High Tibial Osteotomy With Miniaci Planning Using Manual and Semiautomated Digital Measures

Abstract

Background:

Inadequate deformity analysis and planning before high tibial osteotomy (HTO) may result in correction errors with unsatisfactory clinical results.

Indications:

The purpose of this article is to describe the deformity analysis and preoperative planning before HTO. This surgery is effective for young patients with compartmental mild knee osteoarthritis. A partial deformity analysis without considering the femoral or intra-articular deformity may lead to overcorrection or excessive joint line obliquity. Preoperative planning using the Miniaci method with manual or semiautomated digital measures may help to prevent these types of errors.

Technique Description:

Landmarks are used at the proximal femoral side, distal condyles, proximal tibial plateau, and talus borders to define angles automatically on PeekMed software. Fujisawa point is determined to be 50% of the length of the proximal tibia, and Miniaci method is performed after defining the weightbearing line. The method can be performed manually or semiautomatically with the software. In this last case, the optimal procedure to be done to correct the malalignment is proposed by the software which automatically does the opening of the osteotomy to match the desired weightbearing axis and displays the size of the wedge in millimeters.

Results:

The intraobserver and interobserver reproducibility were performed by 2 different analyses and 2 different observers. The precision of the measures was confirmed based on computed tomographic (CT) scan 3-dimensional measures defined as the gold standard. All the intraobserver and interobserver reproducibility correlation coefficients and precision were satisfactory compared with the gold standard. Hip-knee-ankle angle may vary because of weightbearing situations between CT and long-axis x-rays.

Discussion/Conclusion:

The interest of semiautomated software for angular value measurements is now well recognized, and the inclusion of anatomical landmarks allows accurate and reproducible angular value measurements. Automatic knee osteotomy planning analyzes the metaphyseal deformity of both the tibia and the femur, and the software suggests the optimal procedure with the degree of openness to obtain the desired mechanical axis without creating excessive joint line obliquity

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

High tibial osteotomy (HTO) is an efficient procedure in patients with early osteoarthritis and substantial tibial deformity. Digital methods are helpful to ensure reproducibility and accuracy of planning, but semiautomated software may decrease human errors during the planning process.

Indications of HTO are patients aged below 65 years and body mass index (BMI) below 30 kg/m² with a lower deformity, which is mainly present at the proximal aspect of the tibia.

To define the correction, we use Miniaci method. The first step is to draw the Mikulicz line, which starts at the femoral head and ends at the ankle position.

In the second step, we aim to define the passing point of the weightbearing line after surgery. To do that, Fujisawa et al ⁷ define the ideal point to be 62.5%, but more recent papers define the optimal position of this point to be 50% to 55%.

The native and postoperative positions of the ankle are projected, and the angle between those 2 ankle positions defines the correction to be done at the hinge position.

Thanks to calibrated x-rays, this angle is reported and the opening is measured at the medial aspect of the tibia.

To be reproducible, those long-axis x-rays need to be done with an exact rotation of the foot to not overestimate the varus and the valgus. In the second, those images need to be done through weightbearing to correctly estimate the intra-articular wear and the intra-articular deformity.

This is how we plan our digital software; this step always starts with calibration. A small spheric cylinder is measured, and we then moved to the semiautomated deformity analysis. Landmarks such as center of the femoral head, top of the femoral head, great trochanter, distal condyles, proximal tibial plateau, and talus borders are used. Lateral and medial angles are defined automatically.

The results here show a substantial metaphyseal deformity of the tibia with medial proximal tibial angle (MPTA) of 83°.

To do that, we use Miniaci planning to first define the Fujisawa point. This point is here defined to be 50% of the length of the proximal tibia. So, we divide the global length of the tibia by 2 to fix a point which would be our passing point for the weightbearing line after the surgery.

We then define the weightbearing line, Mikulicz line, from the center of the femoral head to the center of the ankle and a second line passing from the center of the femoral head to the desired Miniaci point and the Fujisawa point we have defined. The hinge point is identified at the top of the fibular head, and then the correction to be done is measured in between the initial position of the ankle to the hinge point and the future position after shifting of weightbearing to the ankle. Here, this angle is 9° after the measurements, that is, 9.2°.

We define the optimal cuts using Miniaci definition, so the angle in between the cutting plane and the lateral cortex of the tibia should be 110°. Once this cutting line is defined, we move down the second line of the angle to reproduce the correction we measured, here in 9°. The only landmark who have during the surgery is the width of this opening to be created, and to correct 9°, we need to have 10 mm.

