Factors Affecting Union after Capanna Reconstruction

Resection of long-bone tumors often leaves large skeletal defects. Since the late 1980s, surgeons have used the “hybrid” Capanna technique—a vascularized fibular graft inlaid in a massive bone allograft—to fill those voids, with good functional outcomes reported. In the November 20, 2019 issue of The Journal of Bone & Joint Surgery, Li et al. report on factors influencing union after the Capanna technique.

The authors radiographically evaluated Capanna-technique reconstructions in 60 patients (10 humeral, 33 femoral, and 17 tibial) and correlated allograft-host union time to the following variables:

• Patient age
• Tumor site
• Adjuvant treatment (e.g., chemotherapy)
• Previous surgical procedures
• Defect length
• Fixation method
• Fibular viability (assessed with a bone scan 10 days after reconstruction)

They also histologically analyzed a retrieved specimen from one patient.

Among these 60 reconstructions, the mean defect length was 16 cm, and the mean time to union of the constructs was 13 months. The overall survival rate of the constructs was 93% at the latest follow-up.

Multivariate linear regression revealed no correlation between allograft-host osseous union time and patient age, defect length, tumor site, or fixation method. Conversely, devitalization of the transplanted fibular graft, chemotherapy administration, and a previous surgical procedure were associated with a prolonged union time. Histologically, the allograft-host cortical junction was united by callus from periosteum of both the host bone and the fibular graft.

Li et al. conclude that “ensuring patent vascular anastomoses of the transplanted fibula is crucial to prevent delayed or nonunion.” They also suggest that Capanna-technique patients who have any of the 3 “adverse factors” noted above should be treated with extended postoperative immobilization and delayed weight-bearing.