Comparison of a Simple Anatomic Landmark-Based Achilles Tendon Measurement with Ultrasound and MRI Measurements

Abstract

Category: Ankle; Trauma Introduction/Purpose: Achilles tendon ruptures (ATRs) occurred with an incidence of 2.5 per 100,000 person-years in 2016. This rate has been increasing over the last decade and it has been postulated that this is due to the increasing activity level of an aging population. With a high and increasing incidence of this significant injury, further investigation must be done to optimize the treatment of ATRs. The degree of tendon lengthening has been correlated with clinical outcomes, with greater elongation being associated with worse outcomes. MRI and ultrasound (US) techniques have been validated in Achilles tendon measurements. We sought to develop a reliable, reproducible, and accurate measurement technique utilizing the manual palpation of anatomic landmarks that will be cost effective as well as convenient to perform, particularly intraoperatively. Methods: Both lower legs of 10 healthy subjects without history of Achilles tendon injury were examined. For US and anatomic landmark-based (ALB) measurements, subjects' ankles were held at 90o with the lateral aspect of the lower leg resting on the exam table. The length from the medial head of the gastrocnemius to the bottom of the non-compressed heal pad was measured by three raters using the US and ALB techniques. Two of those raters repeated the measurements one week later. MRI studies were obtained with ankles held at 90o. Using imaging software, the above measurements were made in sagittal and coronal series. A repeated measures mixed model method was utilized to model the measurement type and the length of the Achilles tendon. The length of the Achilles tendon measured by each measurement type was estimated with least square means. All pairwise comparisons were considered. Results: The Achilles tendon length was similar on the left [23.4 cm (95% CL: 22.3 cm, 24.5 cm)] and right [23.5 cm (95% CL: 22.4 cm, 24.6 cm)] legs. The average Achilles tendon length measured with the ALB technique was 23.2 cm (95% CL: 21.9 cm, 24.6 cm). The average Achilles tendon length measured with the US technique was 22.4 cm (95% CL: 21.0, 23.8). The average Achilles tendon length measured on the sagittal view of MRI was 24.1 cm (95% CL: 22.7, 25.4). The average Achilles tendon length measured on the coronal view of MRI was 24.2 cm (95% CL: 22.8, 25.5). Pairwise comparisons of the measurement types were not significantly different from 0. Conclusion: The ALB measurements were not statistically different from MRI or US. With orthopaedic surgeons in need of simple, noninvasive, and cost-effective methods to assess tendon length, the authors propose this ALB technique or US as valid ways to monitor that variable both during and after repair. These results set the stage for further evaluation of this measurement technique in the operating room in subjects undergoing ATR repair.