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Objectives and questions: Glenoid bone loss with strong medialization poses a technical challenge in reverse shoulder arthroplasty (RSA) to achieve ideal central screw positioning. To avoid the use of a “post extension” but not missing out on the effects of lateralizing center of rotation, metallic glenoid augmentation with press-fit impaction can be performed using solely fixation with peripheral screws and without the use of a central screw.

The aim of this study is to evaluate clinical and radiological results of metallic glenoid augmentation using a press-fit impacted “short post” in primary RSA in patients with substantial glenoid defects.

Material and methods: In this retrospective study from prospectively collected data sets, patients with substantial glenoid defects in whom no central screw could be used intraoperatively were identified. Metallic glenoid reconstruction was performed using an impacted short post and definitively fixed solely with peripheral screws and no central screw. On the glenoid side, metallic augmentation was performed using a porous titanium baseplate with centric (+3 mm) or eccentric (full-wedge) offset. On the humerus two different short stems (Ascend Flex or Perform humeral) were implanted.

Inclusion criteria was a completed clinical-radiological follow-up (FU) of at least 24 months and intraoperative poor bone stock where no central screw implantation was possible.

Clinical evaluation was performed preoperatively and at the follow-up examinations using the Constant Score (CS) and Subjective Shoulder Value (SSV), external rotation, flexion and abduction strength. Radiologic evaluation included signs of loosening and osteolysis as well as scapular notching and peri-prosthetic fractures or instability.

Results: A total of 50 shoulders of 48 patients (f: 29; age=70.4 years) were implanted due to reduced quantitative and qualitative bone quality using press-fit “short post” and metallic augmentation (full-wedge n=40; concentric augment +3 mm n=10). A total of 26 patients had a completed clinical-radiologic follow-up of 24 months:

CS improved from preoperative 27.5 (14–40) to 69.2 (43–89) points (p<0.001), SSV increased from 23.1% (0–40) to 80.3% (45–100) (p<0.001). Active external rotation was 33° (5–70), flexion 142° (105–165) at two years post-op with an abduction strength of 4.7 (1–9.4) kg. There were no complications such as peri-prosthetic fractures, instability, scapular notching, osteolysis or signs of loosening.

Discussion and conclusions: Metallic glenoid augmentation in primary RSA using a press-fit impacted “short post” without post-extension allows sufficient implant fixation and stability in patients with poor bone stock presenting very good and reproducible results.