Neck shaft angle (NSA) in Reverse Shoulder Arthroplasty (RSA): 135 versus 145 degrees at minimum 2 years follow-up

BACKGROUND

The most common complication with Reverse Shoulder Arthroplasty (RSA) Grammont based design with a 155° neck shaft angle (NSA) is scapular notching. Scapular notching has been associated with both reduced clinical outcomes. Reducing the humeral neck shaft angle from 155 degrees has been shown to reduce the incidence of scapular notching however it is unknown whether there is a difference in scapular notching between a 145 and 135° NSA. The purpose of this study was to evaluate the effect of decreasing the NSA on scapular notching rate and postoperative range of motion comparing 145° and 135° NSA stems at minimum two year of follow-up.

METHODS

Consecutive patients undergoing primary RSA with a neck shaft angle of either 145° or 135° between January 2014 and February 2019 were retrospectively reviewed. Patients were included if they were over the age of 18, had minimum clinical follow-up of 24 months with true postoperative anteroposterior radiographic view.

RESULTS

One hundred and three patients were included for the final analysis: 73 with a 145° NSA and 30 with a 135° NSA stem. The mean age and mean follow-up were respectively 70.9 years (range, 52.0-89.0) and 32.1 months. The overall incidence of scapular notching was 46.6 %. There was a statistically significant difference in scapular notching between the 145° (53.4%) and 135° (30%) NSA groups (p=.028). There was no difference in terms of postoperative Constant-Murley Score (mean, 66.1 Vs 68.2; p =.395) , Subjective Shoulder Value (mean, 76,5 Vs 83.1%, p= .167), forward flexion (mean, 140° Vs 142°, p= .704), abduction (mean, 123.2° Vs 121.5° , p= .771), external rotation with the arm at the side (mean, 34.1° vs 37.3°, p= .341) and internal rotation (mean, 5.3 vs 5.4 pts p=.336) between the two groups.

CONCLUSION

This is the first study to compare the effect of a 145° vs 135° neck shaft angle on scapular notching rates. The key finding of this study is that scapular notching rate was significantly reduced from 53% to 30% in 135° NSA compared to 145° NSA, after at least 24 months of follow-up. Our data also shows suggests that glenoid lateralization and inferiorization has an influence on scapular notching. We are unable to state that the reduced scapular notching rate was due to a reduction in NSA alone. Despite a lower rate of scapular notching, the 135°NSA group has not shown any significant better clinical and functional outcomes.

Lateralized vs. classic Grammont-style reverse shoulder arthroplasty for cuff deficiency Hamada stage 1-3: does the design make a difference?

BACKGROUND

Reverse shoulder arthroplasty (RSA) with a lateralized design is thought to improve outcomes. Our aim was to compare RSA with the classic Grammont prosthesis against a prosthesis with 135° inclination and a lateralized glenosphere for cuff-deficient shoulders.

METHODS

Patients with irreparable massive posterosuperior rotator cuff tear Hamada grade 1-3 underwent RSA and were documented prospectively up to 24 months postsurgery. Comparative RSA groups were "lateralized" (L), with 135° humeral inclination and 36+4-mm lateralized glenosphere (n = 44), and "Grammont" (G), with 155° humeral inclination and 36+2-mm eccentric glenosphere (n = 23). Range of motion including the Apley scratch test, abduction strength, Constant-Murley score (CS), and Shoulder Pain and Disability Index (SPADI) were assessed. Anteroposterior and axial radiographs were evaluated at 24 months, and additional measurements of scapular neck and glenoid anatomy, baseplate and glenosphere position, center of rotation, humeral offset, and lateralization and distalization shoulder angles were made. Linear regression and mixed models adjusted for sex differences and preoperative values were applied.

