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Category: Ankle; Ankle Arthritis Introduction/Purpose: Outcomes following total ankle arthroplasty (TAA) are largely positive, with high levels of patient satisfaction, but residual pain has been identified in up to 60% of cases. While associations between implant kinematics and pain following TAA have been found in a study of walking gait, there have been no studies to date of pain and function during more challenging locomotor tasks. The purposes of this study were (1) to examine pre- to post-operative (6 months) changes in function along with comparisons to healthy controls, and (2) to determine how functional changes are related to pain. We hypothesized that following TAA, function would improve but would not match that of healthy controls. We further hypothesized that improvements in function would be related to reductions in pain. Methods: Complete data sets were obtained for 11 TAA patients (age: 64.04 +- 9.26 y, height: 1.71 +- 0.07 m, body mass: 98.55+- 20.07 kg; 3 implant designs) and 15 age-matched control subjects (age: 63.14 +- 7.95 y, height: 1.68 +- 0.10 m, body mass: 75.57+- 13.66 kg). All procedures involving testing of human subjects were approved by the PSU HMC Institutional Review Board. Patients performed all tasks pre-operatively and six months post-operatively in a motion laboratory. Participants completed the RAND 36-Item Health Survey 1.0 (SF-36), whose global pain score was used in our analysis. Each patient and control participant performed three tasks to assess their locomotor function: Single-Leg Balance Test (SLBT); Timed Up-and-Go (TUG) Test, and Six- Minute Walk (6MW). Linear regression analysis incorporating covariates of change in pain (delta-pain) and BMI was performed to investigate how change in performance on these tests depended on these variables. Results: For 6MW velocity (r = 0.653, p = 0.030), normalized 6MW velocity (r = 0.624, p = 0.040), and SLBT (r = 0.695, p = 0.018) pre-operative scores were correlated with post-operative function. TUG performance had a very weak correlation (r = 0.226, p = 0.504) and pain levels had a moderate correlation (r = 0.646, p = 0.032). Linear regression did not predict change in function from delta-pain alone, but when BMI and the interaction of BMI with delta-pain were included, moderate to good fits for change in function were obtained (Table 1). Improvements in pain (when accounting for BMI) accounted for the majority of improvement in average walking velocity, and up to half of the variation in improvement in TUG. Conclusion: This is the first study relating changes in locomotor function to changes in pain following TAA. Our first hypothesis that performance on the three tests would be improved over pre-operative function, but without reaching that of healthy controls, was supported. Contrary to our second hypothesis, we found that pain improvement assessed using the pain score from the SF-36 did not explain variation in observed improvements in function. When we included the interaction between pain and BMI in our models, 80% of the changes in 6MW average velocity was explained, and approximately 50% of TUG time change was explained. [Table: see text]

Prior research on total ankle arthroplasty (TAA) has focused on improvements in pain and function following the surgical treatment of ankle arthritis, but its effect on ankle joint mechanics has received relatively little attention. The plantarflexion moment arm of the Achilles tendon is a critical determinant of ankle function with the potential to be altered by TAA. Here we investigate the effect of TAA on Achilles tendon moment arm assessed using two methods. Standing sagittal‐plane radiographs were obtained for ten patients presurgery and postsurgery, from which anterior–posterior distance between the posterior calcaneus and the center of the talar dome was measured. Ultrasound imaging and three‐dimensional (3D) motion capture were used to obtain moment arm pre‐ and post‐TAA. The absolute changes in moment arm pre‐ to post‐TAA were significantly different from zero for both methods (9.6 mm from ultrasound and 4.6% of the calcaneus length from radiographs). Only 46% of the variance in postoperative 3D Achilles tendon moment arm was explained by the preoperative value (r2 = 0.460; p = .031), while pre‐ and post‐TAA values from radiographs were not correlated (r2 = 0.192, p = .206). While we did not find significant mean differences in Achilles tendon moment arm between pre‐ and post‐TAA, we did find absolute changes in 3D moment arm that were significantly different from zero and these changes were partially explained by a change in location of the talar dome as indicated by measurements from radiographs (r2 = 0.497, p = .023).

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