The effect of the distance between the end point of the osteotomy and the lateral cortex on the lateral cortical hinge fracture in medial opening-wedge high tibial osteotomy

Larger lateral hinges increase the probability of Takeuchi type II and III fractures in high tibial osteotomy

PURPOSE

Lateral hinge fractures are the main complications in the high tibial osteotomy to treat varus deformities. The aim of present study is to answer the question whether the lateral hinge length (H) has an effect on the type of fracture and required force during the opening in high tibia osteotomy. It was hypothesized in this comparative research that extending the hinge length increased opening force and probability of a type II and type III fractures.

METHODS

A monoplanar medial open wedge osteotomy with different intact hinge lengths varying from 9 to 32 mm was performed in 20 ostrich bones. A biomechanical experiment using unidirectional tensile testing apparatus was performed to open the wedge, and the required force was increased until a 10 mm opening was reached; then, the presence of fracture in the lateral cortex and its direction were evaluated. Lateral hinge fracture type based on direction was classified as suggested by Takeuchi et al.

RESULTS

Fracture that grows along the osteotomy line (type I) was observed in 4 samples with the mean hinge length (H) of 11 ± 1.54 mm. For seven bones with Takeuchi fracture type II, with downward crack propagation, the mean H was 16 ± 3.36 mm. For the mean H of 25 ± 6.53 mm, the crack propagated upward to the cutting path, displaying a Takeuchi type III fracture in seven samples. The statistical analysis showed that the fracture type significantly depends on the hinge length (P value < 0.05). Also, the mean opening force significantly increased with hinge lengthening (P value < 0.05). The peak forces at crack initiation were 41.8 ± 21.9, 115.2 ± 41.5, and 167 ± 135.3 N, respectively, for the fracture types I, II, and III samples.

CONCLUSION

The lateral cortical hinge length was significantly associated with hinge fracture type. The experimental tests indicated that the hinge lengthening increases the risk of type II and III fractures, as classified by Takeuchi.

Editorial Commentary: Risk of Lateral Hinge Fracture After Knee Medial Opening-Wedge High Tibial Osteotomy Can Be Reduced With Osteotomy at the Level of the Proximal Tibiofibular Joint and Gap Width of No Larger Than 11 mm

Medial opening-wedge high tibial osteotomies are commonly performed to treat varus deformity and medial compartment osteoarthritis of the knee in active younger individuals. A common complication of this procedure is the development of a lateral hinge fracture. This can occur both acutely and with a delayed presentation. There are many considerations to reduce this fracture, including biplanar versus monoplanar osteotomy, amount of correction/gap width, level of the osteotomy, and lateral cortical distance of the osteotomy. To best reduce the risk of a lateral hinge fracture, place the level of the osteotomy at the level of the proximal tibiofibular joint, and maintain a gap width of no larger than ∼11 mm.