Asymmetric, arthritic destruction of the cartilage of the knee joint can lead to an abnormal medial or lateral inclination in limb alignment. Cartilage collapse in the lateral compartment of the knee causes the distal aspect of the femur to lean away from the mid line of the body. This deformity is called “valgus” alignment.
Valgus deformity contributes to unfavorable tensioning of lateral soft-tissue structures. In order to relieve tension in a valgus knee, surgeons typically choose to resect or otherwise release lateral structures (e.g., lateral collateral ligament), to assist in the restoration of appropriate balance and alignment of the joint.
While there are several techniques that can be employed to release soft-tissue, conservative and small corrections may avoid accidental ligament over-release and/or rupture. With that in mind, the “pie-crusting” technique utilizes an 18-gauge needle, or #11 blade, to make small interruptions to localized sections of ligament in a controlled manner. This technique, used in conjunction with feedback from intraoperative sensors, has been shown to be effective in the achievement of balance.1-3
Intraoperative sensors provide surgeons with quantitative feedback regarding soft-tissue balance and intra-articular loading. The following techniques have been suggested to correct several states of imbalance in the valgus knee:
1) Lateral tension in extension only (Asymmetric Imbalance)
In this scenario, the surgeon may notice asymmetric loading during extension with greater lateral tension present. The knee may also present with joint gapping on the medial side during extension. The iliotibial band may also exhibit enough tension to inappropriately induce external rotation on the tibia.
The first lateral structures to consider for release should be the posterior lateral capsule, and/or the arcuate ligament. Palpation of these structures will be necessary to examine tension. Once the release(s) have been made, the surgeon should cycle the leg through the range of motion, several times, to encourage further lengthening of the ligament(s) addressed.
2) Upon re-evaluation, if the surgeon notices that there is still an excess of lateral tension in extension, release of the iliotibial band (ITB) is recommended. Following the release(s), the leg should be cycled again, and loads checked for need of any further release to these structures.2 Lateral tension in flexion only (Asymmetric Imbalance)
In this scenario, the surgeon may notice asymmetric loading during flexion with greater lateral tension. The joint may gap when a valgus stress test is applied, but will not gap during a varus stress test. The structure to target for this deformity is the popliteus. The popliteal fibers should be palpated to assess tension, and released with a pie-crusting technique accordingly. Once the release(s) have been made, the surgeon should cycle the leg through the range of motion, several times, to encourage further lengthening of the ligament(s) addressed.
3) Lateral tension in both extension and flexion (Asymmetric Imbalance)
In this scenario, the surgeon will notice that the lateral compartment exhibits excessive loading through the range of motion. The medial capsule may begin to show gapping in flexion, extension or both. The soft-tissue structures predominantly implicated in lateral tension (that is, the LCL, popliteus, iliotibial band, and lateral posterior capsule) may all feel contracted.
Extension balancing (loads 20 – 40lbf): The first indication for correction should be to release the posterior lateral corner, if in tension. After cycling the leg and rechecking the loads, if needed, the posterior lateral capsule and arcuate complex should be checked for tension and released. Finally, if lateral tension still exists, the fibers of the ITB can be released.
Flexion balancing (loads 20 – 40lbf): If excessive loading is still present, the popliteus should be palpated for tension and released where necessary.
If loading is beyond 40lbf on the lateral side in both extension and flexion, consider recutting the tibia plateau to add more valgus alignment.
VERASENSE: Addressing the Valgus Knee with a Posterior-Lateral Release
Contact OrthoSensor, Inc. for more information on VERASENSE Sensor-Assisted Total Knee Arthroplasty.
Dr. Martin Roche serves as the chief medical officer and is a board member for OrthoSensor, Inc. Dr. Roche also receives royalty payments from OrthoSensor, Inc.
1 Gustke KA, et al. Primary TKA patients with Quantifiably Balanced Soft-Tissue Achieve Significant Clinical Gains Sooner than Unbalanced Patients. Adv Orthop. 2014:628695
2 Gustke K, et al. A New Method for Defining Balance: Promising Short-term outcomes of Sensor-Guided TKA. J Arthroplasty. 2014 May;29(5):955-60
3 Leone, WA. Using Intraoperative Sensing Technology to Guide Revision in the Chronically Painful Knee: A Two-Patient Case Study. ECOR. 2015; 2(2): 77-81.