Outcomes of Retrograde Fibular Strut Allograft Medullary Insertion for Treating Humeral Unicameral Bone Cysts.

Background: Many unicameral bone cysts (UBC) can be resolved or treated conservatively. Managing persistent symptomatic UBCs in the humerus is particularly challenging. An effective surgical method with low complications is significant for treatment. This study evaluated the effectiveness of inserting a fibular strut allograft retrogradely into the humerus UBC, focusing on cyst healing, concurrent pathologic fracture union, and complications.

Methods: We conducted a retrospective analysis of medical records from 2001 to 2020 to review cases of UBCs who underwent surgery at our referral hospital. In cases where cysts persisted despite three steroid injections and were symptomatic or presented with a pathologic fracture, surgical intervention was considered. Out of the initial 43 patients, 15 met the inclusion criteria for this study, and they were treated with retrograde insertion of a fibular strut allograft into the medullary canal, comprising 10 males and 5 females. A cyst filled with bone within 24 months is considered healed in radiographic appearance. When areas of radiolucency remain, it is called residual. Fracture union was identified by observing the bridging of at least three of the four cortical views by bone performed three months after surgery. The Musculoskeletal Tumor Society (MSTS) scoring system was used to evaluate patients' functional outcomes.

Results: After a mean of 54.7 months follow-up, 13 patients demonstrated complete cyst healing. None of the patients exhibited delayed healing. Two patients displayed cyst healing with residual, which remained stable throughout the last follow-up. All fracture cases achieved union within three months postoperation. The patients exhibited favorable functional outcomes, with a mean MSTS score of 29.6 (28 to 30).

Conclusion: Retrograde fibular strut allograft insertion into the medullary canal effectively manages symptomatic UBCs in the humeral bone, especially those in or extending to the middle or distal regions. A comparative study is recommended for further validation.