膝蓋置換缺乏長期的安全性和有效性資料


  【24drs.com】根據線上發表於Lancet期刊的一篇研究,膝蓋置換術是現代醫學的一個成功故事,但是還不知道病患的結果或各式植入物的效果,有關此手術的明確適應症也還缺乏共識。
  
  英國、瑞典和澳洲的作者寫道,因為55歲以下膝蓋跌傷者越來越多、矯正或追蹤手術的比率越高,醫師們需要改善決策方式,另一方面,有些人雖然功能性良好且只有輕微疼痛,仍接受了手術。
  
  這次的研究結果得自對1970年來的文獻回顧,是近一週來、有關骨科關節置換術的安全性和有效性的疑慮的第二篇研究。一篇英國醫學期刊發表的文獻提出質疑,指出成千上萬的髖關節金屬置換術病患,對於可能曝露於有毒性的物質被蒙在鼓裡。
  
  Lancet期刊這篇文章的第一作者Andrew Carr與共同作者們寫道,美國進行全膝關節置換(TKRs)的人數,從1971-1976年的每100,000人年有31.2例,增加到2008年的每100,000人年220.9例,該年共超過650,000例手術,作者們預測,已開發國家之膝關節置換術的需要會持續增加,因為年長人口上升、肥胖比率增加,這兩者也意味著骨關節炎比率更高,這也是該手術的主要適應症。
  
  雖然越來越多人的膝蓋獲得了新的「硬體」,到底有哪些人是真正需要它呢?
  
  Carr博士等人寫道,外科界對於實際適應症、術前症狀的特定嚴重度、肥胖、年紀等並無明確共識,他們指出,國際骨關節炎協會與一個類風濕科組織組成的一個工作小組發現,疼痛、功能及X光片嚴重度和外科醫師之膝關節置換建議無關。
  
  根據作者們表示,膝關節置換術的安全性和有效性資料也是依舊模糊。多數已發表的研究結果,是單一名醫師或單一個中心的系列案例,這些報告大部分記載的是發明該植入物之醫師的實務經驗,因而會有偏見和可能的利益衝突。
  
  研究的關鍵結果是重做手術處置併發症的比率。植入物引起的無菌性鬆動是重做手術的最常見原因,是年輕和有活動力之病患的主要考量,第二個常見原因是感染,其他原因包括術後疼痛、失能、僵硬。
  
  作者們寫道,植入物的設計對於需要重做手術之副作用的風險有相當大的關聯,因此,需透過全國性的登記資料來監測這些植入物。不過,重做手術的其他原因可能是術前診斷、手術技術、經驗、技巧;病患因素;手術室情況;術後照顧。
  
  如果依據TKR或部分膝關節置換(PKRs)區分術後結果,醫師和病患有時候會因為感覺比較像正常膝蓋、手術範圍比較少、感染風險低而選擇PKR,也知道他們在有需要時可以轉換成TKR。不過,部分置換的重做手術風險高於全置換術,根據登記資料,轉換成TKR者需要比一開始就進行TKR者追蹤得更久。
  
  作者們呼籲,繼續發展全國性登記資料,以監測膝關節置換術的長期結果,並使用電子化健康記錄系統來輔助。他們指出,登記資料報告的膝關節置換術結果比發表的臨床試驗少,沒有高品質、無偏見且可信賴的資訊,醫師們無法在每個臨床狀況做出可達到最佳結果的決定。
  
  除了建議做好病患篩選與完整結果報告之外,特別要注意和各個植入物的相關資料,作者們也期待有可以治療初期骨關節炎年輕病患的新策略,而可避免重大手術。
  
  雖然作者們提出了膝關節置換狀態的疑慮,仍對其有所好評。他們寫道,關節置換術是新手術中最成功的範例之一,使末期關節炎患者的生活品質有所改善。
  
  資料來源:http://www.24drs.com/professional/list/content.asp?x_idno=6749&x_classno=0&x_chkdelpoint=Y
  

Knee Replacement Data Scarce for Long-Term Safety, Effectiveness

By Robert Lowes
Medscape Medical News

March 5, 2012 — Knee replacement surgery is a success story of modern medicine, yet not enough is known about patient outcomes or the effectiveness of various implants, and consensus is lacking about the precise indications for the procedure, according to a study published online March 6 in the Lancet.

