Cancellous autografts of the calcaneus: an area-bound measurement of density values in Hounsfield units by use of computed tomography for enhanced bone graft harvest

Abstract

Background: In foot and ankle surgery, the calcaneus serves as an established harvest site for autogenous grafts. As described in current literature, the procedure is associated with a low complication rate of 0 to 13.8%. But, only small amounts of bony material are harvestable by a lateral approach that has not been standardized until now. Moreover, the current technique neither considers the material quantity nor the material quality within the calcaneus. Our study was designed to determine the calcaneal area providing the highest density values in Hounsfield units (HU) in order to harvest more material while causing less damage to the bone. Methods:In 402 eligible sagittal foot and ankle CT scans, the calcaneus was divided into areas I, II, III and IV on the basis of anatomical landmarks. HU values were obtained per area and per measuring slice. Additional peculiarities, such as the location of the neutral triangle, were also recorded. Results:The average density value was 284 HU for area I, 185 HU for area II, 183 HU for area III and 173 HU for area IV. Age-dependent as well as ageindependent density values were significantly higher in area I than in areas II to IV (all p < 0.0001). When comparing HU values of all males (215; 53.5 %) to HU values of all females (187; 46.5 %), no significant difference was found for areas I and II (both p = 0.9995). Conclusion:Our study revealed that area I is the best harvest site for the retrieval of cancellous autografts of the calcaneus, regarding the available material. Thus, the current lateral approach needs to be modified: a lateral-superior approach or a dorsal approach might be conceivable. Further research on consequential complications and biomechanical impacts is required.