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Introduction: Radiographic stress shielding is a common finding in uncemented convertible short-stem shoulder arthroplasty (UCSSSA). The distal filling ratio (DFR) has been described as a predictor for the occurrence of stress shielding. A DFR > 70% was mentioned as a risk factor for the occurrence of stress shielding for some UCSSSA. However, measurements were only performed on conventional radiographs and no validation exists for 3D automated planning tools. Methods: DFR was manually measured on postoperative true ap radiographs of 76 shoulder arthroplasties using a standardized protocol and were compared to preoperative CT scans with an automated calculation of the DFR after virtual implantation of the stem. Results: The mean DFR measured on X-rays was 75.9% (SD = 8.7; 95% CI = 74–78) vs. 78.9% (SD = 9.1; 95% CI = 76.8–83) automatically measured on CT scans. This difference was significant (p < 0.001). In 7 out of 76 cases (9%) the difference between manual measurement on radiographs and computerized measurement on CT scans was > 10%. Conclusion: Manual measurement of the DFR is underestimated on conventional radiographs compared to automated calculation on CT scans be a mean of 3%. Therefore, automated measurement of the DFR on CT scans seems to be beneficial, especially in cases with osteopenic cortices. Manual measurement of the DFR on conventional ap radiographs in cases without CT scans, however, is still a viable alternative. Level of evidence: Level IV, retrospective study. [ABSTRACT FROM AUTHOR]

Purpose: Clinical evaluation of the shoulder range of motion (RoM) may vary significantly depending on the surgeon. We aim to validate an automatic shoulder RoM measurement system associating image acquisition by an RGB-D (red/green/blue–depth) video camera to an artificial intelligence (AI) algorithm. Methods: Thirty healthy volunteers were included. A 3D RGB-D sensor that simultaneously generated a colour image and a depth map was used. Then, an open-access convolutional neural network algorithm that was programmed for shoulder recognition provided a 3D motion measure. Each volunteer adopted a randomized position successively. For each position, two observers made a visual (EyeREF) and goniometric measurement (GonioREF), blind to the automated software which was implemented by an orthopaedic surgeon. We evaluated the inter-tester intra-class correlation (ICC) between observers and the concordance correlation coefficient (CCC) between the three methods. Results: For manual evaluations EyeREF and GonioREF, ICC remained constantly excellent for the widest motions in the vertical plane (i.e., abduction and flexion). It was very good for ER1 and IR2 and fairly good for adduction, extension, and ER2. Differences between the measurements' means of EyeREF and shoulder RoM was significant for all motions. Compared to GonioREF, shoulder RoM provided similar results for abduction, adduction, and flexion and EyeREF provided similar results for adduction, ER1, and ER2. The three methods showed an overall good to excellent CCC. The mean bias between the three methods remained under 10° and clinically acceptable. Conclusion: RGB-D/AI combination is reliable in measuring shoulder RoM in consultation, compared to classic goniometry and visual observation. [ABSTRACT FROM AUTHOR]

Background: Component selection and placement in reverse total shoulder arthroplasty (RTSA) is still being debated. Recently, scapulothoracic orientation and posture have emerged as relevant factors when planning an RTSA. However, the degree to which those parameters may influence ROM and whether modifiable elements of implant configuration may be helpful in improving ROM among patients with different postures have not been thoroughly studied, and modeling them may be instructive.Questions/purposes: Using a dedicated expansion of a conventional preoperative planning software, we asked: (1) How is patient posture likely to influence simulated ROM after virtual RTSA implantation? (2) Do changes in implant configuration, such as humeral component inclination and retrotorsion, or glenoid component size and centricity improve the simulated ROM after virtual RTSA implantation in patients with different posture types?Methods: In a computer laboratory study, available whole-torso CT scans of 30 patients (20 males and 10 females with a mean age of 65 ± 17 years) were analyzed to determine the posture type (Type A, upright posture, retracted scapulae; Type B, intermediate; Type C, kyphotic posture with protracted scapulae) based on the measured scapula internal rotation as previously described. The measurement of scapular internal rotation, which defines these posture types, was found to have a high intraclass correlation coefficient (0.87) in a previous study, suggesting reliability of the employed classification. Three shoulder surgeons each independently virtually implanted a short, curved, metaphyseal impaction stem RTSA in each patient using three-dimensional (3D) preoperative surgical planning software. Modifications based on the original component positioning were automatically generated, including different humeral component retrotorsion (0°, 20°, and 40° of anatomic and scapular internal rotation) and neck-shaft angle (135°, 145°, and 155°) as well as glenoid component configuration (36-mm concentric, 36-mm eccentric, and 42-mm concentric), resulting in 3720 different RTSA configurations. For each configuration, the maximum potential ROM in different planes was determined by the software, and the effect of different posture types was analyzed by comparing subgroups.Results: Irrespective of the RTSA implant configuration, the posture types had a strong effect on the calculated ROM in all planes of motion, except for flexion. In particular, simulated ROM in patients with Type C compared with Type A posture demonstrated inferior adduction (median 5° [interquartile range -7° to 20°] versus 15° [IQR 7° to 22°]; p < 0.01), abduction (63° [IQR 48° to 78°] versus 72° [IQR 63° to 82°]; p < 0.01), extension (4° [IQR -8° to 12°] versus 19° [IQR 8° to 27°]; p < 0.01), and external rotation (7° [IQR -5° to 22°] versus 28° [IQR 13° to 39°]; p < 0.01). Lower retrotorsion and a higher neck-shaft angle of the humeral component as well as a small concentric glenosphere resulted in worse overall ROM in patients with Type C posture, with severe restriction of motion in adduction, extension, and external rotation to below 0°.Conclusion: Different posture types affect the ROM after simulated RTSA implantation, regardless of implant configuration. An individualized choice of component configuration based on scapulothoracic orientation seems to attenuate the negative effects of posture Type B and C. Future studies on ROM after RTSA should consider patient posture and scapulothoracic orientation.Clinical Relevance: In patients with Type C posture, higher retrotorsion, a lower neck-shaft angle, and a larger or inferior eccentric glenosphere seem to be advantageous. [ABSTRACT FROM AUTHOR]

Background: The aim of our study was to evaluate the accuracy of manual determination of the three key points defining the anatomical plane of the scapula, which conditions the reliability of planning software programs based on manual method. Method: We included 82 scapula computed tomography scans (56 pathologic and 26 normal glenoid), excluding truncation and major three-dimensional artifact. Four observers independently picked the three key points for each case. Inter- and intra-observer agreement was calculated for each point, using the intraclass correlation method. The mean error (mm) between the observers was calculated as the diameter of the smallest sphere including the four chosen positions. Results: Lower inter-observer agreement was found for the trigonum superoinferior position and for the glenoid center anteroposterior position. The mean positioning error between the four observers was 6.9 mm for the trigonum point, and error greater than 10 mm was recorded in 25% of the cases. The mean positioning error was 3.5 mm for the glenoid center in altered glenoid, compared to 1.8 mm for normal glenoid. Discussion: Manual determination of an anatomical plane of the scapula suffers from inaccuracy especially due to the variability in trigonum picking, and in a lesser extent, to the variability of glenoid center picking in altered glenoid. [ABSTRACT FROM AUTHOR]