Evaluation of Contact Area and Pressure After Malreduction in Isolated Medial Malleolar Fractures With 2 mm of Displacement: A Cadaveric Study

Abstract

This study was performed to evaluate the changes in contact area and pressure in the tibiotalar joint, with a 2 mm displacement after IMMF (isolated medial malleolar fracture). Ten cadavers with pairs were used to establish a situation in which IMMF occurred during ankle injury. We performed IMMF corresponding to types C and D of the Herscovici classification, and it was displaced by 2 mm. The normal group was defined as a normal tibiotalar joint, the TF (transverse fracture) group as a 2 mm transverse displacement corresponding to the Herscovici classification type C, and the OF (oblique fracture) group as a 2 mm oblique displacement corresponding to the Herscovici classification type D. We measured the contact area and pressure at the tibiotalar joint. The film was scanned and analyzed using the digital imaging software, Scion Image (Scion Crop. Frederick, MD). In normal group, the average contact area of the tibiotalar joint was 317 mm² (IQR; interquartile range, 256; 347) and 308 mm² (IQR, 262; 364), average pressure was 2.19 N/mm² (IQR, 1.94; 2.27) and 2.15 N/mm² (IQR, 2.06; 2.53). In the TF and OF groups, the average contact area of the tibiotalar joint decreased by 9% and 12%, respectively, and the average pressure increased by 8% and 14%, respectively. There was no statistical difference in peak pressure between the normal, TF, and OF groups. In the case of transverse and oblique fractures, a 2 mm displacement showed significant changes in contact area and contact pressure compared to the normal tibiotalar joint, but there were no significant changes pertaining to type, between the 2 fractures.

Keywords: ankle fracture; biomechanics; cadaver.