Bone adaptation of a biologically reconstructed femur after Ewing sarcoma: Long-term morphological and densitometric evolution.

Combining bone allografts and vascularized fibular autografts in intercalary reconstructions after resection of bone sarcomas is of particular interest in young patients as it facilitates bone healing and union and helps reduce fractures. However, adverse events related to bone adaptation still occur. Bone adaptation is driven by mechanical loading, but no quantitative biomechanical studies exist that would help surgical planning and rehabilitation. We analyzed the bone adaptation of a successful femoral reconstruction after Ewing sarcoma during 76-month follow-up using a novel methodology that allows CT-based quantification of morphology and density. The results indicated that the vital allograft promoted bone adaptation in the reconstruction. However, an overall negative balance of bone remodeling and a progressive mineral density decrease in the femoral neck might threaten long-term bone safety. These concerns seem related to both surgical technique and mechanical stimuli, where a stiff metal implant may determine load sharing, which negatively affects bone remodeling.