Sequential Transcutaneous Mechanical Femoral Lengthening of a Profoundly Short Skeletal Residuum and Subsequent Successful Transfemoral Osseointegration: A Case Report Describing a Novel Endo-Exo Intramedullary Stump Lengthening Device.

A 17-year-old adolescent girl presented to our specialty referral center to explore the possibility of osseointegration. Diagnosed with right distal femoral Ewing sarcoma at the age of two, she underwent a transfemoral amputation after 6 months of treatment, resulting in an extremely short residual femur of only 21.7 mm below the pyriformis fossa. The primary challenge was to first elongate the short stump to create a sufficient femoral residuum and then successfully perform osseointegration to enable independent mobility. The aim was to regenerate a good length of the bone to support an osseointegration implant to help her walk independently. After rehabilitation, the patient is mobilizing independently and has a level 3 K-value (activity). Her case illustrates the potential of combining advanced three-dimensional modeling and virtual planning, sophisticated design and manufacturing capabilities, and improving surgical techniques to achieve definitive reconstruction of an amputated limb. Such technological advancements promise to expand the possibilities for future innovations in limb reconstruction and patient rehabilitation. The limitation of this femoral residuum lengthening and staged osseointegration is the need for custom implant design and manufacturing, which is patient-specific and requires meticulous planning.