0
    505
    views

    PRACTICE PEARLS: Technique for Managing the Valgus Knee

    Over the years, several techniques have been developed for managing valgus deformity in total knee arthroplasty (TKA) procedures.

    At ICJR’s Instructional Course at the 9th Congress of the Chinese Association of Orthopaedic Surgeons, Chitranjan S. Ranawat, MD, from Hospital for Special Surgery in New York, provided an overview of these techniques and then described in detail his inside-out technique for soft tissue release in the valgus knee.

    There are 2 elements to the deformity of the valgus knee: bone loss (hypoplastic lateral femoral condyle and lateral tibial plateau) and soft tissue changes (tight lateral structures and elongated medial structures). These deformities have been classified into 2 types:

    • Type I deformity is entirely due to bone loss.
    • Type II deformity has both bone loss laterally and elongated medial soft tissues.

    Treating a knee with a Type II deformity is a much more complex procedure than treating a Type I deformity, Dr. Ranawat said.

    The basic principles of TKA are to:

    • Restore the joint alignment in 3 planes
    • Restore the joint line
    • Restore joint stability
    • Restore the range of motion and patellofemoral kinematics
    • Use appropriate fixation techniques

    The surgeon has several options for setting the rotational alignment of the femoral component, Dr. Ranawat said. His preference is to set the femoral component parallel to the tibial cut, but the epicondylar axis, Whitesides line, and fixed amount of external rotation (2° to 3°) can also be used.

    In 80-85% of less-deformed knees, these axes are coplanar, but in a knee with fixed deformity and elongated medial soft tissues, Dr. Ranawat believes the axis parallel to the tibial cut is more accurate.

    When correcting a valgus deformity, the surgeon should keep these points in mind:

    • Restoration of the frontal alignment occurs with the proximal tibia cut at 90° and the distal femur cut at 3° to the anatomical axis of the femur.
    • Soft tissue balancing is performed in extension.
    • Flexion gap stability is achieved with bone cuts, in the parallel to tibial cut technique
    • Avoid soft tissue balancing in flexion.

    Dr. Ranawat warned attendees to cut less bone in a knee with a Type II deformity. Because the soft tissues are elongated, the knee will be loose in both flexion and extension if the standard amount of bone is removed.

    To release tight lateral structures Dr. Ranawat developed the Inside-out technique, with releases done in the following order:

    • Complete release of the posterior cruciate ligament
    • Release the posterolateral capsule up the posterior border of the iliotibial band at the level of the tibial bone cut with the knee in extension
    • “Pie-crust” release of the iliotibial band

    The goal of the technique, Dr. Ranawat said, is to create a rectangular extension space.

    Early techniques for managing the soft tissues in a valgus knee included the complete release of all lateral structures [1], the release of selected lateral structures [2] and, advancement of the elongated medial soft tissues. [3] The use of a constrained implant was also described. [4]

    These early techniques had limitations, Dr. Ranawat said, in that they were unable to produce the desired outcome in a consistent manner and were associated with a high rate of early- and late-onset instability.

    Dr. Ranawat developed is soft-tissue release technique to minimize these limitations. A 2005 study [5] showed this inside-out technique provides good correction of the deformity with no delayed instability after a follow-up of up to 15 years.

    Click the image above to watch Dr. Ranawat’s presentation.

    References

    1. Insall JN, Scott WN, Ranawat CS. The total condylar knee prosthesis. A report of two hundred and twenty cases. J Bone Joint Surg Am. 1979;61:173-80.
    2. Whiteside LA: Selective ligament release in total knee arthroplasty of the knee in valgus. Clin Orthop 367:130, 1999
    3. Healy WL, Iorio R, Lemos DW. Medial reconstruction during total knee arthroplasty for severe valgus deformity. Clin Orthop Relat Res. 1998;(356):161–169.
    4. Stern SH, Moeckel BH, Insall JN. Total knee arthroplasty in valgus knees. Clin Orthop Relat Res. 1991;273:5-8.
    5. Ranawat AS, Ranawat CS, Elkus M, Rasquinha VJ, Rossi R, Babhulkar S. Total knee arthroplasty for severe valgus deformity. J Bone Joint Surg Am. 2005;87(Suppl 1(Pt 2)):271–284.