To The Editor:
I read with interest "Total Knee Arthroplasty Following Proximal
Tibial Osteotomy: Risk Factors for Failure"
(2004;86:474-9) by Parvizi et
al. The authors reviewed the results of 166 cemented condylar knee
replacements done in 118 patients who had previously had a proximal tibial
osteotomy. These knee replacements had relatively inferior results, and the
authors identified risk factors for early failure.
The problems cited by the authors were malalignment, patella baja,
instability, periarticular scarring, proximal tibial bone deficiency, and
retained hardware. The great detail about the knee arthroplasty, the long
follow-up, and the meticulous study design are all severely compromised by the
absence of any detail regarding the technique of osteotomy. Were these opening
or closing wedge corrections? Was the fibula osteotomized or was the proximal
tibiofibular joint sprung? Was there internal, external, or no fixation? Were
casts applied or were the patients allowed to move their knees? Were the
corrections done acutely or gradually?
Do the authors suggest that these techniques are all the same? That would
be as ludicrous as clumping together a group of knee replacements to include
revision total knee replacements, cemented and uncemented primary total knee
replacements, posterior cruciate-sparing and retaining knee replacements, and
unicondylar knee replacements.
Presumably, this was predominantly a group of closing wedge Coventry-type
high tibial osteotomies. Today, this technique has been largely abandoned
because of its association with patella baja, decreased metaphyseal bone
stock, lateral knee laxity, and altered proximal tibial anatomy.
Modern techniques of proximal tibial osteotomy, including opening wedge
corrections, stable fixation that allows early weight-bearing and knee range
of motion, gradual corrections with external fixation after percutaneous
osteotomy, and adjunctive ligament tensioning techniques, should not be
associated with the specific problems cited by the authors.
The authors have suggested that proximal tibial osteotomy in general will
compromise future total knee replacement. This is a dangerous and inaccurate
message that is not supported by their data or the lack thereof. The authors
should give the readers specific information about the osteotomy techniques
used.
Dr. Rozbruch is correct that not all osteotomies are the same, and it is
true that the details of the osteotomies were not included in the study. The
osteotomies that were preformed prior to the total knee replacements in this
series were lateral closing wedge osteotomies as popularized by Coventry. They
were performed by different surgeons, who, while using the same basic
technique and principles, certainly had small variations in the surgical
technique and postoperative management. Unfortunately, detailed data regarding
the exact technique of each osteotomy procedure were not available. We
acknowledge that this is an inherent problem, common to many retrospective
studies. We agree that various differences in technique (e.g., management of
the proximal part of the fibula, early range of motion versus casts, amount of
bone resected, etc.) could influence the result of the osteotomy and
potentially the result of subsequent total knee replacement, but we believe
that the results are valid for closing wedge osteotomies and can be
generalized to such patients.
We agree with Dr. Rozbruch that newer techniques of osteotomy, such as
opening wedge osteotomy, the use of stable fixation allowing for early range
of motion, and other techniques cited by Dr. Rozbruch, may improve the results
of total knee replacement after proximal tibial osteotomy. We are also hopeful
that, with newer techniques, the results of knee replacement will be more
favorable and that the concerns cited in our article will be less of a
problem. However, to date, there are insufficient data to support this claim,
and further study of total knee replacement after opening wedge osteotomy is
needed now that there are newer techniques of proximal tibial osteotomy.