The goal of this clinical trial is to learn if an ultrasound can measure the length of an internal tibia and femur lengthening rod. The main questions it aims to answer are:

Can an ultrasound be used to measure the length of an internal magnetic lengthening nail in a tibia or femur? Can an ultrasound measure the rod lengthening as well as an ultrasound? Researchers will compare the length of an internal magnetic lengthening rod with both x-rays and ultrasound

Participants will:

Have standard x-rays every week They will also have an ultrasound of the femur or tibia

Limb lengthening with expanding intramedullary rods has become the standard of care for limb lengthening procedures. The procedure entails performing an osteotomy of the short bone and placing a mechanical expanding intramedullary nail. The aim of the study is to explore the role of ultrasound to measure tibia and femur lengthening procedures and compare the accuracy to standard radiographs.

The study design is a prospective, pilot study of 5 tibias and 5 femurs. Measurements of the femurs and tibias will be obtained in 3 separate locations to try to identify areas that can be visualized and measured by an ultrasound. The cost of the ultrasound will be compared to the cost of x-rays, and any pain regarding imaging modalities will also be compared

Inclusion Criteria:

• Patients undergoing tibia or femur lengthening with an intramedullary mechanical rod.

Exclusion Criteria:

• Patients who underwent lengthening procedure with any other device such as external fixator.
• Patients under 8 years old and over 21 years of age