Opposite cortical fracture in high tibial osteotomy: lateral closing compared to the medial opening-wedge technique.

BACKGROUND AND PURPOSE

The aim with high tibial valgus osteotomy (HTO) is to correct the mechanical axis in medial compartmental osteoarthritis of the knee. Loss of operative correction may threaten the long-term outcome. In both a lateral closing-wedge procedure and a medial opening-wedge procedure, the opposite cortex of the tibia is usually not osteotomized, leaving 1 cm of bone intact as fulcrum. A fracture of this cortex may, however, lead to loss of correction; this was examined in the present study.

PATIENTS AND METHODS

We used a prospective cohort of 92 consecutive patients previously reported by Brouwer et al. (2006). The goal in that randomized controlled trial, was to achieve a correction of 4 degrees in excess of physiological valgus. In retrospect, we evaluated the 1-year radiographic effect of opposite cortical fracture. Opposite cortical fracture was identified on the postero-anterior radiographs in supine position on the first day after surgery.

RESULTS

44 patients with a closing-wedge HTO (staples and cast fixation) and 43 patients with an opening-wedge HTO (non-angular-stable plate fixation) were used for analysis. 36 patients (four-fifths) in the closing-wedge group and 15 patients (one-third) in the opening-wedge group had an opposite cortical fracture (p < 0.001). At 1 year, the closing-wedge group with opposite cortical fracture had a valgus position with a mean HKA angle of 3.2 (SD 3.5) degrees of valgus. However, the opening-wedge group with disruption of the opposite cortex achieved varus malalignment with a mean HKA angle of 0.9 (SD 6.6) degrees of varus.

INTERPRETATION

Fracture of the opposite cortex is more common for the lateral closing wedge technique. Medial cortex disruption has no major consequences, however, and does not generally lead to malalignment. Lateral cortex fracture in the medial opening-wedge technique, with the use of a non-angular stable plate, leads more often to varus malalignment.