A careful patient history is always important but may be even more so in the case of treating a patient with valgus knee arthritis. Patients may report slow, steady symptom progression occurring over years, whereas a more rapid progression raises concerns for gross incompetence of structures on the medial side of the knee. A history can also provide an etiology of the valgus angulation be it from prior trauma or lateral meniscectomy. In both instances, previous incisions should be accounted for in the preoperative plan.

While physical examination is important in diagnosing osteoarthritis, it is critical to understanding and planning for surgery. The following steps are part of our critical examination of patients being evaluated for end-stage arthritis. The patient’s gait should be routinely assessed. The range of motion is measured, and the presence or absence of any flexion contracture should be noted as patients with a preoperative flexion contracture in addition to valgus angulation are at much higher risk for postoperative peroneal nerve palsy.⁴ Patellofemoral articulation is evaluated along with the status of the extensor mechanism; assessment of the collaterals in full extension, mid-flexion, and 90° of flexion will provide a more complete assessment of the ligaments, eliminating the tight posterior capsule which may provide a false sense of stability. The ability to correct the valgus deformity is also noted. This information is important as it provides the surgeon an indication as to whether the angulation will be easily correctable (full correction obtained on examination), require releases (partially correctable), or may require a more extensive release and possibly the use of a constrained prosthesis in the setting of fixed valgus angulation. The assessment is concluded with a thorough neurovascular examination. When treating valgus knee arthritis with primary knee arthroplasty, the risk of peroneal nerve palsy exists; sensory and motor function of the superficial and deep peroneal nerves should be assessed and documented. Additionally, as in all patients, assessment of the back, hips, and feet should be performed. Patients with valgus angulation will often have a pes planovalgus deformity of the foot.⁵,²⁴ There is no consensus on whether the foot and ankle deformities should be addressed prior to knee arthroplasty. Most would agree that the surgeon and patient should consider which joint is more symptomatic and if the hindfoot angulation is flexible or fixed. Several studies have documented conflicting reports of alterations in the mechanical axis after correction of knee varus or valgus angulation after a total knee arthroplasty. In some instances where a flexible foot deformity exists there may be sufficient correction through the knee to affect ankle or foot alignment, and may be performed first.⁶,⁷

However, contrary to this, Meding et al highlighted a series of total knee arthroplasty failures related to uncorrected pes planus deformities.⁸ The degree of expected correction, risk for wound complications, expected compliance with foot and ankle orthosis, and
concern for longevity of the implant should all be factors considered when planning total knee arthroplasty in this situation.

Standard weight-bearing and flexion anteroposterior, lateral, Merchant, and alignment radiographs are obtained. Fluoroscopic examination or stress radiographs may provide more information as to the degree of correction obtainable but are not routinely done at our institution. The anteroposterior (AP) radiographs are critically evaluated for deformity, joint space narrowing, osteophytes, cysts, and subchondral sclerosis (Fig. 44-2A to D). In certain instances, the AP view may underrepresent the degree of wear present which may only be seen on the lateral view. On the lateral view, the lateral femoral condyle is evaluated, which may demonstrate possible hypoplasia (Fig. 44-1C) or a large posterolateral defect in the tibia may be evident.

Templating, often used for sizing of components, can be extremely useful in planning bony resections (Fig. 44-2E) and can provide additional information regarding restoration of mechanical alignment. A line is drawn down the femoral and tibial shafts. A perpendicular line to the tibial shaft line is drawn at the level of the more involved tibial plateau (typically the lateral tibial plateau). This line represents the anatomic and mechanical tibial axis as both coincide which gives the surgeon an estimation as to the amount of tibial resection on the lateral and medial aspects of the tibial plateau. On the femoral side, another horizontal line is drawn with 3° to 5° of valgus alignment from the anatomic axis vertical femoral line. This measurement allows for correction of the mechanical axis. Typically, this line passes just medial to the center of the knee which is a starting point for an intramedullary guide in varus knees. However, particular attention should be paid to the femoral starting site which may need to be moved more lateral to avoid unintentional entry into the medial cortex of the femoral shaft when using an intramedullary guide.

