SLR - March 2018 - Nisha N. Shah

Ultrasound Characteristics of the Achilles Tendon in Tophaceous Gout: A Comparison with Age- and Sex- Matched Controls

Reference: Carroll, Matthew, et al. Ultrasound Characteristics of the Achilles Tendon in Tophaceous Gout: A Comparison with Age- and Sex-Matched Controls. The Journal of Rheumatology, vol. 44, no. 10, 1 Aug. 2017, pp. 1487–1492.

Scientific Literature Review

Reviewed By: Nisha N. Shah, DPM
Residency Program: Grant Medical Center, Columbus, OH

Podiatric Relevance: As foot and ankle surgeons, we routinely treat gout and address Achilles tendon pathology. Tophus formation has been identified as a risk factor for the development of musculoskeletal problems and destruction of joint movement. Previous studies have shown the presence of monosodium urate crystals in the Achilles tendon with 40 percent having both entheseal and nonentheseal involvement. Ultrasound is a noninvasive study that can be used to assess urate deposition, joint damage and inflammation. The authors’ purpose of this study was to investigate the frequency and distribution of ultrasound characteristics of the Achilles tendon in people with tophaceous gout compared to age- and sex-matched controls.

Methods: This was a prospective study that looked at 48 people, 24 with gout and 24 controls. The participants were recruited from outpatient clinics with age- and sex-matched controls. Patients were included if the 1977 American Rheumatism Association classification criteria were met, in addition to the presence of one palpable tophus. Ultrasound examination of the Achilles tendon was performed by a single musculoskeletal radiologist. Six months after completion of data, the images were reviewed by the same radiologist. The Achilles tendon was divided into three zones: insertional, preinsertional and proximal to the midsection. The following characteristics were recorded with respect to their zone location: tophus formation, tendon vascularity, tendon morphology, entheseal formation, bursal morphology and calcaneal bone contour. Interobserver reliability was assessed with a second radiologist reading select images from the participants.

Results: Forty-eight people were recruited, 24 with gout and 24 controls. The mean age was 61.9 years with 22 (92 percent) being male. Participants with tophaceous gout had longstanding disease with mean serum urate level of 0.37 mmol/l. Intratendinous tophus was seen in 35/48 (72.9 percent) tendons of patients with gout. There was no tophus deposition, 0/48, in the Achilles tendons of the control group. There was a higher number of tendon tears, calcaneal bone cortex irregularities and calcaneal enthesophytes in the gout participants, but there was no significant difference. In reference to the zones, the only significant ultrasound characteristic was intratendinous hyperechoic spots, defined as formation of collagen fibril or calcified tophi, seen more frequently at the insertion.

Conclusions: There are many causes for Achilles tendon pathology with one being gout. Ultrasound can be used in the office to assess Achilles tendon pain in patients who have a history of gout. This article found that even in the presence of high tophus formation, the structural integrity of the Achilles tendon remains largely intact. However, there were more ultrasound characteristics, such as inflammation and calcaneal irregularities, for participants with gout. These findings may aid the foot and ankle surgeon in diagnosing gout as an underlying etiology of Achilles tendon pathology. The limitations to this study included scoring features that are not standardized or validated, which might have influenced the results. Gout should remain in the differential diagnosis when presented with Achilles tendon pathology. 

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