Functional Outcomes and Deformity Correction of Double vs Triple Arthrodesis in Stage III Posterior Tibial Tendon Insufficiency. A Prospective Cohort Study

CATEGORY: Hindfoot INTRODUCTION/PURPOSE: Posterior tibial tendon insufficiency (PTTI) remains the most important contributor to AAFD. When the deformity becomes rigid, management options are limited to arthrodesis. Triple arthrodesis is considered the gold standard for treating painful, rigid flatfoot deformities with proven long-term reliability of correction and favorable functional outcomes. However, the necessity of fusing an unaffected calcaneocuboid joint has been questioned, and double arthrodesis has been suggested as an alternative to triple arthrodesis. The double arthrodesis has been proven to restore function, provide a plantigrade foot, and protect against postoperative ankle valgus. This study aims to prospectively compare double and triple arthrodesis in terms of functional outcomes and deformity correction. To the best of our knowledge, this is the first prospective comparative study in the literature to date. METHODS: This is a prospective comparative cohort study carried out between May 2017 and May 2019. The study was approved by the IRB at Assiut University and done according to the Helsinki declaration. Patients with AAFD stage III aged between 15 and 40 years old were assigned to double arthrodesis or triple arthrodesis. The groups were prospectively followed for one year. Primary outcomes were union rates, AOFAS scores, and radiological parameters of deformity correction plain radiographs. Secondary outcomes were operative time, time to union, and complications. Twenty-three patients matched the inclusion criteria. Thirteen (all males) patients underwent double arthrodesis, while ten (nine males and one female) patients underwent triple arthrodesis. The mean age for double and triple arthrodesis was 20.15+-5.63 and 25.10+-8.36 years, respectively, and the mean follow-up lengths were 12.46 and 12.9 months, respectively, with no statistically significant differences in age, follow-up or gender between both groups. RESULTS: All patients in both groups achieved union by four months. The mean time to union in the double and triple arthrodesis groups was 3.39+-0.65 vs. 3.31 +-0.6 months, respectively, with no statistically significant differences (P=0.77). The mean operative time in the double arthrodesis group than the triple arthrodesis group, 55.77+-15.18 vs. 91.6+-24.14 minutes (P<0.001), respectively. Both double and triple arthrodesis groups had a statistically significant improvement of the mean AOFAS hindfoot score postoperatively (71.46 +-7.77 vs. 88.38 +-3.66, P<0.001) and (66.9 +-7.69 vs. 85 +-5.83, P<0.001), respectively. Both double and triple arthrodesis groups had statistically significant improvement of preoperative Meary’s angle, calcaneal pitch, Cal-MT5 height, calc-MT1 angle, and TN coverage angle postoperatively. There were no statistically significant differences between double vs. triple arthrodesis groups in AOFAS score improvement or the magnitude of deformity correction. CONCLUSION: Double arthrodesis is an equally reliable surgical option for AAFD stage III for achieving union, improving the functional outcomes, and deformity correction as triple arthrodesis with a significantly shorter operative time in the former. The authors recommend double arthrodesis if the calcaneocuboid joint is unaffected.