Y Marczuk, PH Flurin, C Roche, T Wright, S Grey, R Jones, H Routman, G Gilot, J Zuckerman.
(Limoges, Bordeaux, Gainesville, Fort Collins, Asheville, Palm Beach, Weston, New York)
Scapular notching is the most common reported complication of reverse shoulder arthroplasty. Radiographs from 226 patients who received one particular reverse shoulder arthroplasty were analyzed to correlate prosthesis positioning to the clinical observation of notching.
Immediate post-op and the latest follow-up radiographs (21.3 ± 8.7 months) were collected from 226 patients (age = 72.9 ± 7.1 yrs; females = 155 and males = 71) who received a 38mm (n = 135), 42mm (n = 81), and 46mm (n = 10) Equinoxe reverse shoulder by 7 different surgeons at 7 different institutions through a deltopectoral approach. Each glenoid component was implanted in neutral, without an inferior tilt. Each patient’s radiograph was scored for scapular notching by the implanting physician according to the Sirveaux grading scale. Placement of the glenoid plate peg from the inferior glenoid rim and the amount of glenosphere overhang were measured from each AP radiograph using digital calipers. Prosthesis-scapular neck angle was measured from each AP radiograph using a goniometer. Each radiographic measurement was compared to the surgeon scored notching grade; a Student’s two-tailed, unpaired t-test was used to identify differences, where p<0.05 denoted a significant difference. Results The radiographic analysis demonstrated that 22 of 226 patients had a scapular notch (16 Grade 1 and 6 Grade 2; no Grade 3 or 4 notches were observed) for a scapular notching rate of 9.7%. Female patients (102 38mm and 38 42mm glenospheres) had a scapular notching rate of 9.7% (13 Grade 1 and 2 Grade 2) whereas male patients (19 38mm, 42 42mm, and 10 46mm glenospheres) had a scapular notching rate of 9.9% (3 Grade 1 and 4 Grade 2). Patients with 38, 42, and 46mm glenospheres had a scapular notching rate of 13.3% (13 Grade 1 and 5 Grade 2); 4.9% (3 Grade 1 and 1 Grade 2); and 0%, respectively. The average glenoid plate position for patients without a notch (19.1 ± 2.5mm) was significantly less (p = 0.037) than the average position for patients with a notch (20.1 ± 2.4mm). The average glenosphere overhang for patients without a notch (5.3 ± 2.5mm) was significantly more (p = 0.002) than the average overhang for patients with a notch (3.6 ± 2.4mm). The average prosthesis-scapular neck angle for patients without a notch (105.4 ± 14.6°) was not statistically different than the average angle for patients with a notch (105.8 ± 13.0°). Discussion and Conclusions Significant differences in both the glenoid plate position and glenosphere overhang were observed between patients with and without a notch. Gender differences result from differences in bone size, reflected by the 73.2% of males who received a 42 or 46mm glenosphere, compared to only 24.5% of females. Due to the progressive nature of scapular notching, additional follow-up is necessary to demonstrate that this particular reverse shoulder prosthesis has a scapular notching rate < 10%.