## 4 Discussion  
Based on the main findings of this study, anatomic TSA performed better than SHA for GHOA. At last follow-up, the TSA group demonstrated greater flexion, abduction, and elevation. ASES and VAS were both greater in the TSA group. TSA demonstrated a higher age-adjusted Constant score and a lower rate of revision surgery. The results of the multivariate analysis suggested that the surgical outcome was strongly influenced by the preoperative performance status. A previous systematic review, which analyzed 1952 patients, showed that TSA was effective in reducing pain and improving ROM and patient satisfaction. The same study evidenced that TSA resulted in a significantly lower rate of revision surgery (6.5% versus 10.2%) [23]. A more recent review involving 2111 procedures (1783 TSA and 328 SHA) also found a lower revision rate in TSA (7% versus 13%) [24]. A previous meta-analysis involving 62 TSA procedures revealed a higher University of California at Los Angeles  
Figure 4: Meta-analysis of the comparison: Revision rate. Figure 3: Meta-analysis of the comparison: Age-adjusted Constant score. (UCLA) Shoulder Score than SHA [25]. Similarly, in a more recent meta-analysis including 153 procedures, TSA provides better clinical results than SHA [26]. Indeed, higher UCLA Shoulder Score and A SES were found in the TSA group [26]. In contrast, there was no significant difference between TSA and HA in revision, Western Ontario Osteoarthritis of the Shoulder (WOOS) index, and instability [26]. The present systematic review and meta-analysis confirmed similar findings on a larger scale, analyzing more procedures and outcomes of interest compared with previous studies. Pain relief and full functional recovery are the primary goals of shoulder prostheses [62]. TSA aims to restore the physiological biomechanics of the shoulder joint: spherical size, orientation, center of rotation, capsular tension, joint stability, and range of motion [63]. Neck inclination, humeral head diameter, thickness, height, retroversion, offset, and acrom-humeral distance are the main parameters to follow for a successful implant [64; 65; 66]. Polyethylene wear, aseptic loosen, and the erosion of the glenoid component are the most common complication of TSA [24; 67; 68; 70]. SHA is easier to perform and requires shorter surgical duration and learning curve [71]. HA is advantageous in the early stages of OA with eccentric GHOA [50]; however, given the higher risk of glenoid bone erosion, its use in advanced GHOA is controversial [72]. TSA, in contrast, is more demanding, with greater tissue damage, blood loss, and recovery time [73], but humeral component loosening is uncommon [74; 75]. However, TSA provides greater joint stability, less pain, and increased ROM, especially in internal rotation [76; 77], as highlighted by long-term follow-up studies [22; 78]. In addition, TSA showed a lower rate of revision surgery, and is more cost effective than SHA [30; 79; 80]. Indeed, although TSA has higher initial costs, primarily from the longer operative time and the expense of the glenoid component [81], the lower revision rate of surgery and higher health-related quality-of-life (calculated by quality-adjusted life years, QALYs) make TSA more effective and less costly than the alternative [79]. Glenoid component failure is the most common complication leading to revision surgery following TSA [68; 82; 83], and may discourage the use of glenoid components in younger patients desiring higher activity levels [68; 82; 84; 85; 86]. The present study has several limitations. The retrospective design of most of the included studies has a negative effect on the reliability of the conclusions. Given the limited quantitative data available in the current literature, surgical techniques, approaches, and implants were not analyzed separately. Between-study heterogeneity in the eligibility criteria was shown.