Purpose: To report the MRI features of ECU accessory tendinous
slips, assess their observable prevalence and evaluate a potential link
between this anatomical variation and ECU tenosynovitis or
tendinopathy.
Methods and materials: Institutional review board approved this
retrospective study, with waiver of patient informed consent. One
hundred sixty wrist MRI studies from 158 patients (85 females, 73
males, mean age 45.6 years, range 14-86) performed between March
2008 and February 2009 on a 1.5-T unit were included. MR images
were analyzed by two radiologists in consensus. The observable
prevalence of ECU accessory tendinous slips was assessed and
their origin, diameter and insertion sites were noted. The presence
of ECU tenosynovitis and/or tendinopathy was also evaluated.
Results: The observable prevalence of ECU accessory tendinous slips
was 21.9% (35/160). The origin was always seen: 8 were at the level of,
and 27 distal to the ECU subsheath. The slip median diameter was 0.67
mm (range 0.43-0.88). The insertion was seen in 17.1% (6/35): 2 were
on the fifth metacarpal bone, 4 on the extensor apparatus of the fifth
finger. ECU tenosynovitis (20%), tendinopathy (5.7%) as well as
concomitant tenosynovitis and tendinopathy (25.7%) were more
frequently encountered in the patients with the anatomical variation
than in the control patients group (0.8%, 3.2% and 9.6% respectively).
Differences were statistically significant for tenosynovitis (p = 0.0001)
and concomitant tenosynovitis and tendinopathy (p = 0.02) of the ECU.
Conclusion: ECU accessory tendinous slips are frequent and visible
on 1.5-T wrist MRI studies. ECU tenosynovitis and tendinopathy are
more frequent in patients bearing this anatomical variation.