Clinical and Radiographic Results of Ankle Joint Preservation Surgery in Posterior Ankle Arthritis

Background: Little information is available about how to manage ankles with eccentric arthritis in the sagittal plane. This study aimed to report clinical and radiographic outcomes following joint preservation surgery for ankles with eccentric arthritis at the posterior tibiotalar joint and a plantarflexed talus in the sagittal plane, which we named posterior ankle arthritis. Methods: Ten ankles with posterior ankle arthritis were treated with realignment surgery between 2017 and 2018. Posterior ankle arthritis was defined as having both (1) eccentric narrowing of the joint space at the posterior aspect of the tibiotalar joint on weightbearing lateral radiographs and (2) coronal talar tilt angle less than 4 degrees on weightbearing anteroposterior radiographs. Flatfoot reconstruction with a hindfoot arthrodesis procedure was performed in all patients (subtalar arthrodesis, n = 9; triple arthrodesis, n = 1), and a supramalleolar osteotomy was added in patients with varus distal tibial alignment (n = 6). Pain, functional outcome (foot function index [FFI]), radiographic arthritis stage (stage I to IV), and 9 radiographic parameters, including lateral talar center migration (LTCM), were evaluated on pre- and postoperative weightbearing radiographs. All patients completed a minimum 2-year follow-up. Results: Preoperative radiographic evaluation demonstrated that ankles with posterior arthritis had a lower medial longitudinal arch, forefoot abduction, and valgus hindfoot alignment. Postoperatively, sagittal tibiotalar alignment was restored, as evidenced by an improved median LTCM from -3.3 to -0.3 mm (P < .001). The radiographic arthritis stage improved in 7 (70%) patients, whereas 3 (30%) remain unchanged in the same stage. The median score for pain (visual analog scale) decreased significantly from 8 to 2, and the median FFI improved significantly from 67.8 to 23.4 (P < .001). None of the patients underwent conversion to joint-sacrificing procedures at the latest follow-up. Conclusion: The study results suggest a possible relationship between posterior ankle arthritis and the plantarflexion of the talus, which can be seen in the setting of a flatfoot deformity. Reconstruction of the flatfoot deformity using subtalar arthrodesis restored the tibiotalar relationship in the sagittal plane and resulted in clinical improvements at an average 2.3-year follow-up in this 10-ankle case series.