Objective. This study aims to describe biomechanical maturation process of repair tissue after cartilage repair with autologous chondrocyte implantation (ACI) at long-term follow-up. Design. After ACI, 40 patients underwent altogether 60 arthroscopic biomechanical measurements of the repair tissue at various time points during an up to 11-year follow-up period. Of these patients, 30 patients had full-thickness cartilage lesions and 10 had an osteochondritis dissecans (OCD) defect. The mean lesion area was 6.5 cm2 (SD 3.2). A relative indentation stiffness value for each individually measured lesion was calculated as a ratio of repair tissue and surrounding cartilage indentation value to enable interindividual comparison. Results. Repair tissue stiffness improved during approximately 5 years after surgery. Most of the increase in stiffness occurred during the first 2 years. The curvilinear correlation between relative stiffness values and the follow-up time was 0.31 (95% CI 0.07-0.52), P = 0.017. The interindividual variation of the stiffness was high. Lesion properties or demographic factors showed no significant correlation to biomechanical outcome. The overall postoperative average relative stiffness was 0.75 (SD 0.47). Conclusions. Our clinical study describes a biomechanical maturation process of cartilage repair that may continue even longer than expected. A substantial increase in tissue stiffness proceeds for the first two years postoperatively. Minor progression proceeds for even longer. In some repairs, the biomechanical result was equal to native cartilage, suggesting hyaline-type repair. The variation in biomechanical results suggests substantial inconsistency in the structural outcome following ACI.

中文翻译：

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自体软骨细胞植入后修复组织长期随访的生物力学变化。

客观的。本研究旨在描述自体软骨细胞植入（ACI）软骨修复后修复组织在长期随访中的生物力学成熟过程。设计。在 ACI 之后，在长达 11 年的随访期间，40 名患者在不同时间点总共接受了 60 次修复组织的关节镜生物力学测量。在这些患者中，30 名患者有全层软骨损伤，10 名有剥离性骨软骨炎 (OCD) 缺损。平均病变面积为 6.5 cm2 (SD 3.2)。每个单独测量的病变的相对压痕刚度值被计算为修复组织和周围软骨压痕值的比率，以实现个体间比较。结果。手术后约 5 年内修复组织硬度得到改善。刚度的大部分增加发生在前 2 年。相对刚度值与随访时间的曲线相关性为 0.31（95% CI 0.07-0.52），P = 0.017。刚度的个体差异很大。病变特性或人口统计学因素与生物力学结果没有显着相关性。总体术后平均相对刚度为 0.75 (SD 0.47)。结论。我们的临床研究描述了软骨修复的生物力学成熟过程，其持续时间可能比预期的更长。术后头两年组织硬度显着增加。次要进展会持续更长时间。在一些修复中，生物力学结果与天然软骨相同，表明是透明型修复。