Abstract：
BACKGROUND: As life expectancy has improved, the potential number of revision candidates is also expected to increase among patients who have undergone a total knee arthroplasty (TKA). The longevity of modern posterior stabilized knee prostheses after 20 years of use has not been well documented, especially in Asian populations that require a deeper flexion range due to a floor-based lifestyle.
OBJECTIVE: Firstly, the implant longevity regarding mechanical failures such as aseptic loosening and polyethylene (PE) wear would vary over a longer follow-up depending on the age groups; and secondly there would be unique risk factors for revision surgery in an Asian TKA cohort.
METHODS: We conducted this age-stratified survival analysis in a consecutive series of 368 NexGen Legacy Posterior Stabilized (LPS) TKAs performed by a single surgeon. These cases were divided into four age groups (< 60 years, early 60s, late 60s, and ≥ 70 years). The implant longevity against aseptic mechanical failures was calculated using the Kaplan-Meier method. The revision surgery risk was evaluated using postoperative factors including a deep flexion capability (> 135̊), and postoperative mechanical alignments.
RESULTS: Overall survivorship was significantly lower in the youngest groups than other groups (Log-rank test, p=0.001). The cumulative 20-year implant longevity was more than 95% in the two oldest groups, but less than 60% in the youngest group. It was notable that the post-TKA implant longevity was not apparent up to 10 years between the age groups (p=0.073∼0.458). Aseptic loosening was observed with an earlier onset (3.1 to 18.9 years) trend than PE wear (9.8∼17.9 years), with most cases arising in the youngest groups. Flexion limitation and varus alignment were significant risks to aseptic loosening and PE wear (Cox proportional hazard regression: p=0.001 and 0.045, respectively).
CONCLUSIONS: A younger age (< 60 years), inability of postoperative deep flexion, and varus alignment were significant risk factors for aseptic loosening and PE wear after modern PS design in this Asian cohort. The difference in postoperative longevity affected by these factors was not obvious during the first 10 years but emerged over a second decade.
METHODS: III; retrospective cohort study.
OBJECTIVE: Firstly, the implant longevity regarding mechanical failures such as aseptic loosening and polyethylene (PE) wear would vary over a longer follow-up depending on the age groups; and secondly there would be unique risk factors for revision surgery in an Asian TKA cohort.
METHODS: We conducted this age-stratified survival analysis in a consecutive series of 368 NexGen Legacy Posterior Stabilized (LPS) TKAs performed by a single surgeon. These cases were divided into four age groups (< 60 years, early 60s, late 60s, and ≥ 70 years). The implant longevity against aseptic mechanical failures was calculated using the Kaplan-Meier method. The revision surgery risk was evaluated using postoperative factors including a deep flexion capability (> 135̊), and postoperative mechanical alignments.
RESULTS: Overall survivorship was significantly lower in the youngest groups than other groups (Log-rank test, p=0.001). The cumulative 20-year implant longevity was more than 95% in the two oldest groups, but less than 60% in the youngest group. It was notable that the post-TKA implant longevity was not apparent up to 10 years between the age groups (p=0.073∼0.458). Aseptic loosening was observed with an earlier onset (3.1 to 18.9 years) trend than PE wear (9.8∼17.9 years), with most cases arising in the youngest groups. Flexion limitation and varus alignment were significant risks to aseptic loosening and PE wear (Cox proportional hazard regression: p=0.001 and 0.045, respectively).
CONCLUSIONS: A younger age (< 60 years), inability of postoperative deep flexion, and varus alignment were significant risk factors for aseptic loosening and PE wear after modern PS design in this Asian cohort. The difference in postoperative longevity affected by these factors was not obvious during the first 10 years but emerged over a second decade.
METHODS: III; retrospective cohort study.
摘要：
背景：随着预期寿命的提高，在接受全膝关节置换术(TKA)的患者中,翻修候选的潜在数量预计也会增加.现代后稳定型膝关节假体使用20年后的寿命还没有得到很好的证明,特别是在亚洲人群中，由于以地板为基础的生活方式，需要更深的屈曲范围。
目的：(1)在长期随访中，无菌性松动和聚乙烯(PE)磨损等机械故障的植入物寿命会有所不同，具体取决于年龄组；(2)在亚洲TKA队列中，翻修手术有独特的风险因素。
方法：我们在由一名外科医生进行的368例NexGenLegacy后路稳定（LPS）TKAs的连续系列中进行了年龄分层生存分析。这些病例分为四个年龄组(<60岁，60年代早期,60年代末,且≥70岁)。使用Kaplan-Meier方法计算针对无菌机械故障的植入物寿命。使用术后因素评估翻修手术风险，包括深屈曲能力（>135°），和术后机械对齐。
结果：最年轻组的总生存率明显低于其他组（Log-rank检验，P=0.001)。在两个最古老的组中，累计20年的植入物寿命超过95％。但在最年轻的组中不到60%。值得注意的是，TKA植入后的寿命在10岁以下年龄组之间并不明显（P=0.073~0.458）。观察到无菌性松动的发病时间（3.1至18.9年）比PE磨损（9.8〜17.9年）更早。大多数病例出现在最年轻的群体中。屈伸限制和内翻对准是无菌性松动和PE磨损的显着风险（Cox比例风险回归：分别为P=0.001和0.045）。
结论：年龄较小（<60岁），术后深屈曲无力，在该亚洲队列中，采用现代PS设计后，内翻对准是无菌性松动和PE磨损的重要危险因素。受这些因素影响的术后寿命差异在最初的10年中并不明显，但在第二个十年中出现了。
方法：III；回顾性队列研究。
目的：(1)在长期随访中，无菌性松动和聚乙烯(PE)磨损等机械故障的植入物寿命会有所不同，具体取决于年龄组；(2)在亚洲TKA队列中，翻修手术有独特的风险因素。
方法：我们在由一名外科医生进行的368例NexGenLegacy后路稳定（LPS）TKAs的连续系列中进行了年龄分层生存分析。这些病例分为四个年龄组(<60岁，60年代早期,60年代末,且≥70岁)。使用Kaplan-Meier方法计算针对无菌机械故障的植入物寿命。使用术后因素评估翻修手术风险，包括深屈曲能力（>135°），和术后机械对齐。
结果：最年轻组的总生存率明显低于其他组（Log-rank检验，P=0.001)。在两个最古老的组中，累计20年的植入物寿命超过95％。但在最年轻的组中不到60%。值得注意的是，TKA植入后的寿命在10岁以下年龄组之间并不明显（P=0.073~0.458）。观察到无菌性松动的发病时间（3.1至18.9年）比PE磨损（9.8〜17.9年）更早。大多数病例出现在最年轻的群体中。屈伸限制和内翻对准是无菌性松动和PE磨损的显着风险（Cox比例风险回归：分别为P=0.001和0.045）。
结论：年龄较小（<60岁），术后深屈曲无力，在该亚洲队列中，采用现代PS设计后，内翻对准是无菌性松动和PE磨损的重要危险因素。受这些因素影响的术后寿命差异在最初的10年中并不明显，但在第二个十年中出现了。
方法：III；回顾性队列研究。
