The Copenhagen Achilles Length Measurement Performed at Time of Acute Achilles Tendon Rupture is Correlated to Tendon Elongation After 1 Year

Abstract

Elongation of the tendon has been proposed as the most important factor leading to poor outcome after acute Achilles tendon rupture (ATR). The aim of this paper was to investigate if Amlang's ultrasound classification (AmC) or the Copenhagen Achilles Length Measurement (CALM) when assessed in the acute phase after ATR could predict elongation 1 y after rupture. 107 males and 27 females, aged 18 to 70 y and treated nonsurgically were included. AmC and CALM were assessed at time of rupture and correlated to elongation measured with CALM and Achilles Tendon Resting Angle (ATRA) at 1 y. Receiver operating characteristic (ROC) analysis was performed to determine a cut off for acceptable elongation at time of rupture given that elongation at 1 y was not to exceed 10%. AmC showed no statistically significant correlation. CALM at baseline correlated to CALM at 1 y r = 0.214 (p = .02) and ATRA at 1 y r = 0.218 (p = .02). The ROC model had AUC = 0.67 for 7% elongation at baseline yielding a sensitivity of 0.77 and specificity of 0.50 for predicting elongation of 10% or more at 1 y. Elongation of the Achilles tendon at baseline measured with CALM was weakly correlated to elongation at 1 y. A cut off of 7% elongation at baseline caught 77% of patients who, when treated nonsurgically, ended up with an elongation above 10% at 1 y. A prospective trial investigating CALM as part of a selection algorithm for deciding between operative and nonoperative treatment is needed.