Subacromial notching after reverse total shoulder arthroplasty

Greater distance from the glenosphere center to the acromion reduces risk of acromial impingement in semi-inlay reverse shoulder arthroplasty

Background

Recently, the issue of subacromial notching, caused by acromial impingement has been reported. The purpose of this study was to assess the impact of differences in the distance between the glenosphere center and the greater tuberosity (DGT) and the distance between the glenosphere center and the acromion (DA) on the closest distance between the greater tuberosity and the acromion during active abduction in shoulders with reverse total shoulder arthroplasty (RSA).

Methods

Eleven shoulders with semiinlay RSA were analyzed. Subjects underwent fluoroscopy during active scapular plane abduction. Computed tomography of their shoulders was performed to create three-dimensional (3D) implant models at a mean of 16 months after surgery. Using model-image registration techniques, poses of 3D implant models were iteratively adjusted to match their silhouettes with the silhouettes in the fluoroscopic images (shape matching), and 3D kinematics of implants were computed. The closest distance between the acromion and greater tuberosity was computed at maximum abduction. DA and DGT were measured from 3D surface models. Shoulders were divided into two groups based on DA and DGT measurements and their closest distance data were compared between the groups.

Results

There were 7 shoulders with DA ≥ DGT, and 4 shoulders with DA < DGT. Shoulders with DA ≥ DGT showed a significantly wider distance between the greater tuberosity and acromion at maximum abduction compared to those with DA < DGT (5.9 ± 2.4 mm vs. 0.6 ± 0.7 mm, respectively, P = .0021). There were no significant differences in maximum glenohumeral abduction angle and humeral abduction angle between the two groups. Although DA was significantly greater in shoulders with DA ≥ DGT than in those with DA < DGT (43.7 ± 4.4 mm vs. 35.1 ± 6.7 mm, respectively, P = .0275), there was no significant difference in DGT between the two groups.

Conclusion

When DGT is less than DA in shoulders with RSA, the closest distance between the greater tuberosity and the acromion at maximum abduction is significantly wider compared to cases where DGT is greater than DA by 3D measurement. Therefore, acromial impingement is less likely to occur in shoulders with RSA when DA is greater than DGT. To avoid acromial impingement, it might be important to make DA greater than DGT.

Rates of subacromial notching are low following reverse shoulder arthroplasty with a 135° inlay humeral component and a lateralized glenoid

Background

Lateralization in reverse shoulder arthroplasty (RSA) decreases bony impingement and improves rotational range of motion, but has been theorized to increase the risk of subacromial notching (SaN). The purpose of this study was to evaluate the presence of SaN following RSA and its relationship with lateralization with a 135° inlay humeral component. The secondary purpose was to assess the association of SaN with functional outcomes.

Methods

A retrospective review was performed from a multicenter prospectively collected database on patients who underwent primary RSA from 2015 to 2021. All RSAs were performed with a 135° inlay humeral component. SaN was defined as bony erosion with sclerotic margins on the undersurface of the acromion on final follow-up radiographs not present preoperatively. Postoperative implant positioning (inclination, distalization, and lateralization) were evaluated on minimum 1-year postoperative radiographs. Regression analyses were performed on implant and clinical variables to assess for risk factors. A separate analysis was performed to determine the association of SaN with clinical outcomes.

Results

SaN was identified in 13 out of 442 shoulders (2.9%). Age, sex, body mass index, smoking status, diabetes mellitus, arm dominance had no relationship with SaN. Neither glenoid sided lateralization nor humeral offset were associated with SaN risk. Other implant characteristics such as distalization, glenosphere size, and postoperative inclination did not influence SaN risk. The presence of SaN did not affect patient-reported outcomes (American Shoulder and Elbow Surgeons: P = .357, Visual Analog Scale: P = .210) or range of motion.

Conclusion

The rate of SaN is low and not associated with glenoid or humeral prosthetic lateralization when using a 135° inlay humeral component. When SaN occurs, it is not associated with functional outcomes or range of motion at short-term follow-up.

Rotator cuff tears

Rotator cuff tears are the most common upper extremity condition seen by primary care and orthopaedic surgeons, with a spectrum ranging from tendinopathy to full-thickness tears with arthritic change. Some tears are traumatic, but most rotator cuff problems are degenerative. Not all tears are symptomatic and not all progress, and many patients in whom tears become more extensive do not experience symptom worsening. Hence, a standard algorithm for managing patients is challenging. The pathophysiology of rotator cuff tears is complex and encompasses an interplay between the tendon, bone and muscle. Rotator cuff tears begin as degenerative changes within the tendon, with matrix disorganization and inflammatory changes. Subsequently, tears progress to partial-thickness and then full-thickness tears. Muscle quality, as evidenced by the overall size of the muscle and intramuscular fatty infiltration, also influences symptoms, tear progression and the outcomes of surgery. Treatment depends primarily on symptoms, with non-operative management sufficient for most patients with rotator cuff problems. Modern arthroscopic repair techniques have improved recovery, but outcomes are still limited by a lack of understanding of how to improve tendon to bone healing in many patients.

Baseplate inferior offset affects shoulder range of motion in reverse shoulder arthroplasty in Asian population

BACKGROUND

Impingement is a common complication of reverse shoulder arthroplasty. Placement of the baseplate with a wide impingement-free angle is ideal; however, there are few studies on Asian populations, which have smaller height and physique, and there is a lack of guidance on achieving optimal outcomes. The purpose of the present study was to explore the impingement-free range of motion reverse shoulder arthroplasty and analyze the suitable baseplate position or tilt for the Asian population using simulation software.

METHODS

We uploaded computed tomography scan data from 20 Asian patients to three-dimensional (3D) simulation software. The implantation of the reverse shoulder arthroplasty component was performed on the 3D humerus and scapula using software, and range of motion was assessed until impingement occurred.

RESULTS

The range of motion in flexion significantly improved when the baseplate was lowered up to 3 mm inferiorly. Range of motion in abduction and internal and external rotation significantly improved as the baseplate was lowered up to 4 mm. There was no significant difference in range of motion in any motion after changing the inferior tilt, except in internal and external rotation.

CONCLUSIONS

The range of motion in abduction, flexion, and internal and external rotations significantly improved with increased inferior offset. These results may prove valuable in determining the optimal baseplate position for RSA, particularly in Asian populations.