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Abstract：
BACKGROUND: Pseudotumor formation is a well-known complication in metal-on-metal (MoM) THA. Pseudotumors combined with elevated serum ion levels and complaints from patients can lead to high revision rates. Long-term (> 10 years) results obtained from randomized trials comparing large-head MoM THA and conventional metal-on-polyethylene (MoP) THA are lacking regarding revision and survival rates, pseudotumor formation, functional outcomes, and serum ion levels.
OBJECTIVE: At 10 years of follow-up, (1) what is the difference in survival and revision rates between large-head (38 to 60 mm) MoM THA and conventional 28-mm MoP THA? (2) What is the difference in pseudotumor formation between large-head MoM THA and MoP THA? (3) Is there a difference in functional outcome between large-head MoM THA and MoP THA? (4) What is the difference in serum ion levels between large-head MoM THA and MoP THA?
METHODS: Between January 2006 and December 2008, 104 patients were randomized to receive either cementless MoM THA (50 patients) or cementless MoP THA (54 patients). In all, 78% (81 of 104) of patients completed the 10-year postoperative follow-up: 36 patients with MoM THA (72%; six patients lost to follow-up) and 45 with MoP THA (83%; four lost to follow-up). In the MoM group, 47% (17) were men, and the patients had a mean ± SD age of 60 ± 5 years. In the MoP group, 38% (17) were men, and the patients had a mean age of 61 ± 5 years. All baseline characteristics were similar between the groups. At 10 years of follow-up, all patient records were screened for revision surgery or complications, and the primary endpoint was survivorship free from revision for any cause at the 10-year follow-up interval, which we analyzed using a Kaplan-Meier survival analysis. All patients had a CT scan to determine the pseudotumor classification, which was reviewed by an independent radiologist. Functional outcome was measured using the patient-reported Oxford Hip Score and Harris Hip Score; the latter was assessed by a blinded nurse practitioner. Finally, serum ion cobalt and chrome concentrations were measured at 10 years postoperatively. Because the a priori sample size calculation for this randomized controlled trial was based on a different endpoint, a post hoc power analysis was performed for this long-term follow-up study, with survival as the primary outcome. It showed that considering the number of included patients, this study would have sufficient power (one-sided testing, alpha 0.05, power 80%) to discern a difference of 20% in the survival rate between the MoP and MoM groups (95% versus 75%).
RESULTS: With the numbers available, there was no difference in survivorship free from revision for any cause between the MoP group and MoM group at 10 years (95% [95% CI 85% to 98%] versus 92% [95% CI 82% to 98%]; p = 0.6). A higher percentage of patients in the MoM group had pseudotumors on CT than those in the MoP group did, but pseudotumors were observed in both groups (56% [20 of 36] in the MoM group versus 22% [10 of 45] in the MoP group, relative risk 1.8 [95% CI 1.2 to 2.6]; p = 0.002). A higher proportion of elevated cobalt and chrome levels was found in the MoM group (19% and 14%, respectively) than in the MoP group (0% for both cobalt and chrome) (cobalt: RR 1.2 [95% CI 1.1 to 1.5]; p = 0.002; chrome: RR 1.2 [95% CI 1.0 to 1.3]; p = 0.01). In 25% of the patients with pseudotumors (5 of 20 patients), there were elevated serum cobalt levels. None of the 23 patients without pseudotumors had elevated cobalt levels (RR 1.3 [95% CI 1.0 to 1.7]; p = 0.01). There was no difference in functional outcome between study groups, nor a difference between patients with a pseudotumor and those without.
CONCLUSIONS: This study showed that the survival of patients with large-head MoM THA was high and comparable to that of those with MoP THA, which contrasts with the high revision rates reported by others. Although some patients with MoP THAs experienced pseudotumors, the risk of a pseudotumor was much greater in MoM hips, and serum ion levels were higher in patients who received an MoM THA. For these reasons and unknown future complications, continued surveillance of patients with MoM THAs seems important.
METHODS: Level I, therapeutic study.
OBJECTIVE: At 10 years of follow-up, (1) what is the difference in survival and revision rates between large-head (38 to 60 mm) MoM THA and conventional 28-mm MoP THA? (2) What is the difference in pseudotumor formation between large-head MoM THA and MoP THA? (3) Is there a difference in functional outcome between large-head MoM THA and MoP THA? (4) What is the difference in serum ion levels between large-head MoM THA and MoP THA?
METHODS: Between January 2006 and December 2008, 104 patients were randomized to receive either cementless MoM THA (50 patients) or cementless MoP THA (54 patients). In all, 78% (81 of 104) of patients completed the 10-year postoperative follow-up: 36 patients with MoM THA (72%; six patients lost to follow-up) and 45 with MoP THA (83%; four lost to follow-up). In the MoM group, 47% (17) were men, and the patients had a mean ± SD age of 60 ± 5 years. In the MoP group, 38% (17) were men, and the patients had a mean age of 61 ± 5 years. All baseline characteristics were similar between the groups. At 10 years of follow-up, all patient records were screened for revision surgery or complications, and the primary endpoint was survivorship free from revision for any cause at the 10-year follow-up interval, which we analyzed using a Kaplan-Meier survival analysis. All patients had a CT scan to determine the pseudotumor classification, which was reviewed by an independent radiologist. Functional outcome was measured using the patient-reported Oxford Hip Score and Harris Hip Score; the latter was assessed by a blinded nurse practitioner. Finally, serum ion cobalt and chrome concentrations were measured at 10 years postoperatively. Because the a priori sample size calculation for this randomized controlled trial was based on a different endpoint, a post hoc power analysis was performed for this long-term follow-up study, with survival as the primary outcome. It showed that considering the number of included patients, this study would have sufficient power (one-sided testing, alpha 0.05, power 80%) to discern a difference of 20% in the survival rate between the MoP and MoM groups (95% versus 75%).
