MRI of the achilles tendon: A comprehensive review of the anatomy, biomechanics, and imaging of overuse tendinopathies

Abstract

The Achilles tendon is the largest tendon in the body; it plays an important role in the biomechanics of the lower extremity. It can withstand great forces, especially during sporting exercises and pivoting. The pathologies related to the Achilles tendon are diverse and many carry undesirable consequences. We retrospectively analyzed the images of patients who underwent examinations of the ankle/foot region to review the anatomy of the Achilles tendon and its surroundings and to search for pathologies consistent with overuse injuries. The anatomy of the tendon is described from origin to insertion. The imaging characteristics of the Achilles tendon including pitfalls are reviewed. We also describe the Achilles overuse injuries: paratenonitis, tendinosis, tendon tear, atypical tear, tendon re-tear, retrocalcaneal bursitis, retro-Achilles bursitis, Haglund's deformity, and tendon calcification. We present other entities like tendon ossification and failed transplanted Achilles tendon, with emphasis on MRI.

Ultrasonography and Low-field Magnetic Resonance Imaging of the Common Calcanean Tendon in a Rabbit Model for Tendinopathy Research: a Descriptive Study of Normal Anatomy

“…In transverse images, use of an ultrasound probe with a higher frequency range or higher magnetic field strength MRI unit might result in increased sensitivity allowing distinction of individual components of the common calcanean tendon in the rabbit. The echogenicity and signal intensity of the analyzed tendon observed in longitudinal/sagittal plane was generally comparable to that reported in the normal human calcaneal tendon (Bleakney and White 2005, Harris and Peduto 2006, Pierre-Jerome et al 2010). The differences were the presence of the hypoechoic superficial component as detected in the sonographic examination and the linear areas of higher signal intensity as seen in magnetic resonance which represented the epitenon.…”

“…This protocol was determined not only based on significant contribution of these tendons to the common calcanean tendon but also according to their applicability in tendinopathy research in a rabbit model (Young et al 1998, Oryan et al 2012. Sonograms and scans were assessed qualitatively with a description of normal appearance of elements analogical to those assessed in human Achilles tendon pathologies, that means echogenicity or signal intensity (depending on imaging technique) of the tendon, musculotendinous junctions, the region of calcaneal insertion, the paratenon, the pre-Achilles fat pad and the bursa of calcaneal tendon (Kamel et al 2003, Bleakney and White 2005, Harris and Peduto 2006, Leung and Griffith 2008, McGonagle et al 2008, Pierre-Jerome et al 2010, van Dijk et al 2011, Del Buono et al 2013). Morphometry of the common calcanean tendon was performed on longitudinal sonograms and sagittal T1-weighted MRI (magnetic resonance imaging) scans presenting median section of the crus.…”

“…Despite recent advances in the treatment protocols, their outcomes are still unpredictable due to the decreased mechanical properties of fibrovascular scarring and the degenerative nature of many tendon disorders (Kader et al 2002, Shapiro et al 2015. It has been stated that the calcaneal tendon (Achilles tendon) is one of the most frequently injured tendons in the human musculoskeletal system (Pierre-Jerome et al 2010, Del Buono et al 2013). Due to the complexity of tendon injury and the healing processes as well as differences among particular tendinopathic conditions, animal models are essential for addressing fundamental questions in tendon research (Thomopoulos et al 2015).…”

“…The pre-Achilles fat pad, the bursa of the calcaneal tendon, the calcaneal tendon enthesis itself as well as the fibrocartilages on the surface of the tendon and on the opposing calcaneal tuberosity, formed as a result of an intermittent contact between the tendon and bone, constitute the enthesis organ affected in the spondyloarthropathies of the Achilles tendon (Benjamin and McGonagle 2009). Additionally, the calcaneal tendon is an example of a tendon surrounded by the paratenon -a double-layered connective tissue membrane, separated from the tendon itself , Pierre-Jerome et al 2010. It is involved in Achilles tendon pathologies, classified as paratendinopathies (van Dijk et al 2011).…”

“…Experimental models used to investigate various treatment protocols are usually evaluated by means of histopathological, biochemical or mechanical examinations. However, in practice, diagnostic imaging along with clinical examination are commonly applied for the calcaneal tendon assessment (Bleakney and White 2005, Harris and Peduto 2006, Pierre-Jerome et al 2010, Del Buono et al 2013). Ultrasonography and magnetic resonance imaging provide a non-invasive assessment of tendons, allowing on defining stage of the extend and severity of the disease and evaluation of applied treatment effectiveness.…”