Contact Pressures Change According to Displacement Shape in Isolated Medial Malleolar Fracture: Cadaver Study

CATEGORY: Trauma; Basic Sciences/Biologics INTRODUCTION/PURPOSE: Ankle fractures, representing 9% of all fractures, are among the most common types of fractures worldwide. 1 of 5 ankle fractures is an isolated medial malleolar fracture (IMMF). IMMF were treated surgically, but recently it was concluded that all IMMF(<=2mm) should be treated conservatively. The indication for surgery or conservative treatment of IMMF remains unclear. The purpose of the present study is to check the change of pressure in the ankle joint according to the shape and the displacement in the medial malleolus fractures. METHODS: Twenty pairs of fresh-frozen cadaveric lower legs, disarticulated at the knee, will be used. Specimen pairs were assigned at random into 1 of 2 groups. This study measures the pressure change in the ankle joint according to Muller type C and D. The specimen was mounted in the materials testing machine with the plantar aspect of the foot in contact with the foot-plate. Load was applied with the ankle in the neutral position. Contact area and contact pressure were quantitated with low-grade pressure-sensitive film (Prescale film; Fuji Photo Film, Tokyo, Japan). The color densities were converted to measurements of pressure. After osteotomy the medial malleolus in Muller type C and D, displace each 2mm and fix it with diameter 4.0mm and length 45 mm cortical bone screws. Pressure measurement is done in the same way as above. RESULTS: The median value and wilconxon singed rank test was used for the results. The median value of normal ankle contact area was 3.15cm(2) [2.61.;3.51], the mean pressure was 2.18 Mpa(Megapascal) [2.00.;2.43], and the median value of contact area after transverse osteotomy was 2.89cm(2) [2.41.;3.24], mean pressure was 2.37Mpa [2.14.;2.75], and the median value of contact area after oblique osteotomy was 2.72cm(2) [2.50.;3.16], mean pressure was 2.50Mpa [2.33.;2.74]. P value of the mean area and mean pressure change after transverse and oblique was <0.05. CONCLUSION: At 2mm transverse and oblique displacement, ankle contact area and pressure decreased significantly.