孫孟帥 曹曉瑞 閆昭 朱錦宇 朱慶生
(第四軍醫(yī)大學(xué)西京醫(yī)院全軍骨科研究所關(guān)節(jié)外科,西安710032)
隨著材料學(xué)、假體制作工藝的進(jìn)步與革新、非骨水泥型髖關(guān)節(jié)假體在臨床的廣泛應(yīng)用以及患者年輕化,非骨水泥型膝關(guān)節(jié)假體再次成為臨床研究熱點(diǎn),大量文獻(xiàn)[1-3]回顧表明其臨床效果確切。全膝關(guān)節(jié)置換術(shù)(total knee arthroplasty,TKA)后假體無(wú)菌性松動(dòng)、假體周圍感染、骨溶解等并發(fā)癥是影響假體長(zhǎng)期生存率的常見(jiàn)原因。非骨水泥型髖關(guān)節(jié)假體憑借手術(shù)時(shí)間短、創(chuàng)傷小、出血少、松動(dòng)率低、易于翻修、避免骨水泥植入綜合征等優(yōu)點(diǎn),已逐漸取代傳統(tǒng)骨水泥假體主體地位,成為髖關(guān)節(jié)置換的首選[4]。行TKA的患者平均年齡在逐漸下降,到2030年需要行TKA的患者中<65歲所占比例將超過(guò)60%[5]。Carr等[6]統(tǒng)計(jì)發(fā)現(xiàn),行TKA患者年齡越小其術(shù)后翻修率越高,<55歲年齡組術(shù)后翻修率比>75歲年齡組增加5倍。因此,迫切需要生存率更高、性能更好且易于翻修的膝關(guān)節(jié)假體,以滿足對(duì)術(shù)后關(guān)節(jié)功能要求較高、預(yù)期壽命較長(zhǎng)的年輕患者[7]。
根據(jù)人工膝關(guān)節(jié)假體固定方式分為骨水泥固定型、非骨水泥固定型(生物型)及混合固定型膝關(guān)節(jié)假體。目前,骨水泥固定型膝關(guān)節(jié)假體被稱為TKA的“金標(biāo)準(zhǔn)”,廣泛應(yīng)用于臨床;骨水泥單體聚合膨脹滲透至骨小梁中,加固松質(zhì)骨,擴(kuò)大應(yīng)力傳導(dǎo)范圍,提高對(duì)醫(yī)師技術(shù)偏差和骨質(zhì)的容忍度。然而骨水泥型膝關(guān)節(jié)假體面臨諸多缺點(diǎn),如骨水泥單體毒性、組織熱損傷、骨水泥摩擦顆粒介導(dǎo)無(wú)菌松動(dòng)、骨水泥衰老退變等[8],使骨水泥型假體的長(zhǎng)期生存率受限。早期研發(fā)的非骨水泥型假體存在螺釘釘?shù)廊芙狻⒚劰瞧脚_(tái)松動(dòng)、髕骨假體失敗、聚乙烯襯墊磨損等問(wèn)題[2];目前,非骨水泥關(guān)節(jié)假體在關(guān)節(jié)置換領(lǐng)域應(yīng)用逐漸增多,在髖關(guān)節(jié)置換中已獲得滿意的長(zhǎng)期臨床應(yīng)用效果,骨水泥型髖關(guān)節(jié)假體作為補(bǔ)充多用于存在嚴(yán)重骨質(zhì)疏松、股骨髓腔為Dorr C型的患者,以獲得可靠的初始穩(wěn)定[9];非骨水泥假體在髖關(guān)節(jié)置換中的成功應(yīng)用為在膝關(guān)節(jié)置換中應(yīng)用提供了理論及實(shí)踐支持,非骨水泥型膝關(guān)節(jié)假體逐漸應(yīng)用于年齡較輕、骨質(zhì)較好的患者?;旌闲蛣t是根據(jù)兩種不同固定方式、假體特性,優(yōu)化關(guān)節(jié)假體組配以獲得較好的臨床效果。目前研究[9,10]顯示,混合型相對(duì)于完全骨水泥或非骨水泥型,效果相似或略有優(yōu)勢(shì)。非骨水泥型股骨假體與骨水泥型脛骨假體匹配的混合型膝關(guān)節(jié)置換在解決脛骨平臺(tái)螺釘釘?shù)拦侨芙?、股骨假體周圍骨水泥碎屑導(dǎo)致的三體磨損、骨水泥對(duì)周圍組織熱損傷等缺點(diǎn)方面獲得良好臨床效果[11,12]。骨水泥型股骨假體與鉭金屬骨小梁脛骨假體組配同樣獲得較高的假體長(zhǎng)期生存率[2,13]。骨水泥與非骨水泥型膝關(guān)節(jié)假體特性比較如表1所示。
