Ligament Balancing in Total Knee Arthroplasty Section 4 | Instrumentation techniques and ligament releases

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4 – Overview TKA instrumentation techniques [Fig 4.0.1] Ligament balancing has a typical position in each of the three different instrumentation techniques.

4 – Overview TKA instrumentation techniques [Fig 4.0.2] A fixed bearing knee prosthesis.

4.1 – The classical femur first technique General principles [Fig 4.1.1a] Alignment in extension.

4.1 – The classical femur first technique General principles [Fig 4.1.1b] Alignment in flexion.

4.1 – The classical femur first technique Distal cut first [Fig 4.1.2] The distal femoral cut is set by intramedullary alignment. The lateral distal femoral angle (LDFA) serves as a plausibility check.

4.1 – The classical femur first technique 4-in-1 femoral resection [Fig 4.1.3a] Set the orientation of the cutting block with help of the femoral section of the AP-axis. In this example, a fixed 3° external rotation referenced to the posterior condylar line would also have equaled a neutral rotation orientation, as the posterior condyles were not deformed.

4.1 – The classical femur first technique 4-in-1 femoral resection [Fig 4.1.3b] Utilizing an anterior reference guide to position the 4-in-1 resection block. The posterior condyles are the second reference point: for component sizing and also to assess rotational alignment (varus-valgus alignment in flexion) of the component.

4.1 – The classical femur first technique Proximal tibial resection [Fig 4.1.4] Here, the proximal tibia resection block is aligned by extramedullary instrumentation.

4.1 – The classical femur first technique Osteophyte removal [Fig 4.1.5a] Resect the residual osteophytes from the femoral margin.

4.1 – The classical femur first technique Osteophyte removal [Fig 4.1.5b] Next, resect the residual osteophytes from the tibial margin.

4.1 – The classical femur first technique Osteophyte removal [Fig 4.1.5c] Remove osteophytes from the posterior condyles.

4.1 – The classical femur first technique Osteophyte removal [Fig 4.1.5d] Also remove osteophytes from hidden capsular pouches, like the subpopliteal recess (beneath the popliteal tendon) in this example.

4.1 – The classical femur first technique Insert trials and test joint stability [Fig 4.1.6] Assess ligament stability in flexion and extension.

4.2 – Femur first technique: advantages and watch outs Advantages of technique [Fig 4.2.1a] The femur first technique has a reliable alignment when the landmarks are well defined.

4.2 – Femur first technique: advantages and watch outs Advantages of technique [Fig 4.2.1b] This technique also restores the joint line due to the measured resection principle.

4.2 – Femur first technique: advantages and watch outs Advantages of technique [Fig 4.2.1c] The femur first technique allows the removal of all osteophytes that might interfere with ligament balancing.

4.2 – Femur first technique: advantages and watch outs Advantages of technique [Fig 4.2.1d] Trials are excellent for assessing ligament stability and the effects of ligament releases.

4.2 – Femur first technique: advantages and watch outs Watch outs: Difficult landmark identification [Fig 4.2.2] In some cases, anatomical landmarks can be difficult to define.

4.2 – Femur first technique: advantages and watch outs Watch outs: Possibility of gap mismatch [Fig 4.2.3a] Gap mismatch between extension and flexion gaps is possible due to independent distal and posterior femoral bone cuts.

4.2 – Femur first technique: advantages and watch outs Watch outs: Possibility of gap mismatch [Fig 4.2.3b] The distal femur (and chamfer cuts) can be moved proximally to increase the extension gap. Then a thicker inlay can be inserted.

4.2 – Femur first technique: advantages and watch outs Watch outs: Possibility of gap mismatch [Fig 4.2.3c] A larger femoral component can reduce the size of the flexion gap.

4.2 – Femur first technique: advantages and watch outs Watch outs: Ligament imbalance especially in flexion [Fig 4.2.4a] In some cases an extensive ligament release can be necessary to balance the knee in extension.

