3.2. Clinical Handling Test
proximal humerus fractures, Fracture
ADVERSE EVENTS
Eleven proximal humerus fractures (eight left, three right shoulders) from eight female and three male patients were operated by five different surgeons. The average age of patients at surgery was 67 years and ranged between 47 and 84 years. Fracture types (AO classification) were: 1× 11A2, 1× 11A3, 3× 11B1, 1× 11B2, 4× 11C1 and 1× 11C3. With one exception, where a Philips Zenition 70 system (Koninklijke Philips N.V., Amsterdam, The Netherlands) was used, all intraoperative images were acquired with a Siemens Arcadis Varic (Siemens Healthcare GmbH, Erlangen, Germany) C-arm. Handling of the marker clip in the hospital environment and during surgery was feasible in all patients and did not interfere with hospital processes or surgical procedures. No adverse events concerning the use of the marker clip were recorded for the 11 performed operations. For the retrospective image analysis, five out of eleven patients needed to be excluded for various reasons: for example, one patient was excluded due to the intraoperative use of a wrong drill sleeve, leading to the mispositioning of the marker clip. For two patients, no images after screw insertion were stored to the C-arm. For another two patients, the image pair view angle was too narrow for calculation.Xray images of the remaining six patients underwent retrospective evaluation. Robust marker detection, humeral head segmentation and screw length determination were achieved in all image pairs. The view angle between the images of a pair was on average 27° (range 19°–34°). The calculated screw lengths before and after screw placement differed on average by 1.2 ± 1.7 mm. In five out of six patients, this difference was ≤2 mm for all screws. In one patient (#10), differences up to 8 mm were found. A total of thirty-seven screws were placed in the six evaluated patients. Used screw lengths ranged from 32 to 50 mm. The Xin1 calculation before screw placement correlated significantly with the actual screw lengths implanted (R = 0.78, Maximum plate offset before screw placement was 5 mm in a dorsal–ventral direction and 9 mm in a cranial–caudal direction in respect to the center of the humeral head. After placing the screws, the relative plate position shifted at a maximum of 4 mm for five out of six patients. In one patient (#10), the plate was displaced by 10 mm in the dorsal–ventral direction after screw placement according to the Xin1 measurement (