Safe Zone for Medial Open-Wedge Supramalleolar Osteotomy of the Ankle: A Cadaveric Study.

Background: The purpose of this present study was to determine the incidence of lateral cortical fracture depending on the plane of osteotomy in medial open-wedge supramalleolar osteotomy (SMO) and to define a safe zone through which a medial open-wedge SMO could be performed with minimal risk of lateral cortical fracture.

Materials And Methods: Matched pairs of fresh-frozen human cadaver lower leg specimens were obtained from 7 males and 3 females (average age = 63.9 [range 49-75] years). In group A, a safe zone-level medial open-wedge SMO (plane of osteotomy oriented to the proximal one-third of the intrasyndesmosis) was performed, and in group B, a higher-level medial open-wedge SMO (plane of osteotomy oriented to the suprasyndesmosis) was performed.

Results: In group A, 7 of the 10 limbs had no lateral cortical fracture, and 3 had lateral cortical fracture, but all of the fractured limbs were stable during the medial open-wedge SMO procedure. In group B, 2 of 10 limbs had no lateral cortical fracture and 8 had lateral cortical fracture. Three of the 8 fractured limbs were stable, but 5 were unstable during the medial open-wedge SMO procedure. The incidence of lateral cortical fracture in group B was significantly higher compared to group A (P = .04).

Conclusions: According to the present findings, lateral cortical fracture was less likely to occur when open-wedge SMO was at the plane of the proximal one-third of the intrasyndesmosis, the so-called "safe zone," than at the plane of the suprasyndesmosis.

Clinical Relevance: A safe zone for medial open-wedge SMO to prevent lateral cortical fracture during the medial open-wedge SMO procedure was identified.