**1. Introduction**

6

8

**\***

> Primary avascular necrosis of the humeral head (PANHH) is the result of the necrosis of the bone tissue and bone marrow of the humeral head. It often affects patients in their 4th or 5th decade. While many etiologies are linked to corticosteroid therapy or alcohol abuse, most of the time no causes are identified. Several studies have investigated the results of shoulder arthroplasty for PANHH. Total shoulder arthroplasty (TSA) [1–5] and hemiarthroplasty (HA) [1,6–11] have shown satisfactory clinical outcomes in short-, midand long-term follow-up (FU). It has been well demonstrated that post-traumatic necrosis resulted in inferior outcomes than PANHH [1,12,13]. Only two studies [1,4] have compared the results of HA and TSA but gathered primary and post-traumatic AVHH [1] or the two groups were not comparative in terms of age and age related factor [4]. Therefore, our aim was to assess the complications, the clinical and radiological outcomes of shoulder arthroplasty for PANHH in patients aged 60 years old or younger at the time of the

surgery. The hypotheses were that HA and TSA would (1) both improve clinical outcomes during the FU midterm (2) but would differ with TSA having a higher rate of complication than HA.

#### **2. Materials and Methods**
