2.2. In Vitro Study
CORTEX
For performance assessment, the Xin1 system was compared to the conventional free-hand method in 12 intact, non-fractured shoulders from 6 formalin-embalmed, full-body specimens (3 male and 3 female), which were pre-used for medical student courses. The experiment was performed at the Department of Anatomy of the Medical University of Innsbruck, Austria. Left and right shoulders were randomized into Xin1 and conventional groups. All operations were performed by a single operator (DK), who was at the time the resident surgeon with moderate surgical experience. For both groups, a deltopectoral approach was created and a PHILOS plate was prepositioned and fixed with a cortex screw in the elongated combi-hole (F-level, For the conventional procedure, the plate position and screw lengths were estimated via repeated fluoroscopy and by use of a length probe (Ref. 03.122.052, DePuy Synthes Inc., Raynham, MA, USA) with a target TJD of 5 mm. Eight screws (Ref. X12.1xx, 3.5 Locking Screw, TAN, DePuy Synthes Inc., Raynham, MA, USA) were placed using the screw insertion guide (Ref. 03.122.053, DePuy Synthes Inc., Raynham, MA, USA). Only screw hole 7 on the D-level was left empty. Plate and screw placement was verified via fluoroscopic imaging.For the Xin1 procedure, a marker clip was additionally attached to the drill sleeve (For the TJD accuracy measurement, the humeral head was dislocated from the joint, and the screw tip-to-joint distances were measured including the cartilage layer for all screws by inserting a K-wire into the over-drilled hole until touching the screw tip. The insertion depth was then marked with forceps and measured with a caliper (Non-parametric independent sample tests (Mann–Whitney U) were performed to compare both techniques regarding accuracy (TJD and TJD error), procedure time, number of fluoroscopic images and radiation time. All analyses were performed using SPSS software version 27 (IBM Corporation, Armonk, NY, USA). For all tests level of significance was set to α = 0.05.