The bare area of the proximal ulna. An anatomical study on optimizing olecranon osteotomy

Olecranon osteotomy is an established approach for the treatment of distal humerus fractures. It should be performed through the bare area of the proximal ulna to avoid iatrogenic cartilage lesions. The goal of this study was to analyze the anatomy of the proximal ulna with regard to the bare area and, thereby, to optimize the hitting area of the bare area when performing olecranon osteotomy. The bare areas of 30 embalmed forearm specimens were marked with a radiopaque wire and visualized three-dimensionally with a mobile CaEuroarm. By means of 3D reconstructions of the data sets, the following measurements were obtained: height of the bare area; span of the bare area-hitting area in transverse osteotomy; ideal angle for olecranon osteotomy to maximize the hitting area of the bare area; distance of the posterior olecranon tip to the entry point of the transverse osteotomy and the ideal osteotomy. The height of the bare area was 4.92 +/- 0.81 mm. The hitting area of the transverse osteotomy averaged 3.73 +/- 0.89 mm. The ideal angle for olecranon osteotomy was 30.7A degrees +/- 4.19A degrees. The distance of the posterior olecranon tip to the entry point was 14.08 +/- 2.75 mm for the transverse osteotomy and 24.21 +/- 3.15 mm for the ideal osteotomy. The hitting area of the bare area in the ideal osteotomy was enhanced significantly when compared to the transverse osteotomy (p < 0.0001). This study provides guide values for correct osteotomy of the olecranon. Moreover, a 30A degrees angulation of the osteotomy can significantly increase the hitting area of the bare area.