Leg length change after opening wedge and closing wedge high tibial osteotomy: A meta-analysis
Leg length change after opening wedge and closing wedge high tibial osteotomy: A meta- analysis
Jun-Ho Kim 0 1
Hyun-Jung Kim 0
Dae-Hee Lee 0 1
0 Editor: Ara Nazarian, Harvard Medical School/ BIDMC , UNITED STATES
1 Department of Orthopaedic Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine , Seoul , Korea , 2 Department of Preventive medicine, Korea University College of Medicine , Seoul , Korea
Four studies were included in the meta-analysis. Although pooled results showed leg length
changes from before to after surgery were ±6.93 mm (95% confidence interval [CI]: ±17.53
to 3.67 mm; P = 0.20) in opening wedge HTO and 1.97 mm (95% CI: ±7.13 to 11.07 mm;
P = 0.67) in closing wedge HTO, respectively, these values were statistically not significant.
However, the difference in the pooled mean leg length change from before to after surgery
between opening wedge and closing wedge HTO was 8 mm, a difference that was
significant (95% CI: 6.53 to 9.46 mm; P<0.001).
The change in leg length was not statistically significant for either opening or closing wedge
HTO. However, leg length change from before to after surgery was 8 mm greater for opening wedge HTO than for closing wedge HTO.
Theoretical considerations suggest that leg length increases after opening wedge high tibial osteotomy (HTO) and decreases after closing wedge HTO; however, in vivo studies have yielded conflicting results. This meta-analysis therefore assessed changes in leg length after opening wedge and closing wedge HTO.
All studies comparing pre- and postoperative leg length in patients who underwent opening
and/or closing wedge HTO were included. Two reviewers independently recorded data from
each study in terms of sample size as well as preoperative and postoperative leg length of
open wedge and/or closed wedge HTO groups.
Data Availability Statement: All relevant data are
within the paper and its Supporting Information
Funding: The author(s) received no specific
funding for this work.
Competing interests: The authors have declared
that no competing interests exist.
High tibial osteotomy (HTO) is accepted as the established treatment for patients with early
medial compartment knee osteoarthritis and varus deformity.[
] Among various types of
HTO, the two most commonly used types are opening wedge and closing wedge HTO.[
rationale of the procedure for pain relief is to shift the weight bearing force from the arthritic
medial compartment to the intact lateral compartment by correcting alignment in the coronal
plane.[3±5] The consideration of alignment correction in only the coronal plane can lead to
unintended effects such as a change in the posterior tibial slope,[
] patellar height, and
rotation of the distal tibia below the osteotomy site.[
] One of these unintended alterations
is leg length change after opening or closing wedge HTO. Theoretically, leg length increases
after opening wedge HTO due to spreading of the osteotomy site in the proximal tibia and
decreases after closing wedge HTO due to bone loss by removal of the osteotomy area in the
proximal tibia. However, this phenomenon in HTO has received relatively little attention from
orthopedic surgeons; there is no general consensus on whether leg length is actually increased
after opening wedge HTO and decreased after closing wedge HTO, and previous studies[11±
14] showed conflicting results. In addition, it is unclear whether the magnitude of leg length
changes after surgery is different between opening and closing wedge HTO.
This study was designed to verify whether leg length after surgery is actually increased in
opening wedge HTO and decreased in closing wedge HTO, as well as to quantify the difference
in leg length change following surgery between opening and closing wedge HTO. It was
hypothesized that leg length actually increases after opening wedge HTO and decreases after
closing wedge HTO, and that the amount of leg length changes are similar between opening
and closing wedge HTO.
Materials and methods
This meta-analysis was performed according to the guidelines of the preferred reporting items for systematic reviews and meta-analysis (PRISMA) statement (S1 PRISMA Checklist).
