We commonly plan the osteotomy as described by Dugdale and colleagues ⁵ with a mild (3 to 5 degrees) valgus overcorrection (Fig. 62-1). After the correction, the mechanical axis (the line connecting the center of the femoral head with the center of the ankle joint) should pass through a point located at 62.5% of the tibial width, as measured from the tip of the medial edge of the proximal tibia. This point lies slightly lateral to the tip of the lateral tibial spine. In planning for opening wedge HTO, one line is drawn from this point to the center of the femoral head, and another line is drawn from this point to the center of the ankle joint. The angle between the two lines represents the angle of correction (α) (see Fig. 62-1). Next, the osteotomy line is measured from medial (approximately 4 cm below the joint line) to lateral (tip of the articular fibular head). This measurement is transferred to both rays of the α angle from the vertex. In this fashion the α angle is defined by two identical segments (equal to the osteotomy length), which are then connected by another line. This line serves as the base of an isosceles triangle and corresponds to the opening that should be achieved medially at the osteotomy site (see Fig. 62-1).

Figure 62-1 Preoperative planning of opening wedge high tibial osteotomy (HTO; see text). A, Anteroposterior view of the knee for the coronal planning. B, Lateral view of the knee for the sagittal planning.

In younger patients without medial compartment arthritis, a more neutral alignment is planned after correction (50% of the tibial width, 0 degrees of mechanical axis).

In performing combined ACL reconstruction and HTO, the sagittal planning is very important. The tibial slope can be decreased with a more posterior plate positioning, to protect the graft (see Fig. 62-1).

Hyperextension deformity is more commonly associated with posterior cruciate ligament (PCL) or posterolateral corner (PLC) injury. However, with ACL failure resulting from hyperextension, increasing the tibial slope will correct the hyperextension; but if the slope is severely increased, this will put the ACL reconstruction at risk. Therefore in individuals with deformity of the tibial slope (<6 degrees), a mild correction of the slope is indicated. If the slope is normal (>6 degrees), it should be left as is.

Surgical planning is similar for closing wedge HTO. The α angle is calculated as described for opening wedge HTO, but the osteotomy itself is different and entails two cuts. The proximal osteotomy line is usually horizontal and is placed 2 to 2.5 cm distal to the joint line. The proximal and distal osteotomy should define the angle of correction (α). With closing wedge HTO, it is more difficult to accurately change or correct the tibial slope, which is usually decreased after the procedure.

Surgical Technique

Both opening wedge and closing wedge HTO can be performed, according to surgeon’s preference. Our preferred technique is opening wedge HTO. Also, the choice of the ACL graft and reconstruction technique is a matter of preference of the surgeon.

Surgical Steps

Opening Wedge High Tibial Osteotomy

The surgery is performed with the patient supine on a radiolucent operating table (Box 62-1).^1,3 A lateral post is positioned at the level of the thigh so that the foot can be dropped out of the table and at least 120 degrees of knee flexion can be achieved (Fig. 62-2). Intravenous antibiotic prophylaxis is performed. A tourniquet is placed around the proximal thigh. HTO is performed first. A 5-cm longitudinal incision is made, extending from 1 cm below the medial joint line midway between the medial border of the tubercle and the posteromedial border of the tibia.^1,3 If a hamstring autograft is preferred, harvesting of the graft is performed at this point, to avoid damage to the tendons during proximal tibia exposure. The sartorius fascia is exposed by sharp dissection, and the pes anserinus is then retracted distally with a blunt retractor, exposing the superficial fibers of the medial collateral ligament (sMCL). The distal sMCL insertion is partially detached with a Cobb elevator. A blunt Hohmann retractor is then passed deep to the MCL to protect the posterior neurovascular structures. Next, the medial border of the patellar tendon is identified and retracted laterally with a hook or a second blunt lever. A guidewire is then drilled into the proximal tibia.^1,3 The starting point of the wire is the anteromedial (AM) tibia at the level of the superior border of the tibial tubercle (about 4 cm distal from the joint line). The wire must be inserted aiming toward the tip of the fibular head (1 cm below the lateral articular surface). The guidewire positioning is assessed with fluoroscopy (Fig. 62-3). The tibial osteotomy is performed immediately distal to the guide pin, to protect against proximal migration of the osteotomy into the joint. The slope of the osteotomy in the sagittal plane is critical and should mimic the proximal tibial joint slope.^1,3 A small oscillating saw is used to cut the tibial cortex from the tibial tubercle around to the posteromedial corner under direct vision. Thin, flexible osteotomes are then used to advance the osteotomy to within 1 cm of the lateral tibial cortex (Fig. 62-4). This is achieved with use of intermittent fluoroscopy and graduated osteotomes.⁶ The mobility of the osteotomy is checked by gentle manipulation of the leg with a valgus force and encouraged, if needed, by piling up two or three osteotomes.^1,3 Graduated wedges are then engaged into the osteotomy and advanced slowly until the desired opening has been achieved (Fig. 62-5). Once the calculated preoperative correction has been achieved, a long alignment rod is used to check the mechanical axis. The rod is centered over the hip and ankle joints and, according to the preoperative planning, should lie at 62.5% or 50% of the tibial width, as measured from medial to lateral. The sagittal plane correction should also be assessed by fluoroscopy and by looking carefully at the size of the osteotomy opening. Considering the triangular shape of the tibia, if the opening at the level of the AM tibia is half the size of the opening at the level of the posteromedial tibia, the preexisting slope is maintained (Fig. 62-5B). The wedges (and the plate) can be moved anterior or posterior, according to the correction planned on the sagittal plane.