4.2 – Femur first technique: advantages and watch outs Watch outs: Ligament imbalance especially in flexion [Fig 4.2.4b] These releases also detach all the flexion stabilizers, so the knee will be unstable in flexion.

4.3 – The Classical tibia first technique General principles [Fig 4.3.1] Balanced ligaments guide the bone cuts in the tibia first technique.

4.3 – The Classical tibia first technique Osteophytes removal and ligament balancing [Fig 4.3.2a] Remove osteophytes in the first step of the tibia first technique.

4.3 – The Classical tibia first technique Osteophytes removal and ligament balancing [Fig 4.3.2b] Balanced ligaments are needed to guide the bone cuts in the classical tibia first technique. Therefore ligament balancing is performed early.

4.3 – The Classical tibia first technique Proximal tibial cut [Fig 4.3.3a] Extramedullary tibial alignment to adjust the correct slope. The sagittal mechanical axis of the tibia (reference axis) is tilted by approximately 3° to the anterior border of the tibia.

4.3 – The Classical tibia first technique Proximal tibial cut [Fig 4.3.3b] In the tibia first technique, resect a sufficient amount of tibial bone. This avoids the potential error of shifting the joint line proximally.

4.3 – The Classical tibia first technique Femoral sizing and posterior femoral cut [Fig 4.3.4a] Determine the proposed size of the femoral component using an anterior referencing system.

4.3 – The Classical tibia first technique Femoral sizing and posterior femoral cut [Fig 4.3.4b] Lift the femur and let the ligaments guide it into a rotational position in which the ligament tension is equal. This will ensure balanced bone gaps.

4.3 – The Classical tibia first technique Femoral sizing and posterior femoral cut [Fig 4.3.4c] Resect the posterior condyles to create the flexion gap.

4.3 – The Classical tibia first technique Distal femoral cut and residual cuts [Fig 4.3.5a] Measure the height of the flexion gap with spacers.

4.3 – The Classical tibia first technique Distal femoral cut and residual cuts [Fig 4.3.5b] Position the distal cutting block so that an identical spacer would fit into the extension gap.

4.3 – The Classical tibia first technique Distal femoral cut and residual cuts [Fig 4.3.5c] Resect the distal femur to create the extension gap.

4.3 – The Classical tibia first technique Distal femoral cut and residual cuts [Fig 4.3.5d] Finish the residual bone cuts on the femur.

4.4 – Tibia first technique: advantages and watch outs Advantages of technique [Fig 4.4.1a] Tibia first technique: can lead to more internal rotation of the femur than landmark-oriented technique, but creates a flexion gap parallel to the functional axis of rotation.

4.4 – Tibia first technique: advantages and watch outs Advantages of technique [Fig 4.4.1b] Tibia first technique: the posterior and distal bone cuts of the femur are always of identical height, because the extension gap is created depending on the height of the flexion gap (dependent bone cuts).

4.4 – Tibia first technique: advantages and watch outs Advantages of technique [Fig 4.4.1c] Tibia first technique: the posterior and distal bone cuts of the femur are always of identical height, because the extension gap is created depending on the height of the flexion gap (dependent bone cuts).

4.4 – Tibia first technique: advantages and watch outs Watch outs: Shifting the joint line [Fig 4.4.2a] A prosthetic knee should reproduce the original joint line of the natural knee in extension to allow the correct function of the soft tissues.

4.4 – Tibia first technique: advantages and watch outs Watch outs: Shifting the joint line [Fig 4.4.2b] A prosthetic knee should reproduce the original joint line of the natural knee also in flexion to allow the correct function of the soft tissues.

4.4 – Tibia first technique: advantages and watch outs Watch outs: Shifting the joint line [Fig 4.4.2c] Shifting the joint line proximally in extension and, as shown, anteriorly in flexion positions the patella too low in relation to the joint line.

