Incidental intima-media wall changes in the lower-limb arteries : a case series in habitual distance runners

High-resolution ultrasound is a popular and cost effective imaging modality used in the practice of sport and exercise medicine for the evaluation of soft tissue injury. Indeed, this modality is the imaging investigation of choice in the evaluation of skeletal muscle injury, aponeurotic tears, ligament injuries, tendinopathy and evaluation of soft tissue swelling. It is also an important diagnostic modality in the evaluation of vascular conditions including deep venous thrombosis and peripheral arterial disease. A number of clinical ultrasonographers including the first author of this report have (during musculoskeletal ultrasound conducted for reasons of injury evaluation) noticed the presence of echogenic circular “bead” shaped calcifications in the arterial wall (intimamedia space) of the peripheral lower limb arteries in runners. The vessels identified with this phenomenon include the posterior tibial, anterior tibial, popliteal and (to a lesser extent) the superficial femoral arteries. Discussions with colleagues in the radiology, orthopaedic and vascular fields have failed to explain this finding. It has been suggested that this phenomenon might be a variant of Mönckeberg’s medial sclerosis which might be exacerbated by running, however literature searches targeting this phenomenon have failed to yield many results.[1] It is of interest that a literature search did identify a study of the mechanical stress effects on the cardiovascular adaptations of peripheral arterial calcifications among athletes.[6]

High-resolution ultrasound is a popular and cost effective imaging modality used in the practice of sport and exercise medicine for the evaluation of soft tissue injury.Indeed, this modality is the imaging investigation of choice in the evaluation of skeletal muscle injury, aponeurotic tears, ligament injuries, tendinopathy and evaluation of soft tissue swelling.It is also an important diagnostic modality in the evaluation of vascular conditions including deep venous thrombosis and peripheral arterial disease.
A number of clinical ultrasonographers including the first author of this report have (during musculoskeletal ultrasound conducted for reasons of injury evaluation) noticed the presence of echogenic circular "bead" shaped calcifications in the arterial wall (intimamedia space) of the peripheral lower limb arteries in runners.The vessels identified with this phenomenon include the posterior tibial, anterior tibial, popliteal and (to a lesser extent) the superficial femoral arteries.Discussions with colleagues in the radiology, orthopaedic and vascular fields have failed to explain this finding.
It has been suggested that this phenomenon might be a variant of Mönckeberg's medial sclerosis which might be exacerbated by running, however literature searches targeting this phenomenon have failed to yield many results. [1]It is of interest that a literature search did identify a study of the mechanical stress effects on the cardiovascular adaptations of peripheral arterial calcifications among athletes. [6]

Methods
This case series describes the appearance observed in the lower limb vasculature of three runners who underwent ultrasound evaluation of the lower limb due to musculoskeletal injury.All three athletes were in a similar age group (49-52 years), of similar build and have similar histories of many years of road-running.Two of the athletes are brothers, the third athlete is unrelated.
All athletes underwent ultrasound scanning of the lower limb for either ankle sprain or calf strain.A Philips Epiq 5 ultrasound scanner (Philips, Netherlands) using an 18 MHz transducer with harmonic imaging was used in the imaging evaluations.All athletes described in this study provided written consent for their clinical material to be used in this publication.
Images captured from ultrasound scanning of the three athletes described in Table 1 are shown in Figures 2 to 6.As a control image, an asymptomatic 50-year-old male underwent ultrasound scanning as a means to demonstrate the normal anatomy and provide a "control".The image from this individual is shown in Figure 1.The clinical and sporting characteristics of the three runners are shown in Table 1.

Discussion
This case series describes vascular beadlike calcifications as an incidental finding in the intima-media layers of the lower limb vasculature in three endurance runners who underwent musculoskeletal ultrasound scanning for lower limb soft tissue injury.Many practicing ultrasonographers have observed this phenomenon in endurance runners.
It is assumed that the nature of the hyperechoic regions described above are calcific in origin. [2]In the early stages of these lesions in younger runners, the deposits do not cause any posterior shadowing to suggest calcium as a component.It is therefore possible that the lesions seen might represent lipid or fibrotic deposits.Over time, however, the deposits do cause marked shadowing on ultrasound, to the point of preventing visualisation of sections of the vessel lumen (Figure 6).
Most of the literature describing vascular ultrasound investigations in the athletic and non-athletic populations show that they were performed as diagnostic tests secondary to the presence of vascular symptoms.For example, iliac artery stenosis in cyclists has been well researched and involves endofibrosis, a pathological process characterised by thickening of the vessel intima, causing progressive stenosis of the lumen and impaired blood flow. [3]Fibromuscular dysplasia is a further disorder that has been described but predominantly affects the medial or adventitial layers of the arterial wall and typically involves the renal or extracranial cerebrovascular arteries. [4]The condition described in this series is also clearly different from cystic adventitial disease, in which mucoid cysts develop within the adventitial layer of typically the popliteal artery, increasing adventitial thickness and compromising flow. [5]önckeberg's sclerosis has some similar features to the cases described in this series, but tends to result in a stiffening of the elastic layer of the arterial wall.In addition, it is usually observed in the major lower limb arteries of the elderly, but can occur in the head, neck and pelvis.It is important to note that the vascular calcifications described in this series were only noted in the arteries of the lower limb and not in the carotid vessels (Figure 7).It is also important to note that increased calcium and calcium scores in the coronary arteries of endurance runners has recently been described. [6]The clinical relevance of these findings is yet to be determined.
It is tempting to speculate that the deposits described may be related to an inflammatory process of the arterial walls due to the repetitive jarring impact of the foot on a hard surface.However, to the knowledge of these authors, no biopsies have been performed to establish the aetiology of the deposits.