Spierenburg Willemijn, de Vries Astrid J, Boomsma Martijn F, Siepelinga S, Wetzels Tom, van Raaij Jos J A M
Department of Orthopedics, Martini Hospital, Groningen, the Netherlands.
Department of Radiology, Isala, Zwolle, Netherlands.
Clin Orthop Relat Res. 2024 Jul 1;482(7):1173-1182. doi: 10.1097/CORR.0000000000002924. Epub 2023 Dec 12.
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. QUESTIONS/PURPOSES: 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. CONCLUSION: 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. LEVEL OF EVIDENCE: Level I, therapeutic study.
背景：假瘤形成是金属对金属（MoM）全髋关节置换术（THA）中一种众所周知的并发症。假瘤合并血清离子水平升高和患者主诉可导致高翻修率。目前缺乏关于大直径MoM THA与传统金属对聚乙烯（MoP）THA进行比较的随机试验的长期（>10年）结果，包括翻修率和生存率、假瘤形成、功能结果以及血清离子水平。 问题/目的：在10年随访时，（1）大直径（38至60 mm）MoM THA与传统28 mm MoP THA的生存率和翻修率有何差异？（2）大直径MoM THA与MoP THA在假瘤形成方面有何差异？（3）大直径MoM THA与MoP THA在功能结果方面是否存在差异？（4）大直径MoM THA与MoP THA在血清离子水平上有何差异？ 方法：2006年1月至2008年12月期间，104例患者被随机分为接受非骨水泥型MoM THA（50例患者）或非骨水泥型MoP THA（54例患者）。总共78%（104例中的81例）的患者完成了术后10年随访：MoM THA组36例患者（72%；6例失访），MoP THA组45例患者（83%；4例失访）。在MoM组中，47%（17例）为男性，患者的平均年龄±标准差为60±5岁。在MoP组中，38%（17例）为男性，患者的平均年龄为61±5岁。两组之间所有基线特征相似。在随访10年时，对所有患者记录进行筛查以了解翻修手术或并发症情况，主要终点是在10年随访期内任何原因导致的无翻修生存率，我们使用Kaplan-Meier生存分析进行分析。所有患者均进行CT扫描以确定假瘤分类，由一名独立放射科医生进行复查。使用患者报告的牛津髋关节评分和Harris髋关节评分来测量功能结果；后者由一名不知情的护士从业者进行评估。最后，在术后10年测量血清离子钴和铬浓度。由于该随机对照试验的先验样本量计算基于不同的终点，因此对该长期随访研究进行了事后功效分析，以生存作为主要结局。结果表明，考虑到纳入患者数量，本研究有足够的功效（单侧检验，α 0.05，功效80%）来辨别MoP组和MoM组之间20%的生存率差异（95%对75%）。 结果：就现有数据而言，MoP组和MoM组在10年时任何原因导致的无翻修生存率无差异（95%[95%CI 85%至98%]对92%[95%CI 82%至98%]；p = 0.6）。MoM组中CT显示有假瘤的患者百分比高于MoP组，但两组均观察到假瘤（MoM组为56%[36例中的20例]，MoP组为22%[45例中的10例]，相对风险1.8[95%CI 1.2至2.6]；p = 0.002）。MoM组中钴和铬水平升高的比例（分别为19%和14%）高于MoP组（钴和铬均为0%）（钴：RR 1.2[95%CI 1.1至1.5]；p = 0.002；铬：RR 1.2[95%CI 1.0至1.3]；p = 0.01）。在25%的有假瘤患者（20例中的5例）中，血清钴水平升高。23例无假瘤的患者中无一例钴水平升高（RR 1.3[95%CI 1.0至1.7]；p = 0.01）。研究组之间在功能结果方面无差异，有假瘤患者与无假瘤患者之间也无差异。 结论：本研究表明，大直径MoM THA患者的生存率较高，与MoP THA患者相当，这与其他研究报告的高翻修率形成对比。尽管一些MoP THA患者出现了假瘤，但MoM髋关节出现假瘤的风险要大得多，接受MoM THA的患者血清离子水平更高。由于这些原因以及未知的未来并发症，对MoM THA患者进行持续监测似乎很重要。 证据水平：I级，治疗性研究。
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