4.4 – Tibia first technique: advantages and watch outs Watch outs: Shifting the joint line [Fig 4.4.2d] Shifting the joint line proximally in extension, as shown, and anteriorly in flexion positions the patella too low in relation to the joint line.

4.4 – Tibia first technique: advantages and watch outs Watch outs: Shifting the joint line [Fig 4.4.2e] Mid-flexion instability: from early flexion onward the thicker inlay cannot compensate for the malpositioning of the component.

4.4 – Tibia first technique: advantages and watch outs Watch outs: Shifting the joint line [Fig 4.4.2f] Too conservative a cut of the proximal tibia can lead to shifting the joint line proximally. Knee shown in flexion.

4.4 – Tibia first technique: advantages and watch outs Watch outs: Shifting the joint line [Fig 4.4.2g] Too conservative a cut of the proximal tibia can lead to shifting the joint line proximally. Knee shown in extension.

4.4 – Tibia first technique: advantages and watch outs Watch outs: Shifting the joint line [Fig 4.4.2h] Shifting the joint line distally in extension and, as shown, posteriorly in flexion positions the patella too high in relation to the joint line.

4.4 – Tibia first technique: advantages and watch outs Watch outs: Shifting the joint line [Fig 4.4.2i] Shifting the joint line distally in extension, as shown, and posteriorly in flexion positions the patella too high in relation to the joint line.

4.4 – Tibia first technique: advantages and watch outs Watch outs: Shifting the joint line [Fig 4.4.2j] Mid-flexion contracture: from early flexion onward the inlay is relatively too thick for the malpositioning of the component.

4.4 – Tibia first technique: advantages and watch outs Watch outs: Ligament releases and femoral malrotation [Fig 4.4.3a] Extensive medial releases: the femur rotates too much leading to an externally sloped transepicondylar axis.

4.4 – Tibia first technique: advantages and watch outs Watch outs: Ligament releases and femoral malrotation [Fig 4.4.3b] Not releasing an abnormally tight superficial MCL: too much internal rotation of the femur leading to an internally sloped transepicondylar axis.

4.4 – Tibia first technique: advantages and watch outs Watch outs: ligament balancing only in extension [Fig 4.4.4] Balanced ligaments are needed to guide the bone cuts in the classical tibia first technique. Therefore ligament balancing is performed early.

4.5 – The extension gap first technique General principles [Fig 4.5.1] Extension gap first technique: Ligament balancing after creating the extension gap.

4.5 – The extension gap first technique Proximal tibial cut [Fig 4.5.2a] Orientate the dorsal slope of the tibial cut on the mechanical tibial axis.

4.5 – The extension gap first technique Proximal tibial cut [Fig 4.5.2b] Monitor the correct varus/valgus orientation by using the extramedullary alignment rod.

4.5 – The extension gap first technique Proximal tibial cut [Fig 4.5.2c] To avoid an undesired proximal shifting of the joint line, ensure the tibial cut is substantial enough.

4.5 – The extension gap first technique Proximal tibial cut [Fig 4.5.2d] Recheck the proximal tibia cut.

4.5 – The extension gap first technique Preliminary distal femoral cut [Fig 4.5.3a] In some cases of distal femoral deformity the correct entry point for opening the intramedullary canal is not identical with the area of the intercondylar notch.

4.5 – The extension gap first technique Preliminary distal femoral cut [Fig 4.5.3b] The correct entry point allows the IM-rod to be inserted fully. The distal cutting block is set according to the measured AMA.

4.5 – The extension gap first technique Preliminary distal femoral cut [Fig 4.5.3c] An incorrect entry point interferes with the optimal position of the IM-rod. The valgus angle of the distal cutting block will need to be adjusted.

4.5 – The extension gap first technique Preliminary distal femoral cut [Fig 4.5.3d] In the extension gap first technique the distal femur is not resected at the final level at the beginning.

