A Closer Look At The Distal Tibial Osteotomy For Ankle Varus
The correction of her ankle varus and staged lateral collateral ligament stabilization decreased her varus moment upon heel strike, improved her ankle range of motion and decreased her talar tilt. All of these in combination act to neutralize her gait, prevent recurrent ankle sprains and decrease the contact forces acting on the medial talar dome. This will also decrease the likelihood of an ankle fusion in a young, active patient.
A Guide To Indications And Surgical Planning For Distal Tibial Osteotomies
Distal tibial osteotomies, or supramalleolar osteotomies, have been an orthopedic mainstay for the treatment of tibiotalar varus and valgus. Indications for these corrective osteotomies include post-traumatic deformities, ankle deformity secondary to systemic illnesses and idiopathic ankle arthritis.1,2 Distal tibial osteotomies are also indicated in the pediatric population for congenital tibial deformities including physeal growth arrest with concomitant growth disturbances.3
Preoperative surgical planning for tibiotalar deformities and other angular deformities of the lower extremity involves assessing the patient’s gait, and mechanical and anatomic lower extremity axes, as well as obtaining proper radiographs. For the purpose of this case study, the focus remains on the coronal plane deformity.
Assess the tibial mechanical axis on AP and lateral full-length weightbearing radiographs of the operative limb. Then draw the distal tibial articular surface with the angle formed between the tibial mechanical axis, resulting in the tibial-ankle surface angle on an AP view and the tibial-lateral surface angle on a lateral view. The normal tibial-ankle surface angle is approximately 91 to 93 degrees and the normal tibial-lateral surface angle is 80 to 81 degrees.4
Using the standard Ilizarov principles of deformity correction, determine the center of rotation and angulation with the mechanical axes of the tibia and talus. To prevent the need for translation, make the tibial osteotomy at the center of rotation and angulation.5,6 When the center of rotation and angulation is at the level of the joint and with minimal deformity, one can create the osteotomy about 3 to 4 cm proximal to the joint line. One can determine the amount of correction needed, in terms of bone graft width, by the desired tibial-ankle surface angle correction to normal ankle alignment with the following formula:7
tan θ = height of wedge in millimeters / tibial width
What The Literature Reveals On Osteotomies
Medial opening wedge osteotomies are the most common procedures for ankle varus but the literature is scarce regarding long-term outcomes.
Stamatis and colleagues retrospectively reviewed 13 cases of either distal tibial medial closing wedge osteotomies or medial opening wedge osteotomies for angular deformity with an average follow up of 33 months.8 There were six males and six females with a mean age of 46. Preoperative diagnoses included degenerative arthritis, post-traumatic malunion and congenital deformities. Surgeons performed seven medial closing and five medial opening wedge osteotomies. Outcome measures included American Orthopedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scores, Takakura ankle arthritis scores and pain levels.9
Average AOFAS scores improved from 53.8 to 87 points and the Takakura score improved from 14.6 to 32.3 points.8 Pain levels also improved for this small subset of patients over their follow-up period. Researchers saw no significant difference in leg length discrepancy or the time to osseous healing between a medial closing and opening wedge osteotomy. There were two nonunions and one delayed union in this study.