早期非骨水泥型假體生存率低于骨水泥型[2,14],新一代非骨水泥型假體通過(guò)等離子噴射、高溫?zé)Y(jié)將羥基磷灰石、鈦金屬被覆到假體基體或通過(guò)化學(xué)氣相沉積技術(shù)使鉭原子沉積到網(wǎng)狀玻璃碳網(wǎng)中的碳結(jié)構(gòu)中制成鉭金屬骨小梁組件,使假體表面具有高摩擦系數(shù)、生物相容性、骨長(zhǎng)入誘導(dǎo)性。依靠較高的表面摩擦系數(shù)提高初始穩(wěn)定,通過(guò)誘導(dǎo)成骨細(xì)胞和間充質(zhì)細(xì)胞定植促進(jìn)骨長(zhǎng)入,從而實(shí)現(xiàn)假體長(zhǎng)期生物固定。
羥基磷灰石是人體骨組織的主要無(wú)機(jī)組成成分,表面經(jīng)羥基磷灰石處理的假體植入體內(nèi)后,解離出鈣和磷與骨組織結(jié)合形成化學(xué)鍵并誘導(dǎo)新的骨組織長(zhǎng)入后獲得長(zhǎng)期穩(wěn)定性[15]。研究[16]證實(shí),在髖關(guān)節(jié)假體周圍脫落的羥基磷灰石晶體顆粒直接介導(dǎo)骨溶解過(guò)程,并且顆粒越細(xì)其生物活性越高;隨著涂層溶解、吸收出現(xiàn)機(jī)械強(qiáng)度降低、假體微動(dòng),繼而引起下沉、松動(dòng),影響長(zhǎng)期穩(wěn)定性。鈦金屬涂層是將鈦金屬通過(guò)高溫?zé)Y(jié)和等離子噴涂技術(shù)在假體基體表面形成顆??紫稑?、珍珠孔隙樣或絲孔樣結(jié)構(gòu),通過(guò)誘導(dǎo)骨長(zhǎng)入增加關(guān)節(jié)假體表面與骨的接觸面積,避免假體—骨界面的應(yīng)力集中引起的應(yīng)力遮擋。其次,將鈦金屬涂層經(jīng)過(guò)納米化處理后改變其表面光滑而惰性的性狀,增加成骨細(xì)胞的附著、增殖誘導(dǎo)新骨形成[17]。鈦金屬涂層假體雖然在表面機(jī)械強(qiáng)度、耐腐蝕性及假體長(zhǎng)期穩(wěn)定性方面優(yōu)于羥基磷灰石涂層假體,但在植入早期,鈦金屬涂層在骨誘導(dǎo)功能方面稍遜羥基磷灰石涂層假體。臨床長(zhǎng)期觀察[18]發(fā)現(xiàn),與羥基磷灰石涂層相似,鈦涂層假體同樣存在涂層脫落而導(dǎo)致假體松動(dòng)現(xiàn)象。廣泛應(yīng)用于髖關(guān)節(jié)置換領(lǐng)域的β鈦合金(Ti6Al4V)雖然有生物相容性及力學(xué)性能較高等優(yōu)勢(shì),但其彈性模量高于骨骼,易發(fā)生應(yīng)力遮擋,且其組成成分Al、V對(duì)人體不利[19]。
表1 骨水泥與非骨水泥型膝關(guān)節(jié)假體特性比較
鉭金屬骨小梁假體依靠網(wǎng)狀表面、0.98的高摩擦系數(shù)獲得初始穩(wěn)定,避免了對(duì)效果不確切螺釘?shù)氖褂茫唤Y(jié)構(gòu)上與骨小梁相似—孔隙率為75%~80%、平均孔徑為547 μm,促進(jìn)骨長(zhǎng)入達(dá)到生物自鎖固定[20]。鉭金屬骨小梁假體生物相容性最佳、孔隙率最大、高摩擦系數(shù)、<5 mm間隙術(shù)后都能被填充、彈性模量與骨松質(zhì)相似更符合生物力學(xué)傳導(dǎo)特性、減少假體應(yīng)力遮擋,并且具有潛在抑菌作用等優(yōu)點(diǎn),能夠有效促進(jìn)骨組織長(zhǎng)入假體孔隙、防止假體松動(dòng)和下沉,從而提高假體的長(zhǎng)期生存率[21,22]。
