MR-IMAGING OF ACHILLES-TENDON IN PATIENTS WITH FAMILIAL HYPERLIPIDEMIA - COMPARISON WITH PLAIN FILMS, PHYSICAL-EXAMINATION, AND PATIENTS WITH TRAUMATIC TENDON LESIONS

OBJECTIVE. The purpose of this study was to evaluate the MR imaging ch aracteristics of Achilles tendons in patients at risk for tendon xanth omas because of familial hyperlipidemia and to compare these findings with those seen on plain radiographs and physical examination, We also wished to determine if MR imaging could be used to differentiate xant homas from traumatic tendinopathy in a second group of patients who ha d no history of hyperlipidemia but who had a history of trauma to the Achilles tendon. SUBJECTS AND METHODS. We evaluated the MR imaging stu dies of 26 Achilles tendons in 13 patients with heterozygous familial hypercholesterolemia (n = 11) and type III dysbetalipoproteinemia (n = 2). The size, shape, and signal characteristics of the Achilles tendo n were recorded. A tendon was considered abnormal by MR if there was h igh signal, a convex anterior border, or an anteroposterior measuremen t greater than 7 mm. Findings on plain radiographs and physical examin ation of the Achilles tendons were evaluated in the same group of pati ents. In the group of patients with hyperlipidemia, palpable abnormali ties of the Achilles tendon were present in 14 of 26 tendons. Plain ra diographs were interpreted as showing abnormalities in 18 of the 26 te ndons. In a second group of 21 tendons in patients with no history of hyperlipidemia but with traumatic tendinopathy, studies were evaluated for the size, shape, and signal characteristics of the Achilles tendo n. RESULTS. On MR images, 24 of 26 tendons showed signal abnormalities , and 19 of 26 were enlarged. Abnormal signal was a diffuse stippled p attern with many low-signal round structures of equal size surrounded by high-signal material on all pulse sequences. Abnormal signal was se en in tendons of both normal and abnormal size. Bilateral and symmetri c changes were found in all but one patient. Tendinopathy in patients without known hyperlipidemia appeared indistinguishable from tendon xa nthomas in six (29%) of 21 tendons, The other tendons (71%) were disti nctly different from xanthomas without a uniform stippled signal patte rn. CONCLUSION. MR imaging of patients with familiar hyperlipidemia sh owed an abnormal stippled signal pattern with or without enlargement o r abnormal configuration of the tendon. MR imaging is a more sensitive method than physical examination and plain films for detecting abnorm alities in Achilles tendons of patients with hyperlipidemia. Although the MR signal pattern of xanthomas is often different from that of par tial tendon tears, tendon degeneration, or tendinitis, a significant o verlap in appearance can be observed and the MR appearance of a xantho ma is not pathognomonic.