Data & literature sources
The study design was based on Cochrane Review Methods. Multiple comprehensive databases,
including MEDLINE (January 1, 1976 to May 31, 2015), EMBASE (January 1, 1985 to May 31,
2015), the Cochrane Library (January 1, 1987 to May 31, 2015) and KoreaMed (June 1, 1958 to
May 31, 2015), were searched for studies that evaluated the leg length in patients who
underwent open wedge and/or closed wedge HTO (S1 Search Strategy). There were no restrictions
on language or year of publication. Search terms used in the title, abstract, MeSH and keyword
fields included "Osteotomy" [tiab] OR "Tibial" [tiab] OR "High" [tiab] OR "Open" [tiab], and
"Closed or Closing" [tiab], and "Osteotomy" [MeSH] or "leg length" [tiab] or "limb length
[tiab]". After the initial electronic search, relevant articles and bibliographies were searched
manually. Articles identified were assessed individually for inclusion.
Study inclusion was decided independently by two reviewers, based on the predefined selec
tion criteria. Titles and abstracts were read; if suitability could not be determined, the full
article was evaluated. Studies were included in the meta-analysis if (1) they described preoperative
and postoperative leg length in patients who underwent opening and closing wedge HTO; (2)
they simultaneously reported direct comparisons of change in leg length for opening wedge
and closing wedge HTO; (3) their primary outcomes included change in leg length after
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surgery; (4) they fully reported the sample numbers of their subjects in a final analysis, as well
as means and standard deviations of leg length change; and (5) they used adequate statistical
methods to compare the leg lengths before and after surgery.
Two reviewers independently recorded data from each study using a predefined data extrac
tion form. Any disagreement unresolved by discussion was reviewed by a third author.
Variables recorded included: (1) type of HTO±opening wedge, closing wedge, or both; (2) means and standard deviations of preoperative and postoperative leg length in open wedge and/or closed wedge HTO groups; and (3) sample size of each group. If these variables were not mentioned in the articles, we contacted the study authors by email to request the data.
Assessment of methodological quality
Two reviewers independently assessed the methodological quality of each study using the
Newcastle-Ottawa Scale, as recommended by the Cochrane Non-Randomized Studies
Methods Working Group. For our purposes, the Newcastle-Ottawa Scale's star system, which
awards stars depending on level of bias, was modified to include only low (one star), high, and
unclear bias. Each study was judged on three criteria: the selection of the study groups, the
comparability of the groups, and the ascertainment of either the exposure or outcome of
interest for case-control or cohort studies. Any unresolved disagreements between reviewers were
resolved by consensus or by consultation with a third investigator.
The main outcomes of the meta-analysis were the mean difference in leg length change before
and after surgery in either open wedge or closed wedge HTO. The mean difference and 95%
confidence interval (CI) were used for continuous outcomes in comparing preoperative and
postoperative leg length for each osteotomy. Heterogeneity was determined by estimating the
proportion of between-study inconsistencies due to actual differences between studies, rather
than differences due to random error or chance, using the I2 statistic, with values of 25%, 50%,
and 75% considered low, moderate, and high, respectively. All statistical analyses were
performed using RevMan version 5.2.
Identification of studies
Fig 1 shows the details of study identification, inclusion, and exclusion. An electronic search
yielded 379 studies in PubMed (MEDLINE), 269 in EMBASE, 322 in Web of Science, 480 in
SCOPUS, and 25 in the Cochrane Library. Three additional publications were identified
through manual searching. After removing 541 duplicates, 937 studies remained; of these, 920
were excluded based on reading of the abstracts and full-text articles, and an additional 17
studies were excluded since they did not have usable information or reported the leg length
change for only either open wedge or closed wedge HTO. After applying these criteria, four
studies[11±14] were finally included in this meta-analysis.
Study characteristics and quality of the included studies
All four included studies directly compared the leg length change in subjects before and after surgery between opening wedge and closing wedge HTO, with four studies also comparing flexion and extension moments before and after surgery. Of four included studies, two were
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Fig 1. PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) flow diagram
of the identification and selection of the studies included in this meta-analysis.
retrospective comparison studies, and two were prospective comparison studies. All included
studies showed a low risk of selection bias. All provided detailed demographic data of each
open wedge and closed wedge HTO group. None assessed possible confounding factors. Of
these four studies, three were considered high quality, with >5 points on the
Ottawa Scale (Table 1).