4.5 – The extension gap first technique Preliminary distal femoral cut [Fig 4.5.3e] Instead the distal femur is deliberately under-resected, in the extension gap first technique, to obtain a preliminary distal cut.

4.5 – The extension gap first technique Ligament balancing [Fig 4.5.4a] Spacers used in the “tight” technique disclose even minor asymmetries of the extension gap.

4.5 – The extension gap first technique Ligament balancing [Fig 4.5.4b] After adequate ligament release a perfect spacer fit means a symmetrical extension gap.

4.5 – The extension gap first technique Determine femoral rotation [Fig 4.5.5a] Ligament-guided technique: the femur is lifted up from the tibia and rotated according to the resulting ligament tension.

4.5 – The extension gap first technique Determine femoral rotation [Fig 4.5.5b] The size and A/P-position of the femoral component can be adjusted continuously with anterior referencing.

4.5 – The extension gap first technique Determine femoral rotation [Fig 4.5.5c] Alternatively the femoral rotation can be determined from anatomical landmarks.

4.5 – The extension gap first technique Posterior condylar resection [Fig 4.5.6] Create the definite flexion gap by resecting the posterior condyles.

4.5 – The extension gap first technique Flexion gap verification [Fig 4.5.7] The flexion gap is assessed for symmetry and equal ligament tension. The ligaments are tensioned by the thickest spacer possible.

4.5 – The extension gap first technique Flexion gap transfer onto extension gap [Fig 4.5.8] Transferring the flexion gap height onto the extension gap: the preliminary distal cut is transformed into a final distal cut.

4.5 – The extension gap first technique Extension gap control and final preparation [Fig 4.5.9a] Verify the extension gap is identical to the flexion gap: test with the thickest red spacer in the “tight” technique.

4.5 – The extension gap first technique Extension gap control and final preparation [Fig 4.5.9b] Complete residual femoral bone cuts and preparation of the proximal tibia: test the result with trials.

4.6 – Extension gap first technique: advantages and watch outs Advantages of technique [Fig 4.6.1a] The combination of preliminary distal femoral cut and “tight” spacer technique allows for smart ligament balancing.

4.6 – Extension gap first technique: advantages and watch outs Advantages of technique [Fig 4.6.1b] Ligament guided technique for femoral rotation: flexion gap will be parallel to the functional axis of rotation.

4.6 – Extension gap first technique: advantages and watch outs Advantages of technique [Fig 4.6.1c] Determining femoral rotation: rely on ligament guided rotation in cases without or just with moderate ligament releases.

4.6 – Extension gap first technique: advantages and watch outs Advantages of technique [Fig 4.6.1d] Determining femoral rotation: use landmark oriented instruments in cases with advanced ligament releases

4.6 – Extension gap first technique: advantages and watch outs Advantages of technique [Fig 4.6.1e] Extension gap first technique: the extension gap, as shown, is created depending on the height of the flexion gap (dependent bone cuts).

4.6 – Extension gap first technique: advantages and watch outs Advantages of technique [Fig 4.6.1f] Extension gap first technique: the extension gap is created depending on the height of the, as shown, flexion gap (dependent bone cuts).

4.6 – Extension gap first technique: advantages and watch outs Watch outs: Shifting of joint line [Fig 4.6.2a] Too conservative cut of the proximal tibia: leads to over-resection of the posterior condyles. Result: the femoral component is positioned too far proximally. Knee shown in flexion.

4.6 – Extension gap first technique: advantages and watch outs Watch outs: Shifting of joint line [Fig 4.6.2b] Too conservative cut of the proximal tibia: leads to over-resection of the posterior condyles. Result: the femoral component is positioned too far proximally. Knee shown in extension.

4.6 – Extension gap first technique: advantages and watch outs Watch outs: Ligament balancing only in extension [Fig 4.6.3] Ligament balancing only in extension can be affected by posterior osteophytes. These shorten the posterior capsule and diminish the size of the extension gap.