Assessing the Reliability and Validity of Ultrasound to Evaluate Large Muscle Atrophy in the Lower Limbs

Lower limb surgeries, particularly knee surgeries, are prevalent procedures in US orthopedic departments. Many of these procedures require a postoperative period of immobilization, which may be lengthy for surgeries involving ligament reconstruction, fractures, meniscal repairs, or cartilage transplantation. This leg immobilization results in rapid and significant loss of skeletal muscle mass. Even for shorter periods of immobilization, atrophy occurs within as little as 5 days of immobilization in healthy subjects, and the largest extent of post-operative atrophy takes place during the first two weeks of being immobilized (1)(2).

Muscle atrophy can prolong recovery times and directly impact the safety of a patient's return to activity progression. Providers need a reliable, valid method of assessing postoperative muscle atrophy which is cost-effective, safe, and simple to implement in a clinical setting (4). The aim of this study is to demonstrate that ultrasounds are reliable and valid tools for measuring large lower limb stabilizers such as the rectus femoris. Upon proving reliability and validity, we aim to use the ultrasound to track and characterize rectus femoris atrophy after a common lower limb surgical procedure; anterior cruciate ligament (ACL) reconstruction. Success of this validation study would support the use of ultrasound to monitor large muscle atrophy after lower limb orthopedic surgical procedures, and to evaluate the impact of muscle health interventions. Our ultimate research aim is to develop a reliable, valid ultrasound measurement technique to evaluate promising perioperative interventions for attenuation of muscle atrophy following surgical procedures of the knee.

Patients and Methods:

Part I: Ultrasound measurements of the rectus femoris will be obtained in approximately 50 healthy volunteers. Thigh circumference measurements will be taken as well. The ultrasound (US) images will be de-identified with research identifier (ID) only and transferred from the US unit to a secured folder on a research drive, and associated only with basic demographic information such as age, gender, height, and weight. Ultrasounds currently in use at the UIHC Sports Medicine Clinic will be used. Measurements will be made at a point mid-way between the anterior superior iliac spine and the superior border of the patella.

Part II: Following validation in healthy controls, approximately 100 ACL reconstruction patients will be enrolled for a longitudinal study which utilizes the same ultrasound methods and equipment to track their rectus femoris size at a preoperative visit, and during the 6 week, 3 month, and 6 month standard postoperative follow-up visits. Thigh circumference measurements will be taken as well. The ultrasound images will be de-identified with research ID only and transferred from the US unit to a secured folder on a research drive, and associated only with basic demographic information such as age, gender, height, and weight; along with basic survey data on physical therapy adherence. The patients will not incur any cost from the ultrasound testing, and the ultrasound testing will occur at the same clinical location (UIHC Sports Medicine Clinic) as their follow-up visits.