RESULTS: With the numbers available, there was no difference in survivorship free from revision for any cause between the MoP group and MoM group at 10 years (95% [95% CI 85% to 98%] versus 92% [95% CI 82% to 98%]; p = 0.6). A higher percentage of patients in the MoM group had pseudotumors on CT than those in the MoP group did, but pseudotumors were observed in both groups (56% [20 of 36] in the MoM group versus 22% [10 of 45] in the MoP group, relative risk 1.8 [95% CI 1.2 to 2.6]; p = 0.002). A higher proportion of elevated cobalt and chrome levels was found in the MoM group (19% and 14%, respectively) than in the MoP group (0% for both cobalt and chrome) (cobalt: RR 1.2 [95% CI 1.1 to 1.5]; p = 0.002; chrome: RR 1.2 [95% CI 1.0 to 1.3]; p = 0.01). In 25% of the patients with pseudotumors (5 of 20 patients), there were elevated serum cobalt levels. None of the 23 patients without pseudotumors had elevated cobalt levels (RR 1.3 [95% CI 1.0 to 1.7]; p = 0.01). There was no difference in functional outcome between study groups, nor a difference between patients with a pseudotumor and those without.
CONCLUSIONS: This study showed that the survival of patients with large-head MoM THA was high and comparable to that of those with MoP THA, which contrasts with the high revision rates reported by others. Although some patients with MoP THAs experienced pseudotumors, the risk of a pseudotumor was much greater in MoM hips, and serum ion levels were higher in patients who received an MoM THA. For these reasons and unknown future complications, continued surveillance of patients with MoM THAs seems important.
METHODS: Level I, therapeutic study.
摘要：
背景：假瘤形成是金属对金属（MoM）THA中众所周知的并发症。假瘤合并血清离子水平升高和患者主诉可导致较高的翻修率。从比较大头MoMTHA和常规金属对聚乙烯（MoP）THA的随机试验获得的长期（>10年）结果缺乏关于修订和生存率的研究。假瘤形成,功能结果，和血清离子水平。
目标：随访10年，（1）大头（38至60毫米）MoMTHA和常规28毫米MoPTHA之间的生存率和翻修率差异是什么？（2）大头MoMTHA和MoPTHA之间的假瘤形成有什么区别？（3）大头MoMTHA和MoPTHA之间的功能结局有差异吗？（4）2006年12月MoTHA和MoTHA之间结果：有了可用的数字，MoP组和MoM组10年时无任何原因翻修的生存率无差异(95%[95%CI85%~98%]对92%[95%CI82%~98%];p=0.6).MoM组的CT假瘤患者比例高于MoP组，但在两组中均观察到假瘤（MoM组56％[36个中的20个]与MoP组22％[45个中的10个]，相对风险1.8[95%CI1.2至2.6]；p=0.002)。在MoM组中发现较高比例的钴和铬含量（19％和14％，分别）比MoP组（钴和铬均为0％）（钴：RR1.2[95％CI1.1至1.5]；p=0.002；铬：RR1.2[95％CI1.0至1.3]；p=0.01）。在25％的假瘤患者中（20名患者中有5名），血清钴水平升高。没有假瘤的23例患者中没有一个钴水平升高（RR1.3[95％CI1.0至1.7]；p=0.01）。研究组之间的功能结局没有差异，假瘤患者和无假瘤患者之间也没有区别。
结论：这项研究表明，大头MoMTHA患者的生存率较高，与MoPTHA患者的生存率相当，这与其他人报告的高修订率形成鲜明对比。尽管一些患有MoPTHA的患者经历了假瘤，MoM臀部假瘤的风险要大得多，接受MoMTHA的患者血清离子水平较高。由于这些原因和未知的未来并发症，持续监测MoMTHA患者似乎很重要。
方法：一级，治疗性研究。
目标：随访10年，（1）大头（38至60毫米）MoMTHA和常规28毫米MoPTHA之间的生存率和翻修率差异是什么？（2）大头MoMTHA和MoPTHA之间的假瘤形成有什么区别？（3）大头MoMTHA和MoPTHA之间的功能结局有差异吗？（4）2006年12月MoTHA和MoTHA之间
结论：这项研究表明，大头MoMTHA患者的生存率较高，与MoPTHA患者的生存率相当，这与其他人报告的高修订率形成鲜明对比。尽管一些患有MoPTHA的患者经历了假瘤，MoM臀部假瘤的风险要大得多，接受MoMTHA的患者血清离子水平较高。由于这些原因和未知的未来并发症，持续监测MoMTHA患者似乎很重要。
方法：一级，治疗性研究。
