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Role of Regional Bone Mineral Density on Ankle Fracture Pattern Hannah Sahli, DPMb, Cody J. Togher, DPMa, Stephanie L. Golding, DPMa, Jordan Butterfield, DPMa, Joshua A. Sebag, DPMb, Christopher L. Reeves, MS, DPM, FACFASc, Amber M. Shane, DPM, FACFASc

aCurrent Resident, AdventHealth East Orlando, Florida bImmediate Past Resident, AdventHealth East Orlando, Florida cAttending Faculty, Department of Podiatric Surgery, AdventHealth East Orlando Residency, Florida

Introduction & Literature Review Results Discussion Ankle fractures are a common injury treated by foot and ankle surgeons, frequently Of the 108 subjects, 39 were male, 69 were female. Average age was Rotational mechanism of injury has been described with the Lauge-Hansen classified on plain film radiographs using the Lauge-Hansen system (1). In each stage, 50.7 years. Average BMI was 30.9 ± 32 kg/m^2; tobacco use in 26 system. Injury pattern includes malleolar or ligamentous injury. We investigated malleolar fracture or ligamentous rupture is sustained. However, it is unclear what factors (24.1%), and diabetes mellitus in 18 (16.7%) patients. Average BMD a correlation between BMD and fracture severity. account for this difference. We suspect bone mineral density (BMD) is a contributing The influence CTs have on surgical treatment of ankle fractures has been factor. was 233.18 ± 233 HU. When divided by malleolar involvement there Decreased BMD is a known risk factor for fragility fractures, often hip, wrist and spine were 8 unimalleolar, 33 bimalleolar, and 67 trimalleolar fractures. The discussed by numerous authors (5,6). We had more trimalleolar versus fractures in the elderly (2). The correlation between BMD and ankle fractures has not majority of fractures were supination-external rotation injuries (n=60). unimalleolar fractures, likely because CT images were obtained for surgical planning (7). been well documented. To measure BMD, dual x-ray absorptiometry (DXA) is considered There was an inverse relationship between BMD and malleolar the gold standard but is expensive and time-consuming. Using pre-operative computed We believe that fracture classification is based on mechanism and incidence of tomography (CT), however, we can assess BMD in Hounsfield units (HU) (3). Warner et al involvement (p = 0.04) for unimalleolar (mean 264 HU), bimalleolar injury while the presence of malleolar versus ligamentous injury is strongly showed that HU from the injured versus contralateral extremity had nearly perfect (mean 251 HU), and trimalleolar (mean 220 HU) fractures. An inverse influenced by regional BMD. Hey et al found that in femoral neck fractures, the agreement, supporting this method to accurately measure BMD for fractures. They also relationship was found between age and regional BMD (p<0.001). No fracture traversed areas with lowest BMD, suggesting a higher proclivity for found mean HU on the injured extremity significantly correlated with lumbar, hip and total relationship was found between tobacco use and BMD (p=0.94) or fracture in those regions (8). BMD based on DXA within 3 months of injury (4). The purpose of this study was to between BMD and Lauge-Hansen classification (p = 0.13). determine BMD as a contributing factor in the number of fractured malleolus in adult While CT is not an alternative to DXA in evaluation of global BMD, CT should be ankle fractures. used to evaluate regional BMD preoperatively. This can provide insight to bone quality before reaching the operating room. In multiple studies, locking plate fixation for fibular fractures has increased fixation strength in osteoporotic bone Methodology compared with nonlocking fixation (9,10,11). Tingart et al found that pullout strength of cancellous screws in the humeral head was significantly lower in 108 patients with operatively repaired ankle fractures from July 2017 to August 2019 were identified. Inclusion criteria included: 1) age > 18, 2) pre-operative CT available areas of decreased BMD (12). This can help reduce, or justify, the cost of and 3) underwent open reduction internal fixation (ORIF). Exclusion criteria were: 1) internal fixation based on BMD. no pre-operative CT, 2) chronic injuries, 3) revisional ORIF, 4) and open injuries. There are inherent limitations with retrospective analyses. This cohort of Retrospective chart review was performed to collect age, sex, past medical history, patients may not be representative of populations in other centers or areas, smoking history, characteristics of fracture pattern, and regional bone density. which may limit generalizability of results. There is possible interrater variability Preoperative radiographs and CT were reviewed. Fractures were classified via the in BMD measurements. Lauge-Hansen system. CTs were performed using a 64-slice scanner with 1.25mm In conclusion, our results show a significant correlation between decreased slices. HU were calculated using a Picture Arching and Communication System BMD and number of malleolar fractures. This supports the suspicion that (PACS) with values of cancellous bone in the tibia and fibula. A “region of interest” decreased BMD plays a role in the occurrence of malleolus versus ligamentous (ROI) was placed in the metaphyseal region approximately 1cm proximal to the tibial injury. CT is routinely ordered for surgical planning of complex fractures but can plafond on axial image, avoiding the physeal scar. The same technique was also be used to assess BMD. This can be used for fixation considerations, performed in the fibula at the plafond level. HU values from three consecutive axial perioperative risks, and systemic treatment to optimize bone metabolism. slices of the distal tibia and fibula were averaged for each bone, and then for each Figure 1: Results of bone mineral density analysis with corresponding p-values. ankle. Using a generalized linear model, the association between BMD, number of References fractured malleoli, and Lauge-Hansen fracture pattern was ascertained to achieve a 1.Lauge-Hansen N. Fractures of the ankle: II. Combined experimental-surgical and experimental-roentgenologic investigations. p value. Secondary objectives included the correlation between age and BMD Arch Surg. 1950;60:957–985. (Spearman correlation) and BMD and current tobacco use (Mann-Whitney test). 2.Unnanuntana A, Gladnick BP, Donnelly E, Lane JM (2010) The assessment of fracture risk. J Bone Jt Surg Am 92:743–753. https ://doi.org/10.2106/JBJS.I.00919. 3.Schreiber, J. J., Anderson, P. A., & Hsu, W. K. (2014). Use of computed tomography for assessing bone mineral density. Neurosurgical focus, 37(1), E4. 4.Warner, S. J., Garner, M. R., Fabricant, P. D., & Lorich, D. G. (2018). Bone density correlates with clinical outcomes after ankle fracture fixation. 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A contoured locking plate for line or the cortical Figure 3: Age correlation with bone mineral density measured in Hounsfield distal fibular fractures in osteoporotic bone: a biomechanical cadaver study. Injury 43:718–725, 2012 margin. 11.Davis AT, Israel H, Cannada LK, Bledsoe JG. A biomechanical comparison of one- third tubular plates versus periarticular Units. Shows a significant relationship between increasing age and decreasing plates for fixation of osteoporotic distal fibula fractures. J Orthop Trauma 27:e201–e207, 2013 BMD. 12.Tingart MJ, Lehtinen J, Zurakowski D et al (2006) Proximal humeral fractures: regional differences in bone mineral density of the humeral head affect the fixation strength of cancellous screws. J Shoulder Elbow Surg 15:620–624. https://doi.org/10.1016/j. Jse.2005.09.007 Financial Disclosures: N/A