Hexagonal grafts in mosaicplasty: Biomechanical comparison of standard cylindrical and novel hexagonal grafts in calf cadaver model

Abstract

Objective: Cylindrical grafts are currently used to cover defected area in mosaicplasty. However, there aresome difŞculties with cylindrical grafts, such as potential dead space between grafts and insufŞcientcoverage. Hexagonal graft (honeycomb model) was created and evaluated in this biomechanical study.Hypothesis was that harvesting grafts with hexagonal shape, which has the best volume geometrycharacteristics in nature, would be biomechanically advantageous and provide superior pull-outstrength.Methods: Total of 24 fresh calf femurs were divided into 3 equal groups. In theŞrst group, 1 cylindricaland 1 hexagonal graft were compared. Second group consisted of 3 cylindrical and 3 hexagonal grafts.Third group was designed to evaluate effect of graft depth; hexagonal graft implanted at 5 mm depth wascompared with 20-mm-deep hexagonal graft. All specimens were subjected to pull-out test. FrictionŞeldand graft surface area were also evaluated.Results: Pull-out strength comparison of 15-mm-deep triple cylindrical grafts and 15-mm-deep triplehexagonal grafts in second group revealed statistically signiŞcant difference in favor of hexagonal grafts(p< 0.05). Surface area of cylindrical graft with 9-mm diameter was calculated to be 50.27 mm2, whilehexagonal graft surface area was 55.425 mm2. Volume ratio of cylindrical and hexagonal grafts was753.98 mm3and 831.375 mm3, respectively.Conclusion: This biomechanical study demonstrated that graft geometry, especially in multiple graftapplications, is a factor that influences stability. Hexagonal grafts appear to be more stable than cylindrical grafts in multiple applications, and they may be used to cover a larger defected area.© 2017 Turkish Association of Orthopaedics and Traumatology. Publishing services by Elsevier B.V. This isan open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).