Background: Several treatment modalities have been described for the treatment of unicameral bone cysts (UBC). The aim of this study was to examine the outcome of various treatment modalities of UBC in a specific anatomic location, the humerus.
Methods: This study is a retrospective case-only study of patients with humeral UBC with minimum follow-up of 1 year. Medical records and radiographs were assessed and UBC healing status was determined based on most recent follow-up radiographs and divided into 3 groups (healed, partially healed, and not healed). Descriptive statistics were utilized to summarize study outcome.
Results: Sixty-eight patients (54 boys and 14 girls) with humeral UBC comprised the study population. Sixty-four cases (94.1%) presented with a pathologic fracture. Fifty-one cases were in the proximal metaphysis and 17 were in the diaphysis. Mean age at diagnosis was 9.2±3.7 years, and mean follow-up was 4.0±2.6 years. Twenty-five patients were treated with observation, 38 by injection (27 with steroids and 11 with bone marrow), and 5 by open surgery. Patients who underwent open surgery had relatively larger cyst length, width, and cyst index, and all healed or partially healed at last follow-up. UBC persistence was observed in 29% of diaphyseal and 27.5% of metaphyseal cysts. Of the 19 patients with persistence, 8 were treated with observation, 9 with steroid injection, and 2 with bone marrow injection. Inner wall disruption before injection was performed in 17 patients (24% did not heal), whereas 21 patients did not have inner wall disruption (33% did not heal). Twenty patients received >1 injection. Eleven patients complained of pain at the last visit (8 had a persistent cyst, 2 were partially healed, and 1 had a healed UBC).
Conclusions: Complete healing of humeral UBC is challenging to achieve irrespective of treatment modality. UBCs treated with open surgery tended to heal better. Unhealed cysts were more likely to be associated with pain.
Level of evidence: Level III-a retrospective comparative study.