How to achieve an optimal alignment in medial opening wedge high tibial osteotomy?

Abstract

Medial opening wedge high tibial osteotomy (MOWHTO) is a widely used surgical treatment option for medial compartmental osteoarthritis with varus deformity. It is important that proper lower limb alignment is achieved. However, there has been no consensus about an optimal alignment in MOWHTO. Most studies suggest that achieving valgus alignment is necessary, and recent studies support slight valgus mechanical alignment of less than 3° of mechanical femorotibial angle. Overcorrection and undercorrection is not recommended for achieving good surgical outcomes. To prevent undercorrection and overcorrection in MOWHTO, the method of placing the weight-bearing line in the target range must be precise. There are several ways to place a weight-bearing line within the target range. While the most important factor for a successful MOWHTO is achieving an ideal mechanical axis correction, there are a few other factors to consider, including joint line obliquity, posterior tibial slope, ligament balancing, and patellar height. Several factors exist that lead to undercorrection and overcorrection. Preoperative amount of varus deformity, lateral hinge fracture, and fixation failure can result in undercorrection, while medial soft tissue laxity and the amount of correction angle and target point beyond hypomochlion can result in overcorrection. This study aimed to review the literature on optimal alignment in MOWHTO and report on the factors to be considered to prevent correction errors and how to achieve an optimal alignment.

Keywords: Correction error; High tibial osteotomy; Mechanical axis; Medial opening wedge high tibial osteotomy; Operative planning; Optimal alignment; Overcorrection; Soft tissue laxity; Undercorrection.

Fig. 1

Miniaci’s method and Dugdale’s method. a Miniaci’s method: Line 1 is the planned weight-bearing line. The angle between lines 2 and 3 is the planned correction angle α. b Dugdale’s method: Line 1 runs from the center of the hip joint to the target point of the tibial plateau. Line 2 runs from the center of the ankle joint to the target point of the tibial plateau. The angle between lines 1 and 2 is the planned correction angle β

Fig. 2

Real-size weight-bearing scanogram method. With a full-size radiograph printed on paper, a line is cut along where the osteotomy is going to be performed. The tibia is rotated until the weight-bearing line passed through the target point. Reprinted with permission from Lee DH: The weight-bearing scanogram technique provides better coronal limb alignment than does the navigation technique in open high tibial osteotomy. The Knee. Copyright © 2012 Elsevier B.V. All rights reserved

Fig. 3

Intraoperative method under fluoroscopy guidance with a Bovie cable or radiopaque rod

Fig. 4

The effect of the cortical hinge on the posterior tibial slope. a Posterolateral cortical hinge osteotomy with uneven anterior and posterior gap. b True lateral cortical hinge osteotomy with even anterior and posterior gap

Fig. 5

Correction error due to hinge fracture. a Properly conducted osteotomy and b Lateral hinge fracture. Correction error might be affected by the lateral hinge fracture

Fig. 6

Perioperative change in the soft tissue tension around the knee. a Preoperative standing and supine knee radiographs. b Preoperative and postoperative scanogram. The difference of joint line convergence angle between weight-bearing and supine X-ray implies the possibility of soft tissue tension change after medial opening wedge high tibial osteotomy. The medial joint space is opened, and the lateral joint space is closed by shifting the weight-bearing axis after medial opening wedge high tibial osteotomy. This results in unexpected overcorrection