RESULTS

Overall CS and SPADI outcomes were not significantly different between groups (P ≥ .654). For group L, external rotation remained stable up to the 2-year follow-up and was higher than for group G (P = .012 ); a greater proportion of group L patients could reach the lumbar vertebra 3 (L3) (70% vs. 48% in group G) (P = .26). Group G had a higher inferior glenosphere overhang (P = .020) and center of rotation (COR) medialization (P < .001), whereas group L had higher humeral offset (P < .001) and lateralization shoulder angle (P < .001) with a trend toward higher baseplate positioning (P = .045). The rate of scapular notching was 2.9 times higher for group G than group L (P = .001).

CONCLUSION

RSA with 135° humeral inclination and a lateralized glenosphere shows similar outcome scores as the classic Grammont design but enables better preservation of external rotation and reduces the rate of scapular notching compared with the classic Grammont design in Hamada 1-3 patients with irreparable posterosuperior tears.

A systematic review of tuberosity healing and outcomes following reverse shoulder arthroplasty for fracture according to humeral inclination of the prosthesis

BACKGROUND

Proximal humerus fractures are common in the elderly population and are often treated with reverse shoulder arthroplasty (RSA). The purpose of this systematic review was to compare tuberosity healing and functional outcomes in patients undergoing RSA with humeral inclinations of 135°, 145°, and 155°.

METHODS

A systematic review was performed of RSA for proximal humerus fracture using Preferred Reporting Items for Systemic Reviews and Meta-Analyses (PRISMA) guidelines. Radiographic and functional outcome data were extracted to evaluate tuberosity healing according to humeral inclination. Analysis was also performed of healed vs. nonhealed tuberosities.

RESULTS

A total of 873 patients in 21 studies were included in the analysis. The mean age was 77.5 years (range of 58-97) and the mean follow-up was 26.2 months. Tuberosity healing was 83% in the 135° group compared with 69% in the 145° group and 66% in the 155° group (P = .030). Postoperative abduction was highest in the 155° group (P < .001). No significant difference was found in forward flexion, external rotation, or postoperative Constant score between groups. Patients with tuberosity healing demonstrated 18° higher forward flexion (P = .008) and 16° greater external rotation (P < .001) than those with unhealed tuberosities.

CONCLUSION

RSA for fracture with 135° humeral inclination is associated with higher tuberosity healing rates compared with 145° or 155°. Postoperative abduction is highest with a 155° implant, but there is no difference in in postoperative forward flexion, external rotation, or Constant score according to humeral inclination. Patients with healed tuberosities have superior postoperative forward flexion and external rotation than those with unhealed tuberosities.

Can a functional difference be detected in reverse arthroplasty with 135° versus 155° prosthesis for the treatment of rotator cuff arthropathy: a prospective randomized study

BACKGROUND

The purpose of this randomized controlled trial was to compare humeral inclinations of 135° and 155° in patients undergoing primary reverse shoulder arthroplasty (RSA). Our hypothesis was that forward flexion would be higher in the 155° group but be associated with a higher rate of scapular notching.

METHODS

A randomized controlled trial was conducted on 100 primary RSAs performed with a humeral inclination of either 135° or 155°. The prostheses were otherwise identical and a neutral glenosphere was used in all cases. Functional outcome, forward flexion, external rotation, and scapular notching were assessed at a minimum of 2 years postoperatively.

RESULTS

There was no difference in range of motion or functional outcome scores between the 2 groups. In the 155° group, forward flexion improved from 76° to 135° (P < .001) and external rotation remained unchanged (29° vs. 30°; P = .835). In the 135° group, postoperative forward flexion improved from 78° to 132° (P < .001) and external rotation was unchanged (28° vs. 29°; P = .814). Scapular notching was observed in 58% of cases with a 155° inclination compared with 21% with a 135° inclination (P = .009).

CONCLUSION

With a neutral glenosphere there was no difference in postoperative forward flexion or external rotation after an RSA with a humeral inclination of 135° compared with 155°. Scapular notching was reduced with the use of 135° design compared with a 155° design but persists at a rate of 21% at 2-year follow-up in the absence of a lateralized glenosphere.