Factors Influencing Appropriate Implant Selection and Position in Reverse Total Shoulder Arthroplasty

A reduced scapulo-humeral angle contributes to the development of scapular notching in reverse total shoulder arthroplasty

PURPOSE

Scapular Notching (SN) is one of the most common postoperative complications for a patient after Reverse Total Shoulder Arthroplasty (RTSA). Despite employing various strategies to mitigate SN risk, the overall incidence remains far from zero. This article introduces a new risk factor, the scapulo-humeral angle (SHA), as a key element influencing the risk for SN.

METHODS

A retrospective analysis was conducted on all patients who underwent RTSA for rotator cuff arthropathy at the study centre. The preoperative SHA was measured, and the presence of SN was investigated and graded using the Nerot classification at the latest follow-up.

RESULTS

42 patients were included. 12 presented SN (incidence 28.5%). A statistically significant Pearson coefficient correlation between pre-operative SHA and the incidence of SN was observed (r= -0.6954; 95% C.I. -0,8250 to -0,4963; p < 0.0001). A statistically significant Pearson coefficient correlation was also found between the degree of SN and the pre-operative SHA (r= -0,7045; 95% C.I. -0,8306 to -0,5096; P value (two-tailed) < 0,0001, alpha 0.05).

CONCLUSIONS

The primary finding is a statistically significant correlation between a reduced preoperative SHA and an increased incidence of postoperative SN. The secondary finding is that a smaller preoperative SHA is associated with a more severe degree of SN A SHA cut-off of 50° distinguished patients at high risk of SN from those at low risk. All patients with an SHA below 50° developed SN (10/10), whereas only 6.25% of patients with an SHA exceeding 50° experienced SN (2/32).

Virtual assessment of internal rotation in reverse shoulder arthroplasty based on statistical shape models of scapular size

Background

The purpose of this study was to assess impingement-free internal rotation (IR) in a virtual reverse shoulder arthroplasty simulation using a Statistical Shape Model based on scapula size.

Methods

A database of over 10,000 scapulae utilized for preoperative planning for shoulder arthroplasty was analyzed with a Statistical Shape Model to obtain 5 scapula sizes including the mean and 2 standard deviations. For each scapula model, one glenosphere size (33-42 mm) was selected as the best fit based on consensus among 3 shoulder surgeons. Virtual implantation variables included 1) lateral offset (0-12 mm in 2-mm increments), 2) inferior eccentricity (0, 2.5, 5, and 7.5 mm), and 3) posterior eccentricity (0, 2.5, and 5 mm). The neck shaft angle was fixed at 135° with an inlay design humeral prosthesis. IR at the side (IR0) and in abduction (IRABD) were then simulated.

Results

Maximum impingement-free IR0 was reached with increasing inferior offset in combination with increasing lateralization. Lateralization was the most important variable in increasing impingement-free IRABD. Maximum IRABD was reached at 4-6 mm of lateralization with smaller scapula (-2 to 0 standard deviation). Increasing lateralization up to 12 mm continues to increase IRABD for larger-sized scapula (+1 to +2 standard deviation). Optimal inferior offset and lateralization to maximize IR did have a small loss of external rotation in neutral abduction. There was no loss of external rotation in 60° of abduction.

Conclusion

In a virtual model, the glenosphere position required to maximize IR varied by scapula size. For smaller scapulae, maximum IR0 was reached with a combination of 2.5-mm inferior offset and 0- 4 mm of lateralization. For larger scapulae, maximum IR0 was reached with a combination of 2.5 mm of inferior offset and 4 mm of lateralization. The amount of lateralization required to maximize IRABD also varies by scapula size. Maximum IRABD was reached in smaller scapula with 4-6 mm of lateralization and at least 12 mm of lateralization in larger scapula. These findings may be applied in the clinical decision-making process knowing that impingement-free IR and IRABD can be maximized with combinations of inferior offset and lateralization based on scapula size with minimal effect on external rotation and external rotation in 60° of abduction.