The lateral view is commonly used for sizing purposes. Keeping posterior osteophytes in mind, the posterior aspect of the femoral condyles is outlined and used for sizing. The lateral views are especially important if the surgeon is considering the use of stems in the surgical construct (Fig. 44-2F).

In preparation for a successfully executed total knee arthroplasty of the valgus knee, it is important to give some consideration to implant selection. Excellent results can be achieved utilizing a cruciate retaining implant when operating on a valgus knee. Cruciate retaining implants are bone conserving and have an excellent track record. Choosing an unconstrained implant may limit the perioperative risks for the patient due to smaller bone resection; it may also reduce blood loss and surgery time.⁹ However, the posterior stabilized implant (cruciate sacrificing) offers many advantages as the resection of the posterior cruciate ligament (PCL) allows the surgeon to bypass a major deforming force of the valgus knee and can make balancing the knee considerably easier. If balance is unable to be achieved, a constrained implant should always be available. It should be noted that most posterior stabilized implants do not offer varus and valgus constraint. The use of constrained implants in the setting of severe valgus knee deformity (often defined as > 15°) has been well studied in the literature and found to be successful.¹⁰ However, constrained and stemmed implants increase intramedullary material; the preparation for these implants can, in turn, increase the risk of periprosthetic fractures. Another consideration is the financial savings offered by using primary implants. Anderson et al described using constrained condylar implants without stems to decrease cost with no adverse effects in the short- and mid-term results.¹¹ However, long-term follow-up is necessary to evaluate for potential aseptic loosening. Nonetheless, when increased constraint is necessary, one option is to use stemmed, constrained condylar knees, which have shown excellent long-term outcomes. In general, a condylar constrained prosthesis is chosen if medial or lateral laxity greater than 3 to 5 mm is detected after concerted effort to obtain balance (Fig. 44-3A to F).¹² Constrained condylar designs are useful for instability where a collateral ligament is still present

although lax; they typically provide stability allowing for only 1° to 2° of accepted laxity. However, in cases where the collateral ligaments are absent or damaged and there is significant bone loss (i.e., rheumatoid arthritis, Charcot arthropathy), a rotating hinge device may provide additional and necessary stability (Fig. 44-4A to D). Although loads to the bone/implant interface will be greater in these designs, overall results have been encouraging.¹³ While all implant constraints have been shown to be usable in the valgus knee, surgeons should understand the need for added constraint to achieve balance within the knee and have implants available to make necessary adjustments intraoperatively.

The patient is brought into the operating room and transferred onto a regular operating table. We prefer spinal anesthesia, typically 0.5% bupivacaine, at our institution unless contraindicated. If utilizing femoral and sciatic nerve blocks, one may consider delaying dosing of the sciatic catheter until after completion of the surgery and postoperative assessment of peroneal nerve function. Once spinal anesthesia is administered, the patient is positioned supine on the operating table. A thigh tourniquet is placed and the operative site is shaved. Multiple knee positioning devices exist depending on surgeon preference. The senior author prefers keeping the leg/foot free and uses the lateral thigh post at the level of the tourniquet to prevent excessive external rotation during the course of surgery. A flat foot positioner is also used at the distal end of the table at a level that coincides with 90° flexion of the knee. The foot rests on top of this post during steps that require flexion of the knee.

Once the patient is positioned on the operating table, the operative leg is prepped and draped in the usual sterile manner. Prophylactic intravenous (IV) antibiotics and IV tranexamic acid are administered prior to incision. If there is a contraindication to IV tranexamic acid, a topical form is injected into the wound at the end of the procedure after capsular closure and prior to skin closure. An esmark is used to exsanguinate the limb and the tourniquet is inflated to 250 mmHg. The authors prefer a medial parapatellar approach, although a lateral parapatellar approach has been described with success. There are certain unique challenges associated with the valgus knee which have been extensively cited in the literature, such as surgeon unfamiliarity, obtaining proper rotational alignment, soft-tissue balancing, and patellar tracking. The incision, which extends from 4 to 5 cm above the superior pole of the patella to 2 to 3 cm distal and just medial to the tibial tubercle, is marked. The size of the incision varies depending on the patient’s body habitus; knees with a bigger soft-tissue envelope require longer incisions for safe and effective exposures.