Time point of postoperative
Fig 2. Forest plot showing changes in pre- and postoperative leg length in opening wedge high tibial
Leg length change after opening-and closing wedge HTO
The four included studies evaluated a total of 125 and 171 knees that underwent opening and
closing wedge HTO, respectively. The pooled mean leg length changes from before to after
opening and closing wedge HTO were ±6.93 mm (95% CI: ±17.53 to 3.67 mm; P = 0.20; I2 =
0%, Fig 2) and 1.97 mm (95% CI: ±7.13 to 11.07 mm; P = 0.67; I2 = 0%, Fig 3), respectively.
These results seem to indicate that the leg length increased 6.93 mm after opening wedge and decreased 1.97 mm after closing wedge HTO. However, these leg length changes from before to after surgery were statistically not significant.
Differences in leg length change between opening and closing wedge
All four included studies directly compared the leg length change from before to after surgery
for opening and closing wedge HTO. The pooled mean difference in leg length change from
before to after surgery in opening and closing wedge HTO was 8 mm (95% CI: 6.53 to 9.46
mm; P<0.001; I2 = 71%, Fig 4), indicating that leg length was 8 mm greater after opening
wedge than after closing wedge HTO.
The results of meta-regression analyses are reported in Table 2. The time point at which the
postoperative radiograph was taken was not significantly associated with mean difference in
leg length change from before to after surgery in opening and closing wedge HTO. This
finding indicated that the difference in leg length change between opening-and closing wedge
HTO was not influenced by the time point at which radiographs were taken after surgery.
The most important finding of this study was that leg length did not differ significantly between before and after surgery for both opening and closing wedge HTO. However, the difference in leg length change from before to after surgery was 8 mm greater in opening wedge than in closing wedge HTO.
Fig 3. Forest plot showing changes in pre- and postoperative leg length in closing wedge high tibial
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Fig 4. Forest plot showing the difference in leg length change between opening and closing wedge
high tibial osteotomy.
The results of our current meta-analysis indicate that the change in limb length after either
opening or closing wedge HTO was not statistically significant, and hence that a change in
overall limb length does not seem to be a disadvantage of HTO. However, as this meta-analysis
included only a small number of samples across four studies, the present results will need to be
confirmed in an analysis of a greater number of cases. Theoretically, there was a trend toward
increasing leg length after opening wedge HTO and decreasing leg length after closing wedge
HTO. These trends were partially supported by our meta-analysis, because the pooled results
of leg length change from before to after surgery showed 0 heterogeneity. In addition, all
included opening wedge HTO studies showed increasing leg length after surgery, and all
included closing wedge HTO studies showed decreasing leg length after surgery, although the
pooled results of these data were not statistically significant. However, it is widely accepted
that the magnitude of leg length change after surgery is greater in opening wedge than in
closing wedge HTO, because leg lengthening effect induced by valgus realignment could amplify
the leg length increment in opening wedge HTO, but could offset the leg length decrement in
closing wedge HTO.[
] In the current meta-analysis, the amount of leg length increment was
6 mm in opening wedge HTO and the leg length decrement was 2 mm in closing wedge HTO,
although these values were not statistically significant.
The statistical insignificance of leg length change from before to after opening and closing
wedge HTO may reflect the small magnitude of leg length change after surgery rather than
mathematically calculated amounts. In closing wedge HTO, as described above, the valgus
realignment effect could offset the tibial metaphyseal bone loss. Therefore, if valgus
realignment effects are greater than tibial metaphyseal bone loss, the net leg length change could
increase. Even in opening wedge HTO, the shifting weight-bearing force from medial to lateral
compartment could offset the effect of tibial lengthening after opening wedge HTO,[
especially in cases with severe soft tissue laxity on the lateral side, because weight-bearing force can
lead to overcorrection of alignment despite preoperative planning, which can shorten the leg
length more than required for adequate correction. In addition, the increment of posterior
slope after opening wedge HTO reduces the leg lengthening effect of opening wedge HTO,
because the increased posterior slope leads to anterior translation of the tibia,[
] which could
decrease the magnitude of leg lengthening effect in open wedge HTO.
