*4.2.2 Tensioning of medial structures*

As described by Krackow et al. [17], when the MCL is attenuated and there is a residual medial laxity, the authors suggest tightening of the medial structures. The advancement of the MCL from the epicondyle or a division and imbrication in order to tighten, it can be performed.

### *4.2.3 The fibular nerve dilemma*

Fibular nerve palsy (FNP) is a feared complication after valgus TKA. The reported incidence of FNP after valgus TKA in the literature ranges between 0.3% and 9.5%. Injury of the Fibular nerve can be caused by indirect damage due to stretch or ischemia after correction, or by direct injury due to laceration during lateral soft tissue release. As FNP has serious consequences, some orthopedic surgeons advocate to prevent this complication by a concomitant fibular nerve release (FNR). Due to the limited number of studies investigating FNR, no consensus has yet been reached on the value and indication of the procedure. A systematic review demonstrated no significant differences in FNP rate between valgus TKA with and without FNR (2.4% vs 2.1%) [18]. Therefore, the authors of this chapter do not recommend the routine use of FNR.

#### **4.3 Bone resection**

Valgus deformity has particularities that need to be recognized so that bone cuts can be made properly. In most cases, the origin of the deformity is located in the distal femur, as opposed to the varus deformity. Lateral condyle hypoplasia is frequently present and needs to be recognized, as it directly interferes with several parameters of femoral bone cuts. A smaller number of cases may have lateral tibial plateau sinking, either due to fracture sequelae or in very advanced cases with deformity > 20° and MCL insufficiency.

Extra-articular deformities such as external torsion of the tibia and remodeling with valgus deviation of the femoral and tibial shafts may also coexist [19].

### *4.3.1 Tibial resection*

We recommend that the first bone cut is the tibial one, parallel to the ground. The main reason is that we can use the tibia as a parameter for the posterior cut of the femur through the gap balancing technique, in which the cut is performed parallel to the tibial cut with the knee at 90° under symmetrical soft tissue tension. This is

## *Total Knee Arthroplasty in Valgus Knee DOI: http://dx.doi.org/10.5772/intechopen.109573*

important because, due to hypoplasia of the lateral condyle, we cannot rely on the classic parameter of 3° of external rotation in relation to the posterior condyles, which will be discussed later.

A marked valgus deformity of the tibial diaphysis is frequently observed in valgus knee, which makes it impossible to use an intramedullary guide for the tibia in most cases. Therefore, we recommend the use of the extramedullary guide for all cases. In addition, tibial cutting guides are usually sided (left or right). In these cases, it will be necessary to use the guide on the opposite side. Another important detail of this step is the amount of bone to be cut. Traditionally, in varus knee prosthesis, 9–10 mm of bone can be removed using the healthy plateau as a parameter. However, the healthy tibial plateau in valgus knee is the medial plateau. It turns out that the medial plateau is 3 mm more distal than the lateral plateau. Therefore, we must discount this 3 mm when making the cut, otherwise we will inadvertenltly cut more tibia than ideal. Therefore, make the tibial cut 6 or 7 mm from the medial plateau.

## *4.3.2 Femural resection*

Next, we will make the distal cut of the femur. Instead of the 7° of valgus traditionally used in varus knees, we used 5° in the distal cut of the femur, in order not to under-correct the deformity. The surgeon may also choose to use the exact difference

#### **Figure 1.**

*Tips and tricks for appropriate bone resection in valgus TKA. (A) Weight-bearing knee radiography demonstrating lateral condyle hypoplasia and the adjusted entry point for IM guide at the medial condyle (red arrow), in the prolongation of the anatomical axis of the femur; (B) determination of the rotation of the femoral component by the Whiteside line (yellow), parallel to the transepicondylar axis. Do not use the support guide on the posterior condyles; (C) When determining the rotation of the tibial component, 1 centimeter medial to the TTA, the less experienced surgeon with the Keblish approach must be careful because the tibia is being viewed "in a mirror."*

measured between the anatomical and mechanical axis of the femur in the preoperative panoramic X-ray. Caution should be taken with the entry point of the intramedular guide. Because of hypoplasia of the lateral femoral condyle, the entry point must be medialized, sometimes not above the intercondylar notch as usually done in varus cases, but in the medial femural condyle.

Regarding the adjustment of the femoral rotation, one more point of attention: The existence of hypoplasia of the lateral femoral condyle is very common. Therefore, the use of a guide based on the posterior condylar line will incur in excessive internal rotation of the femoral component. If the technique used is measured resection that considers the anatomical points, the correct way is to base it on the trans-epicondylar axis or on the Whiteside line. An alternative, as already described, is to use the gap balancing technique in this step.

**Figure 1** brings some tips and tricks to keep in mind as they are common causes of errors.
