Triple Arthrodesis with Concomitant Tendo-Achilles Lengthening in Stage III Adult Acquired Flatfoot - A Retrospective Study of Prospectively Collected Clinical and Radiological Outcomes at Two Years.

Introduction: Triple Arthrodesis is the preferred surgical treatment of stage III Adult Acquired Flatfoot Deformity. However, studies have reported subsequent midfoot degenerative arthrosis, with medial column instability. Material and Methods: This is a retrospective study using prospectively collected registry data from a single tertiary institution. Between 2007 to 2014, all patients who had undergone Triple Arthrodesis with concomitant percutaneous Tendo-Achilles lengthening were included. Patients with previous foot surgery, revision surgeries, and concomitant surgical procedures were excluded. We aim to report on our two years outcomes using the hindfoot and midfoot AOFAS and VAS scores, as well as radiographic parameters such as first-metatarsal declination angle, medial cuneiform calcaneal angle, navicular height, medial cuneiform - first metatarsal cuneiform angle, calcaneal pitch and medial longitudinal arch. Results: There were 22 feet from 21 patients that met the criteria of having undergone Triple Arthrodesis with concomitant percutaneous Tendo-Achilles lengthening. Hindfoot and midfoot American Orthopaedic Foot and Ankle Society (AOFAS) scores improved by an average of 34.6 and 36.7 points at 24-months post-surgery (p<0.001). Between six months to two years post-operatively, there was evidence of mid-foot sagging as shown with an increase in Calcaneal-First metatarsal angle by a mean of 5.1° (p=0.001). Additionally, a decrease in the Calcaneal Pitch Angle by 2.9° (p=0.003) and Cuneiform-Calcaneal angle by 5.5° (p=0.000). Navicular Height also decreased significantly by 2.8mm (p=0.001) over this period. A total of 18 (85.6%) reported overall satisfaction being met at the time of a phone survey, at an average of 8.3 years (range 5.8 to 12.4) post-surgery. One patient required an ankle replacement, and another had removal of hardware done. Conclusion: Triple arthrodesis with concomitant Tendo-Achilles lengthening results in significant improvement in AOFAS mid-foot and hindfoot scores at two years. At two years mark, there was features of mid-foot sagging postoperatively, despite continued improvement in AOFAS scores. Eighteen of the 21 patients were satisfied with the outcomes, on a phone survey, at an average of 8.3 years post-surgery.