Purpose: To evaluate the role of fractures on pathologic bone in healing of proximal humerus unicameral bone cysts (UBCs) and investigate the clinical factors that affect healing of UBCs after fractures on pathologic bone.
Methods: This prospective study was carried out between 2002 and 2014. We evaluated 56 patients with a UBC accompanying fractures on pathologic bone in the proximal humerus. Clinical data were collected from the patients' medical records. Age, gender, degree of fracture displacement, location of cyst, and cyst size were investigated, and we assessed how these factors affected cyst healing.
Results: The overall healing rate of UBCs 1 year after fracture was 66% (37 of 56 cases). The healing rate was significantly lower in pubescent patients (10-14 years old; 45%) than in those who were 9 years old (76%) or 15 years old (80%). The rate of healing of fractures in the metaphysis (53%) was lower than that of breaks in the diaphysis (85%). The mean cyst ratio was 1.31 in the 37 patients who experienced cyst healing within 1 year and 1.79 in the 19 patients who needed surgical treatment within 1 year.
Conclusion: In latent lesions and in patients who are older (after puberty), UBCs of the humerus after fracture have better clinical results than do active lesions and those in younger patients (before puberty). Fractures on pathologic bone in proximal humerus UBCs often dramatically decrease cyst size, and patients with such fractures have excellent clinical results in terms of healing rate.
Keywords: cyst healing; cystic ratio; fractures on pathologic bone; unicameral bone cysts (UBCs).