Exploring Methods for Improving Baseplate Fixation in Reverse Total Shoulder Arthroplasty

Improving the success of modern reverse shoulder replacements is dependent on optimal initial baseplate fixation. A cadaveric biomechanical investigation examined how peripheral screw position and orientation affect baseplate fixation in normal glenoids. The results show no statistically significant difference between screw position (p=.60) or orientation (p=.20) regarding baseplate micromotion in the non-eroded glenoid. In a subsequent study to determine best management in pathologic baseplate fixation, a computer-model was employed to quantify the erosion in the E2 type glenoid. In the E2 type glenoid, erosion was found to be oriented postero-superiorly and covering an average of 66% of the surface area of the glenoid, requiring a full augmented baseplate for best seating. Overall, these findings support aiming peripheral screws into best quality bone. In the eroded E2 type glenoid, this is located postero-superiorly encompassing two-thirds of the glenoid’s surface and can be managed by dialing a full wedge augmented baseplate postero-superiorly

Mixed reality visualization in shoulder arthroplasty: is it better than traditional preoperative planning software?

Background Preoperative traditional software planning (TSP) is a method used to assist surgeons with implant selection and glenoid guide-pin insertion in shoulder arthroplasty. Mixed reality (MR) is a new technology that uses digital holograms of the preoperative plan and guide-pin trajectory projected into the operative field. The purpose of this study was to compare TSP to MR in a simulated surgical environment involving insertion of guide-pins into models of severely deformed glenoids. Methods Eight surgeons inserted guide-pins into eight randomized three-dimensional-printed severely eroded glenoid models in a simulated surgical environment using either TSP or MR. In total, 128 glenoid models were used and statistically compared. The outcomes compared between techniques included procedural time, difference in guide-pin start point, difference in version and inclination, and surgeon confidence via a confidence rating scale. Results When comparing traditional preoperative software planning to MR visualization as techniques to assist surgeons in glenoid guide pin insertion, there were no statistically significant differences in terms of mean procedure time (P=0.634), glenoid start-point (TSP=2.2±0.2 mm, MR=2.1±0.1 mm; P=0.760), guide-pin orientation (P=0.586), or confidence rating score (P=0.850). Conclusions The results demonstrate that there were no significant differences between traditional preoperative software planning and MR visualization for guide-pin placement into models of eroded glenoids. A perceived benefit of MR is the real-time intraoperative visibility of the surgical plan and the patient’s anatomy; however, this did not translate into decreased procedural time or improved guide-pin position. Level of evidence Basic science study, biomechanics

Type E2 glenoid bone loss orientation and management with augmented implants

© 2019 Journal of Shoulder and Elbow Surgery Board of Trustees Background: The purpose of this study was 2-fold: (1) to quantify type E2 bone loss orientation and its association with rotator cuff fatty infiltration and (2) to examine reverse baseplate designs used to manage type E2 glenoids. Methods: Computed tomography scans of 40 patients with type E2 glenoids were examined for pathoanatomic features and erosion orientation. The rotator cuff fatty infiltration grade was compared with the erosion orientation angle. To compare reconstructive options in light of the pathoanatomic findings, virtual implantation of 4 glenoid baseplate designs (standard, half wedge, full wedge, and patient-matched) was conducted to determine the volume of bone removal for seating and impingement-free range of motion. Results: The mean type E2 erosion orientation angle was 47° ± 17° from the 0° superoinferior glenoid axis, resulting in the average erosion being located in the posterosuperior quadrant directed toward the 10:30 clock-face position. The type E2 neoglenoid, on average, involved 67% of the total glenoid surface (total surface area, 946 ± 209 mm2; neoglenoid surface area, 636 ± 247 mm2). The patient-matched baseplate design resulted in significantly (P ≤.01) less bone removal (200 ± 297 mm3) for implantation, followed by the full-wedge design (1228 ± 753 mm3), half-wedge design (1763 ± 969 mm3), and standard (non-augmented) design (4009 ± 1210 mm3). We noted a marked difference in erosion orientation toward a more superior direction as the subscapularis fatty infiltration grade increased from grade 3 to grade 4 (P \u3c.001). Conclusion: The average type E2 erosion orientation was directed toward the 10:30 clock-face position in the posterosuperior glenoid quadrant. This orientation resulted in the patient-matched glenoid augmentation requiring the least amount of bone removal for seating, followed by the full-wedge, half-wedge, and standard designs. Implant selection also substantially affected computationally derived range of motion in external rotation, flexion, extension, and adduction

Density distribution of the type E2 glenoid in cuff tear arthropathy

© 2019 Journal of Shoulder and Elbow Surgery Board of Trustees Background: Little is known about the cortical-like and cancellous bone density variations in superiorly eroded glenoids due to cuff tear arthropathy. The purpose of this study was to analyze regional bone density in type E2 glenoids. Methods: Clinical shoulder computed tomography scans were obtained from 32 patients with a type E2 superior erosion (10 men and 22 women; mean age, 73 years). Measurement regions were organized into quadrants (superior, inferior, anterior, and posterior) and depth regions. The depth regions were incremented by 2 mm from 0 to 10 mm. A repeated-measures multiple analysis of variance was performed to assess differences and interactions between mean densities (cortical-like and cancellous bone) in each depth, in each quadrant, and between sexes. Results: The lowest cancellous bone density was found in the inferior glenoid quadrant compared with all other quadrants (307 ± 50 Hounsfield units [HU], P \u3c .001). At the glenoid surface, the superior quadrant contained the highest mean density for cortical-like bone (895 ± 97 HU); this differed significantly from the posterior, anterior, and inferior quadrants (P ≤ .033). As for depth of measurement, cortical-like bone was most dense at the glenoid surface (0-2 mm, 892 ± 91 HU), and density decreased significantly at depths greater than 2 mm (P ≤ .019). Conclusion: In patients with type E2 glenoids due to cuff tear arthropathy, the densest bone was found in the superior quadrant in the area of erosion. The inferior quadrant, which tends to be unloaded as the humeral head migrates superiorly, had the lowest density bone. In addition, the best-quality bone was located at the glenoid surface as compared with deeper in the vault