Comparison of Mid-term Outcomes of Total Shoulder Arthroplasty for B2 and A Glenoids Treated with Trabecular Metal Glenoid Components

Abstract Background : Treatment of B2 glenoids in total shoulder arthroplasty (TSA) has been associated with worse clinical outcomes and increased rates of glenoid loosening. The purpose of this study was to describe and compare the mid-term outcomes of TSA using a trabecular metal-backed glenoid in patients with B2 and A glenoids. Methods : Patients who underwent anatomic TSA with a trabecular metal-backed glenoid component (second generation Trabecular Metal glenoid) for primary osteoarthritis and had minimum 5-year follow-up were reviewed. All patients underwent eccentric glenoid reaming to treat biconcavity, if present. Preoperative imaging was reviewed and patients were divided into two groups: Type A and Type B2. Mid-term outcome measures including patient-rated outcome scores (PROMIS and ASES) and shoulder range of motion (ROM) were determined. ASES score was compared between groups. Radiographs were graded for radiolucent lines and posterior humeral head migration and evaluated for glenoid loosening. Results : 22 patients had Type A glenoids and 22 patients had B2 glenoids. 16 patients in the A group and 18 patients in the B2 group had full radiographic and physical exam follow-up. Both groups had similar follow-up (6.7 ± 1.1 years A, 6.6 ± 0.9 years B2, p=0.88). Groups were similar in terms of age at surgery, gender distribution, body mass index, severity of medical comorbidities and hand dominance distribution. The B2 patients had a mean preoperative glenoid retroversion of 17.5° ± 6.7° and posterior subluxation of 8.5% ± 5.3%. No patients in either group had evidence of glenoid loosening at follow-up. No patients required revision surgery. 9/16 in the A group had evidence of mild radiolucent lines (8 grade 1, 1 grade 2). 8/18 patients in the B2 group had mild radiolucencies (all grade 1). 2/16 Type A and 6/18 B2 patients had evidence of posterior humeral migration, but all cases were graded as mild. Both groups had similar follow-up mean ASES scores (95.5 A, 89.0 B2, p=0.25). Conclusion : At minimum 5-year follow-up, patients who underwent TSA with a trabecular metal-backed glenoid component demonstrated excellent clinical and patient-reported outcomes regardless of preoperative glenoid morphology (A or B2). No patients in either group had evidence of glenoid loosening or required revision surgery. These favorable mid-term outcomes of trabecular metal-backed glenoids in B2 deformities need to be followed longitudinally to determine long-term durability.