Lateral Ankle Instability: The Predictive Value of Ankle Stress Radiographs vs MRI

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Eunice Townsend
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1 Lateral Ankle Instability: The Predictive Value of Ankle Stress Radiographs vs MRI Natalie R. Danna, MD Rachel J. Shakked, MD Steven C. Sheskier, MD

2 Lateral Ankle Instability: The Predictive Value of DISCLOSURES The authors have no conflicts to disclose. 2

functional instability) may have limited rehabilitation potential with nonoperative treatment Reliable

3 BACKGROUND Chronic lateral ankle instability in 20% of sprained ankles Sequelae of instability: synovitis, osteochondral lesions, chondromalacia, loose bodies, ankle arthritis Mechanical instability (vs. functional instability) may have limited rehabilitation potential with nonoperative treatment Reliable identification of pts w/ mechanical instability is important in directing effective treatment Image courtesy of Dr. Ken Mroczek 3

4 BACKGROUND Making the diagnosis: o History: recurrent sprains, ankle giving out o Physical exam: + anterior drawer test; + inversion stress test o Stress radiography: increase in talar tilt and anterior drawer distance o MRI: torn or attenuated ligaments o Arthroscopy: visualized instability However, a standardized diagnostic algorithm is not well-established. PURPOSE To assess the utility of stress radiography & MRI to objectively diagnose mechanical ankle instability. 4

5 METHODS Retrospective chart review on all pts w/ Telos (Hungen, Germany) stress radiographs January 2008 August 2013 Talar tilt & anterior drawer distance measured for each stress radiograph MRI reports reviewed for lateral ligament quality Operative reports reviewed for ankle stability 103 pts w/ subjective instability 38 patients (37%) taken to OR 54 males 49 females Avg age: 40 y 20 (53%) w/ intra-op instability requiring lateral ligament repair 30 (79%) w/ pre-op MRI 5

association b/t ligament tear & talar tilt 6 degrees

6 RESULTS 30 pts w/ pre-op MRI taken to OR As talar tilt ê, ligaments less likely to be torn Significant association b/t ligament tear & talar tilt 6 degrees (p < 0.01) é talar tilt compared to contralateral side! 6

ligaments all classified as abnormal ) ATFL appearance

7 RESULTS Stratification by radiologic description of MRI findings ( attenuated, thickened, or torn ligaments all classified as abnormal ) ATFL appearance on MRI did not correlate w/ intraoperative stability (p = 0.31) 7

8 RESULTS Talar Tilt Measurements for Ankles Found to be Stable and Unstable at the Time of Surgery Talar Tilt (degrees) Ligament Appearance on MRI Abnormal Intact Unavailable 5 0 Stable Unstable 8

9 Stress XR Predicts Instability If intra-op stability considered gold standard, talar tilt of 6 on stress XR significantly predicted ligament incompetence (p < 0.01). Sensitivity & Specificity Sensitivity of stress XR to identify ligament incompetence was 90%. Specificity = 61% MRI Not Predictive of Instability MRI reports described lateral ligaments as intact, thickened, attenuated, or torn. No correlation b/t radiologist s description of ATFL on MRI & intraoperative stability (p = 0.31). 9

10 CONCLUSIONS Stress XR predicts intra-op ligament incompetence when talar tilt 6. No correlation b/t MRI findings & intra-op stability. The dynamic nature of stress radiographs may be better suited to diagnosing mechanical instability than a static MRI. Physical exam remains important in work-up of ankle instability, but stress radiography may be a more objective tool. 10

o Does PT fail to resolve instability in mechanical group?

11 FUTURE DIRECTIONS Use stress XR to stratify patients into functional v. mechanical instability o Does PT resolve instability in functional group? o Does PT fail to resolve instability in mechanical group? Evaluate relationship b/t cartilage injury and degree of instability Further evaluate subgroup of patients w/ isolated CFL injury Cadaver Dissection of Lateral Ligaments! Subtalar Instability w/ Isolated CFL Transection! ATFL! CFL transected! ATFL! CFL! CFL! 11

12 REFERENCES 1. Ajis A, Maffulli N. Conservative management of chronic ankle instability. Foot Ankle Clin 006;11: Alparslan L, Chiodo CP. Lateral ankle instability: MR imaging of associated injuries and surgical treatment procedures. Semin Musculoskelet Radiol Dec;12(4): Chan KW, Ding BC, Mroczek KJ. Acute and chronic lateral ankle instability in the athlete. Bull NYU Hosp Jt Dis. 2011;69(1): Karlsson J, Lansinger O. Lateral instability of the ankle joint (1). Non-surgical treatment is the first choice 20 percent may need ligament surgery. Lakartidningen 1991;88(15): Karlsson J, Lansinger O, Faxen E. Lateral instability of the ankle joint (2). Active training programs can prevent surgery. Lakartidningen 1991;88(15): Ferran NA, Maffulli N. Epidemiology of sprains of the lateral ankle ligament complex. Foot Ankle Clin 2006;11: Griffith JF, Brockwell J. Diagnosis and imaging of ankle instability. Foot Ankle Clin 2006;11: Komenda GA, Ferkel RD. Arthroscopic findings associated with the unstable ankle. Foot Ankle Int 1999;20: Tohyama H, Yasuda K, Ohkoshi Y, et al. Anterior drawer test for acute anterior talofibular ligament injuries of the ankle. How much load should be applied during the test? Am J Sports Med 2003;31(2): Wang CS, Tzeng YH, Lin CC, Huang CK, Chang MC, Chiang CC. Radiographic Evaluation of Ankle Joint Stability After Calcaneofibular Ligament Elevation During Open Reduction and Internal Fixation of Calcaneus Fracture. Foot Ankle Int May

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