Osteoarthritis of the knee is a common orthopaedic condition. Surgical management consists of high tibial osteotomy and unicompartmental or total knee replacement. With the increasing popularity of unicompartmental replacement and improved outcomes in total knee replacement, high tibial osteotomy has been used less frequently. Despite this, high tibial osteotomy is an appropriate procedure in younger active patients with unicompartmental arthritis of the knee and malalignment.
Previously published articles state that high tibial osteotomy has a survivorship of approximately 90% at 5 years and 77% at 10 years. These studies are based on single hospital or single surgeon data. The authors seek to assess if these results are reproduced at a national level. Many of the procedures are not performed at high volume centres and the outcome of high tibial osteotomy at a national level is not well studied.
This manuscript presents the results of a national, registry-based study of 3195 high tibial osteotomies performed in Finland between 1987 and 2008. Kaplan Meier analysis revealed an overall survivorship of 89% (95% CI 88-90%) at 5 years and 73% (95% CI 72-75%) at 10 years with conversion to total knee replacement as the endpoint.
The authors also analysed survivorship by age, gender, and time of operation. Women and patients over the age of 50 had poor survivorship results compared to men and patients under 50 years of age. The time of operation also had an influence on survivorship: high tibial osteotomies performed between 1998 and 2008 fared worse than those performed between 1987 and 1997.
This study is the largest population-based registry study to evaluate survivorship of high tibial osteotomy for osteoarthritis of the knee. The five-year survivorship of 89% is similar to that of previous studies1-4.The authors state that their ten-year of 73% is slightly worse than the 77% mean survivorship of nine other studies. However, the largest of these studies, Hui et al.,4 had a survivorship of 79%, and a recently published Swedish population-based study reports 70% survivorship at 10 years1.
The real benefit of this study is the large number of patients included (3,195), as well as the long follow-up (mean 10.4 years, 0-22.8). However, this should be tempered by the fairly large dropout rate, with only 54% of the total number of osteotomies included in the data. The dropout rate was primarily due to an inability to identify the correct operative side. In addition to a potential bias from dropout, another area of potential concern is the author's inclusion of hospital data from only 13 of the 36 hospitals included in the study. This may bias the results to outcomes at those 13 hospitals. Despite these limitations, the reader can conclude that the previous results of survivorship of high tibial osteotomy may be applied and replicated by orthopaedic surgeons nationally. Worse survivorship among women and in patients less than 50 years of age is also consistent with the current literature2,5. This supports similar outcomes at a national level compared to the previous single hospital and single surgeon studies. This conclusion must be made with some caution, however, because of some the above noted limitations and because this study includes only orthopaedic surgeons in Finland. These results may not be consistent in other countries due to differences in training, licensing, or other practice procedures between countries.
The other variable analysed, date of operation, also had an effect on survivorship. High tibial osteotomies performed between 1987 and 1997 lasted longer than those performed between 1998 and 2008. The authors provide two reasonable explanations for this: less familiarity with the procedure as time passed, and an increasing likelihood of conversion to total knee replacement more recently as the outcome of TKR has improved. One other possible reason for these differences is the increased number of cases of post-traumatic osteoarthritis in the second group. It is curious that there are no cases of post-traumatic osteoarthritis in the first group. I suspect this may possibly be due to changes in the coding between the two groups.
This study is important, as high tibial osteotomy remains an alternative to unicompartmental and total knee replacement in patients with single compartment arthritis and deformity. It provides surgeons with early and mid-term survivorship of high tibial osteotomy on a national level. This data can be used in discussion with carefully selected patients with knee arthritis when discussing the risks and benefits of high tibial osteotomy compared to unicompartmental and total knee replacement.
Scott Lynch and Greg Pinkowsky, MD at Penn State Hershey Medical Center, Hershey, PA, USA
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