i metoda autolognog vaskulariziranog kortikalnog presađivanja kosti pomažu u poboljšanju koštane fuzije, ali je teško postići neposrednu postoperativnu stabilizaciju. Zbog potrebe za velikom količinom alogene/autologne kosti kao materijala koštanog presatka, često je potrebno dodatno kirurško uklanjanje kosti (kao što je uklanjanje ilijačne kosti). Metoda ugradnje titanske mreže u područje koštanog defekta u određenoj je mjeri pogodna za primjenu različitih graft materijala, ali je njezin fiksacijski učinak ograničen, a ima i nedostatke lakog labavljenja, slijeganja ili pomicanja. Zapravo, tehnike kao što su Ilizarov i Masquelet također je teško primijeniti na određenim mjestima disocijacije, kao što je metafiza.
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 ispisuje implantate od poroznog titana
"Implant-bone" interface fusion
U usporedbi s gore-spomenutim metodama koje zahtijevaju veliku količinu alogenog/autolognog punjenja kosti, čini se da primjena 3D-ispisanih implantata od porozne legure titana za popravak i rekonstrukciju koštanih defekata ima očite prednosti. Prvo, implantati se mogu precizno prilagoditi prema obliku koštanog defekta, bez potrebe za koštanim graftom; osim toga, u skladu s prednostima metalne proteze, uređaj za fiksiranje može biti dizajniran za postizanje trenutne stabilizacije između implantata i susjednih kostiju, tako da pacijent može ustati iz kreveta rano nakon operacije; Porozne strukturne značajke, privlačeći susjedno koštano tkivo da urastu u njega i konačno postižu trajnu fuziju sučelja kostiju implantata-.
Slika 1. Radiološka i biomehanička analiza 3D tiskanih poroznih implantata Ti6A14V za rekonstrukciju femoralnog defekta od 4 cm. (A) X-slike 1, 3 i 6 mjeseci nakon implantacije (i-iii) Slike kompjuterizirane tomografije 1, 3 i 6 mjeseci nakon implantacije (iv-vi) . Plave strelice označavaju novoformiranu kost na mjestu defekta ili na vanjskoj površini implantata. (vii) Radiološki rezultat svake skupine. (n=4) (B) MicroCT 3D slike rekonstrukcije (i-iii) skupina 1, 3 i 6 mjeseci nakon žrtvovanja (siva označava leguru titana, zelena označava novu kost). (iv) Kvantitativni rezultati volumne frakcije kosti u peri-implantatu i u-foram regijama svake skupine (n=4).
Međutim, klinički terapeutski učinak upotrebe 3D ispisanih poroznih implantata za popravak koštanih defekata (osobito defekta velikih-segmenata kostiju) zahtijeva ne samo potvrdu rezultata promatranja praćenih-slučajeva, već i rezultati relevantnih pokusnih studija na životinjama kao dokaz. U tu svrhu, istraživački je tim proveo-dubina i sustavna istraživanja i istraživanja.
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.
Slika 5. 3D-ispisani porozni implantat Ti6Al4V za rekonstrukciju femoralnog defekta (slučaj 2). X rekonstruiranog femoralnog defekta od 11 cm neposredno nakon zadnje operacije (A) i 2 (B), 5 mjeseci (C), 8 mjeseci (D), 14 mjeseci (E) i 20 mjeseci (F) nakon slike linije implantacije. Plave strelice označavaju oseointegraciju između implantata i kosti domaćina.
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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