Effect of using a small baseplate on the radiological and clinical outcomes of reverse total shoulder arthroplasty in Asian patients

Aims

The aim of this study was to compare the clinical and radiological outcomes of reverse shoulder arthroplasty (RSA) using small and standard baseplates in Asian patients, and to investigate the impact of a mismatch in the sizes of the glenoid and the baseplate on the outcomes.

Methods

This was retrospective analysis of 50 and 33 RSAs using a standard (33.8 mm, ST group) and a small (29.5 mm, SM group) baseplate of the Equinoxe reverse shoulder system, which were undertaken between January 2017 and March 2021. Radiological evaluations included the size of the glenoid, the β-angle, the inclination of the glenoid component, inferior overhang, scapular notching, the location of the central cage in the baseplate within the vault and the mismatch in size between the glenoid and baseplate. Clinical evaluations included the range of motion (ROM) and functional scores. In subgroup analysis, comparisons were performed between those in whom the vault of the glenoid was perforated (VP group) and those in whom it was not perforated (VNP group).

Results

Perforation of the vault of the glenoid (p = 0.018) and size mismatch in height (p < 0.001) and width (p = 0.013) were significantly more frequent in the ST group than in the SM group. There was no significant difference in the clinical scores and ROM in the two groups, two years postoperatively (all p > 0.05). In subgroup analysis, the VP group had significantly less inferior overhang (p = 0.009), more scapular notching (p = 0.018), and more size mismatch in height (p < 0.001) and width (p = 0.025) than the VNP group.

Conclusion

In Asian patients with a small glenoid, using a 29.5 mm small baseplate at the time of RSA was more effective in reducing size mismatch between the glenoid and the baseplate, decreasing the incidence of perforation of the glenoid vault, and achieving optimal positioning of the baseplate compared with the use of a 33.8 mm standard baseplate. However, longer follow-up is required to assess the impact of these findings on the clinical outcomes.

[Conversion of anatomic to reverse shoulder arthroplasty : Does it make sense?]

We can observe increasing numbers for the implantation of shoulder endoprostheses in developed industrial countries. This is accompanied by a certain number of revision surgeries. The conversion to reverse arthroplasty systems is by far the most common revision procedure. Depending on the primary implant and the individual situation, the surgical effort and consumption of resources can be substantial. Particularly favorable revision scenarios exist in the conversion of stemless primary implants that are part of a platform system and allow a partial exchange and easy conversion from anatomical to reverse implants.

Medium- to Long-Term Outcomes after Reverse Total Shoulder Arthroplasty with a Standard Long Stem

Background: Long-term clinical and radiographic outcome data after standard cemented long-stem reverse shoulder arthroplasty (RSA) remain underreported. The aim of this study is to report on medium- to long-term data of patients over 60 years of age. Methods: The same type of RSA (Aequalis Reverse II, Memphis, TN, USA) was implanted in 27 patients with a mean age of 73 years (range 61−84). Indications for RSA were cuff tear arthropathy (CTA) in 25 cases and osteoarthritis (OA) in two cases. Pre- and postoperative Constant Score was assessed and component loosening, polyethylene wear, scapular notching and revision rates were recorded at a mean clinical follow-up (FU) of 127.6 months (SD ± 33.7; range 83−185). Results: The mean-adjusted CS (aCS) improved from 30.0 (range 10−59) to 95.0 (range 33−141) points (p < 0.001). Glenoid loosening was found in two (9.1%) and stem loosening was found in three (13.6%) cases. Polyethylene wear was observed in four (18.2%) cases. Scapular notching appeared in 15 (68.2%) cases but was not associated with poor aCS (p = 0.423), high levels of pain (p = 0.798) or external rotation (p = 0.229). Revision surgery was necessary in three (11.1%) cases. Conclusions: RSA with a cemented standard long stem leads to improvement in forward elevation, abduction and pain after a mean FU of 10 years. However, external rotation does not improve with this prosthetic design. Moreover, scapular notching is observed in the majority of cases, and revision rates (11.1%) as well as humeral loosening rates (13.6%) remain a concern. Level of evidence: Level 4, retrospective cohort study.