Synthetic Bone Graft Substitute for Treatment of Unicameral Bone Cysts.

BACKGROUND: Treatments for unicameral bone cysts (UBCs) have high documented failure rates (27% to 63%) because of recurrence or persistence of the cyst, similar to nonoperative management. Recent evidence suggests that filling of the defect with a synthetic bone graft substitute (SBGS) supports the weakened cortex and promotes new bone growth. A calcium sulfate, brushite, calcium phosphate, composite graft material (PRODENSE, Wright Medical, Memphis, TN) has been evaluated as a substitute for autogenous or allogenous graft in animal and human studies. The purpose of this study was to compare the rates of revision surgery in patients treated for UBCs with an SBGS compared with historical treatments with allograft or autologous bone marrow aspirate.

METHODS: The authors reviewed 27 of 33 patients (age, 6 months to 21 years) an average of 121 months (range, 32 to 228) after filling of a UBC with an injection of SBGS (n=18) versus allograft or autologous bone marrow aspirate (n=9) between June 2008 and December 2017. Six patients with no follow-up were excluded. Groups did not differ in age at surgery, sex (19/27 male), history of pathologic fracture (22/27), or previous treatments (11/27). The primary outcome was the rate of revision surgery. Secondary outcomes included revision surgery-free survival as evaluated by the log-rank test, rate of postoperative fracture, persistent cysts, continued pain, and/or growth disturbance at the final follow-up.

RESULTS: Seven of 9 patients treated with allograft or autograft underwent revision surgery for postoperative pathologic fracture (n=2) or resorption of the graft (n=5) compared with 2 of 18 patients injected with the SBGS, both treated for graft resorption. The use of SBGS was associated with a decreased need for revision surgery over all time periods (hazard ratio, 0.14; 95% confidence interval, 0.03-0.05). There was no significant difference between postoperative fracture (2/18 vs. 2/9), persistent cyst (7/18 vs. 5/9), pain (0/18 vs. 2/9), or growth disturbance (1/18 vs. 3/9).

CONCLUSIONS: Treatment of UBCs with SBGS may decrease reoperation rates. Initial radiographic appearance after SBGS treatment shows solid structural support, followed by new bone formation. This appearance may lead to a less aggressive approach in considering revision surgery.

LEVEL OF EVIDENCE: Level III-retrospective comparative study investigating the results of treatment.