Risk factors of poor mid-term shoulder functional outcomes of osteosynthesis using antegrade intramedullary nailing for humeral shaft fractures: a retrospective study with a minimum 5-year follow-up.

ABSTRACT

BACKGROUND: Osteosynthesis using antegrade intramedullary nailing for humeral shaft fractures yields satisfactory bone union rates; however, it may adversely affect postoperative shoulder function. To date, factors affecting mid- or long-term shoulder functional outcomes following intramedullary nail fixation have not been clarified. In this study, we aimed to identify the risk factors for poor mid-term functional outcomes over 5 years postoperatively following antegrade intramedullary nail osteosynthesis for humeral shaft fractures. METHODS: We retrospectively identified 33 patients who underwent surgery using an antegrade intramedullary nail for acute traumatic humeral shaft fractures and were followed up for at least 5 years postoperatively. We divided the patients into clinical failure and no clinical failure groups using an age- and sex-adjusted Constant score of 55 at the final follow-up as the cutoff value. We compared preoperative, perioperative, and postoperative factors between the two groups. RESULTS: Five of the 33 patients had poor shoulder functional outcomes (adjusted Constant score < 55) at a mean follow-up of 7.5 years postoperatively. Proximal protrusion of the nail at the time of bone union (P = 0.004) and older age (P = 0.009) were significantly associated with clinical failure in the univariate analyses. Multivariate analysis showed that proximal protrusion of the nail (P = 0.031) was a risk factor for poor outcomes. CONCLUSIONS: The findings of this study provide new information on predictive factors affecting mid-term outcomes following osteosynthesis using antegrade nails. Our results demonstrated that proximal protrusion of the nail was significantly associated with poor mid-term functional shoulder outcomes. Therefore, particularly in older adults, it is essential to place the proximal end of the intramedullary nail below the level of the articular cartilage.