Is the critical shoulder angle a risk factor for symptomatic cuff tear after proximal humerus fracture treated with antegrade intramedullary bent nail?

BACKGROUND: Antegrade intramedullary nailing is one of the proposed techniques for proximal humerus fracture. High rate of bone union and favorable outcomes are reported, but it does have its drawbacks, particularly concerning the potential for rotator cuff injuries associated with the insertion point of a bent nail. Recently, the critical shoulder angle (CSA) was recognized as a risk factor for symptomatic cuff tears and retear after a repair. It is defined as the angle between the glenoid plane and the lateral acromial edge. The aim of the study is to assess if CSA correlates with symptomatic cuff tear and poor outcomes after antegrade intramedullary nailing for proximal humerus fracture.METHODS: We performed a retrospective analysis of 64 patients surgically treated for a PHF between January 2019 and December 2021, using a short bent nail. The CSA was measured preoperatively on CT scan according to Spiegl method. The cohort was divided based on the CSA: under 35° and equal to or greater than 35°. Furthermore, the population was also divided based on the age: under 75 years old and equal to or greater than 75 years old. Constant-Murley Score, DASH score, and the VAS were collected 1 year postoperatively. Symptomatic cuff tear was considered as a score greater or equal to 4 according to Litaker score.RESULTS: Patients under 75 years with CSA equal to or greater than 35° showed worse outcome than the patients with the same age but CSA lower than 35°, P=0.0083 for Constant-Murley Score and P=0.0367 for DASH score.CONCLUSIONS: A CSA equal to or exceeding 35° in patients under the age of 75 could influence the one-year clinical outcome following an AIN for PHF, using a bent nail.