1. Ankle fractures have features of an osteoporotic fracture Kyoung Min Lee MD Department of Orthopaedic Surgery Seoul National University Bundang Hospital

2. Disclosures The authors have no disclosures.

3. Introduction Osteoporosis is a serious disease with high morbidity and mortality caused by fragility fractures, especially hip and spine fractures Osteoporotic fracture is a special treatment problem that needs special care and instruments in operative treatment - poor fixation stability, more comminution?

4. Introduction What is osteoporotic fracture? - fracture on osteoporotic bone Osteoporosis - loss of bone mineral density - age, gender dependent (hormone)

5. Introduction Is ankle fracture an osteoporotic fracture? - increasing incidence after menopause - and ?? Thur et al. 2012

6. Purpose Investigate osteoporotic features of ankle fractures in terms of (1) bone attenuation on CT (BMD) (2) degree of trauma between the ages over 50 years and less than 50 years in patients with ankle fractures.

7. Materials and Methods Retrospectively reviewed 194 consecutive patients with ankle fractures CT examination Exclusion : 30 patients - previous Op - congenital malformation - neuromuscular diseases - tumors or infections - interval of more than one week between the injury and CT examination

8. Demographic data - age, gender Mechanism of injury - high/low energy trauma Fracture type - medial malleolar, lateral malleolar, bimalleolar, trimalleolar Bone attenuation on CT - ROI tool - talus, DT, LM, MM Materials and Methods

9. Bone attenuation (housefield unit, ROI)

12. Data analysis Reliability of CT measurement - ICC Comparison between younger ( 50 yrs) - t-test - chi-square test Multiple regression analysis - effect of age and gender on bone attenuation

13. Results

14. Table 1. Data summary Number of patients194 Mean age (years)51.0 (SD 15.8) Male : Female, n (%)98 (50.5) : 96 (49.5) Right : Left, n (%)109 (56.2) : 85 (43.8) Low energy trauma : high energy trauma, n (%)167 (86.1) : 27 (13.9) Fracture type (medial malleolar/lateral malleolar/bimalleolar/trimalleolar) 23/76/58/37 Average bone attenuation on CT talus (HU)350.7 (SD 97.3) medial malleolus (HU)293.1 (SD 101.0) lateral malleolus (HU)234.5 (SD 93.5) distal central tibia (HU)184.5 (SD 77.6) SD, standard deviation; HU, housefield units.

15. Table 2. ICC values of inter- and intraobserver reliabilities of bone attenuation measurements TalusMedial malleolusLateral malleolusDistal central tibia Interobserver0.988 (0.970 to 0.995)0.888 (0.739 to 0.954)0.895 (0.756 to 0.957)0.875 (0.712 to 0.949) Intraobserver0.983 (0.958 to 0.993)0.981 (0.953 to 0.992)0.986 (0.964 to 0.994)0.943 (0.846 to 0.978) Data are presented as ICC (95% confidence interval)

16. Table 3. Comparison between the younger and older age groups in male patients Younger age groupOlder age groupp-value Number of patients5345- Mean age (years)35.8 (SD 8.9)64.3 (9.3)<0.001 Low energy trauma : high energy trauma, n (%)40 (75.5) : 13 (24.5)40 (88.9) : 5 (11.1)0.087 Fracture type (medial malleolar/lateral malleolar/bimalleolar/trimalleolar)7/27/14/58/12/10/150.012 Average bone attenuation on CT talus (HU)392.7 (SD 85.1)346.2 (SD 82.5)0.008 medial malleolus (HU)338.1 (SD 104.6)296.4 (SD 86.1)0.036 lateral malleolus (HU)297.5 (SD 89.4)233.7 (SD 69.1)<0.001 distal central tibia (HU)225.5 (SD 85.9)175.3 (SD 62.7)0.002 SD, standard deviation; HU, housefield units.

17. Table 4. Comparison between the younger and older age groups in female patients Younger age groupOlder age groupp-value Number of patients3561- Mean age (years)36.9 (SD 8.1)62.4 (SD7.1)<0.001 Low energy trauma : high energy trauma, n (%)28 (80) : 7 (20)59 (96.7) : 2 (3.3)0.011* Fracture type (medial malleolar/lateral malleolar/bimalleolar/trimalleolar)7/14/8/61/23/26/110.009 Average bone attenuation on CT talus (HU)395.8 (SD 98.5)291.7 (SD 85.9)<0.001 medial malleolus (HU)321.2 (SD 86.0)235.4 (SD 89.8)<0.001 lateral malleolus (HU)245.6 (SD 86.8)174.1 (SD78.6)<0.001 distal central tibia (HU)216.0 (SD 55.3)137.7 (SD 63.4)<0.001 SD, standard deviation; HU, housefield units; *, Fisher exact test.

18. Table 5. Effects of age and gender on bone attenuation in multiple regression analysis Dependent variable (bone attenuation)Independent variableBeta95% CIp-value Talus Age-2.4-3.2 to -1.6<0.001 Gender-31.3-56.3 to -6.30.014 Constant52.1.7469.1 to 574.4<0.001 Medial malleolus Age-2.5-3.3 to -1.7<0.001 Gender-41.8-67.4 to -16.10.002 Constant482.5428.4 to 536.6<0.001 Lateral malleolus Age-2.6-3.3 to -1.9<0.001 Gender-57.0-79.2 to -34.9<0.001 Constant451.6405.0 to 498.3<0.001 Dista central tibia Age-2.3-2.9 to -1.7<0.001 Gender-26.4-45.3 to -7.40.007 Constant342.5302.5 to 382.4<0.001 CI, confidence interval. In multiple regression analysis, dependent variable is bone attenuation (a surrogate marker of bone mineral density) of each bony structure, and independent variables are age and gender. Age and female gender show negative effect on bone attenuation.

20. Conclusions - Ankle fracture had features of osteoporotic fracture that is characterized by age and gender dependent low bone attenuation. Ankle fracture should not be excluded from the clinical and research interest as well as from the benefit of osteoporosis management. This study has been accepted in Osteoporos Int (IF=4.8)

21. Thank you!