Mäntymäki Heikki, Mäkelä Keijo T, Vahlberg Tero, Hirviniemi Joni, Niinimäki Tuukka
Department of Orthopedics and Traumatology, Turku University Hospital, Turku, Finland.
Department of Surgery, Vaasa Central Hospital, Hietalahdenkatu 2-4, 65130, Vaasa, Finland.
Clin Orthop Relat Res. 2016 Sep;474(9):1999-2005. doi: 10.1007/s11999-016-4774-7. Epub 2016 Mar 3.
Modern hip implants typically feature modular heads, which allow for easy exchange and removal from the femoral stem at the time of revision. However, owing to fretting, corrosion, or cold welding, the modular head may be difficult or impossible to separate from the underlying trunnion, especially if the implant has titanium interfaces between the head and the stem. We have repeatedly encountered difficulty removing the titanium sleeve adapter in the M(2)a-Magnum(TM) implant. Although the manufacturer warns about this complication and cases with these difficulties have been reported to the United States FDA, we believed this topic is important to study, because the frequency of difficulties in head removal is unknown and the complications related to this event have not been characterized.
QUESTIONS/PURPOSES: We asked: (1) Do revisions of M(2)a-Magnum(TM) implants differ from those of M(2)a-38(TM) implants in terms of ease of removal of the femoral head? (2) In cases where difficulty with M(2)a-Magnum(TM) head removal occurred, was the operative time, bleeding, risk of periprosthetic fracture, or joint infection increased compared with cases where the M(2)a-Magnum(TM) head was removed without difficulties?
Between 2004 and 2014, we revised 296 THAs with metal-on-metal implants that involved M(2)a-Magnum(TM) (123) or M(2)a-38(TM) heads (88); of those, 84 were planned to include a femoral stem revision and insufficient data were available for three operations, so they were excluded from this analysis, leaving 124 THAs in the current retrospective study (70 THAs with M(2)a-Magnum(TM) and 54 THAs with M(2)a-38(TM) heads).The method of modular head removal, any difficulties removing the femoral head from the trunnion, operation time, and complications were recorded based on chart review.
All the observed problems of detaching the head or taper adapter were among M(2)a-Magnum(TM) heads; there were no problems detaching the head in revisions of the M(2)a-38(TM) implant. In 29% (20 of 70) of revisions of the M(2)a-Magnum(TM) implant, the modular head could not be detached by knocking it with a punch and a mallet. Seventeen percent (12 of 70) of hips needed an unplanned stem revision owing to difficulties with head removal. In revisions of the M(2)a-Magnum(TM) implant that experienced head-removal problems, the median operative time was longer (144 minutes; range, 75-274 minutes) and bleeding was greater (725 mL; range, 300-2200 mL) compared with revisions of the M(2)a-Magnum(TM) implant without head removal problems (77 minutes, range, 33-197 minutes, p < 0.001; 475 mL, range, 50-1500 mL, p = 0.004). With the numbers available, we did not see differences in terms of the proportion of patients experiencing major complications (periprosthetic fracture or postoperative infections) between the groups (difficult versus easy; 25% [five of 20] versus 8% [four of 50]; odds ratio, 3.8 [95% CI, 0.9-16.2], p = 0.067).
The titanium-titanium taper junction can be very difficult to separate during revision THAs, and if not anticipated, this problem can result in larger and more complicated revision procedures in patients who have the M(2)a-Magnum(TM) implant. Although the global use of metal-on-metal implants in THAs has decreased dramatically during the last several years, many thousands remain in service and therefore still might require revision. It is crucial to be prepared with special tools, including a femoral head extraction tool and diamond saw. The patient has to be informed of the possibility of a more extensive operation than preoperatively planned.
Level III, therapeutic study.
现代髋关节植入物通常具有模块化股骨头，这使得在翻修时易于从股骨干上进行更换和取出。然而，由于微动、腐蚀或冷焊，模块化股骨头可能难以或无法从下方的耳轴分离，特别是当植入物在股骨头和股骨干之间有钛界面时。我们在M(2)a-Magnum(TM)植入物中反复遇到移除钛套筒适配器的困难。尽管制造商已警告过这种并发症，且美国食品药品监督管理局（FDA）也收到过相关困难案例的报告，但我们认为这个主题很值得研究，因为股骨头移除困难的发生率未知，且与此事件相关的并发症尚未得到明确描述。
问题/目的：我们提出：（1）就股骨头的移除难易程度而言，M(2)a-Magnum(TM)植入物的翻修与M(2)a-38(TM)植入物的翻修有何不同？（2）在M(2)a-Magnum(TM)股骨头移除困难的病例中，与M(2)a-Magnum(TM)股骨头移除顺利的病例相比，手术时间、出血量、假体周围骨折风险或关节感染风险是否增加？
2004年至2014年间，我们对296例采用金属对金属植入物的全髋关节置换术（THA）进行了翻修，其中涉及M(2)a-Magnum(TM)（123例）或M(2)a-38(TM)股骨头（88例）；其中，84例计划包括股骨干翻修，另有3例手术数据不足，因此被排除在本分析之外，在当前的回顾性研究中留下124例THA（70例采用M(2)a-Magnum(TM)，54例采用M(2)a-38(TM)股骨头）。通过查阅病历记录模块化股骨头的移除方法、从耳轴移除股骨头时遇到的任何困难、手术时间和并发症情况。
所有观察到的头部或锥度适配器分离问题均出现在M(2)a-Magnum(TM)股骨头中；M(2)a-38(TM)植入物翻修时在头部分离方面没有问题。在M(2)a-Magnum(TM)植入物翻修中，29%（70例中的20例）的模块化股骨头无法通过用冲头和锤子敲击来分离。由于头部移除困难，17%（70例中的12例）的髋关节需要进行计划外的股骨干翻修。与M(2)a-Magnum(TM)植入物翻修时无头部移除问题的情况相比，M(2)a-Magnum(TM)植入物翻修时出现头部移除问题的病例，中位手术时间更长（144分钟；范围75 - 274分钟），出血量更大（725毫升；范围300 - 2200毫升）（分别为77分钟，范围33 - 197分钟，p < 0.001；475毫升，范围50 - 1500毫升，p = 0.004）。就现有数据而言，我们未发现两组（困难组与顺利组）患者发生主要并发症（假体周围骨折或术后感染）的比例存在差异（25% [20例中的5例] 对8% [50例中的4例]；比值比，3.8 [95% CI，0.9 - 16.2]，p = 0.067）。
在翻修全髋关节置换术中，钛 - 钛锥度连接可能非常难以分离，如果没有预先料到，这个问题可能导致采用M(2)a-Magnum(TM)植入物的患者进行更大规模、更复杂的翻修手术。尽管在过去几年中，全髋关节置换术中金属对金属植入物的全球使用量已大幅下降，但仍有数千例仍在使用，因此仍可能需要翻修。准备好特殊工具至关重要，包括股骨头取出工具和金刚石锯。必须告知患者手术可能比术前计划的更为广泛。
III级，治疗性研究。