假體無(wú)菌性松動(dòng)與聚乙烯襯墊、骨水泥、金屬假體磨損顆粒激活破骨細(xì)胞相關(guān)[23,24],當(dāng)磨損顆粒在每克組織內(nèi)的數(shù)量>1010個(gè)這一閾值時(shí),骨溶解極有可能被激活,假體周圍骨溶解吸收出現(xiàn)無(wú)菌性松動(dòng)[25]。羥基磷灰石涂層、鈦金屬涂層及鉭金屬骨小梁等非骨水泥型假體固定理念避免了因骨水泥老化、退變、碎裂、磨損及應(yīng)力遮擋而引起的骨溶解[13]。其次,目前膝關(guān)節(jié)假體襯墊材質(zhì)為超高分子量聚乙烯,可進(jìn)一步降低磨損顆粒的產(chǎn)生。股骨假體選用非骨水泥的混合型膝關(guān)節(jié)假體在避免非骨水泥假體脛骨假體系列問(wèn)題的同時(shí),也避免了骨水泥碎屑清除不徹底引起的三體磨損[10-12]。鉭金屬一體化脛骨平臺(tái)(tantalum monoblock tibial component,TMT)與傳統(tǒng)脛骨平臺(tái)托、聚乙烯襯墊組配安裝不同,是將襯墊直接壓縮連接到脛骨假體基板上,達(dá)到一體化設(shè)計(jì),較組配式減少了襯墊背面與脛骨假體之間的微動(dòng)磨損[25]。通過(guò)固定理念改變盡量減少或避免傳統(tǒng)骨水泥固定型假體磨損因素,減少磨損顆粒誘導(dǎo)的骨溶解骨吸收,提高假體長(zhǎng)期生存率。
假體周圍關(guān)節(jié)感染是關(guān)節(jié)置換術(shù)后災(zāi)難性并發(fā)癥,在TKA中發(fā)病率約為0.5%~2.0%,是術(shù)后翻修的重要原因。細(xì)菌定植于假體表面形成生物膜,造成難以控制的假體周圍關(guān)節(jié)感染,引起骨溶解、吸收。在假體表面存在著骨組織長(zhǎng)入和細(xì)菌定植的競(jìng)爭(zhēng)性抑制,因此,對(duì)假體表面進(jìn)行處理使其更利于自身骨組織長(zhǎng)入并通過(guò)競(jìng)爭(zhēng)性抑制作用抑制細(xì)菌在假體表面的定植、增殖[26]。促進(jìn)骨長(zhǎng)入是非骨水泥型假體的設(shè)計(jì)理念核心,假體界面粗糙化、納米化等設(shè)計(jì)誘導(dǎo)骨長(zhǎng)入同時(shí)降低了細(xì)菌定植風(fēng)險(xiǎn)[27];但有相關(guān)報(bào)道[28]顯示,雖然生物假體材料界面利于骨長(zhǎng)入,但也增加了細(xì)菌定植的風(fēng)險(xiǎn),感染仍不可避免,假體表面涂層抗菌化處理仍是最可靠方法;一項(xiàng)關(guān)于細(xì)菌在不同材料假體表面粘附性的研究發(fā)現(xiàn),最常見(jiàn)的金黃色葡萄球菌在純鉭表面粘附性較純鈦、鈦合金及不銹鋼等材料低。通過(guò)等離子植入、抗生素涂層、功能性抗菌集團(tuán)組裝使假體表面通過(guò)化學(xué)鍵、非化學(xué)鍵與抗菌活性物質(zhì)結(jié)合獲得抗菌活性,抑制細(xì)菌定植[27]。
盡管假體制作工藝和手術(shù)操作技術(shù)提高使假體生存率逐漸提高,但預(yù)計(jì)在2030年膝關(guān)節(jié)翻修率將達(dá)到14.5%[29]。假體取出困難、骨質(zhì)缺損是TKA術(shù)后翻修的常見(jiàn)難題,骨水泥在聚合過(guò)程中通過(guò)膨脹作用滲透到周圍骨松質(zhì)當(dāng)中,骨水泥取出時(shí)連帶大量骨組織增加骨缺損且常面臨取出困難。非骨水泥型假體理論上可獲得更好的長(zhǎng)期穩(wěn)定性和更高的長(zhǎng)期生存率,但這并不意味著非骨水泥型假體翻修時(shí)會(huì)增加假體取出難度;如TMT假體取出時(shí)利用震蕩鋸及高速磨鉆破壞骨假體界面,利用環(huán)鉆、骨刀取出鉭金屬角釘,可盡量減少金屬碎屑、保留骨量,幾乎無(wú)骨質(zhì)丟失并保存完整的骨床利于再次假體植入[30]。
