Hounsfield Unit Assessed Bone Density Amongst Non-Traumatic and Post-Traumatic Arthritic Total Ankle Arthroplasty Patients

CATEGORY: Ankle Arthritis; Ankle; Hindfoot; Trauma INTRODUCTION/PURPOSE: The etiology of ankle arthritis is multifactorial and secondary osseous changes to the tibiotalar joint can be variable. The relationship of bone density within the tibia and talus with respect to type of ankle arthritis is not well understood. Improved insight of osseous characteristics amongst ankle arthritis patients is helpful in determining optimal implant selection for total ankle arthroplasty. The purpose of this study is to retrospectively analyze pre-operative total ankle arthroplasty patients' films for osseous characteristics associated traumatic ankle arthritis compared to other forms of arthritis using computed tomography (CT) generated Hounsfield units (HU) to analyze bone mineral density and rate of cyst formation. METHODS: A retrospective analysis was performed of 440 patients, under a single orthopedic practice, who underwent primary TAA between 2013-2019. Pre-operative HU of tibia and talus were analyzed amongst two groups (Non-traumatic OA, Post- traumatic OA) within one year prior to TAA. RESULTS: Forty-nine qualified patients (23 NTA, 26 PTA) with mean follow-up in months of 19.98 (SD 15.22) were analyzed. Cystic changes at level of TAA cuts or retained bone: 5 tibia (10.2%), 7 talus (14.29%), 16 combined (32.65%). Overall tibial HU mean 270.23 (SD 91.28) and talus 463.26 (103.65). HU of the tibia amongst post-traumatic and non-traumatic patients was 257.21 (SD 93.9) and 284.94 (SD 87.9) (p=0.29137) and talus 434.53 (104.7) and 495.75 (94.33) (p=0.0365). CONCLUSION: Our results suggest with tibiotalar arthritis HU is a useful tool to predict bone quality. Clinical results amongst the NTA and PTA groups was comparable. Significantly lower HU values were recorded for the PTA groups. Rate of cystic formation within bone of distal tibia does not necessarily correlate with overall HU measured bone mineral density.