SLR - October 2017 - Elizabeth P. Parry
Ratio of Range of Motion of the Ankle and Surrounding Joints After Total Ankle Replacement
Reference: Dekker TJ, Hamid KS, Easley ME, DeOrio JK, Nunley JA, Adams SB. Ratio of Range of Motion of the Ankle and Surrounding Joints After Total Ankle Replacement. J Bone Joint Surg Am. 2017 Apr 5; 99(7):576–582.
Scientific Literature Review
Reviewed By: Elizabeth P. Parry, DPM
Residency Program: The Western Pennsylvania Hospital
Podiatric Relevance: Arthrodesis is considered to be the gold standard for end-stage ankle arthritis. However, increased compensatory motion at the surrounding joints can increase the rate of degenerative arthritis. With the advent of total ankle replacements, it is theorized that the preserved physiologic ankle range of motion decreases the rate of degenerative changes at adjacent joints. Although total ankle replacements do not completely restore normal gait, they offer some preservation of normal range of motion in comparison to ankle arthrodesis. This retrospective study looked at 197 patients who had undergone a total ankle replacement to compare fixed bearing and mobile bearing for actual ankle joint range of motion through the prosthesis compared to total arc of ankle motion and the contribution of adjacent joint and midfoot motion to the total arc of the ankle.
Methods: A level IV retrospective study was performed for 197 patients who underwent a total ankle replacement (75 INBONE, 52 Salto-Harris, and 70 STAR prostheses). All patients had lateral standardized weightbearing radiographs at maximum dorsiflexion and plantarflexion taken at one year postoperatively, with a minimum follow-up of two years. Sagittal plane measurements were performed to compare the total motion arc to the actual ankle motion through the prosthesis. Secondary measurements were taken of the talonavicular joint motion, subtalar joint motion and midfoot range of motion to assess the degree of peritalar joint motion that contributed to total ankle joint range of motion.
Results: The mean actual ankle joint motion through the prosthesis was 25.9° +/- 12.2°, with the mean total motion arc of ankle 37.6° +/- 12.0°. This was statistically significant. This demonstrates that the ankle accounted for 68 percent of total range of motion, and the motion of the peritalar joints accounted for 32 percent. When comparing the degree of motion between the three types of prostheses and the fixed and mobile joint bearing designs, no statistically significant difference was noted.
Conclusion: Actual ankle motion after total ankle replacement is 12° less than the total arc of motion. This might be because of increased compensatory midfoot and subtalar joint motion.