Relationship between proximal femoral morphology and bone mineral density around the stem and the effects of osteoporosis treatment in patients with femoral neck fracture: a multicentre prospective cohort study

Background: This study aimed to classify older patients with femoral neck fractures who underwent hemiarthroplasty using a full hydroxyapatite-collared compaction short stem to evaluate the change in bone mineral density (BMD) around the stem. Methods This multicentre, prospective study included 96 older patients with femoral neck fractures registered for surgery from November of 2018 to October of 2020, who were followed up for 1 year after surgery. The patients were classified into three types according to Dorr classification. The BMD around the stem of each patient was determined based on seven Gruen zones using dual-energy X-ray absorptiometry. Clinical scores were measured concurrently. Further, we compared the BMD change rate around the stem in terms of Dorr classification and clinical scores, and investigated the relationship between osteoporosis treatment intervention and the BMD change rate. Results After excluding patients with missing data, 40 patients were included in the analysis. The BMD change rate in zone 2 was significantly different between Dorr types B and C. Clinical scores did not significantly differ between the three groups. Regarding the relationship between osteoporosis treatment and BMD change rate, the pre-injury intervention group had significantly suppressed BMD change rate decline compared with the post-injury intervention and no-intervention groups in zones 1 and 7. Conclusion Careful follow-up examination is critical when performing hemiarthroplasty in patients with femoral neck fractures of Dorr type C because the BMD change rate may decline postoperatively. Pre-injury osteoporosis intervention therapy may suppress BMD loss around the stem.