Primary stability of a non-cemented humeral stem in Reverse Shoulder Arthroplasty in acute proximal humeral fractures. Prospective study.

Purpose Uncemented humeral stems have recently been introduced in the treatment of an acute proximal humeral fracture with a Reversed Total Shoulder Arthroplasty (rTSA). The objective of this study was to determine the primary stability of an uncemented humeral implant when used for acute proximal humeral fractures. Methods A prospective study that includes consecutive proximal humeral fractures treated with an uncemented rTSA (Delta Xtend with Global Unite Reverse for Fracture, DePuy, Warsaw, Indiana, USA). Three measures were obtained to assess the stability of the uncemented implant: the retroversion, the humeral stem height and the varus/valgus alignment of the humeral component. The three measures were done in both the CT scan obtained 24 hours after surgery, and the CT scan obtained at the 6-month follow-up. Among the patient sample included, five patients were randomly selected to be treated with a rTSA with a cemented humeral stem. They were used as the control. The five patients with the cemented stem underwent the same imaging protocol, and the same measures were also taken. The difference between both measures (24 hours after surgery and 6 months after surgery) were recorded. Results A total of 27 patients were included. There were 22 females and 5 males, with a mean age of 74.2. The mean difference in retroversion in the humeral component in the patients with the uncemented stem between the day after surgery CT and the CT scan at the 6th month was 0.4º (SD 5.1º). However, the mean difference in retroversion in the humeral component in the patients with the cemented stem between the day after surgery CT and the CT scan at the 6th month was 4.4º (SD 5.2º). There was no significant difference between them ( p  = 0.155). No other significant difference was found between uncemented and cemented humeral stems regarding humeral stem height ( p  = 0.574) nor varus/valgus alignment ( p  = 0.287) Conclusions There is good primary stability of an uncemented stem in acute proximal humeral fractures treated with an rTSA, as far as retroversion, humeral stem height and varus/valgus alignment are concerned.