Ritter等[14]對(duì)73例非骨水泥型膝關(guān)節(jié)假體進(jìn)行20年隨訪發(fā)現(xiàn),沒(méi)有螺釘固定的膝關(guān)節(jié)假體同樣獲得良好的關(guān)節(jié)功能,脛骨平臺(tái)假體20年生存率達(dá)96.8%,無(wú)股骨假體失敗病例。Lizaur等[31]對(duì)93例患者進(jìn)行隨機(jī)分組,股骨假體均為非骨水泥型,根據(jù)脛骨假體分為骨水泥組(48例)、非骨水泥組(45例),進(jìn)行平均6.7年(5~12年)隨訪發(fā)現(xiàn)骨水泥組存在4例脛骨假體松動(dòng),而非骨水泥組僅有1例脛骨假體出現(xiàn)松動(dòng),兩者并無(wú)統(tǒng)計(jì)學(xué)差異;但發(fā)現(xiàn)在膝關(guān)節(jié)臨床評(píng)分上非骨水泥組優(yōu)于骨水泥組。Nam等[32]觀察鈦金屬涂層假體與骨水泥假體兩組患者術(shù)后早期情況,均獲得較好的膝關(guān)節(jié)功能情況及患者滿意度,兩組膝關(guān)節(jié)假體均未出現(xiàn)早期失敗。Martino等[33]對(duì)2002年至2005年期間應(yīng)用TMT假體行TKA的33例(33膝)患者進(jìn)行>10年隨訪,僅考慮脛骨平臺(tái)有無(wú)無(wú)菌性松動(dòng)、骨溶解,關(guān)節(jié)假體的生存率為100%;截止到最后隨訪,無(wú)患者出現(xiàn)影像學(xué)上假體松動(dòng)、移位、應(yīng)力遮擋現(xiàn)象。Kamath等[34]對(duì)100例鉭金屬骨小梁假體與312例骨水泥假體進(jìn)行為期5年的前瞻性隨訪研究發(fā)現(xiàn),在手術(shù)時(shí)間上骨水泥組較非骨水泥組長(zhǎng),術(shù)中失血、圍術(shù)期并發(fā)癥及手術(shù)花費(fèi)無(wú)明顯差異;非骨水泥型假體未出現(xiàn)影像學(xué)透亮線,而骨水泥組部分假體周圍存在透亮線,推測(cè)生物型膝關(guān)節(jié)假體將表現(xiàn)出更高的生存率。對(duì)于體重對(duì)非骨水泥固定效果的影響,Lizaur等[35]開(kāi)展了一項(xiàng)前瞻性研究,肥胖組(BMⅠ≥30 kg/m2)與非肥胖組(BMⅠ<30 kg/m2)各171例,發(fā)現(xiàn)兩組假體7年穩(wěn)定性及臨床恢復(fù)效果無(wú)明顯差異,肥胖組間亦無(wú)明顯差異,但肥胖組圍術(shù)期相關(guān)并發(fā)癥相對(duì)較多。
目前,骨水泥型膝關(guān)節(jié)假體雖然仍是TKA的金標(biāo)準(zhǔn),然而,非骨水泥型膝關(guān)節(jié)假體尤其是鉭金屬骨小梁膝關(guān)節(jié)假體已獲得良好的早、中期臨床結(jié)果。雖然,骨質(zhì)疏松患者存在的早期假體移位、長(zhǎng)期骨長(zhǎng)入問(wèn)題使非骨水泥型膝關(guān)節(jié)假體的適用范圍仍然相對(duì)局限,以及目前許多關(guān)節(jié)外科醫(yī)師仍習(xí)慣于傳統(tǒng)骨水泥假體手術(shù),尤其在我國(guó)非骨水泥型膝關(guān)節(jié)假體開(kāi)展較少、假體費(fèi)用較高,其臨床應(yīng)用相對(duì)局限,但非骨水泥假體為醫(yī)師、患者提供了更多的選擇。非骨水泥型關(guān)節(jié)假體能夠避免應(yīng)用骨水泥的缺點(diǎn),同時(shí)具有誘導(dǎo)骨長(zhǎng)入、減少應(yīng)力遮擋,鉭金屬骨小梁假體還存在表面抑菌活性等優(yōu)點(diǎn),從而獲得更高的假體長(zhǎng)期生存率;且易于翻修并在最大程度上保存骨量,因此是預(yù)期壽命較長(zhǎng)、活動(dòng)量較大、骨質(zhì)較好的患者的最好選擇。
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