Varus Knee Deformity
Kapil Mehrotra
Daniel J. Berry
Key Concepts
Balancing the varus knee begins with making bone cuts that restore neutral (or near-neutral) mechanical alignment to the knee, followed by soft tissue management to obtain even (or near-even) soft tissue tension on the medial and lateral sides of the knee.
In the great majority of cases, soft tissue management consists of sequential releases of tight soft tissue structures on the medial side of the knee in an iterative manner.
Overrelease of medial soft tissues is a constant concern and should be avoided to minimize risk of instability.
Constrained implants providing extra varus/valgus stability are reserved for severe cases.
Sterile Instruments and Implants
Sterile Instruments
Routine knee arthroplasty retractors
Periosteal elevator
18-gauge needle
Electrocautery
Small oscillating saw
Implants
Routine knee arthroplasty instrumentation.
In cases with notable bone loss: metal augments to make up for bone deficiencies and implants to protect fixation.
In cases of severe deformity: constrained implants with stems to protect fixation.
Position
Supine on operating table
Tourniquet on the thigh well above area of knee incision
Surgical Approaches
Use the surgeon’s routine preferred knee exposure in most cases: usually this will be medial parapatellar.
In more severe deformities, use medial parapatellar approach even if surgeon usually uses a different exposure for patients with minimal deformity.
 Figure 53.1 ▪ A, Standing weight-bearing knee films. B, Longstanding hip to ankle radiograph to evaluate limb alignment and to use for preoperative planning. |
Preoperative Planning
In addition to performing routine preoperative total knee arthroplasty (TKA) orthopedic and medical evaluation, carefully evaluate the degree to which the varus deformity is correctable with valgus stress and the degree to which lateral structures are stretched out with varus stress. This will provide an idea of the amount of soft tissue balancing that will be required.
Obtain long-standing hip to ankle radiographs to plan the bone cuts required to restore neutral or near-neutral mechanical limb alignment (Figure 53.1A and B).
Measure the tibiofemoral angle (angle created between the anatomic axis of the tibia and femur) to determine the severity of the varus deformity.
Evaluate for medial femoral condyle or medial tibial plateau bone deficiencies.
Identify posterior osteophytes on the lateral radiograph.
Template femoral and tibial component size.
Consider the need for augments, stems, or constrained implants.
Bone, Implant, and Soft Tissue Techniques
Bone Preparation
After routine exposure via medial parapatellar exposure, make bone cuts on femur and tibia per the surgeon’s routine method, either measured resection or flexion gap balancing methods (see Chapters 2, 50, and 51).
Make sure during routine exposure the dissection around the medial proximal tibia is in the subperiosteal plane. This protects the medial collateral ligament (MCL), which can be adherent to medial osteophytes and also provides a good soft tissue sleeve for later repair.
If bone deficiency is present, it is usually of the medial tibia in the varus knee. Make bone cuts to avoid excessive tibial resection. If the medial tibia is notably deficient, plan to fill the deficiency rather than resecting much extra bone. Usually the bone loss will be filled with a medial metal tibial block augment (Figure 53.2A-D). Very mild deficiencies may be filled with cement. Realize some mild bone deficiencies will be removed after resection of medial tibial osteophytes (Figure 53.3A and B).Related posts:
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