The opening is then created virtually, using a cut function from the software to successfully shift the distal aspect of the leg by 9° and confirm that those 9° convert into a 10-mm wedge. The opening is performed, and when a 9-mm opening is done, the measure that is reported on the top of the opening here, the base of the triangle is confirmed to be 10 mm.

We then instruct the software to do all the corrections automatically based on the measurements we have done previously during the deformity analysis. We have just raised the optimal line for HTO following the Miniaci definition of the ideal cut.

Then, the software asks us whether the osteotomy has to be done automatically, and it will by itself correct the leg to have a Mikulicz line passing exactly through the middle of the joint at the Miniaci point and Fujisawa point we define.

The osteotomy is done by the software, and we confirm here that the opening that needs to be performed is around 10 mm during the surgery to obtain a perfectly aligned leg.

We designed a study to confirm the accuracy and reproducibility of our software method. We analyzed 49 HTOs in 49 varus knees, mostly men, with an average age of 49 years and BMI of 25 kg/m². The intraobserver and interobserver reproducibility were performed by 2 different analyses and 2 different observers, and the precision of the measurements was confirmed based on computed tomographic (CT) scans, 3-dimensional measures, to be defined as the gold standard.

All the intraobserver and interobserver reproducibility correlation coefficients and the precision were satisfactory compared with the gold standard. Hip-knee-ankle (HKA) angle may vary because of weightbearing situations between CT and long-axis x-rays.

Here is the references used and the article and the video.

We describe here a real-time planning with a case example. The long-axis x-ray of the patient is loaded into the software, and the software is calibrated using the rule that appears in between the legs on this long-axis x-ray.

The first angle that we measure is the HKA, that is, the angle in between the line crossing the center of the femoral head to the center of the condyles and the center of the tibial plateau to the center of the talus. Here, this angle is 5° of varus.

We then try to see where the varus is located by measuring 2 angles—the mechanical lateral distal femoral angle (mLDFA) which is remeasured here because of the landmarks that will not precisely define the distal aspect of the femur; this angle is 88°.

We then measured the proximal tibial morphology with the MPTA; we here measured the angle in between the tibial plateau and the center of the interline connecting the center of the spines and the center of the talus; the angle is here 84°.

When this is completely done, we can switch to another analysis of the lower limb based on the Minciaci planning. The Minciaci planning is a projection in between the Mikulicz line before the surgery and after the surgery. The idea is to switch the position of the ankle through a hinge which would be located in the tibia because, here, we intended to do an HTO.

We draw a first line in between the femoral head and the center of the talus; then we projected a second line from the center of the femoral head to the Fujisawa point at the top of the plateau. Here, we intended to have this line passing at 60% of the width of the plateau.

We calculate this using this application to divide the distance in between the width at the Fujisawa point and the global distance, the global width of the tibia. This value here is 45 divided by 77, which is almost 0.6, that is, 60% of the global plateau width, which is what we intended to do in this case.

We then measured the angle in between those 2 points at the ankle level, passing through the hinge that we create, and that would be our shifting point from the preoperative to the postoperative aspect of the ankle. So, this angle measures exactly the correction to be done at the proximal tibia—here 8°.

We then project on the proximal tibia an 8° angle with an 110° cut, which is following the Miniaci publication—the ideal cut to have enough bone above the osteotomy site—and you can see here that we create an angle of 8° and we measure the distance in between the proximal and the distal lines of this angle, to be the only element we have intraoperatively and to be the measure of the opening to create in this opening wedge osteotomy. This measure here is around 9 mm.

We now instruct the software to do all the measures, which were done manually in the last minute, automatically. We are just positioning landmarks such as the center of the femoral head, the external part of the femoral head, the great trochanter, the medial condyle, the lateral condyle, the medial aspect of the tibial plateau, the lateral aspect of the tibial plateau, the lateral border of the tibial plateau, the medial border of the tibial plateau, and finally the lateral and medial aspects of the talus at the ankle.

Those elements will automatically create angle measurements, and you can see here that our mLDFA is 88° and the MPTA is slightly less, 82.2° compared with 84°, and we just double-check to confirm those measures are exactly positioned at the good position. So, we moved a little bit lower in the condyle position, but you can see that the tibia measures and the proximal tibial definition were correctly assessed by the software.

Here, we set our Fujisawa point to 60%, and the last thing to be done is the definition of the osteotomy site. We move the Fujisawa point here to 60% and automatically create the osteotomy. And you can see that the distance measured by the software is 10 mm. This affirmation would be the only one we have intraoperatively—during the 10-mm opening we perform the osteotomy.

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