Scapular notching is a complication after reverse shoulder arthroplasty with a high incidence up to 100%. Its clinical relevance remains uncertain; however, some studies have reported that scapular notching is associated with an inferior clinical outcome. There have been no published articles that studied positional relationship between the scapular neck and polyethylene insert in vivo. The purpose of this study was to measure the distance between the scapular neck and polyethylene insert in shoulders with Grammont type reverse shoulder arthroplasty during active external rotation at the side. Eighteen shoulders with Grammont type prosthesis (Aequalis Reverse, Tornier) were enrolled in this study. There were 13 males and 5 female, and the mean age at surgery was 74 years (range, 63–91). All shoulders used a glenosphere with 36mm diameter, and retroversion of the humeral implant was 10°in 4 shoulders, 15°in 3 shoulders, and 20°in 11 shoulders. Fluoroscopic images were recorded during active external rotation at the side from maximum internal to external rotation at the mean of 14 months (range, 7–24) after surgery. The patients also underwent CT scans, and three-dimensional glenosphere models with screws and scapula neck models were created from CT images. CT-derived models of the glenosphere and computer-aided design humeral implant models were matched with the silhouette of the implants in the fluoroscopic images using model-image registration techniques (Figure 1). Based on the calculated kinematics of the implants, the closest distance between the scapular neck and polyethylene insert was computed using the scapular model and computer-aided design insert models (Figure 2). The distance was computed at each 5° increment of glenohumeral internal/external rotation, and the data from 20°internal rotation to 40°external rotation were used for analyses. One-way repeated-measures analysis of variance was used to examine the change of the distance during the activity, and the level of significance was set at P < 0.05.Background
Methods
Massive rotator cuff tears and consequent cuff-deficient arthritis (CTA) of the shoulder can cause severe shoulder dysfunction in the elderly. Reverse total shoulder arthroplasty (RTSA) has been widely used for treatment of CTA in all over the world since its introduction in the 90's. In Japan, however, we have just started to clinically use RTSA from April 2014. In addition, we have only one choice of the implants (Aequalis Reverse, Tornier) currently, and only one size of the base-plate of the glenoid component (29 mm in diameter) is available so far. Japanese, especially elderly people, have generally smaller figure than Caucasians. We are not sure whether the base-plate would fit for the smaller Japanese. The purpose of this study was to measure the size of the glenoids in Japanese using CT images and to examine that they would fit the 29 mm base-plate. The shoulders without osteoarthritis of the glenohumeral joint were eligible for the study. The subjects consisted of 30 shoulders including 10 elderly males, 10 elderly females, and 10 younger males, and the mean ages were 73 (range, 63–81), 74 (range, 65–89), and 32 (range, 27–36) years old, respectively. Mean heights and weights were 164 cm (range, 156–179) and 59 kg (range, 49–72), 154 cm (range, 151–161) and 57 kg (range, 48–65), and 173 cm (range, 162–179) and 72 kg (range, 61–100), respectively. CT images with a 0.3 mm slice pitch were used for the analysis. The images were loaded into a DICOM viewer (OsiriX), and a slice for simulated implantation of the base-plate was created using the multi-planar reconstruction (Figure 1), which had 10° of inferior tilt to the glenoid face. The width of the glenoid in the antero-posterior direction was measured at 14 mm above the inferior edge of the glenoid.Background
Methods
