A comparison of different fixation methods involving transarticular pins and locking plates for shoulder arthrodesis in dogs using finite element analysis.

Objective: The purpose of this study is to compare 3 fixation methods for shoulder arthrodesis using finite element analysis.

Methods: Three dogs from different breeds, previously evaluated for shoulder joint arthrodesis, were selected, and their scapula and humerus were extracted from 2019 CT data to create computer models of shoulder arthrodesis. They were fixed with transarticular pins, a plate and screws, or a combination of all 3. The stress distribution of the implants and the dislocation at the osteotomy site were compared under a compression load of 35 N, an internal rotation of 1 Nm, and an external rotation of 1 Nm.

Results: The stress distribution on the implants was reduced when all 3 implants were used. The relative dislocation at the osteotomy site is the greatest when fixed solely with the transarticular pins and least when all the implants are used under any loads. The impact of adding transarticular pins was more prominent under the rotational load than under the compression load.

Conclusions: The plate and screws are the primary load-bearing components under the compression and rotational loads. However, adding the pins decreases the stress distribution on other implants and prevents motion at the osteotomy site, particularly under rotational load.

Clinical relevance: This study indicated that using transarticular pins in conjunction with a plate and screws for shoulder arthrodesis has the potential to reduce the risk of implant failure and may be advantageous for minimizing the risk of malunion or nonunion.