Development of an Anatomic Landmark-Based Measurement of the Achilles Tendon

Abstract

Category: Ankle; Sports 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 older people. With a high and increasing incidence of such a 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 techniques have been validated in measurement of Achilles tendon. 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 using ultrasound and anatomic landmark-based measurement techniques. Subjects sat upright on the exam table and legs were held in flexion at the knee with slight external rotation with the ankle held at 90o, allowing the lower leg to rest flat 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 ultrasound and anatomic landmark-based techniques for inter-rater reliability. The measurements were repeated one week later for intra-rater reliability. Ultrasound measurements had excellent inter-rater (0.93) and intra-rater (0.82) correlation coefficients, while good inter-rater (0.76) and intra-rater (0.86) correlation coefficients were observed among anatomic landmark-based measurements. Achilles tendon length measured with ultrasound and anatomic landmark-based techniques were compared using a paired t-test. Results: The anatomic landmark-based technique produces longer measurements of the Achilles tendon (23.2 cm (sd 2.6 cm)) compared to measurements made using ultrasound (22.4 cm (sd 2.6)) (p<0.001). On average, the anatomic landmark-based technique measures 0.8 cm (95% Confidence Interval: 0.4, 1.2) longer than the ultrasound technique. The intraclass correlation coefficient between the anatomic landmark-based and ultrasound measurements is 0.90. Conclusion: While the anatomic landmark-based technique produces a longer measurement of the Achilles tendon, it may still be a reproducible measurement tool. If the change in tendon length is of interest, this technique may be a valid and simple way to monitor that variable. Comparison with MRI may be warranted to better determine the accuracy of the anatomic landmark-based Achilles tendon measure. These results compared with MRI may set the stage for further evaluation of this measurement technique in the operating room in subjects undergoing ATR repair.