There was no general consensus about the extent to which the change in leg length could result in clinically relevant problems such as back pain and progression of knee osteoarthritis due to alteration of gait kinematics. Some degree (less than 2 cm) of leg length discrepancy can be allowed in humans because of a compensatory mechanism that dynamically lengthens
the shorter limb and shortens the longer limb,[
] probably to minimize the displacement of
the body center of mass and consequently reduce body energy expenditure.[
] However, a
leg length discrepancy±whether lengthening or shortening±should be avoided as much as
possible, because previous studies demonstrated that leg lengthening, even by less than 1 cm,
increases the chance of developing knee osteoarthritis in the longer limb,[
] and that
correcting leg length discrepancy of only 5.6 mm relieved chronic low back pain, possibly by reducing
lumbar spine lateral flexion and rotation.[
] The result of the current meta-analysis showed
an apparent difference in leg length change between opening wedge and closing wedge HTO;
the opening wedge HTO resulted in an 8-mm greater leg length than closing wedge HTO.
This small difference, although less than 1 cm, could induce clinically important symptoms,
according to the results of the above two studies. Therefore, orthopedic surgeons should
carefully consider leg length changes when deciding the type of HTO. If patients have a shorter leg
length on the operative side than on the contralateral side, open wedge HTO should be
considered rather than closing wedge HTO. In contrast, closing wedge HTO rather than opening
wedge HTO should be chosen for cases in which leg lengthening is anticipated after surgery.
Moreover, when treating patients with bilateral medial osteoarthritic varus knees and equal leg
lengths, the same type of HTO should be performed on both legs.
Several limitations should be taken into consideration when interpreting the results of the
current study. There are other factors that could affect leg length change after HTO. The leg
length change could be influenced by the amount of alignment correction. It has been reported
in the literature that the greater the amount of correction of limb alignment, the greater the leg
length, even after closing wedge HTO. In addition, radiographs taken at different time points
after surgery could also affect leg length change, because some residual flexion contractures
could remain for up to 6 months after surgery. Also, the leg length determined from
radiographs may depend on the conditions used when recording the radiographs; however, all of
the studies included in this meta-analysis considered the effect of radiographic magnification.
About half of the studies included in this meta-analysis were also retrospective observational
comparison studies. These were influenced by different factors such as alignment correction
amount, variable radiography time points, differences in the conditions used when recording
radiographs, and low levels of evidence for the study design, resulting in inherent
heterogeneity due to uncontrolled bias. However, the results of the current study with regard to leg length
change from before to after surgery showed absolutely no heterogeneity, as represented by
ªzero (0)º I2 values, for both opening wedge and closing wedge HTO, which showed the robust
reliability of this meta-analysis. In addition, the results of meta-regression analysis in our
study showed no correlation between differences in leg length change in opening-and closing
wedge HTO according to time of radiography after surgery. Finally, this study did not evaluate
the effects of leg length change in opening or closing wedge HTO on clinical results such as
knee osteoarthritis and back pain due to spine problems. Future research should examine
Leg length did not change significantly from before to after surgery in both opening- and closing wedge HTO. However, leg length change from before to after surgery was 8 mm greater in opening wedge HTO than in closing wedge HTO.
S1 PRISMA Checklist.
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S1 Search Strategy.
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article, nor have any funds been received in support of this study.
Conceptualization: Jun-Ho Kim, Dae-Hee Lee.
Data curation: Jun-Ho Kim, Dae-Hee Lee.
Formal analysis: Hyun-Jung Kim, Dae-Hee Lee.
Methodology: Hyun-Jung Kim, Dae-Hee Lee.
Resources: Dae-Hee Lee.
Supervision: Hyun-Jung Kim.
Validation: Dae-Hee Lee.
Writing ± original draft: Jun-Ho Kim, Dae-Hee Lee.
Writing ± review & editing: Jun-Ho Kim, Dae-Hee Lee.
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(NOS) for assessing the quality of nonrandomized studies in meta-analyses. In 2013.
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