The ankle 1: inversion injury including lateral ligaments
A 19-year-old woman presented having suffered an injury to her left ankle. Two-weeks earlier she had tripped on a medicine ball and forcefully inverted her ankle. An X-ray at ED taken on the day of the injury did not show a fracture, and she was advised to use RICE and given elbow crutches. Ultrasound examination (Philips iU22, L12-5 MHz and 15-7 MHz Hockey Stick transducers) of the lateral, medial, anterior and posterior compartments of her left ankle was performed.
The examination demonstrated an anterior talofibular ligament (ATFL) partial tear Grade 2 injury, superior extensor retinaculum tear, talocrural joint capsule injury, and deltoid ligament sprain and vascularity.
Key findings (Figures below) included thickening of the ATFL with a partial tear (7 x 4 mm) and mild thickening of the lateral aspect of the superior retinaculum. The posterior talofibular ligament (PTFL) appeared normal, however there was fluid bulging over the posterior talofibular ligament (11 x 5 x 4 mm) in the region of the lateral part of the posterior talocrural joint, which was focally tender. In addition the deltoid ligament was mildly disrupted, tender, and had increased vascularity. All other structures examined, including the calcaneofibular ligament (CFL), were normal.
Figure A: The thickened ATFL in long view, with hashmarks indicating the size of the tear.
Figure B: The thickened ATFL in axial view, with hashmarks indicating the size of the tear.
Figure C: The thickened extensor retinaculum, indicated by hashmarks, wrapping around the lateral part of the EDL tendon bundle.
Figure E: The disrupted deltoid ligament, with vascularity indicated in red.
Figure D: The fluid in the region of the posterior talocrural joint.
Figure F: The disrupted deltoid ligament.
Conventional wisdom has it that the most commonly injured aspect of the ankle is the lateral ankle ligament complex1 (comprised of the ATFL, CFL and PTFL), particularly in athletic populations2. Indeed, the presentation of this case suggested that a lateral ligament injury was likely, and reassuringly an ATFL tear was found. How could we interpret the rest of the findings?
In fact, few inversion injuries damage the lateral ankle complex in isolation, for example up to 50% of inversion injuries also injure the deltoid ligament3. In this case, the findings do suggest deltoid ligament injury. In addition, you may recall that the deep layer of the deltoid ligament comprises a portion of the ankle (talocrural) joint capsule4. When considered alongside the posterior fluid bulge that was found, it is not unreasonable to consider the possibility of joint capsule injury as part of the clinical picture.
Finally, a swollen superior extensor retinaculum may be compressing the extensor digitorum longus (EDL) tendon bundle, and this in turn may lead to stenosing tenosynovitis. We think this case highlights that an inversion ankle injury includes involvement of the lateral complex but is less likely to be limited to only the lateral complex.
References:
MacAuley D. Ankle injuries: same joint, different sports. Med Sci Sports Exerc. 1999 Jul;31(7 Suppl):S409-11.
Roos KG, Kerr ZY, Mauntel TC, Djoko A, Dompier TP, Wikstrom EA. The Epidemiology of Lateral Ligament Complex Ankle Sprains in National CollegiateAthletic Association Sports. Am J Sports Med. 2017 Jan;45(1):201–9.
Khor YP, Tan KJ. The Anatomic Pattern of Injuries in Acute Inversion Ankle Sprains: A MagneticResonance Imaging Study. Orthop J Sport Med. 2013 Dec;1(7):2325967113517078.
Amaha K, Nimura A, Yamaguchi R, Kampan N, Tasaki A, Yamaguchi K, et al. Anatomic study of the medial side of the ankle base on the joint capsule: analternative description of the deltoid and spring ligament. J Exp Orthop. 2019 Jan;6(1):2.