The authors, based in the United Kingdom, Sweden, and Australia, write that surgeons need improved decision-making as more and more possible candidates for new knees fall are younger than 55 years — a group that has a higher rate of revision or follow-up surgery. On another problematic note, some patients undergo the operation despite having good functional ability and only mild pain beforehand.

The article, based on a literature review going back to 1970, is the second in less than a week raising doubts about the evidence on orthopaedic joint implant safety and effectiveness. On February 28, the British Medical Journal published an article charging that hundreds of thousands of patients with metal-on-metal hip replacements were kept in the dark about possible exposure to toxic substances.

Andrew Carr, FRCS FmedSci, lead author of the Lancet article, and coauthors write that the number of total knee replacements (TKRs) in the United States increased from 31.2 per 100,000 person-years in the period from 1971 to 1976 to 220.9 per 100,000 person-years in 2008, for a total that year of more than 650,000 procedures. The authors predict that the demand for knee replacement will continue to grow in developed countries, in light of aging populations and rising obesity rates, which both portend higher rates of osteoarthritis, the main clinical indication for the operation.

Although more and more people are getting new hardware for their knees, fuzzy thinking prevails as to who really needs it.

"No clear consensus exists within the surgical community about exact indications, particularly severity of preoperative symptoms, obesity, and age," Dr. Carr and coauthors write. They point to a task force organized by the Osteoarthritis Research Society International and a rheumatology organization that found that "pain, function, and radiographic severity are not associated with a surgeon's recommendation for knee replacement."

Improve Treatment of Early-Stage Osteoarthritis to Avoid Surgery

Outcomes data on the safety and effectiveness of knee-replacement surgery also are fuzzy, according to the authors. Most published reports of outcomes, they write, are single-surgeon or single-center case series. Many of these reports chronicle the practice of a surgeon who invented the implant, "which introduces bias and a potential conflict of interest."

The key outcome studied was the rate of revision surgery to deal with complications. Aseptic loosening, usually caused by implant wear, is the most common reason for revision surgery, and "is mainly a concern in young and active patients." The second most common reason is infection. Other major causes are postoperative pain, instability, and stiffness.

The authors write that an implant's design can make a big difference in minimizing or maximizing the risk for adverse events that require revision surgery, hence the need to monitor implants through national registries. However, revision surgery also can be blamed on preoperative diagnosis; surgical technique, experience, and skill; patient factors; operating room conditions; and postoperative care.

Outcomes data break down into those for TKRs vs those for partial-knee replacements (PKRs). Surgeons and their patients sometimes will choose a PKR for the sake of a more normal-feeling knee, less extensive surgery, and a lower risk for infection, knowing that they have the option of converting to a TKR if need be. However, partial replacement has a higher risk for revision surgery than total replacement, and a conversion TKR is more likely to require more follow-up than a primary TKR, according to registry data.

The authors urge the continued development of national registries to monitor the long-term outcomes of knee replacement surgery, as well as the use of electronic health record systems to facilitate this. They note that registries tend to report less glowing outcomes for knee replacement than published clinical trials. "Without high quality, unbiased, and reliable information, surgeons cannot make informed decisions about how to achieve the best outcome in each clinical situation," the authors write.

In addition to recommending better patient selection and better reporting of outcomes, particularly as it relates to individual implant devices, the authors also call for new strategies to treat early-stage osteoarthritis in younger patients that will "avoid the need for major surgery altogether."

Despite the misgivings they express about the state of knee replacement, the authors also render praise.

"Joint-replacement surgery," they write, "is one of the most successful examples of innovative surgery, and has resulted in substantial quality-of-life gains for people with end-stage arthritis."

One coauthor is paid by the Australian Orthopaedic Association as director of the National Joint Registry. One coauthor has received honoraria and support for travel from Biomet. One coauthor has received consultancy fees from Stryker and institutional research grants from Genzyme. The 4 remaining authors have disclosed no relevant financial relationships.

Lancet. Published online March 6, 2012.

    
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