Prosthetic design of reverse shoulder arthroplasty contributes to scapular notching and instability

Table 1 Characteristics of 58 adults who underwent 65 reverse total shoulder arthroplasties, 2004-2011

Characteristic	Grammont group (n = 18)		Lateral-design group (n = 47)		P-value
	Mean ± SD	n (%)	Mean ± SD	n (%)
Male sex		121 (67)		311 (66)	NA1
Age (yr)	69 ± 7.3		70 ± 8.4		0.722
Follow-up (mo)	43 ± 15		32 ± 7.9		0.0004
Dominant side affected		12 (67)		21 (45)	NA
Workers compensation		02 (0)		22 (3.4)	NA
Glenoid sphere diameter
32 mm		01 (0)		28 (60)	NA
≥ 36 mm		181 (100)		19 (40)	NA

¹Number of shoulders;

²Number of patients. NA: Not applicable; SD: Standard deviation.

Table 2 Scapular notching and instability by prosthesis design in 65 cases of reverse total shoulder arthroplasty with minimum 2-year follow-up, 2004-2011¹

Parameter	Grammont group (n = 18), n (%)	Lateral-design group (n = 47), n (%)	P-value
Scapular notching	13 (72)	11 (23)	< 0.0012
Notching severity5
Grade 1	7 (39)	8 (17)	> 0.0013
Grade 2	2 (11)	1 (2.1)	NA4
Grade 3	2 (11)	2 (4.3)	NA4
Grade 4	2 (11)	0 (0)	NA4
Instability6	3 (17)	0 (0)	0.019

¹NA: Not applicable;

²P-value from two-tailed Fisher exact test;

³Adjusted for length of follow-up using general linear model;

⁴Small values prevented determination of significant differences;

⁵Notching severity was measured according to Sirveaux classification[15];

⁶Instability was determined using clinical examination and radiographic evidence of component dislocation.

Table 3 Glenoid position by prosthesis design in 65 cases of reverse total shoulder arthroplasty, 2004-2011

Parameter	Grammont group (n = 18), mean ± SD	Lateral-design group (n = 47), mean ± SD	P-value
Glenoid position (mm)
Inferior glenoid osseous rim to lowest point of glenoid sphere[23]	1.5 ± 2.1	-0.6 ± 3.3	0.004
Peg-glenoid rim distance[16]	22.6 ± 1.7	21.4 ± 3.3	0.066
Glenoid inclination (°)
Inclination angle[23]	93.2 ± 15.3	101 ± 11.7	0.027
Prosthesis-scapular neck angle[16]	102 ± 21.3	106 ± 17.1	0.368
Prosthesis-scapular bone angle[24]	126 ± 16.9	132 ± 11.0	0.219