Streitparth F, Schöttle P, Schlichting K, Schell H, Fischbach F, Denecke T, Duda G N, Schröder R J
Department of Radiology, Klinik für Strahlenheilkunde, Humboldt University, Berlin, Germany.
Acta Radiol. 2009 Sep;50(7):765-74. doi: 10.1080/02841850902980272.
Biodegradable scaffolds have become an important option in the treatment of osteochondral defects. Therefore, accurate and reproducible monitoring of scaffold repair tissue is crucial.
To assess the feasibility of indirect magnetic resonance (MR) arthrography in determining the quality of osteochondral repair after scaffold implantation using an MR imaging (MRI) scoring and grading system with histology as reference.
Osteochondral defects created at ovine condylar facets were treated with either a commercial poly (DL-lactide-co-glycolide) (PLG) scaffold or a modified softer one (n=6/group; 87% and 55% of the elastic modulus of ovine subchondral bone, respectively). Empty defects at the contralateral condyle served as control group. A 1.5T MRI scan was performed after 6 months with proton density (PD)-weighted (w) fat-saturated (fs) fast spin-echo (FSE), T1-w two-dimensional (2D), and 3D fs gradient echo (GE) sequences 30 min after intravenous Gd-DTPA administration and passive joint movement. Two independent radiologists evaluated the repair tissue. The MR findings were correlated with histological findings.
MRI and histological grading correlated well (10/12 cases). The stiff-scaffold group showed significantly superior repair in comparison to the control group (P<0.05). The 3D fs GE sequence proved to be most valuable in evaluating morphologic status. Complete defect filling and integration, intact surface and isointense signal to the adjacent native cartilage, subchondral incorporation with bone marrow edema, and graft plug enhancement were associated with a good histological outcome. Histologically, we found a smooth fibrocartilaginous layer and osseous replacement of the scaffold. Incomplete cartilage repair and irregular subchondral structures on the MRI correlated histologically with fibrocartilage-like repair and subchondral sclerosis, due to substantial degradation of the scaffold.
Indirect MR arthrography is an accurate, noninvasive monitoring tool in the follow-up of scaffold implants. The MRI scoring and grading system allows reliable assessment of normal and pathological repair, with high correlation to histological findings.
可生物降解支架已成为治疗骨软骨缺损的重要选择。因此，对支架修复组织进行准确且可重复的监测至关重要。
以组织学为参考，使用磁共振成像（MRI）评分和分级系统，评估间接磁共振（MR）关节造影在确定支架植入后骨软骨修复质量方面的可行性。
在绵羊髁状突关节面制造骨软骨缺损，分别用商用聚（DL-丙交酯-共-乙交酯）（PLG）支架或改良的较软支架进行治疗（每组n = 6；弹性模量分别为绵羊软骨下骨的87%和55%）。对侧髁的空白缺损作为对照组。6个月后进行1.5T MRI扫描，静脉注射钆喷酸葡胺（Gd-DTPA）30分钟后，采用质子密度（PD）加权（w）脂肪抑制（fs）快速自旋回波（FSE）、T1加权二维（2D）和三维fs梯度回波（GE）序列，并进行被动关节活动。两名独立的放射科医生评估修复组织。将MR结果与组织学结果进行关联。
MRI和组织学分级相关性良好（12例中的10例）。与对照组相比，硬支架组显示出明显更好的修复效果（P<0.05）。三维fs GE序列在评估形态学状态方面被证明最有价值。完全缺损填充和整合、完整的表面以及与相邻天然软骨等信号强度、软骨下骨合并骨髓水肿和移植物栓增强与良好的组织学结果相关。组织学上，我们发现有一层光滑的纤维软骨层以及支架的骨替代。MRI上不完全的软骨修复和不规则的软骨下结构在组织学上与纤维软骨样修复和软骨下硬化相关，这是由于支架的大量降解所致。
间接MR关节造影是支架植入物随访中一种准确、无创的监测工具。MRI评分和分级系统能够可靠地评估正常和病理性修复，与组织学结果高度相关。
